lib/isc/mem.c

	mem.c revision 697680186792135143176f9d692172ff9f54efba
/*
 * Copyright (C) 1997-2000  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
 * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
 * INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
 * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: mem.c,v 1.77 2001/01/09 00:39:46 marka Exp $ */

#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>

#include <limits.h>

#include <isc/mem.h>
#include <isc/msgs.h>
#include <isc/ondestroy.h>
#include <isc/string.h>

#include <isc/mutex.h>
#include <isc/util.h>

unsigned int isc_mem_debugging = 0;

/*
 * Constants.
 */

#define DEF_MAX_SIZE        1100
#define DEF_MEM_TARGET      4096
#define ALIGNMENT_SIZE      8       /* must be a power of 2 */
#define NUM_BASIC_BLOCKS    64      /* must be > 1 */
#define TABLE_INCREMENT     1024
#define DEBUGLIST_COUNT     1024

/*
 * Types.
 */
#if ISC_MEM_TRACKLINES
typedef struct debuglink debuglink_t;
struct debuglink {
    ISC_LINK(debuglink_t)   link;
    const void         *ptr[DEBUGLIST_COUNT];
    const char         *file[DEBUGLIST_COUNT];
    unsigned int        line[DEBUGLIST_COUNT];
    unsigned int        count;
};

#define FLARG_PASS  , file, line
#define FLARG       , const char *file, int line
#else
#define FLARG_PASS
#define FLARG
#endif

typedef struct element element;
struct element {
    element *       next;
};

typedef struct {
    /*
     * This structure must be ALIGNMENT_SIZE bytes.
     */
    union {
        size_t      size;
        char        bytes[ALIGNMENT_SIZE];
    } u;
} size_info;

struct stats {
    unsigned long       gets;
    unsigned long       totalgets;
    unsigned long       blocks;
    unsigned long       freefrags;
};

#define MEM_MAGIC       0x4D656d43U /* MemC. */
#define VALID_CONTEXT(c)    ((c) != NULL && (c)->magic == MEM_MAGIC)

struct isc_mem {
    unsigned int        magic;
    isc_ondestroy_t     ondestroy;
    isc_mutex_t     lock;
    isc_memalloc_t      memalloc;
    isc_memfree_t       memfree;
    void *          arg;
    size_t          max_size;
    size_t          mem_target;
    element **      freelists;
    element *       basic_blocks;
    unsigned char **    basic_table;
    unsigned int        basic_table_count;
    unsigned int        basic_table_size;
    unsigned char *     lowest;
    unsigned char *     highest;
    isc_boolean_t       checkfree;
    isc_boolean_t       trysplit;
    struct stats *      stats;
    unsigned int        references;
    size_t          quota;
    size_t          total;
    size_t          inuse;
    size_t          hi_water;
    size_t          lo_water;
    isc_boolean_t       hi_called;
    isc_mem_water_t     water;
    void *          water_arg;
    ISC_LIST(isc_mempool_t) pools;
#if ISC_MEM_TRACKLINES
    ISC_LIST(debuglink_t)   debuglist;
#endif
};

#define MEMPOOL_MAGIC       0x4D454d70U /* MEMp. */
#define VALID_MEMPOOL(c)    ((c) != NULL && (c)->magic == MEMPOOL_MAGIC)

struct isc_mempool {
    /* always unlocked */
    unsigned int    magic;      /* magic number */
    isc_mutex_t    *lock;       /* optional lock */
    isc_mem_t      *mctx;       /* our memory context */
    /* locked via the memory context's lock */
    ISC_LINK(isc_mempool_t) link;   /* next pool in this mem context */
    /* optionally locked from here down */
    element        *items;      /* low water item list */
    size_t      size;       /* size of each item on this pool */
    unsigned int    maxalloc;   /* max number of items allowed */
    unsigned int    allocated;  /* # of items currently given out */
    unsigned int    freecount;  /* # of items on reserved list */
    unsigned int    freemax;    /* # of items allowed on free list */
    unsigned int    fillcount;  /* # of items to fetch on each fill */
    /* Stats only. */
    unsigned int    gets;       /* # of requests to this pool */
    /* Debugging only. */
#if ISC_MEMPOOL_NAMES
    char        name[16];   /* printed name in stats reports */
#endif
};

/*
 * Private Inline-able.
 */

#if ! ISC_MEM_TRACKLINES
#define ADD_TRACE(a, b, c, d, e)
#define DELETE_TRACE(a, b, c, d, e)
#else
#define ADD_TRACE(a, b, c, d, e)    add_trace_entry(a, b, c, d, e)
#define DELETE_TRACE(a, b, c, d, e) delete_trace_entry(a, b, c, d, e)

#define MEM_TRACE   ((isc_mem_debugging & ISC_MEM_DEBUGTRACE) != 0)
#define MEM_RECORD  ((isc_mem_debugging & ISC_MEM_DEBUGRECORD) != 0)

/*
 * mctx must be locked.
 */
static inline void
add_trace_entry(isc_mem_t *mctx, const void *ptr, unsigned int size
        FLARG)
{
    debuglink_t *dl;
    unsigned int i;

    if (MEM_TRACE)
        fprintf(stderr, isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                           ISC_MSG_ADDTRACE,
                           "add %p size %u "
                           "file %s line %u mctx %p\n"),
            ptr, size, file, line, mctx);

    if (!MEM_RECORD)
        return;

    dl = ISC_LIST_HEAD(mctx->debuglist);
    while (dl != NULL) {
        if (dl->count == DEBUGLIST_COUNT)
            goto next;
        for (i = 0 ; i < DEBUGLIST_COUNT ; i++) {
            if (dl->ptr[i] == NULL) {
                dl->ptr[i] = ptr;
                dl->file[i] = file;
                dl->line[i] = line;
                dl->count++;
                return;
            }
        }
    next:
        dl = ISC_LIST_NEXT(dl, link);
    }

    dl = malloc(sizeof(debuglink_t));
    INSIST(dl != NULL);

