hfs-556.60.1.tar.gz

[apple/hfs.git] / core / hfs_hotfiles.c

/*
 * Copyright (c) 2003-2015 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,
 * 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@
 */

#include <libkern/OSAtomic.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/ubc.h>
#include <sys/vnode.h>
#include <sys/kauth.h>
#include <sys/vm.h>

#include "hfs.h"
#include "hfs_endian.h"
#include "hfs_format.h"
#include "hfs_mount.h"
#include "hfs_hotfiles.h"

#include "BTreeScanner.h"


#define HFC_DEBUG  0
#define HFC_VERBOSE 0


/*
 * Minimum post Tiger base time.
 * Thu Mar 31 17:00:00 2005
 */
#define HFC_MIN_BASE_TIME   0x424c8f00L

/*
 * Hot File List (runtime).
 */
typedef struct hotfileinfo {
        u_int32_t  hf_fileid;
        u_int32_t  hf_temperature;
        u_int32_t  hf_blocks;
} hotfileinfo_t;

typedef struct hotfilelist {
        size_t            hfl_size;
        u_int32_t     hfl_magic;
        u_int32_t     hfl_version;
        time_t        hfl_duration;    /* duration of sample period */
        int           hfl_count;       /* count of hot files recorded */
        int           hfl_next;        /* next file to move */
        int           hfl_totalblocks; /* total hot file blocks */
        int           hfl_reclaimblks; /* blocks to reclaim in HFV */
        u_int32_t     hfl_spare[2];
        hotfileinfo_t hfl_hotfile[1];  /* array of hot files */
} hotfilelist_t;


/*
 * Hot File Entry (runtime).
 */
typedef struct hotfile_entry {
        struct  hotfile_entry  *left;
        struct  hotfile_entry  *right;
        u_int32_t  fileid;
        u_int32_t  temperature;
        u_int32_t  blocks;
} hotfile_entry_t;


//
// We cap the max temperature for non-system files to "MAX_NORMAL_TEMP"
// so that they will always have a lower temperature than system (aka 
// "auto-cached") files.  System files have MAX_NORMAL_TEMP added to
// their temperature which produces two bands of files (all non-system
// files will have a temp less than MAX_NORMAL_TEMP and all system
// files will have a temp greatern than MAX_NORMAL_TEMP).
//
// This puts non-system files on the left side of the hotfile btree 
// (and we start evicting from the left-side of the tree).  The idea is 
// that we will evict non-system files more aggressively since their
// working set changes much more dynamically than system files (which 
// are for the most part, static).
//
// NOTE: these values have to fit into a 32-bit int.  We use a
//       value of 1-billion which gives a pretty broad range
//       and yet should not run afoul of any sign issues.
//
#define MAX_NORMAL_TEMP    1000000000
#define HF_TEMP_RANGE      MAX_NORMAL_TEMP


//
// These used to be defines of the hard coded values.  But if
// we're on an cooperative fusion (CF) system we need to change 
// the values (which happens in hfs_recording_init()
// 
uint32_t hfc_default_file_count = 1000;
uint32_t hfc_default_duration   = (3600 * 60);
uint32_t hfc_max_file_count     = 5000;
uint64_t hfc_max_file_size      = (10 * 1024 * 1024);


/*
 * Hot File Recording Data (runtime).
 */
typedef struct hotfile_data {
        size_t                          size;
        struct hfsmount    *hfsmp;
        long                            refcount;
        u_int32_t                       activefiles;  /* active number of hot files */
        u_int32_t                       threshold;
        u_int32_t                       maxblocks;
        hotfile_entry_t    *rootentry;
        hotfile_entry_t    *freelist;
        hotfile_entry_t    *coldest;
        hotfile_entry_t         entries[];
} hotfile_data_t;

static int  hfs_recording_start (struct hfsmount *);
static int  hfs_recording_stop (struct hfsmount *);

/* Hotfiles pinning routines */
static int hfs_getvnode_and_pin (struct hfsmount *hfsmp, uint32_t fileid, uint32_t *pinned);
static int hfs_pin_extent_record (struct hfsmount *hfsmp, HFSPlusExtentRecord extents, uint32_t *pinned);
static int hfs_pin_catalog_rec (struct hfsmount *hfsmp, HFSPlusCatalogFile *cfp, int rsrc);

/*
 * Hot File Data recording functions (in-memory binary tree).
 */
static int               hf_insert (hotfile_data_t *, hotfile_entry_t *);
static void              hf_delete (hotfile_data_t *, u_int32_t, u_int32_t);
static hotfile_entry_t * hf_coldest (hotfile_data_t *);
static hotfile_entry_t * hf_getnewentry (hotfile_data_t *);
static void              hf_getsortedlist (hotfile_data_t *, hotfilelist_t *);

#if HFC_DEBUG
static hotfile_entry_t * hf_lookup (hotfile_data_t *, u_int32_t, u_int32_t);
static void  hf_maxdepth(hotfile_entry_t *, int, int *);
static void  hf_printtree (hotfile_entry_t *);
#endif

/*
 * Hot File misc support functions.
 */
static int  hotfiles_collect (struct hfsmount *);
static int  hotfiles_age (struct hfsmount *);
static int  hotfiles_adopt (struct hfsmount *);
static int  hotfiles_evict (struct hfsmount *, vfs_context_t);
static int  hotfiles_refine (struct hfsmount *);
static int  hotextents(struct hfsmount *, HFSPlusExtentDescriptor *);
static int  hfs_addhotfile_internal(struct vnode *);
static int  hfs_hotfile_cur_freeblks(hfsmount_t *hfsmp);


/*
 * Hot File Cluster B-tree (on disk) functions.
 */
static int  hfc_btree_create (struct hfsmount *, unsigned int, unsigned int);
static int  hfc_btree_open (struct hfsmount *, struct vnode **);
static int  hfc_btree_open_ext(struct hfsmount *hfsmp, struct vnode **vpp, int ignore_btree_errs);
static int  hfc_btree_close (struct hfsmount *, struct vnode *);
static int  hfc_btree_delete_record(struct hfsmount *hfsmp, BTreeIterator *iterator, HotFileKey *key);
static int  hfc_btree_delete(struct hfsmount *hfsmp);
static int  hfc_comparekeys (HotFileKey *, HotFileKey *);


char hfc_tag[] = "CLUSTERED HOT FILES B-TREE     ";


/*
 *========================================================================
 *                       HOT FILE INTERFACE ROUTINES
 *========================================================================
 */

/*
 * Start recording the hottest files on a file system.
 *
 * Requires that the hfc_mutex be held.
 */
static int
hfs_recording_start(struct hfsmount *hfsmp)
{
        hotfile_data_t *hotdata;
        struct timeval tv;
        int maxentries;
        size_t size;
        int i;
        int error;

        if ((hfsmp->hfs_flags & HFS_READ_ONLY) ||
            (hfsmp->jnl == NULL) ||
            (hfsmp->hfs_flags & HFS_METADATA_ZONE) == 0) {
                return (EPERM);
        }
        if (HFSTOVCB(hfsmp)->freeBlocks < (2 * (u_int32_t)hfsmp->hfs_hotfile_maxblks)) {
                return (ENOSPC);
        }
        if (hfsmp->hfc_stage != HFC_IDLE) {
                return (EBUSY);
        }
        hfsmp->hfc_stage = HFC_BUSY;

        if (hfsmp->hfc_recdata) {
                hfs_free(hfsmp->hfc_recdata, hfsmp->hfc_recdata->size);
                hfsmp->hfc_recdata = NULL;
        }
        if (hfsmp->hfc_filelist) {
                hfs_free(hfsmp->hfc_filelist, hfsmp->hfc_filelist->hfl_size);
                hfsmp->hfc_filelist = NULL;
        }

        microtime(&tv);  /* Times are base on GMT time. */

        /*
         * On first startup check for suspended recording.
         */
        if (hfsmp->hfc_timebase == 0 &&
            hfc_btree_open(hfsmp, &hfsmp->hfc_filevp) == 0) {
                HotFilesInfo hotfileinfo;

                if ((BTGetUserData(VTOF(hfsmp->hfc_filevp), &hotfileinfo,
                                   sizeof(hotfileinfo)) == 0) &&
                    (SWAP_BE32 (hotfileinfo.magic) == HFC_MAGIC) &&
                    (SWAP_BE32 (hotfileinfo.timeleft) > 0) &&
                    (SWAP_BE32 (hotfileinfo.timebase) > 0)) {
                        if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                                if (hfsmp->hfs_hotfile_freeblks == 0) {
                                        hfsmp->hfs_hotfile_freeblks = hfsmp->hfs_hotfile_maxblks - SWAP_BE32 (hotfileinfo.usedblocks);
                                }
                                hfsmp->hfc_maxfiles = 0x7fffffff;
                                printf("hfs: %s: %s: hotfile freeblocks: %d, max: %d\n", hfsmp->vcbVN, __FUNCTION__,
                                       hfsmp->hfs_hotfile_freeblks, hfsmp->hfs_hotfile_maxblks);
                        } else {
                                hfsmp->hfc_maxfiles = SWAP_BE32 (hotfileinfo.maxfilecnt);
                        }
                        hfsmp->hfc_timebase = SWAP_BE32 (hotfileinfo.timebase);
                        int timeleft = (int)SWAP_BE32(hotfileinfo.timeleft);
                        if (timeleft < 0 || timeleft > (int)(HFC_DEFAULT_DURATION*2)) {
                                // in case this field got botched, don't let it screw things up
                                // printf("hfs: hotfiles: bogus looking timeleft: %d\n", timeleft);
                                timeleft = HFC_DEFAULT_DURATION;
                        }
                        hfsmp->hfc_timeout = timeleft + tv.tv_sec ;
                        /* Fix up any bogus timebase values. */
                        if (hfsmp->hfc_timebase < HFC_MIN_BASE_TIME) {
                                hfsmp->hfc_timebase = hfsmp->hfc_timeout - HFC_DEFAULT_DURATION;
                        }
#if HFC_VERBOSE
                        printf("hfs: Resume recording hot files on %s (%d secs left (%d); timeout %ld)\n",
                               hfsmp->vcbVN, SWAP_BE32 (hotfileinfo.timeleft), timeleft, hfsmp->hfc_timeout - tv.tv_sec);
#endif
                } else {
                        hfsmp->hfc_maxfiles = HFC_DEFAULT_FILE_COUNT;
                        hfsmp->hfc_timebase = tv.tv_sec + 1;
                        hfsmp->hfc_timeout = hfsmp->hfc_timebase + HFC_DEFAULT_DURATION;
                }
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                hfsmp->hfc_filevp = NULL;
        } else {
                struct cat_attr cattr;
                u_int32_t cnid;

                /*
                 * Make sure a btree file exists.
                 */
                cnid = GetFileInfo(HFSTOVCB(hfsmp), kRootDirID, HFC_FILENAME, &cattr, NULL);
                if ((cnid == 0) &&
                    !S_ISREG(cattr.ca_mode) &&
                    (error = hfc_btree_create(hfsmp, HFSTOVCB(hfsmp)->blockSize, HFC_DEFAULT_FILE_COUNT))) {
                        hfsmp->hfc_stage = HFC_IDLE;
                        wakeup((caddr_t)&hfsmp->hfc_stage);
                        return (error);
                }
#if HFC_VERBOSE
                printf("hfs: begin recording hot files on %s (hotfile start/end block: %d - %d; max/free: %d/%d; maxfiles: %d)\n",
                       hfsmp->vcbVN,
                       hfsmp->hfs_hotfile_start, hfsmp->hfs_hotfile_end,
                       hfsmp->hfs_hotfile_maxblks, hfsmp->hfs_hotfile_freeblks, hfsmp->hfc_maxfiles);
#endif
                hfsmp->hfc_maxfiles = HFC_DEFAULT_FILE_COUNT;
                hfsmp->hfc_timeout = tv.tv_sec + HFC_DEFAULT_DURATION;

                /* Reset time base.  */
                if (hfsmp->hfc_timebase == 0) {
                        hfsmp->hfc_timebase = tv.tv_sec + 1;
                } else {
                        time_t cumulativebase;

                        cumulativebase = hfsmp->hfc_timeout - (HFC_CUMULATIVE_CYCLES * HFC_DEFAULT_DURATION);
                        hfsmp->hfc_timebase = MAX(hfsmp->hfc_timebase, cumulativebase);
                }
        }

        if ((hfsmp->hfc_maxfiles == 0) ||
            (hfsmp->hfc_maxfiles > HFC_MAXIMUM_FILE_COUNT)) {
                hfsmp->hfc_maxfiles = HFC_DEFAULT_FILE_COUNT;
        }
        maxentries = hfsmp->hfc_maxfiles;

        size = sizeof(hotfile_data_t) + maxentries * sizeof(hotfile_entry_t);
        hotdata = hfs_mallocz(size);
        hotdata->size = size;

        for (i = 1; i < maxentries ; i++)
                hotdata->entries[i-1].right = &hotdata->entries[i];
        
        hotdata->freelist = &hotdata->entries[0];
        /* 
         * Establish minimum temperature and maximum file size.
         */
        hotdata->threshold = HFC_MINIMUM_TEMPERATURE;
        hotdata->maxblocks = HFC_MAXIMUM_FILESIZE / HFSTOVCB(hfsmp)->blockSize;
        hotdata->hfsmp = hfsmp;
        
        hfsmp->hfc_recdata = hotdata;
        hfsmp->hfc_stage = HFC_RECORDING;
        wakeup((caddr_t)&hfsmp->hfc_stage);
        return (0);
}

/*
 * Stop recording the hotest files on a file system.
 *
 * Requires that the hfc_mutex be held.
 */
static int
hfs_recording_stop(struct hfsmount *hfsmp)
{
        hotfile_data_t *hotdata;
        hotfilelist_t  *listp;
        struct timeval tv;
        size_t  size;
        enum hfc_stage newstage = HFC_IDLE;
        int  error;

        if (hfsmp->hfc_stage != HFC_RECORDING)
                return (EPERM);

        hfsmp->hfc_stage = HFC_BUSY;

        hotfiles_collect(hfsmp);


        /*
         * Convert hot file data into a simple file id list....
         *
         * then dump the sample data
         */
#if HFC_VERBOSE
        printf("hfs: end of hot file recording on %s\n", hfsmp->vcbVN);
#endif
        hotdata = hfsmp->hfc_recdata;
        if (hotdata == NULL)
                return (0);
        hfsmp->hfc_recdata = NULL;
        hfsmp->hfc_stage = HFC_EVALUATION;
        wakeup((caddr_t)&hfsmp->hfc_stage);

#if HFC_VERBOSE
        printf("hfs:   curentries: %d\n", hotdata->activefiles);
#endif
        /*
         * If no hot files recorded then we're done.
         */
        if (hotdata->rootentry == NULL) {
                error = 0;
                goto out;
        }

        /* Open the B-tree file for writing... */
        if (hfsmp->hfc_filevp)
                panic("hfs_recording_stop: hfc_filevp exists (vp = %p)", hfsmp->hfc_filevp);

        error = hfc_btree_open(hfsmp, &hfsmp->hfc_filevp);
        if (error) {
                goto out;
        }

        /*
         * Age the previous set of clustered hot files.
         */
        error = hotfiles_age(hfsmp);
        if (error) {
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                hfsmp->hfc_filevp = NULL;
                goto out;
        }

        /*
         * Create a sorted list of hotest files.
         */
        size = sizeof(hotfilelist_t);
        size += sizeof(hotfileinfo_t) * (hotdata->activefiles - 1);
        listp = hfs_mallocz(size);
        listp->hfl_size = size;

        hf_getsortedlist(hotdata, listp);       /* NOTE: destroys hot file tree! */
        microtime(&tv);
        listp->hfl_duration = tv.tv_sec - hfsmp->hfc_timebase;
        hfs_assert(!hfsmp->hfc_filelist);
        hfsmp->hfc_filelist = listp;

        /*
         * Account for duplicates.
         */
        error = hotfiles_refine(hfsmp);
        if (error) {
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                hfsmp->hfc_filevp = NULL;
                goto out;
        }

