bdi: Fix use after free bug in debugfs_remove()

[mirror_ubuntu-bionic-kernel.git] / mm / slab_common.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Slab allocator functions that are independent of the allocator strategy
 *
 * (C) 2012 Christoph Lameter <cl@linux.com>
 */
#include <linux/slab.h>

#include <linux/mm.h>
#include <linux/poison.h>
#include <linux/interrupt.h>
#include <linux/memory.h>
#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/uaccess.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/page.h>
#include <linux/memcontrol.h>

#define CREATE_TRACE_POINTS
#include <trace/events/kmem.h>

#include "slab.h"

enum slab_state slab_state;
LIST_HEAD(slab_caches);
DEFINE_MUTEX(slab_mutex);
struct kmem_cache *kmem_cache;

static LIST_HEAD(slab_caches_to_rcu_destroy);
static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work);
static DECLARE_WORK(slab_caches_to_rcu_destroy_work,
                    slab_caches_to_rcu_destroy_workfn);

/*
 * Set of flags that will prevent slab merging
 */
#define SLAB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
                SLAB_TRACE | SLAB_TYPESAFE_BY_RCU | SLAB_NOLEAKTRACE | \
                SLAB_FAILSLAB | SLAB_KASAN)

#define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | \
                         SLAB_ACCOUNT)

/*
 * Merge control. If this is set then no merging of slab caches will occur.
 */
static bool slab_nomerge = !IS_ENABLED(CONFIG_SLAB_MERGE_DEFAULT);

static int __init setup_slab_nomerge(char *str)
{
        slab_nomerge = true;
        return 1;
}

#ifdef CONFIG_SLUB
__setup_param("slub_nomerge", slub_nomerge, setup_slab_nomerge, 0);
#endif

__setup("slab_nomerge", setup_slab_nomerge);

/*
 * Determine the size of a slab object
 */
unsigned int kmem_cache_size(struct kmem_cache *s)
{
        return s->object_size;
}
EXPORT_SYMBOL(kmem_cache_size);

#ifdef CONFIG_DEBUG_VM
static int kmem_cache_sanity_check(const char *name, size_t size)
{
        struct kmem_cache *s = NULL;

        if (!name || in_interrupt() || size < sizeof(void *) ||
                size > KMALLOC_MAX_SIZE) {
                pr_err("kmem_cache_create(%s) integrity check failed\n", name);
                return -EINVAL;
        }

        list_for_each_entry(s, &slab_caches, list) {
                char tmp;
                int res;

                /*
                 * This happens when the module gets unloaded and doesn't
                 * destroy its slab cache and no-one else reuses the vmalloc
                 * area of the module.  Print a warning.
                 */
                res = probe_kernel_address(s->name, tmp);
                if (res) {
                        pr_err("Slab cache with size %d has lost its name\n",
                               s->object_size);
                        continue;
                }
        }

        WARN_ON(strchr(name, ' '));     /* It confuses parsers */
        return 0;
}
#else
static inline int kmem_cache_sanity_check(const char *name, size_t size)
{
        return 0;
}
#endif

void __kmem_cache_free_bulk(struct kmem_cache *s, size_t nr, void **p)
{
        size_t i;

        for (i = 0; i < nr; i++) {
                if (s)
                        kmem_cache_free(s, p[i]);
                else
                        kfree(p[i]);
        }
}

int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr,
                                                                void **p)
{
        size_t i;

        for (i = 0; i < nr; i++) {
                void *x = p[i] = kmem_cache_alloc(s, flags);
                if (!x) {
                        __kmem_cache_free_bulk(s, i, p);
                        return 0;
                }
        }
        return i;
}

#if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)

LIST_HEAD(slab_root_caches);

void slab_init_memcg_params(struct kmem_cache *s)
{
        s->memcg_params.root_cache = NULL;
        RCU_INIT_POINTER(s->memcg_params.memcg_caches, NULL);
        INIT_LIST_HEAD(&s->memcg_params.children);
}

static int init_memcg_params(struct kmem_cache *s,
                struct mem_cgroup *memcg, struct kmem_cache *root_cache)
{
        struct memcg_cache_array *arr;

        if (root_cache) {
                s->memcg_params.root_cache = root_cache;
                s->memcg_params.memcg = memcg;
                INIT_LIST_HEAD(&s->memcg_params.children_node);
                INIT_LIST_HEAD(&s->memcg_params.kmem_caches_node);
                return 0;
        }

        slab_init_memcg_params(s);

        if (!memcg_nr_cache_ids)
                return 0;

        arr = kvzalloc(sizeof(struct memcg_cache_array) +
                       memcg_nr_cache_ids * sizeof(void *),
                       GFP_KERNEL);
        if (!arr)
                return -ENOMEM;