    ISC_LINK_INIT(dl, link);
    for (i = 1 ; i < DEBUGLIST_COUNT ; i++) {
        dl->ptr[i] = NULL;
        dl->file[i] = NULL;
        dl->line[i] = 0;
    }

    dl->ptr[0] = ptr;
    dl->file[0] = file;
    dl->line[0] = line;
    dl->count = 1;

    ISC_LIST_PREPEND(mctx->debuglist, dl, link);
}

static inline void
delete_trace_entry(isc_mem_t *mctx, const void *ptr, unsigned int size,
           const char *file, unsigned int line)
{
    debuglink_t *dl;
    unsigned int i;

    if (MEM_TRACE)
        fprintf(stderr, isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                           ISC_MSG_DELTRACE,
                           "del %p size %u "
                           "file %s line %u mctx %p\n"),
            ptr, size, file, line, mctx);

    if (!MEM_RECORD)
        return;

    dl = ISC_LIST_HEAD(mctx->debuglist);
    while (dl != NULL) {
        for (i = 0 ; i < DEBUGLIST_COUNT ; i++) {
            if (dl->ptr[i] == ptr) {
                dl->ptr[i] = NULL;
                dl->file[i] = NULL;
                dl->line[i] = 0;

                INSIST(dl->count > 0);
                dl->count--;
                if (dl->count == 0) {
                    ISC_LIST_UNLINK(mctx->debuglist,
                            dl, link);
                    free(dl);
                }
                return;
            }
        }
        dl = ISC_LIST_NEXT(dl, link);
    }

    /*
     * If we get here, we didn't find the item on the list.  We're
     * screwed.
     */
    INSIST(dl != NULL);
}
#endif /* ISC_MEM_TRACKLINES */

static inline size_t
rmsize(size_t size) {
    /*
     * round down to ALIGNMENT_SIZE
     */
    return (size & (~(ALIGNMENT_SIZE - 1)));
}

static inline size_t
quantize(size_t size) {
    /*
     * Round up the result in order to get a size big
     * enough to satisfy the request and be aligned on ALIGNMENT_SIZE
     * byte boundaries.
     */

    if (size == 0)
        return (ALIGNMENT_SIZE);
    return ((size + ALIGNMENT_SIZE - 1) & (~(ALIGNMENT_SIZE - 1)));
}

static inline void
split(isc_mem_t *ctx, size_t size, size_t new_size) {
    unsigned char *ptr;
    size_t remaining_size;

    /*
     * Unlink a frag of size 'size'.
     */
    ptr = (unsigned char *)ctx->freelists[size];
    ctx->freelists[size] = ctx->freelists[size]->next;
    ctx->stats[size].freefrags--;

    /*
     * Create a frag of size 'new_size' and link it in.
     */
    ((element *)ptr)->next = ctx->freelists[new_size];
    ctx->freelists[new_size] = (element *)ptr;
    ctx->stats[new_size].freefrags++;

    /*
     * Create a frag of size 'size - new_size' and link it in.
     */
    remaining_size = size - new_size;
    ptr += new_size;
    ((element *)ptr)->next = ctx->freelists[remaining_size];
    ctx->freelists[remaining_size] = (element *)ptr;
    ctx->stats[remaining_size].freefrags++;
}

static inline isc_boolean_t
try_split(isc_mem_t *ctx, size_t new_size) {
    size_t i, doubled_size;

    if (!ctx->trysplit)
        return (ISC_FALSE);

    /*
     * Try splitting a frag that's at least twice as big as the size
     * we want.
     */
    doubled_size = new_size * 2;
    for (i = doubled_size;
         i < ctx->max_size;
         i += ALIGNMENT_SIZE) {
        if (ctx->freelists[i] != NULL) {
            split(ctx, i, new_size);
            return (ISC_TRUE);
        }
    }

    /*
     * No luck.  Try splitting any frag bigger than the size we need.
     */
    for (i = new_size + ALIGNMENT_SIZE;
         i < doubled_size;
         i += ALIGNMENT_SIZE) {
        if (ctx->freelists[i] != NULL) {
            split(ctx, i, new_size);
            return (ISC_TRUE);
        }
    }

    return (ISC_FALSE);
}

static inline isc_boolean_t
more_basic_blocks(isc_mem_t *ctx) {
    void *new;
    unsigned char *curr, *next;
    unsigned char *first, *last;
    unsigned char **table;
    unsigned int table_size;
    size_t increment;
    int i;

    /* Require: we hold the context lock. */

    /*
     * Did we hit the quota for this context?
     */
    increment = NUM_BASIC_BLOCKS * ctx->mem_target;
    if (ctx->quota != 0 && ctx->total + increment > ctx->quota)
        return (ISC_FALSE);