        /*
         * Compute the amount of space to reclaim...
         */
        if (listp->hfl_totalblocks > hfs_hotfile_cur_freeblks(hfsmp)) {
                listp->hfl_reclaimblks =
                        MIN(listp->hfl_totalblocks, hfsmp->hfs_hotfile_maxblks) -
                        hfsmp->hfs_hotfile_freeblks;
#if HFC_VERBOSE
                printf("hfs_recording_stop: need to reclaim %d blocks\n", listp->hfl_reclaimblks);
#endif
                if (listp->hfl_reclaimblks)
                        newstage = HFC_EVICTION;
                else
                        newstage = HFC_ADOPTION;
        } else {
                newstage = HFC_ADOPTION;
        }
        
        if (newstage == HFC_ADOPTION && listp->hfl_totalblocks == 0) {
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                hfsmp->hfc_filevp = NULL;
                newstage = HFC_IDLE;
        }
out:
#if HFC_VERBOSE
        if (newstage == HFC_EVICTION)
                printf("hfs: evicting coldest files\n");
        else if (newstage == HFC_ADOPTION)
                printf("hfs: adopting hotest files\n");
#endif
        hfs_free(hotdata, hotdata->size);

        hfsmp->hfc_stage = newstage;
        wakeup((caddr_t)&hfsmp->hfc_stage);
        return (error);
}

static void
save_btree_user_info(struct hfsmount *hfsmp)
{
        HotFilesInfo hotfileinfo;
        struct timeval tv;

        microtime(&tv);
        hotfileinfo.magic       = SWAP_BE32 (HFC_MAGIC);
        hotfileinfo.version     = SWAP_BE32 (HFC_VERSION);
        hotfileinfo.duration    = SWAP_BE32 (HFC_DEFAULT_DURATION);
        hotfileinfo.timebase    = SWAP_BE32 (hfsmp->hfc_timebase);
        hotfileinfo.timeleft    = SWAP_BE32 (hfsmp->hfc_timeout - tv.tv_sec);
        hotfileinfo.threshold   = SWAP_BE32 (HFC_MINIMUM_TEMPERATURE);
        hotfileinfo.maxfileblks = SWAP_BE32 (HFC_MAXIMUM_FILESIZE / HFSTOVCB(hfsmp)->blockSize);
        if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                hotfileinfo.usedblocks = SWAP_BE32 (hfsmp->hfs_hotfile_maxblks - hfs_hotfile_cur_freeblks(hfsmp));
#if HFC_VERBOSE
                printf("hfs: %s: saving usedblocks = %d (timeleft: %d; timeout %ld)\n", hfsmp->vcbVN, (hfsmp->hfs_hotfile_maxblks - hfsmp->hfs_hotfile_freeblks),
                       SWAP_BE32(hotfileinfo.timeleft), hfsmp->hfc_timeout);
#endif
        } else {
                hotfileinfo.maxfilecnt  = SWAP_BE32 (HFC_DEFAULT_FILE_COUNT);
        }
        strlcpy((char *)hotfileinfo.tag, hfc_tag, sizeof hotfileinfo.tag);
        (void) BTSetUserData(VTOF(hfsmp->hfc_filevp), &hotfileinfo, sizeof(hotfileinfo));
}

/*
 * Suspend recording the hotest files on a file system.
 */
int
hfs_recording_suspend(struct hfsmount *hfsmp)
{
        hotfile_data_t *hotdata = NULL;
        int  error;

        if (hfsmp->hfc_stage == HFC_DISABLED)
                return (0);

        lck_mtx_lock(&hfsmp->hfc_mutex);

        /*
         * XXX NOTE
         * A suspend can occur during eval/evict/adopt stage.
         * In that case we would need to write out info and
         * flush our HFBT vnode. Currently we just bail.
         */

        hotdata = hfsmp->hfc_recdata;
        if (hotdata == NULL || hfsmp->hfc_stage != HFC_RECORDING) {
                error = 0;
                goto out;
        }
        hfsmp->hfc_stage = HFC_BUSY;

#if HFC_VERBOSE
        printf("hfs: suspend hot file recording on %s\n", hfsmp->vcbVN);
#endif
        error = hfc_btree_open(hfsmp, &hfsmp->hfc_filevp);
        if (error) {
                printf("hfs_recording_suspend: err %d opening btree\n", error);
                goto out;
        }

        if (hfs_start_transaction(hfsmp) != 0) {
            goto out;
        }
        if (hfs_lock(VTOC(hfsmp->hfc_filevp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT) != 0) {
                goto end_transaction;
        }

        save_btree_user_info(hfsmp);

        hfs_unlock(VTOC(hfsmp->hfc_filevp));

end_transaction:
        hfs_end_transaction(hfsmp);

out:
        if (hfsmp->hfc_filevp) {
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                hfsmp->hfc_filevp = NULL;
        }
        if (hotdata) {
                hfs_free(hotdata, hotdata->size);
                hfsmp->hfc_recdata = NULL;
        }
        hfsmp->hfc_stage = HFC_DISABLED;
        wakeup((caddr_t)&hfsmp->hfc_stage);

        lck_mtx_unlock(&hfsmp->hfc_mutex);
        return (error);
}


static void
reset_file_ids(struct hfsmount *hfsmp, uint32_t *fileid_table, int num_ids)
{
        int i, error;

        for(i=0; i < num_ids; i++) {
                struct vnode *vp;

                error = hfs_vget(hfsmp, fileid_table[i], &vp, 0, 0);
                if (error) {
                        if (error == ENOENT) {
                                error = 0;
                                continue;  /* stale entry, go to next */
                        }
                        continue;
                }

                // hfs_vget returns a locked cnode so no need to lock here

                if ((hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) && (VTOC(vp)->c_attr.ca_recflags & kHFSFastDevPinnedMask)) {
                        error = hfs_pin_vnode(hfsmp, vp, HFS_UNPIN_IT, NULL);
                }

                /*
                 * The updates to the catalog must be journaled
                 */
                hfs_start_transaction(hfsmp);

                //
                // turn off _all_ the hotfile related bits since we're resetting state
                //
                if (VTOC(vp)->c_attr.ca_recflags & kHFSFastDevCandidateMask) {
                        vnode_clearfastdevicecandidate(vp);
                }

                VTOC(vp)->c_attr.ca_recflags &= ~(kHFSFastDevPinnedMask|kHFSDoNotFastDevPinMask|kHFSFastDevCandidateMask|kHFSAutoCandidateMask);
                VTOC(vp)->c_flag |= C_MODIFIED;

                hfs_update(vp, 0);

                hfs_end_transaction(hfsmp);
                
                hfs_unlock(VTOC(vp));
                vnode_put(vp);
        }
}

static int
flag_hotfile(struct hfsmount *hfsmp, const char *filename)
{
        struct vnode *dvp = NULL, *fvp = NULL;
        vfs_context_t ctx = vfs_context_kernel();
        int  error=0;
        size_t fname_len;
        const char *orig_fname = filename;
        
        if (filename == NULL) {
                return EINVAL;
        }

        fname_len = strlen(filename);    // do NOT include the trailing '\0' so that we break out of the loop below
        
        error = hfs_vfs_root(HFSTOVFS(hfsmp), &dvp, ctx);
        if (error) {
                return (error);
        }

        /* At this point, 'dvp' must be considered iocounted */
        const char *ptr;
        ptr = filename;

        while (ptr < (orig_fname + fname_len - 1)) {
                for(; ptr < (orig_fname + fname_len) && *ptr && *ptr != '/'; ptr++) {
                        /* just keep advancing till we reach the end of the string or a slash */
                }

                struct componentname cname = {
                        .cn_nameiop = LOOKUP,
                        .cn_flags       = ISLASTCN,
                        .cn_pnbuf       = __DECONST(char *, orig_fname),
                        .cn_nameptr = __DECONST(char *, filename),
                        .cn_pnlen       = fname_len,
                        .cn_namelen = ptr - filename
                };

        struct vnop_lookup_args ap = {
            .a_dvp      = dvp,
            .a_vpp      = &fvp,
            .a_cnp      = &cname,
            .a_context  = ctx
        };

        error = hfs_vnop_lookup(&ap);
                if (error) {
                        /*
                         * If 'dvp' is non-NULL, then it has an iocount.  Make sure to release it
                         * before bailing out.  VNOP_LOOKUP could legitimately return ENOENT
                         * if the item didn't exist or if we raced with a delete.
                         */
                        if (dvp) {
                                vnode_put(dvp);
                                dvp = NULL;
                        }
                        return error;
                }

                if (ptr < orig_fname + fname_len - 1) {
                        //
                        // we've got a multi-part pathname so drop the ref on the dir,
                        // make dvp become what we just looked up, and advance over
                        // the slash character in the pathname to get to the next part
                        // of the component
                        //
                        vnode_put(dvp);
                        dvp = fvp;
                        fvp = NULL;

                        filename = ++ptr;   // skip the slash character
                }
        }
        
        if (fvp == NULL) {
                error = ENOENT;
                goto out;
        }

        struct cnode *cp = VTOC(fvp);
        if ((error = hfs_lock(cp, HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT)) != 0) {
                goto out;
        }

        hfs_start_transaction(hfsmp);
        
        cp->c_attr.ca_recflags |= (kHFSFastDevCandidateMask|kHFSAutoCandidateMask);
        cp->c_flag |= C_MODIFIED;

        hfs_update(fvp, 0);

        hfs_end_transaction(hfsmp);

        hfs_unlock(cp);
        //printf("hfs: flagged /%s with the fast-dev-candidate|auto-candidate flags\n", filename);


out:
        if (fvp) {
                vnode_put(fvp);
                fvp = NULL;
        }

        if (dvp) {
                vnode_put(dvp);
                dvp = NULL;
        }

        return error;
}


static void
hfs_setup_default_cf_hotfiles(struct hfsmount *hfsmp)
{
        const char *system_default_hotfiles[] = {
                "usr",
                "System",
                "Applications",
                "private/var/db/dyld"
        };
        int i;

        for(i=0; i < (int)(sizeof(system_default_hotfiles)/sizeof(char *)); i++) {
                flag_hotfile(hfsmp, system_default_hotfiles[i]);
        }
}


#define NUM_FILE_RESET_IDS   4096    // so we allocate 16k to hold file-ids

static void
hfs_hotfile_reset(struct hfsmount *hfsmp)
{
        CatalogKey * keyp;
        CatalogRecord * datap;
        u_int32_t  dataSize;
        BTScanState scanstate;
        BTreeIterator * iterator = NULL;
        FSBufferDescriptor  record;
        u_int32_t  data;
        u_int32_t  cnid;
        int error = 0;
        uint32_t *fileids=NULL;
        int cur_id_index = 0;

        int cleared = 0;  /* debug variables */
        int filecount = 0;
        int dircount = 0;

#if HFC_VERBOSE
        printf("hfs: %s: %s\n", hfsmp->vcbVN, __FUNCTION__);
#endif

        iterator = hfs_mallocz(sizeof(*iterator));

        fileids = hfs_malloc(NUM_FILE_RESET_IDS * sizeof(uint32_t));

        record.bufferAddress = &data;
        record.itemSize = sizeof(u_int32_t);
        record.itemCount = 1;

        /*
         * Get ready to scan the Catalog file.
         */
        error = BTScanInitialize(VTOF(HFSTOVCB(hfsmp)->catalogRefNum), 0, 0, 0,
                               kCatSearchBufferSize, &scanstate);
        if (error) {
                printf("hfs_hotfile_reset: err %d BTScanInit\n", error);
                goto out;
        }

        /*
         * Visit all the catalog btree leaf records, clearing any that have the
         * HotFileCached bit set.
         */
        for (;;) {
                error = BTScanNextRecord(&scanstate, 0, (void **)&keyp, (void **)&datap, &dataSize);
                if (error) {
                        if (error == btNotFound)
                                error = 0;
                        else
                                printf("hfs_hotfile_reset: err %d BTScanNext\n", error);
                        break;
                }

                if (datap->recordType == kHFSPlusFolderRecord && (dataSize == sizeof(HFSPlusCatalogFolder))) {
                        HFSPlusCatalogFolder *dirp = (HFSPlusCatalogFolder *)datap;

                        dircount++;
                
                        if ((dirp->flags & (kHFSFastDevPinnedMask|kHFSDoNotFastDevPinMask|kHFSFastDevCandidateMask|kHFSAutoCandidateMask)) == 0) {
                                continue;
                        }

                        cnid = dirp->folderID;
                } else if ((datap->recordType == kHFSPlusFileRecord) && (dataSize == sizeof(HFSPlusCatalogFile))) {
                        HFSPlusCatalogFile *filep = (HFSPlusCatalogFile *)datap;   

                        filecount++;

                        /*
                         * If the file doesn't have any of the HotFileCached bits set, ignore it.
                         */
                        if ((filep->flags & (kHFSFastDevPinnedMask|kHFSDoNotFastDevPinMask|kHFSFastDevCandidateMask|kHFSAutoCandidateMask)) == 0) {
                                continue;
                        }

                        cnid = filep->fileID;
                } else {
                        continue;
                }

                /* Skip over journal files. */
                if (cnid == hfsmp->hfs_jnlfileid || cnid == hfsmp->hfs_jnlinfoblkid) {
                        continue;
                }

                //
                // Just record the cnid of the file for now.  We will modify it separately
                // because we can't modify the catalog while we're scanning it.
                //
                fileids[cur_id_index++] = cnid;
                if (cur_id_index >= NUM_FILE_RESET_IDS) {
                        //
                        // We're over the limit of file-ids so we have to terminate this
                        // scan, go modify all the catalog records, then restart the scan.
                        // This is required because it's not permissible to modify the
                        // catalog while scanning it.
                        //
                        (void) BTScanTerminate(&scanstate, &data, &data, &data);

                        reset_file_ids(hfsmp, fileids, cur_id_index);
                        cleared += cur_id_index;
                        cur_id_index = 0;

                        // restart the scan
                        error = BTScanInitialize(VTOF(HFSTOVCB(hfsmp)->catalogRefNum), 0, 0, 0,
                                                 kCatSearchBufferSize, &scanstate);
                        if (error) {
                                printf("hfs_hotfile_reset: err %d BTScanInit\n", error);
                                goto out;
                        }
                        continue;
                }
        }

        if (cur_id_index) {
                reset_file_ids(hfsmp, fileids, cur_id_index);
                cleared += cur_id_index;
                cur_id_index = 0;
        }

        printf("hfs: cleared HotFileCache related bits on %d files out of %d (dircount %d)\n", cleared, filecount, dircount);

        (void) BTScanTerminate(&scanstate, &data, &data, &data);

out:    
        hfs_free(fileids, NUM_FILE_RESET_IDS * sizeof(uint32_t));
        hfs_free(iterator, sizeof(*iterator));

        //
        // If the hotfile btree exists, delete it.  We need to open
        // it to be able to delete it because we need the hfc_filevp
        // for deletion.
        //
        error = hfc_btree_open_ext(hfsmp, &hfsmp->hfc_filevp, 1);
        if (!error) {
                printf("hfs: hotfile_reset: deleting existing hotfile btree\n");
                hfc_btree_delete(hfsmp);
        }
        
        if (hfsmp->hfc_filevp) {
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                hfsmp->hfc_filevp = NULL;
        }

        hfsmp->hfs_hotfile_blk_adjust = 0;
        hfsmp->hfs_hotfile_freeblks = hfsmp->hfs_hotfile_maxblks;
}


//
// This should ONLY be called by hfs_recording_init() and the special fsctl.
//
// We assume that the hotfile btree is already opened.
//
static int
hfs_hotfile_repin_files(struct hfsmount *hfsmp)
{
        BTreeIterator * iterator = NULL;
        HotFileKey * key;
        filefork_t * filefork;
        int  error = 0;
        int  bt_op;
        enum hfc_stage stage;
        uint32_t pinned_blocks;
        uint32_t num_files=0, nrsrc=0;
        uint32_t total_pinned=0;

        if (!(hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) || !hfsmp->hfc_filevp) {
                //
                // this is only meaningful if we're pinning hotfiles
                // (as opposed to the regular form of hotfiles that
                // get relocated to the hotfile zone)
                //
                return 0;
        }