        RCU_INIT_POINTER(s->memcg_params.memcg_caches, arr);
        return 0;
}

static void destroy_memcg_params(struct kmem_cache *s)
{
        if (is_root_cache(s))
                kvfree(rcu_access_pointer(s->memcg_params.memcg_caches));
}

static void free_memcg_params(struct rcu_head *rcu)
{
        struct memcg_cache_array *old;

        old = container_of(rcu, struct memcg_cache_array, rcu);
        kvfree(old);
}

static int update_memcg_params(struct kmem_cache *s, int new_array_size)
{
        struct memcg_cache_array *old, *new;

        new = kvzalloc(sizeof(struct memcg_cache_array) +
                       new_array_size * sizeof(void *), GFP_KERNEL);
        if (!new)
                return -ENOMEM;

        old = rcu_dereference_protected(s->memcg_params.memcg_caches,
                                        lockdep_is_held(&slab_mutex));
        if (old)
                memcpy(new->entries, old->entries,
                       memcg_nr_cache_ids * sizeof(void *));

        rcu_assign_pointer(s->memcg_params.memcg_caches, new);
        if (old)
                call_rcu(&old->rcu, free_memcg_params);
        return 0;
}

int memcg_update_all_caches(int num_memcgs)
{
        struct kmem_cache *s;
        int ret = 0;

        mutex_lock(&slab_mutex);
        list_for_each_entry(s, &slab_root_caches, root_caches_node) {
                ret = update_memcg_params(s, num_memcgs);
                /*
                 * Instead of freeing the memory, we'll just leave the caches
                 * up to this point in an updated state.
                 */
                if (ret)
                        break;
        }
        mutex_unlock(&slab_mutex);
        return ret;
}

void memcg_link_cache(struct kmem_cache *s)
{
        if (is_root_cache(s)) {
                list_add(&s->root_caches_node, &slab_root_caches);
        } else {
                list_add(&s->memcg_params.children_node,
                         &s->memcg_params.root_cache->memcg_params.children);
                list_add(&s->memcg_params.kmem_caches_node,
                         &s->memcg_params.memcg->kmem_caches);
        }
}

static void memcg_unlink_cache(struct kmem_cache *s)
{
        if (is_root_cache(s)) {
                list_del(&s->root_caches_node);
        } else {
                list_del(&s->memcg_params.children_node);
                list_del(&s->memcg_params.kmem_caches_node);
        }
}
#else
static inline int init_memcg_params(struct kmem_cache *s,
                struct mem_cgroup *memcg, struct kmem_cache *root_cache)
{
        return 0;
}

static inline void destroy_memcg_params(struct kmem_cache *s)
{
}

static inline void memcg_unlink_cache(struct kmem_cache *s)
{
}
#endif /* CONFIG_MEMCG && !CONFIG_SLOB */

/*
 * Find a mergeable slab cache
 */
int slab_unmergeable(struct kmem_cache *s)
{
        if (slab_nomerge || (s->flags & SLAB_NEVER_MERGE))
                return 1;

        if (!is_root_cache(s))
                return 1;

        if (s->ctor)
                return 1;

        /*
         * We may have set a slab to be unmergeable during bootstrap.
         */
        if (s->refcount < 0)
                return 1;

        return 0;
}

struct kmem_cache *find_mergeable(size_t size, size_t align,
                slab_flags_t flags, const char *name, void (*ctor)(void *))
{
        struct kmem_cache *s;

        if (slab_nomerge)
                return NULL;

        if (ctor)
                return NULL;

        size = ALIGN(size, sizeof(void *));
        align = calculate_alignment(flags, align, size);
        size = ALIGN(size, align);
        flags = kmem_cache_flags(size, flags, name, NULL);

        if (flags & SLAB_NEVER_MERGE)
                return NULL;

        list_for_each_entry_reverse(s, &slab_root_caches, root_caches_node) {
                if (slab_unmergeable(s))
                        continue;

