[mirror_spl.git] / module / spl / spl-kmem.c

/*****************************************************************************\
 *  Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
 *  Copyright (C) 2007 The Regents of the University of California.
 *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
 *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
 *  UCRL-CODE-235197
 *
 *  This file is part of the SPL, Solaris Porting Layer.
 *  For details, see <http://zfsonlinux.org/>.
 *
 *  The SPL is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License as published by the
 *  Free Software Foundation; either version 2 of the License, or (at your
 *  option) any later version.
 *
 *  The SPL is distributed in the hope that it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
 *****************************************************************************
 *  Solaris Porting Layer (SPL) Kmem Implementation.
\*****************************************************************************/

#include <sys/kmem.h>
#include <spl-debug.h>

#ifdef SS_DEBUG_SUBSYS
#undef SS_DEBUG_SUBSYS
#endif

#define SS_DEBUG_SUBSYS SS_KMEM

/*
 * Within the scope of spl-kmem.c file the kmem_cache_* definitions
 * are removed to allow access to the real Linux slab allocator.
 */
#undef kmem_cache_destroy
#undef kmem_cache_create
#undef kmem_cache_alloc
#undef kmem_cache_free


/*
 * Cache expiration was implemented because it was part of the default Solaris
 * kmem_cache behavior.  The idea is that per-cpu objects which haven't been
 * accessed in several seconds should be returned to the cache.  On the other
 * hand Linux slabs never move objects back to the slabs unless there is
 * memory pressure on the system.  By default the Linux method is enabled
 * because it has been shown to improve responsiveness on low memory systems.
 * This policy may be changed by setting KMC_EXPIRE_AGE or KMC_EXPIRE_MEM.
 */
unsigned int spl_kmem_cache_expire = KMC_EXPIRE_MEM;
EXPORT_SYMBOL(spl_kmem_cache_expire);
module_param(spl_kmem_cache_expire, uint, 0644);
MODULE_PARM_DESC(spl_kmem_cache_expire, "By age (0x1) or low memory (0x2)");

unsigned int spl_kmem_cache_obj_per_slab = SPL_KMEM_CACHE_OBJ_PER_SLAB;
module_param(spl_kmem_cache_obj_per_slab, uint, 0644);
MODULE_PARM_DESC(spl_kmem_cache_obj_per_slab, "Number of objects per slab");

unsigned int spl_kmem_cache_obj_per_slab_min = SPL_KMEM_CACHE_OBJ_PER_SLAB_MIN;
module_param(spl_kmem_cache_obj_per_slab_min, uint, 0644);
MODULE_PARM_DESC(spl_kmem_cache_obj_per_slab_min,
    "Minimal number of objects per slab");

unsigned int spl_kmem_cache_max_size = 32;
module_param(spl_kmem_cache_max_size, uint, 0644);
MODULE_PARM_DESC(spl_kmem_cache_max_size, "Maximum size of slab in MB");

unsigned int spl_kmem_cache_slab_limit = 0;
module_param(spl_kmem_cache_slab_limit, uint, 0644);
MODULE_PARM_DESC(spl_kmem_cache_slab_limit,
    "Objects less than N bytes use the Linux slab");

unsigned int spl_kmem_cache_kmem_limit = (PAGE_SIZE / 4);
module_param(spl_kmem_cache_kmem_limit, uint, 0644);
MODULE_PARM_DESC(spl_kmem_cache_kmem_limit,
    "Objects less than N bytes use the kmalloc");

/*
 * The minimum amount of memory measured in pages to be free at all
 * times on the system.  This is similar to Linux's zone->pages_min
 * multiplied by the number of zones and is sized based on that.
 */
pgcnt_t minfree = 0;
EXPORT_SYMBOL(minfree);

/*
 * The desired amount of memory measured in pages to be free at all
 * times on the system.  This is similar to Linux's zone->pages_low
 * multiplied by the number of zones and is sized based on that.
 * Assuming all zones are being used roughly equally, when we drop
 * below this threshold asynchronous page reclamation is triggered.
 */
pgcnt_t desfree = 0;
EXPORT_SYMBOL(desfree);

/*
 * When above this amount of memory measures in pages the system is
 * determined to have enough free memory.  This is similar to Linux's
 * zone->pages_high multiplied by the number of zones and is sized based
 * on that.  Assuming all zones are being used roughly equally, when
 * asynchronous page reclamation reaches this threshold it stops.
 */
pgcnt_t lotsfree = 0;
EXPORT_SYMBOL(lotsfree);

/* Unused always 0 in this implementation */
pgcnt_t needfree = 0;
EXPORT_SYMBOL(needfree);

pgcnt_t swapfs_minfree = 0;
EXPORT_SYMBOL(swapfs_minfree);

pgcnt_t swapfs_reserve = 0;
EXPORT_SYMBOL(swapfs_reserve);

vmem_t *heap_arena = NULL;
EXPORT_SYMBOL(heap_arena);

vmem_t *zio_alloc_arena = NULL;
EXPORT_SYMBOL(zio_alloc_arena);

vmem_t *zio_arena = NULL;
EXPORT_SYMBOL(zio_arena);

#ifndef HAVE_GET_VMALLOC_INFO
get_vmalloc_info_t get_vmalloc_info_fn = SYMBOL_POISON;
EXPORT_SYMBOL(get_vmalloc_info_fn);
#endif /* HAVE_GET_VMALLOC_INFO */

#ifdef HAVE_PGDAT_HELPERS
# ifndef HAVE_FIRST_ONLINE_PGDAT
first_online_pgdat_t first_online_pgdat_fn = SYMBOL_POISON;
EXPORT_SYMBOL(first_online_pgdat_fn);
# endif /* HAVE_FIRST_ONLINE_PGDAT */

# ifndef HAVE_NEXT_ONLINE_PGDAT
next_online_pgdat_t next_online_pgdat_fn = SYMBOL_POISON;
EXPORT_SYMBOL(next_online_pgdat_fn);
# endif /* HAVE_NEXT_ONLINE_PGDAT */

# ifndef HAVE_NEXT_ZONE
next_zone_t next_zone_fn = SYMBOL_POISON;
EXPORT_SYMBOL(next_zone_fn);
# endif /* HAVE_NEXT_ZONE */

#else /* HAVE_PGDAT_HELPERS */

# ifndef HAVE_PGDAT_LIST
struct pglist_data *pgdat_list_addr = SYMBOL_POISON;
EXPORT_SYMBOL(pgdat_list_addr);
# endif /* HAVE_PGDAT_LIST */

#endif /* HAVE_PGDAT_HELPERS */

#ifdef NEED_GET_ZONE_COUNTS
# ifndef HAVE_GET_ZONE_COUNTS
get_zone_counts_t get_zone_counts_fn = SYMBOL_POISON;
EXPORT_SYMBOL(get_zone_counts_fn);
# endif /* HAVE_GET_ZONE_COUNTS */

unsigned long
spl_global_page_state(spl_zone_stat_item_t item)
{
        unsigned long active;
        unsigned long inactive;
        unsigned long free;

        get_zone_counts(&active, &inactive, &free);
        switch (item) {
        case SPL_NR_FREE_PAGES: return free;
        case SPL_NR_INACTIVE:   return inactive;
        case SPL_NR_ACTIVE:     return active;
        default:                ASSERT(0); /* Unsupported */
        }

        return 0;
}
#else
# ifdef HAVE_GLOBAL_PAGE_STATE
unsigned long
spl_global_page_state(spl_zone_stat_item_t item)
{
        unsigned long pages = 0;

        switch (item) {
        case SPL_NR_FREE_PAGES:
#  ifdef HAVE_ZONE_STAT_ITEM_NR_FREE_PAGES
                pages += global_page_state(NR_FREE_PAGES);
#  endif
                break;
        case SPL_NR_INACTIVE:
#  ifdef HAVE_ZONE_STAT_ITEM_NR_INACTIVE
                pages += global_page_state(NR_INACTIVE);
#  endif
#  ifdef HAVE_ZONE_STAT_ITEM_NR_INACTIVE_ANON
                pages += global_page_state(NR_INACTIVE_ANON);
#  endif
#  ifdef HAVE_ZONE_STAT_ITEM_NR_INACTIVE_FILE
                pages += global_page_state(NR_INACTIVE_FILE);
#  endif
                break;
        case SPL_NR_ACTIVE:
#  ifdef HAVE_ZONE_STAT_ITEM_NR_ACTIVE
                pages += global_page_state(NR_ACTIVE);
#  endif
#  ifdef HAVE_ZONE_STAT_ITEM_NR_ACTIVE_ANON
                pages += global_page_state(NR_ACTIVE_ANON);
#  endif
#  ifdef HAVE_ZONE_STAT_ITEM_NR_ACTIVE_FILE
                pages += global_page_state(NR_ACTIVE_FILE);
#  endif
                break;
        default:
                ASSERT(0); /* Unsupported */
        }

        return pages;
}
# else
#  error "Both global_page_state() and get_zone_counts() unavailable"
# endif /* HAVE_GLOBAL_PAGE_STATE */
#endif /* NEED_GET_ZONE_COUNTS */
EXPORT_SYMBOL(spl_global_page_state);

#ifndef HAVE_SHRINK_DCACHE_MEMORY
shrink_dcache_memory_t shrink_dcache_memory_fn = SYMBOL_POISON;
EXPORT_SYMBOL(shrink_dcache_memory_fn);
#endif /* HAVE_SHRINK_DCACHE_MEMORY */

#ifndef HAVE_SHRINK_ICACHE_MEMORY
shrink_icache_memory_t shrink_icache_memory_fn = SYMBOL_POISON;
EXPORT_SYMBOL(shrink_icache_memory_fn);
#endif /* HAVE_SHRINK_ICACHE_MEMORY */

pgcnt_t
spl_kmem_availrmem(void)
{
        /* The amount of easily available memory */
        return (spl_global_page_state(SPL_NR_FREE_PAGES) +
                spl_global_page_state(SPL_NR_INACTIVE));
}
EXPORT_SYMBOL(spl_kmem_availrmem);

size_t
vmem_size(vmem_t *vmp, int typemask)
{
        struct vmalloc_info vmi;
        size_t size = 0;

        ASSERT(vmp == NULL);
        ASSERT(typemask & (VMEM_ALLOC | VMEM_FREE));

        get_vmalloc_info(&vmi);
        if (typemask & VMEM_ALLOC)
                size += (size_t)vmi.used;

        if (typemask & VMEM_FREE)
                size += (size_t)(VMALLOC_TOTAL - vmi.used);

        return size;
}
EXPORT_SYMBOL(vmem_size);

int
kmem_debugging(void)
{
        return 0;
}
EXPORT_SYMBOL(kmem_debugging);

#ifndef HAVE_KVASPRINTF
/* Simplified asprintf. */
char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap)
{
        unsigned int len;
        char *p;
        va_list aq;

        va_copy(aq, ap);
        len = vsnprintf(NULL, 0, fmt, aq);
        va_end(aq);

        p = kmalloc(len+1, gfp);
        if (!p)
                return NULL;

        vsnprintf(p, len+1, fmt, ap);

        return p;
}
EXPORT_SYMBOL(kvasprintf);
#endif /* HAVE_KVASPRINTF */

char *
kmem_vasprintf(const char *fmt, va_list ap)
{
        va_list aq;
        char *ptr;

        do {
                va_copy(aq, ap);
                ptr = kvasprintf(GFP_KERNEL, fmt, aq);
                va_end(aq);
        } while (ptr == NULL);

        return ptr;
}
EXPORT_SYMBOL(kmem_vasprintf);

char *
kmem_asprintf(const char *fmt, ...)
{
        va_list ap;
        char *ptr;

        do {
                va_start(ap, fmt);
                ptr = kvasprintf(GFP_KERNEL, fmt, ap);
                va_end(ap);
        } while (ptr == NULL);

        return ptr;
}
EXPORT_SYMBOL(kmem_asprintf);

static char *
__strdup(const char *str, int flags)
{
        char *ptr;
        int n;

        n = strlen(str);
        ptr = kmalloc_nofail(n + 1, flags);
        if (ptr)
                memcpy(ptr, str, n + 1);

        return ptr;
}

char *
strdup(const char *str)
{
        return __strdup(str, KM_SLEEP);
}
EXPORT_SYMBOL(strdup);

void
strfree(char *str)
{
        kfree(str);
}
EXPORT_SYMBOL(strfree);

