xnu-1228.12.14.tar.gz

[apple/xnu.git] / bsd / kern / uipc_mbuf.c

/*
 * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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 * Please see the License for the specific language governing rights and
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 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 1982, 1986, 1988, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)uipc_mbuf.c 8.2 (Berkeley) 1/4/94
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/protosw.h>
#include <sys/domain.h>
#include <sys/queue.h>

#include <kern/kern_types.h>
#include <kern/simple_lock.h>
#include <kern/queue.h>
#include <kern/sched_prim.h>
#include <kern/cpu_number.h>

#include <libkern/OSAtomic.h>
#include <libkern/libkern.h>

#include <IOKit/IOMapper.h>

#include <machine/limits.h>
#include <machine/machine_routines.h>

#if CONFIG_MACF_NET
#include <security/mac_framework.h>
#endif /* MAC_NET */

#include <sys/mcache.h>

/*
 * MBUF IMPLEMENTATION NOTES.
 *
 * There is a total of 5 per-CPU caches:
 *
 * MC_MBUF:
 *      This is a cache of rudimentary objects of MSIZE in size; each
 *      object represents an mbuf structure.  This cache preserves only
 *      the m_type field of the mbuf during its transactions.
 *
 * MC_CL:
 *      This is a cache of rudimentary objects of MCLBYTES in size; each
 *      object represents a mcluster structure.  This cache does not
 *      preserve the contents of the objects during its transactions.
 *
 * MC_BIGCL:
 *      This is a cache of rudimentary objects of NBPG in size; each
 *      object represents a mbigcluster structure.  This cache does not
 *      preserve the contents of the objects during its transaction.
 *
 * MC_MBUF_CL:
 *      This is a cache of mbufs each having a cluster attached to it.
 *      It is backed by MC_MBUF and MC_CL rudimentary caches.  Several
 *      fields of the mbuf related to the external cluster are preserved
 *      during transactions.
 *
 * MC_MBUF_BIGCL:
 *      This is a cache of mbufs each having a big cluster attached to it.
 *      It is backed by MC_MBUF and MC_BIGCL rudimentary caches.  Several
 *      fields of the mbuf related to the external cluster are preserved
 *      during transactions.
 *
 * OBJECT ALLOCATION:
 *
 * Allocation requests are handled first at the per-CPU (mcache) layer
 * before falling back to the slab layer.  Performance is optimal when
 * the request is satisfied at the CPU layer because global data/lock
 * never gets accessed.  When the slab layer is entered for allocation,
 * the slab freelist will be checked first for available objects before
 * the VM backing store is invoked.  Slab layer operations are serialized
 * for all of the caches as the mbuf global lock is held most of the time.
 * Allocation paths are different depending on the class of objects:
 *
 * a. Rudimentary object:
 *
 *      { m_get_common(), m_clattach(), m_mclget(),
 *        m_mclalloc(), m_bigalloc(), m_copym_with_hdrs(),
 *        composite object allocation }
 *                      |       ^
 *                      |       |
 *                      |       +-----------------------+
 *                      v                               |
 *         mcache_alloc/mcache_alloc_ext()      mbuf_slab_audit()
 *                      |                               ^
 *                      v                               |
 *                 [CPU cache] -------> (found?) -------+
 *                      |                               |
 *                      v                               |
 *               mbuf_slab_alloc()                      |
 *                      |                               |
 *                      v                               |
 *      +---------> [freelist] -------> (found?) -------+
 *      |               |
 *      |               v
 *      |           m_clalloc()
 *      |               |
 *      |               v
 *      +---<<---- kmem_mb_alloc()
 *
 * b. Composite object:
 *
 *      { m_getpackets_internal(), m_allocpacket_internal() }
 *                      |       ^
 *                      |       |
 *                      |       +------ (done) ---------+
 *                      v                               |
 *         mcache_alloc/mcache_alloc_ext()      mbuf_cslab_audit()
 *                      |                               ^
 *                      v                               |
 *                 [CPU cache] -------> (found?) -------+
 *                      |                               |
 *                      v                               |
 *               mbuf_cslab_alloc()                     |
 *                      |                               |
 *                      v                               |
 *                  [freelist] -------> (found?) -------+
 *                      |                               |
 *                      v                               |
 *              (rudimentary object)                    |
 *         mcache_alloc/mcache_alloc_ext() ------>>-----+
 *
 * Auditing notes: If auditing is enabled, buffers will be subjected to
 * integrity checks by the audit routine.  This is done by verifying their
 * contents against DEADBEEF (free) pattern before returning them to caller.
 * As part of this step, the routine will also record the transaction and
 * pattern-fill the buffers with BADDCAFE (uninitialized) pattern.  It will
 * also restore any constructed data structure fields if necessary.
 *
 * OBJECT DEALLOCATION:
 *
 * Freeing an object simply involves placing it into the CPU cache; this
 * pollutes the cache to benefit subsequent allocations.  The slab layer
 * will only be entered if the object is to be purged out of the cache.
 * During normal operations, this happens only when the CPU layer resizes
 * its bucket while it's adjusting to the allocation load.  Deallocation
 * paths are different depending on the class of objects:
 *
 * a. Rudimentary object:
 *
 *      { m_free(), m_freem_list(), composite object deallocation }
 *                      |       ^
 *                      |       |
 *                      |       +------ (done) ---------+
 *                      v                               |
 *         mcache_free/mcache_free_ext()                |
 *                      |                               |
 *                      v                               |
 *              mbuf_slab_audit()                       |
 *                      |                               |
 *                      v                               |
 *                 [CPU cache] ---> (not purging?) -----+
 *                      |                               |
 *                      v                               |
 *               mbuf_slab_free()                       |
 *                      |                               |
 *                      v                               |
 *                  [freelist] ----------->>------------+
 *       (objects never get purged to VM)
 *
 * b. Composite object:
 *
 *      { m_free(), m_freem_list() }
 *                      |       ^
 *                      |       |
 *                      |       +------ (done) ---------+
 *                      v                               |
 *         mcache_free/mcache_free_ext()                |
 *                      |                               |
 *                      v                               |
 *              mbuf_cslab_audit()                      |
 *                      |                               |
 *                      v                               |
 *                 [CPU cache] ---> (not purging?) -----+
 *                      |                               |
 *                      v                               |
 *               mbuf_cslab_free()                      |
 *                      |                               |
 *                      v                               |
 *                  [freelist] ---> (not purging?) -----+
 *                      |                               |
 *                      v                               |
 *              (rudimentary object)                    |
 *         mcache_free/mcache_free_ext() ------->>------+
 *
 * Auditing notes: If auditing is enabled, the audit routine will save
 * any constructed data structure fields (if necessary) before filling the
 * contents of the buffers with DEADBEEF (free) pattern and recording the
 * transaction.  Buffers that are freed (whether at CPU or slab layer) are
 * expected to contain the free pattern.
 *
 * DEBUGGING:
 *
 * Debugging can be enabled by adding "mbuf_debug=0x3" to boot-args; this
 * translates to the mcache flags (MCF_VERIFY | MCF_AUDIT).  Additionally,
 * the CPU layer cache can be disabled by setting the MCF_NOCPUCACHE flag,
 * i.e. modify the boot argument parameter to "mbuf_debug=0x13".  Note
 * that debugging consumes more CPU and memory.
 *
 * Each object is associated with exactly one mcache_audit_t structure that
 * contains the information related to its last buffer transaction.  Given
 * an address of an object, the audit structure can be retrieved by finding
 * the position of the object relevant to the base address of the cluster:
 *
 *      +------------+                  +=============+
 *      | mbuf addr  |                  | mclaudit[i] |
 *      +------------+                  +=============+
 *            |                         | cl_audit[0] |
 *      i = MTOCL(addr)                 +-------------+
 *            |                 +-----> | cl_audit[1] | -----> mcache_audit_t
 *      b = CLTOM(i)            |       +-------------+
 *            |                 |       |     ...     |
 *      x = MCLIDX(b, addr)     |       +-------------+
 *            |                 |       | cl_audit[7] |
 *            +-----------------+       +-------------+
 *               (e.g. x == 1)
 *
 * The mclaudit[] array is allocated at initialization time, but its contents
 * get populated when the corresponding cluster is created.  Because a cluster
 * can be turned into NMBPCL number of mbufs, we preserve enough space for the
 * mbufs so that there is a 1-to-1 mapping between them.  A cluster that never
 * gets (or has not yet) turned into mbufs will use only cl_audit[0] with the
 * remaining entries unused.  For big clusters, only one entry is allocated
 * and used for the entire cluster pair.
 */

/* TODO: should be in header file */
/* kernel translater */
extern vm_offset_t kmem_mb_alloc(vm_map_t, int);
extern ppnum_t pmap_find_phys(pmap_t pmap, addr64_t va);
extern vm_map_t mb_map;         /* special map */

/* Global lock */
static lck_mtx_t *mbuf_mlock;
static lck_attr_t *mbuf_mlock_attr;
static lck_grp_t *mbuf_mlock_grp;
static lck_grp_attr_t *mbuf_mlock_grp_attr;

/* Back-end (common) layer */
static void *mbuf_worker_run;   /* wait channel for worker thread */
static int mbuf_worker_ready;   /* worker thread is runnable */
static int mbuf_expand_mcl;     /* number of cluster creation requets */
static int mbuf_expand_big;     /* number of big cluster creation requests */
static int mbuf_expand_16k;     /* number of 16K cluster creation requests */
static int ncpu;                /* number of CPUs */
static int *mcl_paddr;          /* Array of cluster physical addresses */
static ppnum_t mcl_paddr_base;  /* Handle returned by IOMapper::iovmAlloc() */
static mcache_t *ref_cache;     /* Cache of cluster reference & flags */
static mcache_t *mcl_audit_con_cache; /* Audit contents cache */
static unsigned int mbuf_debug; /* patchable mbuf mcache flags */
static unsigned int mb_normalized; /* number of packets "normalized" */

typedef enum {
        MC_MBUF = 0,    /* Regular mbuf */
        MC_CL,          /* Cluster */
        MC_BIGCL,       /* Large (4K) cluster */
        MC_16KCL,       /* Jumbo (16K) cluster */
        MC_MBUF_CL,     /* mbuf + cluster */
        MC_MBUF_BIGCL,  /* mbuf + large (4K) cluster */
        MC_MBUF_16KCL   /* mbuf + jumbo (16K) cluster */
} mbuf_class_t;

#define MBUF_CLASS_MIN          MC_MBUF
#define MBUF_CLASS_MAX          MC_MBUF_16KCL
#define MBUF_CLASS_LAST         MC_16KCL
#define MBUF_CLASS_VALID(c) \
        ((int)(c) >= MBUF_CLASS_MIN && (int)(c) <= MBUF_CLASS_MAX)
#define MBUF_CLASS_COMPOSITE(c) \
        ((int)(c) > MBUF_CLASS_LAST)


/*
 * mbuf specific mcache allocation request flags.
 */
#define MCR_COMP        MCR_USR1 /* for MC_MBUF_{CL,BIGCL,16KCL} caches */

/*
 * Per-cluster slab structure.
 *
 * A slab is a cluster control structure that contains one or more object
 * chunks; the available chunks are chained in the slab's freelist (sl_head).
 * Each time a chunk is taken out of the slab, the slab's reference count
 * gets incremented.  When all chunks have been taken out, the empty slab
 * gets removed (SLF_DETACHED) from the class's slab list.  A chunk that is
 * returned to a slab causes the slab's reference count to be decremented;
 * it also causes the slab to be reinserted back to class's slab list, if
 * it's not already done.
 *
 * Compartmentalizing of the object chunks into slabs allows us to easily
 * merge one or more slabs together when the adjacent slabs are idle, as
 * well as to convert or move a slab from one class to another; e.g. the
 * mbuf cluster slab can be converted to a regular cluster slab when all
 * mbufs in the slab have been freed.
 *
 * A slab may also span across multiple clusters for chunks larger than
 * a cluster's size.  In this case, only the slab of the first cluster is
 * used.  The rest of the slabs are marked with SLF_PARTIAL to indicate
 * that they are part of the larger slab.
 */
typedef struct mcl_slab {
        struct mcl_slab *sl_next;       /* neighboring slab */
        u_int8_t        sl_class;       /* controlling mbuf class */
        int8_t          sl_refcnt;      /* outstanding allocations */
        int8_t          sl_chunks;      /* chunks (bufs) in this slab */
        u_int16_t       sl_flags;       /* slab flags (see below) */
        u_int16_t       sl_len;         /* slab length */
        void            *sl_base;       /* base of allocated memory */
        void            *sl_head;       /* first free buffer */
        TAILQ_ENTRY(mcl_slab) sl_link;  /* next/prev slab on freelist */
} mcl_slab_t;

#define SLF_MAPPED      0x0001          /* backed by a mapped page */
#define SLF_PARTIAL     0x0002          /* part of another slab */
#define SLF_DETACHED    0x0004          /* not in slab freelist */

/*
 * The array of slabs are broken into groups of arrays per 1MB of kernel
 * memory to reduce the footprint.  Each group is allocated on demand
 * whenever a new piece of memory mapped in from the VM crosses the 1MB
 * boundary.
 */
#define NSLABSPMB       ((1 << MBSHIFT) >> MCLSHIFT)    /* 512 slabs/grp */

typedef struct mcl_slabg {
        mcl_slab_t      slg_slab[NSLABSPMB];    /* group of slabs */
} mcl_slabg_t;

/*
 * Per-cluster audit structure.
 */
typedef struct {
        mcache_audit_t  *cl_audit[NMBPCL];      /* array of audits */
} mcl_audit_t;

#if CONFIG_MBUF_NOEXPAND
static unsigned int maxmbufcl;
#endif /* CONFIG_MBUF_NOEXPAND */

/*
 * Size of data from the beginning of an mbuf that covers m_hdr, pkthdr
 * and m_ext structures.  If auditing is enabled, we allocate a shadow
 * mbuf structure of this size inside each audit structure, and the
 * contents of the real mbuf gets copied into it when the mbuf is freed.
 * This allows us to pattern-fill the mbuf for integrity check, and to
 * preserve any constructed mbuf fields (e.g. mbuf + cluster cache case).
 * Note that we don't save the contents of clusters when they are freed;
 * we simply pattern-fill them.
 */
#if defined(__LP64__)
#define AUDIT_CONTENTS_SIZE     160
#else
#define AUDIT_CONTENTS_SIZE     80
#endif /* __LP64__ */

/*
 * mbuf specific mcache audit flags
 */
#define MB_INUSE        0x01    /* object has not been returned to slab */
#define MB_COMP_INUSE   0x02    /* object has not been returned to cslab */
#define MB_SCVALID      0x04    /* object has valid saved contents */

/*
 * Each of the following two arrays hold up to nmbclusters elements.
 */
static mcl_audit_t *mclaudit;   /* array of cluster audit information */
static mcl_slabg_t **slabstbl;  /* cluster slabs table */
static unsigned int maxslabgrp; /* max # of entries in slabs table */
static unsigned int slabgrp;    /* # of entries in slabs table */

/* Globals */
int nclusters;                  /* # of clusters for non-jumbo (legacy) sizes */
int njcl;                       /* # of clusters for jumbo sizes */
int njclbytes;                  /* size of a jumbo cluster */
union mcluster *mbutl;          /* first mapped cluster address */
union mcluster *embutl;         /* ending virtual address of mclusters */
int max_linkhdr;                /* largest link-level header */
int max_protohdr;               /* largest protocol header */
int max_hdr;                    /* largest link+protocol header */
int max_datalen;                /* MHLEN - max_hdr */

/* TODO: should be in header file */
int do_reclaim = 0;

/* The minimum number of objects that are allocated, to start. */
#define MINCL           32
#define MINBIGCL        (MINCL >> 1)
#define MIN16KCL        (MINCL >> 2)

/* Low watermarks (only map in pages once free counts go below) */
#define MCL_LOWAT       MINCL
#define MBIGCL_LOWAT    MINBIGCL
#define M16KCL_LOWAT    MIN16KCL

typedef struct {
        mbuf_class_t    mtbl_class;     /* class type */
        mcache_t        *mtbl_cache;    /* mcache for this buffer class */
        TAILQ_HEAD(mcl_slhead, mcl_slab) mtbl_slablist; /* slab list */
        mcache_obj_t    *mtbl_cobjlist; /* composite objects freelist */
        mb_class_stat_t *mtbl_stats;    /* statistics fetchable via sysctl */
        u_int32_t       mtbl_maxsize;   /* maximum buffer size */
        int             mtbl_minlimit;  /* minimum allowed */
        int             mtbl_maxlimit;  /* maximum allowed */
        u_int32_t       mtbl_wantpurge; /* purge during next reclaim */
} mbuf_table_t;

#define m_class(c)      mbuf_table[c].mtbl_class
#define m_cache(c)      mbuf_table[c].mtbl_cache
#define m_slablist(c)   mbuf_table[c].mtbl_slablist
#define m_cobjlist(c)   mbuf_table[c].mtbl_cobjlist
#define m_maxsize(c)    mbuf_table[c].mtbl_maxsize
#define m_minlimit(c)   mbuf_table[c].mtbl_minlimit
#define m_maxlimit(c)   mbuf_table[c].mtbl_maxlimit
#define m_wantpurge(c)  mbuf_table[c].mtbl_wantpurge
#define m_cname(c)      mbuf_table[c].mtbl_stats->mbcl_cname
#define m_size(c)       mbuf_table[c].mtbl_stats->mbcl_size
#define m_total(c)      mbuf_table[c].mtbl_stats->mbcl_total
#define m_active(c)     mbuf_table[c].mtbl_stats->mbcl_active
#define m_infree(c)     mbuf_table[c].mtbl_stats->mbcl_infree
#define m_slab_cnt(c)   mbuf_table[c].mtbl_stats->mbcl_slab_cnt
#define m_alloc_cnt(c)  mbuf_table[c].mtbl_stats->mbcl_alloc_cnt
#define m_free_cnt(c)   mbuf_table[c].mtbl_stats->mbcl_free_cnt
#define m_notified(c)   mbuf_table[c].mtbl_stats->mbcl_notified
#define m_purge_cnt(c)  mbuf_table[c].mtbl_stats->mbcl_purge_cnt
#define m_fail_cnt(c)   mbuf_table[c].mtbl_stats->mbcl_fail_cnt
#define m_ctotal(c)     mbuf_table[c].mtbl_stats->mbcl_ctotal

static mbuf_table_t mbuf_table[] = {
        /*
         * The caches for mbufs, regular clusters and big clusters.
         */
        { MC_MBUF, NULL, TAILQ_HEAD_INITIALIZER(m_slablist(MC_MBUF)),
            NULL, NULL, 0, 0, 0, 0 },
        { MC_CL, NULL, TAILQ_HEAD_INITIALIZER(m_slablist(MC_CL)),
            NULL, NULL, 0, 0, 0, 0 },
        { MC_BIGCL, NULL, TAILQ_HEAD_INITIALIZER(m_slablist(MC_BIGCL)),
            NULL, NULL, 0, 0, 0, 0 },
        { MC_16KCL, NULL, TAILQ_HEAD_INITIALIZER(m_slablist(MC_16KCL)),
            NULL, NULL, 0, 0, 0, 0 },
        /*
         * The following are special caches; they serve as intermediate
         * caches backed by the above rudimentary caches.  Each object
         * in the cache is an mbuf with a cluster attached to it.  Unlike
         * the above caches, these intermediate caches do not directly
         * deal with the slab structures; instead, the constructed
         * cached elements are simply stored in the freelists.
         */
        { MC_MBUF_CL, NULL, { NULL, NULL }, NULL, NULL, 0, 0, 0, 0 },
        { MC_MBUF_BIGCL, NULL, { NULL, NULL }, NULL, NULL, 0, 0, 0, 0 },
        { MC_MBUF_16KCL, NULL, { NULL, NULL }, NULL, NULL, 0, 0, 0, 0 },
};

#define NELEM(a)        (sizeof (a) / sizeof ((a)[0]))

static void *mb_waitchan = &mbuf_table; /* wait channel for all caches */
static int mb_waiters;                  /* number of sleepers */

/* The following are used to serialize m_clalloc() */
static boolean_t mb_clalloc_busy;
static void *mb_clalloc_waitchan = &mb_clalloc_busy;
static int mb_clalloc_waiters;

static int mbstat_sysctl SYSCTL_HANDLER_ARGS;
static int mb_stat_sysctl SYSCTL_HANDLER_ARGS;
static void mbuf_table_init(void);
static inline void m_incref(struct mbuf *);
static inline u_int32_t m_decref(struct mbuf *);
static int m_clalloc(const u_int32_t, const int, const u_int32_t);
static void mbuf_worker_thread_init(void);
static mcache_obj_t *slab_alloc(mbuf_class_t, int);
static void slab_free(mbuf_class_t, mcache_obj_t *);
static unsigned int mbuf_slab_alloc(void *, mcache_obj_t ***,
    unsigned int, int);
static void mbuf_slab_free(void *, mcache_obj_t *, int);
static void mbuf_slab_audit(void *, mcache_obj_t *, boolean_t);
static void mbuf_slab_notify(void *, u_int32_t);
static unsigned int cslab_alloc(mbuf_class_t, mcache_obj_t ***,
    unsigned int);
static unsigned int cslab_free(mbuf_class_t, mcache_obj_t *, int);
static unsigned int mbuf_cslab_alloc(void *, mcache_obj_t ***,
    unsigned int, int);
static void mbuf_cslab_free(void *, mcache_obj_t *, int);
static void mbuf_cslab_audit(void *, mcache_obj_t *, boolean_t);
static int freelist_populate(mbuf_class_t, unsigned int, int);
static boolean_t mbuf_cached_above(mbuf_class_t, int);
static boolean_t mbuf_steal(mbuf_class_t, unsigned int);
static void m_reclaim(mbuf_class_t, unsigned int, boolean_t);
static int m_howmany(int, size_t);
static void mbuf_worker_thread(void);
static boolean_t mbuf_sleep(mbuf_class_t, unsigned int, int);

static void mcl_audit_init(void *, mcache_audit_t **, mcache_obj_t **,
    size_t, unsigned int);
static mcache_audit_t *mcl_audit_buf2mca(mbuf_class_t, mcache_obj_t *);
static void mcl_audit_mbuf(mcache_audit_t *, void *, boolean_t, boolean_t);
static void mcl_audit_cluster(mcache_audit_t *, void *, size_t, boolean_t,
    boolean_t);
static void mcl_audit_restore_mbuf(struct mbuf *, mcache_audit_t *, boolean_t);
static void mcl_audit_save_mbuf(struct mbuf *, mcache_audit_t *);
static void mcl_audit_mcheck_panic(struct mbuf *);
static void mcl_audit_verify_nextptr(void *, mcache_audit_t *);

static mcl_slab_t *slab_get(void *);
static void slab_init(mcl_slab_t *, mbuf_class_t, u_int32_t,
    void *, void *, unsigned int, int, int);
static void slab_insert(mcl_slab_t *, mbuf_class_t);
static void slab_remove(mcl_slab_t *, mbuf_class_t);
static boolean_t slab_inrange(mcl_slab_t *, void *);
static void slab_nextptr_panic(mcl_slab_t *, void *);
static void slab_detach(mcl_slab_t *);
static boolean_t slab_is_detached(mcl_slab_t *);