    INSIST(ctx->basic_table_count <= ctx->basic_table_size);
    if (ctx->basic_table_count == ctx->basic_table_size) {
        table_size = ctx->basic_table_size + TABLE_INCREMENT;
        table = (ctx->memalloc)(ctx->arg,
                    table_size * sizeof (unsigned char *));
        if (table == NULL)
            return (ISC_FALSE);
        if (ctx->basic_table_size != 0) {
            memcpy(table, ctx->basic_table,
                   ctx->basic_table_size *
                   sizeof (unsigned char *));
            (ctx->memfree)(ctx->arg, ctx->basic_table);
        }
        ctx->basic_table = table;
        ctx->basic_table_size = table_size;
    }

    new = (ctx->memalloc)(ctx->arg, NUM_BASIC_BLOCKS * ctx->mem_target);
    if (new == NULL)
        return (ISC_FALSE);
    ctx->total += increment;
    ctx->basic_table[ctx->basic_table_count] = new;
    ctx->basic_table_count++;

    curr = new;
    next = curr + ctx->mem_target;
    for (i = 0; i < (NUM_BASIC_BLOCKS - 1); i++) {
        ((element *)curr)->next = (element *)next;
        curr = next;
        next += ctx->mem_target;
    }
    /*
     * curr is now pointing at the last block in the
     * array.
     */
    ((element *)curr)->next = NULL;
    first = new;
    last = first + NUM_BASIC_BLOCKS * ctx->mem_target - 1;
    if (first < ctx->lowest || ctx->lowest == NULL)
        ctx->lowest = first;
    if (last > ctx->highest)
        ctx->highest = last;
    ctx->basic_blocks = new;

    return (ISC_TRUE);
}

static inline isc_boolean_t
more_frags(isc_mem_t *ctx, size_t new_size) {
    int i, frags;
    size_t total_size;
    void *new;
    unsigned char *curr, *next;

    /*
     * Try to get more fragments by chopping up a basic block.
     */

    if (ctx->basic_blocks == NULL) {
        if (!more_basic_blocks(ctx)) {
            /*
             * We can't get more memory from the OS, or we've
             * hit the quota for this context.
             */
            /*
             * XXXRTH  "At quota" notification here.
             */
            /*
             * Maybe we can split one of our existing
             * list frags.
             */
            return (try_split(ctx, new_size));
        }
    }

    total_size = ctx->mem_target;
    new = ctx->basic_blocks;
    ctx->basic_blocks = ctx->basic_blocks->next;
    frags = total_size / new_size;
    ctx->stats[new_size].blocks++;
    ctx->stats[new_size].freefrags += frags;
    /*
     * Set up a linked-list of blocks of size
     * "new_size".
     */
    curr = new;
    next = curr + new_size;
    total_size -= new_size;
    for (i = 0; i < (frags - 1); i++) {
        ((element *)curr)->next = (element *)next;
        curr = next;
        next += new_size;
        total_size -= new_size;
    }
    /*
     * Add the remaining fragment of the basic block to a free list.
     */
    total_size = rmsize(total_size);
    if (total_size > 0) {
        ((element *)next)->next = ctx->freelists[total_size];
        ctx->freelists[total_size] = (element *)next;
        ctx->stats[total_size].freefrags++;
    }
    /*
     * curr is now pointing at the last block in the
     * array.
     */
    ((element *)curr)->next = NULL;
    ctx->freelists[new_size] = new;

    return (ISC_TRUE);
}

static inline void *
mem_getunlocked(isc_mem_t *ctx, size_t size) {
    size_t new_size = quantize(size);
    void *ret;

    if (size >= ctx->max_size || new_size >= ctx->max_size) {
        /*
         * memget() was called on something beyond our upper limit.
         */
        if (ctx->quota != 0 && ctx->total + size > ctx->quota) {
            ret = NULL;
            goto done;
        }
        ret = (ctx->memalloc)(ctx->arg, size);
        if (ret != NULL) {
            ctx->total += size;
            ctx->inuse += size;
            ctx->stats[ctx->max_size].gets++;
            ctx->stats[ctx->max_size].totalgets++;
            /*
             * If we don't set new_size to size, then the
             * ISC_MEM_FILL code might write over bytes we
             * don't own.
             */
            new_size = size;
        }
        goto done;
    }

    /*
     * If there are no blocks in the free list for this size, get a chunk
     * of memory and then break it up into "new_size"-sized blocks, adding
     * them to the free list.
     */
    if (ctx->freelists[new_size] == NULL && !more_frags(ctx, new_size))
        return (NULL);

    /*
     * The free list uses the "rounded-up" size "new_size".
     */
    ret = ctx->freelists[new_size];
    ctx->freelists[new_size] = ctx->freelists[new_size]->next;

    /*
     * The stats[] uses the _actual_ "size" requested by the
     * caller, with the caveat (in the code above) that "size" >= the
     * max. size (max_size) ends up getting recorded as a call to
     * max_size.
     */
    ctx->stats[size].gets++;
    ctx->stats[size].totalgets++;
    ctx->stats[new_size].freefrags--;
    ctx->inuse += new_size;

 done:

#if ISC_MEM_FILL
    if (ret != NULL)
        memset(ret, 0xbe, new_size); /* Mnemonic for "beef". */
#endif

    return (ret);
}

#if ISC_MEM_FILL && ISC_MEM_CHECKOVERRUN
static inline void
check_overrun(void *mem, size_t size, size_t new_size) {
    unsigned char *cp;

    cp = (unsigned char *)mem;
    cp += size;
    while (size < new_size) {
        INSIST(*cp == 0xbe);
        cp++;
        size++;
    }
}
#endif

static inline void
mem_putunlocked(isc_mem_t *ctx, void *mem, size_t size) {
    size_t new_size = quantize(size);

    if (size == ctx->max_size || new_size >= ctx->max_size) {
        /*
         * memput() called on something beyond our upper limit.
         */
#if ISC_MEM_FILL
        memset(mem, 0xde, size); /* Mnemonic for "dead". */
#endif
        (ctx->memfree)(ctx->arg, mem);
        INSIST(ctx->stats[ctx->max_size].gets != 0);
        ctx->stats[ctx->max_size].gets--;
        INSIST(size <= ctx->total);
        ctx->inuse -= size;
        ctx->total -= size;
        return;
    }

#if ISC_MEM_FILL
#if ISC_MEM_CHECKOVERRUN
    check_overrun(mem, size, new_size);
#endif
    memset(mem, 0xde, new_size); /* Mnemonic for "dead". */
#endif

