xnu-3248.60.10.tar.gz

[apple/xnu.git] / osfmk / vm / vm_compressor_pager.c

/*
 * Copyright (c) 2013 Apple Computer, 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,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */

/*
 *      Compressor Pager.
 *              Memory Object Management.
 */

#include <kern/host_statistics.h>
#include <kern/kalloc.h>

#include <mach/memory_object_control.h>
#include <mach/memory_object_types.h>
#include <mach/memory_object_server.h>
#include <mach/upl.h>

#include <vm/memory_object.h>
#include <vm/vm_compressor_pager.h>
#include <vm/vm_external.h>
#include <vm/vm_pageout.h>
#include <vm/vm_protos.h>

/* memory_object interfaces */
void compressor_memory_object_reference(memory_object_t mem_obj);
void compressor_memory_object_deallocate(memory_object_t mem_obj);
kern_return_t compressor_memory_object_init(
        memory_object_t         mem_obj,
        memory_object_control_t control,
        memory_object_cluster_size_t pager_page_size);
kern_return_t compressor_memory_object_terminate(memory_object_t mem_obj);
kern_return_t compressor_memory_object_data_request(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        memory_object_cluster_size_t            length,
        __unused vm_prot_t      protection_required,
        memory_object_fault_info_t      fault_info);
kern_return_t compressor_memory_object_data_return(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        memory_object_cluster_size_t                    size,
        __unused memory_object_offset_t *resid_offset,
        __unused int            *io_error,
        __unused boolean_t      dirty,
        __unused boolean_t      kernel_copy,
        __unused int    upl_flags);
kern_return_t compressor_memory_object_data_initialize(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        memory_object_cluster_size_t            size);
kern_return_t compressor_memory_object_data_unlock(
        __unused memory_object_t                mem_obj,
        __unused memory_object_offset_t offset,
        __unused memory_object_size_t           size,
        __unused vm_prot_t              desired_access);
kern_return_t compressor_memory_object_synchronize(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        memory_object_size_t            length,
        __unused vm_sync_t              flags);
kern_return_t compressor_memory_object_map(
        __unused memory_object_t        mem_obj,
        __unused vm_prot_t              prot);
kern_return_t compressor_memory_object_last_unmap(memory_object_t mem_obj);
kern_return_t compressor_memory_object_data_reclaim(
        __unused memory_object_t        mem_obj,
        __unused boolean_t              reclaim_backing_store);

const struct memory_object_pager_ops compressor_pager_ops = {
        compressor_memory_object_reference,
        compressor_memory_object_deallocate,
        compressor_memory_object_init,
        compressor_memory_object_terminate,
        compressor_memory_object_data_request,
        compressor_memory_object_data_return,
        compressor_memory_object_data_initialize,
        compressor_memory_object_data_unlock,
        compressor_memory_object_synchronize,
        compressor_memory_object_map,
        compressor_memory_object_last_unmap,
        compressor_memory_object_data_reclaim,
        "compressor pager"
};

/* internal data structures */

struct {
        uint64_t        data_returns;
        uint64_t        data_requests;
        uint64_t        put;
        uint64_t        get;
        uint64_t        state_clr;
        uint64_t        state_get;
        uint64_t        transfer;
} compressor_pager_stats;

typedef int compressor_slot_t;

typedef struct compressor_pager {
        struct ipc_object_header        cpgr_pager_header; /* fake ip_kotype */
        memory_object_pager_ops_t       cpgr_pager_ops; /* == &compressor_pager_ops */
        memory_object_control_t         cpgr_control;
        lck_mtx_t                       cpgr_lock;

        unsigned int                    cpgr_references;
        unsigned int                    cpgr_num_slots;
        unsigned int                    cpgr_num_slots_occupied;
        union {
                compressor_slot_t       cpgr_eslots[2]; /* embedded slots */
                compressor_slot_t       *cpgr_dslots;   /* direct slots */
                compressor_slot_t       **cpgr_islots;  /* indirect slots */
        } cpgr_slots;
} *compressor_pager_t;

#define compressor_pager_lookup(_mem_obj_, _cpgr_)                      \
        MACRO_BEGIN                                                     \
        if (_mem_obj_ == NULL ||                                        \
            _mem_obj_->mo_pager_ops != &compressor_pager_ops) {         \
                _cpgr_ = NULL;                                          \
        } else {                                                        \
                _cpgr_ = (compressor_pager_t) _mem_obj_;                \
        }                                                               \
        MACRO_END

zone_t compressor_pager_zone;

lck_grp_t       compressor_pager_lck_grp;
lck_grp_attr_t  compressor_pager_lck_grp_attr;
lck_attr_t      compressor_pager_lck_attr;