#if HFC_VERBOSE
        printf("hfs: %s: %s\n", hfsmp->vcbVN, __FUNCTION__);
#endif
        
        if (hfs_lock(VTOC(hfsmp->hfc_filevp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT) != 0) {
                return (EPERM);
        }


        iterator = hfs_mallocz(sizeof(*iterator));

        stage = hfsmp->hfc_stage;
        hfsmp->hfc_stage = HFC_BUSY;

        bt_op = kBTreeFirstRecord;

        key = (HotFileKey*) &iterator->key;

        filefork = VTOF(hfsmp->hfc_filevp);
        int lockflags;

        while (1) {

                lockflags = 0;
                /*
                 * Obtain the first record (ie the coldest one).
                 */
                if (BTIterateRecord(filefork, bt_op, iterator, NULL, NULL) != 0) {
                        // no more records
                        error = 0;
                        break;
                }
                if (key->keyLength != HFC_KEYLENGTH) {
                        // printf("hfs: hotfiles_repin_files: invalid key length %d\n", key->keyLength);
                        error = EFTYPE;
                        break;
                }               
                if (key->temperature == HFC_LOOKUPTAG) {
                        // ran into thread records in the hotfile btree
                        error = 0;
                        break;
                }

        //
                // Just lookup the records in the catalog and pin the direct
                // mapped extents.  Faster than instantiating full vnodes
                // (and thereby thrashing the system vnode cache).
                //
                struct cat_desc fdesc;
                struct cat_attr attr;
                struct cat_fork fork;
        uint8_t forktype = 0;

                lockflags = hfs_systemfile_lock(hfsmp, (SFL_CATALOG | SFL_EXTENTS), HFS_SHARED_LOCK);
        /*
         * Snoop the cnode hash to find out if the item we want is in-core already.
         *
         * We largely expect this function to fail (the items we want are probably not in the hash).
         * we use the special variant which bails out as soon as it finds a vnode (even if it is
         * marked as open-unlinked or actually removed on-disk.  If we find a vnode, then we
         * release the systemfile locks and go through the pin-vnode path instead.
         */
        if (hfs_chash_snoop (hfsmp, key->fileID, 1, NULL, NULL) == 0) {
            pinned_blocks = 0;

            /* unlock immediately and go through the in-core path */
            hfs_systemfile_unlock(hfsmp, lockflags);
                        lockflags = 0;

            error = hfs_getvnode_and_pin (hfsmp, key->fileID, &pinned_blocks);
            if (error) {
                /* if ENOENT, then it was deleted in the catalog. Remove from our hotfiles tracking */
                if (error == ENOENT) {
                    hfc_btree_delete_record(hfsmp, iterator, key);
                }
                /* other errors, just ignore and move on with life */
            }
            else { //!error
                total_pinned += pinned_blocks;
                num_files++;
            }

            goto next;
        }

        /* If we get here, we're still holding the systemfile locks */
                error = cat_idlookup(hfsmp, key->fileID, 1, 0, &fdesc, &attr, &fork);
                if (error) {
                        //
                        // this file system could have been mounted while booted from a
                        // different partition and thus the hotfile btree would not have
                        // been maintained.  thus a file that was hotfile cached could
                        // have been deleted while booted from a different partition which
                        // means we need to delete it from the hotfile btree.
                        //
                        // block accounting is taken care of at the end: we re-assign
                        // hfsmp->hfs_hotfile_freeblks based on how many blocks we actually
                        // pinned.
                        //
                        hfc_btree_delete_record(hfsmp, iterator, key);

                        goto next;
                }

                if (fork.cf_size == 0) {
                        // hmmm, the data is probably in the resource fork (aka a compressed file)
                        error = cat_idlookup(hfsmp, key->fileID, 1, 1, &fdesc, &attr, &fork);
                        if (error) {
                                hfc_btree_delete_record(hfsmp, iterator, key);
                                goto next;
                        }
            forktype = 0xff;
                        nrsrc++;
                }

                pinned_blocks = 0;

        /* Can't release the catalog /extents lock yet, we may need to go find the overflow blocks */
        error = hfs_pin_extent_record (hfsmp, fork.cf_extents, &pinned_blocks);
        if (error) {
            goto next;  //skip to next
        }
                /* add in the blocks from the inline 8 */
        total_pinned += pinned_blocks;
        pinned_blocks = 0;

        /* Could this file have overflow extents? */
        if (fork.cf_extents[kHFSPlusExtentDensity-1].startBlock) {
            /* better pin them, too */
            error = hfs_pin_overflow_extents (hfsmp, key->fileID, forktype, &pinned_blocks);
            if (error) {
                                /* If we fail to pin all of the overflow extents, then just skip to the next file */
                goto next;
            }
        }

                num_files++;
        if (pinned_blocks) {
            /* now add in any overflow also */
            total_pinned += pinned_blocks;
        }

        next:
                if (lockflags) {
                        hfs_systemfile_unlock(hfsmp, lockflags);
                        lockflags = 0;
                }
                bt_op = kBTreeNextRecord;

        } /* end while */

#if HFC_VERBOSE
        printf("hfs: hotfiles_repin_files: re-pinned %d files (nrsrc %d, total pinned %d blks; freeblock %d, maxblocks %d, calculated free: %d)\n",
               num_files, nrsrc, total_pinned, hfsmp->hfs_hotfile_freeblks, hfsmp->hfs_hotfile_maxblks,
              hfsmp->hfs_hotfile_maxblks - total_pinned);
#endif
        //
        // make sure this is accurate based on how many blocks we actually pinned
        //
        hfsmp->hfs_hotfile_freeblks = hfsmp->hfs_hotfile_maxblks - total_pinned;

        hfs_unlock(VTOC(hfsmp->hfc_filevp));

        hfs_free(iterator, sizeof(*iterator));  
        hfsmp->hfc_stage = stage;
        wakeup((caddr_t)&hfsmp->hfc_stage);
        return (error);
}

void
hfs_repin_hotfiles(struct hfsmount *hfsmp)
{
        int error, need_close;
        
        lck_mtx_lock(&hfsmp->hfc_mutex);

        if (hfsmp->hfc_filevp == NULL) {
                error = hfc_btree_open(hfsmp, &hfsmp->hfc_filevp);
                if (!error) {
                        need_close = 1;
                } else {
                        printf("hfs: failed to open the btree err=%d.  Unable to re-pin hotfiles.\n", error);
                        lck_mtx_unlock(&hfsmp->hfc_mutex);
                        return;
                }
        } else {
                need_close = 0;
        }

        hfs_pin_vnode(hfsmp, hfsmp->hfc_filevp, HFS_PIN_IT, NULL);
                        
        hfs_hotfile_repin_files(hfsmp);

        if (need_close) {
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                hfsmp->hfc_filevp = NULL;
        }

        lck_mtx_unlock(&hfsmp->hfc_mutex);
}

/*
 * For a given file ID, find and pin all of its overflow extents to the underlying CS
 * device.  Assumes that the extents overflow b-tree is locked for the duration of this call.
 *
 * Emit the number of blocks pinned in output argument 'pinned'
 *
 * Return success or failure (errno) in return value.
 *
 */
int hfs_pin_overflow_extents (struct hfsmount *hfsmp, uint32_t fileid,
                                     uint8_t forktype, uint32_t *pinned) {

    struct BTreeIterator *ext_iter = NULL;
    ExtentKey *ext_key_ptr = NULL;
    ExtentRecord ext_data;
    FSBufferDescriptor btRecord;
    uint16_t btRecordSize;
    int error = 0;

    uint32_t pinned_blocks = 0;


    ext_iter = hfs_mallocz(sizeof (*ext_iter));

    BTInvalidateHint (ext_iter);
    ext_key_ptr = (ExtentKey*)&ext_iter->key;
    btRecord.bufferAddress = &ext_data;
    btRecord.itemCount = 1;

    /*
     * This is like when you delete a file; we don't actually need most of the search machinery because
     * we are going to need all of the extent records that belong to this file (for a given fork type),
     * so we might as well use a straight-up iterator.
     *
     * Position the B-Tree iterator at the first record with this file ID
     */
    btRecord.itemSize = sizeof (HFSPlusExtentRecord);
    ext_key_ptr->hfsPlus.keyLength = kHFSPlusExtentKeyMaximumLength;
    ext_key_ptr->hfsPlus.forkType = forktype;
    ext_key_ptr->hfsPlus.pad = 0;
    ext_key_ptr->hfsPlus.fileID = fileid;
    ext_key_ptr->hfsPlus.startBlock = 0;

    error = BTSearchRecord (VTOF(hfsmp->hfs_extents_vp), ext_iter, &btRecord, &btRecordSize, ext_iter);
    if (error ==  btNotFound) {
        /* empty b-tree, so that's ok. we'll fall out during error check below. */
        error = 0;
    }

    while (1) {
        uint32_t found_fileid;
        uint32_t pblocks;

        error = BTIterateRecord (VTOF(hfsmp->hfs_extents_vp), kBTreeNextRecord, ext_iter, &btRecord, &btRecordSize);
        if (error) {
            /* swallow it if it's btNotFound, otherwise just bail out */
            if (error == btNotFound)
                error = 0;
            break;
        }

        found_fileid = ext_key_ptr->hfsPlus.fileID;
        /*
         * We only do one fork type at a time. So if either the fork-type doesn't
         * match what we are looking for (resource or data), OR the file id doesn't match
         * which indicates that there's nothing more with this file ID as the key, then bail out
         */
        if ((found_fileid != fileid) || (ext_key_ptr->hfsPlus.forkType != forktype))  {
            error = 0;
            break;
        }

        /* Otherwise, we now have an extent record. Process and pin all of the file extents. */
        pblocks = 0;
        error = hfs_pin_extent_record (hfsmp, ext_data.hfsPlus, &pblocks);

        if (error) {
            break;
        }
        pinned_blocks += pblocks;

        /* if 8th extent is empty, then bail out */
        if (ext_data.hfsPlus[kHFSPlusExtentDensity-1].startBlock == 0) {
            error = 0;
            break;
        }

    } // end extent-getting loop

    /* dump the iterator */
    hfs_free(ext_iter, sizeof(*ext_iter));

    if (error == 0) {
        /*
         * In the event that the file has no overflow extents, pinned_blocks
         * will never be updated, so we'll properly export 0 pinned blocks to caller
         */
        *pinned = pinned_blocks;
    }

    return error;

}


static int
hfs_getvnode_and_pin (struct hfsmount *hfsmp, uint32_t fileid, uint32_t *pinned) {
    struct vnode *vp;
    int error = 0;
    *pinned = 0;
    uint32_t pblocks;

    /*
     * Acquire the vnode for this file.  This returns a locked cnode on success
     */
    error = hfs_vget(hfsmp, fileid, &vp, 0, 0);
    if (error) {
        /* It's possible the file was open-unlinked. In this case, we'll get ENOENT back. */
        return error;
    }

    /*
     * Symlinks that may have been inserted into the hotfile zone during a previous OS are now stuck
     * here.  We do not want to move them.
     */
    if (!vnode_isreg(vp)) {
        hfs_unlock(VTOC(vp));
        vnode_put(vp);
        return EPERM;
    }

    if (!(VTOC(vp)->c_attr.ca_recflags & kHFSFastDevPinnedMask)) {
        hfs_unlock(VTOC(vp));
        vnode_put(vp);
        return EINVAL;
    }

    error = hfs_pin_vnode(hfsmp, vp, HFS_PIN_IT, &pblocks);
    if (error == 0) {
        *pinned = pblocks;
    }

    hfs_unlock(VTOC(vp));
    vnode_put(vp);

    return error;

}

/*
 * Pins an HFS Extent record to the underlying CoreStorage.  Assumes that Catalog & Extents overflow
 * B-trees are held locked, as needed.
 *
 * Returns the number of blocks pinned in the output argument 'pinned'
 *
 * Returns error status (0 || errno) in return value.
 */
static int hfs_pin_extent_record (struct hfsmount *hfsmp, HFSPlusExtentRecord extents, uint32_t *pinned) {
    uint32_t pb = 0;
    int i;
    int error = 0;

        if (pinned == NULL) {
                return EINVAL;
        }
    *pinned = 0;



        /* iterate through the extents */
        for ( i = 0; i < kHFSPlusExtentDensity; i++) {
                if (extents[i].startBlock == 0) {
                        break;
                }

                error = hfs_pin_block_range (hfsmp, HFS_PIN_IT, extents[i].startBlock,
                                extents[i].blockCount);

                if (error) {
                        break;
                }
                pb += extents[i].blockCount;
        }

    *pinned = pb;

        return error;
}

/*
 * Consume an HFS Plus on-disk catalog record and pin its blocks
 * to the underlying CS devnode.
 *
 * NOTE: This is an important distinction!
 * This function takes in an HFSPlusCatalogFile* which is the actual
 * 200-some-odd-byte on-disk representation in the Catalog B-Tree (not
 * one of the run-time structs that we normally use.
 *
 * This assumes that the catalog and extents-overflow btrees
 * are locked, at least in shared mode
 */
static int hfs_pin_catalog_rec (struct hfsmount *hfsmp, HFSPlusCatalogFile *cfp, int rsrc) {
        uint32_t pinned_blocks = 0;
        HFSPlusForkData *forkdata;
        int error = 0;
        uint8_t forktype = 0;

        if (rsrc) {
        forkdata = &cfp->resourceFork;
                forktype = 0xff;
        }
        else {
                forkdata = &cfp->dataFork;
        }

        uint32_t pblocks = 0;

        /* iterate through the inline extents */
        error = hfs_pin_extent_record (hfsmp, forkdata->extents, &pblocks);
        if (error) {
        return error;
        }

        pinned_blocks += pblocks;
    pblocks = 0;

        /* it may have overflow extents */
        if (forkdata->extents[kHFSPlusExtentDensity-1].startBlock != 0) {
        error = hfs_pin_overflow_extents (hfsmp, cfp->fileID, forktype, &pblocks);
        }
    pinned_blocks += pblocks;

        hfsmp->hfs_hotfile_freeblks -= pinned_blocks;

        return error;
}


/*
 *
 */
int
hfs_recording_init(struct hfsmount *hfsmp)
{
        CatalogKey * keyp;
        CatalogRecord * datap;
        u_int32_t  dataSize;
        HFSPlusCatalogFile *filep;
        BTScanState scanstate;
        BTreeIterator * iterator = NULL;
        FSBufferDescriptor  record;
        HotFileKey * key;
        filefork_t * filefork;
        u_int32_t  data;
        struct cat_attr cattr;
        u_int32_t  cnid;
        int error = 0;
        long starting_temp;

        int started_tr = 0;
        int started_scan = 0;

        int inserted = 0;  /* debug variables */
        int filecount = 0;
        int uncacheable = 0;

        /*
         * For now, only the boot volume is supported.
         */
        if ((vfs_flags(HFSTOVFS(hfsmp)) & MNT_ROOTFS) == 0) {
                hfsmp->hfc_stage = HFC_DISABLED;
                return (EPERM);
        }

        /* We grab the HFC mutex even though we're not fully mounted yet, just for orderliness */
        lck_mtx_lock (&hfsmp->hfc_mutex);

        /*
         * Tracking of hot files requires up-to-date access times.
         * So if access time updates are disabled, then we disable
         * hot files, too.
         */
        if (vfs_flags(HFSTOVFS(hfsmp)) & MNT_NOATIME) {
                hfsmp->hfc_stage = HFC_DISABLED;
                lck_mtx_unlock (&hfsmp->hfc_mutex);
                return EPERM;
        }
        
        //
        // Check if we've been asked to suspend operation
        //
        cnid = GetFileInfo(HFSTOVCB(hfsmp), kRootDirID, ".hotfile-suspend", &cattr, NULL);
        if (cnid != 0) {
                printf("hfs: %s: %s: hotfiles explicitly disabled!  remove /.hotfiles-suspend to re-enable\n", hfsmp->vcbVN, __FUNCTION__);
                hfsmp->hfc_stage = HFC_DISABLED;
                lck_mtx_unlock (&hfsmp->hfc_mutex);
                return EPERM;
        }

        //
        // Check if we've been asked to reset our state.
        //
        cnid = GetFileInfo(HFSTOVCB(hfsmp), kRootDirID, ".hotfile-reset", &cattr, NULL);
        if (cnid != 0) {
                hfs_hotfile_reset(hfsmp);
        }

        if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                //
                // Cooperative Fusion (CF) systems use different constants 
                // than traditional hotfile systems.  These were picked after a bit of
                // experimentation - we can cache many more files on the
                // ssd in an CF system and we can do so more rapidly
                // so bump the limits considerably (and turn down the
                // duration so that it doesn't take weeks to adopt all
                // the files).
                //
                hfc_default_file_count = 20000;
                hfc_default_duration   = 300;    // 5min
                hfc_max_file_count     = 50000;
                hfc_max_file_size      = (512ULL * 1024ULL * 1024ULL);
        }