    /*
     * The free list uses the "rounded-up" size "new_size".
     */
    ((element *)mem)->next = ctx->freelists[new_size];
    ctx->freelists[new_size] = (element *)mem;

    /*
     * The stats[] uses the _actual_ "size" requested by the
     * caller, with the caveat (in the code above) that "size" >= the
     * max. size (max_size) ends up getting recorded as a call to
     * max_size.
     */
    INSIST(ctx->stats[size].gets != 0);
    ctx->stats[size].gets--;
    ctx->stats[new_size].freefrags++;
    ctx->inuse -= new_size;
}

/*
 * Private.
 */

static void *
default_memalloc(void *arg, size_t size) {
    UNUSED(arg);
    return (malloc(size));
}

static void
default_memfree(void *arg, void *ptr) {
    UNUSED(arg);
    free(ptr);
}

/*
 * Public.
 */

isc_result_t
isc_mem_createx(size_t init_max_size, size_t target_size,
        isc_memalloc_t memalloc, isc_memfree_t memfree, void *arg,
        isc_mem_t **ctxp)
{
    isc_mem_t *ctx;

    REQUIRE(ctxp != NULL && *ctxp == NULL);
    REQUIRE(memalloc != NULL);
    REQUIRE(memfree != NULL);

    INSIST((ALIGNMENT_SIZE & (ALIGNMENT_SIZE - 1)) == 0);

    ctx = (memalloc)(arg, sizeof *ctx);
    if (ctx == NULL)
        return (ISC_R_NOMEMORY);

    if (init_max_size == 0)
        ctx->max_size = DEF_MAX_SIZE;
    else
        ctx->max_size = init_max_size;
    if (target_size == 0)
        ctx->mem_target = DEF_MEM_TARGET;
    else
        ctx->mem_target = target_size;
    ctx->memalloc = memalloc;
    ctx->memfree = memfree;
    ctx->arg = arg;
    ctx->freelists = (memalloc)(arg, ctx->max_size * sizeof (element *));
    if (ctx->freelists == NULL) {
        (memfree)(arg, ctx);
        return (ISC_R_NOMEMORY);
    }
    ctx->checkfree = ISC_TRUE;
    ctx->trysplit = ISC_FALSE;
    memset(ctx->freelists, 0,
           ctx->max_size * sizeof (element *));
    ctx->stats = (memalloc)(arg,
                (ctx->max_size+1) * sizeof (struct stats));
    if (ctx->stats == NULL) {
        (memfree)(arg, ctx->freelists);
        (memfree)(arg, ctx);
        return (ISC_R_NOMEMORY);
    }
    memset(ctx->stats, 0, (ctx->max_size + 1) * sizeof (struct stats));
    ctx->basic_blocks = NULL;
    ctx->basic_table = NULL;
    ctx->basic_table_count = 0;
    ctx->basic_table_size = 0;
    ctx->lowest = NULL;
    ctx->highest = NULL;
    if (isc_mutex_init(&ctx->lock) != ISC_R_SUCCESS) {
        (memfree)(arg, ctx->stats);
        (memfree)(arg, ctx->freelists);
        (memfree)(arg, ctx);
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_mutex_init() %s",
                 isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
                        ISC_MSG_FAILED, "failed"));
        return (ISC_R_UNEXPECTED);
    }
    ctx->references = 1;
    ctx->quota = 0;
    ctx->total = 0;
    ctx->inuse = 0;
    ctx->hi_water = 0;
    ctx->lo_water = 0;
    ctx->hi_called = ISC_FALSE;
    ctx->water = NULL;
    ctx->water_arg = NULL;
    ctx->magic = MEM_MAGIC;
    isc_ondestroy_init(&ctx->ondestroy);
    ISC_LIST_INIT(ctx->pools);
#if ISC_MEM_TRACKLINES
    ISC_LIST_INIT(ctx->debuglist);
#endif

    *ctxp = ctx;
    return (ISC_R_SUCCESS);
}

isc_result_t
isc_mem_create(size_t init_max_size, size_t target_size,
           isc_mem_t **ctxp)
{
    return (isc_mem_createx(init_max_size, target_size,
                default_memalloc, default_memfree, NULL,
                ctxp));
}

static void
destroy(isc_mem_t *ctx) {
    unsigned int i;
    isc_ondestroy_t ondest;

    ctx->magic = 0;

    INSIST(ISC_LIST_EMPTY(ctx->pools));
#if ISC_MEM_TRACKLINES
    if (ctx->checkfree)
        INSIST(ISC_LIST_EMPTY(ctx->debuglist));
    else {
        debuglink_t *dl;

        for (dl = ISC_LIST_HEAD(ctx->debuglist);
             dl != NULL;
             dl = ISC_LIST_HEAD(ctx->debuglist)) {
            ISC_LIST_UNLINK(ctx->debuglist, dl, link);
            free(dl);
        }
    }
#endif
    INSIST(ctx->references == 0);

    if (ctx->checkfree) {
        for (i = 0; i <= ctx->max_size; i++)
            INSIST(ctx->stats[i].gets == 0);
    }

#if 0                   /* XXX brister debugging */
    for (i = 0; i < ctx->basic_table_count; i++)
        memset(ctx->basic_table[i], 0x0,
               NUM_BASIC_BLOCKS * ctx->mem_target);
#endif


    for (i = 0; i < ctx->basic_table_count; i++)
        (ctx->memfree)(ctx->arg, ctx->basic_table[i]);
    (ctx->memfree)(ctx->arg, ctx->freelists);
    (ctx->memfree)(ctx->arg, ctx->stats);
    (ctx->memfree)(ctx->arg, ctx->basic_table);

    ondest = ctx->ondestroy;