/*
 * This flag is set for all mbufs that come out of and into the composite
 * mbuf + cluster caches, i.e. MC_MBUF_CL and MC_MBUF_BIGCL.  mbufs that
 * are marked with such a flag have clusters attached to them, and will be
 * treated differently when they are freed; instead of being placed back
 * into the mbuf and cluster freelists, the composite mbuf + cluster objects
 * are placed back into the appropriate composite cache's freelist, and the
 * actual freeing is deferred until the composite objects are purged.  At
 * such a time, this flag will be cleared from the mbufs and the objects
 * will be freed into their own separate freelists.
 */
#define EXTF_COMPOSITE  0x1

#define MEXT_RFA(m)             ((m)->m_ext.ext_refflags)
#define MEXT_REF(m)             (MEXT_RFA(m)->refcnt)
#define MEXT_FLAGS(m)           (MEXT_RFA(m)->flags)
#define MBUF_IS_COMPOSITE(m)    \
        (MEXT_REF(m) == 0 && (MEXT_FLAGS(m) & EXTF_COMPOSITE))

/*
 * Macros used to verify the integrity of the mbuf.
 */
#define _MCHECK(m) {                                                    \
        if ((m)->m_type != MT_FREE) {                                   \
                if (mclaudit == NULL)                                   \
                        panic("MCHECK: m_type=%d m=%p",                 \
                            (u_int16_t)(m)->m_type, m);                 \
                else                                                    \
                        mcl_audit_mcheck_panic(m);                      \
        }                                                               \
}

#define MBUF_IN_MAP(addr)                                               \
        ((void *)(addr) >= (void *)mbutl && (void *)(addr) < (void *)embutl)

#define MRANGE(addr) {                                                  \
        if (!MBUF_IN_MAP(addr))                                         \
                panic("MRANGE: address out of range 0x%p", addr);       \
}

/*
 * Macro version of mtod.
 */
#define MTOD(m, t)      ((t)((m)->m_data))

/*
 * Macros to obtain cluster index and base cluster address.
 */
#define MTOCL(x)        (((char *)(x) - (char *)mbutl) >> MCLSHIFT)
#define CLTOM(x)        ((union mcluster *)(mbutl + (x)))

/*
 * Macro to find the mbuf index relative to the cluster base.
 */
#define MCLIDX(c, m)    (((char *)(m) - (char *)(c)) >> 8)

/*
 * Macros used during mbuf and cluster initialization.
 */
#define MBUF_INIT(m, pkthdr, type) {                                    \
        _MCHECK(m);                                                     \
        (m)->m_next = (m)->m_nextpkt = NULL;                            \
        (m)->m_len = 0;                                                 \
        (m)->m_type = type;                                             \
        if ((pkthdr) == 0) {                                            \
                (m)->m_data = (m)->m_dat;                               \
                (m)->m_flags = 0;                                       \
        } else {                                                        \
                (m)->m_data = (m)->m_pktdat;                            \
                (m)->m_flags = M_PKTHDR;                                \
                (m)->m_pkthdr.rcvif = NULL;                             \
                (m)->m_pkthdr.len = 0;                                  \
                (m)->m_pkthdr.header = NULL;                            \
                (m)->m_pkthdr.csum_flags = 0;                           \
                (m)->m_pkthdr.csum_data = 0;                            \
                (m)->m_pkthdr.reserved0 = NULL;                         \
                (m)->m_pkthdr.vlan_tag = 0;                             \
                (m)->m_pkthdr.socket_id = 0;                            \
                m_tag_init(m);                                          \
        }                                                               \
}

#define MEXT_INIT(m, buf, size, free, arg, rfa, ref, flag) {            \
        (m)->m_data = (m)->m_ext.ext_buf = (buf);                       \
        (m)->m_flags |= M_EXT;                                          \
        (m)->m_ext.ext_size = (size);                                   \
        (m)->m_ext.ext_free = (free);                                   \
        (m)->m_ext.ext_arg = (arg);                                     \
        (m)->m_ext.ext_refs.forward = (m)->m_ext.ext_refs.backward =    \
            &(m)->m_ext.ext_refs;                                       \
        MEXT_RFA(m) = (rfa);                                            \
        MEXT_REF(m) = (ref);                                            \
        MEXT_FLAGS(m) = (flag);                                         \
}

#define MBUF_CL_INIT(m, buf, rfa, ref, flag)    \
        MEXT_INIT(m, buf, m_maxsize(MC_CL), NULL, NULL, rfa, ref, flag)

#define MBUF_BIGCL_INIT(m, buf, rfa, ref, flag) \
        MEXT_INIT(m, buf, m_maxsize(MC_BIGCL), m_bigfree, NULL, rfa, ref, flag)

#define MBUF_16KCL_INIT(m, buf, rfa, ref, flag) \
        MEXT_INIT(m, buf, m_maxsize(MC_16KCL), m_16kfree, NULL, rfa, ref, flag)

/*
 * Macro to convert BSD malloc sleep flag to mcache's
 */
#define MSLEEPF(f)      ((!((f) & M_DONTWAIT)) ? MCR_SLEEP : MCR_NOSLEEP)

/*
 * The structure that holds all mbuf class statistics exportable via sysctl.
 * Similar to mbstat structure, the mb_stat structure is protected by the
 * global mbuf lock.  It contains additional information about the classes
 * that allows for a more accurate view of the state of the allocator.
 */
struct mb_stat *mb_stat;

#define MB_STAT_SIZE(n) \
        ((size_t)(&((mb_stat_t *)0)->mbs_class[n]))

/*
 * The legacy structure holding all of the mbuf allocation statistics.
 * The actual statistics used by the kernel are stored in the mbuf_table
 * instead, and are updated atomically while the global mbuf lock is held.
 * They are mirrored in mbstat to support legacy applications (e.g. netstat).
 * Unlike before, the kernel no longer relies on the contents of mbstat for
 * its operations (e.g. cluster expansion) because the structure is exposed
 * to outside and could possibly be modified, therefore making it unsafe.
 * With the exception of the mbstat.m_mtypes array (see below), all of the
 * statistics are updated as they change.
 */
struct mbstat mbstat;

#define MBSTAT_MTYPES_MAX \
        (sizeof (mbstat.m_mtypes) / sizeof (mbstat.m_mtypes[0]))

/*
 * Allocation statistics related to mbuf types (up to MT_MAX-1) are updated
 * atomically and stored in a per-CPU structure which is lock-free; this is
 * done in order to avoid writing to the global mbstat data structure which
 * would cause false sharing.  During sysctl request for kern.ipc.mbstat,
 * the statistics across all CPUs will be converged into the mbstat.m_mtypes
 * array and returned to the application.  Any updates for types greater or
 * equal than MT_MAX would be done atomically to the mbstat; this slows down
 * performance but is okay since the kernel uses only up to MT_MAX-1 while
 * anything beyond that (up to type 255) is considered a corner case.
 */
typedef struct {
        unsigned int    cpu_mtypes[MT_MAX];
} __attribute__((aligned(CPU_CACHE_SIZE), packed)) mtypes_cpu_t;

typedef struct {
        mtypes_cpu_t    mbs_cpu[1];
} mbuf_mtypes_t;

static mbuf_mtypes_t *mbuf_mtypes;      /* per-CPU statistics */

#define MBUF_MTYPES_SIZE(n) \
        ((size_t)(&((mbuf_mtypes_t *)0)->mbs_cpu[n]))

#define MTYPES_CPU(p) \
        ((mtypes_cpu_t *)((char *)(p) + MBUF_MTYPES_SIZE(cpu_number())))

/* This should be in a header file */
#define atomic_add_32(a, n)     ((void) OSAddAtomic(n, (volatile SInt32 *)a))

#define mtype_stat_add(type, n) {                                       \
        if ((unsigned)(type) < MT_MAX) {                                \
                mtypes_cpu_t *mbs = MTYPES_CPU(mbuf_mtypes);            \
                atomic_add_32(&mbs->cpu_mtypes[type], n);               \
        } else if ((unsigned)(type) < MBSTAT_MTYPES_MAX) {              \
                atomic_add_32(&mbstat.m_mtypes[type], n);               \
        }                                                               \
}

#define mtype_stat_sub(t, n)    mtype_stat_add(t, -(n))
#define mtype_stat_inc(t)       mtype_stat_add(t, 1)
#define mtype_stat_dec(t)       mtype_stat_sub(t, 1)

static int
mbstat_sysctl SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
        int m, n;
        mtypes_cpu_t mtc;

        bzero(&mtc, sizeof (mtc));
        for (m = 0; m < ncpu; m++) {
                mtypes_cpu_t *scp = &mbuf_mtypes->mbs_cpu[m];
                mtypes_cpu_t temp;

                bcopy(&scp->cpu_mtypes, &temp.cpu_mtypes,
                    sizeof (temp.cpu_mtypes));

                for (n = 0; n < MT_MAX; n++)
                        mtc.cpu_mtypes[n] += temp.cpu_mtypes[n];
        }
        lck_mtx_lock(mbuf_mlock);
        for (n = 0; n < MT_MAX; n++)
                mbstat.m_mtypes[n] = mtc.cpu_mtypes[n];
        lck_mtx_unlock(mbuf_mlock);

        return (SYSCTL_OUT(req, &mbstat, sizeof (mbstat)));
}

static int
mb_stat_sysctl SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
        mcache_t *cp;
        mcache_cpu_t *ccp;
        mb_class_stat_t *sp;
        int k, m, bktsize;

        lck_mtx_lock(mbuf_mlock);
        for (k = 0; k < NELEM(mbuf_table); k++) {
                cp = m_cache(k);
                ccp = &cp->mc_cpu[0];
                bktsize = ccp->cc_bktsize;
                sp = mbuf_table[k].mtbl_stats;

                if (cp->mc_flags & MCF_NOCPUCACHE)
                        sp->mbcl_mc_state = MCS_DISABLED;
                else if (cp->mc_purge_cnt > 0)
                        sp->mbcl_mc_state = MCS_PURGING;
                else if (bktsize == 0)
                        sp->mbcl_mc_state = MCS_OFFLINE;
                else
                        sp->mbcl_mc_state = MCS_ONLINE;

                sp->mbcl_mc_cached = 0;
                for (m = 0; m < ncpu; m++) {
                        ccp = &cp->mc_cpu[m];
                        if (ccp->cc_objs > 0)
                                sp->mbcl_mc_cached += ccp->cc_objs;
                        if (ccp->cc_pobjs > 0)
                                sp->mbcl_mc_cached += ccp->cc_pobjs;
                }
                sp->mbcl_mc_cached += (cp->mc_full.bl_total * bktsize);
                sp->mbcl_active = sp->mbcl_total - sp->mbcl_mc_cached -
                    sp->mbcl_infree;

                sp->mbcl_mc_waiter_cnt = cp->mc_waiter_cnt;
                sp->mbcl_mc_wretry_cnt = cp->mc_wretry_cnt;
                sp->mbcl_mc_nwretry_cnt = cp->mc_nwretry_cnt;

                /* Calculate total count specific to each class */
                sp->mbcl_ctotal = sp->mbcl_total;
                switch (m_class(k)) {
                case MC_MBUF:
                        /* Deduct mbufs used in composite caches */
                        sp->mbcl_ctotal -= (m_total(MC_MBUF_CL) +
                            m_total(MC_MBUF_BIGCL));
                        break;

                case MC_CL:
                        /* Deduct clusters used in composite cache and mbufs */
                        sp->mbcl_ctotal -= (m_total(MC_MBUF_CL) +
                            (P2ROUNDUP(m_total(MC_MBUF), NMBPCL)/NMBPCL));
                        break;

                case MC_BIGCL:
                        /* Deduct clusters used in composite cache */
                        sp->mbcl_ctotal -= m_total(MC_MBUF_BIGCL);
                        break;

                case MC_16KCL:
                        /* Deduct clusters used in composite cache */
                        sp->mbcl_ctotal -= m_total(MC_MBUF_16KCL);
                        break;

                default:
                        break;
                }
        }
        lck_mtx_unlock(mbuf_mlock);

        return (SYSCTL_OUT(req, mb_stat, MB_STAT_SIZE(NELEM(mbuf_table))));
}

static inline void
m_incref(struct mbuf *m)
{
        UInt32 old, new;
        volatile UInt32 *addr = (volatile UInt32 *)&MEXT_REF(m);

        do {
                old = *addr;
                new = old + 1;
                ASSERT(new != 0);
        } while (!OSCompareAndSwap(old, new, addr));
}

static inline u_int32_t
m_decref(struct mbuf *m)
{
        UInt32 old, new;
        volatile UInt32 *addr = (volatile UInt32 *)&MEXT_REF(m);

        do {
                old = *addr;
                new = old - 1;
                ASSERT(old != 0);
        } while (!OSCompareAndSwap(old, new, addr));

        return (new);
}

static void
mbuf_table_init(void)
{
        int m;

        MALLOC(mb_stat, mb_stat_t *, MB_STAT_SIZE(NELEM(mbuf_table)),
            M_TEMP, M_WAITOK | M_ZERO);
        VERIFY(mb_stat != NULL);

        mb_stat->mbs_cnt = NELEM(mbuf_table);
        for (m = 0; m < NELEM(mbuf_table); m++)
                mbuf_table[m].mtbl_stats = &mb_stat->mbs_class[m];

#if CONFIG_MBUF_JUMBO
        /*
         * Set aside 1/3 of the mbuf cluster map for jumbo clusters; we do
         * this only on platforms where jumbo cluster pool is enabled.
         */
        njcl = nmbclusters / 3;
        njclbytes = M16KCLBYTES;
#endif /* CONFIG_MBUF_JUMBO */

        /*
         * nclusters is going to be split in 2 to hold both the 2K
         * and the 4K pools, so make sure each half is even.
         */
        nclusters = P2ROUNDDOWN(nmbclusters - njcl, 4);
        if (njcl > 0) {
                /*
                 * Each jumbo cluster takes 8 2K clusters, so make
                 * sure that the pool size is evenly divisible by 8.
                 */
                njcl = P2ROUNDDOWN(nmbclusters - nclusters, 8);
        }

#if CONFIG_MBUF_NOEXPAND
        /* Only use 4k clusters if we're setting aside more than 256k */
        if (nmbclusters <= 128) {
                maxmbufcl = nmbclusters / 4;
        } else {
                /* Half to big clusters, half to small */
                maxmbufcl = (nmbclusters / 4) * 3;
        }
#endif /* CONFIG_MBUF_NOEXPAND */

        /*
         * 1/2 of the map is reserved for 2K clusters.  Out of this, 1/16th
         * of the total number of 2K clusters allocated is reserved and cannot
         * be turned into mbufs.  It can only be used for pure cluster objects.
         */
        m_minlimit(MC_CL) = (nclusters >> 5);
        m_maxlimit(MC_CL) = (nclusters >> 1);
        m_maxsize(MC_CL) = m_size(MC_CL) = MCLBYTES;
        (void) snprintf(m_cname(MC_CL), MAX_MBUF_CNAME, "cl");

        /*
         * The remaining (15/16th) can be turned into mbufs.
         */
        m_minlimit(MC_MBUF) = 0;
        m_maxlimit(MC_MBUF) = (m_maxlimit(MC_CL) - m_minlimit(MC_CL)) * NMBPCL;
        m_maxsize(MC_MBUF) = m_size(MC_MBUF) = MSIZE;
        (void) snprintf(m_cname(MC_MBUF), MAX_MBUF_CNAME, "mbuf");

        /*
         * The other 1/2 of the map is reserved for 4K clusters.
         */
        m_minlimit(MC_BIGCL) = 0;
        m_maxlimit(MC_BIGCL) = m_maxlimit(MC_CL) >> 1;
        m_maxsize(MC_BIGCL) = m_size(MC_BIGCL) = NBPG;
        (void) snprintf(m_cname(MC_BIGCL), MAX_MBUF_CNAME, "bigcl");

        /*
         * Set limits for the composite classes.
         */
        m_minlimit(MC_MBUF_CL) = 0;
        m_maxlimit(MC_MBUF_CL) = m_maxlimit(MC_CL) - m_minlimit(MC_CL);
        m_maxsize(MC_MBUF_CL) = MCLBYTES;
        m_size(MC_MBUF_CL) = m_size(MC_MBUF) + m_size(MC_CL);
        (void) snprintf(m_cname(MC_MBUF_CL), MAX_MBUF_CNAME, "mbuf_cl");

        m_minlimit(MC_MBUF_BIGCL) = 0;
        m_maxlimit(MC_MBUF_BIGCL) = m_maxlimit(MC_BIGCL);
        m_maxsize(MC_MBUF_BIGCL) = NBPG;
        m_size(MC_MBUF_BIGCL) = m_size(MC_MBUF) + m_size(MC_BIGCL);
        (void) snprintf(m_cname(MC_MBUF_BIGCL), MAX_MBUF_CNAME, "mbuf_bigcl");

        /*
         * And for jumbo classes.
         */
        m_minlimit(MC_16KCL) = 0;
        m_maxlimit(MC_16KCL) = (njcl >> 3);
        m_maxsize(MC_16KCL) = m_size(MC_16KCL) = M16KCLBYTES;
        (void) snprintf(m_cname(MC_16KCL), MAX_MBUF_CNAME, "16kcl");

        m_minlimit(MC_MBUF_16KCL) = 0;
        m_maxlimit(MC_MBUF_16KCL) = m_maxlimit(MC_16KCL);
        m_maxsize(MC_MBUF_16KCL) = M16KCLBYTES;
        m_size(MC_MBUF_16KCL) = m_size(MC_MBUF) + m_size(MC_16KCL);
        (void) snprintf(m_cname(MC_MBUF_16KCL), MAX_MBUF_CNAME, "mbuf_16kcl");

        /*
         * Initialize the legacy mbstat structure.
         */
        bzero(&mbstat, sizeof (mbstat));
        mbstat.m_msize = m_maxsize(MC_MBUF);
        mbstat.m_mclbytes = m_maxsize(MC_CL);
        mbstat.m_minclsize = MINCLSIZE;
        mbstat.m_mlen = MLEN;
        mbstat.m_mhlen = MHLEN;
        mbstat.m_bigmclbytes = m_maxsize(MC_BIGCL);
}

__private_extern__ void
mbinit(void)
{
        unsigned int m;
        int initmcl = MINCL;
        int mcl_pages;
        void *buf;

        if (nmbclusters == 0)
                nmbclusters = NMBCLUSTERS;

        /* Setup the mbuf table */
        mbuf_table_init();

        /* Global lock for common layer */
        mbuf_mlock_grp_attr = lck_grp_attr_alloc_init();
        mbuf_mlock_grp = lck_grp_alloc_init("mbuf", mbuf_mlock_grp_attr);
        mbuf_mlock_attr = lck_attr_alloc_init();
        mbuf_mlock = lck_mtx_alloc_init(mbuf_mlock_grp, mbuf_mlock_attr);

        /* Allocate cluster slabs table */
        maxslabgrp = P2ROUNDUP(nmbclusters, NSLABSPMB) / NSLABSPMB;
        MALLOC(slabstbl, mcl_slabg_t **, maxslabgrp * sizeof (mcl_slabg_t *),
            M_TEMP, M_WAITOK | M_ZERO);
        VERIFY(slabstbl != NULL);

        /* Allocate audit structures if needed */
        PE_parse_boot_argn("mbuf_debug", &mbuf_debug, sizeof (mbuf_debug));
        mbuf_debug |= mcache_getflags();
        if (mbuf_debug & MCF_AUDIT) {
                MALLOC(mclaudit, mcl_audit_t *,
                    nmbclusters * sizeof (*mclaudit), M_TEMP,
                    M_WAITOK | M_ZERO);
                VERIFY(mclaudit != NULL);

                mcl_audit_con_cache = mcache_create("mcl_audit_contents",
                    AUDIT_CONTENTS_SIZE, 0, 0, MCR_SLEEP);
                VERIFY(mcl_audit_con_cache != NULL);
        }

        /* Calculate the number of pages assigned to the cluster pool */
        mcl_pages = nmbclusters/(NBPG/CLBYTES);
        MALLOC(mcl_paddr, int *, mcl_pages * sizeof (int), M_TEMP, M_WAITOK);
        VERIFY(mcl_paddr != NULL);

        /* Register with the I/O Bus mapper */
        mcl_paddr_base = IOMapperIOVMAlloc(mcl_pages);
        bzero((char *)mcl_paddr, mcl_pages * sizeof (int));

        embutl = (union mcluster *)
            ((unsigned char *)mbutl + (nmbclusters * MCLBYTES));

        PE_parse_boot_argn("initmcl", &initmcl, sizeof (initmcl));

        lck_mtx_lock(mbuf_mlock);

        if (m_clalloc(MAX(NBPG/CLBYTES, 1) * initmcl, M_WAIT, MCLBYTES) == 0)
                panic("mbinit: m_clalloc failed\n");

        lck_mtx_unlock(mbuf_mlock);

        (void) kernel_thread(kernel_task, mbuf_worker_thread_init);

        ref_cache = mcache_create("mext_ref", sizeof (struct ext_ref),
            0, 0, MCR_SLEEP);

        /* Create the cache for each class */
        for (m = 0; m < NELEM(mbuf_table); m++) {
                void *allocfunc, *freefunc, *auditfunc;
                u_int32_t flags;

                flags = mbuf_debug;
                if (m_class(m) == MC_MBUF_CL || m_class(m) == MC_MBUF_BIGCL ||
                    m_class(m) == MC_MBUF_16KCL) {
                        allocfunc = mbuf_cslab_alloc;
                        freefunc = mbuf_cslab_free;
                        auditfunc = mbuf_cslab_audit;
                } else {
                        allocfunc = mbuf_slab_alloc;
                        freefunc = mbuf_slab_free;
                        auditfunc = mbuf_slab_audit;
                }

                /*
                 * Disable per-CPU caches for jumbo classes if there
                 * is no jumbo cluster pool available in the system.
                 * The cache itself is still created (but will never
                 * be populated) since it simplifies the code.
                 */
                if ((m_class(m) == MC_MBUF_16KCL || m_class(m) == MC_16KCL) &&
                    njcl == 0)
                        flags |= MCF_NOCPUCACHE;

                m_cache(m) = mcache_create_ext(m_cname(m), m_maxsize(m),
                    allocfunc, freefunc, auditfunc, mbuf_slab_notify,
                    (void *)m, flags, MCR_SLEEP);
        }

        /*
         * Allocate structure for per-CPU statistics that's aligned
         * on the CPU cache boundary; this code assumes that we never
         * uninitialize this framework, since the original address
         * before alignment is not saved.
         */
        ncpu = ml_get_max_cpus();
        MALLOC(buf, void *, MBUF_MTYPES_SIZE(ncpu) + CPU_CACHE_SIZE,
            M_TEMP, M_WAITOK);
        VERIFY(buf != NULL);

        mbuf_mtypes = (mbuf_mtypes_t *)P2ROUNDUP((intptr_t)buf, CPU_CACHE_SIZE);
        bzero(mbuf_mtypes, MBUF_MTYPES_SIZE(ncpu));

        printf("mbinit: done\n");
}

/*
 * Obtain a slab of object(s) from the class's freelist.
 */
static mcache_obj_t *
slab_alloc(mbuf_class_t class, int wait)
{
        mcl_slab_t *sp;
        mcache_obj_t *buf;