                if (size > s->size)
                        continue;

                if ((flags & SLAB_MERGE_SAME) != (s->flags & SLAB_MERGE_SAME))
                        continue;
                /*
                 * Check if alignment is compatible.
                 * Courtesy of Adrian Drzewiecki
                 */
                if ((s->size & ~(align - 1)) != s->size)
                        continue;

                if (s->size - size >= sizeof(void *))
                        continue;

                if (IS_ENABLED(CONFIG_SLAB) && align &&
                        (align > s->align || s->align % align))
                        continue;

                return s;
        }
        return NULL;
}

/*
 * Figure out what the alignment of the objects will be given a set of
 * flags, a user specified alignment and the size of the objects.
 */
unsigned long calculate_alignment(slab_flags_t flags,
                unsigned long align, unsigned long size)
{
        /*
         * If the user wants hardware cache aligned objects then follow that
         * suggestion if the object is sufficiently large.
         *
         * The hardware cache alignment cannot override the specified
         * alignment though. If that is greater then use it.
         */
        if (flags & SLAB_HWCACHE_ALIGN) {
                unsigned long ralign = cache_line_size();
                while (size <= ralign / 2)
                        ralign /= 2;
                align = max(align, ralign);
        }

        if (align < ARCH_SLAB_MINALIGN)
                align = ARCH_SLAB_MINALIGN;

        return ALIGN(align, sizeof(void *));
}

static struct kmem_cache *create_cache(const char *name,
                size_t object_size, size_t size, size_t align,
                slab_flags_t flags, void (*ctor)(void *),
                struct mem_cgroup *memcg, struct kmem_cache *root_cache)
{
        struct kmem_cache *s;
        int err;

        err = -ENOMEM;
        s = kmem_cache_zalloc(kmem_cache, GFP_KERNEL);
        if (!s)
                goto out;

        s->name = name;
        s->object_size = object_size;
        s->size = size;
        s->align = align;
        s->ctor = ctor;

        err = init_memcg_params(s, memcg, root_cache);
        if (err)
                goto out_free_cache;

        err = __kmem_cache_create(s, flags);
        if (err)
                goto out_free_cache;

        s->refcount = 1;
        list_add(&s->list, &slab_caches);
        memcg_link_cache(s);
out:
        if (err)
                return ERR_PTR(err);
        return s;

out_free_cache:
        destroy_memcg_params(s);
        kmem_cache_free(kmem_cache, s);
        goto out;
}

/*
 * kmem_cache_create - Create a cache.
 * @name: A string which is used in /proc/slabinfo to identify this cache.
 * @size: The size of objects to be created in this cache.
 * @align: The required alignment for the objects.
 * @flags: SLAB flags
 * @ctor: A constructor for the objects.
 *
 * Returns a ptr to the cache on success, NULL on failure.
 * Cannot be called within a interrupt, but can be interrupted.
 * The @ctor is run when new pages are allocated by the cache.
 *
 * The flags are
 *
 * %SLAB_POISON - Poison the slab with a known test pattern (a5a5a5a5)
 * to catch references to uninitialised memory.
 *
 * %SLAB_RED_ZONE - Insert `Red' zones around the allocated memory to check
 * for buffer overruns.
 *
 * %SLAB_HWCACHE_ALIGN - Align the objects in this cache to a hardware
 * cacheline.  This can be beneficial if you're counting cycles as closely
 * as davem.
 */
struct kmem_cache *
kmem_cache_create(const char *name, size_t size, size_t align,
                  slab_flags_t flags, void (*ctor)(void *))
{
        struct kmem_cache *s = NULL;
        const char *cache_name;
        int err;

        get_online_cpus();
        get_online_mems();
        memcg_get_cache_ids();

        mutex_lock(&slab_mutex);

        err = kmem_cache_sanity_check(name, size);
        if (err) {
                goto out_unlock;
        }

        /* Refuse requests with allocator specific flags */
        if (flags & ~SLAB_FLAGS_PERMITTED) {
                err = -EINVAL;
                goto out_unlock;
        }