    DESTROYLOCK(&ctx->lock);
    (ctx->memfree)(ctx->arg, ctx);

    isc_ondestroy_notify(&ondest, ctx);
}

void
isc_mem_attach(isc_mem_t *source, isc_mem_t **targetp) {
    REQUIRE(VALID_CONTEXT(source));
    REQUIRE(targetp != NULL && *targetp == NULL);

    LOCK(&source->lock);
    source->references++;
    UNLOCK(&source->lock);

    *targetp = source;
}

void
isc_mem_detach(isc_mem_t **ctxp) {
    isc_mem_t *ctx;
    isc_boolean_t want_destroy = ISC_FALSE;

    REQUIRE(ctxp != NULL);
    ctx = *ctxp;
    REQUIRE(VALID_CONTEXT(ctx));

    LOCK(&ctx->lock);
    INSIST(ctx->references > 0);
    ctx->references--;
    if (ctx->references == 0)
        want_destroy = ISC_TRUE;
    UNLOCK(&ctx->lock);

    if (want_destroy)
        destroy(ctx);

    *ctxp = NULL;
}

/*
 * isc_mem_putanddetach() is the equivalent of:
 *
 * mctx = NULL;
 * isc_mem_attach(ptr->mctx, &mctx);
 * isc_mem_detach(&ptr->mctx);
 * isc_mem_put(mctx, ptr, sizeof(*ptr);
 * isc_mem_detach(&mctx);
 */

void
isc__mem_putanddetach(isc_mem_t **ctxp, void *ptr, size_t size FLARG) {
    isc_mem_t *ctx;
    isc_boolean_t want_destroy = ISC_FALSE;

    REQUIRE(ctxp != NULL);
    ctx = *ctxp;
    REQUIRE(VALID_CONTEXT(ctx));
    REQUIRE(ptr != NULL);

    /*
     * Must be before mem_putunlocked() as ctxp is usually within
     * [ptr..ptr+size).
     */
    *ctxp = NULL;

    LOCK(&ctx->lock);
    DELETE_TRACE(ctx, ptr, size, file, line);
    mem_putunlocked(ctx, ptr, size);
    INSIST(ctx->references > 0);
    ctx->references--;
    if (ctx->references == 0)
        want_destroy = ISC_TRUE;
    UNLOCK(&ctx->lock);

    if (want_destroy)
        destroy(ctx);
}

void
isc_mem_destroy(isc_mem_t **ctxp) {
    isc_mem_t *ctx;

    /*
     * This routine provides legacy support for callers who use mctxs
     * without attaching/detaching.
     */

    REQUIRE(ctxp != NULL);
    ctx = *ctxp;
    REQUIRE(VALID_CONTEXT(ctx));

    LOCK(&ctx->lock);
    REQUIRE(ctx->references == 1);
    ctx->references--;
    UNLOCK(&ctx->lock);

    destroy(ctx);

    *ctxp = NULL;
}

isc_result_t
isc_mem_ondestroy(isc_mem_t *ctx, isc_task_t *task, isc_event_t **event) {
    isc_result_t res;

    LOCK(&ctx->lock);
    res = isc_ondestroy_register(&ctx->ondestroy, task, event);
    UNLOCK(&ctx->lock);

    return (res);
}


isc_result_t
isc_mem_restore(isc_mem_t *ctx) {
    isc_result_t result;

    result = isc_mutex_init(&ctx->lock);
    if (result != ISC_R_SUCCESS)
        ctx->magic = 0;

    return (result);
}

void *
isc__mem_get(isc_mem_t *ctx, size_t size FLARG) {
    void *ptr;
    isc_boolean_t call_water = ISC_FALSE;

    REQUIRE(VALID_CONTEXT(ctx));

    LOCK(&ctx->lock);
    ptr = mem_getunlocked(ctx, size);
    ADD_TRACE(ctx, ptr, size, file, line);
    if (ctx->hi_water != 0 && !ctx->hi_called &&
        ctx->inuse > ctx->hi_water) {
        ctx->hi_called = ISC_TRUE;
        call_water = ISC_TRUE;
    }
    UNLOCK(&ctx->lock);

    /* XXX remove */
    if (ctx->hi_water)
        fprintf(stderr,"inuse %u, total %u\n", ctx->inuse, ctx->total);

    if (call_water) {
        /* XXX remove */
        fprintf(stderr, "%s water(%p, ISC_MEM_HIWATER)\n",
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
                       ISC_MSG_CALLING, "calling"),
            ctx->water_arg);
        (ctx->water)(ctx->water_arg, ISC_MEM_HIWATER);
    }

    return (ptr);
}

void
isc__mem_put(isc_mem_t *ctx, void *ptr, size_t size FLARG)
{
    isc_boolean_t call_water = ISC_FALSE;

    REQUIRE(VALID_CONTEXT(ctx));
    REQUIRE(ptr != NULL);

    LOCK(&ctx->lock);
    DELETE_TRACE(ctx, ptr, size, file, line);
    mem_putunlocked(ctx, ptr, size);
    if (ctx->hi_called && ctx->inuse < ctx->lo_water) {
        ctx->hi_called = ISC_FALSE;
        call_water = ISC_TRUE;
    }
    UNLOCK(&ctx->lock);

    /* XXX remove */
    if (ctx->hi_water)
        fprintf(stderr,"inuse %u, total %u\n", ctx->inuse, ctx->total);

    if (call_water) {
        /* XXX remove */
        fprintf(stderr, "%s water(%p,ISC_MEM_LOWATER)\n",
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
                       ISC_MSG_CALLING, "calling"),
            ctx->water_arg);
        (ctx->water)(ctx->water_arg, ISC_MEM_LOWATER);
    }
}

isc_result_t
isc_mem_preallocate(isc_mem_t *ctx) {
    size_t i;
    isc_result_t result = ISC_R_SUCCESS;
    void *ptr;