        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        VERIFY(class != MC_16KCL || njcl > 0);

        /* This should always be NULL for us */
        VERIFY(m_cobjlist(class) == NULL);

        /*
         * Treat composite objects as having longer lifespan by using
         * a slab from the reverse direction, in hoping that this could
         * reduce the probability of fragmentation for slabs that hold
         * more than one buffer chunks (e.g. mbuf slabs).  For other
         * slabs, this probably doesn't make much of a difference.
         */
        if (class == MC_MBUF && (wait & MCR_COMP))
                sp = (mcl_slab_t *)TAILQ_LAST(&m_slablist(class), mcl_slhead);
        else
                sp = (mcl_slab_t *)TAILQ_FIRST(&m_slablist(class));

        if (sp == NULL) {
                VERIFY(m_infree(class) == 0 && m_slab_cnt(class) == 0);
                /* The slab list for this class is empty */
                return (NULL);
        }

        VERIFY(m_infree(class) > 0);
        VERIFY(!slab_is_detached(sp));
        VERIFY(sp->sl_class == class &&
            (sp->sl_flags & (SLF_MAPPED | SLF_PARTIAL)) == SLF_MAPPED);
        buf = sp->sl_head;
        VERIFY(slab_inrange(sp, buf) && sp == slab_get(buf));

        if (class == MC_MBUF) {
                sp->sl_head = buf->obj_next;
                VERIFY(sp->sl_head != NULL || sp->sl_refcnt == (NMBPCL - 1));
        } else {
                sp->sl_head = NULL;
        }
        if (sp->sl_head != NULL && !slab_inrange(sp, sp->sl_head)) {
                slab_nextptr_panic(sp, sp->sl_head);
                /* In case sl_head is in the map but not in the slab */
                VERIFY(slab_inrange(sp, sp->sl_head));
                /* NOTREACHED */
        }

        /* Increment slab reference */
        sp->sl_refcnt++;

        if (mclaudit != NULL) {
                mcache_audit_t *mca = mcl_audit_buf2mca(class, buf);
                mca->mca_uflags = 0;
                /* Save contents on mbuf objects only */
                if (class == MC_MBUF)
                        mca->mca_uflags |= MB_SCVALID;
        }

        if (class == MC_CL) {
                mbstat.m_clfree = (--m_infree(MC_CL)) + m_infree(MC_MBUF_CL);
                /*
                 * A 2K cluster slab can have at most 1 reference.
                 */
                VERIFY(sp->sl_refcnt == 1 && sp->sl_chunks == 1 &&
                    sp->sl_len == m_maxsize(MC_CL) && sp->sl_head == NULL);
        } else if (class == MC_BIGCL) {
                mcl_slab_t *nsp = sp->sl_next;
                mbstat.m_bigclfree = (--m_infree(MC_BIGCL)) +
                    m_infree(MC_MBUF_BIGCL);
                /*
                 * Increment 2nd slab.  A 4K big cluster takes
                 * 2 slabs, each having at most 1 reference.
                 */
                VERIFY(sp->sl_refcnt == 1 && sp->sl_chunks == 1 &&
                    sp->sl_len == m_maxsize(MC_BIGCL) && sp->sl_head == NULL);
                /* Next slab must already be present */
                VERIFY(nsp != NULL);
                nsp->sl_refcnt++;
                VERIFY(!slab_is_detached(nsp));
                VERIFY(nsp->sl_class == MC_BIGCL &&
                    nsp->sl_flags == (SLF_MAPPED | SLF_PARTIAL) &&
                    nsp->sl_refcnt == 1 && nsp->sl_chunks == 0 &&
                    nsp->sl_len == 0 && nsp->sl_base == sp->sl_base &&
                    nsp->sl_head == NULL);
        } else if (class == MC_16KCL) {
                mcl_slab_t *nsp;
                int k;

                --m_infree(MC_16KCL);
                VERIFY(sp->sl_refcnt == 1 && sp->sl_chunks == 1 &&
                    sp->sl_len == m_maxsize(MC_16KCL) && sp->sl_head == NULL);
                /*
                 * Increment 2nd-8th slab.  A 16K big cluster takes
                 * 8 cluster slabs, each having at most 1 reference.
                 */
                for (nsp = sp, k = 1; k < (M16KCLBYTES / MCLBYTES); k++) {
                        nsp = nsp->sl_next;
                        /* Next slab must already be present */
                        VERIFY(nsp != NULL);
                        nsp->sl_refcnt++;
                        VERIFY(!slab_is_detached(nsp));
                        VERIFY(nsp->sl_class == MC_16KCL &&
                            nsp->sl_flags == (SLF_MAPPED | SLF_PARTIAL) &&
                            nsp->sl_refcnt == 1 && nsp->sl_chunks == 0 &&
                            nsp->sl_len == 0 && nsp->sl_base == sp->sl_base &&
                            nsp->sl_head == NULL);
                }
        } else {
                ASSERT(class == MC_MBUF);
                --m_infree(MC_MBUF);
                /*
                 * If auditing is turned on, this check is
                 * deferred until later in mbuf_slab_audit().
                 */
                if (mclaudit == NULL)
                        _MCHECK((struct mbuf *)buf);
                /*
                 * Since we have incremented the reference count above,
                 * an mbuf slab (formerly a 2K cluster slab that was cut
                 * up into mbufs) must have a reference count between 1
                 * and NMBPCL at this point.
                 */
                VERIFY(sp->sl_refcnt >= 1 &&
                    (unsigned short)sp->sl_refcnt <= NMBPCL &&
                    sp->sl_chunks == NMBPCL && sp->sl_len == m_maxsize(MC_CL));
                VERIFY((unsigned short)sp->sl_refcnt < NMBPCL ||
                    sp->sl_head == NULL);
        }

        /* If empty, remove this slab from the class's freelist */
        if (sp->sl_head == NULL) {
                VERIFY(class != MC_MBUF || sp->sl_refcnt == NMBPCL);
                slab_remove(sp, class);
        }

        return (buf);
}

/*
 * Place a slab of object(s) back into a class's slab list.
 */
static void
slab_free(mbuf_class_t class, mcache_obj_t *buf)
{
        mcl_slab_t *sp;

        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        VERIFY(class != MC_16KCL || njcl > 0);
        VERIFY(buf->obj_next == NULL);
        sp = slab_get(buf);
        VERIFY(sp->sl_class == class && slab_inrange(sp, buf) &&
            (sp->sl_flags & (SLF_MAPPED | SLF_PARTIAL)) == SLF_MAPPED);

        /* Decrement slab reference */
        sp->sl_refcnt--;

        if (class == MC_CL || class == MC_BIGCL) {
                VERIFY(IS_P2ALIGNED(buf, MCLBYTES));
                /*
                 * A 2K cluster slab can have at most 1 reference
                 * which must be 0 at this point.
                 */
                VERIFY(sp->sl_refcnt == 0 && sp->sl_chunks == 1 &&
                    sp->sl_len == m_maxsize(class) && sp->sl_head == NULL);
                VERIFY(slab_is_detached(sp));
                if (class == MC_BIGCL) {
                        mcl_slab_t *nsp = sp->sl_next;
                        VERIFY(IS_P2ALIGNED(buf, NBPG));
                        /* Next slab must already be present */
                        VERIFY(nsp != NULL);
                        /* Decrement 2nd slab reference */
                        nsp->sl_refcnt--;
                        /*
                         * A 4K big cluster takes 2 slabs, both
                         * must now have 0 reference.
                         */
                        VERIFY(slab_is_detached(nsp));
                        VERIFY(nsp->sl_class == MC_BIGCL &&
                            (nsp->sl_flags & (SLF_MAPPED | SLF_PARTIAL)) &&
                            nsp->sl_refcnt == 0 && nsp->sl_chunks == 0 &&
                            nsp->sl_len == 0 && nsp->sl_base == sp->sl_base &&
                            nsp->sl_head == NULL);
                }
        } else if (class == MC_16KCL) {
                mcl_slab_t *nsp;
                int k;
                /*
                 * A 16K cluster takes 8 cluster slabs, all must
                 * now have 0 reference.
                 */
                VERIFY(IS_P2ALIGNED(buf, NBPG));
                VERIFY(sp->sl_refcnt == 0 && sp->sl_chunks == 1 &&
                    sp->sl_len == m_maxsize(MC_16KCL) && sp->sl_head == NULL);
                VERIFY(slab_is_detached(sp));
                for (nsp = sp, k = 1; k < (M16KCLBYTES / MCLBYTES); k++) {
                        nsp = nsp->sl_next;
                        /* Next slab must already be present */
                        VERIFY(nsp != NULL);
                        nsp->sl_refcnt--;
                        VERIFY(slab_is_detached(nsp));
                        VERIFY(nsp->sl_class == MC_16KCL &&
                            (nsp->sl_flags & (SLF_MAPPED | SLF_PARTIAL)) &&
                            nsp->sl_refcnt == 0 && nsp->sl_chunks == 0 &&
                            nsp->sl_len == 0 && nsp->sl_base == sp->sl_base &&
                            nsp->sl_head == NULL);
                }
        } else {
                /*
                 * An mbuf slab has a total of NMBPL reference counts.
                 * Since we have decremented the reference above, it
                 * must now be between 0 and NMBPCL-1.
                 */
                VERIFY(sp->sl_refcnt >= 0 &&
                    (unsigned short)sp->sl_refcnt <= (NMBPCL - 1) &&
                    sp->sl_chunks == NMBPCL && sp->sl_len == m_maxsize(MC_CL));
                VERIFY(sp->sl_refcnt < (NMBPCL - 1) ||
                    (slab_is_detached(sp) && sp->sl_head == NULL));
        }

        /*
         * When auditing is enabled, ensure that the buffer still
         * contains the free pattern.  Otherwise it got corrupted
         * while at the CPU cache layer.
         */
        if (mclaudit != NULL) {
                mcache_audit_t *mca = mcl_audit_buf2mca(class, buf);
                mcache_audit_free_verify(mca, buf, 0, m_maxsize(class));
                mca->mca_uflags &= ~MB_SCVALID;
        }

        if (class == MC_CL) {
                mbstat.m_clfree = (++m_infree(MC_CL)) + m_infree(MC_MBUF_CL);
        } else if (class == MC_BIGCL) {
                mbstat.m_bigclfree = (++m_infree(MC_BIGCL)) +
                    m_infree(MC_MBUF_BIGCL);
        } else if (class == MC_16KCL) {
                ++m_infree(MC_16KCL);
        } else {
                ++m_infree(MC_MBUF);
                buf->obj_next = sp->sl_head;
        }
        sp->sl_head = buf;

        /* All mbufs are freed; return the cluster that we stole earlier */
        if (sp->sl_refcnt == 0 && class == MC_MBUF) {
                int i = NMBPCL;

                m_total(MC_MBUF) -= NMBPCL;
                mbstat.m_mbufs = m_total(MC_MBUF);
                m_infree(MC_MBUF) -= NMBPCL;
                mtype_stat_add(MT_FREE, -NMBPCL);

                while (i--) {
                        struct mbuf *m = sp->sl_head;
                        VERIFY(m != NULL);
                        sp->sl_head = m->m_next;
                        m->m_next = NULL;
                }
                VERIFY(sp->sl_head == NULL);

                /* Remove the slab from the mbuf class's slab list */
                slab_remove(sp, class);

                /* Reinitialize it as a 2K cluster slab */
                slab_init(sp, MC_CL, sp->sl_flags, sp->sl_base, sp->sl_base,
                    sp->sl_len, 0, 1);

                if (mclaudit != NULL)
                        mcache_set_pattern(MCACHE_FREE_PATTERN,
                            (caddr_t)sp->sl_head, m_maxsize(MC_CL));

                mbstat.m_clfree = (++m_infree(MC_CL)) + m_infree(MC_MBUF_CL);

                VERIFY(slab_is_detached(sp));
                /* And finally switch class */
                class = MC_CL;
        }

        /* Reinsert the slab to the class's slab list */
        if (slab_is_detached(sp))
                slab_insert(sp, class);
}

/*
 * Common allocator for rudimentary objects called by the CPU cache layer
 * during an allocation request whenever there is no available element in the
 * bucket layer.  It returns one or more elements from the appropriate global
 * freelist.  If the freelist is empty, it will attempt to populate it and
 * retry the allocation.
 */
static unsigned int
mbuf_slab_alloc(void *arg, mcache_obj_t ***plist, unsigned int num, int wait)
{
        mbuf_class_t class = (mbuf_class_t)arg;
        unsigned int need = num;
        mcache_obj_t **list = *plist;

        ASSERT(MBUF_CLASS_VALID(class) && !MBUF_CLASS_COMPOSITE(class));
        ASSERT(need > 0);

        lck_mtx_lock(mbuf_mlock);

        for (;;) {
                if ((*list = slab_alloc(class, wait)) != NULL) {
                        (*list)->obj_next = NULL;
                        list = *plist = &(*list)->obj_next;

                        if (--need == 0) {
                                /*
                                 * If the number of elements in freelist has
                                 * dropped below low watermark, asynchronously
                                 * populate the freelist now rather than doing
                                 * it later when we run out of elements.
                                 */
                                if (!mbuf_cached_above(class, wait) &&
                                    m_infree(class) < m_total(class) >> 5) {
                                        (void) freelist_populate(class, 1,
                                            M_DONTWAIT);
                                }
                                break;
                        }
                } else {
                        VERIFY(m_infree(class) == 0 || class == MC_CL);

                        (void) freelist_populate(class, 1,
                            (wait & MCR_NOSLEEP) ? M_DONTWAIT : M_WAIT);

                        if (m_infree(class) > 0)
                                continue;

                        /* Check if there's anything at the cache layer */
                        if (mbuf_cached_above(class, wait))
                                break;

                        /* We have nothing and cannot block; give up */
                        if (wait & MCR_NOSLEEP) {
                                if (!(wait & MCR_TRYHARD)) {
                                        m_fail_cnt(class)++;
                                        mbstat.m_drops++;
                                        break;
                                }
                        }

                        /*
                         * If the freelist is still empty and the caller is
                         * willing to be blocked, sleep on the wait channel
                         * until an element is available.  Otherwise, if
                         * MCR_TRYHARD is set, do our best to satisfy the
                         * request without having to go to sleep.
                         */
                        if (mbuf_worker_ready &&
                            mbuf_sleep(class, need, wait))
                                break;

                        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);
                }
        }

        m_alloc_cnt(class) += num - need;
        lck_mtx_unlock(mbuf_mlock);

        return (num - need);
}

/*
 * Common de-allocator for rudimentary objects called by the CPU cache
 * layer when one or more elements need to be returned to the appropriate
 * global freelist.
 */
static void
mbuf_slab_free(void *arg, mcache_obj_t *list, __unused int purged)
{
        mbuf_class_t class = (mbuf_class_t)arg;
        mcache_obj_t *nlist;
        unsigned int num = 0;
        int w;

        ASSERT(MBUF_CLASS_VALID(class) && !MBUF_CLASS_COMPOSITE(class));

        lck_mtx_lock(mbuf_mlock);

        for (;;) {
                nlist = list->obj_next;
                list->obj_next = NULL;
                slab_free(class, list);
                ++num;
                if ((list = nlist) == NULL)
                        break;
        }
        m_free_cnt(class) += num;

        if ((w = mb_waiters) > 0)
                mb_waiters = 0;

        lck_mtx_unlock(mbuf_mlock);

        if (w != 0)
                wakeup(mb_waitchan);
}

/*
 * Common auditor for rudimentary objects called by the CPU cache layer
 * during an allocation or free request.  For the former, this is called
 * after the objects are obtained from either the bucket or slab layer
 * and before they are returned to the caller.  For the latter, this is
 * called immediately during free and before placing the objects into
 * the bucket or slab layer.
 */
static void
mbuf_slab_audit(void *arg, mcache_obj_t *list, boolean_t alloc)
{
        mbuf_class_t class = (mbuf_class_t)arg;
        mcache_audit_t *mca;

        ASSERT(MBUF_CLASS_VALID(class) && !MBUF_CLASS_COMPOSITE(class));

        while (list != NULL) {
                lck_mtx_lock(mbuf_mlock);
                mca = mcl_audit_buf2mca(class, list);

                /* Do the sanity checks */
                if (class == MC_MBUF) {
                        mcl_audit_mbuf(mca, list, FALSE, alloc);
                        ASSERT(mca->mca_uflags & MB_SCVALID);
                } else {
                        mcl_audit_cluster(mca, list, m_maxsize(class),
                            alloc, TRUE);
                        ASSERT(!(mca->mca_uflags & MB_SCVALID));
                }
                /* Record this transaction */
                mcache_buffer_log(mca, list, m_cache(class));
                if (alloc)
                        mca->mca_uflags |= MB_INUSE;
                else
                        mca->mca_uflags &= ~MB_INUSE;
                /* Unpair the object (unconditionally) */
                mca->mca_uptr = NULL;
                lck_mtx_unlock(mbuf_mlock);

                list = list->obj_next;
        }
}

/*
 * Common notify routine for all caches.  It is called by mcache when
 * one or more objects get freed.  We use this indication to trigger
 * the wakeup of any sleeping threads so that they can retry their
 * allocation requests.
 */
static void
mbuf_slab_notify(void *arg, u_int32_t reason)
{
        mbuf_class_t class = (mbuf_class_t)arg;
        int w;

        ASSERT(MBUF_CLASS_VALID(class));

        if (reason != MCN_RETRYALLOC)
                return;

        lck_mtx_lock(mbuf_mlock);
        if ((w = mb_waiters) > 0) {
                m_notified(class)++;
                mb_waiters = 0;
        }
        lck_mtx_unlock(mbuf_mlock);

        if (w != 0)
                wakeup(mb_waitchan);
}

/*
 * Obtain object(s) from the composite class's freelist.
 */
static unsigned int
cslab_alloc(mbuf_class_t class, mcache_obj_t ***plist, unsigned int num)
{
        unsigned int need = num;
        mcl_slab_t *sp, *clsp, *nsp;
        struct mbuf *m;
        mcache_obj_t **list = *plist;
        void *cl;

        VERIFY(need > 0);
        VERIFY(class != MC_MBUF_16KCL || njcl > 0);
        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        /* Get what we can from the freelist */
        while ((*list = m_cobjlist(class)) != NULL) {
                MRANGE(*list);

                m = (struct mbuf *)*list;
                sp = slab_get(m);
                cl = m->m_ext.ext_buf;
                clsp = slab_get(cl);
                VERIFY(m->m_flags == M_EXT && cl != NULL);
                VERIFY(MEXT_RFA(m) != NULL && MBUF_IS_COMPOSITE(m));
                VERIFY(clsp->sl_refcnt == 1);
                if (class == MC_MBUF_BIGCL) {
                        nsp = clsp->sl_next;
                        /* Next slab must already be present */
                        VERIFY(nsp != NULL);
                        VERIFY(nsp->sl_refcnt == 1);
                } else if (class == MC_MBUF_16KCL) {
                        int k;
                        for (nsp = clsp, k = 1;
                            k < (M16KCLBYTES / MCLBYTES); k++) {
                                nsp = nsp->sl_next;
                                /* Next slab must already be present */
                                VERIFY(nsp != NULL);
                                VERIFY(nsp->sl_refcnt == 1);
                        }
                }

                if ((m_cobjlist(class) = (*list)->obj_next) != NULL &&
                    !MBUF_IN_MAP(m_cobjlist(class))) {
                        slab_nextptr_panic(sp, m_cobjlist(class));
                        /* NOTREACHED */
                }
                (*list)->obj_next = NULL;
                list = *plist = &(*list)->obj_next;

                if (--need == 0)
                        break;
        }
        m_infree(class) -= (num - need);

        return (num - need);
}

/*
 * Place object(s) back into a composite class's freelist.
 */
static unsigned int
cslab_free(mbuf_class_t class, mcache_obj_t *list, int purged)
{
        mcache_obj_t *o, *tail;
        unsigned int num = 0;
        struct mbuf *m, *ms;
        mcache_audit_t *mca = NULL;
        mcache_obj_t *ref_list = NULL;
        mcl_slab_t *clsp, *nsp;
        void *cl;

        ASSERT(MBUF_CLASS_VALID(class) && MBUF_CLASS_COMPOSITE(class));
        VERIFY(class != MC_MBUF_16KCL || njcl > 0);
        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        o = tail = list;

        while ((m = ms = (struct mbuf *)o) != NULL) {
                mcache_obj_t *rfa, *nexto = o->obj_next;

                /* Do the mbuf sanity checks */
                if (mclaudit != NULL) {
                        mca = mcl_audit_buf2mca(MC_MBUF, (mcache_obj_t *)m);
                        mcache_audit_free_verify(mca, m, 0, m_maxsize(MC_MBUF));
                        ms = (struct mbuf *)mca->mca_contents;
                }

                /* Do the cluster sanity checks */
                cl = ms->m_ext.ext_buf;
                clsp = slab_get(cl);
                if (mclaudit != NULL) {
                        size_t size;
                        if (class == MC_MBUF_CL)
                                size = m_maxsize(MC_CL);
                        else if (class == MC_MBUF_BIGCL)
                                size = m_maxsize(MC_BIGCL);
                        else
                                size = m_maxsize(MC_16KCL);
                        mcache_audit_free_verify(mcl_audit_buf2mca(MC_CL,
                            (mcache_obj_t *)cl), cl, 0, size);
                }
                VERIFY(ms->m_type == MT_FREE);
                VERIFY(ms->m_flags == M_EXT);
                VERIFY(MEXT_RFA(ms) != NULL && MBUF_IS_COMPOSITE(ms));
                VERIFY(clsp->sl_refcnt == 1);
                if (class == MC_MBUF_BIGCL) {
                        nsp = clsp->sl_next;
                        /* Next slab must already be present */
                        VERIFY(nsp != NULL);
                        VERIFY(nsp->sl_refcnt == 1);
                } else if (class == MC_MBUF_16KCL) {
                        int k;
                        for (nsp = clsp, k = 1;
                            k < (M16KCLBYTES / MCLBYTES); k++) {
                                nsp = nsp->sl_next;
                                /* Next slab must already be present */
                                VERIFY(nsp != NULL);
                                VERIFY(nsp->sl_refcnt == 1);
                        }
                }

                /*
                 * If we're asked to purge, restore the actual mbuf using
                 * contents of the shadow structure (if auditing is enabled)
                 * and clear EXTF_COMPOSITE flag from the mbuf, as we are
                 * about to free it and the attached cluster into their caches.
                 */
                if (purged) {
                        /* Restore constructed mbuf fields */
                        if (mclaudit != NULL)
                                mcl_audit_restore_mbuf(m, mca, TRUE);

                        MEXT_REF(m) = 0;
                        MEXT_FLAGS(m) = 0;

                        rfa = (mcache_obj_t *)MEXT_RFA(m);
                        rfa->obj_next = ref_list;
                        ref_list = rfa;
                        MEXT_RFA(m) = NULL;

                        m->m_type = MT_FREE;
                        m->m_flags = m->m_len = 0;
                        m->m_next = m->m_nextpkt = NULL;

                        /* Save mbuf fields and make auditing happy */
                        if (mclaudit != NULL)
                                mcl_audit_mbuf(mca, o, FALSE, FALSE);