        /*
         * Some allocators will constraint the set of valid flags to a subset
         * of all flags. We expect them to define CACHE_CREATE_MASK in this
         * case, and we'll just provide them with a sanitized version of the
         * passed flags.
         */
        flags &= CACHE_CREATE_MASK;

        s = __kmem_cache_alias(name, size, align, flags, ctor);
        if (s)
                goto out_unlock;

        cache_name = kstrdup_const(name, GFP_KERNEL);
        if (!cache_name) {
                err = -ENOMEM;
                goto out_unlock;
        }

        s = create_cache(cache_name, size, size,
                         calculate_alignment(flags, align, size),
                         flags, ctor, NULL, NULL);
        if (IS_ERR(s)) {
                err = PTR_ERR(s);
                kfree_const(cache_name);
        }

out_unlock:
        mutex_unlock(&slab_mutex);

        memcg_put_cache_ids();
        put_online_mems();
        put_online_cpus();

        if (err) {
                if (flags & SLAB_PANIC)
                        panic("kmem_cache_create: Failed to create slab '%s'. Error %d\n",
                                name, err);
                else {
                        pr_warn("kmem_cache_create(%s) failed with error %d\n",
                                name, err);
                        dump_stack();
                }
                return NULL;
        }
        return s;
}
EXPORT_SYMBOL(kmem_cache_create);

static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
{
        LIST_HEAD(to_destroy);
        struct kmem_cache *s, *s2;

        /*
         * On destruction, SLAB_TYPESAFE_BY_RCU kmem_caches are put on the
         * @slab_caches_to_rcu_destroy list.  The slab pages are freed
         * through RCU and and the associated kmem_cache are dereferenced
         * while freeing the pages, so the kmem_caches should be freed only
         * after the pending RCU operations are finished.  As rcu_barrier()
         * is a pretty slow operation, we batch all pending destructions
         * asynchronously.
         */
        mutex_lock(&slab_mutex);
        list_splice_init(&slab_caches_to_rcu_destroy, &to_destroy);
        mutex_unlock(&slab_mutex);

        if (list_empty(&to_destroy))
                return;

        rcu_barrier();

        list_for_each_entry_safe(s, s2, &to_destroy, list) {
#ifdef SLAB_SUPPORTS_SYSFS
                sysfs_slab_release(s);
#else
                slab_kmem_cache_release(s);
#endif
        }
}

static int shutdown_cache(struct kmem_cache *s)
{
        /* free asan quarantined objects */
        kasan_cache_shutdown(s);

        if (__kmem_cache_shutdown(s) != 0)
                return -EBUSY;

        memcg_unlink_cache(s);
        list_del(&s->list);

        if (s->flags & SLAB_TYPESAFE_BY_RCU) {
                list_add_tail(&s->list, &slab_caches_to_rcu_destroy);
                schedule_work(&slab_caches_to_rcu_destroy_work);
        } else {
#ifdef SLAB_SUPPORTS_SYSFS
                sysfs_slab_release(s);
#else
                slab_kmem_cache_release(s);
#endif
        }

        return 0;
}

#if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
/*
 * memcg_create_kmem_cache - Create a cache for a memory cgroup.
 * @memcg: The memory cgroup the new cache is for.
 * @root_cache: The parent of the new cache.
 *
 * This function attempts to create a kmem cache that will serve allocation
 * requests going from @memcg to @root_cache. The new cache inherits properties
 * from its parent.
 */
void memcg_create_kmem_cache(struct mem_cgroup *memcg,
                             struct kmem_cache *root_cache)
{
        static char memcg_name_buf[NAME_MAX + 1]; /* protected by slab_mutex */
        struct cgroup_subsys_state *css = &memcg->css;
        struct memcg_cache_array *arr;
        struct kmem_cache *s = NULL;
        char *cache_name;
        int idx;

        get_online_cpus();
        get_online_mems();

        mutex_lock(&slab_mutex);

        /*
         * The memory cgroup could have been offlined while the cache
         * creation work was pending.
         */
        if (memcg->kmem_state != KMEM_ONLINE)
                goto out_unlock;

        idx = memcg_cache_id(memcg);
        arr = rcu_dereference_protected(root_cache->memcg_params.memcg_caches,
                                        lockdep_is_held(&slab_mutex));