        /*
         * If the Hot File btree exists then metadata zone is ready.
         */
        cnid = GetFileInfo(HFSTOVCB(hfsmp), kRootDirID, HFC_FILENAME, &cattr, NULL);
        if (cnid != 0 && S_ISREG(cattr.ca_mode)) {
                int recreate = 0;
                
                if (hfsmp->hfc_stage == HFC_DISABLED)
                        hfsmp->hfc_stage = HFC_IDLE;
                hfsmp->hfs_hotfile_freeblks = 0;

                if ((hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) && cattr.ca_blocks > 0) {
                        //
                        // make sure the hotfile btree is pinned
                        //
                        error = hfc_btree_open(hfsmp, &hfsmp->hfc_filevp);
                        if (!error) {
                                /* XXX: must fix hfs_pin_vnode too */
                                hfs_pin_vnode(hfsmp, hfsmp->hfc_filevp, HFS_PIN_IT, NULL);
                                
                        } else {
                                printf("hfs: failed to open the btree err=%d.  Recreating hotfile btree.\n", error);
                                recreate = 1;
                        }
                        
                        hfs_hotfile_repin_files(hfsmp);

                        if (hfsmp->hfc_filevp) {
                                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                                hfsmp->hfc_filevp = NULL;
                        }

                } else if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                        // hmmm, the hotfile btree is zero bytes long?  how odd.  let's recreate it.
                        printf("hfs: hotfile btree is zero bytes long?!  recreating it.\n");
                        recreate = 1;
                }

                if (!recreate) {
                        /* don't forget to unlock the mutex */
                        lck_mtx_unlock (&hfsmp->hfc_mutex);
                        return (0);
                } else {
                        //
                        // open the hotfile btree file ignoring errors because
                        // we need the vnode pointer for hfc_btree_delete() to
                        // be able to do its work
                        //
                        error = hfc_btree_open_ext(hfsmp, &hfsmp->hfc_filevp, 1);
                        if (!error) {
                                // and delete it!
                                error = hfc_btree_delete(hfsmp);
                                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                                hfsmp->hfc_filevp = NULL;
                        }
                }
        }

        printf("hfs: %s: %s: creating the hotfile btree\n", hfsmp->vcbVN, __FUNCTION__);
        if (hfs_start_transaction(hfsmp) != 0) {
                lck_mtx_unlock (&hfsmp->hfc_mutex);
                return EINVAL;
        }

        /* B-tree creation must be journaled */
        started_tr = 1;

        error = hfc_btree_create(hfsmp, HFSTOVCB(hfsmp)->blockSize, HFC_DEFAULT_FILE_COUNT);
        if (error) {
#if HFC_VERBOSE
                printf("hfs: Error %d creating hot file b-tree on %s \n", error, hfsmp->vcbVN);
#endif
                goto recording_init_out;
        }

        hfs_end_transaction (hfsmp);
        started_tr = 0;
        /*
         * Do a journal flush + flush track cache. We have to ensure that the async I/Os have been issued to the media
         * before proceeding.
         */
        hfs_flush (hfsmp, HFS_FLUSH_FULL);

        /* now re-start a new transaction */
        if (hfs_start_transaction (hfsmp) != 0) {
                lck_mtx_unlock (&hfsmp->hfc_mutex);
                return EINVAL;
        }
        started_tr = 1;

        /*
         * Open the Hot File B-tree file for writing.
         */
        if (hfsmp->hfc_filevp)
                panic("hfs_recording_init: hfc_filevp exists (vp = %p)", hfsmp->hfc_filevp);

        error = hfc_btree_open(hfsmp, &hfsmp->hfc_filevp);
        if (error) {
#if HFC_VERBOSE
                printf("hfs: Error %d opening hot file b-tree on %s \n", error, hfsmp->vcbVN);
#endif
                goto recording_init_out;
        }

        /*
         * This function performs work similar to namei; we must NOT hold the catalog lock while
         * calling it. This will decorate catalog records as being pinning candidates. (no hotfiles work)
         */
        hfs_setup_default_cf_hotfiles(hfsmp);

        /*
         * now grab the hotfiles b-tree vnode/cnode lock first, as it is not classified as a systemfile.
         */
        if (hfs_lock(VTOC(hfsmp->hfc_filevp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT) != 0) {
                error = EPERM;
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                /* zero it out to avoid pinning later on */
                hfsmp->hfc_filevp = NULL;
                goto recording_init_out;
        }

        iterator = hfs_mallocz(sizeof(*iterator));

        key = (HotFileKey*) &iterator->key;
        key->keyLength = HFC_KEYLENGTH;

        record.bufferAddress = &data;
        record.itemSize = sizeof(u_int32_t);
        record.itemCount = 1;

#if HFC_VERBOSE
        printf("hfs: Evaluating space for \"%s\" metadata zone... (freeblks %d)\n", HFSTOVCB(hfsmp)->vcbVN,
               hfsmp->hfs_hotfile_freeblks);
#endif

        /*
         * Get ready to scan the Catalog file. We explicitly do NOT grab the catalog lock because
         * we're fully single-threaded at the moment (by virtue of being called during mount()),
         * and if we have to grow the hotfile btree, then we would need to grab the catalog lock
         * and if we take a shared lock here, it would deadlock (see <rdar://problem/21486585>)
         *
         * We already started a transaction so we should already be holding the journal lock at this point.
         * Note that we have to hold the journal lock / start a txn BEFORE the systemfile locks.
         */

        error = BTScanInitialize(VTOF(HFSTOVCB(hfsmp)->catalogRefNum), 0, 0, 0,
                               kCatSearchBufferSize, &scanstate);
        if (error) {
                printf("hfs_recording_init: err %d BTScanInit\n", error);

                /* drop the systemfile locks */
                hfs_unlock(VTOC(hfsmp->hfc_filevp));

                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);

                /* zero it out to avoid pinning */
                hfsmp->hfc_filevp = NULL;
                goto recording_init_out;
        }

        started_scan = 1;

        filefork = VTOF(hfsmp->hfc_filevp);

        starting_temp = random() % HF_TEMP_RANGE;

        /*
         * Visit all the catalog btree leaf records. We have to hold the catalog lock to do this.
         *
         * NOTE: The B-Tree scanner reads from the media itself. Under normal circumstances it would be
         * fine to simply use b-tree routines to read blocks that correspond to b-tree nodes, because the
         * block cache is going to ensure you always get the cached copy of a block (even if a journal
         * txn has modified one of those blocks).  That is NOT true when
         * using the scanner.  In particular, it will always read whatever is on-disk. So we have to ensure
         * that the journal has flushed and that the async I/Os to the metadata files have been issued.
         */
        for (;;) {
                error = BTScanNextRecord(&scanstate, 0, (void **)&keyp, (void **)&datap, &dataSize);
                if (error) {
                        if (error == btNotFound)
                                error = 0;
                        else
                                printf("hfs_recording_init: err %d BTScanNext\n", error);
                        break;
                }
                if ((datap->recordType != kHFSPlusFileRecord) ||
                    (dataSize != sizeof(HFSPlusCatalogFile))) {
                        continue;
                }
                filep = (HFSPlusCatalogFile *)datap;
                filecount++;

                if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                        if (filep->flags & kHFSDoNotFastDevPinMask) {
                                uncacheable++;
                        }

                        //
                        // If the file does not have the FastDevPinnedMask set, we
                        // can ignore it and just go to the next record.
                        //
                        if ((filep->flags & kHFSFastDevPinnedMask) == 0) {
                                continue;
                        }
                } else if (filep->dataFork.totalBlocks == 0) {
                        continue;
                }

                /*
                 * On a regular hdd, any file that has blocks inside
                 * the hot file space is recorded for later eviction.
                 *
                 * For now, resource forks are ignored.
                 *
                 * We don't do this on CF systems as there is no real
                 * hotfile area - we just pin/unpin blocks belonging to
                 * interesting files.
                 */
                if (!(hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) && !hotextents(hfsmp, &filep->dataFork.extents[0])) {
                        continue;
                }
                cnid = filep->fileID;

                /* Skip over journal files and the hotfiles B-Tree file. */
                if (cnid == hfsmp->hfs_jnlfileid
                        || cnid == hfsmp->hfs_jnlinfoblkid
                        || cnid == VTOC(hfsmp->hfc_filevp)->c_fileid) {
                        continue;
                }
                /*
                 * XXX - need to skip quota files as well.
                 */

                uint32_t temp;

                if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                        int rsrc = 0;

                        temp = (uint32_t)starting_temp++;
                        if (filep->flags & kHFSAutoCandidateMask) {
                                temp += MAX_NORMAL_TEMP;
                        }

                        /* use the data fork by default */
                        if (filep->dataFork.totalBlocks == 0) {
                                /*
                 * but if empty, switch to rsrc as its likely
                 * a compressed file
                 */
                                rsrc = 1;
                        }

                        error =  hfs_pin_catalog_rec (hfsmp, filep, rsrc);
                        if (error)
                                break;

                } else {
                        temp = HFC_MINIMUM_TEMPERATURE;
                }

                /* Insert a hot file entry. */
                key->keyLength   = HFC_KEYLENGTH;
                key->temperature = temp;
                key->fileID      = cnid;
                key->forkType    = 0;
                data = 0x3f3f3f3f;
                error = BTInsertRecord(filefork, iterator, &record, record.itemSize);
                if (error) {
                        printf("hfs_recording_init: BTInsertRecord failed %d (fileid %d)\n", error, key->fileID);
                        error = MacToVFSError(error);
                        break;
                }

                /* Insert the corresponding thread record. */
                key->keyLength = HFC_KEYLENGTH;
                key->temperature = HFC_LOOKUPTAG;
                key->fileID = cnid;
                key->forkType = 0;
                data = temp;
                error = BTInsertRecord(filefork, iterator, &record, record.itemSize);
                if (error) {
                        printf("hfs_recording_init: BTInsertRecord failed %d (fileid %d)\n", error, key->fileID);
                        error = MacToVFSError(error);
                        break;
                }
                inserted++;
        } // end catalog iteration loop

        save_btree_user_info(hfsmp);
        (void) BTFlushPath(filefork);

recording_init_out:

        /* Unlock first, then pin after releasing everything else */
        if (hfsmp->hfc_filevp) {
                hfs_unlock (VTOC(hfsmp->hfc_filevp));
        }

        if (started_scan) {
                (void) BTScanTerminate (&scanstate, &data, &data, &data);
        }

        if (started_tr) {
                hfs_end_transaction(hfsmp);
        }

#if HFC_VERBOSE
        printf("hfs: %d files identified out of %d (freeblocks is now: %d)\n", inserted, filecount, hfsmp->hfs_hotfile_freeblks);
        if (uncacheable) {
                printf("hfs: %d files were marked as uncacheable\n", uncacheable);
        }
#endif
        
        if (iterator)
                hfs_free(iterator, sizeof(*iterator));

        if (hfsmp->hfc_filevp) {
                if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                        hfs_pin_vnode(hfsmp, hfsmp->hfc_filevp, HFS_PIN_IT, NULL);
                }
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                hfsmp->hfc_filevp = NULL;
        }

        if (error == 0)
                hfsmp->hfc_stage = HFC_IDLE;

        /* Finally, unlock the HFC mutex */
        lck_mtx_unlock (&hfsmp->hfc_mutex);

        return (error);
}

/*
 * Use sync to perform ocassional background work.
 */
int
hfs_hotfilesync(struct hfsmount *hfsmp, vfs_context_t ctx)
{
        if (hfsmp->hfc_stage) {
                struct timeval tv;

                lck_mtx_lock(&hfsmp->hfc_mutex);

                switch (hfsmp->hfc_stage) {
                case HFC_IDLE:
                        (void) hfs_recording_start(hfsmp);
                        break;
        
                case HFC_RECORDING:
                        microtime(&tv);
                        if (tv.tv_sec > hfsmp->hfc_timeout)
                                (void) hfs_recording_stop(hfsmp);
                        break;
        
                case HFC_EVICTION:
                        (void) hotfiles_evict(hfsmp, ctx);
                        break;
        
                case HFC_ADOPTION:
                        (void) hotfiles_adopt(hfsmp);
                        break;
                default:
                        break;
                }

                lck_mtx_unlock(&hfsmp->hfc_mutex);
        }
        return (0);
}

/*
 * Add a hot file to the recording list.
 *
 * This can happen when a hot file gets reclaimed or at the
 * end of the recording period for any active hot file.
 *
 * NOTE: Since both the data and resource fork can  be hot,
 * there can be two entries for the same file id.
 *
 * Note: the cnode is locked on entry.
 */
int
hfs_addhotfile(struct vnode *vp)
{
        hfsmount_t *hfsmp;
        int error;

        hfsmp = VTOHFS(vp);
        if (hfsmp->hfc_stage != HFC_RECORDING)
                return (0);

        lck_mtx_lock(&hfsmp->hfc_mutex);
        error = hfs_addhotfile_internal(vp);
        lck_mtx_unlock(&hfsmp->hfc_mutex);
        return (error);
}

static int
hf_ignore_process(const char *pname, size_t maxlen)
{
        if (   strncmp(pname, "mds", maxlen) == 0
            || strncmp(pname, "mdworker", maxlen) == 0
            || strncmp(pname, "mds_stores", maxlen) == 0
            || strncmp(pname, "makewhatis", maxlen) == 0) {
                return 1;
        }

        return 0;
        
}

static int
hfs_addhotfile_internal(struct vnode *vp)
{
        hotfile_data_t *hotdata;
        hotfile_entry_t *entry;
        hfsmount_t *hfsmp;
        cnode_t *cp;
        filefork_t *ffp;
        u_int32_t temperature;

        hfsmp = VTOHFS(vp);
        if (hfsmp->hfc_stage != HFC_RECORDING)
                return (0);

        /* 
         * Only regular files are eligible for hotfiles addition. 
         * 
         * Symlinks were previously added to the list and may exist in 
         * extant hotfiles regions, but no new ones will be added, and no
         * symlinks will now be relocated/evicted from the hotfiles region.
         */
        if (!vnode_isreg(vp) || vnode_issystem(vp)) {
                return (0);
        }

        /* Skip resource forks for now. */
        if (VNODE_IS_RSRC(vp)) {
                return (0);
        }
        if ((hotdata = hfsmp->hfc_recdata) == NULL) {
                return (0);
        }
        ffp = VTOF(vp);
        cp = VTOC(vp);

        if (cp->c_attr.ca_recflags & (kHFSFastDevPinnedMask|kHFSDoNotFastDevPinMask)) {
                // it's already a hotfile or can't be a hotfile...
                return 0;
        }

        if (vnode_isdir(vp) || vnode_issystem(vp) || (cp->c_flag & (C_DELETED | C_NOEXISTS))) {
                return 0;
        }

        if ((hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) && vnode_isfastdevicecandidate(vp)) {
                //
                // On cooperative fusion (CF) systems we have different criteria for whether something
                // can be pinned to the ssd.
                //
                if (cp->c_flag & (C_DELETED|C_NOEXISTS)) {
                        //
                        // dead files are definitely not worth caching
                        //
                        return 0;
                } else if (ffp->ff_blocks == 0 && !(cp->c_bsdflags & UF_COMPRESSED) && !(cp->c_attr.ca_recflags & kHFSFastDevCandidateMask)) {
                        //
                        // empty files aren't worth caching but compressed ones might be, as are 
                        // newly created files that live in WorthCaching directories... 
                        //
                        return 0;
                }

                char pname[256];
                pname[0] = '\0';
                proc_selfname(pname, sizeof(pname));
                if (hf_ignore_process(pname, sizeof(pname))) {
                        // ignore i/o's from certain system daemons 
                        return 0;
                }

                temperature = cp->c_fileid;        // in memory we just keep it sorted by file-id
        } else {
                // the normal hard drive based hotfile checks
                if ((ffp->ff_bytesread == 0) ||
                    (ffp->ff_blocks == 0) ||
                    (ffp->ff_size == 0) ||
                    (ffp->ff_blocks > hotdata->maxblocks) ||
                    (cp->c_bsdflags & (UF_NODUMP | UF_COMPRESSED)) ||
                    (cp->c_atime < hfsmp->hfc_timebase)) {
                        return (0);
                }

                temperature = ffp->ff_bytesread / ffp->ff_size;
                if (temperature < hotdata->threshold) {
                        return (0);
                }
        }