/*
 * Memory allocation interfaces and debugging for basic kmem_*
 * and vmem_* style memory allocation.  When DEBUG_KMEM is enabled
 * the SPL will keep track of the total memory allocated, and
 * report any memory leaked when the module is unloaded.
 */
#ifdef DEBUG_KMEM

/* Shim layer memory accounting */
# ifdef HAVE_ATOMIC64_T
atomic64_t kmem_alloc_used = ATOMIC64_INIT(0);
unsigned long long kmem_alloc_max = 0;
atomic64_t vmem_alloc_used = ATOMIC64_INIT(0);
unsigned long long vmem_alloc_max = 0;
# else  /* HAVE_ATOMIC64_T */
atomic_t kmem_alloc_used = ATOMIC_INIT(0);
unsigned long long kmem_alloc_max = 0;
atomic_t vmem_alloc_used = ATOMIC_INIT(0);
unsigned long long vmem_alloc_max = 0;
# endif /* HAVE_ATOMIC64_T */

EXPORT_SYMBOL(kmem_alloc_used);
EXPORT_SYMBOL(kmem_alloc_max);
EXPORT_SYMBOL(vmem_alloc_used);
EXPORT_SYMBOL(vmem_alloc_max);

/* When DEBUG_KMEM_TRACKING is enabled not only will total bytes be tracked
 * but also the location of every alloc and free.  When the SPL module is
 * unloaded a list of all leaked addresses and where they were allocated
 * will be dumped to the console.  Enabling this feature has a significant
 * impact on performance but it makes finding memory leaks straight forward.
 *
 * Not surprisingly with debugging enabled the xmem_locks are very highly
 * contended particularly on xfree().  If we want to run with this detailed
 * debugging enabled for anything other than debugging  we need to minimize
 * the contention by moving to a lock per xmem_table entry model.
 */
# ifdef DEBUG_KMEM_TRACKING

#  define KMEM_HASH_BITS          10
#  define KMEM_TABLE_SIZE         (1 << KMEM_HASH_BITS)

#  define VMEM_HASH_BITS          10
#  define VMEM_TABLE_SIZE         (1 << VMEM_HASH_BITS)

typedef struct kmem_debug {
        struct hlist_node kd_hlist;     /* Hash node linkage */
        struct list_head kd_list;       /* List of all allocations */
        void *kd_addr;                  /* Allocation pointer */
        size_t kd_size;                 /* Allocation size */
        const char *kd_func;            /* Allocation function */
        int kd_line;                    /* Allocation line */
} kmem_debug_t;

spinlock_t kmem_lock;
struct hlist_head kmem_table[KMEM_TABLE_SIZE];
struct list_head kmem_list;

spinlock_t vmem_lock;
struct hlist_head vmem_table[VMEM_TABLE_SIZE];
struct list_head vmem_list;

EXPORT_SYMBOL(kmem_lock);
EXPORT_SYMBOL(kmem_table);
EXPORT_SYMBOL(kmem_list);

EXPORT_SYMBOL(vmem_lock);
EXPORT_SYMBOL(vmem_table);
EXPORT_SYMBOL(vmem_list);

static kmem_debug_t *
kmem_del_init(spinlock_t *lock, struct hlist_head *table, int bits, const void *addr)
{
        struct hlist_head *head;
        struct hlist_node *node;
        struct kmem_debug *p;
        unsigned long flags;
        SENTRY;

        spin_lock_irqsave(lock, flags);

        head = &table[hash_ptr((void *)addr, bits)];
        hlist_for_each(node, head) {
                p = list_entry(node, struct kmem_debug, kd_hlist);
                if (p->kd_addr == addr) {
                        hlist_del_init(&p->kd_hlist);
                        list_del_init(&p->kd_list);
                        spin_unlock_irqrestore(lock, flags);
                        return p;
                }
        }

        spin_unlock_irqrestore(lock, flags);

        SRETURN(NULL);
}

void *
kmem_alloc_track(size_t size, int flags, const char *func, int line,
    int node_alloc, int node)
{
        void *ptr = NULL;
        kmem_debug_t *dptr;
        unsigned long irq_flags;
        SENTRY;

        /* Function may be called with KM_NOSLEEP so failure is possible */
        dptr = (kmem_debug_t *) kmalloc_nofail(sizeof(kmem_debug_t),
            flags & ~__GFP_ZERO);

        if (unlikely(dptr == NULL)) {
                SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING, "debug "
                    "kmem_alloc(%ld, 0x%x) at %s:%d failed (%lld/%llu)\n",
                    sizeof(kmem_debug_t), flags, func, line,
                    kmem_alloc_used_read(), kmem_alloc_max);
        } else {
                /*
                 * Marked unlikely because we should never be doing this,
                 * we tolerate to up 2 pages but a single page is best.
                 */
                if (unlikely((size > PAGE_SIZE*2) && !(flags & KM_NODEBUG))) {
                        SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING, "large "
                            "kmem_alloc(%llu, 0x%x) at %s:%d (%lld/%llu)\n",
                            (unsigned long long) size, flags, func, line,
                            kmem_alloc_used_read(), kmem_alloc_max);
                        spl_debug_dumpstack(NULL);
                }

                /*
                 *  We use __strdup() below because the string pointed to by
                 * __FUNCTION__ might not be available by the time we want
                 * to print it since the module might have been unloaded.
                 * This can only fail in the KM_NOSLEEP case.
                 */
                dptr->kd_func = __strdup(func, flags & ~__GFP_ZERO);
                if (unlikely(dptr->kd_func == NULL)) {
                        kfree(dptr);
                        SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING,
                            "debug __strdup() at %s:%d failed (%lld/%llu)\n",
                            func, line, kmem_alloc_used_read(), kmem_alloc_max);
                        goto out;
                }

                /* Use the correct allocator */
                if (node_alloc) {
                        ASSERT(!(flags & __GFP_ZERO));
                        ptr = kmalloc_node_nofail(size, flags, node);
                } else if (flags & __GFP_ZERO) {
                        ptr = kzalloc_nofail(size, flags & ~__GFP_ZERO);
                } else {
                        ptr = kmalloc_nofail(size, flags);
                }

                if (unlikely(ptr == NULL)) {
                        kfree(dptr->kd_func);
                        kfree(dptr);
                        SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING, "kmem_alloc"
                            "(%llu, 0x%x) at %s:%d failed (%lld/%llu)\n",
                            (unsigned long long) size, flags, func, line,
                            kmem_alloc_used_read(), kmem_alloc_max);
                        goto out;
                }

                kmem_alloc_used_add(size);
                if (unlikely(kmem_alloc_used_read() > kmem_alloc_max))
                        kmem_alloc_max = kmem_alloc_used_read();

                INIT_HLIST_NODE(&dptr->kd_hlist);
                INIT_LIST_HEAD(&dptr->kd_list);

                dptr->kd_addr = ptr;
                dptr->kd_size = size;
                dptr->kd_line = line;

                spin_lock_irqsave(&kmem_lock, irq_flags);
                hlist_add_head(&dptr->kd_hlist,
                    &kmem_table[hash_ptr(ptr, KMEM_HASH_BITS)]);
                list_add_tail(&dptr->kd_list, &kmem_list);
                spin_unlock_irqrestore(&kmem_lock, irq_flags);

                SDEBUG_LIMIT(SD_INFO,
                    "kmem_alloc(%llu, 0x%x) at %s:%d = %p (%lld/%llu)\n",
                    (unsigned long long) size, flags, func, line, ptr,
                    kmem_alloc_used_read(), kmem_alloc_max);
        }
out:
        SRETURN(ptr);
}
EXPORT_SYMBOL(kmem_alloc_track);

void
kmem_free_track(const void *ptr, size_t size)
{
        kmem_debug_t *dptr;
        SENTRY;

        ASSERTF(ptr || size > 0, "ptr: %p, size: %llu", ptr,
            (unsigned long long) size);

        dptr = kmem_del_init(&kmem_lock, kmem_table, KMEM_HASH_BITS, ptr);

        /* Must exist in hash due to kmem_alloc() */
        ASSERT(dptr);

        /* Size must match */
        ASSERTF(dptr->kd_size == size, "kd_size (%llu) != size (%llu), "
            "kd_func = %s, kd_line = %d\n", (unsigned long long) dptr->kd_size,
            (unsigned long long) size, dptr->kd_func, dptr->kd_line);

        kmem_alloc_used_sub(size);
        SDEBUG_LIMIT(SD_INFO, "kmem_free(%p, %llu) (%lld/%llu)\n", ptr,
            (unsigned long long) size, kmem_alloc_used_read(),
            kmem_alloc_max);

        kfree(dptr->kd_func);

        memset((void *)dptr, 0x5a, sizeof(kmem_debug_t));
        kfree(dptr);

        memset((void *)ptr, 0x5a, size);
        kfree(ptr);

        SEXIT;
}
EXPORT_SYMBOL(kmem_free_track);

void *
vmem_alloc_track(size_t size, int flags, const char *func, int line)
{
        void *ptr = NULL;
        kmem_debug_t *dptr;
        unsigned long irq_flags;
        SENTRY;

        ASSERT(flags & KM_SLEEP);

        /* Function may be called with KM_NOSLEEP so failure is possible */
        dptr = (kmem_debug_t *) kmalloc_nofail(sizeof(kmem_debug_t),
            flags & ~__GFP_ZERO);
        if (unlikely(dptr == NULL)) {
                SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING, "debug "
                    "vmem_alloc(%ld, 0x%x) at %s:%d failed (%lld/%llu)\n",
                    sizeof(kmem_debug_t), flags, func, line,
                    vmem_alloc_used_read(), vmem_alloc_max);
        } else {
                /*
                 * We use __strdup() below because the string pointed to by
                 * __FUNCTION__ might not be available by the time we want
                 * to print it, since the module might have been unloaded.
                 * This can never fail because we have already asserted
                 * that flags is KM_SLEEP.
                 */
                dptr->kd_func = __strdup(func, flags & ~__GFP_ZERO);
                if (unlikely(dptr->kd_func == NULL)) {
                        kfree(dptr);
                        SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING,
                            "debug __strdup() at %s:%d failed (%lld/%llu)\n",
                            func, line, vmem_alloc_used_read(), vmem_alloc_max);
                        goto out;
                }

                /* Use the correct allocator */
                if (flags & __GFP_ZERO) {
                        ptr = vzalloc_nofail(size, flags & ~__GFP_ZERO);
                } else {
                        ptr = vmalloc_nofail(size, flags);
                }

                if (unlikely(ptr == NULL)) {
                        kfree(dptr->kd_func);
                        kfree(dptr);
                        SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING, "vmem_alloc"
                            "(%llu, 0x%x) at %s:%d failed (%lld/%llu)\n",
                            (unsigned long long) size, flags, func, line,
                            vmem_alloc_used_read(), vmem_alloc_max);
                        goto out;
                }

                vmem_alloc_used_add(size);
                if (unlikely(vmem_alloc_used_read() > vmem_alloc_max))
                        vmem_alloc_max = vmem_alloc_used_read();