    REQUIRE(VALID_CONTEXT(ctx));

    LOCK(&ctx->lock);

    for (i = 0; i < ctx->max_size; i += ALIGNMENT_SIZE) {
        ptr = mem_getunlocked(ctx, i);
        if (ptr == NULL) {
            result = ISC_R_NOMEMORY;
            break;
        }
        mem_putunlocked(ctx, ptr, i);
    }

    UNLOCK(&ctx->lock);

    return (result);
}

/*
 * Print the stats[] on the stream "out" with suitable formatting.
 */
void
isc_mem_stats(isc_mem_t *ctx, FILE *out) {
    size_t i;
    const struct stats *s;
    const isc_mempool_t *pool;

    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    if (ctx->freelists != NULL) {
        for (i = 0; i <= ctx->max_size; i++) {
            s = &ctx->stats[i];

            if (s->totalgets == 0 && s->gets == 0)
                continue;
            fprintf(out, "%s%5lu: %11lu gets, %11lu rem",
                (i == ctx->max_size) ? ">=" : "  ",
                (unsigned long) i, s->totalgets, s->gets);
            if (s->blocks != 0 || s->freefrags != 0)
                fprintf(out, " (%lu bl, %lu ff)",
                    s->blocks, s->freefrags);
            fputc('\n', out);
        }
    }

    /*
     * Note that since a pool can be locked now, these stats might be
     * somewhat off if the pool is in active use at the time the stats
     * are dumped.  The link fields are protected by the isc_mem_t's
     * lock, however, so walking this list and extracting integers from
     * stats fields is always safe.
     */
    pool = ISC_LIST_HEAD(ctx->pools);
    if (pool != NULL) {
        fprintf(out, isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                        ISC_MSG_POOLSTATS,
                        "[Pool statistics]\n"));
        fprintf(out, "%15s %10s %10s %10s %10s %10s %10s %10s %1s\n",
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                       ISC_MSG_POOLNAME, "name"),
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                       ISC_MSG_POOLSIZE, "size"),
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                       ISC_MSG_POOLMAXALLOC, "maxalloc"),
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                       ISC_MSG_POOLALLOCATED, "allocated"),
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                       ISC_MSG_POOLFREECOUNT, "freecount"),
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                       ISC_MSG_POOLFREEMAX, "freemax"),
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                       ISC_MSG_POOLFILLCOUNT, "fillcount"),
            isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                       ISC_MSG_POOLGETS, "gets"),
            "L");
    }
    while (pool != NULL) {
        fprintf(out, "%15s %10lu %10u %10u %10u %10u %10u %10u %s\n",
            pool->name, (unsigned long) pool->size, pool->maxalloc,
            pool->allocated, pool->freecount, pool->freemax,
            pool->fillcount, pool->gets,
            (pool->lock == NULL ? "N" : "Y"));
        pool = ISC_LIST_NEXT(pool, link);
    }

#if ISC_MEM_TRACKLINES
    if (MEM_RECORD) {
        debuglink_t *dl;
        unsigned int i;

        fprintf(out, isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                        ISC_MSG_DUMPALLOC,
                        "DUMP OF ALL OUTSTANDING "
                        "MEMORY ALLOCATIONS\n"));
        dl = ISC_LIST_HEAD(ctx->debuglist);
        if (dl == NULL)
            fprintf(out, isc_msgcat_get(isc_msgcat, ISC_MSGSET_MEM,
                            ISC_MSG_NONE,
                            "\tNone.\n"));
        while (dl != NULL) {
            for (i = 0 ; i < DEBUGLIST_COUNT ; i++)
                if (dl->ptr[i] != NULL)
                    fprintf(out,
                        isc_msgcat_get(isc_msgcat,
                               ISC_MSGSET_MEM,
                               ISC_MSG_PTRFILELINE,
                               "\tptr %p "
                               "file %s "
                               "line %u\n"),
                        dl->ptr[i], dl->file[i],
                        dl->line[i]);
            dl = ISC_LIST_NEXT(dl, link);
        }
    }
#endif

    UNLOCK(&ctx->lock);
}

isc_boolean_t
isc_mem_valid(isc_mem_t *ctx, void *ptr) {
    unsigned char *cp = ptr;
    isc_boolean_t result = ISC_FALSE;

    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    if (ctx->lowest != NULL && cp >= ctx->lowest && cp <= ctx->highest)
        result = ISC_TRUE;

    UNLOCK(&ctx->lock);

    return (result);
}

/*
 * Replacements for malloc() and free() -- they implicitly remember the
 * size of the object allocated (with some additional overhead).
 */

static void *
isc__mem_allocateunlocked(isc_mem_t *ctx, size_t size) {
    size_info *si;

    size += ALIGNMENT_SIZE;
    si = mem_getunlocked(ctx, size);
    if (si == NULL)
        return (NULL);
    si->u.size = size;
    return (&si[1]);
}

void *
isc__mem_allocate(isc_mem_t *ctx, size_t size FLARG) {
    size_info *si;

    REQUIRE(VALID_CONTEXT(ctx));

    LOCK(&ctx->lock);
    si = isc__mem_allocateunlocked(ctx, size);
#if ISC_MEM_TRACKLINES
    if (si != NULL)
        ADD_TRACE(ctx, si, si[-1].u.size, file, line);
#endif
    UNLOCK(&ctx->lock);

    return (si);
}

void
isc__mem_free(isc_mem_t *ctx, void *ptr FLARG) {
    size_info *si;