        /*
         * If there is room or this file is hotter than
         * the coldest one then add it to the list.
         *
         */
        if ((hotdata->activefiles < hfsmp->hfc_maxfiles) ||
            (hotdata->coldest == NULL) ||
            (temperature >= hotdata->coldest->temperature)) {
                ++hotdata->refcount;
                entry = hf_getnewentry(hotdata);
                entry->temperature = temperature;
                entry->fileid = cp->c_fileid;
                //
                // if ffp->ff_blocks is zero, it might be compressed so make sure we record
                // that there's at least one block.
                //
                entry->blocks = ffp->ff_blocks ? ffp->ff_blocks : 1;   
                if (hf_insert(hotdata, entry) == EEXIST) {
                        // entry is already present, don't need to add it again
                        entry->right = hotdata->freelist;
                        hotdata->freelist = entry;
                }
                --hotdata->refcount;
        }

        return (0);
}

/*
 * Remove a hot file from the recording list.
 *
 * This can happen when a hot file becomes
 * an active vnode (active hot files are
 * not kept in the recording list until the
 * end of the recording period).
 *
 * Note: the cnode is locked on entry.
 */
int
hfs_removehotfile(struct vnode *vp)
{
        hotfile_data_t *hotdata;
        hfsmount_t *hfsmp;
        cnode_t *cp;
        filefork_t *ffp;
        u_int32_t temperature;

        hfsmp = VTOHFS(vp);
        if (hfsmp->hfc_stage != HFC_RECORDING)
                return (0);

        if ((!vnode_isreg(vp)) || vnode_issystem(vp)) {
                return (0);
        }

        ffp = VTOF(vp);
        cp = VTOC(vp);

        if ((ffp->ff_bytesread == 0) || (ffp->ff_blocks == 0) ||
            (ffp->ff_size == 0) || (cp->c_atime < hfsmp->hfc_timebase)) {
                return (0);
        }

        lck_mtx_lock(&hfsmp->hfc_mutex);
        if (hfsmp->hfc_stage != HFC_RECORDING)
                goto out;
        if ((hotdata = hfsmp->hfc_recdata) == NULL)
                goto out;

        temperature = ffp->ff_bytesread / ffp->ff_size;
        if (temperature < hotdata->threshold)
                goto out;

        if (hotdata->coldest && (temperature >= hotdata->coldest->temperature)) {
                ++hotdata->refcount;
                hf_delete(hotdata, VTOC(vp)->c_fileid, temperature);
                --hotdata->refcount;
        }
out:
        lck_mtx_unlock(&hfsmp->hfc_mutex);
        return (0);
}

int
hfs_hotfile_deleted(__unused struct vnode *vp)
{
#if 1
        return 0;
#else   
        //
        // XXXdbg - this code, while it would work, would introduce a huge inefficiency
        //          to deleting files as the way it's written would require us to open
        //          the hotfile btree on every open, delete two records in it and then
        //          close the hotfile btree (which involves more writes).
        //
        //          We actually can be lazy about deleting hotfile records for files
        //          that get deleted.  When it's time to evict things, if we encounter
        //          a record that references a dead file (i.e. a fileid which no
        //          longer exists), the eviction code will remove the records.  Likewise
        //          the code that scans the HotFile B-Tree at boot time to re-pin files
        //          will remove dead records.
        //

        hotfile_data_t *hotdata;
        hfsmount_t *hfsmp;
        cnode_t *cp;
        filefork_t *filefork;
        u_int32_t temperature;
        BTreeIterator * iterator = NULL;
        FSBufferDescriptor record;
        HotFileKey *key;
        u_int32_t data;
        int error=0;

        cp = VTOC(vp);
        if (cp == NULL || !(cp->c_attr.ca_recflags & kHFSFastDevPinnedMask)) {
                return 0;
        }

        hfsmp = VTOHFS(vp);
        if (!(hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN)) {
                return 0;
        }
        
        if (hfc_btree_open(hfsmp, &hfsmp->hfc_filevp) != 0 || hfsmp->hfc_filevp == NULL) {
                // either there is no hotfile info or it's damaged
                return EINVAL;
        }
        
        filefork = VTOF(hfsmp->hfc_filevp);
        if (filefork == NULL) {
                return 0;
        }

        iterator = hfs_mallocz(sizeof(*iterator));

        key = (HotFileKey*) &iterator->key;

        record.bufferAddress = &data;
        record.itemSize = sizeof(u_int32_t);
        record.itemCount = 1;

        key->keyLength = HFC_KEYLENGTH;
        key->temperature = HFC_LOOKUPTAG;
        key->fileID = cp->c_fileid;
        key->forkType = 0;

        lck_mtx_lock(&hfsmp->hfc_mutex);
        (void) BTInvalidateHint(iterator);
        if (BTSearchRecord(filefork, iterator, &record, NULL, iterator) == 0) {
                temperature = key->temperature;
                hfc_btree_delete_record(hfsmp, iterator, key);
        } else {
                //printf("hfs: hotfile_deleted: did not find fileid %d\n", cp->c_fileid);
                error = ENOENT;
        }

        if ((hotdata = hfsmp->hfc_recdata) != NULL) {
                // just in case, also make sure it's removed from the in-memory list as well
                ++hotdata->refcount;
                hf_delete(hotdata, cp->c_fileid, cp->c_fileid);
                --hotdata->refcount;
        }

        lck_mtx_unlock(&hfsmp->hfc_mutex);
        hfs_free(iterator, sizeof(*iterator));

        hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
        
        return error;
#endif
}

int
hfs_hotfile_adjust_blocks(struct vnode *vp, int64_t num_blocks)
{
        hfsmount_t *hfsmp;
        
        if (vp == NULL) {
                return 0;
        }

        hfsmp = VTOHFS(vp);

        if (!(hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) || num_blocks == 0 || vp == NULL) {
                return 0;
        }

        //
        // if file is not HotFileCached or it has the CanNotHotFile cache
        // bit set then there is nothing to do
        //
        if (!(VTOC(vp)->c_attr.ca_recflags & kHFSFastDevPinnedMask) || (VTOC(vp)->c_attr.ca_recflags & kHFSDoNotFastDevPinMask)) {
                // it's not a hot file or can't be one so don't bother tracking
                return 0;
        }
        
        OSAddAtomic(num_blocks, &hfsmp->hfs_hotfile_blk_adjust);

        return (0);
}

//
// Assumes hfsmp->hfc_mutex is LOCKED
//
static int
hfs_hotfile_cur_freeblks(hfsmount_t *hfsmp)
{
        if (hfsmp->hfc_stage < HFC_IDLE) {
                return 0;
        }
        
        int cur_blk_adjust = hfsmp->hfs_hotfile_blk_adjust;   // snap a copy of this value

        if (cur_blk_adjust) {
                OSAddAtomic(-cur_blk_adjust, &hfsmp->hfs_hotfile_blk_adjust);
                hfsmp->hfs_hotfile_freeblks += cur_blk_adjust;
        }

        return hfsmp->hfs_hotfile_freeblks;
}


/*
 *========================================================================
 *                     HOT FILE MAINTENANCE ROUTINES
 *========================================================================
 */

static int
hotfiles_collect_callback(struct vnode *vp, __unused void *cargs)
{
        if ((vnode_isreg(vp)) && !vnode_issystem(vp))
                (void) hfs_addhotfile_internal(vp);

        return (VNODE_RETURNED);
}

/*
 * Add all active hot files to the recording list.
 */
static int
hotfiles_collect(struct hfsmount *hfsmp)
{
        struct mount *mp = HFSTOVFS(hfsmp);

        if (vfs_busy(mp, LK_NOWAIT))
                return (0);

        /*
         * hotfiles_collect_callback will be called for each vnode
         * hung off of this mount point
         * the vnode will be
         * properly referenced and unreferenced around the callback
         */
        vnode_iterate(mp, 0, hotfiles_collect_callback, (void *)NULL);

        vfs_unbusy(mp);

        return (0);
}


/*
 * Update the data of a btree record
 * This is called from within BTUpdateRecord.
 */
static int
update_callback(const HotFileKey *key, u_int32_t *data, u_int32_t *state)
{
        if (key->temperature == HFC_LOOKUPTAG)
                *data = *state;
        return (0);
}

/*
 * Identify files already in hot area.
 */
static int
hotfiles_refine(struct hfsmount *hfsmp)
{
        BTreeIterator * iterator = NULL;
        struct mount *mp;
        filefork_t * filefork;
        hotfilelist_t  *listp;
        FSBufferDescriptor  record;
        HotFileKey * key;
        u_int32_t  data;
        int  i;
        int  error = 0;

        if ((listp = hfsmp->hfc_filelist) == NULL)
                return (0);     

        if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                // on ssd's we don't refine the temperature since the
                // replacement algorithm is simply random
                return 0;
        }

        mp = HFSTOVFS(hfsmp);

        iterator = hfs_mallocz(sizeof(*iterator));

        key = (HotFileKey*) &iterator->key;

        record.bufferAddress = &data;
        record.itemSize = sizeof(u_int32_t);
        record.itemCount = 1;

        if (hfs_start_transaction(hfsmp) != 0) {
            error = EINVAL;
            goto out;
        } 
        if (hfs_lock(VTOC(hfsmp->hfc_filevp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT) != 0) {
                error = EPERM;
                goto out1;
        }
        filefork = VTOF(hfsmp->hfc_filevp);

        for (i = 0; i < listp->hfl_count; ++i) {
                /*
                 * Check if entry (thread) is already in hot area.
                 */
                key->keyLength = HFC_KEYLENGTH;
                key->temperature = HFC_LOOKUPTAG;
                key->fileID = listp->hfl_hotfile[i].hf_fileid;
                key->forkType = 0;
                (void) BTInvalidateHint(iterator);
                if (BTSearchRecord(filefork, iterator, &record, NULL, iterator) != 0) {
                        continue;  /* not in hot area, so skip */
                }

                /*
                 * Update thread entry with latest temperature.
                 */
                error = BTUpdateRecord(filefork, iterator,
                                       (IterateCallBackProcPtr)update_callback,
                                      &listp->hfl_hotfile[i].hf_temperature);
                if (error) {
                        printf("hfs: hotfiles_refine: BTUpdateRecord failed %d (file %d)\n", error, key->fileID);
                        error = MacToVFSError(error);
                        //      break;
                }
                /*
                 * Re-key entry with latest temperature.
                 */
                key->keyLength = HFC_KEYLENGTH;
                key->temperature = data;
                key->fileID = listp->hfl_hotfile[i].hf_fileid;
                key->forkType = 0;
                /* Pick up record data. */
                (void) BTInvalidateHint(iterator);
                (void) BTSearchRecord(filefork, iterator, &record, NULL, iterator);
                error = BTDeleteRecord(filefork, iterator);
                if (error) {
                        printf("hfs: hotfiles_refine: BTDeleteRecord failed %d (file %d)\n", error, key->fileID);
                        error = MacToVFSError(error);
                        break;
                }
                key->keyLength = HFC_KEYLENGTH;
                key->temperature = listp->hfl_hotfile[i].hf_temperature;
                key->fileID = listp->hfl_hotfile[i].hf_fileid;
                key->forkType = 0;
                error = BTInsertRecord(filefork, iterator, &record, record.itemSize);
                if (error) {
                        printf("hfs: hotfiles_refine: BTInsertRecord failed %d (file %d)\n", error, key->fileID);
                        error = MacToVFSError(error);
                        break;
                }
                /*
                 * Invalidate this entry in the list.
                 */
                listp->hfl_hotfile[i].hf_temperature = 0;
                listp->hfl_totalblocks -= listp->hfl_hotfile[i].hf_blocks;
                
        } /* end for */

        (void) BTFlushPath(filefork);
        hfs_unlock(VTOC(hfsmp->hfc_filevp));

out1:
        hfs_end_transaction(hfsmp);
out:
        if (iterator)
                hfs_free(iterator, sizeof(*iterator));  
        return (error);
}

/*
 * Move new hot files into hot area.
 *
 * Requires that the hfc_mutex be held.
 */
static int
hotfiles_adopt(struct hfsmount *hfsmp)
{
        BTreeIterator * iterator = NULL;
        struct vnode *vp;
        filefork_t * filefork;
        hotfilelist_t  *listp;
        FSBufferDescriptor  record;
        HotFileKey * key;
        u_int32_t  data;
        enum hfc_stage stage;
        int  fileblocks;
        int  blksmoved;
        int  i;
        int  last;
        int  error = 0;
        int  startedtrans = 0;
        //
        // all files in a given adoption phase have a temperature
        // that starts at a random value and then increases linearly.
        // the idea is that during eviction, files that were adopted
        // together will be evicted together
        //
        long starting_temp = random() % HF_TEMP_RANGE;
        long temp_adjust = 0;

        if ((listp = hfsmp->hfc_filelist) == NULL)
                return (0);     

        if (hfsmp->hfc_stage != HFC_ADOPTION) {
                return (EBUSY);
        }
        if (hfs_lock(VTOC(hfsmp->hfc_filevp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT) != 0) {
                return (EPERM);
        }

        iterator = hfs_mallocz(sizeof(*iterator));

#if HFC_VERBOSE
                printf("hfs:%s: hotfiles_adopt: (hfl_next: %d, hotfile start/end block: %d - %d; max/free: %d/%d; maxfiles: %d)\n",
                       hfsmp->vcbVN,
                       listp->hfl_next,
                       hfsmp->hfs_hotfile_start, hfsmp->hfs_hotfile_end,
                       hfsmp->hfs_hotfile_maxblks, hfsmp->hfs_hotfile_freeblks, hfsmp->hfc_maxfiles);
#endif

        stage = hfsmp->hfc_stage;
        hfsmp->hfc_stage = HFC_BUSY;

        blksmoved = 0;
        last = listp->hfl_next + HFC_FILESPERSYNC;
        if (last > listp->hfl_count)
                last = listp->hfl_count;

        key = (HotFileKey*) &iterator->key;
        key->keyLength = HFC_KEYLENGTH;

        record.bufferAddress = &data;
        record.itemSize = sizeof(u_int32_t);
        record.itemCount = 1;

        filefork = VTOF(hfsmp->hfc_filevp);

        for (i = listp->hfl_next; (i < last) && (blksmoved < HFC_BLKSPERSYNC); ++i) {
                /*
                 * Skip entries that aren't going to work.
                 */
                if (listp->hfl_hotfile[i].hf_temperature == 0) {
                        //printf("hfs: zero temp on file-id %d\n", listp->hfl_hotfile[i].hf_fileid);
                        listp->hfl_next++;
                        continue;
                }
                if (listp->hfl_hotfile[i].hf_fileid == VTOC(hfsmp->hfc_filevp)->c_fileid) {
                        //printf("hfs: cannot adopt the hotfile b-tree itself! (file-id %d)\n", listp->hfl_hotfile[i].hf_fileid);
                        listp->hfl_next++;
                        continue;
                }
                if (listp->hfl_hotfile[i].hf_fileid < kHFSFirstUserCatalogNodeID) {
                        //printf("hfs: cannot adopt system files (file-id %d)\n", listp->hfl_hotfile[i].hf_fileid);
                        listp->hfl_next++;
                        continue;
                }

                /*
                 * Acquire a vnode for this file.
                 */
                error = hfs_vget(hfsmp, listp->hfl_hotfile[i].hf_fileid, &vp, 0, 0);
                if (error) {
                        //printf("failed to get fileid %d (err %d)\n", listp->hfl_hotfile[i].hf_fileid, error);
                        if (error == ENOENT) {
                                error = 0;
                                listp->hfl_next++;
                                continue;  /* stale entry, go to next */
                        }
                        break;
                }

                //printf("hfs: examining hotfile entry w/fileid %d, temp %d, blocks %d (HotFileCached: %s)\n",
                //       listp->hfl_hotfile[i].hf_fileid, listp->hfl_hotfile[i].hf_temperature,
                //       listp->hfl_hotfile[i].hf_blocks,
                //       (VTOC(vp)->c_attr.ca_recflags & kHFSFastDevPinnedMask) ? "YES" : "NO");

                if (!vnode_isreg(vp)) {
                        /* Symlinks are ineligible for adoption into the hotfile zone.  */
                        //printf("hfs: hotfiles_adopt: huh, not a file %d (%d)\n", listp->hfl_hotfile[i].hf_fileid, VTOC(vp)->c_cnid);
                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        listp->hfl_hotfile[i].hf_temperature = 0;
                        listp->hfl_next++;
                        continue;  /* stale entry, go to next */
                }
                if (   (VTOC(vp)->c_flag & (C_DELETED | C_NOEXISTS))
                    || (!(hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) && hotextents(hfsmp, &VTOF(vp)->ff_extents[0]))
                    || (VTOC(vp)->c_attr.ca_recflags & (kHFSFastDevPinnedMask|kHFSDoNotFastDevPinMask))) {
                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        listp->hfl_hotfile[i].hf_temperature = 0;
                        listp->hfl_next++;
                        listp->hfl_totalblocks -= listp->hfl_hotfile[i].hf_blocks;
                        continue;  /* stale entry, go to next */
                }

                fileblocks = VTOF(vp)->ff_blocks;

                //
                // for CF, if the file is empty (and not compressed) or it is too large,
                // do not try to pin it.  (note: if fileblocks == 0 but the file is marked
                // as compressed, we may still be able to cache it).
                //
                if ((hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) &&
                    ((fileblocks == 0 && !(VTOC(vp)->c_bsdflags & UF_COMPRESSED)) ||
                     (unsigned int)fileblocks > (HFC_MAXIMUM_FILESIZE / (uint64_t)HFSTOVCB(hfsmp)->blockSize))) {
                        // don't try to cache something too large or that's zero-bytes

                        vnode_clearfastdevicecandidate(vp);    // turn off the fast-dev-candidate flag so we don't keep trying to cache it.