        /*
         * Since per-memcg caches are created asynchronously on first
         * allocation (see memcg_kmem_get_cache()), several threads can try to
         * create the same cache, but only one of them may succeed.
         */
        if (arr->entries[idx])
                goto out_unlock;

        cgroup_name(css->cgroup, memcg_name_buf, sizeof(memcg_name_buf));
        cache_name = kasprintf(GFP_KERNEL, "%s(%llu:%s)", root_cache->name,
                               css->serial_nr, memcg_name_buf);
        if (!cache_name)
                goto out_unlock;

        s = create_cache(cache_name, root_cache->object_size,
                         root_cache->size, root_cache->align,
                         root_cache->flags & CACHE_CREATE_MASK,
                         root_cache->ctor, memcg, root_cache);
        /*
         * If we could not create a memcg cache, do not complain, because
         * that's not critical at all as we can always proceed with the root
         * cache.
         */
        if (IS_ERR(s)) {
                kfree(cache_name);
                goto out_unlock;
        }

        /*
         * Since readers won't lock (see cache_from_memcg_idx()), we need a
         * barrier here to ensure nobody will see the kmem_cache partially
         * initialized.
         */
        smp_wmb();
        arr->entries[idx] = s;

out_unlock:
        mutex_unlock(&slab_mutex);

        put_online_mems();
        put_online_cpus();
}

static void kmemcg_deactivate_workfn(struct work_struct *work)
{
        struct kmem_cache *s = container_of(work, struct kmem_cache,
                                            memcg_params.deact_work);

        get_online_cpus();
        get_online_mems();

        mutex_lock(&slab_mutex);

        s->memcg_params.deact_fn(s);

        mutex_unlock(&slab_mutex);

        put_online_mems();
        put_online_cpus();

        /* done, put the ref from slab_deactivate_memcg_cache_rcu_sched() */
        css_put(&s->memcg_params.memcg->css);
}

static void kmemcg_deactivate_rcufn(struct rcu_head *head)
{
        struct kmem_cache *s = container_of(head, struct kmem_cache,
                                            memcg_params.deact_rcu_head);

        /*
         * We need to grab blocking locks.  Bounce to ->deact_work.  The
         * work item shares the space with the RCU head and can't be
         * initialized eariler.
         */
        INIT_WORK(&s->memcg_params.deact_work, kmemcg_deactivate_workfn);
        queue_work(memcg_kmem_cache_wq, &s->memcg_params.deact_work);
}

/**
 * slab_deactivate_memcg_cache_rcu_sched - schedule deactivation after a
 *                                         sched RCU grace period
 * @s: target kmem_cache
 * @deact_fn: deactivation function to call
 *
 * Schedule @deact_fn to be invoked with online cpus, mems and slab_mutex
 * held after a sched RCU grace period.  The slab is guaranteed to stay
 * alive until @deact_fn is finished.  This is to be used from
 * __kmemcg_cache_deactivate().
 */
void slab_deactivate_memcg_cache_rcu_sched(struct kmem_cache *s,
                                           void (*deact_fn)(struct kmem_cache *))
{
        if (WARN_ON_ONCE(is_root_cache(s)) ||
            WARN_ON_ONCE(s->memcg_params.deact_fn))
                return;

        /* pin memcg so that @s doesn't get destroyed in the middle */
        css_get(&s->memcg_params.memcg->css);

        s->memcg_params.deact_fn = deact_fn;
        call_rcu_sched(&s->memcg_params.deact_rcu_head, kmemcg_deactivate_rcufn);
}

void memcg_deactivate_kmem_caches(struct mem_cgroup *memcg)
{
        int idx;
        struct memcg_cache_array *arr;
        struct kmem_cache *s, *c;

        idx = memcg_cache_id(memcg);

        get_online_cpus();
        get_online_mems();

        mutex_lock(&slab_mutex);
        list_for_each_entry(s, &slab_root_caches, root_caches_node) {
                arr = rcu_dereference_protected(s->memcg_params.memcg_caches,
                                                lockdep_is_held(&slab_mutex));
                c = arr->entries[idx];
                if (!c)
                        continue;