#define compressor_pager_lock(_cpgr_) \
        lck_mtx_lock(&(_cpgr_)->cpgr_lock)
#define compressor_pager_unlock(_cpgr_) \
        lck_mtx_unlock(&(_cpgr_)->cpgr_lock)
#define compressor_pager_lock_init(_cpgr_) \
        lck_mtx_init(&(_cpgr_)->cpgr_lock, &compressor_pager_lck_grp, &compressor_pager_lck_attr)
#define compressor_pager_lock_destroy(_cpgr_) \
        lck_mtx_destroy(&(_cpgr_)->cpgr_lock, &compressor_pager_lck_grp)

#define COMPRESSOR_SLOTS_CHUNK_SIZE     (512)
#define COMPRESSOR_SLOTS_PER_CHUNK      (COMPRESSOR_SLOTS_CHUNK_SIZE / sizeof (compressor_slot_t))

/* forward declarations */
unsigned int compressor_pager_slots_chunk_free(compressor_slot_t *chunk,
                                               int num_slots,
                                               int flags,
                                               int *failures);
void compressor_pager_slot_lookup(
        compressor_pager_t      pager,
        boolean_t               do_alloc,
        memory_object_offset_t  offset,
        compressor_slot_t       **slot_pp);

kern_return_t
compressor_memory_object_init(
        memory_object_t         mem_obj,
        memory_object_control_t control,
        __unused memory_object_cluster_size_t pager_page_size)
{
        compressor_pager_t              pager;

        assert(pager_page_size == PAGE_SIZE);

        memory_object_control_reference(control);

        compressor_pager_lookup(mem_obj, pager);
        compressor_pager_lock(pager);

        if (pager->cpgr_control != MEMORY_OBJECT_CONTROL_NULL)
                panic("compressor_memory_object_init: bad request");
        pager->cpgr_control = control;

        compressor_pager_unlock(pager);

        return KERN_SUCCESS;
}

kern_return_t
compressor_memory_object_synchronize(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        memory_object_size_t            length,
        __unused vm_sync_t              flags)
{
        compressor_pager_t      pager;

        compressor_pager_lookup(mem_obj, pager);

        memory_object_synchronize_completed(pager->cpgr_control, offset, length);

        return KERN_SUCCESS;
}

kern_return_t
compressor_memory_object_map(
        __unused memory_object_t        mem_obj,
        __unused vm_prot_t              prot)
{
        panic("compressor_memory_object_map");
        return KERN_FAILURE;
}

kern_return_t
compressor_memory_object_last_unmap(
        __unused memory_object_t        mem_obj)
{
        panic("compressor_memory_object_last_unmap");
        return KERN_FAILURE;
}

kern_return_t
compressor_memory_object_data_reclaim(
        __unused memory_object_t        mem_obj,
        __unused boolean_t              reclaim_backing_store)
{
        panic("compressor_memory_object_data_reclaim");
        return KERN_FAILURE;
}

kern_return_t
compressor_memory_object_terminate(
        memory_object_t         mem_obj)
{
        memory_object_control_t control;
        compressor_pager_t      pager;

        /* 
         * control port is a receive right, not a send right.
         */

        compressor_pager_lookup(mem_obj, pager);
        compressor_pager_lock(pager);

        /*
         * After memory_object_terminate both memory_object_init
         * and a no-senders notification are possible, so we need
         * to clean up our reference to the memory_object_control
         * to prepare for a new init.
         */

        control = pager->cpgr_control;
        pager->cpgr_control = MEMORY_OBJECT_CONTROL_NULL;

        compressor_pager_unlock(pager);

        /*
         * Now we deallocate our reference on the control.
         */
        memory_object_control_deallocate(control);
        return KERN_SUCCESS;
}

void
compressor_memory_object_reference(
        memory_object_t         mem_obj)
{
        compressor_pager_t      pager;

        compressor_pager_lookup(mem_obj, pager);
        if (pager == NULL)
                return;

        compressor_pager_lock(pager);
        assert(pager->cpgr_references > 0);
        pager->cpgr_references++;
        compressor_pager_unlock(pager);
}

void
compressor_memory_object_deallocate(
        memory_object_t         mem_obj)
{
        compressor_pager_t      pager;
        unsigned int            num_slots_freed;