                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        listp->hfl_hotfile[i].hf_temperature = 0;
                        listp->hfl_next++;
                        listp->hfl_totalblocks -= listp->hfl_hotfile[i].hf_blocks;
                        continue;  /* entry is too big, just carry on with the next guy */
                }

                //
                // If a file is not an autocandidate (i.e. it's a user-tagged file desirous of
                // being hotfile cached) but it is already bigger than 4 megs, don't bother
                // hotfile caching it.  Note that if a user tagged file starts small, gets
                // adopted and then grows over time we will allow it to grow bigger than 4 megs
                // which is intentional for things like the Mail or Photos database files which
                // grow slowly over time and benefit from being on the FastDevice.
                //
                if ((hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) &&
                    !(VTOC(vp)->c_attr.ca_recflags & kHFSAutoCandidateMask) && 
                    (VTOC(vp)->c_attr.ca_recflags & kHFSFastDevCandidateMask) && 
                    (unsigned int)fileblocks > ((4*1024*1024) / (uint64_t)HFSTOVCB(hfsmp)->blockSize)) {

                        vnode_clearfastdevicecandidate(vp);    // turn off the fast-dev-candidate flag so we don't keep trying to cache it.

                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        listp->hfl_hotfile[i].hf_temperature = 0;
                        listp->hfl_next++;
                        listp->hfl_totalblocks -= listp->hfl_hotfile[i].hf_blocks;
                        continue;  /* entry is too big, just carry on with the next guy */
                }

                if (fileblocks > hfs_hotfile_cur_freeblks(hfsmp)) {
                        //
                        // No room for this file.  Although eviction should have made space
                        // it's best that we check here as well since writes to existing
                        // hotfiles may have eaten up space since we performed eviction
                        //
                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        listp->hfl_next++;
                        listp->hfl_totalblocks -= fileblocks;
                        continue;  /* entry too big, go to next */
                }
                
                if ((blksmoved > 0) &&
                    (blksmoved + fileblocks) > HFC_BLKSPERSYNC) {
                        //
                        // we've done enough work, let's be nice to the system and
                        // stop until the next iteration
                        //
                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        break;  /* adopt this entry the next time around */
                }

                //
                // The size of data for a hot file record is 4 bytes. The data
                // stored in hot file record is not really meaningful. However
                // to aid debugging, we store first four bytes of the file name
                // or the ASCII text "????"
                //
                if (VTOC(vp)->c_desc.cd_nameptr && (VTOC(vp)->c_desc.cd_namelen > 0)) {
                        size_t max_len;

                        max_len = sizeof(u_int32_t);
                        if (max_len > (unsigned)VTOC(vp)->c_desc.cd_namelen)
                                max_len = VTOC(vp)->c_desc.cd_namelen;

                        memcpy(&data, VTOC(vp)->c_desc.cd_nameptr, max_len);
                } else
                        data = 0x3f3f3f3f;


                if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                        //
                        // For CF we pin the blocks belonging to the file
                        // to the "fast" (aka ssd) media
                        //
                        uint32_t pinned_blocks;

                        if (vnode_isautocandidate(vp)) {
                                VTOC(vp)->c_attr.ca_recflags |= kHFSAutoCandidateMask;
                        }
                        if (VTOC(vp)->c_attr.ca_recflags & kHFSAutoCandidateMask) {
                                //
                                // this moves auto-cached files to the higher tier 
                                // of "temperatures" which means they are less likely
                                // to get evicted (user selected hotfiles will get
                                // evicted first in the theory that they change more
                                // frequently compared to system files)
                                //
                                temp_adjust = MAX_NORMAL_TEMP;
                        } else {
                                temp_adjust = 0;
                        }

                        hfs_unlock(VTOC(vp));  // don't need an exclusive lock for this
                        hfs_lock(VTOC(vp), HFS_SHARED_LOCK, HFS_LOCK_ALLOW_NOEXISTS);

                        error = hfs_pin_vnode(hfsmp, vp, HFS_PIN_IT, &pinned_blocks);

                        fileblocks = pinned_blocks;

                        // go back to an exclusive lock since we're going to modify the cnode again
                        hfs_unlock(VTOC(vp));
                        hfs_lock(VTOC(vp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_ALLOW_NOEXISTS);
                } else {
                        //
                        // Old style hotfiles moves the data to the center (aka "hot")
                        // region of the disk
                        //
                        error = hfs_relocate(vp, hfsmp->hfs_hotfile_start, kauth_cred_get(), current_proc());
                }

                if (!error) {
                        VTOC(vp)->c_attr.ca_recflags |= kHFSFastDevPinnedMask;
                        VTOC(vp)->c_flag |= C_MODIFIED;
                } else if ((hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) && error == EALREADY) {
                        //
                        // If hfs_pin_vnode() returned EALREADY then this file is not
                        // ever able to be hotfile cached the normal way.  This can
                        // happen with compressed files which have their data stored
                        // in an extended attribute.  We flag them so that we won't
                        // bother to try and hotfile cache them again the next time
                        // they're read.
                        //
                        VTOC(vp)->c_attr.ca_recflags |= kHFSDoNotFastDevPinMask;
                        VTOC(vp)->c_flag |= C_MODIFIED;
                }

                hfs_unlock(VTOC(vp));
                vnode_put(vp);
                if (error) {
#if HFC_VERBOSE
                        if (error != EALREADY) {
                                printf("hfs: hotfiles_adopt: could not relocate file %d (err %d)\n", listp->hfl_hotfile[i].hf_fileid, error);
                        }
#endif

                        if (last < listp->hfl_count) {
                                last++;
                        }
                        /* Move on to next item. */
                        listp->hfl_next++;
                        continue;
                }
                /* Keep hot file free space current. */
                hfsmp->hfs_hotfile_freeblks -= fileblocks;
                listp->hfl_totalblocks -= fileblocks;
                
                /* Insert hot file entry */
                key->keyLength   = HFC_KEYLENGTH;

                if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                        //
                        // The "temperature" for a CF hotfile is simply a random
                        // number that we sequentially increment for each file in
                        // the set of files we're currently adopting.  This has the
                        // nice property that all of the files we pin to the ssd
                        // in the current phase will sort together in the hotfile
                        // btree.  When eviction time comes we will evict them
                        // together as well.  This gives the eviction phase temporal
                        // locality - things written together get evicted together
                        // which is what ssd's like.
                        //
                        listp->hfl_hotfile[i].hf_temperature = (uint32_t)temp_adjust + starting_temp++;
                }

                key->temperature = listp->hfl_hotfile[i].hf_temperature;
                key->fileID      = listp->hfl_hotfile[i].hf_fileid;
                key->forkType    = 0;

                /* Start a new transaction before calling BTree code. */
                if (hfs_start_transaction(hfsmp) != 0) {
                    error = EINVAL;
                    break;
                }
                startedtrans = 1;

                error = BTInsertRecord(filefork, iterator, &record, record.itemSize);
                if (error) {
                        int orig_error = error;
                        error = MacToVFSError(error);
                        printf("hfs: hotfiles_adopt:1: BTInsertRecord failed %d/%d (fileid %d)\n", error, orig_error, key->fileID);
                        stage = HFC_IDLE;
                        break;
                }

                /* Insert thread record */
                key->keyLength = HFC_KEYLENGTH;
                key->temperature = HFC_LOOKUPTAG;
                key->fileID = listp->hfl_hotfile[i].hf_fileid;
                key->forkType = 0;
                data = listp->hfl_hotfile[i].hf_temperature;
                error = BTInsertRecord(filefork, iterator, &record, record.itemSize);
                if (error) {
                        int orig_error = error;
                        error = MacToVFSError(error);
                        printf("hfs: hotfiles_adopt:2: BTInsertRecord failed %d/%d (fileid %d)\n", error, orig_error, key->fileID);
                        stage = HFC_IDLE;
                        break;
                } else {
                        (void) BTFlushPath(filefork);
                        blksmoved += fileblocks;
                }

                listp->hfl_next++;
                if (listp->hfl_next >= listp->hfl_count) {
                        break;
                }

                /* Transaction complete. */
                if (startedtrans) {
                    hfs_end_transaction(hfsmp);
                    startedtrans = 0;
                }

                if (hfs_hotfile_cur_freeblks(hfsmp) <= 0) {
#if HFC_VERBOSE
                        printf("hfs: hotfiles_adopt: free space exhausted (%d)\n", hfsmp->hfs_hotfile_freeblks);
#endif
                        break;
                }
        } /* end for */

#if HFC_VERBOSE
        printf("hfs: hotfiles_adopt: [%d] adopted %d blocks (%d files left)\n", listp->hfl_next, blksmoved, listp->hfl_count - i);
#endif
        if (!startedtrans) {
                // start a txn so we'll save the btree summary info
                if (hfs_start_transaction(hfsmp) == 0) {
                        startedtrans = 1;
                }
        }               

        /* Finish any outstanding transactions. */
        if (startedtrans) {
                save_btree_user_info(hfsmp);

                (void) BTFlushPath(filefork);
                hfs_end_transaction(hfsmp);
                startedtrans = 0;
        }
        hfs_unlock(VTOC(hfsmp->hfc_filevp));

        if ((listp->hfl_next >= listp->hfl_count) || (hfsmp->hfs_hotfile_freeblks <= 0)) {
#if HFC_VERBOSE
                printf("hfs: hotfiles_adopt: all done relocating %d files\n", listp->hfl_count);
                printf("hfs: hotfiles_adopt: %d blocks free in hot file band\n", hfsmp->hfs_hotfile_freeblks);
#endif
                stage = HFC_IDLE;
        }
        hfs_free(iterator, sizeof(*iterator));

        if (stage != HFC_ADOPTION && hfsmp->hfc_filevp) {
                (void) hfc_btree_close(hfsmp, hfsmp->hfc_filevp);
                hfsmp->hfc_filevp = NULL;
        }
        hfsmp->hfc_stage = stage;
        wakeup((caddr_t)&hfsmp->hfc_stage);
        return (error);
}

/*
 * Reclaim space by evicting the coldest files.
 *
 * Requires that the hfc_mutex be held.
 */
static int
hotfiles_evict(struct hfsmount *hfsmp, vfs_context_t ctx)
{
        BTreeIterator * iterator = NULL;
        struct vnode *vp;
        HotFileKey * key;
        filefork_t * filefork;
        hotfilelist_t  *listp;
        enum hfc_stage stage;
        u_int32_t savedtemp;
        int  blksmoved;
        int  filesmoved;
        int  fileblocks;
        int  error = 0;
        int  startedtrans = 0;
        int  bt_op;

        if (hfsmp->hfc_stage != HFC_EVICTION) {
                return (EBUSY);
        }

        if ((listp = hfsmp->hfc_filelist) == NULL)
                return (0);     

        if (hfs_lock(VTOC(hfsmp->hfc_filevp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT) != 0) {
                return (EPERM);
        }

#if HFC_VERBOSE
                printf("hfs:%s: hotfiles_evict (hotfile start/end block: %d - %d; max/free: %d/%d; maxfiles: %d)\n",
                       hfsmp->vcbVN,
                       hfsmp->hfs_hotfile_start, hfsmp->hfs_hotfile_end,
                       hfsmp->hfs_hotfile_maxblks, hfsmp->hfs_hotfile_freeblks, hfsmp->hfc_maxfiles);
#endif

        iterator = hfs_mallocz(sizeof(*iterator));

        stage = hfsmp->hfc_stage;
        hfsmp->hfc_stage = HFC_BUSY;

        filesmoved = blksmoved = 0;
        bt_op = kBTreeFirstRecord;

        key = (HotFileKey*) &iterator->key;

        filefork = VTOF(hfsmp->hfc_filevp);

#if HFC_VERBOSE
        printf("hfs: hotfiles_evict: reclaim blks %d\n", listp->hfl_reclaimblks);
#endif
        
        while (listp->hfl_reclaimblks > 0 &&
               blksmoved < HFC_BLKSPERSYNC &&
               filesmoved < HFC_FILESPERSYNC) {

                /*
                 * Obtain the first record (ie the coldest one).
                 */
                if (BTIterateRecord(filefork, bt_op, iterator, NULL, NULL) != 0) {
#if HFC_VERBOSE
                        printf("hfs: hotfiles_evict: no more records\n");
#endif
                        error = 0;
                        stage = HFC_ADOPTION;
                        break;
                }
                if (key->keyLength != HFC_KEYLENGTH) {
                        printf("hfs: hotfiles_evict: invalid key length %d\n", key->keyLength);
                        error = EFTYPE;
                        break;
                }               
                if (key->temperature == HFC_LOOKUPTAG) {
#if HFC_VERBOSE
                        printf("hfs: hotfiles_evict: ran into thread records\n");
#endif
                        error = 0;
                        stage = HFC_ADOPTION;
                        break;
                }

                // Jump straight to delete for some files...
                if (key->fileID == VTOC(hfsmp->hfc_filevp)->c_fileid
                        || key->fileID == hfsmp->hfs_jnlfileid
                        || key->fileID == hfsmp->hfs_jnlinfoblkid
                        || key->fileID < kHFSFirstUserCatalogNodeID) {
                        goto delete;
                }

                /*
                 * Aquire the vnode for this file.
                 */
                error = hfs_vget(hfsmp, key->fileID, &vp, 0, 0);
                if (error) {
                        if (error == ENOENT) {
                                goto delete;  /* stale entry, go to next */
                        } else {
                                printf("hfs: hotfiles_evict: err %d getting file %d\n",
                                       error, key->fileID);
                        }
                        break;
                }

                /* 
                 * Symlinks that may have been inserted into the hotfile zone during a previous OS are now stuck 
                 * here.  We do not want to move them. 
                 */
                if (!vnode_isreg(vp)) {
                        //printf("hfs: hotfiles_evict: huh, not a file %d\n", key->fileID);
                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        goto delete;  /* invalid entry, go to next */
                }

                fileblocks = VTOF(vp)->ff_blocks;
                if ((blksmoved > 0) &&
                    (blksmoved + fileblocks) > HFC_BLKSPERSYNC) {
                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        break;
                }
                /*
                 * Make sure file is in the hot area.
                 */
                if (!hotextents(hfsmp, &VTOF(vp)->ff_extents[0]) && !(VTOC(vp)->c_attr.ca_recflags & kHFSFastDevPinnedMask)) {
#if HFC_VERBOSE
                        printf("hfs: hotfiles_evict: file %d isn't hot!\n", key->fileID);
#endif
                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        goto delete;  /* stale entry, go to next */
                }
                
                /*
                 * Relocate file out of hot area.  On cooperative fusion (CF) that just 
                 * means un-pinning the data from the ssd.  For traditional hotfiles that means moving
                 * the file data out of the hot region of the disk.
                 */
                if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                        uint32_t pinned_blocks;
                        