                INIT_HLIST_NODE(&dptr->kd_hlist);
                INIT_LIST_HEAD(&dptr->kd_list);

                dptr->kd_addr = ptr;
                dptr->kd_size = size;
                dptr->kd_line = line;

                spin_lock_irqsave(&vmem_lock, irq_flags);
                hlist_add_head(&dptr->kd_hlist,
                    &vmem_table[hash_ptr(ptr, VMEM_HASH_BITS)]);
                list_add_tail(&dptr->kd_list, &vmem_list);
                spin_unlock_irqrestore(&vmem_lock, irq_flags);

                SDEBUG_LIMIT(SD_INFO,
                    "vmem_alloc(%llu, 0x%x) at %s:%d = %p (%lld/%llu)\n",
                    (unsigned long long) size, flags, func, line,
                    ptr, vmem_alloc_used_read(), vmem_alloc_max);
        }
out:
        SRETURN(ptr);
}
EXPORT_SYMBOL(vmem_alloc_track);

void
vmem_free_track(const void *ptr, size_t size)
{
        kmem_debug_t *dptr;
        SENTRY;

        ASSERTF(ptr || size > 0, "ptr: %p, size: %llu", ptr,
            (unsigned long long) size);

        dptr = kmem_del_init(&vmem_lock, vmem_table, VMEM_HASH_BITS, ptr);

        /* Must exist in hash due to vmem_alloc() */
        ASSERT(dptr);

        /* Size must match */
        ASSERTF(dptr->kd_size == size, "kd_size (%llu) != size (%llu), "
            "kd_func = %s, kd_line = %d\n", (unsigned long long) dptr->kd_size,
            (unsigned long long) size, dptr->kd_func, dptr->kd_line);

        vmem_alloc_used_sub(size);
        SDEBUG_LIMIT(SD_INFO, "vmem_free(%p, %llu) (%lld/%llu)\n", ptr,
            (unsigned long long) size, vmem_alloc_used_read(),
            vmem_alloc_max);

        kfree(dptr->kd_func);

        memset((void *)dptr, 0x5a, sizeof(kmem_debug_t));
        kfree(dptr);

        memset((void *)ptr, 0x5a, size);
        vfree(ptr);

        SEXIT;
}
EXPORT_SYMBOL(vmem_free_track);

# else /* DEBUG_KMEM_TRACKING */

void *
kmem_alloc_debug(size_t size, int flags, const char *func, int line,
    int node_alloc, int node)
{
        void *ptr;
        SENTRY;

        /*
         * Marked unlikely because we should never be doing this,
         * we tolerate to up 2 pages but a single page is best.
         */
        if (unlikely((size > PAGE_SIZE * 2) && !(flags & KM_NODEBUG))) {
                SDEBUG(SD_CONSOLE | SD_WARNING,
                    "large kmem_alloc(%llu, 0x%x) at %s:%d (%lld/%llu)\n",
                    (unsigned long long) size, flags, func, line,
                    kmem_alloc_used_read(), kmem_alloc_max);
                dump_stack();
        }

        /* Use the correct allocator */
        if (node_alloc) {
                ASSERT(!(flags & __GFP_ZERO));
                ptr = kmalloc_node_nofail(size, flags, node);
        } else if (flags & __GFP_ZERO) {
                ptr = kzalloc_nofail(size, flags & (~__GFP_ZERO));
        } else {
                ptr = kmalloc_nofail(size, flags);
        }

        if (unlikely(ptr == NULL)) {
                SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING,
                    "kmem_alloc(%llu, 0x%x) at %s:%d failed (%lld/%llu)\n",
                    (unsigned long long) size, flags, func, line,
                    kmem_alloc_used_read(), kmem_alloc_max);
        } else {
                kmem_alloc_used_add(size);
                if (unlikely(kmem_alloc_used_read() > kmem_alloc_max))
                        kmem_alloc_max = kmem_alloc_used_read();

                SDEBUG_LIMIT(SD_INFO,
                    "kmem_alloc(%llu, 0x%x) at %s:%d = %p (%lld/%llu)\n",
                    (unsigned long long) size, flags, func, line, ptr,
                    kmem_alloc_used_read(), kmem_alloc_max);
        }

        SRETURN(ptr);
}
EXPORT_SYMBOL(kmem_alloc_debug);

void
kmem_free_debug(const void *ptr, size_t size)
{
        SENTRY;

        ASSERTF(ptr || size > 0, "ptr: %p, size: %llu", ptr,
            (unsigned long long) size);

        kmem_alloc_used_sub(size);
        SDEBUG_LIMIT(SD_INFO, "kmem_free(%p, %llu) (%lld/%llu)\n", ptr,
            (unsigned long long) size, kmem_alloc_used_read(),
            kmem_alloc_max);
        kfree(ptr);

        SEXIT;
}
EXPORT_SYMBOL(kmem_free_debug);

void *
vmem_alloc_debug(size_t size, int flags, const char *func, int line)
{
        void *ptr;
        SENTRY;

        ASSERT(flags & KM_SLEEP);

        /* Use the correct allocator */
        if (flags & __GFP_ZERO) {
                ptr = vzalloc_nofail(size, flags & (~__GFP_ZERO));
        } else {
                ptr = vmalloc_nofail(size, flags);
        }

        if (unlikely(ptr == NULL)) {
                SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING,
                    "vmem_alloc(%llu, 0x%x) at %s:%d failed (%lld/%llu)\n",
                    (unsigned long long) size, flags, func, line,
                    vmem_alloc_used_read(), vmem_alloc_max);
        } else {
                vmem_alloc_used_add(size);
                if (unlikely(vmem_alloc_used_read() > vmem_alloc_max))
                        vmem_alloc_max = vmem_alloc_used_read();

                SDEBUG_LIMIT(SD_INFO, "vmem_alloc(%llu, 0x%x) = %p "
                    "(%lld/%llu)\n", (unsigned long long) size, flags, ptr,
                    vmem_alloc_used_read(), vmem_alloc_max);
        }

        SRETURN(ptr);
}
EXPORT_SYMBOL(vmem_alloc_debug);

void
vmem_free_debug(const void *ptr, size_t size)
{
        SENTRY;

        ASSERTF(ptr || size > 0, "ptr: %p, size: %llu", ptr,
            (unsigned long long) size);

        vmem_alloc_used_sub(size);
        SDEBUG_LIMIT(SD_INFO, "vmem_free(%p, %llu) (%lld/%llu)\n", ptr,
            (unsigned long long) size, vmem_alloc_used_read(),
            vmem_alloc_max);
        vfree(ptr);

        SEXIT;
}
EXPORT_SYMBOL(vmem_free_debug);

# endif /* DEBUG_KMEM_TRACKING */
#endif /* DEBUG_KMEM */

/*
 * Slab allocation interfaces
 *
 * While the Linux slab implementation was inspired by the Solaris
 * implementation I cannot use it to emulate the Solaris APIs.  I
 * require two features which are not provided by the Linux slab.
 *
 * 1) Constructors AND destructors.  Recent versions of the Linux
 *    kernel have removed support for destructors.  This is a deal
 *    breaker for the SPL which contains particularly expensive
 *    initializers for mutex's, condition variables, etc.  We also
 *    require a minimal level of cleanup for these data types unlike
 *    many Linux data type which do need to be explicitly destroyed.
 *
 * 2) Virtual address space backed slab.  Callers of the Solaris slab
 *    expect it to work well for both small are very large allocations.
 *    Because of memory fragmentation the Linux slab which is backed
 *    by kmalloc'ed memory performs very badly when confronted with
 *    large numbers of large allocations.  Basing the slab on the
 *    virtual address space removes the need for contiguous pages
 *    and greatly improve performance for large allocations.
 *
 * For these reasons, the SPL has its own slab implementation with
 * the needed features.  It is not as highly optimized as either the
 * Solaris or Linux slabs, but it should get me most of what is
 * needed until it can be optimized or obsoleted by another approach.
 *
 * One serious concern I do have about this method is the relatively
 * small virtual address space on 32bit arches.  This will seriously
 * constrain the size of the slab caches and their performance.
 *
 * XXX: Improve the partial slab list by carefully maintaining a
 *      strict ordering of fullest to emptiest slabs based on
 *      the slab reference count.  This guarantees the when freeing
 *      slabs back to the system we need only linearly traverse the
 *      last N slabs in the list to discover all the freeable slabs.
 *
 * XXX: NUMA awareness for optionally allocating memory close to a
 *      particular core.  This can be advantageous if you know the slab
 *      object will be short lived and primarily accessed from one core.
 *
 * XXX: Slab coloring may also yield performance improvements and would
 *      be desirable to implement.
 */

struct list_head spl_kmem_cache_list;   /* List of caches */
struct rw_semaphore spl_kmem_cache_sem; /* Cache list lock */
taskq_t *spl_kmem_cache_taskq;          /* Task queue for ageing / reclaim */

static void spl_cache_shrink(spl_kmem_cache_t *skc, void *obj);

SPL_SHRINKER_CALLBACK_FWD_DECLARE(spl_kmem_cache_generic_shrinker);
SPL_SHRINKER_DECLARE(spl_kmem_cache_shrinker,
        spl_kmem_cache_generic_shrinker, KMC_DEFAULT_SEEKS);

static void *
kv_alloc(spl_kmem_cache_t *skc, int size, int flags)
{
        void *ptr;

        ASSERT(ISP2(size));

        if (skc->skc_flags & KMC_KMEM)
                ptr = (void *)__get_free_pages(flags | __GFP_COMP,
                    get_order(size));
        else
                ptr = __vmalloc(size, flags | __GFP_HIGHMEM, PAGE_KERNEL);

        /* Resulting allocated memory will be page aligned */
        ASSERT(IS_P2ALIGNED(ptr, PAGE_SIZE));

        return ptr;
}

static void
kv_free(spl_kmem_cache_t *skc, void *ptr, int size)
{
        ASSERT(IS_P2ALIGNED(ptr, PAGE_SIZE));
        ASSERT(ISP2(size));

        /*
         * The Linux direct reclaim path uses this out of band value to
         * determine if forward progress is being made.  Normally this is
         * incremented by kmem_freepages() which is part of the various
         * Linux slab implementations.  However, since we are using none
         * of that infrastructure we are responsible for incrementing it.
         */
        if (current->reclaim_state)
                current->reclaim_state->reclaimed_slab += size >> PAGE_SHIFT;

        if (skc->skc_flags & KMC_KMEM)
                free_pages((unsigned long)ptr, get_order(size));
        else
                vfree(ptr);
}

/*
 * Required space for each aligned sks.
 */
static inline uint32_t
spl_sks_size(spl_kmem_cache_t *skc)
{
        return P2ROUNDUP_TYPED(sizeof(spl_kmem_slab_t),
               skc->skc_obj_align, uint32_t);
}

/*
 * Required space for each aligned object.
 */
static inline uint32_t
spl_obj_size(spl_kmem_cache_t *skc)
{
        uint32_t align = skc->skc_obj_align;

        return P2ROUNDUP_TYPED(skc->skc_obj_size, align, uint32_t) +
               P2ROUNDUP_TYPED(sizeof(spl_kmem_obj_t), align, uint32_t);
}

/*
 * Lookup the spl_kmem_object_t for an object given that object.
 */
static inline spl_kmem_obj_t *
spl_sko_from_obj(spl_kmem_cache_t *skc, void *obj)
{
        return obj + P2ROUNDUP_TYPED(skc->skc_obj_size,
               skc->skc_obj_align, uint32_t);
}

/*
 * Required space for each offslab object taking in to account alignment
 * restrictions and the power-of-two requirement of kv_alloc().
 */
static inline uint32_t
spl_offslab_size(spl_kmem_cache_t *skc)
{
        return 1UL << (highbit(spl_obj_size(skc)) + 1);
}