                        VERIFY(m_total(class) > 0);
                        m_total(class)--;

                        /* Free the mbuf */
                        o->obj_next = NULL;
                        slab_free(MC_MBUF, o);

                        /* And free the cluster */
                        ((mcache_obj_t *)cl)->obj_next = NULL;
                        if (class == MC_MBUF_CL)
                                slab_free(MC_CL, cl);
                        else if (class == MC_MBUF_BIGCL)
                                slab_free(MC_BIGCL, cl);
                        else
                                slab_free(MC_16KCL, cl);
                }

                ++num;
                tail = o;
                o = nexto;
        }

        if (!purged) {
                tail->obj_next = m_cobjlist(class);
                m_cobjlist(class) = list;
                m_infree(class) += num;
        } else if (ref_list != NULL) {
                mcache_free_ext(ref_cache, ref_list);
        }

        return (num);
}

/*
 * Common allocator for composite objects called by the CPU cache layer
 * during an allocation request whenever there is no available element in
 * the bucket layer.  It returns one or more composite elements from the
 * appropriate global freelist.  If the freelist is empty, it will attempt
 * to obtain the rudimentary objects from their caches and construct them
 * into composite mbuf + cluster objects.
 */
static unsigned int
mbuf_cslab_alloc(void *arg, mcache_obj_t ***plist, unsigned int needed,
    int wait)
{
        mbuf_class_t class = (mbuf_class_t)arg;
        mcache_t *cp = NULL;
        unsigned int num = 0, cnum = 0, want = needed;
        mcache_obj_t *ref_list = NULL;
        mcache_obj_t *mp_list = NULL;
        mcache_obj_t *clp_list = NULL;
        mcache_obj_t **list;
        struct ext_ref *rfa;
        struct mbuf *m;
        void *cl;

        ASSERT(MBUF_CLASS_VALID(class) && MBUF_CLASS_COMPOSITE(class));
        ASSERT(needed > 0);

        VERIFY(class != MC_MBUF_16KCL || njcl > 0);

        /* There should not be any slab for this class */
        VERIFY(m_slab_cnt(class) == 0 &&
            m_slablist(class).tqh_first == NULL &&
            m_slablist(class).tqh_last == NULL);

        lck_mtx_lock(mbuf_mlock);

        /* Try using the freelist first */
        num = cslab_alloc(class, plist, needed);
        list = *plist;
        if (num == needed) {
                m_alloc_cnt(class) += num;
                lck_mtx_unlock(mbuf_mlock);
                return (needed);
        }

        lck_mtx_unlock(mbuf_mlock);

        /*
         * We could not satisfy the request using the freelist alone;
         * allocate from the appropriate rudimentary caches and use
         * whatever we can get to construct the composite objects.
         */
        needed -= num;

        /*
         * Mark these allocation requests as coming from a composite cache.
         * Also, if the caller is willing to be blocked, mark the request
         * with MCR_FAILOK such that we don't end up sleeping at the mbuf
         * slab layer waiting for the individual object when one or more
         * of the already-constructed composite objects are available.
         */
        wait |= MCR_COMP;
        if (!(wait & MCR_NOSLEEP))
                wait |= MCR_FAILOK;

        needed = mcache_alloc_ext(m_cache(MC_MBUF), &mp_list, needed, wait);
        if (needed == 0) {
                ASSERT(mp_list == NULL);
                goto fail;
        }
        if (class == MC_MBUF_CL)
                cp = m_cache(MC_CL);
        else if (class == MC_MBUF_BIGCL)
                cp = m_cache(MC_BIGCL);
        else
                cp = m_cache(MC_16KCL);
        needed = mcache_alloc_ext(cp, &clp_list, needed, wait);
        if (needed == 0) {
                ASSERT(clp_list == NULL);
                goto fail;
        }
        needed = mcache_alloc_ext(ref_cache, &ref_list, needed, wait);
        if (needed == 0) {
                ASSERT(ref_list == NULL);
                goto fail;
        }

        /*
         * By this time "needed" is MIN(mbuf, cluster, ref).  Any left
         * overs will get freed accordingly before we return to caller.
         */
        for (cnum = 0; cnum < needed; cnum++) {
                struct mbuf *ms;

                m = ms = (struct mbuf *)mp_list;
                mp_list = mp_list->obj_next;

                cl = clp_list;
                clp_list = clp_list->obj_next;
                ((mcache_obj_t *)cl)->obj_next = NULL;

                rfa = (struct ext_ref *)ref_list;
                ref_list = ref_list->obj_next;
                ((mcache_obj_t *)rfa)->obj_next = NULL;

                /*
                 * If auditing is enabled, construct the shadow mbuf
                 * in the audit structure instead of in the actual one.
                 * mbuf_cslab_audit() will take care of restoring the
                 * contents after the integrity check.
                 */
                if (mclaudit != NULL) {
                        mcache_audit_t *mca, *cl_mca;
                        size_t size;

                        lck_mtx_lock(mbuf_mlock);
                        mca = mcl_audit_buf2mca(MC_MBUF, (mcache_obj_t *)m);
                        ms = ((struct mbuf *)mca->mca_contents);
                        cl_mca = mcl_audit_buf2mca(MC_CL, (mcache_obj_t *)cl);

                        /*
                         * Pair them up.  Note that this is done at the time
                         * the mbuf+cluster objects are constructed.  This
                         * information should be treated as "best effort"
                         * debugging hint since more than one mbufs can refer
                         * to a cluster.  In that case, the cluster might not
                         * be freed along with the mbuf it was paired with.
                         */
                        mca->mca_uptr = cl_mca;
                        cl_mca->mca_uptr = mca;

                        ASSERT(mca->mca_uflags & MB_SCVALID);
                        ASSERT(!(cl_mca->mca_uflags & MB_SCVALID));
                        lck_mtx_unlock(mbuf_mlock);

                        /* Technically, they are in the freelist */
                        mcache_set_pattern(MCACHE_FREE_PATTERN, m,
                            m_maxsize(MC_MBUF));
                        if (class == MC_MBUF_CL)
                                size = m_maxsize(MC_CL);
                        else if (class == MC_MBUF_BIGCL)
                                size = m_maxsize(MC_BIGCL);
                        else
                                size = m_maxsize(MC_16KCL);
                        mcache_set_pattern(MCACHE_FREE_PATTERN, cl, size);
                }

                MBUF_INIT(ms, 0, MT_FREE);
                if (class == MC_MBUF_16KCL) {
                        MBUF_16KCL_INIT(ms, cl, rfa, 0, EXTF_COMPOSITE);
                } else if (class == MC_MBUF_BIGCL) {
                        MBUF_BIGCL_INIT(ms, cl, rfa, 0, EXTF_COMPOSITE);
                } else {
                        MBUF_CL_INIT(ms, cl, rfa, 0, EXTF_COMPOSITE);
                }
                VERIFY(ms->m_flags == M_EXT);
                VERIFY(MEXT_RFA(ms) != NULL && MBUF_IS_COMPOSITE(ms));

                *list = (mcache_obj_t *)m;
                (*list)->obj_next = NULL;
                list = *plist = &(*list)->obj_next;
        }

fail:
        /*
         * Free up what's left of the above.
         */
        if (mp_list != NULL)
                mcache_free_ext(m_cache(MC_MBUF), mp_list);
        if (clp_list != NULL)
                mcache_free_ext(cp, clp_list);
        if (ref_list != NULL)
                mcache_free_ext(ref_cache, ref_list);

        lck_mtx_lock(mbuf_mlock);
        if (num > 0 || cnum > 0) {
                m_total(class) += cnum;
                VERIFY(m_total(class) <= m_maxlimit(class));
                m_alloc_cnt(class) += num + cnum;
        }
        if ((num + cnum) < want)
                m_fail_cnt(class) += (want - (num + cnum));
        lck_mtx_unlock(mbuf_mlock);

        return (num + cnum);
}

/*
 * Common de-allocator for composite objects called by the CPU cache
 * layer when one or more elements need to be returned to the appropriate
 * global freelist.
 */
static void
mbuf_cslab_free(void *arg, mcache_obj_t *list, int purged)
{
        mbuf_class_t class = (mbuf_class_t)arg;
        unsigned int num;
        int w;

        ASSERT(MBUF_CLASS_VALID(class) && MBUF_CLASS_COMPOSITE(class));

        lck_mtx_lock(mbuf_mlock);

        num = cslab_free(class, list, purged);
        m_free_cnt(class) += num;

        if ((w = mb_waiters) > 0)
                mb_waiters = 0;

        lck_mtx_unlock(mbuf_mlock);

        if (w != 0)
                wakeup(mb_waitchan);
}

/*
 * Common auditor for composite objects called by the CPU cache layer
 * during an allocation or free request.  For the former, this is called
 * after the objects are obtained from either the bucket or slab layer
 * and before they are returned to the caller.  For the latter, this is
 * called immediately during free and before placing the objects into
 * the bucket or slab layer.
 */
static void
mbuf_cslab_audit(void *arg, mcache_obj_t *list, boolean_t alloc)
{
        mbuf_class_t class = (mbuf_class_t)arg;
        mcache_audit_t *mca;
        struct mbuf *m, *ms;
        mcl_slab_t *clsp, *nsp;
        size_t size;
        void *cl;

        ASSERT(MBUF_CLASS_VALID(class) && MBUF_CLASS_COMPOSITE(class));

        while ((m = ms = (struct mbuf *)list) != NULL) {
                lck_mtx_lock(mbuf_mlock);
                /* Do the mbuf sanity checks and record its transaction */
                mca = mcl_audit_buf2mca(MC_MBUF, (mcache_obj_t *)m);
                mcl_audit_mbuf(mca, m, TRUE, alloc);
                mcache_buffer_log(mca, m, m_cache(class));
                if (alloc)
                        mca->mca_uflags |= MB_COMP_INUSE;
                else
                        mca->mca_uflags &= ~MB_COMP_INUSE;

                /*
                 * Use the shadow mbuf in the audit structure if we are
                 * freeing, since the contents of the actual mbuf has been
                 * pattern-filled by the above call to mcl_audit_mbuf().
                 */
                if (!alloc)
                        ms = (struct mbuf *)mca->mca_contents;

                /* Do the cluster sanity checks and record its transaction */
                cl = ms->m_ext.ext_buf;
                clsp = slab_get(cl);
                VERIFY(ms->m_flags == M_EXT && cl != NULL);
                VERIFY(MEXT_RFA(ms) != NULL && MBUF_IS_COMPOSITE(ms));
                VERIFY(clsp->sl_refcnt == 1);
                if (class == MC_MBUF_BIGCL) {
                        nsp = clsp->sl_next;
                        /* Next slab must already be present */
                        VERIFY(nsp != NULL);
                        VERIFY(nsp->sl_refcnt == 1);
                } else if (class == MC_MBUF_16KCL) {
                        int k;
                        for (nsp = clsp, k = 1;
                            k < (M16KCLBYTES / MCLBYTES); k++) {
                                nsp = nsp->sl_next;
                                /* Next slab must already be present */
                                VERIFY(nsp != NULL);
                                VERIFY(nsp->sl_refcnt == 1);
                        }
                }

                mca = mcl_audit_buf2mca(MC_CL, cl);
                if (class == MC_MBUF_CL)
                        size = m_maxsize(MC_CL);
                else if (class == MC_MBUF_BIGCL)
                        size = m_maxsize(MC_BIGCL);
                else
                        size = m_maxsize(MC_16KCL);
                mcl_audit_cluster(mca, cl, size, alloc, FALSE);
                mcache_buffer_log(mca, cl, m_cache(class));
                if (alloc)
                        mca->mca_uflags |= MB_COMP_INUSE;
                else
                        mca->mca_uflags &= ~MB_COMP_INUSE;
                lck_mtx_unlock(mbuf_mlock);

                list = list->obj_next;
        }
}

/*
 * Allocate some number of mbuf clusters and place on cluster freelist.
 */
static int
m_clalloc(const u_int32_t num, const int wait, const u_int32_t bufsize)
{
        int i;
        vm_size_t size = 0;
        int numpages = 0;
        vm_offset_t page = 0;
        mcache_audit_t *mca_list = NULL;
        mcache_obj_t *con_list = NULL;
        mcl_slab_t *sp;

        VERIFY(bufsize == m_maxsize(MC_CL) ||
            bufsize == m_maxsize(MC_BIGCL) || bufsize == m_maxsize(MC_16KCL));

        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        /*
         * Multiple threads may attempt to populate the cluster map one
         * after another.  Since we drop the lock below prior to acquiring
         * the physical page(s), our view of the cluster map may no longer
         * be accurate, and we could end up over-committing the pages beyond
         * the maximum allowed for each class.  To prevent it, this entire
         * operation (including the page mapping) is serialized.
         */
        while (mb_clalloc_busy) {
                mb_clalloc_waiters++;
                (void) msleep(mb_clalloc_waitchan, mbuf_mlock,
                    (PZERO-1), "m_clalloc", NULL);
                lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);
        }

        /* We are busy now; tell everyone else to go away */
        mb_clalloc_busy = TRUE;

        /*
         * Honor the caller's wish to block or not block.  We have a way
         * to grow the pool asynchronously using the mbuf worker thread.
         */
        i = m_howmany(num, bufsize);
        if (i == 0 || (wait & M_DONTWAIT))
                goto out;

        lck_mtx_unlock(mbuf_mlock);

        size = round_page_32(i * bufsize);
        page = kmem_mb_alloc(mb_map, size);

        if (page == 0) {
                if (bufsize <= m_maxsize(MC_BIGCL)) {
                        /* Try for 1 page if failed, only for 2KB/4KB request */
                        size = NBPG;
                        page = kmem_mb_alloc(mb_map, size);
                }

                if (page == 0) {
                        lck_mtx_lock(mbuf_mlock);
                        goto out;
                }
        }

        VERIFY(IS_P2ALIGNED(page, NBPG));
        numpages = size / NBPG;

        /* If auditing is enabled, allocate the audit structures now */
        if (mclaudit != NULL) {
                int needed;

                /*
                 * Yes, I realize this is a waste of memory for clusters
                 * that never get transformed into mbufs, as we may end
                 * up with NMBPCL-1 unused audit structures per cluster.
                 * But doing so tremendously simplifies the allocation
                 * strategy, since at this point we are not holding the
                 * mbuf lock and the caller is okay to be blocked.  For
                 * the case of big clusters, we allocate one structure
                 * for each as we never turn them into mbufs.
                 */
                if (bufsize == m_maxsize(MC_CL)) {
                        needed = numpages * 2 * NMBPCL;

                        i = mcache_alloc_ext(mcl_audit_con_cache,
                            &con_list, needed, MCR_SLEEP);

                        VERIFY(con_list != NULL && i == needed);
                } else if (bufsize == m_maxsize(MC_BIGCL)) {
                        needed = numpages;
                } else {
                        needed = numpages / (M16KCLBYTES / NBPG);
                }

                i = mcache_alloc_ext(mcache_audit_cache,
                    (mcache_obj_t **)&mca_list, needed, MCR_SLEEP);

                VERIFY(mca_list != NULL && i == needed);
        }

        lck_mtx_lock(mbuf_mlock);

        for (i = 0; i < numpages; i++, page += NBPG) {
                ppnum_t offset = ((char *)page - (char *)mbutl) / NBPG;
                ppnum_t new_page = pmap_find_phys(kernel_pmap,
                    (vm_address_t)page);

                /*
                 * In the case of no mapper being available the following
                 * code noops and returns the input page; if there is a
                 * mapper the appropriate I/O page is returned.
                 */
                new_page = IOMapperInsertPage(mcl_paddr_base, offset, new_page);
                mcl_paddr[offset] = new_page << PGSHIFT;

                /* Pattern-fill this fresh page */
                if (mclaudit != NULL)
                        mcache_set_pattern(MCACHE_FREE_PATTERN,
                            (caddr_t)page, NBPG);

                if (bufsize == m_maxsize(MC_CL)) {
                        union mcluster *mcl = (union mcluster *)page;

                        /* 1st cluster in the page */
                        sp = slab_get(mcl);
                        if (mclaudit != NULL)
                                mcl_audit_init(mcl, &mca_list, &con_list,
                                    AUDIT_CONTENTS_SIZE, NMBPCL);

                        VERIFY(sp->sl_refcnt == 0 && sp->sl_flags == 0);
                        slab_init(sp, MC_CL, SLF_MAPPED,
                            mcl, mcl, bufsize, 0, 1);

                        /* Insert this slab */
                        slab_insert(sp, MC_CL);

                        /* Update stats now since slab_get() drops the lock */
                        mbstat.m_clfree = ++m_infree(MC_CL) +
                            m_infree(MC_MBUF_CL);
                        mbstat.m_clusters = ++m_total(MC_CL);
                        VERIFY(m_total(MC_CL) <= m_maxlimit(MC_CL));

                        /* 2nd cluster in the page */
                        sp = slab_get(++mcl);
                        if (mclaudit != NULL)
                                mcl_audit_init(mcl, &mca_list, &con_list,
                                    AUDIT_CONTENTS_SIZE, NMBPCL);

                        VERIFY(sp->sl_refcnt == 0 && sp->sl_flags == 0);
                        slab_init(sp, MC_CL, SLF_MAPPED,
                            mcl, mcl, bufsize, 0, 1);

                        /* Insert this slab */
                        slab_insert(sp, MC_CL);

                        /* Update stats now since slab_get() drops the lock */
                        mbstat.m_clfree = ++m_infree(MC_CL) +
                            m_infree(MC_MBUF_CL);
                        mbstat.m_clusters = ++m_total(MC_CL);
                        VERIFY(m_total(MC_CL) <= m_maxlimit(MC_CL));
                } else if (bufsize == m_maxsize(MC_BIGCL)) {
                        union mbigcluster *mbc = (union mbigcluster *)page;
                        mcl_slab_t *nsp;

                        /* One for the entire page */
                        sp = slab_get(mbc);
                        if (mclaudit != NULL)
                                mcl_audit_init(mbc, &mca_list, NULL, 0, 1);

                        VERIFY(sp->sl_refcnt == 0 && sp->sl_flags == 0);
                        slab_init(sp, MC_BIGCL, SLF_MAPPED,
                            mbc, mbc, bufsize, 0, 1);

                        /* 2nd cluster's slab is part of the previous one */
                        nsp = slab_get(((union mcluster *)page) + 1);
                        slab_init(nsp, MC_BIGCL, SLF_MAPPED | SLF_PARTIAL,
                            mbc, NULL, 0, 0, 0);

                        /* Insert this slab */
                        slab_insert(sp, MC_BIGCL);

                        /* Update stats now since slab_get() drops the lock */
                        mbstat.m_bigclfree = ++m_infree(MC_BIGCL) +
                            m_infree(MC_MBUF_BIGCL);
                        mbstat.m_bigclusters = ++m_total(MC_BIGCL);
                        VERIFY(m_total(MC_BIGCL) <= m_maxlimit(MC_BIGCL));
                } else if ((i % (M16KCLBYTES / NBPG)) == 0) {
                        union m16kcluster *m16kcl = (union m16kcluster *)page;
                        mcl_slab_t *nsp;
                        int k;

                        VERIFY(njcl > 0);
                        /* One for the entire 16KB */
                        sp = slab_get(m16kcl);
                        if (mclaudit != NULL)
                                mcl_audit_init(m16kcl, &mca_list, NULL, 0, 1);

                        VERIFY(sp->sl_refcnt == 0 && sp->sl_flags == 0);
                        slab_init(sp, MC_16KCL, SLF_MAPPED,
                            m16kcl, m16kcl, bufsize, 0, 1);

                        /* 2nd-8th cluster's slab is part of the first one */
                        for (k = 1; k < (M16KCLBYTES / MCLBYTES); k++) {
                                nsp = slab_get(((union mcluster *)page) + k);
                                VERIFY(nsp->sl_refcnt == 0 &&
                                    nsp->sl_flags == 0);
                                slab_init(nsp, MC_16KCL,
                                    SLF_MAPPED | SLF_PARTIAL,
                                    m16kcl, NULL, 0, 0, 0);
                        }

                        /* Insert this slab */
                        slab_insert(sp, MC_16KCL);

                        /* Update stats now since slab_get() drops the lock */
                        m_infree(MC_16KCL)++;
                        m_total(MC_16KCL)++;
                        VERIFY(m_total(MC_16KCL) <= m_maxlimit(MC_16KCL));
                }
        }
        VERIFY(mca_list == NULL && con_list == NULL);

        /* We're done; let others enter */
        mb_clalloc_busy = FALSE;
        if (mb_clalloc_waiters > 0) {
                mb_clalloc_waiters = 0;
                wakeup(mb_clalloc_waitchan);
        }

        if (bufsize == m_maxsize(MC_CL))
                return (numpages << 1);
        else if (bufsize == m_maxsize(MC_BIGCL))
                return (numpages);

        VERIFY(bufsize == m_maxsize(MC_16KCL));
        return (numpages / (M16KCLBYTES / NBPG));

out:
        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        /* We're done; let others enter */
        mb_clalloc_busy = FALSE;
        if (mb_clalloc_waiters > 0) {
                mb_clalloc_waiters = 0;
                wakeup(mb_clalloc_waitchan);
        }

        /*
         * When non-blocking we kick a thread if we have to grow the
         * pool or if the number of free clusters is less than requested.
         */
        if (bufsize == m_maxsize(MC_CL)) {
                if (i > 0) {
                        /*
                         * Remember total number of clusters needed
                         * at this time.
                         */
                        i += m_total(MC_CL);
                        if (i > mbuf_expand_mcl) {
                                mbuf_expand_mcl = i;
                                if (mbuf_worker_ready)
                                        wakeup((caddr_t)&mbuf_worker_run);
                        }
                }

                if (m_infree(MC_CL) >= num)
                        return (1);
        } else if (bufsize == m_maxsize(MC_BIGCL)) {
                if (i > 0) {
                        /*
                         * Remember total number of 4KB clusters needed
                         * at this time.
                         */
                        i += m_total(MC_BIGCL);
                        if (i > mbuf_expand_big) {
                                mbuf_expand_big = i;
                                if (mbuf_worker_ready)
                                        wakeup((caddr_t)&mbuf_worker_run);
                        }
                }

                if (m_infree(MC_BIGCL) >= num)
                        return (1);
        } else {
                if (i > 0) {
                        /*
                         * Remember total number of 16KB clusters needed
                         * at this time.
                         */
                        i += m_total(MC_16KCL);
                        if (i > mbuf_expand_16k) {
                                mbuf_expand_16k = i;
                                if (mbuf_worker_ready)
                                        wakeup((caddr_t)&mbuf_worker_run);
                        }
                }

                if (m_infree(MC_16KCL) >= num)
                        return (1);
        }
        return (0);
}

/*
 * Populate the global freelist of the corresponding buffer class.
 */
static int
freelist_populate(mbuf_class_t class, unsigned int num, int wait)
{
        mcache_obj_t *o = NULL;
        int i;

        VERIFY(class == MC_MBUF || class == MC_CL || class == MC_BIGCL ||
            class == MC_16KCL);