    REQUIRE(VALID_CONTEXT(ctx));
    REQUIRE(ptr != NULL);

    si = &(((size_info *)ptr)[-1]);
    LOCK(&ctx->lock);
    DELETE_TRACE(ctx, ptr, si->u.size, file, line);
    mem_putunlocked(ctx, si, si->u.size);
    UNLOCK(&ctx->lock);
}

/*
 * Other useful things.
 */

char *
isc__mem_strdup(isc_mem_t *mctx, const char *s FLARG) {
    size_t len;
    char *ns;

    REQUIRE(VALID_CONTEXT(mctx));
    REQUIRE(s != NULL);

    len = strlen(s);

    ns = isc__mem_allocate(mctx, len + 1 FLARG_PASS);

    if (ns != NULL)
        strncpy(ns, s, len + 1);

    return (ns);
}

void
isc_mem_setdestroycheck(isc_mem_t *ctx, isc_boolean_t flag) {
    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    ctx->checkfree = flag;

    UNLOCK(&ctx->lock);
}

void
isc_mem_setsplit(isc_mem_t *ctx, isc_boolean_t flag) {
    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    ctx->trysplit = flag;

    UNLOCK(&ctx->lock);
}


/*
 * Quotas
 */

void
isc_mem_setquota(isc_mem_t *ctx, size_t quota) {
    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    ctx->quota = quota;

    UNLOCK(&ctx->lock);
}

size_t
isc_mem_getquota(isc_mem_t *ctx) {
    size_t quota;

    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    quota = ctx->quota;

    UNLOCK(&ctx->lock);

    return (quota);
}

size_t
isc_mem_inuse(isc_mem_t *ctx) {
    size_t inuse;

    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    inuse = ctx->inuse;

    UNLOCK(&ctx->lock);

    return (inuse);
}

void
isc_mem_setwater(isc_mem_t *ctx, isc_mem_water_t water, void *water_arg,
                 size_t hiwater, size_t lowater)
{
    REQUIRE(VALID_CONTEXT(ctx));

    if (water != NULL) {
        REQUIRE(hiwater > lowater);
        REQUIRE(hiwater > 0);
        REQUIRE(lowater > 0);
    }

    LOCK(&ctx->lock);
    if (water == NULL) {
        ctx->water = NULL;
        ctx->water_arg = NULL;
        ctx->hi_water = 0;
        ctx->lo_water = 0;
        ctx->hi_called = ISC_FALSE;
    } else {
        ctx->water = water;
        ctx->water_arg = water_arg;
        ctx->hi_water = hiwater;
        ctx->lo_water = lowater;
        ctx->hi_called = ISC_FALSE;
    }
    UNLOCK(&ctx->lock);
}

/*
 * Memory pool stuff
 */


#if 0
/*
 * Free all but "n" items from the pool's free list.  If n == 0, all items
 * will be returned to the mctx.
 */
static void
mempool_release(isc_mempool_t *mpctx, unsigned int n) {
    isc_mem_t *mctx;
    element *item;
    element *next;
    unsigned int count;

    mctx = mpctx->mctx;

    if (mpctx->freecount <= n)
        return;

    INSIST(mpctx->items != NULL);
    item = mpctx->items;
    for (count = 0 ; count < n ; count++) {
        item = item->next;
        INSIST(item != NULL);
    }

    /*
     * All remaining items are to be freed.  Lock the context once,
     * free them all, and unlock the context.
     */
    LOCK(&mctx->lock);
    do {
        next = item->next;
        mem_putunlocked(mctx, item, mpctx->size);
        INSIST(mpctx->freecount > 0);
        mpctx->freecount--;
        item = next;
    } while (item != NULL);
    UNLOCK(&mctx->lock);
}
#endif

/*
 * Release all items on the free list.  No locking is done, the memory
 * context must be locked, and the pool if needed.
 */
static void
mempool_releaseall(isc_mempool_t *mpctx) {
    isc_mem_t *mctx;
    element *item;
    element *next;

    mctx = mpctx->mctx;

    if (mpctx->freecount == 0)
        return;

    INSIST(mpctx->items != NULL);
    item = mpctx->items;

    do {
        next = item->next;
        mem_putunlocked(mctx, item, mpctx->size);
        INSIST(mpctx->freecount > 0);
        mpctx->freecount--;
        item = next;
    } while (item != NULL);
}

isc_result_t
isc_mempool_create(isc_mem_t *mctx, size_t size, isc_mempool_t **mpctxp) {
    isc_mempool_t *mpctx;

    REQUIRE(VALID_CONTEXT(mctx));
    REQUIRE(size > 0);
    REQUIRE(mpctxp != NULL && *mpctxp == NULL);

    /*
     * Allocate space for this pool, initialize values, and if all works
     * well, attach to the memory context.
     */
    LOCK(&mctx->lock);

    mpctx = mem_getunlocked(mctx, sizeof(isc_mempool_t));
    if (mpctx == NULL) {
        UNLOCK(&mctx->lock);
        return (ISC_R_NOMEMORY);
    }

    mpctx->magic = MEMPOOL_MAGIC;
    mpctx->lock = NULL;
    mpctx->mctx = mctx;
    mpctx->size = size;
    mpctx->maxalloc = UINT_MAX;
    mpctx->allocated = 0;
    mpctx->freecount = 0;
    mpctx->freemax = 1;
    mpctx->fillcount = 1;
    mpctx->gets = 0;
#if ISC_MEMPOOL_NAMES
    mpctx->name[0] = 0;
#endif
    mpctx->items = NULL;

    *mpctxp = mpctx;

    ISC_LIST_INITANDAPPEND(mctx->pools, mpctx, link);

    UNLOCK(&mctx->lock);

    return (ISC_R_SUCCESS);
}

void
isc_mempool_setname(isc_mempool_t *mpctx, const char *name) {
    REQUIRE(name != NULL);