        /*
         * Because we don't give out multiple first references
         * for a memory object, there can't be a race
         * between getting a deallocate call and creating
         * a new reference for the object.
         */

        compressor_pager_lookup(mem_obj, pager);
        if (pager == NULL)
                return;

        compressor_pager_lock(pager);
        if (--pager->cpgr_references > 0) {
                compressor_pager_unlock(pager);
                return;
        }

        /*
         * We shouldn't get a deallocation call
         * when the kernel has the object cached.
         */
        if (pager->cpgr_control != MEMORY_OBJECT_CONTROL_NULL)
                panic("compressor_memory_object_deallocate(): bad request");

        /*
         * Unlock the pager (though there should be no one
         * waiting for it).
         */
        compressor_pager_unlock(pager);

        /* free the compressor slots */
        int num_chunks;
        int i;
        compressor_slot_t *chunk;

        num_chunks = (pager->cpgr_num_slots + COMPRESSOR_SLOTS_PER_CHUNK -1) / COMPRESSOR_SLOTS_PER_CHUNK;
        if (num_chunks > 1) {
                /* we have an array of chunks */
                for (i = 0; i < num_chunks; i++) {
                        chunk = pager->cpgr_slots.cpgr_islots[i];
                        if (chunk != NULL) {
                                num_slots_freed =
                                        compressor_pager_slots_chunk_free(
                                                chunk,
                                                COMPRESSOR_SLOTS_PER_CHUNK,
                                                0,
                                                NULL);
                                pager->cpgr_slots.cpgr_islots[i] = NULL;
                                kfree(chunk, COMPRESSOR_SLOTS_CHUNK_SIZE);
                        }
                }
                kfree(pager->cpgr_slots.cpgr_islots,
                      num_chunks * sizeof (pager->cpgr_slots.cpgr_islots[0]));
                pager->cpgr_slots.cpgr_islots = NULL;
        } else if (pager->cpgr_num_slots > 2) {
                chunk = pager->cpgr_slots.cpgr_dslots;
                num_slots_freed =
                        compressor_pager_slots_chunk_free(
                                chunk,
                                pager->cpgr_num_slots,
                                0,
                                NULL);
                pager->cpgr_slots.cpgr_dslots = NULL;
                kfree(chunk,
                      (pager->cpgr_num_slots *
                       sizeof (pager->cpgr_slots.cpgr_dslots[0])));
        } else {
                chunk = &pager->cpgr_slots.cpgr_eslots[0];
                num_slots_freed =
                        compressor_pager_slots_chunk_free(
                                chunk,
                                pager->cpgr_num_slots,
                                0,
                                NULL);
        }

        compressor_pager_lock_destroy(pager);
        zfree(compressor_pager_zone, pager);
}

kern_return_t
compressor_memory_object_data_request(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        memory_object_cluster_size_t            length,
        __unused vm_prot_t      protection_required,
        __unused memory_object_fault_info_t     fault_info)
{
        compressor_pager_t      pager;
        kern_return_t           kr;
        compressor_slot_t       *slot_p;
        
        compressor_pager_stats.data_requests++;

        /*
         * Request must be on a page boundary and a multiple of pages.
         */
        if ((offset & PAGE_MASK) != 0 || (length & PAGE_MASK) != 0)
                panic("compressor_memory_object_data_request(): bad alignment");

        if ((uint32_t)(offset/PAGE_SIZE) != (offset/PAGE_SIZE)) {
                panic("%s: offset 0x%llx overflow\n",
                      __FUNCTION__, (uint64_t) offset);
                return KERN_FAILURE;
        }

        compressor_pager_lookup(mem_obj, pager);

        if (length == 0) {
                /* we're only querying the pager for this page */
        } else {
                panic("compressor: data_request");
        }

        /* find the compressor slot for that page */
        compressor_pager_slot_lookup(pager, FALSE, offset, &slot_p);

        if (offset / PAGE_SIZE > pager->cpgr_num_slots) {
                /* out of range */
                kr = KERN_FAILURE;
        } else if (slot_p == NULL || *slot_p == 0) {
                /* compressor does not have this page */
                kr = KERN_FAILURE;
        } else {
                /* compressor does have this page */
                kr = KERN_SUCCESS;
        }
        return kr;
}