/*
 * It's important that we pack the spl_kmem_obj_t structure and the
 * actual objects in to one large address space to minimize the number
 * of calls to the allocator.  It is far better to do a few large
 * allocations and then subdivide it ourselves.  Now which allocator
 * we use requires balancing a few trade offs.
 *
 * For small objects we use kmem_alloc() because as long as you are
 * only requesting a small number of pages (ideally just one) its cheap.
 * However, when you start requesting multiple pages with kmem_alloc()
 * it gets increasingly expensive since it requires contiguous pages.
 * For this reason we shift to vmem_alloc() for slabs of large objects
 * which removes the need for contiguous pages.  We do not use
 * vmem_alloc() in all cases because there is significant locking
 * overhead in __get_vm_area_node().  This function takes a single
 * global lock when acquiring an available virtual address range which
 * serializes all vmem_alloc()'s for all slab caches.  Using slightly
 * different allocation functions for small and large objects should
 * give us the best of both worlds.
 *
 * KMC_ONSLAB                       KMC_OFFSLAB
 *
 * +------------------------+       +-----------------+
 * | spl_kmem_slab_t --+-+  |       | spl_kmem_slab_t |---+-+
 * | skc_obj_size    <-+ |  |       +-----------------+   | |
 * | spl_kmem_obj_t      |  |                             | |
 * | skc_obj_size    <---+  |       +-----------------+   | |
 * | spl_kmem_obj_t      |  |       | skc_obj_size    | <-+ |
 * | ...                 v  |       | spl_kmem_obj_t  |     |
 * +------------------------+       +-----------------+     v
 */
static spl_kmem_slab_t *
spl_slab_alloc(spl_kmem_cache_t *skc, int flags)
{
        spl_kmem_slab_t *sks;
        spl_kmem_obj_t *sko, *n;
        void *base, *obj;
        uint32_t obj_size, offslab_size = 0;
        int i,  rc = 0;

        base = kv_alloc(skc, skc->skc_slab_size, flags);
        if (base == NULL)
                SRETURN(NULL);

        sks = (spl_kmem_slab_t *)base;
        sks->sks_magic = SKS_MAGIC;
        sks->sks_objs = skc->skc_slab_objs;
        sks->sks_age = jiffies;
        sks->sks_cache = skc;
        INIT_LIST_HEAD(&sks->sks_list);
        INIT_LIST_HEAD(&sks->sks_free_list);
        sks->sks_ref = 0;
        obj_size = spl_obj_size(skc);

        if (skc->skc_flags & KMC_OFFSLAB)
                offslab_size = spl_offslab_size(skc);

        for (i = 0; i < sks->sks_objs; i++) {
                if (skc->skc_flags & KMC_OFFSLAB) {
                        obj = kv_alloc(skc, offslab_size, flags);
                        if (!obj)
                                SGOTO(out, rc = -ENOMEM);
                } else {
                        obj = base + spl_sks_size(skc) + (i * obj_size);
                }

                ASSERT(IS_P2ALIGNED(obj, skc->skc_obj_align));
                sko = spl_sko_from_obj(skc, obj);
                sko->sko_addr = obj;
                sko->sko_magic = SKO_MAGIC;
                sko->sko_slab = sks;
                INIT_LIST_HEAD(&sko->sko_list);
                list_add_tail(&sko->sko_list, &sks->sks_free_list);
        }

        list_for_each_entry(sko, &sks->sks_free_list, sko_list)
                if (skc->skc_ctor)
                        skc->skc_ctor(sko->sko_addr, skc->skc_private, flags);
out:
        if (rc) {
                if (skc->skc_flags & KMC_OFFSLAB)
                        list_for_each_entry_safe(sko, n, &sks->sks_free_list,
                                                 sko_list)
                                kv_free(skc, sko->sko_addr, offslab_size);

                kv_free(skc, base, skc->skc_slab_size);
                sks = NULL;
        }

        SRETURN(sks);
}

/*
 * Remove a slab from complete or partial list, it must be called with
 * the 'skc->skc_lock' held but the actual free must be performed
 * outside the lock to prevent deadlocking on vmem addresses.
 */
static void
spl_slab_free(spl_kmem_slab_t *sks,
              struct list_head *sks_list, struct list_head *sko_list)
{
        spl_kmem_cache_t *skc;
        SENTRY;

        ASSERT(sks->sks_magic == SKS_MAGIC);
        ASSERT(sks->sks_ref == 0);

        skc = sks->sks_cache;
        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT(spin_is_locked(&skc->skc_lock));

        /*
         * Update slab/objects counters in the cache, then remove the
         * slab from the skc->skc_partial_list.  Finally add the slab
         * and all its objects in to the private work lists where the
         * destructors will be called and the memory freed to the system.
         */
        skc->skc_obj_total -= sks->sks_objs;
        skc->skc_slab_total--;
        list_del(&sks->sks_list);
        list_add(&sks->sks_list, sks_list);
        list_splice_init(&sks->sks_free_list, sko_list);

        SEXIT;
}

/*
 * Traverses all the partial slabs attached to a cache and free those
 * which which are currently empty, and have not been touched for
 * skc_delay seconds to  avoid thrashing.  The count argument is
 * passed to optionally cap the number of slabs reclaimed, a count
 * of zero means try and reclaim everything.  When flag is set we
 * always free an available slab regardless of age.
 */
static void
spl_slab_reclaim(spl_kmem_cache_t *skc, int count, int flag)
{
        spl_kmem_slab_t *sks, *m;
        spl_kmem_obj_t *sko, *n;
        LIST_HEAD(sks_list);
        LIST_HEAD(sko_list);
        uint32_t size = 0;
        int i = 0;
        SENTRY;

        /*
         * Move empty slabs and objects which have not been touched in
         * skc_delay seconds on to private lists to be freed outside
         * the spin lock.  This delay time is important to avoid thrashing
         * however when flag is set the delay will not be used.
         */
        spin_lock(&skc->skc_lock);
        list_for_each_entry_safe_reverse(sks,m,&skc->skc_partial_list,sks_list){
                /*
                 * All empty slabs are at the end of skc->skc_partial_list,
                 * therefore once a non-empty slab is found we can stop
                 * scanning.  Additionally, stop when reaching the target
                 * reclaim 'count' if a non-zero threshold is given.
                 */
                if ((sks->sks_ref > 0) || (count && i >= count))
                        break;

                if (time_after(jiffies,sks->sks_age+skc->skc_delay*HZ)||flag) {
                        spl_slab_free(sks, &sks_list, &sko_list);
                        i++;
                }
        }
        spin_unlock(&skc->skc_lock);

        /*
         * The following two loops ensure all the object destructors are
         * run, any offslab objects are freed, and the slabs themselves
         * are freed.  This is all done outside the skc->skc_lock since
         * this allows the destructor to sleep, and allows us to perform
         * a conditional reschedule when a freeing a large number of
         * objects and slabs back to the system.
         */
        if (skc->skc_flags & KMC_OFFSLAB)
                size = spl_offslab_size(skc);

        list_for_each_entry_safe(sko, n, &sko_list, sko_list) {
                ASSERT(sko->sko_magic == SKO_MAGIC);

                if (skc->skc_dtor)
                        skc->skc_dtor(sko->sko_addr, skc->skc_private);

                if (skc->skc_flags & KMC_OFFSLAB)
                        kv_free(skc, sko->sko_addr, size);
        }

        list_for_each_entry_safe(sks, m, &sks_list, sks_list) {
                ASSERT(sks->sks_magic == SKS_MAGIC);
                kv_free(skc, sks, skc->skc_slab_size);
        }

        SEXIT;
}

static spl_kmem_emergency_t *
spl_emergency_search(struct rb_root *root, void *obj)
{
        struct rb_node *node = root->rb_node;
        spl_kmem_emergency_t *ske;
        unsigned long address = (unsigned long)obj;

        while (node) {
                ske = container_of(node, spl_kmem_emergency_t, ske_node);

                if (address < (unsigned long)ske->ske_obj)
                        node = node->rb_left;
                else if (address > (unsigned long)ske->ske_obj)
                        node = node->rb_right;
                else
                        return ske;
        }

        return NULL;
}

static int
spl_emergency_insert(struct rb_root *root, spl_kmem_emergency_t *ske)
{
        struct rb_node **new = &(root->rb_node), *parent = NULL;
        spl_kmem_emergency_t *ske_tmp;
        unsigned long address = (unsigned long)ske->ske_obj;

        while (*new) {
                ske_tmp = container_of(*new, spl_kmem_emergency_t, ske_node);

                parent = *new;
                if (address < (unsigned long)ske_tmp->ske_obj)
                        new = &((*new)->rb_left);
                else if (address > (unsigned long)ske_tmp->ske_obj)
                        new = &((*new)->rb_right);
                else
                        return 0;
        }

        rb_link_node(&ske->ske_node, parent, new);
        rb_insert_color(&ske->ske_node, root);

        return 1;
}

/*
 * Allocate a single emergency object and track it in a red black tree.
 */
static int
spl_emergency_alloc(spl_kmem_cache_t *skc, int flags, void **obj)
{
        spl_kmem_emergency_t *ske;
        int empty;
        SENTRY;

        /* Last chance use a partial slab if one now exists */
        spin_lock(&skc->skc_lock);
        empty = list_empty(&skc->skc_partial_list);
        spin_unlock(&skc->skc_lock);
        if (!empty)
                SRETURN(-EEXIST);

        ske = kmalloc(sizeof(*ske), flags);
        if (ske == NULL)
                SRETURN(-ENOMEM);

        ske->ske_obj = kmalloc(skc->skc_obj_size, flags);
        if (ske->ske_obj == NULL) {
                kfree(ske);
                SRETURN(-ENOMEM);
        }

        spin_lock(&skc->skc_lock);
        empty = spl_emergency_insert(&skc->skc_emergency_tree, ske);
        if (likely(empty)) {
                skc->skc_obj_total++;
                skc->skc_obj_emergency++;
                if (skc->skc_obj_emergency > skc->skc_obj_emergency_max)
                        skc->skc_obj_emergency_max = skc->skc_obj_emergency;
        }
        spin_unlock(&skc->skc_lock);

        if (unlikely(!empty)) {
                kfree(ske->ske_obj);
                kfree(ske);
                SRETURN(-EINVAL);
        }

        if (skc->skc_ctor)
                skc->skc_ctor(ske->ske_obj, skc->skc_private, flags);

        *obj = ske->ske_obj;

        SRETURN(0);
}

/*
 * Locate the passed object in the red black tree and free it.
 */
static int
spl_emergency_free(spl_kmem_cache_t *skc, void *obj)
{
        spl_kmem_emergency_t *ske;
        SENTRY;

        spin_lock(&skc->skc_lock);
        ske = spl_emergency_search(&skc->skc_emergency_tree, obj);
        if (likely(ske)) {
                rb_erase(&ske->ske_node, &skc->skc_emergency_tree);
                skc->skc_obj_emergency--;
                skc->skc_obj_total--;
        }
        spin_unlock(&skc->skc_lock);

        if (unlikely(ske == NULL))
                SRETURN(-ENOENT);

        if (skc->skc_dtor)
                skc->skc_dtor(ske->ske_obj, skc->skc_private);

        kfree(ske->ske_obj);
        kfree(ske);

        SRETURN(0);
}

/*
 * Release objects from the per-cpu magazine back to their slab.  The flush
 * argument contains the max number of entries to remove from the magazine.
 */
static void
__spl_cache_flush(spl_kmem_cache_t *skc, spl_kmem_magazine_t *skm, int flush)
{
        int i, count = MIN(flush, skm->skm_avail);
        SENTRY;