#if CONFIG_MBUF_NOEXPAND
        if ((mbstat.m_mbufs / NMBPCL) >= maxmbufcl) {
#if DEBUG
                static int printonce = 1;
                if (printonce == 1) {
                        printonce = 0;
                        printf("m_expand failed, allocated %ld out of %d "
                            "clusters\n", mbstat.m_mbufs / NMBPCL,
                            nmbclusters);
                }
#endif /* DEBUG */
                return (0);
        }
#endif /* CONFIG_MBUF_NOEXPAND */

        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        switch (class) {
        case MC_MBUF:
        case MC_CL:
                i = m_clalloc(num, wait, m_maxsize(MC_CL));

                /* Respect the 2K clusters minimum limit */
                if (m_total(MC_CL) == m_maxlimit(MC_CL) &&
                    m_infree(MC_CL) <= m_minlimit(MC_CL)) {
                        if (class != MC_CL || (wait & MCR_COMP))
                                return (0);
                }
                if (class == MC_CL)
                        return (i != 0);
                break;

        case MC_BIGCL:
        case MC_16KCL:
                return (m_clalloc(num, wait, m_maxsize(class)) != 0);
                /* NOTREACHED */

        default:
                VERIFY(0);
                /* NOTREACHED */
        }

        /* Steal a cluster and cut it up to create NMBPCL mbufs */
        if ((o = slab_alloc(MC_CL, wait)) != NULL) {
                struct mbuf *m = (struct mbuf *)o;
                mcache_audit_t *mca = NULL;
                mcl_slab_t *sp = slab_get(o);

                VERIFY(slab_is_detached(sp) &&
                    (sp->sl_flags & (SLF_MAPPED | SLF_PARTIAL)) == SLF_MAPPED);

                /* Make sure that the cluster is unmolested while in freelist */
                if (mclaudit != NULL) {
                        mca = mcl_audit_buf2mca(MC_CL, o);
                        mcache_audit_free_verify(mca, o, 0, m_maxsize(MC_CL));
                }

                /* Reinitialize it as an mbuf slab */
                slab_init(sp, MC_MBUF, sp->sl_flags, sp->sl_base, NULL,
                    sp->sl_len, 0, NMBPCL);

                VERIFY(m == (struct mbuf *)sp->sl_base);
                VERIFY(sp->sl_head == NULL);

                m_total(MC_MBUF) += NMBPCL;
                mbstat.m_mbufs = m_total(MC_MBUF);
                m_infree(MC_MBUF) += NMBPCL;
                mtype_stat_add(MT_FREE, NMBPCL);

                i = NMBPCL;
                while (i--) {
                        /*
                         * If auditing is enabled, construct the shadow mbuf
                         * in the audit structure instead of the actual one.
                         * mbuf_slab_audit() will take care of restoring the
                         * contents after the integrity check.
                         */
                        if (mclaudit != NULL) {
                                struct mbuf *ms;
                                mca = mcl_audit_buf2mca(MC_MBUF,
                                    (mcache_obj_t *)m);
                                ms = ((struct mbuf *)mca->mca_contents);
                                ms->m_type = MT_FREE;
                        } else {
                                m->m_type = MT_FREE;
                        }
                        m->m_next = sp->sl_head;
                        sp->sl_head = (void *)m++;
                }

                /* Insert it into the mbuf class's slab list */
                slab_insert(sp, MC_MBUF);

                if ((i = mb_waiters) > 0)
                        mb_waiters = 0;
                if (i != 0)
                        wakeup(mb_waitchan);

                return (1);
        }

        return (0);
}

/*
 * (Inaccurately) check if it might be worth a trip back to the
 * mcache layer due the availability of objects there.  We'll
 * end up back here if there's nothing up there.
 */
static boolean_t
mbuf_cached_above(mbuf_class_t class, int wait)
{
        switch (class) {
        case MC_MBUF:
                if (wait & MCR_COMP)
                        return (!mcache_bkt_isempty(m_cache(MC_MBUF_CL)) ||
                            !mcache_bkt_isempty(m_cache(MC_MBUF_BIGCL)));
                break;

        case MC_CL:
                if (wait & MCR_COMP)
                        return (!mcache_bkt_isempty(m_cache(MC_MBUF_CL)));
                break;

        case MC_BIGCL:
                if (wait & MCR_COMP)
                        return (!mcache_bkt_isempty(m_cache(MC_MBUF_BIGCL)));
                break;

        case MC_16KCL:
                if (wait & MCR_COMP)
                        return (!mcache_bkt_isempty(m_cache(MC_MBUF_16KCL)));
                break;

        case MC_MBUF_CL:
        case MC_MBUF_BIGCL:
        case MC_MBUF_16KCL:
                break;

        default:
                VERIFY(0);
                /* NOTREACHED */
        }

        return (!mcache_bkt_isempty(m_cache(class)));
}

/*
 * If possible, convert constructed objects to raw ones.
 */
static boolean_t
mbuf_steal(mbuf_class_t class, unsigned int num)
{
        mcache_obj_t *top = NULL;
        mcache_obj_t **list = &top;
        unsigned int tot = 0;

        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        switch (class) {
        case MC_MBUF:
        case MC_CL:
        case MC_BIGCL:
        case MC_16KCL:
                return (FALSE);

        case MC_MBUF_CL:
        case MC_MBUF_BIGCL:
        case MC_MBUF_16KCL:
                /* Get the required number of constructed objects if possible */
                if (m_infree(class) > m_minlimit(class)) {
                        tot = cslab_alloc(class, &list,
                            MIN(num, m_infree(class)));
                }

                /* And destroy them to get back the raw objects */
                if (top != NULL)
                        (void) cslab_free(class, top, 1);
                break;

        default:
                VERIFY(0);
                /* NOTREACHED */
        }

        return (tot == num);
}

static void
m_reclaim(mbuf_class_t class, unsigned int num, boolean_t comp)
{
        int m, bmap = 0;

        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        VERIFY(m_total(MC_CL) <= m_maxlimit(MC_CL));
        VERIFY(m_total(MC_BIGCL) <= m_maxlimit(MC_BIGCL));
        VERIFY(m_total(MC_16KCL) <= m_maxlimit(MC_16KCL));

        /*
         * This logic can be made smarter; for now, simply mark
         * all other related classes as potential victims.
         */
        switch (class) {
        case MC_MBUF:
                m_wantpurge(MC_CL)++;
                m_wantpurge(MC_MBUF_CL)++;
                m_wantpurge(MC_MBUF_BIGCL)++;
                break;

        case MC_CL:
                m_wantpurge(MC_MBUF)++;
                if (!comp)
                        m_wantpurge(MC_MBUF_CL)++;
                break;

        case MC_BIGCL:
                if (!comp)
                        m_wantpurge(MC_MBUF_BIGCL)++;
                break;

        case MC_16KCL:
                if (!comp)
                        m_wantpurge(MC_MBUF_16KCL)++;
                break;

        default:
                VERIFY(0);
                /* NOTREACHED */
        }

        /*
         * Run through each marked class and check if we really need to
         * purge (and therefore temporarily disable) the per-CPU caches
         * layer used by the class.  If so, remember the classes since
         * we are going to drop the lock below prior to purging.
         */
        for (m = 0; m < NELEM(mbuf_table); m++) {
                if (m_wantpurge(m) > 0) {
                        m_wantpurge(m) = 0;
                        /*
                         * Try hard to steal the required number of objects
                         * from the freelist of other mbuf classes.  Only
                         * purge and disable the per-CPU caches layer when
                         * we don't have enough; it's the last resort.
                         */
                        if (!mbuf_steal(m, num))
                                bmap |= (1 << m);
                }
        }

        lck_mtx_unlock(mbuf_mlock);

        if (bmap != 0) {
                /* drain is performed in pfslowtimo(), to avoid deadlocks */
                do_reclaim = 1;

                /* Sigh; we have no other choices but to ask mcache to purge */
                for (m = 0; m < NELEM(mbuf_table); m++) {
                        if ((bmap & (1 << m)) &&
                            mcache_purge_cache(m_cache(m))) {
                                lck_mtx_lock(mbuf_mlock);
                                m_purge_cnt(m)++;
                                mbstat.m_drain++;
                                lck_mtx_unlock(mbuf_mlock);
                        }
                }
        } else {
                /*
                 * Request mcache to reap extra elements from all of its caches;
                 * note that all reaps are serialized and happen only at a fixed
                 * interval.
                 */
                mcache_reap();
        }
        lck_mtx_lock(mbuf_mlock);
}

static inline struct mbuf *
m_get_common(int wait, short type, int hdr)
{
        struct mbuf *m;
        int mcflags = MSLEEPF(wait);

        /* Is this due to a non-blocking retry?  If so, then try harder */
        if (mcflags & MCR_NOSLEEP)
                mcflags |= MCR_TRYHARD;

        m = mcache_alloc(m_cache(MC_MBUF), mcflags);
        if (m != NULL) {
                MBUF_INIT(m, hdr, type);
                mtype_stat_inc(type);
                mtype_stat_dec(MT_FREE);
#if CONFIG_MACF_NET
                if (hdr && mac_init_mbuf(m, wait) != 0) {
                        m_free(m);
                        return (NULL);
                }
#endif /* MAC_NET */
        }
        return (m);
}

/*
 * Space allocation routines; these are also available as macros
 * for critical paths.
 */
#define _M_GET(wait, type)      m_get_common(wait, type, 0)
#define _M_GETHDR(wait, type)   m_get_common(wait, type, 1)
#define _M_RETRY(wait, type)    _M_GET(wait, type)
#define _M_RETRYHDR(wait, type) _M_GETHDR(wait, type)
#define _MGET(m, how, type)     ((m) = _M_GET(how, type))
#define _MGETHDR(m, how, type)  ((m) = _M_GETHDR(how, type))

struct mbuf *
m_get(int wait, int type)
{
        return (_M_GET(wait, type));
}

struct mbuf *
m_gethdr(int wait, int type)
{
        return (_M_GETHDR(wait, type));
}

struct mbuf *
m_retry(int wait, int type)
{
        return (_M_RETRY(wait, type));
}

struct mbuf *
m_retryhdr(int wait, int type)
{
        return (_M_RETRYHDR(wait, type));
}

struct mbuf *
m_getclr(int wait, int type)
{
        struct mbuf *m;

        _MGET(m, wait, type);
        if (m != NULL)
                bzero(MTOD(m, caddr_t), MLEN);
        return (m);
}

struct mbuf *
m_free(struct mbuf *m)
{
        struct mbuf *n = m->m_next;

        if (m->m_type == MT_FREE)
                panic("m_free: freeing an already freed mbuf");

        /* Free the aux data and tags if there is any */
        if (m->m_flags & M_PKTHDR) {
                m_tag_delete_chain(m, NULL);
        }

        if (m->m_flags & M_EXT) {
                u_int32_t refcnt;
                u_int32_t flags;

                refcnt = m_decref(m);
                flags = MEXT_FLAGS(m);
                if (refcnt == 0 && flags == 0) {
                        if (m->m_ext.ext_free == NULL) {
                                mcache_free(m_cache(MC_CL), m->m_ext.ext_buf);
                        } else if (m->m_ext.ext_free == m_bigfree) {
                                mcache_free(m_cache(MC_BIGCL),
                                    m->m_ext.ext_buf);
                        } else if (m->m_ext.ext_free == m_16kfree) {
                                mcache_free(m_cache(MC_16KCL),
                                    m->m_ext.ext_buf);
                        } else {
                                (*(m->m_ext.ext_free))(m->m_ext.ext_buf,
                                    m->m_ext.ext_size, m->m_ext.ext_arg);
                        }
                        mcache_free(ref_cache, MEXT_RFA(m));
                        MEXT_RFA(m) = NULL;
                } else if (refcnt == 0 && (flags & EXTF_COMPOSITE)) {
                        VERIFY(m->m_type != MT_FREE);

                        mtype_stat_dec(m->m_type);
                        mtype_stat_inc(MT_FREE);

                        m->m_type = MT_FREE;
                        m->m_flags = M_EXT;
                        m->m_len = 0;
                        m->m_next = m->m_nextpkt = NULL;

                        /* "Free" into the intermediate cache */
                        if (m->m_ext.ext_free == NULL) {
                                mcache_free(m_cache(MC_MBUF_CL), m);
                        } else if (m->m_ext.ext_free == m_bigfree) {
                                mcache_free(m_cache(MC_MBUF_BIGCL), m);
                        } else {
                                VERIFY(m->m_ext.ext_free == m_16kfree);
                                mcache_free(m_cache(MC_MBUF_16KCL), m);
                        }
                        return (n);
                }
        }

        if (m->m_type != MT_FREE) {
                mtype_stat_dec(m->m_type);
                mtype_stat_inc(MT_FREE);
        }

        m->m_type = MT_FREE;
        m->m_flags = m->m_len = 0;
        m->m_next = m->m_nextpkt = NULL;

        mcache_free(m_cache(MC_MBUF), m);

        return (n);
}

__private_extern__ struct mbuf *
m_clattach(struct mbuf *m, int type, caddr_t extbuf,
    void (*extfree)(caddr_t, u_int, caddr_t), u_int extsize, caddr_t extarg,
    int wait)
{
        struct ext_ref *rfa = NULL;

        if (m == NULL && (m = _M_GETHDR(wait, type)) == NULL)
                return (NULL);

        if (m->m_flags & M_EXT) {
                u_int32_t refcnt;
                u_int32_t flags;

                refcnt = m_decref(m);
                flags = MEXT_FLAGS(m);
                if (refcnt == 0 && flags == 0) {
                        if (m->m_ext.ext_free == NULL) {
                                mcache_free(m_cache(MC_CL), m->m_ext.ext_buf);
                        } else if (m->m_ext.ext_free == m_bigfree) {
                                mcache_free(m_cache(MC_BIGCL),
                                    m->m_ext.ext_buf);
                        } else if (m->m_ext.ext_free == m_16kfree) {
                                mcache_free(m_cache(MC_16KCL),
                                    m->m_ext.ext_buf);
                        } else {
                                (*(m->m_ext.ext_free))(m->m_ext.ext_buf,
                                    m->m_ext.ext_size, m->m_ext.ext_arg);
                        }
                        /* Re-use the reference structure */
                        rfa = MEXT_RFA(m);
                } else if (refcnt == 0 && (flags & EXTF_COMPOSITE)) {
                        VERIFY(m->m_type != MT_FREE);

                        mtype_stat_dec(m->m_type);
                        mtype_stat_inc(MT_FREE);

                        m->m_type = MT_FREE;
                        m->m_flags = M_EXT;
                        m->m_len = 0;
                        m->m_next = m->m_nextpkt = NULL;
                        /* "Free" into the intermediate cache */
                        if (m->m_ext.ext_free == NULL) {
                                mcache_free(m_cache(MC_MBUF_CL), m);
                        } else if (m->m_ext.ext_free == m_bigfree) {
                                mcache_free(m_cache(MC_MBUF_BIGCL), m);
                        } else {
                                VERIFY(m->m_ext.ext_free == m_16kfree);
                                mcache_free(m_cache(MC_MBUF_16KCL), m);
                        }
                        /*
                         * Allocate a new mbuf, since we didn't divorce
                         * the composite mbuf + cluster pair above.
                         */
                        if ((m = _M_GETHDR(wait, type)) == NULL)
                                return (NULL);
                }
        }

        if (rfa == NULL &&
            (rfa = mcache_alloc(ref_cache, MSLEEPF(wait))) == NULL) {
                m_free(m);
                return (NULL);
        }

        MEXT_INIT(m, extbuf, extsize, extfree, extarg, rfa, 1, 0);

        return (m);
}

/* m_mclget() add an mbuf cluster to a normal mbuf */
struct mbuf *
m_mclget(struct mbuf *m, int wait)
{
        struct ext_ref *rfa;

        if ((rfa = mcache_alloc(ref_cache, MSLEEPF(wait))) == NULL)
                return (m);

        m->m_ext.ext_buf = m_mclalloc(wait);
        if (m->m_ext.ext_buf != NULL) {
                MBUF_CL_INIT(m, m->m_ext.ext_buf, rfa, 1, 0);
        } else {
                mcache_free(ref_cache, rfa);
        }
        return (m);
}

/* Allocate an mbuf cluster */
caddr_t
m_mclalloc(int wait)
{
        int mcflags = MSLEEPF(wait);

        /* Is this due to a non-blocking retry?  If so, then try harder */
        if (mcflags & MCR_NOSLEEP)
                mcflags |= MCR_TRYHARD;

        return (mcache_alloc(m_cache(MC_CL), mcflags));
}

/* Free an mbuf cluster */
void
m_mclfree(caddr_t p)
{
        mcache_free(m_cache(MC_CL), p);
}

/*
 * mcl_hasreference() checks if a cluster of an mbuf is referenced by
 * another mbuf
 */
int
m_mclhasreference(struct mbuf *m)
{
        if (!(m->m_flags & M_EXT))
                return (0);

        ASSERT(MEXT_RFA(m) != NULL);

        return (MEXT_REF(m) > 1);
}

__private_extern__ caddr_t
m_bigalloc(int wait)
{
        int mcflags = MSLEEPF(wait);

        /* Is this due to a non-blocking retry?  If so, then try harder */
        if (mcflags & MCR_NOSLEEP)
                mcflags |= MCR_TRYHARD;

        return (mcache_alloc(m_cache(MC_BIGCL), mcflags));
}

__private_extern__ void
m_bigfree(caddr_t p, __unused u_int size, __unused caddr_t arg)
{
        mcache_free(m_cache(MC_BIGCL), p);
}

/* m_mbigget() add an 4KB mbuf cluster to a normal mbuf */
__private_extern__ struct mbuf *
m_mbigget(struct mbuf *m, int wait)
{
        struct ext_ref *rfa;

        if ((rfa = mcache_alloc(ref_cache, MSLEEPF(wait))) == NULL)
                return (m);

        m->m_ext.ext_buf =  m_bigalloc(wait);
        if (m->m_ext.ext_buf != NULL) {
                MBUF_BIGCL_INIT(m, m->m_ext.ext_buf, rfa, 1, 0);
        } else {
                mcache_free(ref_cache, rfa);
        }
        return (m);
}

__private_extern__ caddr_t
m_16kalloc(int wait)
{
        int mcflags = MSLEEPF(wait);

        /* Is this due to a non-blocking retry?  If so, then try harder */
        if (mcflags & MCR_NOSLEEP)
                mcflags |= MCR_TRYHARD;

        return (mcache_alloc(m_cache(MC_16KCL), mcflags));
}

__private_extern__ void
m_16kfree(caddr_t p, __unused u_int size, __unused caddr_t arg)
{
        mcache_free(m_cache(MC_16KCL), p);
}

/* m_m16kget() add a 16KB mbuf cluster to a normal mbuf */
__private_extern__ struct mbuf *
m_m16kget(struct mbuf *m, int wait)
{
        struct ext_ref *rfa;

        if ((rfa = mcache_alloc(ref_cache, MSLEEPF(wait))) == NULL)
                return (m);

        m->m_ext.ext_buf =  m_16kalloc(wait);
        if (m->m_ext.ext_buf != NULL) {
                MBUF_16KCL_INIT(m, m->m_ext.ext_buf, rfa, 1, 0);
        } else {
                mcache_free(ref_cache, rfa);
        }
        return (m);
}

/* */
void
m_copy_pkthdr(struct mbuf *to, struct mbuf *from)
{
#if CONFIG_MACF_NET
        /* We will be taking over the tags of 'to' */
        if (to->m_flags & M_PKTHDR)
                m_tag_delete_chain(to, NULL);
#endif /* MAC_NET */
        to->m_pkthdr = from->m_pkthdr;          /* especially tags */
        m_tag_init(from);                       /* purge tags from src */
        to->m_flags = (from->m_flags & M_COPYFLAGS) | (to->m_flags & M_EXT);
        if ((to->m_flags & M_EXT) == 0)
                to->m_data = to->m_pktdat;
}

/*
 * Duplicate "from"'s mbuf pkthdr in "to".
 * "from" must have M_PKTHDR set, and "to" must be empty.
 * In particular, this does a deep copy of the packet tags.
 */
static int
m_dup_pkthdr(struct mbuf *to, struct mbuf *from, int how)
{
#if CONFIG_MACF_NET
        if (to->m_flags & M_PKTHDR)
                m_tag_delete_chain(to, NULL);
#endif /* MAC_NET */
        to->m_flags = (from->m_flags & M_COPYFLAGS) | (to->m_flags & M_EXT);
        if ((to->m_flags & M_EXT) == 0)
                to->m_data = to->m_pktdat;
        to->m_pkthdr = from->m_pkthdr;
        m_tag_init(to);
        return (m_tag_copy_chain(to, from, how));
}

/*
 * Return a list of mbuf hdrs that point to clusters.  Try for num_needed;
 * if wantall is not set, return whatever number were available.  Set up the
 * first num_with_pkthdrs with mbuf hdrs configured as packet headers; these
 * are chained on the m_nextpkt field.  Any packets requested beyond this
 * are chained onto the last packet header's m_next field.  The size of
 * the cluster is controlled by the parameter bufsize.
 */
__private_extern__ struct mbuf *
m_getpackets_internal(unsigned int *num_needed, int num_with_pkthdrs,
    int wait, int wantall, size_t bufsize)
{
        struct mbuf *m;
        struct mbuf **np, *top;
        unsigned int pnum, needed = *num_needed;
        mcache_obj_t *mp_list = NULL;
        int mcflags = MSLEEPF(wait);
        u_int32_t flag;
        struct ext_ref *rfa;
        mcache_t *cp;
        void *cl;

        ASSERT(bufsize == m_maxsize(MC_CL) ||
            bufsize == m_maxsize(MC_BIGCL) ||
            bufsize == m_maxsize(MC_16KCL));

        /*
         * Caller must first check for njcl because this
         * routine is internal and not exposed/used via KPI.
         */
        VERIFY(bufsize != m_maxsize(MC_16KCL) || njcl > 0);

        top = NULL;
        np = &top;
        pnum = 0;

        /*
         * The caller doesn't want all the requested buffers; only some.
         * Try hard to get what we can, but don't block.  This effectively
         * overrides MCR_SLEEP, since this thread will not go to sleep
         * if we can't get all the buffers.
         */
        if (!wantall || (mcflags & MCR_NOSLEEP))
                mcflags |= MCR_TRYHARD;

        /* Allocate the composite mbuf + cluster elements from the cache */
        if (bufsize == m_maxsize(MC_CL))
                cp = m_cache(MC_MBUF_CL);
        else if (bufsize == m_maxsize(MC_BIGCL))
                cp = m_cache(MC_MBUF_BIGCL);
        else
                cp = m_cache(MC_MBUF_16KCL);
        needed = mcache_alloc_ext(cp, &mp_list, needed, mcflags);

        for (pnum = 0; pnum < needed; pnum++) {
                m = (struct mbuf *)mp_list;
                mp_list = mp_list->obj_next;

                VERIFY(m->m_type == MT_FREE && m->m_flags == M_EXT);
                cl = m->m_ext.ext_buf;
                rfa = MEXT_RFA(m);

                ASSERT(cl != NULL && rfa != NULL);
                VERIFY(MBUF_IS_COMPOSITE(m));

                flag = MEXT_FLAGS(m);