                __kmemcg_cache_deactivate(c);
                arr->entries[idx] = NULL;
        }
        mutex_unlock(&slab_mutex);

        put_online_mems();
        put_online_cpus();
}

void memcg_destroy_kmem_caches(struct mem_cgroup *memcg)
{
        struct kmem_cache *s, *s2;

        get_online_cpus();
        get_online_mems();

        mutex_lock(&slab_mutex);
        list_for_each_entry_safe(s, s2, &memcg->kmem_caches,
                                 memcg_params.kmem_caches_node) {
                /*
                 * The cgroup is about to be freed and therefore has no charges
                 * left. Hence, all its caches must be empty by now.
                 */
                BUG_ON(shutdown_cache(s));
        }
        mutex_unlock(&slab_mutex);

        put_online_mems();
        put_online_cpus();
}

static int shutdown_memcg_caches(struct kmem_cache *s)
{
        struct memcg_cache_array *arr;
        struct kmem_cache *c, *c2;
        LIST_HEAD(busy);
        int i;

        BUG_ON(!is_root_cache(s));

        /*
         * First, shutdown active caches, i.e. caches that belong to online
         * memory cgroups.
         */
        arr = rcu_dereference_protected(s->memcg_params.memcg_caches,
                                        lockdep_is_held(&slab_mutex));
        for_each_memcg_cache_index(i) {
                c = arr->entries[i];
                if (!c)
                        continue;
                if (shutdown_cache(c))
                        /*
                         * The cache still has objects. Move it to a temporary
                         * list so as not to try to destroy it for a second
                         * time while iterating over inactive caches below.
                         */
                        list_move(&c->memcg_params.children_node, &busy);
                else
                        /*
                         * The cache is empty and will be destroyed soon. Clear
                         * the pointer to it in the memcg_caches array so that
                         * it will never be accessed even if the root cache
                         * stays alive.
                         */
                        arr->entries[i] = NULL;
        }

        /*
         * Second, shutdown all caches left from memory cgroups that are now
         * offline.
         */
        list_for_each_entry_safe(c, c2, &s->memcg_params.children,
                                 memcg_params.children_node)
                shutdown_cache(c);

        list_splice(&busy, &s->memcg_params.children);

        /*
         * A cache being destroyed must be empty. In particular, this means
         * that all per memcg caches attached to it must be empty too.
         */
        if (!list_empty(&s->memcg_params.children))
                return -EBUSY;
        return 0;
}
#else
static inline int shutdown_memcg_caches(struct kmem_cache *s)
{
        return 0;
}
#endif /* CONFIG_MEMCG && !CONFIG_SLOB */

void slab_kmem_cache_release(struct kmem_cache *s)
{
        __kmem_cache_release(s);
        destroy_memcg_params(s);
        kfree_const(s->name);
        kmem_cache_free(kmem_cache, s);
}

void kmem_cache_destroy(struct kmem_cache *s)
{
        int err;

        if (unlikely(!s))
                return;

        get_online_cpus();
        get_online_mems();

        mutex_lock(&slab_mutex);

        s->refcount--;
        if (s->refcount)
                goto out_unlock;

        err = shutdown_memcg_caches(s);
        if (!err)
                err = shutdown_cache(s);

        if (err) {
                pr_err("kmem_cache_destroy %s: Slab cache still has objects\n",
                       s->name);
                dump_stack();
        }
out_unlock:
        mutex_unlock(&slab_mutex);

        put_online_mems();
        put_online_cpus();
}
EXPORT_SYMBOL(kmem_cache_destroy);

/**
 * kmem_cache_shrink - Shrink a cache.
 * @cachep: The cache to shrink.
 *
 * Releases as many slabs as possible for a cache.
 * To help debugging, a zero exit status indicates all slabs were released.
 */
int kmem_cache_shrink(struct kmem_cache *cachep)
{
        int ret;

        get_online_cpus();
        get_online_mems();
        kasan_cache_shrink(cachep);
        ret = __kmem_cache_shrink(cachep);
        put_online_mems();
        put_online_cpus();
        return ret;
}
EXPORT_SYMBOL(kmem_cache_shrink);

bool slab_is_available(void)
{
        return slab_state >= UP;
}

#ifndef CONFIG_SLOB
/* Create a cache during boot when no slab services are available yet */
void __init create_boot_cache(struct kmem_cache *s, const char *name, size_t size,
                slab_flags_t flags)
{
        int err;

        s->name = name;
        s->size = s->object_size = size;
        s->align = calculate_alignment(flags, ARCH_KMALLOC_MINALIGN, size);

        slab_init_memcg_params(s);

        err = __kmem_cache_create(s, flags);

        if (err)
                panic("Creation of kmalloc slab %s size=%zu failed. Reason %d\n",
                                        name, size, err);