        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT(skm->skm_magic == SKM_MAGIC);
        ASSERT(spin_is_locked(&skc->skc_lock));

        for (i = 0; i < count; i++)
                spl_cache_shrink(skc, skm->skm_objs[i]);

        skm->skm_avail -= count;
        memmove(skm->skm_objs, &(skm->skm_objs[count]),
                sizeof(void *) * skm->skm_avail);

        SEXIT;
}

static void
spl_cache_flush(spl_kmem_cache_t *skc, spl_kmem_magazine_t *skm, int flush)
{
        spin_lock(&skc->skc_lock);
        __spl_cache_flush(skc, skm, flush);
        spin_unlock(&skc->skc_lock);
}

static void
spl_magazine_age(void *data)
{
        spl_kmem_cache_t *skc = (spl_kmem_cache_t *)data;
        spl_kmem_magazine_t *skm = skc->skc_mag[smp_processor_id()];

        ASSERT(skm->skm_magic == SKM_MAGIC);
        ASSERT(skm->skm_cpu == smp_processor_id());
        ASSERT(irqs_disabled());

        /* There are no available objects or they are too young to age out */
        if ((skm->skm_avail == 0) ||
            time_before(jiffies, skm->skm_age + skc->skc_delay * HZ))
                return;

        /*
         * Because we're executing in interrupt context we may have
         * interrupted the holder of this lock.  To avoid a potential
         * deadlock return if the lock is contended.
         */
        if (!spin_trylock(&skc->skc_lock))
                return;

        __spl_cache_flush(skc, skm, skm->skm_refill);
        spin_unlock(&skc->skc_lock);
}

/*
 * Called regularly to keep a downward pressure on the cache.
 *
 * Objects older than skc->skc_delay seconds in the per-cpu magazines will
 * be returned to the caches.  This is done to prevent idle magazines from
 * holding memory which could be better used elsewhere.  The delay is
 * present to prevent thrashing the magazine.
 *
 * The newly released objects may result in empty partial slabs.  Those
 * slabs should be released to the system.  Otherwise moving the objects
 * out of the magazines is just wasted work.
 */
static void
spl_cache_age(void *data)
{
        spl_kmem_cache_t *skc = (spl_kmem_cache_t *)data;
        taskqid_t id = 0;

        ASSERT(skc->skc_magic == SKC_MAGIC);

        /* Dynamically disabled at run time */
        if (!(spl_kmem_cache_expire & KMC_EXPIRE_AGE))
                return;

        atomic_inc(&skc->skc_ref);

        if (!(skc->skc_flags & KMC_NOMAGAZINE))
                spl_on_each_cpu(spl_magazine_age, skc, 1);

        spl_slab_reclaim(skc, skc->skc_reap, 0);

        while (!test_bit(KMC_BIT_DESTROY, &skc->skc_flags) && !id) {
                id = taskq_dispatch_delay(
                    spl_kmem_cache_taskq, spl_cache_age, skc, TQ_SLEEP,
                    ddi_get_lbolt() + skc->skc_delay / 3 * HZ);

                /* Destroy issued after dispatch immediately cancel it */
                if (test_bit(KMC_BIT_DESTROY, &skc->skc_flags) && id)
                        taskq_cancel_id(spl_kmem_cache_taskq, id);
        }

        spin_lock(&skc->skc_lock);
        skc->skc_taskqid = id;
        spin_unlock(&skc->skc_lock);

        atomic_dec(&skc->skc_ref);
}

/*
 * Size a slab based on the size of each aligned object plus spl_kmem_obj_t.
 * When on-slab we want to target spl_kmem_cache_obj_per_slab.  However,
 * for very small objects we may end up with more than this so as not
 * to waste space in the minimal allocation of a single page.  Also for
 * very large objects we may use as few as spl_kmem_cache_obj_per_slab_min,
 * lower than this and we will fail.
 */
static int
spl_slab_size(spl_kmem_cache_t *skc, uint32_t *objs, uint32_t *size)
{
        uint32_t sks_size, obj_size, max_size;

        if (skc->skc_flags & KMC_OFFSLAB) {
                *objs = spl_kmem_cache_obj_per_slab;
                *size = P2ROUNDUP(sizeof(spl_kmem_slab_t), PAGE_SIZE);
                SRETURN(0);
        } else {
                sks_size = spl_sks_size(skc);
                obj_size = spl_obj_size(skc);

                if (skc->skc_flags & KMC_KMEM)
                        max_size = ((uint32_t)1 << (MAX_ORDER-3)) * PAGE_SIZE;
                else
                        max_size = (spl_kmem_cache_max_size * 1024 * 1024);

                /* Power of two sized slab */
                for (*size = PAGE_SIZE; *size <= max_size; *size *= 2) {
                        *objs = (*size - sks_size) / obj_size;
                        if (*objs >= spl_kmem_cache_obj_per_slab)
                                SRETURN(0);
                }

                /*
                 * Unable to satisfy target objects per slab, fall back to
                 * allocating a maximally sized slab and assuming it can
                 * contain the minimum objects count use it.  If not fail.
                 */
                *size = max_size;
                *objs = (*size - sks_size) / obj_size;
                if (*objs >= (spl_kmem_cache_obj_per_slab_min))
                        SRETURN(0);
        }

        SRETURN(-ENOSPC);
}

/*
 * Make a guess at reasonable per-cpu magazine size based on the size of
 * each object and the cost of caching N of them in each magazine.  Long
 * term this should really adapt based on an observed usage heuristic.
 */
static int
spl_magazine_size(spl_kmem_cache_t *skc)
{
        uint32_t obj_size = spl_obj_size(skc);
        int size;
        SENTRY;

        /* Per-magazine sizes below assume a 4Kib page size */
        if (obj_size > (PAGE_SIZE * 256))
                size = 4;  /* Minimum 4Mib per-magazine */
        else if (obj_size > (PAGE_SIZE * 32))
                size = 16; /* Minimum 2Mib per-magazine */
        else if (obj_size > (PAGE_SIZE))
                size = 64; /* Minimum 256Kib per-magazine */
        else if (obj_size > (PAGE_SIZE / 4))
                size = 128; /* Minimum 128Kib per-magazine */
        else
                size = 256;

        SRETURN(size);
}

/*
 * Allocate a per-cpu magazine to associate with a specific core.
 */
static spl_kmem_magazine_t *
spl_magazine_alloc(spl_kmem_cache_t *skc, int cpu)
{
        spl_kmem_magazine_t *skm;
        int size = sizeof(spl_kmem_magazine_t) +
                   sizeof(void *) * skc->skc_mag_size;
        SENTRY;

        skm = kmem_alloc_node(size, KM_SLEEP, cpu_to_node(cpu));
        if (skm) {
                skm->skm_magic = SKM_MAGIC;
                skm->skm_avail = 0;
                skm->skm_size = skc->skc_mag_size;
                skm->skm_refill = skc->skc_mag_refill;
                skm->skm_cache = skc;
                skm->skm_age = jiffies;
                skm->skm_cpu = cpu;
        }

        SRETURN(skm);
}

/*
 * Free a per-cpu magazine associated with a specific core.
 */
static void
spl_magazine_free(spl_kmem_magazine_t *skm)
{
        int size = sizeof(spl_kmem_magazine_t) +
                   sizeof(void *) * skm->skm_size;

        SENTRY;
        ASSERT(skm->skm_magic == SKM_MAGIC);
        ASSERT(skm->skm_avail == 0);

        kmem_free(skm, size);
        SEXIT;
}

/*
 * Create all pre-cpu magazines of reasonable sizes.
 */
static int
spl_magazine_create(spl_kmem_cache_t *skc)
{
        int i;
        SENTRY;

        if (skc->skc_flags & KMC_NOMAGAZINE)
                SRETURN(0);

        skc->skc_mag_size = spl_magazine_size(skc);
        skc->skc_mag_refill = (skc->skc_mag_size + 1) / 2;

        for_each_online_cpu(i) {
                skc->skc_mag[i] = spl_magazine_alloc(skc, i);
                if (!skc->skc_mag[i]) {
                        for (i--; i >= 0; i--)
                                spl_magazine_free(skc->skc_mag[i]);

                        SRETURN(-ENOMEM);
                }
        }

        SRETURN(0);
}

/*
 * Destroy all pre-cpu magazines.
 */
static void
spl_magazine_destroy(spl_kmem_cache_t *skc)
{
        spl_kmem_magazine_t *skm;
        int i;
        SENTRY;

        if (skc->skc_flags & KMC_NOMAGAZINE) {
                SEXIT;
                return;
        }

        for_each_online_cpu(i) {
                skm = skc->skc_mag[i];
                spl_cache_flush(skc, skm, skm->skm_avail);
                spl_magazine_free(skm);
        }

        SEXIT;
}

/*
 * Create a object cache based on the following arguments:
 * name         cache name
 * size         cache object size
 * align        cache object alignment
 * ctor         cache object constructor
 * dtor         cache object destructor
 * reclaim      cache object reclaim
 * priv         cache private data for ctor/dtor/reclaim
 * vmp          unused must be NULL
 * flags
 *      KMC_NOTOUCH     Disable cache object aging (unsupported)
 *      KMC_NODEBUG     Disable debugging (unsupported)
 *      KMC_NOHASH      Disable hashing (unsupported)
 *      KMC_QCACHE      Disable qcache (unsupported)
 *      KMC_NOMAGAZINE  Enabled for kmem/vmem, Disabled for Linux slab
 *      KMC_KMEM        Force kmem backed cache
 *      KMC_VMEM        Force vmem backed cache
 *      KMC_SLAB        Force Linux slab backed cache
 *      KMC_OFFSLAB     Locate objects off the slab
 */
spl_kmem_cache_t *
spl_kmem_cache_create(char *name, size_t size, size_t align,
                      spl_kmem_ctor_t ctor,
                      spl_kmem_dtor_t dtor,
                      spl_kmem_reclaim_t reclaim,
                      void *priv, void *vmp, int flags)
{
        spl_kmem_cache_t *skc;
        int rc;
        SENTRY;

        ASSERTF(!(flags & KMC_NOMAGAZINE), "Bad KMC_NOMAGAZINE (%x)\n", flags);
        ASSERTF(!(flags & KMC_NOHASH), "Bad KMC_NOHASH (%x)\n", flags);
        ASSERTF(!(flags & KMC_QCACHE), "Bad KMC_QCACHE (%x)\n", flags);
        ASSERT(vmp == NULL);

        might_sleep();

        /*
         * Allocate memory for a new cache an initialize it.  Unfortunately,
         * this usually ends up being a large allocation of ~32k because
         * we need to allocate enough memory for the worst case number of
         * cpus in the magazine, skc_mag[NR_CPUS].  Because of this we
         * explicitly pass KM_NODEBUG to suppress the kmem warning
         */
        skc = kmem_zalloc(sizeof(*skc), KM_SLEEP| KM_NODEBUG);
        if (skc == NULL)
                SRETURN(NULL);

        skc->skc_magic = SKC_MAGIC;
        skc->skc_name_size = strlen(name) + 1;
        skc->skc_name = (char *)kmem_alloc(skc->skc_name_size, KM_SLEEP);
        if (skc->skc_name == NULL) {
                kmem_free(skc, sizeof(*skc));
                SRETURN(NULL);
        }
        strncpy(skc->skc_name, name, skc->skc_name_size);

        skc->skc_ctor = ctor;
        skc->skc_dtor = dtor;
        skc->skc_reclaim = reclaim;
        skc->skc_private = priv;
        skc->skc_vmp = vmp;
        skc->skc_linux_cache = NULL;
        skc->skc_flags = flags;
        skc->skc_obj_size = size;
        skc->skc_obj_align = SPL_KMEM_CACHE_ALIGN;
        skc->skc_delay = SPL_KMEM_CACHE_DELAY;
        skc->skc_reap = SPL_KMEM_CACHE_REAP;
        atomic_set(&skc->skc_ref, 0);