#if ISC_MEMPOOL_NAMES
    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    strncpy(mpctx->name, name, sizeof(mpctx->name) - 1);
    mpctx->name[sizeof(mpctx->name) - 1] = '\0';

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
#else
    UNUSED(mpctx);
    UNUSED(name);
#endif
}

void
isc_mempool_destroy(isc_mempool_t **mpctxp) {
    isc_mempool_t *mpctx;
    isc_mem_t *mctx;
    isc_mutex_t *lock;

    REQUIRE(mpctxp != NULL);
    mpctx = *mpctxp;
    REQUIRE(VALID_MEMPOOL(mpctx));
    REQUIRE(mpctx->allocated == 0);

    mctx = mpctx->mctx;

    lock = mpctx->lock;

    if (lock != NULL)
        LOCK(lock);

    LOCK(&mctx->lock);

    /*
     * Return any items on the free list
     */
    mempool_releaseall(mpctx);

    /*
     * Remove our linked list entry from the memory context.
     */
    ISC_LIST_UNLINK(mctx->pools, mpctx, link);

    mpctx->magic = 0;

    mem_putunlocked(mpctx->mctx, mpctx, sizeof(isc_mempool_t));

    UNLOCK(&mctx->lock);

    if (lock != NULL)
        UNLOCK(lock);

    *mpctxp = NULL;
}

void
isc_mempool_associatelock(isc_mempool_t *mpctx, isc_mutex_t *lock) {
    REQUIRE(VALID_MEMPOOL(mpctx));
    REQUIRE(mpctx->lock == NULL);
    REQUIRE(lock != NULL);

    mpctx->lock = lock;
}

void *
isc__mempool_get(isc_mempool_t *mpctx FLARG) {
    element *item;
    isc_mem_t *mctx;
    unsigned int i;

    REQUIRE(VALID_MEMPOOL(mpctx));

    mctx = mpctx->mctx;

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    /*
     * Don't let the caller go over quota
     */
    if (mpctx->allocated >= mpctx->maxalloc) {
        item = NULL;
        goto out;
    }

    /*
     * if we have a free list item, return the first here
     */
    item = mpctx->items;
    if (item != NULL) {
        mpctx->items = item->next;
        INSIST(mpctx->freecount > 0);
        mpctx->freecount--;
        mpctx->gets++;
        mpctx->allocated++;
        goto out;
    }

    /*
     * We need to dip into the well.  Lock the memory context here and
     * fill up our free list.
     */
    LOCK(&mctx->lock);
    for (i = 0 ; i < mpctx->fillcount ; i++) {
        item = mem_getunlocked(mctx, mpctx->size);
        if (item == NULL)
            break;
        item->next = mpctx->items;
        mpctx->items = item;
        mpctx->freecount++;
    }
    UNLOCK(&mctx->lock);

    /*
     * If we didn't get any items, return NULL.
     */
    item = mpctx->items;
    if (item == NULL)
        goto out;

    mpctx->items = item->next;
    mpctx->freecount--;
    mpctx->gets++;
    mpctx->allocated++;

 out:
    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    if (item != NULL) {
        LOCK(&mctx->lock);
        ADD_TRACE(mctx, item, mpctx->size, file, line);
        UNLOCK(&mctx->lock);
    }

    return (item);
}

void
isc__mempool_put(isc_mempool_t *mpctx, void *mem FLARG) {
    isc_mem_t *mctx;
    element *item;

    REQUIRE(VALID_MEMPOOL(mpctx));
    REQUIRE(mem != NULL);

    mctx = mpctx->mctx;

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    INSIST(mpctx->allocated > 0);
    mpctx->allocated--;

    DELETE_TRACE(mctx, mem, mpctx->size, file, line);

    /*
     * If our free list is full, return this to the mctx directly.
     */
    if (mpctx->freecount >= mpctx->freemax) {
        LOCK(&mctx->lock);
        mem_putunlocked(mctx, mem, mpctx->size);
        UNLOCK(&mctx->lock);
        if (mpctx->lock != NULL)
            UNLOCK(mpctx->lock);
        return;
    }

    /*
     * Otherwise, attach it to our free list and bump the counter.
     */
    mpctx->freecount++;
    item = (element *)mem;
    item->next = mpctx->items;
    mpctx->items = item;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
}

/*
 * Quotas
 */

void
isc_mempool_setfreemax(isc_mempool_t *mpctx, unsigned int limit) {
    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    mpctx->freemax = limit;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
}

unsigned int
isc_mempool_getfreemax(isc_mempool_t *mpctx) {
    unsigned int freemax;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    freemax = mpctx->freemax;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (freemax);
}

unsigned int
isc_mempool_getfreecount(isc_mempool_t *mpctx) {
    unsigned int freecount;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    freecount = mpctx->freecount;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (freecount);
}

void
isc_mempool_setmaxalloc(isc_mempool_t *mpctx, unsigned int limit) {
    REQUIRE(limit > 0);

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    mpctx->maxalloc = limit;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
}

unsigned int
isc_mempool_getmaxalloc(isc_mempool_t *mpctx) {
    unsigned int maxalloc;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    maxalloc = mpctx->maxalloc;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (maxalloc);
}

unsigned int
isc_mempool_getallocated(isc_mempool_t *mpctx) {
    unsigned int allocated;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    allocated = mpctx->allocated;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (allocated);
}

void
isc_mempool_setfillcount(isc_mempool_t *mpctx, unsigned int limit) {
    REQUIRE(limit > 0);
    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    mpctx->fillcount = limit;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
}

unsigned int
isc_mempool_getfillcount(isc_mempool_t *mpctx) {
    unsigned int fillcount;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    fillcount = mpctx->fillcount;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (fillcount);
}