                        hfs_unlock(VTOC(vp));  // don't need an exclusive lock for this
                        hfs_lock(VTOC(vp), HFS_SHARED_LOCK, HFS_LOCK_ALLOW_NOEXISTS);

                        error = hfs_pin_vnode(hfsmp, vp, HFS_UNPIN_IT, &pinned_blocks);
                        fileblocks = pinned_blocks;

                        if (!error) {
                                // go back to an exclusive lock since we're going to modify the cnode again
                                hfs_unlock(VTOC(vp));
                                hfs_lock(VTOC(vp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_ALLOW_NOEXISTS);
                        }
                } else {
                        error = hfs_relocate(vp, HFSTOVCB(hfsmp)->nextAllocation, vfs_context_ucred(ctx), vfs_context_proc(ctx));
                }
                if (error) {
#if HFC_VERBOSE
                        printf("hfs: hotfiles_evict: err %d relocating file %d\n", error, key->fileID);
#endif
                        hfs_unlock(VTOC(vp));
                        vnode_put(vp);
                        bt_op = kBTreeNextRecord;
                        goto next;  /* go to next */
                } else {
                        VTOC(vp)->c_attr.ca_recflags &= ~kHFSFastDevPinnedMask;
                        VTOC(vp)->c_flag |= C_MODIFIED;
                }

                //
                // We do not believe that this call to hfs_fsync() is
                // necessary and it causes a journal transaction
                // deadlock so we are removing it.
                //
                // (void) hfs_fsync(vp, MNT_WAIT, 0, p);

                hfs_unlock(VTOC(vp));
                vnode_put(vp);

                hfsmp->hfs_hotfile_freeblks += fileblocks;
                listp->hfl_reclaimblks -= fileblocks;
                if (listp->hfl_reclaimblks < 0)
                        listp->hfl_reclaimblks = 0;
                blksmoved += fileblocks;
                filesmoved++;
delete:
                /* Start a new transaction before calling BTree code. */
                if (hfs_start_transaction(hfsmp) != 0) {
                    error = EINVAL;
                    break;
                }
                startedtrans = 1;

                error = BTDeleteRecord(filefork, iterator);
                if (error) {
                        error = MacToVFSError(error);
                        break;
                }
                savedtemp = key->temperature;
                key->temperature = HFC_LOOKUPTAG;
                error = BTDeleteRecord(filefork, iterator);
                if (error) {
                        error = MacToVFSError(error);
                        break;
                }
                key->temperature = savedtemp;
next:
                (void) BTFlushPath(filefork);

                /* Transaction complete. */
                if (startedtrans) {
                        hfs_end_transaction(hfsmp);
                        startedtrans = 0;
                }

        } /* end while */

#if HFC_VERBOSE
        printf("hfs: hotfiles_evict: moved %d files (%d blks, %d to go)\n", filesmoved, blksmoved, listp->hfl_reclaimblks);
#endif
        /* Finish any outstanding transactions. */
        if (startedtrans) {
                save_btree_user_info(hfsmp);

                (void) BTFlushPath(filefork);
                hfs_end_transaction(hfsmp);
                startedtrans = 0;
        }
        hfs_unlock(VTOC(hfsmp->hfc_filevp));

        /*
         * Move to next stage when finished.
         */
        if (listp->hfl_reclaimblks <= 0) {
                stage = HFC_ADOPTION;
#if HFC_VERBOSE
                printf("hfs: hotfiles_evict: %d blocks free in hot file band\n", hfsmp->hfs_hotfile_freeblks);
#endif
        }
        hfs_free(iterator, sizeof(*iterator));  
        hfsmp->hfc_stage = stage;
        wakeup((caddr_t)&hfsmp->hfc_stage);
        return (error);
}

/*
 * Age the existing records in the hot files b-tree.
 */
static int
hotfiles_age(struct hfsmount *hfsmp)
{
        BTreeInfoRec  btinfo;
        BTreeIterator * iterator = NULL;
        BTreeIterator * prev_iterator;
        FSBufferDescriptor  record;
        FSBufferDescriptor  prev_record;
        HotFileKey * key;
        HotFileKey * prev_key;
        filefork_t * filefork;
        u_int32_t  data;
        u_int32_t  prev_data;
        u_int32_t  newtemp;
        int  error;
        int  i;
        int  numrecs;
        int  aged = 0;
        u_int16_t  reclen;


        if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                //
                // hotfiles don't age on CF
                //
                return 0;
        }

        iterator = hfs_mallocz(2 * sizeof(*iterator));

        key = (HotFileKey*) &iterator->key;

        prev_iterator = &iterator[1];
        prev_key = (HotFileKey*) &prev_iterator->key;

        record.bufferAddress = &data;
        record.itemSize = sizeof(data);
        record.itemCount = 1;
        prev_record.bufferAddress = &prev_data;
        prev_record.itemSize = sizeof(prev_data);
        prev_record.itemCount = 1;

        /*
         * Capture b-tree changes inside a transaction
         */
        if (hfs_start_transaction(hfsmp) != 0) {
            error = EINVAL;
            goto out2;
        } 
        if (hfs_lock(VTOC(hfsmp->hfc_filevp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT) != 0) {
                error = EPERM;
                goto out1;
        }
        filefork = VTOF(hfsmp->hfc_filevp);

        error = BTGetInformation(filefork, 0, &btinfo);
        if (error) {
                error = MacToVFSError(error);
                goto out;
        }
        if (btinfo.numRecords < 2) {
                error = 0;
                goto out;
        }
        
        /* Only want 1st half of leaf records */
        numrecs = (btinfo.numRecords /= 2) - 1;

        error = BTIterateRecord(filefork, kBTreeFirstRecord, iterator, &record, &reclen);
        if (error) {
                printf("hfs_agehotfiles: BTIterateRecord: %d\n", error);
                error = MacToVFSError(error);
                goto out;
        }
        bcopy(iterator, prev_iterator, sizeof(BTreeIterator));
        prev_data = data;

        for (i = 0; i < numrecs; ++i) {
                error = BTIterateRecord(filefork, kBTreeNextRecord, iterator, &record, &reclen);
                if (error == 0) {
                        if (key->temperature < prev_key->temperature) {
                                printf("hfs_agehotfiles: out of order keys!\n");
                                error = EFTYPE;
                                break;
                        }
                        if (reclen != sizeof(data)) {
                                printf("hfs_agehotfiles: invalid record length %d\n", reclen);
                                error = EFTYPE;
                                break;
                        }
                        if (key->keyLength != HFC_KEYLENGTH) {
                                printf("hfs_agehotfiles: invalid key length %d\n", key->keyLength);
                                error = EFTYPE;
                                break;
                        }
                } else if ((error == fsBTEndOfIterationErr || error == fsBTRecordNotFoundErr) &&
                    (i == (numrecs - 1))) {
                        error = 0;
                } else if (error) {
                        printf("hfs_agehotfiles: %d of %d BTIterateRecord: %d\n", i, numrecs, error);
                        error = MacToVFSError(error);
                        break;
                }
                if (prev_key->temperature == HFC_LOOKUPTAG) {
#if HFC_VERBOSE 
                        printf("hfs_agehotfiles: ran into thread record\n");
#endif
                        error = 0;
                        break;
                }
                error = BTDeleteRecord(filefork, prev_iterator);
                if (error) {
                        printf("hfs_agehotfiles: BTDeleteRecord failed %d (file %d)\n", error, prev_key->fileID);
                        error = MacToVFSError(error);
                        break;
                }
                
                /* Age by halving the temperature (floor = 4) */
                newtemp = MAX(prev_key->temperature >> 1, 4);
                prev_key->temperature = newtemp;
        
                error = BTInsertRecord(filefork, prev_iterator, &prev_record, prev_record.itemSize);
                if (error) {
                        printf("hfs_agehotfiles: BTInsertRecord failed %d (file %d)\n", error, prev_key->fileID);
                        error = MacToVFSError(error);
                        break;
                }
                ++aged;
                /*
                 * Update thread entry with latest temperature.
                 */
                prev_key->temperature = HFC_LOOKUPTAG;
                error = BTUpdateRecord(filefork, prev_iterator,
                                (IterateCallBackProcPtr)update_callback,
                                &newtemp);
                if (error) {
                        printf("hfs_agehotfiles: %d of %d BTUpdateRecord failed %d (file %d, %d)\n",
                                i, numrecs, error, prev_key->fileID, newtemp);
                        error = MacToVFSError(error);
                //      break;
                }

                bcopy(iterator, prev_iterator, sizeof(BTreeIterator));
                prev_data = data;

        } /* end for */

#if HFC_VERBOSE 
        if (error == 0)
                printf("hfs_agehotfiles: aged %d records out of %d\n", aged, btinfo.numRecords);
#endif
        (void) BTFlushPath(filefork);
out:
        hfs_unlock(VTOC(hfsmp->hfc_filevp));
out1:
        hfs_end_transaction(hfsmp);
out2:
        if (iterator)
                hfs_free(iterator, 2 * sizeof(*iterator));
        return (error);
}

/*
 * Return true if any blocks (or all blocks if all is true)
 * are contained in the hot file region.
 */
static int
hotextents(struct hfsmount *hfsmp, HFSPlusExtentDescriptor * extents)
{
        u_int32_t  b1, b2;
        int  i;
        int  inside = 0;

        for (i = 0; i < kHFSPlusExtentDensity; ++i) {
                b1 = extents[i].startBlock;
                if (b1 == 0)
                        break;
                b2 = b1 + extents[i].blockCount - 1;
                if ((b1 >= hfsmp->hfs_hotfile_start &&
                     b2 <= hfsmp->hfs_hotfile_end) ||
                    (b1 < hfsmp->hfs_hotfile_end && 
                     b2 > hfsmp->hfs_hotfile_end)) {
                        inside = 1;
                        break;
                }
        }
        return (inside);
}


/*
 *========================================================================
 *                       HOT FILE B-TREE ROUTINES
 *========================================================================
 */

/*
 * Open the hot files b-tree for writing.
 *
 * On successful exit the vnode has a reference but not an iocount.
 */
static int
hfc_btree_open(struct hfsmount *hfsmp, struct vnode **vpp)
{
        return hfc_btree_open_ext(hfsmp, vpp, 0);
}

static int
hfc_btree_open_ext(struct hfsmount *hfsmp, struct vnode **vpp, int ignore_btree_errs)
{
        proc_t p;
        struct vnode *vp;
        struct cat_desc  cdesc;
        struct cat_attr  cattr;
        struct cat_fork  cfork;
        static char filename[] = HFC_FILENAME;
        int  error;
        int  retry = 0;
        int lockflags;
        int newvnode_flags = 0;

        *vpp = NULL;
        p = current_proc();

        bzero(&cdesc, sizeof(cdesc));
        cdesc.cd_parentcnid = kRootDirID;
        cdesc.cd_nameptr = (const u_int8_t *)filename;
        cdesc.cd_namelen = strlen(filename);

        lockflags = hfs_systemfile_lock(hfsmp, SFL_CATALOG, HFS_SHARED_LOCK);

        error = cat_lookup(hfsmp, &cdesc, 0, 0, &cdesc, &cattr, &cfork, NULL);

        hfs_systemfile_unlock(hfsmp, lockflags);

        if (error) {
                printf("hfs: hfc_btree_open: cat_lookup error %d\n", error);
                return (error);
        }
again:
        cdesc.cd_flags |= CD_ISMETA;
        error = hfs_getnewvnode(hfsmp, NULL, NULL, &cdesc, 0, &cattr, 
                                                        &cfork, &vp, &newvnode_flags);
        if (error) {
                printf("hfs: hfc_btree_open: hfs_getnewvnode error %d\n", error);
                cat_releasedesc(&cdesc);
                return (error);
        }
        if (!vnode_issystem(vp)) {
#if HFC_VERBOSE
                printf("hfs: hfc_btree_open: file has UBC, try again\n");
#endif
                hfs_unlock(VTOC(vp));
                vnode_recycle(vp);
                vnode_put(vp);
                if (retry++ == 0)
                        goto again;
                else
                        return (EBUSY);
        }

        /* Open the B-tree file for writing... */
        error = BTOpenPath(VTOF(vp), (KeyCompareProcPtr) hfc_comparekeys);      
        if (error) {
                if (!ignore_btree_errs) {
                        printf("hfs: hfc_btree_open: BTOpenPath error %d; filesize %lld\n", error, VTOF(vp)->ff_size);
                        error = MacToVFSError(error);
                } else {
                        error = 0;
                }
        }

        hfs_unlock(VTOC(vp));
        if (error == 0) {
                *vpp = vp;
                vnode_ref(vp);  /* keep a reference while its open */
        }
        vnode_put(vp);

        if (!vnode_issystem(vp))
                panic("hfs: hfc_btree_open: not a system file (vp = %p)", vp);

        HotFilesInfo hotfileinfo;

        if (error == 0 && (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN)) {
                if ((BTGetUserData(VTOF(vp), &hotfileinfo, sizeof(hotfileinfo)) == 0) && (SWAP_BE32 (hotfileinfo.magic) == HFC_MAGIC)) {
                        if (hfsmp->hfs_hotfile_freeblks == 0) {
                                hfsmp->hfs_hotfile_freeblks = hfsmp->hfs_hotfile_maxblks - SWAP_BE32 (hotfileinfo.usedblocks);
                        }

                        hfs_hotfile_cur_freeblks(hfsmp);        // factors in any adjustments that happened at run-time
                }
        }
        
        return (error);
}

/*
 * Close the hot files b-tree.
 *
 * On entry the vnode has a reference.
 */
static int
hfc_btree_close(struct hfsmount *hfsmp, struct vnode *vp)
{
        proc_t p = current_proc();
        int  error = 0;


        if (hfsmp->jnl) {
            hfs_flush(hfsmp, HFS_FLUSH_JOURNAL);
        }

        if (vnode_get(vp) == 0) {
                error = hfs_lock(VTOC(vp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT);
                if (error == 0) {
                        (void) hfs_fsync(vp, MNT_WAIT, 0, p);
                        error = BTClosePath(VTOF(vp));
                        hfs_unlock(VTOC(vp));
                }
                vnode_rele(vp);
                vnode_recycle(vp);
                vnode_put(vp);
        }
        
        return (error);
}

//
// Assumes that hfsmp->hfc_filevp points to the hotfile btree vnode
// (i.e. you called hfc_btree_open() ahead of time)
//
static int
hfc_btree_delete_record(struct hfsmount *hfsmp, BTreeIterator *iterator, HotFileKey *key)
{
        int error;
        filefork_t *filefork=VTOF(hfsmp->hfc_filevp);

        /* Start a new transaction before calling BTree code. */
        if (hfs_start_transaction(hfsmp) != 0) {
                return EINVAL;
        }

        error = BTDeleteRecord(filefork, iterator);
        if (error) {
                error = MacToVFSError(error);
                printf("hfs: failed to delete record for file-id %d : err %d\n", key->fileID, error);
                goto out;
        }

        int savedtemp;
        savedtemp = key->temperature;
        key->temperature = HFC_LOOKUPTAG;
        error = BTDeleteRecord(filefork, iterator);
        if (error) {
                error = MacToVFSError(error);
                printf("hfs:2: failed to delete record for file-id %d : err %d\n", key->fileID, error);
        }
        key->temperature = savedtemp;

        (void) BTFlushPath(filefork);

out:
        /* Transaction complete. */
        hfs_end_transaction(hfsmp);

        return error;
}

//
// You have to have already opened the hotfile btree so
// that hfsmp->hfc_filevp is filled in.
//
static int
hfc_btree_delete(struct hfsmount *hfsmp)
{
        struct vnode *dvp = NULL;
        vfs_context_t ctx = vfs_context_current();
        struct vnode_attr va;
        static char filename[] = HFC_FILENAME;
        int  error;

        error = hfs_vfs_root(HFSTOVFS(hfsmp), &dvp, ctx);
        if (error) {
                return (error);
        }

        struct componentname cname = {
                .cn_nameiop = DELETE,
                .cn_flags = ISLASTCN,
                .cn_pnbuf = filename,
                .cn_pnlen = sizeof(filename),
                .cn_nameptr = filename,
                .cn_namelen = strlen(filename),
        };