        INIT_LIST_HEAD(&skc->skc_list);
        INIT_LIST_HEAD(&skc->skc_complete_list);
        INIT_LIST_HEAD(&skc->skc_partial_list);
        skc->skc_emergency_tree = RB_ROOT;
        spin_lock_init(&skc->skc_lock);
        init_waitqueue_head(&skc->skc_waitq);
        skc->skc_slab_fail = 0;
        skc->skc_slab_create = 0;
        skc->skc_slab_destroy = 0;
        skc->skc_slab_total = 0;
        skc->skc_slab_alloc = 0;
        skc->skc_slab_max = 0;
        skc->skc_obj_total = 0;
        skc->skc_obj_alloc = 0;
        skc->skc_obj_max = 0;
        skc->skc_obj_deadlock = 0;
        skc->skc_obj_emergency = 0;
        skc->skc_obj_emergency_max = 0;

        /*
         * Verify the requested alignment restriction is sane.
         */
        if (align) {
                VERIFY(ISP2(align));
                VERIFY3U(align, >=, SPL_KMEM_CACHE_ALIGN);
                VERIFY3U(align, <=, PAGE_SIZE);
                skc->skc_obj_align = align;
        }

        /*
         * When no specific type of slab is requested (kmem, vmem, or
         * linuxslab) then select a cache type based on the object size
         * and default tunables.
         */
        if (!(skc->skc_flags & (KMC_KMEM | KMC_VMEM | KMC_SLAB))) {

                /*
                 * Objects smaller than spl_kmem_cache_slab_limit can
                 * use the Linux slab for better space-efficiency.  By
                 * default this functionality is disabled until its
                 * performance characters are fully understood.
                 */
                if (spl_kmem_cache_slab_limit &&
                    size <= (size_t)spl_kmem_cache_slab_limit)
                        skc->skc_flags |= KMC_SLAB;

                /*
                 * Small objects, less than spl_kmem_cache_kmem_limit per
                 * object should use kmem because their slabs are small.
                 */
                else if (spl_obj_size(skc) <= spl_kmem_cache_kmem_limit)
                        skc->skc_flags |= KMC_KMEM;

                /*
                 * All other objects are considered large and are placed
                 * on vmem backed slabs.
                 */
                else
                        skc->skc_flags |= KMC_VMEM;
        }

        /*
         * Given the type of slab allocate the required resources.
         */
        if (skc->skc_flags & (KMC_KMEM | KMC_VMEM)) {
                rc = spl_slab_size(skc,
                    &skc->skc_slab_objs, &skc->skc_slab_size);
                if (rc)
                        SGOTO(out, rc);

                rc = spl_magazine_create(skc);
                if (rc)
                        SGOTO(out, rc);
        } else {
                skc->skc_linux_cache = kmem_cache_create(
                    skc->skc_name, size, align, 0, NULL);
                if (skc->skc_linux_cache == NULL)
                        SGOTO(out, rc = ENOMEM);

                kmem_cache_set_allocflags(skc, __GFP_COMP);
                skc->skc_flags |= KMC_NOMAGAZINE;
        }

        if (spl_kmem_cache_expire & KMC_EXPIRE_AGE)
                skc->skc_taskqid = taskq_dispatch_delay(spl_kmem_cache_taskq,
                    spl_cache_age, skc, TQ_SLEEP,
                    ddi_get_lbolt() + skc->skc_delay / 3 * HZ);

        down_write(&spl_kmem_cache_sem);
        list_add_tail(&skc->skc_list, &spl_kmem_cache_list);
        up_write(&spl_kmem_cache_sem);

        SRETURN(skc);
out:
        kmem_free(skc->skc_name, skc->skc_name_size);
        kmem_free(skc, sizeof(*skc));
        SRETURN(NULL);
}
EXPORT_SYMBOL(spl_kmem_cache_create);

/*
 * Register a move callback to for cache defragmentation.
 * XXX: Unimplemented but harmless to stub out for now.
 */
void
spl_kmem_cache_set_move(spl_kmem_cache_t *skc,
    kmem_cbrc_t (move)(void *, void *, size_t, void *))
{
        ASSERT(move != NULL);
}
EXPORT_SYMBOL(spl_kmem_cache_set_move);

/*
 * Destroy a cache and all objects associated with the cache.
 */
void
spl_kmem_cache_destroy(spl_kmem_cache_t *skc)
{
        DECLARE_WAIT_QUEUE_HEAD(wq);
        taskqid_t id;
        SENTRY;

        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT(skc->skc_flags & (KMC_KMEM | KMC_VMEM | KMC_SLAB));

        down_write(&spl_kmem_cache_sem);
        list_del_init(&skc->skc_list);
        up_write(&spl_kmem_cache_sem);

        /* Cancel any and wait for any pending delayed tasks */
        VERIFY(!test_and_set_bit(KMC_BIT_DESTROY, &skc->skc_flags));

        spin_lock(&skc->skc_lock);
        id = skc->skc_taskqid;
        spin_unlock(&skc->skc_lock);

        taskq_cancel_id(spl_kmem_cache_taskq, id);

        /* Wait until all current callers complete, this is mainly
         * to catch the case where a low memory situation triggers a
         * cache reaping action which races with this destroy. */
        wait_event(wq, atomic_read(&skc->skc_ref) == 0);

        if (skc->skc_flags & (KMC_KMEM | KMC_VMEM)) {
                spl_magazine_destroy(skc);
                spl_slab_reclaim(skc, 0, 1);
        } else {
                ASSERT(skc->skc_flags & KMC_SLAB);
                kmem_cache_destroy(skc->skc_linux_cache);
        }

        spin_lock(&skc->skc_lock);

        /* Validate there are no objects in use and free all the
         * spl_kmem_slab_t, spl_kmem_obj_t, and object buffers. */
        ASSERT3U(skc->skc_slab_alloc, ==, 0);
        ASSERT3U(skc->skc_obj_alloc, ==, 0);
        ASSERT3U(skc->skc_slab_total, ==, 0);
        ASSERT3U(skc->skc_obj_total, ==, 0);
        ASSERT3U(skc->skc_obj_emergency, ==, 0);
        ASSERT(list_empty(&skc->skc_complete_list));

        kmem_free(skc->skc_name, skc->skc_name_size);
        spin_unlock(&skc->skc_lock);

        kmem_free(skc, sizeof(*skc));

        SEXIT;
}
EXPORT_SYMBOL(spl_kmem_cache_destroy);

/*
 * Allocate an object from a slab attached to the cache.  This is used to
 * repopulate the per-cpu magazine caches in batches when they run low.
 */
static void *
spl_cache_obj(spl_kmem_cache_t *skc, spl_kmem_slab_t *sks)
{
        spl_kmem_obj_t *sko;

        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT(sks->sks_magic == SKS_MAGIC);
        ASSERT(spin_is_locked(&skc->skc_lock));

        sko = list_entry(sks->sks_free_list.next, spl_kmem_obj_t, sko_list);
        ASSERT(sko->sko_magic == SKO_MAGIC);
        ASSERT(sko->sko_addr != NULL);

        /* Remove from sks_free_list */
        list_del_init(&sko->sko_list);

        sks->sks_age = jiffies;
        sks->sks_ref++;
        skc->skc_obj_alloc++;

        /* Track max obj usage statistics */
        if (skc->skc_obj_alloc > skc->skc_obj_max)
                skc->skc_obj_max = skc->skc_obj_alloc;

        /* Track max slab usage statistics */
        if (sks->sks_ref == 1) {
                skc->skc_slab_alloc++;

                if (skc->skc_slab_alloc > skc->skc_slab_max)
                        skc->skc_slab_max = skc->skc_slab_alloc;
        }

        return sko->sko_addr;
}

/*
 * Generic slab allocation function to run by the global work queues.
 * It is responsible for allocating a new slab, linking it in to the list
 * of partial slabs, and then waking any waiters.
 */
static void
spl_cache_grow_work(void *data)
{
        spl_kmem_alloc_t *ska = (spl_kmem_alloc_t *)data;
        spl_kmem_cache_t *skc = ska->ska_cache;
        spl_kmem_slab_t *sks;

        sks = spl_slab_alloc(skc, ska->ska_flags | __GFP_NORETRY | KM_NODEBUG);
        spin_lock(&skc->skc_lock);
        if (sks) {
                skc->skc_slab_total++;
                skc->skc_obj_total += sks->sks_objs;
                list_add_tail(&sks->sks_list, &skc->skc_partial_list);
        }

        atomic_dec(&skc->skc_ref);
        clear_bit(KMC_BIT_GROWING, &skc->skc_flags);
        clear_bit(KMC_BIT_DEADLOCKED, &skc->skc_flags);
        wake_up_all(&skc->skc_waitq);
        spin_unlock(&skc->skc_lock);

        kfree(ska);
}

/*
 * Returns non-zero when a new slab should be available.
 */
static int
spl_cache_grow_wait(spl_kmem_cache_t *skc)
{
        return !test_bit(KMC_BIT_GROWING, &skc->skc_flags);
}

static int
spl_cache_reclaim_wait(void *word)
{
        schedule();
        return 0;
}

/*
 * No available objects on any slabs, create a new slab.  Note that this
 * functionality is disabled for KMC_SLAB caches which are backed by the
 * Linux slab.
 */
static int
spl_cache_grow(spl_kmem_cache_t *skc, int flags, void **obj)
{
        int remaining, rc;
        SENTRY;

        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT((skc->skc_flags & KMC_SLAB) == 0);
        might_sleep();
        *obj = NULL;

        /*
         * Before allocating a new slab wait for any reaping to complete and
         * then return so the local magazine can be rechecked for new objects.
         */
        if (test_bit(KMC_BIT_REAPING, &skc->skc_flags)) {
                rc = wait_on_bit(&skc->skc_flags, KMC_BIT_REAPING,
                    spl_cache_reclaim_wait, TASK_UNINTERRUPTIBLE);
                SRETURN(rc ? rc : -EAGAIN);
        }

        /*
         * This is handled by dispatching a work request to the global work
         * queue.  This allows us to asynchronously allocate a new slab while
         * retaining the ability to safely fall back to a smaller synchronous
         * allocations to ensure forward progress is always maintained.
         */
        if (test_and_set_bit(KMC_BIT_GROWING, &skc->skc_flags) == 0) {
                spl_kmem_alloc_t *ska;

                ska = kmalloc(sizeof(*ska), flags);
                if (ska == NULL) {
                        clear_bit(KMC_BIT_GROWING, &skc->skc_flags);
                        wake_up_all(&skc->skc_waitq);
                        SRETURN(-ENOMEM);
                }

                atomic_inc(&skc->skc_ref);
                ska->ska_cache = skc;
                ska->ska_flags = flags & ~__GFP_FS;
                taskq_init_ent(&ska->ska_tqe);
                taskq_dispatch_ent(spl_kmem_cache_taskq,
                    spl_cache_grow_work, ska, 0, &ska->ska_tqe);
        }