                MBUF_INIT(m, num_with_pkthdrs, MT_DATA);
                if (bufsize == m_maxsize(MC_16KCL)) {
                        MBUF_16KCL_INIT(m, cl, rfa, 1, flag);
                } else if (bufsize == m_maxsize(MC_BIGCL)) {
                        MBUF_BIGCL_INIT(m, cl, rfa, 1, flag);
                } else {
                        MBUF_CL_INIT(m, cl, rfa, 1, flag);
                }

                if (num_with_pkthdrs > 0) {
                        --num_with_pkthdrs;
#if CONFIG_MACF_NET
                        if (mac_mbuf_label_init(m, wait) != 0) {
                                m_free(m);
                                break;
                        }
#endif /* MAC_NET */
                }

                *np = m;
                if (num_with_pkthdrs > 0)
                        np = &m->m_nextpkt;
                else
                        np = &m->m_next;
        }
        ASSERT(pnum != *num_needed || mp_list == NULL);
        if (mp_list != NULL)
                mcache_free_ext(cp, mp_list);

        if (pnum > 0) {
                mtype_stat_add(MT_DATA, pnum);
                mtype_stat_sub(MT_FREE, pnum);
        }

        if (wantall && (pnum != *num_needed)) {
                if (top != NULL)
                        m_freem_list(top);
                return (NULL);
        }

        *num_needed = pnum;
        return (top);
}

/*
 * Return list of mbuf linked by m_nextpkt.  Try for numlist, and if
 * wantall is not set, return whatever number were available.  The size of
 * each mbuf in the list is controlled by the parameter packetlen.  Each
 * mbuf of the list may have a chain of mbufs linked by m_next.  Each mbuf
 * in the chain is called a segment.  If maxsegments is not null and the
 * value pointed to is not null, this specify the maximum number of segments
 * for a chain of mbufs.  If maxsegments is zero or the value pointed to
 * is zero the caller does not have any restriction on the number of segments.
 * The actual  number of segments of a mbuf chain is return in the value
 * pointed to by maxsegments.
 */
__private_extern__ struct mbuf *
m_allocpacket_internal(unsigned int *numlist, size_t packetlen,
    unsigned int *maxsegments, int wait, int wantall, size_t wantsize)
{
        struct mbuf **np, *top, *first = NULL;
        size_t bufsize, r_bufsize;
        unsigned int num = 0;
        unsigned int nsegs = 0;
        unsigned int needed, resid;
        int mcflags = MSLEEPF(wait);
        mcache_obj_t *mp_list = NULL, *rmp_list = NULL;
        mcache_t *cp = NULL, *rcp = NULL;

        if (*numlist == 0)
                return (NULL);

        top = NULL;
        np = &top;

        if (wantsize == 0) {
                if (packetlen <= MINCLSIZE) {
                        bufsize = packetlen;
                } else if (packetlen > m_maxsize(MC_CL)) {
                        /* Use 4KB if jumbo cluster pool isn't available */
                        if (packetlen <= m_maxsize(MC_BIGCL) || njcl == 0)
                                bufsize = m_maxsize(MC_BIGCL);
                        else
                                bufsize = m_maxsize(MC_16KCL);
                } else {
                        bufsize = m_maxsize(MC_CL);
                }
        } else if (wantsize == m_maxsize(MC_CL) ||
            wantsize == m_maxsize(MC_BIGCL) ||
            (wantsize == m_maxsize(MC_16KCL) && njcl > 0)) {
                bufsize = wantsize;
        } else {
                return (NULL);
        }

        if (bufsize <= MHLEN) {
                nsegs = 1;
        } else if (bufsize <= MINCLSIZE) {
                if (maxsegments != NULL && *maxsegments == 1) {
                        bufsize = m_maxsize(MC_CL);
                        nsegs = 1;
                } else {
                        nsegs = 2;
                }
        } else if (bufsize == m_maxsize(MC_16KCL)) {
                VERIFY(njcl > 0);
                nsegs = ((packetlen - 1) >> (PGSHIFT + 2)) + 1;
        } else if (bufsize == m_maxsize(MC_BIGCL)) {
                nsegs = ((packetlen - 1) >> PGSHIFT) + 1;
        } else {
                nsegs = ((packetlen - 1) >> MCLSHIFT) + 1;
        }
        if (maxsegments != NULL) {
                if (*maxsegments && nsegs > *maxsegments) {
                        *maxsegments = nsegs;
                        return (NULL);
                }
                *maxsegments = nsegs;
        }

        /*
         * The caller doesn't want all the requested buffers; only some.
         * Try hard to get what we can, but don't block.  This effectively
         * overrides MCR_SLEEP, since this thread will not go to sleep
         * if we can't get all the buffers.
         */
        if (!wantall || (mcflags & MCR_NOSLEEP))
                mcflags |= MCR_TRYHARD;

        /*
         * Simple case where all elements in the lists/chains are mbufs.
         * Unless bufsize is greater than MHLEN, each segment chain is made
         * up of exactly 1 mbuf.  Otherwise, each segment chain is made up
         * of 2 mbufs; the second one is used for the residual data, i.e.
         * the remaining data that cannot fit into the first mbuf.
         */
        if (bufsize <= MINCLSIZE) {
                /* Allocate the elements in one shot from the mbuf cache */
                ASSERT(bufsize <= MHLEN || nsegs == 2);
                cp = m_cache(MC_MBUF);
                needed = mcache_alloc_ext(cp, &mp_list,
                    (*numlist) * nsegs, mcflags);

                /*
                 * The number of elements must be even if we are to use an
                 * mbuf (instead of a cluster) to store the residual data.
                 * If we couldn't allocate the requested number of mbufs,
                 * trim the number down (if it's odd) in order to avoid
                 * creating a partial segment chain.
                 */
                if (bufsize > MHLEN && (needed & 0x1))
                        needed--;

                while (num < needed) {
                        struct mbuf *m;

                        m = (struct mbuf *)mp_list;
                        mp_list = mp_list->obj_next;
                        ASSERT(m != NULL);

                        MBUF_INIT(m, 1, MT_DATA);
#if CONFIG_MACF_NET
                        if (mac_init_mbuf(m, wait) != 0) {
                                m_free(m);
                                break;
                        }
#endif /* MAC_NET */
                        num++;
                        if (bufsize > MHLEN) {
                                /* A second mbuf for this segment chain */
                                m->m_next = (struct mbuf *)mp_list;
                                mp_list = mp_list->obj_next;
                                ASSERT(m->m_next != NULL);

                                MBUF_INIT(m->m_next, 0, MT_DATA);
                                num++;
                        }
                        *np = m;
                        np = &m->m_nextpkt;
                }
                ASSERT(num != *numlist || mp_list == NULL);

                if (num > 0) {
                        mtype_stat_add(MT_DATA, num);
                        mtype_stat_sub(MT_FREE, num);
                }
                num /= nsegs;

                /* We've got them all; return to caller */
                if (num == *numlist)
                        return (top);

                goto fail;
        }

        /*
         * Complex cases where elements are made up of one or more composite
         * mbufs + cluster, depending on packetlen.  Each N-segment chain can
         * be illustrated as follows:
         *
         * [mbuf + cluster 1] [mbuf + cluster 2] ... [mbuf + cluster N]
         *
         * Every composite mbuf + cluster element comes from the intermediate
         * cache (either MC_MBUF_CL or MC_MBUF_BIGCL).  For space efficiency,
         * the last composite element will come from the MC_MBUF_CL cache,
         * unless the residual data is larger than 2KB where we use the
         * big cluster composite cache (MC_MBUF_BIGCL) instead.  Residual
         * data is defined as extra data beyond the first element that cannot
         * fit into the previous element, i.e. there is no residual data if
         * the chain only has 1 segment.
         */
        r_bufsize = bufsize;
        resid = packetlen > bufsize ? packetlen % bufsize : 0;
        if (resid > 0) {
                /* There is residual data; figure out the cluster size */
                if (wantsize == 0 && packetlen > MINCLSIZE) {
                        /*
                         * Caller didn't request that all of the segments
                         * in the chain use the same cluster size; use the
                         * smaller of the cluster sizes.
                         */
                        if (njcl > 0 && resid > m_maxsize(MC_BIGCL))
                                r_bufsize = m_maxsize(MC_16KCL);
                        else if (resid > m_maxsize(MC_CL))
                                r_bufsize = m_maxsize(MC_BIGCL);
                        else
                                r_bufsize = m_maxsize(MC_CL);
                } else {
                        /* Use the same cluster size as the other segments */
                        resid = 0;
                }
        }

        needed = *numlist;
        if (resid > 0) {
                /*
                 * Attempt to allocate composite mbuf + cluster elements for
                 * the residual data in each chain; record the number of such
                 * elements that can be allocated so that we know how many
                 * segment chains we can afford to create.
                 */
                if (r_bufsize <= m_maxsize(MC_CL))
                        rcp = m_cache(MC_MBUF_CL);
                else if (r_bufsize <= m_maxsize(MC_BIGCL))
                        rcp = m_cache(MC_MBUF_BIGCL);
                else
                        rcp = m_cache(MC_MBUF_16KCL);
                needed = mcache_alloc_ext(rcp, &rmp_list, *numlist, mcflags);

                if (needed == 0)
                        goto fail;

                /* This is temporarily reduced for calculation */
                ASSERT(nsegs > 1);
                nsegs--;
        }

        /*
         * Attempt to allocate the rest of the composite mbuf + cluster
         * elements for the number of segment chains that we need.
         */
        if (bufsize <= m_maxsize(MC_CL))
                cp = m_cache(MC_MBUF_CL);
        else if (bufsize <= m_maxsize(MC_BIGCL))
                cp = m_cache(MC_MBUF_BIGCL);
        else
                cp = m_cache(MC_MBUF_16KCL);
        needed = mcache_alloc_ext(cp, &mp_list, needed * nsegs, mcflags);

        /* Round it down to avoid creating a partial segment chain */
        needed = (needed / nsegs) * nsegs;
        if (needed == 0)
                goto fail;

        if (resid > 0) {
                /*
                 * We're about to construct the chain(s); take into account
                 * the number of segments we have created above to hold the
                 * residual data for each chain, as well as restore the
                 * original count of segments per chain.
                 */
                ASSERT(nsegs > 0);
                needed += needed / nsegs;
                nsegs++;
        }

        for (;;) {
                struct mbuf *m;
                u_int32_t flag;
                struct ext_ref *rfa;
                void *cl;
                int pkthdr;

                ++num;
                if (nsegs == 1 || (num % nsegs) != 0 || resid == 0) {
                        m = (struct mbuf *)mp_list;
                        mp_list = mp_list->obj_next;
                } else {
                        m = (struct mbuf *)rmp_list;
                        rmp_list = rmp_list->obj_next;
                }
                ASSERT(m != NULL);
                VERIFY(m->m_type == MT_FREE && m->m_flags == M_EXT);
                VERIFY(m->m_ext.ext_free == NULL ||
                    m->m_ext.ext_free == m_bigfree ||
                    m->m_ext.ext_free == m_16kfree);

                cl = m->m_ext.ext_buf;
                rfa = MEXT_RFA(m);

                ASSERT(cl != NULL && rfa != NULL);
                VERIFY(MBUF_IS_COMPOSITE(m));

                flag = MEXT_FLAGS(m);

                pkthdr = (nsegs == 1 || (num % nsegs) == 1);
                if (pkthdr)
                        first = m;
                MBUF_INIT(m, pkthdr, MT_DATA);
                if (m->m_ext.ext_free == m_16kfree) {
                        MBUF_16KCL_INIT(m, cl, rfa, 1, flag);
                } else if (m->m_ext.ext_free == m_bigfree) {
                        MBUF_BIGCL_INIT(m, cl, rfa, 1, flag);
                } else {
                        MBUF_CL_INIT(m, cl, rfa, 1, flag);
                }
#if CONFIG_MACF_NET
                if (pkthdr && mac_init_mbuf(m, wait) != 0) {
                        --num;
                        m_free(m);
                        break;
                }
#endif /* MAC_NET */

                *np = m;
                if ((num % nsegs) == 0)
                        np = &first->m_nextpkt;
                else
                        np = &m->m_next;

                if (num == needed)
                        break;
        }

        if (num > 0) {
                mtype_stat_add(MT_DATA, num);
                mtype_stat_sub(MT_FREE, num);
        }

        num /= nsegs;

        /* We've got them all; return to caller */
        if (num == *numlist) {
                ASSERT(mp_list == NULL && rmp_list == NULL);
                return (top);
        }

fail:
        /* Free up what's left of the above */
        if (mp_list != NULL)
                mcache_free_ext(cp, mp_list);
        if (rmp_list != NULL)
                mcache_free_ext(rcp, rmp_list);
        if (wantall && top != NULL) {
                m_freem(top);
                return (NULL);
        }
        *numlist = num;
        return (top);
}

/*
 * Best effort to get a mbuf cluster + pkthdr.  Used by drivers to allocated
 * packets on receive ring.
 */
__private_extern__ struct mbuf *
m_getpacket_how(int wait)
{
        unsigned int num_needed = 1;

        return (m_getpackets_internal(&num_needed, 1, wait, 1,
            m_maxsize(MC_CL)));
}

/*
 * Best effort to get a mbuf cluster + pkthdr.  Used by drivers to allocated
 * packets on receive ring.
 */
struct mbuf *
m_getpacket(void)
{
        unsigned int num_needed = 1;

        return (m_getpackets_internal(&num_needed, 1, M_WAIT, 1,
            m_maxsize(MC_CL)));
}

/*
 * Return a list of mbuf hdrs that point to clusters.  Try for num_needed;
 * if this can't be met, return whatever number were available.  Set up the
 * first num_with_pkthdrs with mbuf hdrs configured as packet headers.  These
 * are chained on the m_nextpkt field.  Any packets requested beyond this are
 * chained onto the last packet header's m_next field.
 */
struct mbuf *
m_getpackets(int num_needed, int num_with_pkthdrs, int how)
{
        unsigned int n = num_needed;

        return (m_getpackets_internal(&n, num_with_pkthdrs, how, 0,
            m_maxsize(MC_CL)));
}

/*
 * Return a list of mbuf hdrs set up as packet hdrs chained together
 * on the m_nextpkt field
 */
struct mbuf *
m_getpackethdrs(int num_needed, int how)
{
        struct mbuf *m;
        struct mbuf **np, *top;

        top = NULL;
        np = &top;

        while (num_needed--) {
                m = _M_RETRYHDR(how, MT_DATA);
                if (m == NULL)
                        break;

                *np = m;
                np = &m->m_nextpkt;
        }

        return (top);
}

/*
 * Free an mbuf list (m_nextpkt) while following m_next.  Returns the count
 * for mbufs packets freed.  Used by the drivers.
 */
int
m_freem_list(struct mbuf *m)
{
        struct mbuf *nextpkt;
        mcache_obj_t *mp_list = NULL;
        mcache_obj_t *mcl_list = NULL;
        mcache_obj_t *mbc_list = NULL;
        mcache_obj_t *m16k_list = NULL;
        mcache_obj_t *m_mcl_list = NULL;
        mcache_obj_t *m_mbc_list = NULL;
        mcache_obj_t *m_m16k_list = NULL;
        mcache_obj_t *ref_list = NULL;
        int pktcount = 0;
        int mt_free = 0, mt_data = 0, mt_header = 0, mt_soname = 0, mt_tag = 0;

        while (m != NULL) {
                pktcount++;

                nextpkt = m->m_nextpkt;
                m->m_nextpkt = NULL;

                while (m != NULL) {
                        struct mbuf *next = m->m_next;
                        mcache_obj_t *o, *rfa;
                        u_int32_t refcnt, flags;

                        if (m->m_type == MT_FREE)
                                panic("m_free: freeing an already freed mbuf");

                        if (m->m_type != MT_FREE)
                                mt_free++;

                        if (m->m_flags & M_PKTHDR) {
                                m_tag_delete_chain(m, NULL);
                        }

                        if (!(m->m_flags & M_EXT))
                                goto simple_free;

                        o = (mcache_obj_t *)m->m_ext.ext_buf;
                        refcnt = m_decref(m);
                        flags = MEXT_FLAGS(m);
                        if (refcnt == 0 && flags == 0) {
                                if (m->m_ext.ext_free == NULL) {
                                        o->obj_next = mcl_list;
                                        mcl_list = o;
                                } else if (m->m_ext.ext_free == m_bigfree) {
                                        o->obj_next = mbc_list;
                                        mbc_list = o;
                                } else if (m->m_ext.ext_free == m_16kfree) {
                                        o->obj_next = m16k_list;
                                        m16k_list = o;
                                } else {
                                        (*(m->m_ext.ext_free))((caddr_t)o,
                                            m->m_ext.ext_size,
                                            m->m_ext.ext_arg);
                                }
                                rfa = (mcache_obj_t *)MEXT_RFA(m);
                                rfa->obj_next = ref_list;
                                ref_list = rfa;
                                MEXT_RFA(m) = NULL;
                        } else if (refcnt == 0 && (flags & EXTF_COMPOSITE)) {
                                VERIFY(m->m_type != MT_FREE);
                                /*
                                 * Amortize the costs of atomic operations
                                 * by doing them at the end, if possible.
                                 */
                                if (m->m_type == MT_DATA)
                                        mt_data++;
                                else if (m->m_type == MT_HEADER)
                                        mt_header++;
                                else if (m->m_type == MT_SONAME)
                                        mt_soname++;
                                else if (m->m_type == MT_TAG)
                                        mt_tag++;
                                else
                                        mtype_stat_dec(m->m_type);

                                m->m_type = MT_FREE;
                                m->m_flags = M_EXT;
                                m->m_len = 0;
                                m->m_next = m->m_nextpkt = NULL;

                                /* "Free" into the intermediate cache */
                                o = (mcache_obj_t *)m;
                                if (m->m_ext.ext_free == NULL) {
                                        o->obj_next = m_mcl_list;
                                        m_mcl_list = o;
                                } else if (m->m_ext.ext_free == m_bigfree) {
                                        o->obj_next = m_mbc_list;
                                        m_mbc_list = o;
                                } else {
                                        VERIFY(m->m_ext.ext_free == m_16kfree);
                                        o->obj_next = m_m16k_list;
                                        m_m16k_list = o;
                                }
                                m = next;
                                continue;
                        }
simple_free:
                        /*
                         * Amortize the costs of atomic operations
                         * by doing them at the end, if possible.
                         */
                        if (m->m_type == MT_DATA)
                                mt_data++;
                        else if (m->m_type == MT_HEADER)
                                mt_header++;
                        else if (m->m_type == MT_SONAME)
                                mt_soname++;
                        else if (m->m_type == MT_TAG)
                                mt_tag++;
                        else if (m->m_type != MT_FREE)
                                mtype_stat_dec(m->m_type);

                        m->m_type = MT_FREE;
                        m->m_flags = m->m_len = 0;
                        m->m_next = m->m_nextpkt = NULL;

                        ((mcache_obj_t *)m)->obj_next = mp_list;
                        mp_list = (mcache_obj_t *)m;

                        m = next;
                }

                m = nextpkt;
        }

        if (mt_free > 0)
                mtype_stat_add(MT_FREE, mt_free);
        if (mt_data > 0)
                mtype_stat_sub(MT_DATA, mt_data);
        if (mt_header > 0)
                mtype_stat_sub(MT_HEADER, mt_header);
        if (mt_soname > 0)
                mtype_stat_sub(MT_SONAME, mt_soname);
        if (mt_tag > 0)
                mtype_stat_sub(MT_TAG, mt_tag);

        if (mp_list != NULL)
                mcache_free_ext(m_cache(MC_MBUF), mp_list);
        if (mcl_list != NULL)
                mcache_free_ext(m_cache(MC_CL), mcl_list);
        if (mbc_list != NULL)
                mcache_free_ext(m_cache(MC_BIGCL), mbc_list);
        if (m16k_list != NULL)
                mcache_free_ext(m_cache(MC_16KCL), m16k_list);
        if (m_mcl_list != NULL)
                mcache_free_ext(m_cache(MC_MBUF_CL), m_mcl_list);
        if (m_mbc_list != NULL)
                mcache_free_ext(m_cache(MC_MBUF_BIGCL), m_mbc_list);
        if (m_m16k_list != NULL)
                mcache_free_ext(m_cache(MC_MBUF_16KCL), m_m16k_list);
        if (ref_list != NULL)
                mcache_free_ext(ref_cache, ref_list);

        return (pktcount);
}

void
m_freem(struct mbuf *m)
{
        while (m != NULL)
                m = m_free(m);
}

/*
 * Mbuffer utility routines.
 */

/*
 * Compute the amount of space available before the current start
 * of data in an mbuf.
 */
int
m_leadingspace(struct mbuf *m)
{
        if (m->m_flags & M_EXT) {
                if (MCLHASREFERENCE(m))
                        return (0);
                return (m->m_data - m->m_ext.ext_buf);
        }
        if (m->m_flags & M_PKTHDR)
                return (m->m_data - m->m_pktdat);
        return (m->m_data - m->m_dat);
}

/*
 * Compute the amount of space available after the end of data in an mbuf.
 */
int
m_trailingspace(struct mbuf *m)
{
        if (m->m_flags & M_EXT) {
                if (MCLHASREFERENCE(m))
                        return (0);
                return (m->m_ext.ext_buf + m->m_ext.ext_size -
                    (m->m_data + m->m_len));
        }
        return (&m->m_dat[MLEN] - (m->m_data + m->m_len));
}

/*
 * Lesser-used path for M_PREPEND: allocate new mbuf to prepend to chain,
 * copy junk along.  Does not adjust packet header length.
 */
struct mbuf *
m_prepend(struct mbuf *m, int len, int how)
{
        struct mbuf *mn;

        _MGET(mn, how, m->m_type);
        if (mn == NULL) {
                m_freem(m);
                return (NULL);
        }
        if (m->m_flags & M_PKTHDR) {
                M_COPY_PKTHDR(mn, m);
                m->m_flags &= ~M_PKTHDR;
        }
        mn->m_next = m;
        m = mn;
        if (len < MHLEN)
                MH_ALIGN(m, len);
        m->m_len = len;
        return (m);
}

/*
 * Replacement for old M_PREPEND macro: allocate new mbuf to prepend to
 * chain, copy junk along, and adjust length.
 */
struct mbuf *
m_prepend_2(struct mbuf *m, int len, int how)
{
        if (M_LEADINGSPACE(m) >= len) {
                m->m_data -= len;
                m->m_len += len;
        } else {
                m = m_prepend(m, len, how);
        }
        if ((m) && (m->m_flags & M_PKTHDR))
                m->m_pkthdr.len += len;
        return (m);
}