        VATTR_INIT(&va);
        VATTR_SET(&va, va_type, VREG);
        VATTR_SET(&va, va_mode, S_IFREG | S_IRUSR | S_IWUSR);
        VATTR_SET(&va, va_uid, 0);
        VATTR_SET(&va, va_gid, 0);

        if (hfs_start_transaction(hfsmp) != 0) {
            error = EINVAL;
            goto out;
        } 

    struct vnop_remove_args ap = {
        .a_dvp = dvp,
        .a_vp  = hfsmp->hfc_filevp,
        .a_cnp = &cname,
    };

    error = hfs_vnop_remove(&ap);
        if (error) {
                printf("hfs: error %d removing HFBT on %s\n", error, HFSTOVCB(hfsmp)->vcbVN);
        }

        hfs_end_transaction(hfsmp);

out:
        if (dvp) {
                vnode_put(dvp);
                dvp = NULL;
        }

        return 0;
}




/*
 *  Create a hot files btree file.
 *
 */
static int
hfc_btree_create(struct hfsmount *hfsmp, unsigned int nodesize, unsigned int entries)
{
        struct vnode *dvp = NULL;
        struct vnode *vp = NULL;
        struct cnode *cp = NULL;
        vfs_context_t ctx = vfs_context_current();
        struct vnode_attr va;
        static char filename[] = HFC_FILENAME;
        int  error;

        if (hfsmp->hfc_filevp)
                panic("hfs: hfc_btree_create: hfc_filevp exists (vp = %p)", hfsmp->hfc_filevp);

        error = hfs_vfs_root(HFSTOVFS(hfsmp), &dvp, ctx);
        if (error) {
                return (error);
        }

        struct componentname cname = {
                .cn_nameiop = CREATE,
                .cn_flags = ISLASTCN,
                .cn_pnbuf = filename,
                .cn_pnlen = sizeof(filename),
                .cn_nameptr = filename,
                .cn_namelen = strlen(filename)
        };

        VATTR_INIT(&va);
        VATTR_SET(&va, va_type, VREG);
        VATTR_SET(&va, va_mode, S_IFREG | S_IRUSR | S_IWUSR);
        VATTR_SET(&va, va_uid, 0);
        VATTR_SET(&va, va_gid, 0);

        if (hfs_start_transaction(hfsmp) != 0) {
                vnode_put(dvp);
                return EINVAL;
        }

        /* call ourselves directly, ignore the higher-level VFS file creation code */

    struct vnop_create_args ap = {
        .a_dvp = dvp,
        .a_vpp = &vp,
        .a_cnp = &cname,
        .a_vap = &va
    };

    error = hfs_vnop_create(&ap);
        if (error) {
                printf("hfs: error %d creating HFBT on %s\n", error, HFSTOVCB(hfsmp)->vcbVN);
                goto out;
        }
        if (dvp) {
                vnode_put(dvp);
                dvp = NULL;
        }
        if ((error = hfs_lock(VTOC(vp), HFS_EXCLUSIVE_LOCK, HFS_LOCK_DEFAULT))) {
                goto out;
        }
        cp = VTOC(vp);

        /* Don't use non-regular files or files with links. */
        if (!vnode_isreg(vp) || cp->c_linkcount != 1) {
                error = EFTYPE;
                goto out;
        }

        printf("hfs: created HFBT on %s\n", HFSTOVCB(hfsmp)->vcbVN);

        if (VTOF(vp)->ff_size < nodesize) {
                caddr_t  buffer;
                u_int16_t *index;
                u_int16_t  offset;
                BTNodeDescriptor  *ndp;
                BTHeaderRec  *bthp;
                HotFilesInfo *hotfileinfo;
                int  nodecnt;
                int  filesize;
                int  entirespernode;

                /*
                 * Mark it invisible (truncate will pull these changes).
                 */
                ((FndrFileInfo *)&cp->c_finderinfo[0])->fdFlags |=
                        SWAP_BE16 (kIsInvisible + kNameLocked);

                buffer = hfs_mallocz(nodesize);
                index = (u_int16_t *)buffer;
        
                entirespernode = (nodesize - sizeof(BTNodeDescriptor) - 2) /
                                 (sizeof(HotFileKey) + 6);
                nodecnt = 2 + howmany(entries * 2, entirespernode);
                nodecnt = roundup(nodecnt, 8);
                filesize = nodecnt * nodesize;
        
                /* FILL IN THE NODE DESCRIPTOR:  */
                ndp = (BTNodeDescriptor *)buffer;
                ndp->kind = kBTHeaderNode;
                ndp->numRecords = SWAP_BE16 (3);
                offset = sizeof(BTNodeDescriptor);
                index[(nodesize / 2) - 1] = SWAP_BE16 (offset);
        
                /* FILL IN THE HEADER RECORD:  */
                bthp = (BTHeaderRec *)((u_int8_t *)buffer + offset);
                bthp->nodeSize     = SWAP_BE16 (nodesize);
                bthp->totalNodes   = SWAP_BE32 (filesize / nodesize);
                bthp->freeNodes    = SWAP_BE32 (nodecnt - 1);
                bthp->clumpSize    = SWAP_BE32 (filesize);
                bthp->btreeType    = kUserBTreeType; /* non-metadata */
                bthp->attributes  |= SWAP_BE32 (kBTBigKeysMask);
                bthp->maxKeyLength = SWAP_BE16 (HFC_KEYLENGTH);
                offset += sizeof(BTHeaderRec);
                index[(nodesize / 2) - 2] = SWAP_BE16 (offset);
        
                /* FILL IN THE USER RECORD:  */
                hotfileinfo = (HotFilesInfo *)((u_int8_t *)buffer + offset);
                hotfileinfo->magic       = SWAP_BE32 (HFC_MAGIC);
                hotfileinfo->version     = SWAP_BE32 (HFC_VERSION);
                hotfileinfo->duration    = SWAP_BE32 (HFC_DEFAULT_DURATION);
                hotfileinfo->timebase    = 0;
                hotfileinfo->timeleft    = 0;
                hotfileinfo->threshold   = SWAP_BE32 (HFC_MINIMUM_TEMPERATURE);
                hotfileinfo->maxfileblks = SWAP_BE32 (HFC_MAXIMUM_FILESIZE / HFSTOVCB(hfsmp)->blockSize);
                if (hfsmp->hfs_flags & HFS_CS_HOTFILE_PIN) {
                        if (hfsmp->hfs_hotfile_freeblks == 0) {
                                hfsmp->hfs_hotfile_freeblks = hfsmp->hfs_hotfile_maxblks;
                        }
                        hotfileinfo->usedblocks = SWAP_BE32 (hfsmp->hfs_hotfile_maxblks - hfsmp->hfs_hotfile_freeblks);
                } else {
                        hotfileinfo->maxfilecnt  = SWAP_BE32 (HFC_DEFAULT_FILE_COUNT);
                }
                strlcpy((char *)hotfileinfo->tag, hfc_tag,
                        sizeof hotfileinfo->tag);
                offset += kBTreeHeaderUserBytes;
                index[(nodesize / 2) - 3] = SWAP_BE16 (offset);
        
                /* FILL IN THE MAP RECORD (only one node in use). */
                *((u_int8_t *)buffer + offset) = 0x80;
                offset += nodesize - sizeof(BTNodeDescriptor) - sizeof(BTHeaderRec)
                                   - kBTreeHeaderUserBytes - (4 * sizeof(int16_t));
                index[(nodesize / 2) - 4] = SWAP_BE16 (offset);

                vnode_setnoflush(vp);
                error = hfs_truncate(vp, (off_t)filesize, IO_NDELAY, 0, ctx);
                if (error) {
                        printf("hfs: error %d growing HFBT on %s\n", error, HFSTOVCB(hfsmp)->vcbVN);
                        goto out;
                }
                cp->c_flag |= C_ZFWANTSYNC;
                cp->c_zftimeout = 1;
                
                if (error == 0) {
                        struct vnop_write_args args;
                        uio_t auio;

                        auio = uio_create(1, 0, UIO_SYSSPACE, UIO_WRITE);
                        uio_addiov(auio, (uintptr_t)buffer, nodesize);

                        args.a_desc = &vnop_write_desc;
                        args.a_vp = vp;
                        args.a_uio = auio;
                        args.a_ioflag = 0;
                        args.a_context = ctx;

                        hfs_unlock(cp);
                        cp = NULL;

                        error = hfs_vnop_write(&args);
                        if (error)
                                printf("hfs: error %d writing HFBT on %s\n", error, HFSTOVCB(hfsmp)->vcbVN);

                        uio_free(auio);
                }
                hfs_free(buffer, nodesize);
        }
out:
        hfs_end_transaction(hfsmp);
        if (dvp) {
                vnode_put(dvp);
        }
        if (vp) {
                if (cp)
                        hfs_unlock(cp);
                vnode_recycle(vp);
                vnode_put(vp);
        }
        return (error);
}

/*
 * Compare two hot file b-tree keys.
 *
 * Result:   +n  search key > trial key
 *            0  search key = trial key
 *           -n  search key < trial key
 */
static int
hfc_comparekeys(HotFileKey *searchKey, HotFileKey *trialKey)
{
        /*
         * Compared temperatures first.
         */
        if (searchKey->temperature == trialKey->temperature) {
                /*
                 * Temperatures are equal so compare file ids.
                 */
                if (searchKey->fileID == trialKey->fileID) {
                        /*
                         * File ids are equal so compare fork types.
                         */
                        if (searchKey->forkType == trialKey->forkType) {
                                return (0);
                        } else if (searchKey->forkType > trialKey->forkType) {
                                return (1);
                        }
                } else if (searchKey->fileID > trialKey->fileID) {
                        return (1);
                }
        } else if (searchKey->temperature > trialKey->temperature) {
                return (1);
        }
        
        return (-1);
}


/*
 *========================================================================
 *               HOT FILE DATA COLLECTING ROUTINES
 *========================================================================
 */

/*
 * Lookup a hot file entry in the tree.
 */
#if HFC_DEBUG
static hotfile_entry_t *
hf_lookup(hotfile_data_t *hotdata, u_int32_t fileid, u_int32_t temperature)
{
        hotfile_entry_t *entry = hotdata->rootentry;

        while (entry &&
               entry->temperature != temperature &&
               entry->fileid != fileid) {

                if (temperature > entry->temperature)
                        entry = entry->right;
                else if (temperature < entry->temperature)
                        entry = entry->left;
                else if (fileid > entry->fileid)
                        entry = entry->right;
                else
                        entry = entry->left;
        }
        return (entry);
}
#endif

/*
 * Insert a hot file entry into the tree.
 */
static int
hf_insert(hotfile_data_t *hotdata, hotfile_entry_t *newentry) 
{
        hotfile_entry_t *entry = hotdata->rootentry;
        u_int32_t fileid = newentry->fileid;
        u_int32_t temperature = newentry->temperature;

        if (entry == NULL) {
                hotdata->rootentry = newentry;
                hotdata->coldest = newentry;
                hotdata->activefiles++;
                return 0;
        }

        while (entry) {
                if (temperature > entry->temperature) {
                        if (entry->right) {
                                entry = entry->right;
                        } else {
                                entry->right = newentry;
                                break;
                        }
                } else if (temperature < entry->temperature) {
                        if (entry->left) {
                                entry = entry->left;
                        } else {
                                entry->left = newentry;
                                break;
                        }
                } else if (fileid > entry->fileid) { 
                        if (entry->right) {
                                entry = entry->right;
                        } else {
                                if (entry->fileid != fileid)
                                        entry->right = newentry;
                                break;
                        }
                } else { 
                        if (entry->left) {
                                entry = entry->left;
                        } else {
                                if (entry->fileid != fileid) {
                                        entry->left = newentry;
                                } else {
                                        return EEXIST;
                                }
                                break;
                        }
                }
        }

        hotdata->activefiles++;
        return 0;
}

/*
 * Find the coldest entry in the tree.
 */
static hotfile_entry_t *
hf_coldest(hotfile_data_t *hotdata)
{
        hotfile_entry_t *entry = hotdata->rootentry;

        if (entry) {
                while (entry->left)
                        entry = entry->left;
        }
        return (entry);
}

/*
 * Find the hottest entry in the tree.
 */
static hotfile_entry_t *
hf_hottest(hotfile_data_t *hotdata)
{
        hotfile_entry_t *entry = hotdata->rootentry;

        if (entry) {
                while (entry->right)
                        entry = entry->right;
        }
        return (entry);
}

/*
 * Delete a hot file entry from the tree.
 */
static void
hf_delete(hotfile_data_t *hotdata, u_int32_t fileid, u_int32_t temperature)
{
        hotfile_entry_t *entry, *parent, *next;

        parent = NULL;
        entry = hotdata->rootentry;

        while (entry &&
               entry->temperature != temperature &&
               entry->fileid != fileid) {

                parent = entry;
                if (temperature > entry->temperature)
                        entry = entry->right;
                else if (temperature < entry->temperature)
                        entry = entry->left;
                else if (fileid > entry->fileid)
                        entry = entry->right;
                else
                        entry = entry->left;
        }

        if (entry) {
                /*
                 * Reorganize the sub-trees spanning from our entry.
                 */
                if ((next = entry->right)) {
                        hotfile_entry_t *pnextl, *psub;
                        /*
                         * Tree pruning: take the left branch of the
                         * current entry and place it at the lowest
                         * left branch of the current right branch 
                         */
                        psub = next;
                        
                        /* Walk the Right/Left sub tree from current entry */
                        while ((pnextl = psub->left))
                                psub = pnextl;  
                        
                        /* Plug the old left tree to the new ->Right leftmost entry */  
                        psub->left = entry->left;
        
                } else /* only left sub-tree, simple case */ {  
                        next = entry->left;
                }
                /* 
                 * Now, plug the current entry sub tree to
                 * the good pointer of our parent entry.
                 */
                if (parent == NULL)
                        hotdata->rootentry = next;
                else if (parent->left == entry)
                        parent->left = next;
                else
                        parent->right = next;   
                
                /* Place entry back on the free-list */
                entry->left = 0;
                entry->fileid = 0;
                entry->temperature = 0;

                entry->right = hotdata->freelist; 
                hotdata->freelist = entry;              
                hotdata->activefiles--;
                
                if (hotdata->coldest == entry || hotdata->coldest == NULL) {
                        hotdata->coldest = hf_coldest(hotdata);
                }

        }
}

/*
 * Get a free hot file entry.
 */
static hotfile_entry_t *
hf_getnewentry(hotfile_data_t *hotdata)
{
        hotfile_entry_t * entry;
        
        /*
         * When the free list is empty then steal the coldest one
         */
        if (hotdata->freelist == NULL) {
                entry = hf_coldest(hotdata);
                hf_delete(hotdata, entry->fileid, entry->temperature);
        }
        entry = hotdata->freelist;
        hotdata->freelist = entry->right;
        entry->right = 0;
        
        return (entry);
}


/*
 * Generate a sorted list of hot files (hottest to coldest).
 *
 * As a side effect, every node in the hot file tree will be
 * deleted (moved to the free list).
 */
static void
hf_getsortedlist(hotfile_data_t * hotdata, hotfilelist_t *sortedlist)
{
        int i = 0;
        hotfile_entry_t *entry;
        
        while ((entry = hf_hottest(hotdata)) != NULL) {
                sortedlist->hfl_hotfile[i].hf_fileid = entry->fileid;
                sortedlist->hfl_hotfile[i].hf_temperature = entry->temperature;
                sortedlist->hfl_hotfile[i].hf_blocks = entry->blocks;
                sortedlist->hfl_totalblocks += entry->blocks;
                ++i;

                hf_delete(hotdata, entry->fileid, entry->temperature);
        }
        
        sortedlist->hfl_count = i;
        
#if HFC_VERBOSE
        printf("hfs: hf_getsortedlist returning %d entries w/%d total blocks\n", i, sortedlist->hfl_totalblocks);
#endif
}


#if HFC_DEBUG
static void
hf_maxdepth(hotfile_entry_t * root, int depth, int *maxdepth)
{
        if (root) {
                depth++;
                if (depth > *maxdepth)
                        *maxdepth = depth;
                hf_maxdepth(root->left, depth, maxdepth);
                hf_maxdepth(root->right, depth, maxdepth);
        }
}

static void
hf_printtree(hotfile_entry_t * root)
{
        if (root) {
                hf_printtree(root->left);
                printf("hfs: temperature: % 8d, fileid %d\n", root->temperature, root->fileid);
                hf_printtree(root->right);
        }
}
#endif