        /*
         * The goal here is to only detect the rare case where a virtual slab
         * allocation has deadlocked.  We must be careful to minimize the use
         * of emergency objects which are more expensive to track.  Therefore,
         * we set a very long timeout for the asynchronous allocation and if
         * the timeout is reached the cache is flagged as deadlocked.  From
         * this point only new emergency objects will be allocated until the
         * asynchronous allocation completes and clears the deadlocked flag.
         */
        if (test_bit(KMC_BIT_DEADLOCKED, &skc->skc_flags)) {
                rc = spl_emergency_alloc(skc, flags, obj);
        } else {
                remaining = wait_event_timeout(skc->skc_waitq,
                                               spl_cache_grow_wait(skc), HZ);

                if (!remaining && test_bit(KMC_BIT_VMEM, &skc->skc_flags)) {
                        spin_lock(&skc->skc_lock);
                        if (test_bit(KMC_BIT_GROWING, &skc->skc_flags)) {
                                set_bit(KMC_BIT_DEADLOCKED, &skc->skc_flags);
                                skc->skc_obj_deadlock++;
                        }
                        spin_unlock(&skc->skc_lock);
                }

                rc = -ENOMEM;
        }

        SRETURN(rc);
}

/*
 * Refill a per-cpu magazine with objects from the slabs for this cache.
 * Ideally the magazine can be repopulated using existing objects which have
 * been released, however if we are unable to locate enough free objects new
 * slabs of objects will be created.  On success NULL is returned, otherwise
 * the address of a single emergency object is returned for use by the caller.
 */
static void *
spl_cache_refill(spl_kmem_cache_t *skc, spl_kmem_magazine_t *skm, int flags)
{
        spl_kmem_slab_t *sks;
        int count = 0, rc, refill;
        void *obj = NULL;
        SENTRY;

        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT(skm->skm_magic == SKM_MAGIC);

        refill = MIN(skm->skm_refill, skm->skm_size - skm->skm_avail);
        spin_lock(&skc->skc_lock);

        while (refill > 0) {
                /* No slabs available we may need to grow the cache */
                if (list_empty(&skc->skc_partial_list)) {
                        spin_unlock(&skc->skc_lock);

                        local_irq_enable();
                        rc = spl_cache_grow(skc, flags, &obj);
                        local_irq_disable();

                        /* Emergency object for immediate use by caller */
                        if (rc == 0 && obj != NULL)
                                SRETURN(obj);

                        if (rc)
                                SGOTO(out, rc);

                        /* Rescheduled to different CPU skm is not local */
                        if (skm != skc->skc_mag[smp_processor_id()])
                                SGOTO(out, rc);

                        /* Potentially rescheduled to the same CPU but
                         * allocations may have occurred from this CPU while
                         * we were sleeping so recalculate max refill. */
                        refill = MIN(refill, skm->skm_size - skm->skm_avail);

                        spin_lock(&skc->skc_lock);
                        continue;
                }

                /* Grab the next available slab */
                sks = list_entry((&skc->skc_partial_list)->next,
                                 spl_kmem_slab_t, sks_list);
                ASSERT(sks->sks_magic == SKS_MAGIC);
                ASSERT(sks->sks_ref < sks->sks_objs);
                ASSERT(!list_empty(&sks->sks_free_list));

                /* Consume as many objects as needed to refill the requested
                 * cache.  We must also be careful not to overfill it. */
                while (sks->sks_ref < sks->sks_objs && refill-- > 0 && ++count) {
                        ASSERT(skm->skm_avail < skm->skm_size);
                        ASSERT(count < skm->skm_size);
                        skm->skm_objs[skm->skm_avail++]=spl_cache_obj(skc,sks);
                }

                /* Move slab to skc_complete_list when full */
                if (sks->sks_ref == sks->sks_objs) {
                        list_del(&sks->sks_list);
                        list_add(&sks->sks_list, &skc->skc_complete_list);
                }
        }

        spin_unlock(&skc->skc_lock);
out:
        SRETURN(NULL);
}

/*
 * Release an object back to the slab from which it came.
 */
static void
spl_cache_shrink(spl_kmem_cache_t *skc, void *obj)
{
        spl_kmem_slab_t *sks = NULL;
        spl_kmem_obj_t *sko = NULL;
        SENTRY;

        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT(spin_is_locked(&skc->skc_lock));

        sko = spl_sko_from_obj(skc, obj);
        ASSERT(sko->sko_magic == SKO_MAGIC);
        sks = sko->sko_slab;
        ASSERT(sks->sks_magic == SKS_MAGIC);
        ASSERT(sks->sks_cache == skc);
        list_add(&sko->sko_list, &sks->sks_free_list);

        sks->sks_age = jiffies;
        sks->sks_ref--;
        skc->skc_obj_alloc--;

        /* Move slab to skc_partial_list when no longer full.  Slabs
         * are added to the head to keep the partial list is quasi-full
         * sorted order.  Fuller at the head, emptier at the tail. */
        if (sks->sks_ref == (sks->sks_objs - 1)) {
                list_del(&sks->sks_list);
                list_add(&sks->sks_list, &skc->skc_partial_list);
        }

        /* Move empty slabs to the end of the partial list so
         * they can be easily found and freed during reclamation. */
        if (sks->sks_ref == 0) {
                list_del(&sks->sks_list);
                list_add_tail(&sks->sks_list, &skc->skc_partial_list);
                skc->skc_slab_alloc--;
        }

        SEXIT;
}

/*
 * Allocate an object from the per-cpu magazine, or if the magazine
 * is empty directly allocate from a slab and repopulate the magazine.
 */
void *
spl_kmem_cache_alloc(spl_kmem_cache_t *skc, int flags)
{
        spl_kmem_magazine_t *skm;
        void *obj = NULL;
        SENTRY;

        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT(!test_bit(KMC_BIT_DESTROY, &skc->skc_flags));
        ASSERT(flags & KM_SLEEP);

        atomic_inc(&skc->skc_ref);

        /*
         * Allocate directly from a Linux slab.  All optimizations are left
         * to the underlying cache we only need to guarantee that KM_SLEEP
         * callers will never fail.
         */
        if (skc->skc_flags & KMC_SLAB) {
                struct kmem_cache *slc = skc->skc_linux_cache;

                do {
                        obj = kmem_cache_alloc(slc, flags | __GFP_COMP);
                        if (obj && skc->skc_ctor)
                                skc->skc_ctor(obj, skc->skc_private, flags);

                } while ((obj == NULL) && !(flags & KM_NOSLEEP));

                atomic_dec(&skc->skc_ref);
                SRETURN(obj);
        }

        local_irq_disable();

restart:
        /* Safe to update per-cpu structure without lock, but
         * in the restart case we must be careful to reacquire
         * the local magazine since this may have changed
         * when we need to grow the cache. */
        skm = skc->skc_mag[smp_processor_id()];
        ASSERTF(skm->skm_magic == SKM_MAGIC, "%x != %x: %s/%p/%p %x/%x/%x\n",
                skm->skm_magic, SKM_MAGIC, skc->skc_name, skc, skm,
                skm->skm_size, skm->skm_refill, skm->skm_avail);

        if (likely(skm->skm_avail)) {
                /* Object available in CPU cache, use it */
                obj = skm->skm_objs[--skm->skm_avail];
                skm->skm_age = jiffies;
        } else {
                obj = spl_cache_refill(skc, skm, flags);
                if (obj == NULL)
                        SGOTO(restart, obj = NULL);
        }

        local_irq_enable();
        ASSERT(obj);
        ASSERT(IS_P2ALIGNED(obj, skc->skc_obj_align));

        /* Pre-emptively migrate object to CPU L1 cache */
        prefetchw(obj);
        atomic_dec(&skc->skc_ref);

        SRETURN(obj);
}
EXPORT_SYMBOL(spl_kmem_cache_alloc);

/*
 * Free an object back to the local per-cpu magazine, there is no
 * guarantee that this is the same magazine the object was originally
 * allocated from.  We may need to flush entire from the magazine
 * back to the slabs to make space.
 */
void
spl_kmem_cache_free(spl_kmem_cache_t *skc, void *obj)
{
        spl_kmem_magazine_t *skm;
        unsigned long flags;
        SENTRY;

        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT(!test_bit(KMC_BIT_DESTROY, &skc->skc_flags));
        atomic_inc(&skc->skc_ref);

        /*
         * Free the object from the Linux underlying Linux slab.
         */
        if (skc->skc_flags & KMC_SLAB) {
                if (skc->skc_dtor)
                        skc->skc_dtor(obj, skc->skc_private);

                kmem_cache_free(skc->skc_linux_cache, obj);
                goto out;
        }

        /*
         * Only virtual slabs may have emergency objects and these objects
         * are guaranteed to have physical addresses.  They must be removed
         * from the tree of emergency objects and the freed.
         */
        if ((skc->skc_flags & KMC_VMEM) && !kmem_virt(obj))
                SGOTO(out, spl_emergency_free(skc, obj));

        local_irq_save(flags);

        /* Safe to update per-cpu structure without lock, but
         * no remote memory allocation tracking is being performed
         * it is entirely possible to allocate an object from one
         * CPU cache and return it to another. */
        skm = skc->skc_mag[smp_processor_id()];
        ASSERT(skm->skm_magic == SKM_MAGIC);

        /* Per-CPU cache full, flush it to make space */
        if (unlikely(skm->skm_avail >= skm->skm_size))
                spl_cache_flush(skc, skm, skm->skm_refill);

        /* Available space in cache, use it */
        skm->skm_objs[skm->skm_avail++] = obj;

        local_irq_restore(flags);
out:
        atomic_dec(&skc->skc_ref);

        SEXIT;
}
EXPORT_SYMBOL(spl_kmem_cache_free);

/*
 * The generic shrinker function for all caches.  Under Linux a shrinker
 * may not be tightly coupled with a slab cache.  In fact Linux always
 * systematically tries calling all registered shrinker callbacks which
 * report that they contain unused objects.  Because of this we only
 * register one shrinker function in the shim layer for all slab caches.
 * We always attempt to shrink all caches when this generic shrinker
 * is called.  The shrinker should return the number of free objects
 * in the cache when called with nr_to_scan == 0 but not attempt to
 * free any objects.  When nr_to_scan > 0 it is a request that nr_to_scan
 * objects should be freed, which differs from Solaris semantics.
 * Solaris semantics are to free all available objects which may (and
 * probably will) be more objects than the requested nr_to_scan.
 */
static int
__spl_kmem_cache_generic_shrinker(struct shrinker *shrink,
    struct shrink_control *sc)
{
        spl_kmem_cache_t *skc;
        int unused = 0;

        down_read(&spl_kmem_cache_sem);
        list_for_each_entry(skc, &spl_kmem_cache_list, skc_list) {
                if (sc->nr_to_scan)
                        spl_kmem_cache_reap_now(skc,
                           MAX(sc->nr_to_scan >> fls64(skc->skc_slab_objs), 1));

                /*
                 * Presume everything alloc'ed in reclaimable, this ensures
                 * we are called again with nr_to_scan > 0 so can try and
                 * reclaim.  The exact number is not important either so
                 * we forgo taking this already highly contented lock.
                 */
                unused += skc->skc_obj_alloc;
        }
        up_read(&spl_kmem_cache_sem);

        /*
         * After performing reclaim always return -1 to indicate we cannot
         * perform additional reclaim.  This prevents shrink_slabs() from
         * repeatedly invoking this generic shrinker and potentially spinning.
         */
        if (sc->nr_to_scan)
                return -1;

        return unused;
}

SPL_SHRINKER_CALLBACK_WRAPPER(spl_kmem_cache_generic_shrinker);

/*
 * Call the registered reclaim function for a cache.  Depending on how
 * many and which objects are released it may simply repopulate the
 * local magazine which will then need to age-out.  Objects which cannot
 * fit in the magazine we will be released back to their slabs which will
 * also need to age out before being release.  This is all just best
 * effort and we do not want to thrash creating and destroying slabs.
 */
void
spl_kmem_cache_reap_now(spl_kmem_cache_t *skc, int count)
{
        SENTRY;

        ASSERT(skc->skc_magic == SKC_MAGIC);
        ASSERT(!test_bit(KMC_BIT_DESTROY, &skc->skc_flags));

        atomic_inc(&skc->skc_ref);

        /*
         * Execute the registered reclaim callback if it exists.  The
         * per-cpu caches will be drained when is set KMC_EXPIRE_MEM.
         */
        if (skc->skc_flags & KMC_SLAB) {
                if (skc->skc_reclaim)
                        skc->skc_reclaim(skc->skc_private);

                if (spl_kmem_cache_expire & KMC_EXPIRE_MEM)
                        kmem_cache_shrink(skc->skc_linux_cache);