/*
 * Make a copy of an mbuf chain starting "off0" bytes from the beginning,
 * continuing for "len" bytes.  If len is M_COPYALL, copy to end of mbuf.
 * The wait parameter is a choice of M_WAIT/M_DONTWAIT from caller.
 */
int MCFail;

struct mbuf *
m_copym(struct mbuf *m, int off0, int len, int wait)
{
        struct mbuf *n, *mhdr = NULL, **np;
        int off = off0;
        struct mbuf *top;
        int copyhdr = 0;

        if (off < 0 || len < 0)
                panic("m_copym: invalid offset %d or len %d", off, len);

        if (off == 0 && (m->m_flags & M_PKTHDR)) {
                mhdr = m;
                copyhdr = 1;
        }

        while (off >= m->m_len) {
                if (m->m_next == NULL)
                        panic("m_copym: invalid mbuf chain");
                off -= m->m_len;
                m = m->m_next;
        }
        np = &top;
        top = NULL;

        while (len > 0) {
                if (m == NULL) {
                        if (len != M_COPYALL)
                                panic("m_copym: len != M_COPYALL");
                        break;
                }

                n = _M_RETRY(wait, m->m_type);
                *np = n;

                if (n == NULL)
                        goto nospace;

                if (copyhdr != 0) {
                        M_COPY_PKTHDR(n, mhdr);
                        if (len == M_COPYALL)
                                n->m_pkthdr.len -= off0;
                        else
                                n->m_pkthdr.len = len;
                        copyhdr = 0;
                }
                if (len == M_COPYALL) {
                        if (MIN(len, (m->m_len - off)) == len) {
                                printf("m->m_len %ld - off %d = %ld, %ld\n",
                                    m->m_len, off, m->m_len - off,
                                    MIN(len, (m->m_len - off)));
                        }
                }
                n->m_len = MIN(len, (m->m_len - off));
                if (n->m_len == M_COPYALL) {
                        printf("n->m_len == M_COPYALL, fixing\n");
                        n->m_len = MHLEN;
                }
                if (m->m_flags & M_EXT) {
                        n->m_ext = m->m_ext;
                        m_incref(m);
                        n->m_data = m->m_data + off;
                        n->m_flags |= M_EXT;
                } else {
                        bcopy(MTOD(m, caddr_t)+off, MTOD(n, caddr_t),
                            (unsigned)n->m_len);
                }
                if (len != M_COPYALL)
                        len -= n->m_len;
                off = 0;
                m = m->m_next;
                np = &n->m_next;
        }

        if (top == NULL)
                MCFail++;

        return (top);
nospace:

        m_freem(top);
        MCFail++;
        return (NULL);
}

/*
 * Equivalent to m_copym except that all necessary mbuf hdrs are allocated
 * within this routine also, the last mbuf and offset accessed are passed
 * out and can be passed back in to avoid having to rescan the entire mbuf
 * list (normally hung off of the socket)
 */
struct mbuf *
m_copym_with_hdrs(struct mbuf *m, int off0, int len0, int wait,
    struct mbuf **m_last, int *m_off)
{
        struct mbuf *n, **np = NULL;
        int off = off0, len = len0;
        struct mbuf *top = NULL;
        int mcflags = MSLEEPF(wait);
        int copyhdr = 0;
        int type = 0;
        mcache_obj_t *list = NULL;
        int needed = 0;

        if (off == 0 && (m->m_flags & M_PKTHDR))
                copyhdr = 1;

        if (*m_last != NULL) {
                m = *m_last;
                off = *m_off;
        } else {
                while (off >= m->m_len) {
                        off -= m->m_len;
                        m = m->m_next;
                }
        }

        n = m;
        while (len > 0) {
                needed++;
                ASSERT(n != NULL);
                len -= MIN(len, (n->m_len - ((needed == 1) ? off : 0)));
                n = n->m_next;
        }
        needed++;
        len = len0;

        /*
         * If the caller doesn't want to be put to sleep, mark it with
         * MCR_TRYHARD so that we may reclaim buffers from other places
         * before giving up.
         */
        if (mcflags & MCR_NOSLEEP)
                mcflags |= MCR_TRYHARD;

        if (mcache_alloc_ext(m_cache(MC_MBUF), &list, needed,
            mcflags) != needed)
                goto nospace;

        needed = 0;
        while (len > 0) {
                n = (struct mbuf *)list;
                list = list->obj_next;
                ASSERT(n != NULL && m != NULL);

                type = (top == NULL) ? MT_HEADER : m->m_type;
                MBUF_INIT(n, (top == NULL), type);
#if CONFIG_MACF_NET
                if (top == NULL && mac_mbuf_label_init(n, wait) != 0) {
                        mtype_stat_inc(MT_HEADER);
                        mtype_stat_dec(MT_FREE);
                        m_free(n);
                        goto nospace;
                }
#endif /* MAC_NET */

                if (top == NULL) {
                        top = n;
                        np = &top->m_next;
                        continue;
                } else {
                        needed++;
                        *np = n;
                }

                if (copyhdr) {
                        M_COPY_PKTHDR(n, m);
                        n->m_pkthdr.len = len;
                        copyhdr = 0;
                }
                n->m_len = MIN(len, (m->m_len - off));

                if (m->m_flags & M_EXT) {
                        n->m_ext = m->m_ext;
                        m_incref(m);
                        n->m_data = m->m_data + off;
                        n->m_flags |= M_EXT;
                } else {
                        bcopy(MTOD(m, caddr_t)+off, MTOD(n, caddr_t),
                            (unsigned)n->m_len);
                }
                len -= n->m_len;

                if (len == 0) {
                        if ((off + n->m_len) == m->m_len) {
                                *m_last = m->m_next;
                                *m_off  = 0;
                        } else {
                                *m_last = m;
                                *m_off  = off + n->m_len;
                        }
                        break;
                }
                off = 0;
                m = m->m_next;
                np = &n->m_next;
        }

        mtype_stat_inc(MT_HEADER);
        mtype_stat_add(type, needed);
        mtype_stat_sub(MT_FREE, needed + 1);

        ASSERT(list == NULL);
        return (top);

nospace:
        if (list != NULL)
                mcache_free_ext(m_cache(MC_MBUF), list);
        if (top != NULL)
                m_freem(top);
        MCFail++;
        return (NULL);
}

/*
 * Copy data from an mbuf chain starting "off" bytes from the beginning,
 * continuing for "len" bytes, into the indicated buffer.
 */
void
m_copydata(struct mbuf *m, int off, int len, caddr_t cp)
{
        unsigned count;

        if (off < 0 || len < 0)
                panic("m_copydata: invalid offset %d or len %d", off, len);

        while (off > 0) {
                if (m == NULL)
                        panic("m_copydata: invalid mbuf chain");
                if (off < m->m_len)
                        break;
                off -= m->m_len;
                m = m->m_next;
        }
        while (len > 0) {
                if (m == NULL)
                        panic("m_copydata: invalid mbuf chain");
                count = MIN(m->m_len - off, len);
                bcopy(MTOD(m, caddr_t) + off, cp, count);
                len -= count;
                cp += count;
                off = 0;
                m = m->m_next;
        }
}

/*
 * Concatenate mbuf chain n to m.  Both chains must be of the same type
 * (e.g. MT_DATA).  Any m_pkthdr is not updated.
 */
void
m_cat(struct mbuf *m, struct mbuf *n)
{
        while (m->m_next)
                m = m->m_next;
        while (n) {
                if ((m->m_flags & M_EXT) ||
                    m->m_data + m->m_len + n->m_len >= &m->m_dat[MLEN]) {
                        /* just join the two chains */
                        m->m_next = n;
                        return;
                }
                /* splat the data from one into the other */
                bcopy(MTOD(n, caddr_t), MTOD(m, caddr_t) + m->m_len,
                    (u_int)n->m_len);
                m->m_len += n->m_len;
                n = m_free(n);
        }
}

void
m_adj(struct mbuf *mp, int req_len)
{
        int len = req_len;
        struct mbuf *m;
        int count;

        if ((m = mp) == NULL)
                return;
        if (len >= 0) {
                /*
                 * Trim from head.
                 */
                while (m != NULL && len > 0) {
                        if (m->m_len <= len) {
                                len -= m->m_len;
                                m->m_len = 0;
                                m = m->m_next;
                        } else {
                                m->m_len -= len;
                                m->m_data += len;
                                len = 0;
                        }
                }
                m = mp;
                if (m->m_flags & M_PKTHDR)
                        m->m_pkthdr.len -= (req_len - len);
        } else {
                /*
                 * Trim from tail.  Scan the mbuf chain,
                 * calculating its length and finding the last mbuf.
                 * If the adjustment only affects this mbuf, then just
                 * adjust and return.  Otherwise, rescan and truncate
                 * after the remaining size.
                 */
                len = -len;
                count = 0;
                for (;;) {
                        count += m->m_len;
                        if (m->m_next == (struct mbuf *)0)
                                break;
                        m = m->m_next;
                }
                if (m->m_len >= len) {
                        m->m_len -= len;
                        m = mp;
                        if (m->m_flags & M_PKTHDR)
                                m->m_pkthdr.len -= len;
                        return;
                }
                count -= len;
                if (count < 0)
                        count = 0;
                /*
                 * Correct length for chain is "count".
                 * Find the mbuf with last data, adjust its length,
                 * and toss data from remaining mbufs on chain.
                 */
                m = mp;
                if (m->m_flags & M_PKTHDR)
                        m->m_pkthdr.len = count;
                for (; m; m = m->m_next) {
                        if (m->m_len >= count) {
                                m->m_len = count;
                                break;
                        }
                        count -= m->m_len;
                }
                while ((m = m->m_next))
                        m->m_len = 0;
        }
}

/*
 * Rearange an mbuf chain so that len bytes are contiguous
 * and in the data area of an mbuf (so that mtod and dtom
 * will work for a structure of size len).  Returns the resulting
 * mbuf chain on success, frees it and returns null on failure.
 * If there is room, it will add up to max_protohdr-len extra bytes to the
 * contiguous region in an attempt to avoid being called next time.
 */
int MPFail;

struct mbuf *
m_pullup(struct mbuf *n, int len)
{
        struct mbuf *m;
        int count;
        int space;

        /*
         * If first mbuf has no cluster, and has room for len bytes
         * without shifting current data, pullup into it,
         * otherwise allocate a new mbuf to prepend to the chain.
         */
        if ((n->m_flags & M_EXT) == 0 &&
            n->m_data + len < &n->m_dat[MLEN] && n->m_next) {
                if (n->m_len >= len)
                        return (n);
                m = n;
                n = n->m_next;
                len -= m->m_len;
        } else {
                if (len > MHLEN)
                        goto bad;
                _MGET(m, M_DONTWAIT, n->m_type);
                if (m == 0)
                        goto bad;
                m->m_len = 0;
                if (n->m_flags & M_PKTHDR) {
                        M_COPY_PKTHDR(m, n);
                        n->m_flags &= ~M_PKTHDR;
                }
        }
        space = &m->m_dat[MLEN] - (m->m_data + m->m_len);
        do {
                count = MIN(MIN(MAX(len, max_protohdr), space), n->m_len);
                bcopy(MTOD(n, caddr_t), MTOD(m, caddr_t) + m->m_len,
                    (unsigned)count);
                len -= count;
                m->m_len += count;
                n->m_len -= count;
                space -= count;
                if (n->m_len)
                        n->m_data += count;
                else
                        n = m_free(n);
        } while (len > 0 && n);
        if (len > 0) {
                (void) m_free(m);
                goto bad;
        }
        m->m_next = n;
        return (m);
bad:
        m_freem(n);
        MPFail++;
        return (0);
}

/*
 * Partition an mbuf chain in two pieces, returning the tail --
 * all but the first len0 bytes.  In case of failure, it returns NULL and
 * attempts to restore the chain to its original state.
 */
struct mbuf *
m_split(struct mbuf *m0, int len0, int wait)
{
        struct mbuf *m, *n;
        unsigned len = len0, remain;

        for (m = m0; m && len > m->m_len; m = m->m_next)
                len -= m->m_len;
        if (m == NULL)
                return (NULL);
        remain = m->m_len - len;
        if (m0->m_flags & M_PKTHDR) {
                _MGETHDR(n, wait, m0->m_type);
                if (n == NULL)
                        return (NULL);
                n->m_pkthdr.rcvif = m0->m_pkthdr.rcvif;
                n->m_pkthdr.len = m0->m_pkthdr.len - len0;
                m0->m_pkthdr.len = len0;
                if (m->m_flags & M_EXT)
                        goto extpacket;
                if (remain > MHLEN) {
                        /* m can't be the lead packet */
                        MH_ALIGN(n, 0);
                        n->m_next = m_split(m, len, wait);
                        if (n->m_next == NULL) {
                                (void) m_free(n);
                                return (NULL);
                        } else
                                return (n);
                } else
                        MH_ALIGN(n, remain);
        } else if (remain == 0) {
                n = m->m_next;
                m->m_next = NULL;
                return (n);
        } else {
                _MGET(n, wait, m->m_type);
                if (n == NULL)
                        return (NULL);
                M_ALIGN(n, remain);
        }
extpacket:
        if (m->m_flags & M_EXT) {
                n->m_flags |= M_EXT;
                n->m_ext = m->m_ext;
                m_incref(m);
                n->m_data = m->m_data + len;
        } else {
                bcopy(MTOD(m, caddr_t) + len, MTOD(n, caddr_t), remain);
        }
        n->m_len = remain;
        m->m_len = len;
        n->m_next = m->m_next;
        m->m_next = NULL;
        return (n);
}

/*
 * Routine to copy from device local memory into mbufs.
 */
struct mbuf *
m_devget(char *buf, int totlen, int off0, struct ifnet *ifp,
    void (*copy)(const void *, void *, size_t))
{
        struct mbuf *m;
        struct mbuf *top = NULL, **mp = &top;
        int off = off0, len;
        char *cp;
        char *epkt;

        cp = buf;
        epkt = cp + totlen;
        if (off) {
                /*
                 * If 'off' is non-zero, packet is trailer-encapsulated,
                 * so we have to skip the type and length fields.
                 */
                cp += off + 2 * sizeof (u_int16_t);
                totlen -= 2 * sizeof (u_int16_t);
        }
        _MGETHDR(m, M_DONTWAIT, MT_DATA);
        if (m == NULL)
                return (NULL);
        m->m_pkthdr.rcvif = ifp;
        m->m_pkthdr.len = totlen;
        m->m_len = MHLEN;

        while (totlen > 0) {
                if (top != NULL) {
                        _MGET(m, M_DONTWAIT, MT_DATA);
                        if (m == NULL) {
                                m_freem(top);
                                return (NULL);
                        }
                        m->m_len = MLEN;
                }
                len = MIN(totlen, epkt - cp);
                if (len >= MINCLSIZE) {
                        MCLGET(m, M_DONTWAIT);
                        if (m->m_flags & M_EXT) {
                                m->m_len = len = MIN(len, m_maxsize(MC_CL));
                        } else {
                                /* give up when it's out of cluster mbufs */
                                if (top != NULL)
                                        m_freem(top);
                                m_freem(m);
                                return (NULL);
                        }
                } else {
                        /*
                         * Place initial small packet/header at end of mbuf.
                         */
                        if (len < m->m_len) {
                                if (top == NULL &&
                                    len + max_linkhdr <= m->m_len)
                                        m->m_data += max_linkhdr;
                                m->m_len = len;
                        } else {
                                len = m->m_len;
                        }
                }
                if (copy)
                        copy(cp, MTOD(m, caddr_t), (unsigned)len);
                else
                        bcopy(cp, MTOD(m, caddr_t), (unsigned)len);
                cp += len;
                *mp = m;
                mp = &m->m_next;
                totlen -= len;
                if (cp == epkt)
                        cp = buf;
        }
        return (top);
}

/*
 * Cluster freelist allocation check.
 */
static int
m_howmany(int num, size_t bufsize)
{
        int i = 0, j = 0;
        u_int32_t m_clusters, m_bigclusters, m_16kclusters;
        u_int32_t m_clfree, m_bigclfree, m_16kclfree;

        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        m_clusters = m_total(MC_CL);
        m_bigclusters = m_total(MC_BIGCL);
        m_16kclusters = m_total(MC_16KCL);
        m_clfree = m_infree(MC_CL);
        m_bigclfree = m_infree(MC_BIGCL);
        m_16kclfree = m_infree(MC_16KCL);

        /* Bail if we've maxed out the mbuf memory map */
        if ((bufsize != m_maxsize(MC_16KCL) &&
            (m_clusters + (m_bigclusters << 1) >= nclusters)) ||
            (njcl > 0 && bufsize == m_maxsize(MC_16KCL) &&
            (m_16kclusters << 3) >= njcl)) {
#if DEBUG
                if (bufsize == MCLBYTES && num > m_clfree) {
                        printf("m_howmany - out of small clusters, "
                            "%d short\n", num - mbstat.m_clfree);
                }
#endif /* DEBUG */
                return (0);
        }

        if (bufsize == m_maxsize(MC_CL)) {
                /* Under minimum */
                if (m_clusters < MINCL)
                        return (MINCL - m_clusters);
                /* Too few (free < 1/16 total) and not over maximum */
                if (m_clusters < m_maxlimit(MC_CL)) {
                        if (m_clfree >= MCL_LOWAT)
                                return (0);
                        if (num >= m_clfree)
                                i = num - m_clfree;
                        if (((m_clusters + num) >> 4) > m_clfree)
                                j = ((m_clusters + num) >> 4) - m_clfree;
                        i = MAX(i, j);
                        if (i + m_clusters >= m_maxlimit(MC_CL))
                                i = m_maxlimit(MC_CL) - m_clusters;
                }
                VERIFY((m_total(MC_CL) + i) <= m_maxlimit(MC_CL));
        } else if (bufsize == m_maxsize(MC_BIGCL)) {
                /* Under minimum */
                if (m_bigclusters < MINBIGCL)
                        return (MINBIGCL - m_bigclusters);
                /* Too few (free < 1/16 total) and not over maximum */
                if (m_bigclusters < m_maxlimit(MC_BIGCL)) {
                        if (m_bigclfree >= MBIGCL_LOWAT)
                                return (0);
                        if (num >= m_bigclfree)
                                i = num - m_bigclfree;
                        if (((m_bigclusters + num) >> 4) > m_bigclfree)
                                j = ((m_bigclusters + num) >> 4) - m_bigclfree;
                        i = MAX(i, j);
                        if (i + m_bigclusters >= m_maxlimit(MC_BIGCL))
                                i = m_maxlimit(MC_BIGCL) - m_bigclusters;
                }
                VERIFY((m_total(MC_BIGCL) + i) <= m_maxlimit(MC_BIGCL));
        } else {
                VERIFY(njcl > 0);
                /* Under minimum */
                if (m_16kclusters < MIN16KCL)
                        return (MIN16KCL - m_16kclusters);
                /* Too few (free < 1/16 total) and not over maximum */
                if (m_16kclusters < m_maxlimit(MC_16KCL)) {
                        if (m_16kclfree >= M16KCL_LOWAT)
                                return (0);
                        if (num >= m_16kclfree)
                                i = num - m_16kclfree;
                        if (((m_16kclusters + num) >> 4) > m_16kclfree)
                                j = ((m_16kclusters + num) >> 4) - m_16kclfree;
                        i = MAX(i, j);
                        if (i + m_16kclusters >= m_maxlimit(MC_16KCL))
                                i = m_maxlimit(MC_16KCL) - m_16kclusters;
                }
                VERIFY((m_total(MC_16KCL) + i) <= m_maxlimit(MC_16KCL));
        }

        return (i);
}

/*
 * Copy data from a buffer back into the indicated mbuf chain,
 * starting "off" bytes from the beginning, extending the mbuf
 * chain if necessary.
 */
void
m_copyback(struct mbuf *m0, int off, int len, caddr_t cp)
{
        int mlen;
        struct mbuf *m = m0, *n;
        int totlen = 0;

        if (m0 == NULL)
                return;
        while (off > (mlen = m->m_len)) {
                off -= mlen;
                totlen += mlen;
                if (m->m_next == NULL) {
                        n = m_getclr(M_DONTWAIT, m->m_type);
                        if (n == NULL)
                                goto out;
                        n->m_len = MIN(MLEN, len + off);
                        m->m_next = n;
                }
                m = m->m_next;
        }
        while (len > 0) {
                mlen = MIN(m->m_len - off, len);
                bcopy(cp, off + MTOD(m, caddr_t), (unsigned)mlen);
                cp += mlen;
                len -= mlen;
                mlen += off;
                off = 0;
                totlen += mlen;
                if (len == 0)
                        break;
                if (m->m_next == NULL) {
                        n = _M_GET(M_DONTWAIT, m->m_type);
                        if (n == NULL)
                                break;
                        n->m_len = MIN(MLEN, len);
                        m->m_next = n;
                }
                m = m->m_next;
        }
out:
        if (((m = m0)->m_flags & M_PKTHDR) && (m->m_pkthdr.len < totlen))
                m->m_pkthdr.len = totlen;
}

char *
mcl_to_paddr(char *addr)
{
        int base_phys;

        if (!MBUF_IN_MAP(addr))
                return (NULL);
        base_phys = mcl_paddr[(addr - (char *)mbutl) >> PGSHIFT];

        if (base_phys == 0)
                return (NULL);
        return ((char *)((int)base_phys | ((int)addr & PGOFSET)));
}

/*
 * Dup the mbuf chain passed in.  The whole thing.  No cute additional cruft.
 * And really copy the thing.  That way, we don't "precompute" checksums
 * for unsuspecting consumers.  Assumption: m->m_nextpkt == 0.  Trick: for
 * small packets, don't dup into a cluster.  That way received  packets
 * don't take up too much room in the sockbuf (cf. sbspace()).
 */
int MDFail;

struct mbuf *
m_dup(struct mbuf *m, int how)
{
        struct mbuf *n, **np;
        struct mbuf *top;
        int copyhdr = 0;

        np = &top;
        top = NULL;
        if (m->m_flags & M_PKTHDR)
                copyhdr = 1;

        /*
         * Quick check: if we have one mbuf and its data fits in an
         *  mbuf with packet header, just copy and go.
         */
        if (m->m_next == NULL) {
                /* Then just move the data into an mbuf and be done... */
                if (copyhdr) {
                        if (m->m_pkthdr.len <= MHLEN && m->m_len <= MHLEN) {
                                if ((n = _M_GETHDR(how, m->m_type)) == NULL)
                                        return (NULL);
                                n->m_len = m->m_len;
                                m_dup_pkthdr(n, m, how);
                                bcopy(m->m_data, n->m_data, m->m_len);
                                return (n);
                        }
                } else if (m->m_len <= MLEN) {
                        if ((n = _M_GET(how, m->m_type)) == NULL)
                                return (NULL);
                        bcopy(m->m_data, n->m_data, m->m_len);
                        n->m_len = m->m_len;
                        return (n);
                }
        }
        while (m != NULL) {
#if BLUE_DEBUG
                kprintf("<%x: %x, %x, %x\n", m, m->m_flags, m->m_len,
                    m->m_data);
#endif
                if (copyhdr)
                        n = _M_GETHDR(how, m->m_type);
                else
                        n = _M_GET(how, m->m_type);
                if (n == NULL)
                        goto nospace;
                if (m->m_flags & M_EXT) {
                        if (m->m_len <= m_maxsize(MC_CL))
                                MCLGET(n, how);
                        else if (m->m_len <= m_maxsize(MC_BIGCL))
                                n = m_mbigget(n, how);
                        else if (m->m_len <= m_maxsize(MC_16KCL) && njcl > 0)
                                n = m_m16kget(n, how);
                        if (!(n->m_flags & M_EXT)) {
                                (void) m_free(n);
                                goto nospace;
                        }
                }
                *np = n;
                if (copyhdr) {
                        /* Don't use M_COPY_PKTHDR: preserve m_data */
                        m_dup_pkthdr(n, m, how);
                        copyhdr = 0;
                        if (!(n->m_flags & M_EXT))
                                n->m_data = n->m_pktdat;
                }
                n->m_len = m->m_len;
                /*
                 * Get the dup on the same bdry as the original
                 * Assume that the two mbufs have the same offset to data area
                 * (up to word boundaries)
                 */
                bcopy(MTOD(m, caddr_t), MTOD(n, caddr_t), (unsigned)n->m_len);
                m = m->m_next;
                np = &n->m_next;
#if BLUE_DEBUG
                kprintf(">%x: %x, %x, %x\n", n, n->m_flags, n->m_len,
                    n->m_data);
#endif
        }

        if (top == NULL)
                MDFail++;
        return (top);

nospace:
        m_freem(top);
        MDFail++;
        return (NULL);
}

#define MBUF_MULTIPAGES(m)                                              \
        (((m)->m_flags & M_EXT) &&                                      \
        ((IS_P2ALIGNED((m)->m_data, NBPG) && (m)->m_len > NBPG) ||      \
        (!IS_P2ALIGNED((m)->m_data, NBPG) &&                            \
        P2ROUNDUP((m)->m_data, NBPG) < ((uintptr_t)(m)->m_data + (m)->m_len))))

static struct mbuf *
m_expand(struct mbuf *m, struct mbuf **last)
{
        struct mbuf *top = NULL;
        struct mbuf **nm = &top;
        uintptr_t data0, data;
        unsigned int len0, len;