/*
 * memory_object_data_initialize: check whether we already have each page, and
 * write it if we do not.  The implementation is far from optimized, and
 * also assumes that the default_pager is single-threaded.
 */
/*  It is questionable whether or not a pager should decide what is relevant */
/* and what is not in data sent from the kernel.  Data initialize has been */
/* changed to copy back all data sent to it in preparation for its eventual */
/* merge with data return.  It is the kernel that should decide what pages */
/* to write back.  As of the writing of this note, this is indeed the case */
/* the kernel writes back one page at a time through this interface */

kern_return_t
compressor_memory_object_data_initialize(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        memory_object_cluster_size_t            size)
{
        compressor_pager_t      pager;
        memory_object_offset_t  cur_offset;

        compressor_pager_lookup(mem_obj, pager);
        compressor_pager_lock(pager);

        for (cur_offset = offset;
             cur_offset < offset + size;
             cur_offset += PAGE_SIZE) {
                panic("do a data_return() if slot for this page is empty");
        }

        compressor_pager_unlock(pager);

        return KERN_SUCCESS;
}

kern_return_t
compressor_memory_object_data_unlock(
        __unused memory_object_t                mem_obj,
        __unused memory_object_offset_t offset,
        __unused memory_object_size_t           size,
        __unused vm_prot_t              desired_access)
{
        panic("compressor_memory_object_data_unlock()");
        return KERN_FAILURE;
}


/*ARGSUSED*/
kern_return_t
compressor_memory_object_data_return(
        __unused memory_object_t                        mem_obj,
        __unused memory_object_offset_t         offset,
        __unused memory_object_cluster_size_t   size,
        __unused memory_object_offset_t *resid_offset,
        __unused int            *io_error,
        __unused boolean_t      dirty,
        __unused boolean_t      kernel_copy,
        __unused int            upl_flags)
{
        panic("compressor: data_return");
        return KERN_FAILURE;
}

/*
 * Routine:     default_pager_memory_object_create
 * Purpose:
 *      Handle requests for memory objects from the
 *      kernel.
 * Notes:
 *      Because we only give out the default memory
 *      manager port to the kernel, we don't have to
 *      be so paranoid about the contents.
 */
kern_return_t
compressor_memory_object_create(
        memory_object_size_t    new_size,
        memory_object_t         *new_mem_obj)
{
        compressor_pager_t      pager;
        int                     num_chunks;

        if ((uint32_t)(new_size/PAGE_SIZE) != (new_size/PAGE_SIZE)) {
                /* 32-bit overflow for number of pages */
                panic("%s: size 0x%llx overflow\n",
                      __FUNCTION__, (uint64_t) new_size);
                return KERN_INVALID_ARGUMENT;
        }

        pager = (compressor_pager_t) zalloc(compressor_pager_zone);
        if (pager == NULL) {
                return KERN_RESOURCE_SHORTAGE;
        }

        compressor_pager_lock_init(pager);
        pager->cpgr_control = MEMORY_OBJECT_CONTROL_NULL;
        pager->cpgr_references = 1;
        pager->cpgr_num_slots = (uint32_t)(new_size/PAGE_SIZE);
        pager->cpgr_num_slots_occupied = 0;

        num_chunks = (pager->cpgr_num_slots + COMPRESSOR_SLOTS_PER_CHUNK - 1) / COMPRESSOR_SLOTS_PER_CHUNK;
        if (num_chunks > 1) {
                pager->cpgr_slots.cpgr_islots = kalloc(num_chunks * sizeof (pager->cpgr_slots.cpgr_islots[0]));
                bzero(pager->cpgr_slots.cpgr_islots, num_chunks * sizeof (pager->cpgr_slots.cpgr_islots[0]));
        } else if (pager->cpgr_num_slots > 2) {
                pager->cpgr_slots.cpgr_dslots = kalloc(pager->cpgr_num_slots * sizeof (pager->cpgr_slots.cpgr_dslots[0]));
                bzero(pager->cpgr_slots.cpgr_dslots, pager->cpgr_num_slots * sizeof (pager->cpgr_slots.cpgr_dslots[0]));
        } else {
                pager->cpgr_slots.cpgr_eslots[0] = 0;
                pager->cpgr_slots.cpgr_eslots[1] = 0;
        }

        /*
         * Set up associations between this memory object
         * and this compressor_pager structure
         */

        pager->cpgr_pager_ops = &compressor_pager_ops;
        pager->cpgr_pager_header.io_bits = IKOT_MEMORY_OBJECT;

        *new_mem_obj = (memory_object_t) pager;
        return KERN_SUCCESS;
}


unsigned int
compressor_pager_slots_chunk_free(
        compressor_slot_t       *chunk,
        int                     num_slots,
        int                     flags,
        int                     *failures)
{
        int i;
        int retval;
        unsigned int num_slots_freed;

        if (failures)
                *failures = 0;
        num_slots_freed = 0;
        for (i = 0; i < num_slots; i++) {
                if (chunk[i] != 0) {
                        retval = vm_compressor_free(&chunk[i], flags);