                SGOTO(out, 0);
        }

        /*
         * Prevent concurrent cache reaping when contended.
         */
        if (test_and_set_bit(KMC_BIT_REAPING, &skc->skc_flags))
                SGOTO(out, 0);

        /*
         * When a reclaim function is available it may be invoked repeatedly
         * until at least a single slab can be freed.  This ensures that we
         * do free memory back to the system.  This helps minimize the chance
         * of an OOM event when the bulk of memory is used by the slab.
         *
         * When free slabs are already available the reclaim callback will be
         * skipped.  Additionally, if no forward progress is detected despite
         * a reclaim function the cache will be skipped to avoid deadlock.
         *
         * Longer term this would be the correct place to add the code which
         * repacks the slabs in order minimize fragmentation.
         */
        if (skc->skc_reclaim) {
                uint64_t objects = UINT64_MAX;
                int do_reclaim;

                do {
                        spin_lock(&skc->skc_lock);
                        do_reclaim =
                            (skc->skc_slab_total > 0) &&
                            ((skc->skc_slab_total - skc->skc_slab_alloc) == 0) &&
                            (skc->skc_obj_alloc < objects);

                        objects = skc->skc_obj_alloc;
                        spin_unlock(&skc->skc_lock);

                        if (do_reclaim)
                                skc->skc_reclaim(skc->skc_private);

                } while (do_reclaim);
        }

        /* Reclaim from the magazine then the slabs ignoring age and delay. */
        if (spl_kmem_cache_expire & KMC_EXPIRE_MEM) {
                spl_kmem_magazine_t *skm;
                unsigned long irq_flags;

                local_irq_save(irq_flags);
                skm = skc->skc_mag[smp_processor_id()];
                spl_cache_flush(skc, skm, skm->skm_avail);
                local_irq_restore(irq_flags);
        }

        spl_slab_reclaim(skc, count, 1);
        clear_bit(KMC_BIT_REAPING, &skc->skc_flags);
        smp_mb__after_clear_bit();
        wake_up_bit(&skc->skc_flags, KMC_BIT_REAPING);
out:
        atomic_dec(&skc->skc_ref);

        SEXIT;
}
EXPORT_SYMBOL(spl_kmem_cache_reap_now);

/*
 * Reap all free slabs from all registered caches.
 */
void
spl_kmem_reap(void)
{
        struct shrink_control sc;

        sc.nr_to_scan = KMC_REAP_CHUNK;
        sc.gfp_mask = GFP_KERNEL;

        __spl_kmem_cache_generic_shrinker(NULL, &sc);
}
EXPORT_SYMBOL(spl_kmem_reap);

#if defined(DEBUG_KMEM) && defined(DEBUG_KMEM_TRACKING)
static char *
spl_sprintf_addr(kmem_debug_t *kd, char *str, int len, int min)
{
        int size = ((len - 1) < kd->kd_size) ? (len - 1) : kd->kd_size;
        int i, flag = 1;

        ASSERT(str != NULL && len >= 17);
        memset(str, 0, len);

        /* Check for a fully printable string, and while we are at
         * it place the printable characters in the passed buffer. */
        for (i = 0; i < size; i++) {
                str[i] = ((char *)(kd->kd_addr))[i];
                if (isprint(str[i])) {
                        continue;
                } else {
                        /* Minimum number of printable characters found
                         * to make it worthwhile to print this as ascii. */
                        if (i > min)
                                break;

                        flag = 0;
                        break;
                }
        }

        if (!flag) {
                sprintf(str, "%02x%02x%02x%02x%02x%02x%02x%02x",
                        *((uint8_t *)kd->kd_addr),
                        *((uint8_t *)kd->kd_addr + 2),
                        *((uint8_t *)kd->kd_addr + 4),
                        *((uint8_t *)kd->kd_addr + 6),
                        *((uint8_t *)kd->kd_addr + 8),
                        *((uint8_t *)kd->kd_addr + 10),
                        *((uint8_t *)kd->kd_addr + 12),
                        *((uint8_t *)kd->kd_addr + 14));
        }

        return str;
}

static int
spl_kmem_init_tracking(struct list_head *list, spinlock_t *lock, int size)
{
        int i;
        SENTRY;

        spin_lock_init(lock);
        INIT_LIST_HEAD(list);

        for (i = 0; i < size; i++)
                INIT_HLIST_HEAD(&kmem_table[i]);

        SRETURN(0);
}

static void
spl_kmem_fini_tracking(struct list_head *list, spinlock_t *lock)
{
        unsigned long flags;
        kmem_debug_t *kd;
        char str[17];
        SENTRY;

        spin_lock_irqsave(lock, flags);
        if (!list_empty(list))
                printk(KERN_WARNING "%-16s %-5s %-16s %s:%s\n", "address",
                       "size", "data", "func", "line");

        list_for_each_entry(kd, list, kd_list)
                printk(KERN_WARNING "%p %-5d %-16s %s:%d\n", kd->kd_addr,
                       (int)kd->kd_size, spl_sprintf_addr(kd, str, 17, 8),
                       kd->kd_func, kd->kd_line);

        spin_unlock_irqrestore(lock, flags);
        SEXIT;
}
#else /* DEBUG_KMEM && DEBUG_KMEM_TRACKING */
#define spl_kmem_init_tracking(list, lock, size)
#define spl_kmem_fini_tracking(list, lock)
#endif /* DEBUG_KMEM && DEBUG_KMEM_TRACKING */

static void
spl_kmem_init_globals(void)
{
        struct zone *zone;

        /* For now all zones are includes, it may be wise to restrict
         * this to normal and highmem zones if we see problems. */
        for_each_zone(zone) {

                if (!populated_zone(zone))
                        continue;

                minfree += min_wmark_pages(zone);
                desfree += low_wmark_pages(zone);
                lotsfree += high_wmark_pages(zone);
        }

        /* Solaris default values */
        swapfs_minfree = MAX(2*1024*1024 >> PAGE_SHIFT, physmem >> 3);
        swapfs_reserve = MIN(4*1024*1024 >> PAGE_SHIFT, physmem >> 4);
}

/*
 * Called at module init when it is safe to use spl_kallsyms_lookup_name()
 */
int
spl_kmem_init_kallsyms_lookup(void)
{
#ifndef HAVE_GET_VMALLOC_INFO
        get_vmalloc_info_fn = (get_vmalloc_info_t)
                spl_kallsyms_lookup_name("get_vmalloc_info");
        if (!get_vmalloc_info_fn) {
                printk(KERN_ERR "Error: Unknown symbol get_vmalloc_info\n");
                return -EFAULT;
        }
#endif /* HAVE_GET_VMALLOC_INFO */

#ifdef HAVE_PGDAT_HELPERS
# ifndef HAVE_FIRST_ONLINE_PGDAT
        first_online_pgdat_fn = (first_online_pgdat_t)
                spl_kallsyms_lookup_name("first_online_pgdat");
        if (!first_online_pgdat_fn) {
                printk(KERN_ERR "Error: Unknown symbol first_online_pgdat\n");
                return -EFAULT;
        }
# endif /* HAVE_FIRST_ONLINE_PGDAT */

# ifndef HAVE_NEXT_ONLINE_PGDAT
        next_online_pgdat_fn = (next_online_pgdat_t)
                spl_kallsyms_lookup_name("next_online_pgdat");
        if (!next_online_pgdat_fn) {
                printk(KERN_ERR "Error: Unknown symbol next_online_pgdat\n");
                return -EFAULT;
        }
# endif /* HAVE_NEXT_ONLINE_PGDAT */

# ifndef HAVE_NEXT_ZONE
        next_zone_fn = (next_zone_t)
                spl_kallsyms_lookup_name("next_zone");
        if (!next_zone_fn) {
                printk(KERN_ERR "Error: Unknown symbol next_zone\n");
                return -EFAULT;
        }
# endif /* HAVE_NEXT_ZONE */

#else /* HAVE_PGDAT_HELPERS */

# ifndef HAVE_PGDAT_LIST
        pgdat_list_addr = *(struct pglist_data **)
                spl_kallsyms_lookup_name("pgdat_list");
        if (!pgdat_list_addr) {
                printk(KERN_ERR "Error: Unknown symbol pgdat_list\n");
                return -EFAULT;
        }
# endif /* HAVE_PGDAT_LIST */
#endif /* HAVE_PGDAT_HELPERS */

#if defined(NEED_GET_ZONE_COUNTS) && !defined(HAVE_GET_ZONE_COUNTS)
        get_zone_counts_fn = (get_zone_counts_t)
                spl_kallsyms_lookup_name("get_zone_counts");
        if (!get_zone_counts_fn) {
                printk(KERN_ERR "Error: Unknown symbol get_zone_counts\n");
                return -EFAULT;
        }
#endif  /* NEED_GET_ZONE_COUNTS && !HAVE_GET_ZONE_COUNTS */

        /*
         * It is now safe to initialize the global tunings which rely on
         * the use of the for_each_zone() macro.  This macro in turns
         * depends on the *_pgdat symbols which are now available.
         */
        spl_kmem_init_globals();

#ifndef HAVE_SHRINK_DCACHE_MEMORY
        /* When shrink_dcache_memory_fn == NULL support is disabled */
        shrink_dcache_memory_fn = (shrink_dcache_memory_t)
                spl_kallsyms_lookup_name("shrink_dcache_memory");
#endif /* HAVE_SHRINK_DCACHE_MEMORY */

#ifndef HAVE_SHRINK_ICACHE_MEMORY
        /* When shrink_icache_memory_fn == NULL support is disabled */
        shrink_icache_memory_fn = (shrink_icache_memory_t)
                spl_kallsyms_lookup_name("shrink_icache_memory");
#endif /* HAVE_SHRINK_ICACHE_MEMORY */

        return 0;
}

int
spl_kmem_init(void)
{
        int rc = 0;
        SENTRY;

#ifdef DEBUG_KMEM
        kmem_alloc_used_set(0);
        vmem_alloc_used_set(0);

        spl_kmem_init_tracking(&kmem_list, &kmem_lock, KMEM_TABLE_SIZE);
        spl_kmem_init_tracking(&vmem_list, &vmem_lock, VMEM_TABLE_SIZE);
#endif

        init_rwsem(&spl_kmem_cache_sem);
        INIT_LIST_HEAD(&spl_kmem_cache_list);
        spl_kmem_cache_taskq = taskq_create("spl_kmem_cache",
            1, maxclsyspri, 1, 32, TASKQ_PREPOPULATE);

        spl_register_shrinker(&spl_kmem_cache_shrinker);

        SRETURN(rc);
}

void
spl_kmem_fini(void)
{
        SENTRY;

        spl_unregister_shrinker(&spl_kmem_cache_shrinker);
        taskq_destroy(spl_kmem_cache_taskq);

#ifdef DEBUG_KMEM
        /* Display all unreclaimed memory addresses, including the
         * allocation size and the first few bytes of what's located
         * at that address to aid in debugging.  Performance is not
         * a serious concern here since it is module unload time. */
        if (kmem_alloc_used_read() != 0)
                SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING,
                    "kmem leaked %ld/%ld bytes\n",
                    kmem_alloc_used_read(), kmem_alloc_max);


        if (vmem_alloc_used_read() != 0)
                SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING,
                    "vmem leaked %ld/%ld bytes\n",
                    vmem_alloc_used_read(), vmem_alloc_max);

        spl_kmem_fini_tracking(&kmem_list, &kmem_lock);
        spl_kmem_fini_tracking(&vmem_list, &vmem_lock);
#endif /* DEBUG_KMEM */

        SEXIT;
}