        VERIFY(MBUF_MULTIPAGES(m));
        VERIFY(m->m_next == NULL);
        data0 = (uintptr_t)m->m_data;
        len0 = m->m_len;
        *last = top;

        for (;;) {
                struct mbuf *n;

                data = data0;
                if (IS_P2ALIGNED(data, NBPG) && len0 > NBPG)
                        len = NBPG;
                else if (!IS_P2ALIGNED(data, NBPG) &&
                    P2ROUNDUP(data, NBPG) < (data + len0))
                        len = P2ROUNDUP(data, NBPG) - data;
                else
                        len = len0;

                VERIFY(len > 0);
                VERIFY(m->m_flags & M_EXT);
                m->m_data = (void *)data;
                m->m_len = len;

                *nm = *last = m;
                nm = &m->m_next;
                m->m_next = NULL;

                data0 += len;
                len0 -= len;
                if (len0 == 0)
                        break;

                n = _M_RETRY(M_DONTWAIT, MT_DATA);
                if (n == NULL) {
                        m_freem(top);
                        top = *last = NULL;
                        break;
                }

                n->m_ext = m->m_ext;
                m_incref(m);
                n->m_flags |= M_EXT;
                m = n;
        }
        return (top);
}

struct mbuf *
m_normalize(struct mbuf *m)
{
        struct mbuf *top = NULL;
        struct mbuf **nm = &top;
        boolean_t expanded = FALSE;

        while (m != NULL) {
                struct mbuf *n;

                n = m->m_next;
                m->m_next = NULL;

                /* Does the data cross one or more page boundaries? */
                if (MBUF_MULTIPAGES(m)) {
                        struct mbuf *last;
                        if ((m = m_expand(m, &last)) == NULL) {
                                m_freem(n);
                                m_freem(top);
                                top = NULL;
                                break;
                        }
                        *nm = m;
                        nm = &last->m_next;
                        expanded = TRUE;
                } else {
                        *nm = m;
                        nm = &m->m_next;
                }
                m = n;
        }
        if (expanded)
                atomic_add_32(&mb_normalized, 1);
        return (top);
}

void
m_mchtype(struct mbuf *m, int t)
{
        mtype_stat_inc(t);
        mtype_stat_dec(m->m_type);
        (m)->m_type = t;
}

void *
m_mtod(struct mbuf *m)
{
        return (MTOD(m, void *));
}

struct mbuf *
m_dtom(void *x)
{
        return ((struct mbuf *)((u_long)(x) & ~(MSIZE-1)));
}

void
m_mcheck(struct mbuf *m)
{
        _MCHECK(m);
}

/*
 * Inform the corresponding mcache(s) that there's a waiter below.
 */
static void
mbuf_waiter_inc(mbuf_class_t class, boolean_t comp)
{
        mcache_waiter_inc(m_cache(class));
        if (comp) {
                if (class == MC_CL) {
                        mcache_waiter_inc(m_cache(MC_MBUF_CL));
                } else if (class == MC_BIGCL) {
                        mcache_waiter_inc(m_cache(MC_MBUF_BIGCL));
                } else if (class == MC_16KCL) {
                        mcache_waiter_inc(m_cache(MC_MBUF_16KCL));
                } else {
                        mcache_waiter_inc(m_cache(MC_MBUF_CL));
                        mcache_waiter_inc(m_cache(MC_MBUF_BIGCL));
                }
        }
}

/*
 * Inform the corresponding mcache(s) that there's no more waiter below.
 */
static void
mbuf_waiter_dec(mbuf_class_t class, boolean_t comp)
{
        mcache_waiter_dec(m_cache(class));
        if (comp) {
                if (class == MC_CL) {
                        mcache_waiter_dec(m_cache(MC_MBUF_CL));
                } else if (class == MC_BIGCL) {
                        mcache_waiter_dec(m_cache(MC_MBUF_BIGCL));
                } else if (class == MC_16KCL) {
                        mcache_waiter_dec(m_cache(MC_MBUF_16KCL));
                } else {
                        mcache_waiter_dec(m_cache(MC_MBUF_CL));
                        mcache_waiter_dec(m_cache(MC_MBUF_BIGCL));
                }
        }
}

/*
 * Called during blocking allocation.  Returns TRUE if one or more objects
 * are available at the per-CPU caches layer and that allocation should be
 * retried at that level.
 */
static boolean_t
mbuf_sleep(mbuf_class_t class, unsigned int num, int wait)
{
        boolean_t mcache_retry = FALSE;

        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        /* Check if there's anything at the cache layer */
        if (mbuf_cached_above(class, wait)) {
                mcache_retry = TRUE;
                goto done;
        }

        /* Nothing?  Then try hard to get it from somewhere */
        m_reclaim(class, num, (wait & MCR_COMP));

        /* We tried hard and got something? */
        if (m_infree(class) > 0) {
                mbstat.m_wait++;
                goto done;
        } else if (mbuf_cached_above(class, wait)) {
                mbstat.m_wait++;
                mcache_retry = TRUE;
                goto done;
        } else if (wait & MCR_TRYHARD) {
                mcache_retry = TRUE;
                goto done;
        }

        /*
         * There's really nothing for us right now; inform the
         * cache(s) that there is a waiter below and go to sleep.
         */
        mbuf_waiter_inc(class, (wait & MCR_COMP));

        VERIFY(!(wait & MCR_NOSLEEP));
        mb_waiters++;
        (void) msleep(mb_waitchan, mbuf_mlock, (PZERO-1), m_cname(class), NULL);

        /* We are now up; stop getting notified until next round */
        mbuf_waiter_dec(class, (wait & MCR_COMP));

        /* We waited and got something */
        if (m_infree(class) > 0) {
                mbstat.m_wait++;
                goto done;
        } else if (mbuf_cached_above(class, wait)) {
                mbstat.m_wait++;
                mcache_retry = TRUE;
        }
done:
        return (mcache_retry);
}

static void
mbuf_worker_thread(void)
{
        int mbuf_expand;

        while (1) {
                lck_mtx_lock(mbuf_mlock);

                mbuf_expand = 0;
                if (mbuf_expand_mcl) {
                        int n;

                        /* Adjust to current number of cluster in use */
                        n = mbuf_expand_mcl -
                            (m_total(MC_CL) - m_infree(MC_CL));
                        if ((n + m_total(MC_CL)) > m_maxlimit(MC_CL))
                                n = m_maxlimit(MC_CL) - m_total(MC_CL);
                        mbuf_expand_mcl = 0;

                        if (n > 0 && freelist_populate(MC_CL, n, M_WAIT) > 0)
                                mbuf_expand++;
                }
                if (mbuf_expand_big) {
                        int n;

                        /* Adjust to current number of 4 KB cluster in use */
                        n = mbuf_expand_big -
                            (m_total(MC_BIGCL) - m_infree(MC_BIGCL));
                        if ((n + m_total(MC_BIGCL)) > m_maxlimit(MC_BIGCL))
                                n = m_maxlimit(MC_BIGCL) - m_total(MC_BIGCL);
                        mbuf_expand_big = 0;

                        if (n > 0 && freelist_populate(MC_BIGCL, n, M_WAIT) > 0)
                                mbuf_expand++;
                }
                if (mbuf_expand_16k) {
                        int n;

                        /* Adjust to current number of 16 KB cluster in use */
                        n = mbuf_expand_16k -
                            (m_total(MC_16KCL) - m_infree(MC_16KCL));
                        if ((n + m_total(MC_16KCL)) > m_maxlimit(MC_16KCL))
                                n = m_maxlimit(MC_16KCL) - m_total(MC_16KCL);
                        mbuf_expand_16k = 0;

                        if (n > 0)
                                (void) freelist_populate(MC_16KCL, n, M_WAIT);
                }

                /*
                 * Because we can run out of memory before filling the mbuf
                 * map, we should not allocate more clusters than they are
                 * mbufs -- otherwise we could have a large number of useless
                 * clusters allocated.
                 */
                if (mbuf_expand) {
                        while (m_total(MC_MBUF) <
                            (m_total(MC_BIGCL) + m_total(MC_CL))) {
                                if (freelist_populate(MC_MBUF, 1, M_WAIT) == 0)
                                        break;
                        }
                }

                lck_mtx_unlock(mbuf_mlock);

                assert_wait(&mbuf_worker_run, THREAD_UNINT);
                (void) thread_block((thread_continue_t)mbuf_worker_thread);
        }
}

static void
mbuf_worker_thread_init(void)
{
        mbuf_worker_ready++;
        mbuf_worker_thread();
}

static mcl_slab_t *
slab_get(void *buf)
{
        mcl_slabg_t *slg;
        unsigned int ix, k;

        lck_mtx_assert(mbuf_mlock, LCK_MTX_ASSERT_OWNED);

        VERIFY(MBUF_IN_MAP(buf));
        ix = ((char *)buf - (char *)mbutl) >> MBSHIFT;
        VERIFY(ix < maxslabgrp);

        if ((slg = slabstbl[ix]) == NULL) {
                /*
                 * In the current implementation, we never shrink the memory
                 * pool (hence the cluster map); if we attempt to reallocate
                 * a cluster group when it's already allocated, panic since
                 * this is a sign of a memory corruption (slabstbl[ix] got
                 * nullified).  This also means that there shouldn't be any
                 * hole in the kernel sub-map for the mbuf pool.
                 */
                ++slabgrp;
                VERIFY(ix < slabgrp);
                /*
                 * Slabs expansion can only be done single threaded; when
                 * we get here, it must be as a result of m_clalloc() which
                 * is serialized and therefore mb_clalloc_busy must be set.
                 */
                VERIFY(mb_clalloc_busy);
                lck_mtx_unlock(mbuf_mlock);

                /* This is a new buffer; create the slabs group for it */
                MALLOC(slg, mcl_slabg_t *, sizeof (*slg), M_TEMP,
                    M_WAITOK | M_ZERO);
                VERIFY(slg != NULL);

                lck_mtx_lock(mbuf_mlock);
                /*
                 * No other thread could have gone into m_clalloc() after
                 * we dropped the lock above, so verify that it's true.
                 */
                VERIFY(mb_clalloc_busy);

                slabstbl[ix] = slg;

                /* Chain each slab in the group to its forward neighbor */
                for (k = 1; k < NSLABSPMB; k++)
                        slg->slg_slab[k - 1].sl_next = &slg->slg_slab[k];
                VERIFY(slg->slg_slab[NSLABSPMB - 1].sl_next == NULL);

                /* And chain the last slab in the previous group to this */
                if (ix > 0) {
                        VERIFY(slabstbl[ix - 1]->
                            slg_slab[NSLABSPMB - 1].sl_next == NULL);
                        slabstbl[ix - 1]->slg_slab[NSLABSPMB - 1].sl_next =
                            &slg->slg_slab[0];
                }
        }

        ix = MTOCL(buf) % NSLABSPMB;
        VERIFY(ix < NSLABSPMB);

        return (&slg->slg_slab[ix]);
}

static void
slab_init(mcl_slab_t *sp, mbuf_class_t class, u_int32_t flags,
    void *base, void *head, unsigned int len, int refcnt, int chunks)
{
        sp->sl_class = class;
        sp->sl_flags = flags;
        sp->sl_base = base;
        sp->sl_head = head;
        sp->sl_len = len;
        sp->sl_refcnt = refcnt;
        sp->sl_chunks = chunks;
        slab_detach(sp);
}

static void
slab_insert(mcl_slab_t *sp, mbuf_class_t class)
{
        VERIFY(slab_is_detached(sp));
        m_slab_cnt(class)++;
        TAILQ_INSERT_TAIL(&m_slablist(class), sp, sl_link);
        sp->sl_flags &= ~SLF_DETACHED;
        if (class == MC_BIGCL) {
                sp = sp->sl_next;
                /* Next slab must already be present */
                VERIFY(sp != NULL);
                VERIFY(slab_is_detached(sp));
                sp->sl_flags &= ~SLF_DETACHED;
        } else if (class == MC_16KCL) {
                int k;
                for (k = 1; k < (M16KCLBYTES / MCLBYTES); k++) {
                        sp = sp->sl_next;
                        /* Next slab must already be present */
                        VERIFY(sp != NULL);
                        VERIFY(slab_is_detached(sp));
                        sp->sl_flags &= ~SLF_DETACHED;
                }
        }
}

static void
slab_remove(mcl_slab_t *sp, mbuf_class_t class)
{
        VERIFY(!slab_is_detached(sp));
        VERIFY(m_slab_cnt(class) > 0);
        m_slab_cnt(class)--;
        TAILQ_REMOVE(&m_slablist(class), sp, sl_link);
        slab_detach(sp);
        if (class == MC_BIGCL) {
                sp = sp->sl_next;
                /* Next slab must already be present */
                VERIFY(sp != NULL);
                VERIFY(!slab_is_detached(sp));
                slab_detach(sp);
        } else if (class == MC_16KCL) {
                int k;
                for (k = 1; k < (M16KCLBYTES / MCLBYTES); k++) {
                        sp = sp->sl_next;
                        /* Next slab must already be present */
                        VERIFY(sp != NULL);
                        VERIFY(!slab_is_detached(sp));
                        slab_detach(sp);
                }
        }
}

static boolean_t
slab_inrange(mcl_slab_t *sp, void *buf)
{
        return ((uintptr_t)buf >= (uintptr_t)sp->sl_base &&
            (uintptr_t)buf < ((uintptr_t)sp->sl_base + sp->sl_len));
}

#undef panic(...)

static void
slab_nextptr_panic(mcl_slab_t *sp, void *addr)
{
        int i;
        unsigned int chunk_len = sp->sl_len / sp->sl_chunks;
        uintptr_t buf = (uintptr_t)sp->sl_base;

        for (i = 0; i < sp->sl_chunks; i++, buf += chunk_len) {
                void *next = ((mcache_obj_t *)buf)->obj_next;
                if (next != addr)
                        continue;
                if (mclaudit == NULL) {
                        if (next != NULL && !MBUF_IN_MAP(next)) {
                                mcache_t *cp = m_cache(sp->sl_class);
                                panic("%s: %s buffer %p in slab %p modified "
                                    "after free at offset 0: %p out of range "
                                    "[%p-%p)\n", __func__, cp->mc_name,
                                    (void *)buf, sp, next, mbutl, embutl);
                                /* NOTREACHED */
                        }
                } else {
                        mcache_audit_t *mca = mcl_audit_buf2mca(sp->sl_class,
                            (mcache_obj_t *)buf);
                        mcl_audit_verify_nextptr(next, mca);
                }
        }
}

static void
slab_detach(mcl_slab_t *sp)
{
        sp->sl_link.tqe_next = (mcl_slab_t *)-1;
        sp->sl_link.tqe_prev = (mcl_slab_t **)-1;
        sp->sl_flags |= SLF_DETACHED;
}

static boolean_t
slab_is_detached(mcl_slab_t *sp)
{
        return ((intptr_t)sp->sl_link.tqe_next == -1 &&
            (intptr_t)sp->sl_link.tqe_prev == -1 &&
            (sp->sl_flags & SLF_DETACHED));
}

static void
mcl_audit_init(void *buf, mcache_audit_t **mca_list,
    mcache_obj_t **con_list, size_t con_size, unsigned int num)
{
        mcache_audit_t *mca, *mca_tail;
        mcache_obj_t *con = NULL;
        boolean_t save_contents = (con_list != NULL);
        unsigned int i, ix;

        ASSERT(num <= NMBPCL);
        ASSERT(con_list == NULL || con_size != 0);

        ix = MTOCL(buf);
        /* Make sure we haven't been here before */
        for (i = 0; i < NMBPCL; i++)
                VERIFY(mclaudit[ix].cl_audit[i] == NULL);

        mca = mca_tail = *mca_list;
        if (save_contents)
                con = *con_list;

        for (i = 0; i < num; i++) {
                mcache_audit_t *next;

                next = mca->mca_next;
                bzero(mca, sizeof (*mca));
                mca->mca_next = next;
                mclaudit[ix].cl_audit[i] = mca;

                /* Attach the contents buffer if requested */
                if (save_contents) {
                        VERIFY(con != NULL);
                        mca->mca_contents_size = con_size;
                        mca->mca_contents = con;
                        con = con->obj_next;
                        bzero(mca->mca_contents, mca->mca_contents_size);
                }

                mca_tail = mca;
                mca = mca->mca_next;
        }

        if (save_contents)
                *con_list = con;

        *mca_list = mca_tail->mca_next;
        mca_tail->mca_next = NULL;
}

/*
 * Given an address of a buffer (mbuf/cluster/big cluster), return
 * the corresponding audit structure for that buffer.
 */
static mcache_audit_t *
mcl_audit_buf2mca(mbuf_class_t class, mcache_obj_t *o)
{
        mcache_audit_t *mca = NULL;
        int ix = MTOCL(o);

        VERIFY(IS_P2ALIGNED(o, MIN(m_maxsize(class), NBPG)));

        switch (class) {
        case MC_MBUF:
                /*
                 * For the mbuf case, find the index of the cluster
                 * used by the mbuf and use that index to locate the
                 * base address of the cluster.  Then find out the
                 * mbuf index relative to the cluster base and use
                 * it to locate the audit structure.
                 */
                VERIFY(MCLIDX(CLTOM(ix), o) < (int)NMBPCL);
                mca = mclaudit[ix].cl_audit[MCLIDX(CLTOM(ix), o)];
                break;

        case MC_CL:
        case MC_BIGCL:
        case MC_16KCL:
                /*
                 * Same as above, but only return the first element.
                 */
                mca = mclaudit[ix].cl_audit[0];
                break;

        default:
                VERIFY(0);
                /* NOTREACHED */
        }

        return (mca);
}

static void
mcl_audit_mbuf(mcache_audit_t *mca, void *addr, boolean_t composite,
    boolean_t alloc)
{
        struct mbuf *m = addr;
        mcache_obj_t *next = ((mcache_obj_t *)m)->obj_next;

        VERIFY(mca->mca_contents != NULL &&
            mca->mca_contents_size == AUDIT_CONTENTS_SIZE);

        mcl_audit_verify_nextptr(next, mca);

        if (!alloc) {
                /* Save constructed mbuf fields */
                mcl_audit_save_mbuf(m, mca);
                mcache_set_pattern(MCACHE_FREE_PATTERN, m, m_maxsize(MC_MBUF));
                ((mcache_obj_t *)m)->obj_next = next;
                return;
        }

        /* Check if the buffer has been corrupted while in freelist */
        mcache_audit_free_verify_set(mca, addr, 0, m_maxsize(MC_MBUF));

        /* Restore constructed mbuf fields */
        mcl_audit_restore_mbuf(m, mca, composite);
}

static void
mcl_audit_restore_mbuf(struct mbuf *m, mcache_audit_t *mca, boolean_t composite)
{
        struct mbuf *ms = (struct mbuf *)mca->mca_contents;

        if (composite) {
                struct mbuf *next = m->m_next;
                VERIFY(ms->m_flags == M_EXT && MEXT_RFA(ms) != NULL &&
                    MBUF_IS_COMPOSITE(ms));
                /*
                 * We could have hand-picked the mbuf fields and restore
                 * them individually, but that will be a maintenance
                 * headache.  Instead, restore everything that was saved;
                 * the mbuf layer will recheck and reinitialize anyway.
                 */
                bcopy(ms, m, mca->mca_contents_size);
                m->m_next = next;
        } else {
                /*
                 * For a regular mbuf (no cluster attached) there's nothing
                 * to restore other than the type field, which is expected
                 * to be MT_FREE.
                 */
                m->m_type = ms->m_type;
        }
        _MCHECK(m);
}

static void
mcl_audit_save_mbuf(struct mbuf *m, mcache_audit_t *mca)
{
        _MCHECK(m);
        bcopy(m, mca->mca_contents, mca->mca_contents_size);
}

static void
mcl_audit_cluster(mcache_audit_t *mca, void *addr, size_t size, boolean_t alloc,
    boolean_t save_next)
{
        mcache_obj_t *next = ((mcache_obj_t *)addr)->obj_next;

        if (!alloc) {
                mcache_set_pattern(MCACHE_FREE_PATTERN, addr, size);
                if (save_next) {
                        mcl_audit_verify_nextptr(next, mca);
                        ((mcache_obj_t *)addr)->obj_next = next;
                }
        } else {
                /* Check if the buffer has been corrupted while in freelist */
                mcl_audit_verify_nextptr(next, mca);
                mcache_audit_free_verify_set(mca, addr, 0, size);
        }
}

static void
mcl_audit_mcheck_panic(struct mbuf *m)
{
        mcache_audit_t *mca;

        MRANGE(m);
        mca = mcl_audit_buf2mca(MC_MBUF, (mcache_obj_t *)m);

        panic("mcl_audit: freed mbuf %p with type 0x%x (instead of 0x%x)\n%s\n",
            m, (u_int16_t)m->m_type, MT_FREE, mcache_dump_mca(mca));
        /* NOTREACHED */
}

static void
mcl_audit_verify_nextptr(void *next, mcache_audit_t *mca)
{
        if (next != NULL && next != (void *)MCACHE_FREE_PATTERN &&
            !MBUF_IN_MAP(next)) {
                panic("mcl_audit: buffer %p modified after free at offset 0: "
                    "%p out of range [%p-%p)\n%s\n",
                    mca->mca_addr, next, mbutl, embutl, mcache_dump_mca(mca));
                /* NOTREACHED */
        }
}

SYSCTL_DECL(_kern_ipc);
SYSCTL_PROC(_kern_ipc, KIPC_MBSTAT, mbstat, CTLFLAG_RD | CTLFLAG_LOCKED,
    0, 0, mbstat_sysctl, "S,mbstat", "");
SYSCTL_PROC(_kern_ipc, OID_AUTO, mb_stat, CTLFLAG_RD | CTLFLAG_LOCKED,
    0, 0, mb_stat_sysctl, "S,mb_stat", "");
SYSCTL_INT(_kern_ipc, OID_AUTO, mb_normalized, CTLFLAG_RD | CTLFLAG_LOCKED,
    &mb_normalized, 0, "");