                        if (retval == 0)
                                num_slots_freed++;
                        else {
                                if (retval == -2)
                                        assert(flags & C_DONT_BLOCK);

                                if (failures)
                                        *failures += 1;
                        }
                }
        }
        return num_slots_freed;
}

void
compressor_pager_slot_lookup(
        compressor_pager_t      pager,
        boolean_t               do_alloc,
        memory_object_offset_t  offset,
        compressor_slot_t       **slot_pp)
{
        int                     num_chunks;
        uint32_t                page_num;
        int                     chunk_idx;
        int                     slot_idx;
        compressor_slot_t       *chunk;
        compressor_slot_t       *t_chunk;

        page_num = (uint32_t)(offset/PAGE_SIZE);
        if (page_num != (offset/PAGE_SIZE)) {
                /* overflow */
                panic("%s: offset 0x%llx overflow\n",
                      __FUNCTION__, (uint64_t) offset);
                *slot_pp = NULL;
                return;
        }
        if (page_num > pager->cpgr_num_slots) {
                /* out of range */
                *slot_pp = NULL;
                return;
        }
        num_chunks = (pager->cpgr_num_slots + COMPRESSOR_SLOTS_PER_CHUNK - 1) / COMPRESSOR_SLOTS_PER_CHUNK;
        if (num_chunks > 1) {
                /* we have an array of chunks */
                chunk_idx = page_num / COMPRESSOR_SLOTS_PER_CHUNK;
                chunk = pager->cpgr_slots.cpgr_islots[chunk_idx];

                if (chunk == NULL && do_alloc) {
                        t_chunk = kalloc(COMPRESSOR_SLOTS_CHUNK_SIZE);
                        bzero(t_chunk, COMPRESSOR_SLOTS_CHUNK_SIZE);

                        compressor_pager_lock(pager);

                        if ((chunk = pager->cpgr_slots.cpgr_islots[chunk_idx]) == NULL) {
                                chunk = pager->cpgr_slots.cpgr_islots[chunk_idx] = t_chunk;
                                t_chunk = NULL;
                        }
                        compressor_pager_unlock(pager);
                        
                        if (t_chunk)
                                kfree(t_chunk, COMPRESSOR_SLOTS_CHUNK_SIZE);
                }
                if (chunk == NULL) {
                        *slot_pp = NULL;
                } else {
                        slot_idx = page_num % COMPRESSOR_SLOTS_PER_CHUNK;
                        *slot_pp = &chunk[slot_idx];
                }
        } else if (pager->cpgr_num_slots > 2) {
                slot_idx = page_num;
                *slot_pp = &pager->cpgr_slots.cpgr_dslots[slot_idx];
        } else {
                slot_idx = page_num;
                *slot_pp = &pager->cpgr_slots.cpgr_eslots[slot_idx];
        }
}

void
vm_compressor_pager_init(void)
{
        lck_grp_attr_setdefault(&compressor_pager_lck_grp_attr);
        lck_grp_init(&compressor_pager_lck_grp, "compressor_pager", &compressor_pager_lck_grp_attr);
        lck_attr_setdefault(&compressor_pager_lck_attr);

        compressor_pager_zone = zinit(sizeof (struct compressor_pager),
                                      10000 * sizeof (struct compressor_pager),
                                      8192, "compressor_pager");
        zone_change(compressor_pager_zone, Z_CALLERACCT, FALSE);
        zone_change(compressor_pager_zone, Z_NOENCRYPT, TRUE);

        vm_compressor_init();
}

kern_return_t
vm_compressor_pager_put(
        memory_object_t                 mem_obj,
        memory_object_offset_t          offset,
        ppnum_t                         ppnum,
        void                            **current_chead,
        char                            *scratch_buf,
        int                             *compressed_count_delta_p)
{
        compressor_pager_t      pager;
        compressor_slot_t       *slot_p;

        compressor_pager_stats.put++;

        *compressed_count_delta_p = 0;

        /* This routine is called by the pageout thread.  The pageout thread */
        /* cannot be blocked by read activities unless the read activities   */
        /* Therefore the grant of vs lock must be done on a try versus a      */
        /* blocking basis.  The code below relies on the fact that the       */
        /* interface is synchronous.  Should this interface be again async   */
        /* for some type  of pager in the future the pages will have to be   */
        /* returned through a separate, asynchronous path.                   */

        compressor_pager_lookup(mem_obj, pager);

        if ((uint32_t)(offset/PAGE_SIZE) != (offset/PAGE_SIZE)) {
                /* overflow */
                panic("%s: offset 0x%llx overflow\n",
                      __FUNCTION__, (uint64_t) offset);
                return KERN_RESOURCE_SHORTAGE;
        }

        compressor_pager_slot_lookup(pager, TRUE, offset, &slot_p);

        if (slot_p == NULL) {
                /* out of range ? */
                panic("vm_compressor_pager_put: out of range");
        }
        if (*slot_p != 0) {
                /*
                 * Already compressed: forget about the old one.
                 *
                 * This can happen after a vm_object_do_collapse() when
                 * the "backing_object" had some pages paged out and the
                 * "object" had an equivalent page resident.
                 */
                vm_compressor_free(slot_p, 0);
                *compressed_count_delta_p -= 1;
        }
        if (vm_compressor_put(ppnum, slot_p, current_chead, scratch_buf))
                return (KERN_RESOURCE_SHORTAGE);
        *compressed_count_delta_p += 1;

        return (KERN_SUCCESS);
}


kern_return_t
vm_compressor_pager_get(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        ppnum_t                 ppnum,
        int                     *my_fault_type,
        int                     flags,
        int                     *compressed_count_delta_p)
{
        compressor_pager_t      pager;
        kern_return_t           kr;
        compressor_slot_t       *slot_p;
        
        compressor_pager_stats.get++;

        *compressed_count_delta_p = 0;

        if ((uint32_t)(offset/PAGE_SIZE) != (offset/PAGE_SIZE)) {
                panic("%s: offset 0x%llx overflow\n",
                      __FUNCTION__, (uint64_t) offset);
                return KERN_MEMORY_ERROR;
        }

        compressor_pager_lookup(mem_obj, pager);

        /* find the compressor slot for that page */
        compressor_pager_slot_lookup(pager, FALSE, offset, &slot_p);

        if (offset / PAGE_SIZE > pager->cpgr_num_slots) {
                /* out of range */
                kr = KERN_MEMORY_FAILURE;
        } else if (slot_p == NULL || *slot_p == 0) {
                /* compressor does not have this page */
                kr = KERN_MEMORY_ERROR;
        } else {
                /* compressor does have this page */
                kr = KERN_SUCCESS;
        }
        *my_fault_type = DBG_COMPRESSOR_FAULT;
                
        if (kr == KERN_SUCCESS) {
                int     retval;

                /* get the page from the compressor */
                retval = vm_compressor_get(ppnum, slot_p, flags);
                if (retval == -1)
                        kr = KERN_MEMORY_FAILURE;
                else if (retval == 1)
                        *my_fault_type = DBG_COMPRESSOR_SWAPIN_FAULT;
                else if (retval == -2) {
                        assert((flags & C_DONT_BLOCK));
                        kr = KERN_FAILURE;
                }
        }

        if (kr == KERN_SUCCESS) {
                assert(slot_p != NULL);
                if (*slot_p != 0) {
                        /*
                         * We got the page for a copy-on-write fault
                         * and we kept the original in place.  Slot
                         * is still occupied.
                         */
                } else {
                        *compressed_count_delta_p -= 1;
                }
        }

        return kr;
}

unsigned int
vm_compressor_pager_state_clr(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset)
{
        compressor_pager_t      pager;
        compressor_slot_t       *slot_p;
        unsigned int            num_slots_freed;
        
        compressor_pager_stats.state_clr++;

        if ((uint32_t)(offset/PAGE_SIZE) != (offset/PAGE_SIZE)) {
                /* overflow */
                panic("%s: offset 0x%llx overflow\n",
                      __FUNCTION__, (uint64_t) offset);
                return 0;
        }

        compressor_pager_lookup(mem_obj, pager);

        /* find the compressor slot for that page */
        compressor_pager_slot_lookup(pager, FALSE, offset, &slot_p);

        num_slots_freed = 0;
        if (slot_p && *slot_p != 0) {
                vm_compressor_free(slot_p, 0);
                num_slots_freed++;
                assert(*slot_p == 0);
        }

        return num_slots_freed;
}

vm_external_state_t
vm_compressor_pager_state_get(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset)
{
        compressor_pager_t      pager;
        compressor_slot_t       *slot_p;
        
        compressor_pager_stats.state_get++;

        if ((uint32_t)(offset/PAGE_SIZE) != (offset/PAGE_SIZE)) {
                /* overflow */
                panic("%s: offset 0x%llx overflow\n",
                      __FUNCTION__, (uint64_t) offset);
                return VM_EXTERNAL_STATE_ABSENT;
        }

        compressor_pager_lookup(mem_obj, pager);

        /* find the compressor slot for that page */
        compressor_pager_slot_lookup(pager, FALSE, offset, &slot_p);

        if (offset / PAGE_SIZE > pager->cpgr_num_slots) {
                /* out of range */
                return VM_EXTERNAL_STATE_ABSENT;
        } else if (slot_p == NULL || *slot_p == 0) {
                /* compressor does not have this page */
                return VM_EXTERNAL_STATE_ABSENT;
        } else {
                /* compressor does have this page */
                return VM_EXTERNAL_STATE_EXISTS;
        }
}

unsigned int
vm_compressor_pager_reap_pages(
        memory_object_t         mem_obj,
        int                     flags)
{
        compressor_pager_t      pager;
        int                     num_chunks;
        int                     failures;
        int                     i;
        compressor_slot_t       *chunk;
        unsigned int            num_slots_freed;

        compressor_pager_lookup(mem_obj, pager);
        if (pager == NULL)
                return 0;

        compressor_pager_lock(pager);

        /* reap the compressor slots */
        num_slots_freed = 0;

        num_chunks = (pager->cpgr_num_slots + COMPRESSOR_SLOTS_PER_CHUNK -1) / COMPRESSOR_SLOTS_PER_CHUNK;
        if (num_chunks > 1) {
                /* we have an array of chunks */
                for (i = 0; i < num_chunks; i++) {
                        chunk = pager->cpgr_slots.cpgr_islots[i];
                        if (chunk != NULL) {
                                num_slots_freed +=
                                        compressor_pager_slots_chunk_free(
                                                chunk,
                                                COMPRESSOR_SLOTS_PER_CHUNK,
                                                flags,
                                                &failures);
                                if (failures == 0) {
                                        pager->cpgr_slots.cpgr_islots[i] = NULL;
                                        kfree(chunk, COMPRESSOR_SLOTS_CHUNK_SIZE);
                                }
                        }
                }
        } else if (pager->cpgr_num_slots > 2) {
                chunk = pager->cpgr_slots.cpgr_dslots;
                num_slots_freed +=
                        compressor_pager_slots_chunk_free(
                                chunk,
                                pager->cpgr_num_slots,
                                flags,
                                NULL);
        } else {
                chunk = &pager->cpgr_slots.cpgr_eslots[0];
                num_slots_freed +=
                        compressor_pager_slots_chunk_free(
                                chunk,
                                pager->cpgr_num_slots,
                                flags,
                                NULL);
        }

        compressor_pager_unlock(pager);

        return num_slots_freed;
}

void
vm_compressor_pager_transfer(
        memory_object_t         dst_mem_obj,
        memory_object_offset_t  dst_offset,
        memory_object_t         src_mem_obj,
        memory_object_offset_t  src_offset)
{
        compressor_pager_t      src_pager, dst_pager;
        compressor_slot_t       *src_slot_p, *dst_slot_p;
        
        compressor_pager_stats.transfer++;

        /* find the compressor slot for the destination */
        assert((uint32_t) dst_offset == dst_offset);
        compressor_pager_lookup(dst_mem_obj, dst_pager);
        assert(dst_offset / PAGE_SIZE <= dst_pager->cpgr_num_slots);
        compressor_pager_slot_lookup(dst_pager, TRUE, (uint32_t) dst_offset,
                                     &dst_slot_p);
        assert(dst_slot_p != NULL);
        assert(*dst_slot_p == 0);

        /* find the compressor slot for the source */
        assert((uint32_t) src_offset == src_offset);
        compressor_pager_lookup(src_mem_obj, src_pager);
        assert(src_offset / PAGE_SIZE <= src_pager->cpgr_num_slots);
        compressor_pager_slot_lookup(src_pager, FALSE, (uint32_t) src_offset,
                                     &src_slot_p);
        assert(src_slot_p != NULL);
        assert(*src_slot_p != 0);

        /* transfer the slot from source to destination */
        vm_compressor_transfer(dst_slot_p, src_slot_p);
        OSAddAtomic(-1, &src_pager->cpgr_num_slots_occupied);
        OSAddAtomic(+1, &dst_pager->cpgr_num_slots_occupied);
}

memory_object_offset_t
vm_compressor_pager_next_compressed(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset)
{
        compressor_pager_t      pager;
        uint32_t                num_chunks;
        uint32_t                page_num;
        uint32_t                chunk_idx;
        uint32_t                slot_idx;
        compressor_slot_t       *chunk;

        compressor_pager_lookup(mem_obj, pager);

        page_num = (uint32_t)(offset / PAGE_SIZE);
        if (page_num != (offset/PAGE_SIZE)) {
                /* overflow */
                return (memory_object_offset_t) -1;
        }
        if (page_num > pager->cpgr_num_slots) {
                /* out of range */
                return (memory_object_offset_t) -1;
        }

        num_chunks = ((pager->cpgr_num_slots + COMPRESSOR_SLOTS_PER_CHUNK - 1) /
                      COMPRESSOR_SLOTS_PER_CHUNK);

        if (num_chunks == 1) {
                if (pager->cpgr_num_slots > 2) {
                        chunk = pager->cpgr_slots.cpgr_dslots;
                } else {
                        chunk = &pager->cpgr_slots.cpgr_eslots[0];
                }
                for (slot_idx = page_num;
                     slot_idx < pager->cpgr_num_slots;
                     slot_idx++) {
                        if (chunk[slot_idx] != 0) {
                                /* found a non-NULL slot in this chunk */
                                return (memory_object_offset_t) (slot_idx *
                                                                 PAGE_SIZE);
                        }
                }
                return (memory_object_offset_t) -1;
        }

        /* we have an array of chunks; find the next non-NULL chunk */
        chunk = NULL;
        for (chunk_idx = page_num / COMPRESSOR_SLOTS_PER_CHUNK,
                     slot_idx = page_num % COMPRESSOR_SLOTS_PER_CHUNK;
             chunk_idx < num_chunks;
             chunk_idx++,
                     slot_idx = 0) {
                chunk = pager->cpgr_slots.cpgr_islots[chunk_idx];
                if (chunk == NULL) {
                        /* no chunk here: try the next one */
                        continue;
                }
                /* search for an occupied slot in this chunk */
                for (;
                     slot_idx < COMPRESSOR_SLOTS_PER_CHUNK;
                     slot_idx++) {
                        if (chunk[slot_idx] != 0) {
                                /* found an occupied slot in this chunk */
                                uint32_t next_slot;

                                next_slot = ((chunk_idx *
                                              COMPRESSOR_SLOTS_PER_CHUNK) +
                                             slot_idx);
                                if (next_slot > pager->cpgr_num_slots) {
                                        /* went beyond end of object */
                                        return (memory_object_offset_t) -1;
                                }
                                return (memory_object_offset_t) (next_slot *
                                                                 PAGE_SIZE);
                        }
                }
        }
        return (memory_object_offset_t) -1;
}

unsigned int
vm_compressor_pager_get_count(
        memory_object_t mem_obj)
{
        compressor_pager_t      pager;

        compressor_pager_lookup(mem_obj, pager);
        if (pager == NULL)
                return 0;

        /*
         * The caller should have the VM object locked and one
         * needs that lock to do a page-in or page-out, so no
         * need to lock the pager here.
         */
        assert(pager->cpgr_num_slots_occupied >= 0);

        return pager->cpgr_num_slots_occupied;
}

void
vm_compressor_pager_count(
        memory_object_t mem_obj,
        int             compressed_count_delta,
        boolean_t       shared_lock,
        vm_object_t     object __unused)
{
        compressor_pager_t      pager;

        if (compressed_count_delta == 0) {
                return;
        }

        compressor_pager_lookup(mem_obj, pager);
        if (pager == NULL)
                return;

        if (compressed_count_delta < 0) {
                assert(pager->cpgr_num_slots_occupied >=
                       (unsigned int) -compressed_count_delta);
        }

        /*
         * The caller should have the VM object locked,
         * shared or exclusive.
         */
        if (shared_lock) {
                vm_object_lock_assert_shared(object);
                OSAddAtomic(compressed_count_delta,
                            &pager->cpgr_num_slots_occupied);
        } else {
                vm_object_lock_assert_exclusive(object);
                pager->cpgr_num_slots_occupied += compressed_count_delta;
        }
}

#if CONFIG_FREEZE
kern_return_t
vm_compressor_pager_relocate(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        void                    **current_chead)
{
        /*
         * Has the page at this offset been compressed?
         */

        compressor_slot_t *slot_p;
        compressor_pager_t dst_pager;

        assert(mem_obj);
                
        compressor_pager_lookup(mem_obj, dst_pager);
        if (dst_pager == NULL)
                return KERN_FAILURE;

        compressor_pager_slot_lookup(dst_pager, FALSE, offset, &slot_p);
        return (vm_compressor_relocate(current_chead, slot_p));
}
#endif /* CONFIG_FREEZE */