        s->refcount = -1;       /* Exempt from merging for now */
}

struct kmem_cache *__init create_kmalloc_cache(const char *name, size_t size,
                                slab_flags_t flags)
{
        struct kmem_cache *s = kmem_cache_zalloc(kmem_cache, GFP_NOWAIT);

        if (!s)
                panic("Out of memory when creating slab %s\n", name);

        create_boot_cache(s, name, size, flags);
        list_add(&s->list, &slab_caches);
        memcg_link_cache(s);
        s->refcount = 1;
        return s;
}

struct kmem_cache *kmalloc_caches[KMALLOC_SHIFT_HIGH + 1];
EXPORT_SYMBOL(kmalloc_caches);

#ifdef CONFIG_ZONE_DMA
struct kmem_cache *kmalloc_dma_caches[KMALLOC_SHIFT_HIGH + 1];
EXPORT_SYMBOL(kmalloc_dma_caches);
#endif

/*
 * Conversion table for small slabs sizes / 8 to the index in the
 * kmalloc array. This is necessary for slabs < 192 since we have non power
 * of two cache sizes there. The size of larger slabs can be determined using
 * fls.
 */
static s8 size_index[24] = {
        3,      /* 8 */
        4,      /* 16 */
        5,      /* 24 */
        5,      /* 32 */
        6,      /* 40 */
        6,      /* 48 */
        6,      /* 56 */
        6,      /* 64 */
        1,      /* 72 */
        1,      /* 80 */
        1,      /* 88 */
        1,      /* 96 */
        7,      /* 104 */
        7,      /* 112 */
        7,      /* 120 */
        7,      /* 128 */
        2,      /* 136 */
        2,      /* 144 */
        2,      /* 152 */
        2,      /* 160 */
        2,      /* 168 */
        2,      /* 176 */
        2,      /* 184 */
        2       /* 192 */
};

static inline int size_index_elem(size_t bytes)
{
        return (bytes - 1) / 8;
}

/*
 * Find the kmem_cache structure that serves a given size of
 * allocation
 */
struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags)
{
        int index;

        if (unlikely(size > KMALLOC_MAX_SIZE)) {
                WARN_ON_ONCE(!(flags & __GFP_NOWARN));
                return NULL;
        }

        if (size <= 192) {
                if (!size)
                        return ZERO_SIZE_PTR;

                index = size_index[size_index_elem(size)];
        } else
                index = fls(size - 1);

#ifdef CONFIG_ZONE_DMA
        if (unlikely((flags & GFP_DMA)))
                return kmalloc_dma_caches[index];

#endif
        return kmalloc_caches[index];
}

/*
 * kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time.
 * kmalloc_index() supports up to 2^26=64MB, so the final entry of the table is
 * kmalloc-67108864.
 */
const struct kmalloc_info_struct kmalloc_info[] __initconst = {
        {NULL,                      0},         {"kmalloc-96",             96},
        {"kmalloc-192",           192},         {"kmalloc-8",               8},
        {"kmalloc-16",             16},         {"kmalloc-32",             32},
        {"kmalloc-64",             64},         {"kmalloc-128",           128},
        {"kmalloc-256",           256},         {"kmalloc-512",           512},
        {"kmalloc-1024",         1024},         {"kmalloc-2048",         2048},
        {"kmalloc-4096",         4096},         {"kmalloc-8192",         8192},
        {"kmalloc-16384",       16384},         {"kmalloc-32768",       32768},
        {"kmalloc-65536",       65536},         {"kmalloc-131072",     131072},
        {"kmalloc-262144",     262144},         {"kmalloc-524288",     524288},
        {"kmalloc-1048576",   1048576},         {"kmalloc-2097152",   2097152},
        {"kmalloc-4194304",   4194304},         {"kmalloc-8388608",   8388608},
        {"kmalloc-16777216", 16777216},         {"kmalloc-33554432", 33554432},
        {"kmalloc-67108864", 67108864}
};

/*
 * Patch up the size_index table if we have strange large alignment
 * requirements for the kmalloc array. This is only the case for
 * MIPS it seems. The standard arches will not generate any code here.
 *
 * Largest permitted alignment is 256 bytes due to the way we
 * handle the index determination for the smaller caches.
 *
 * Make sure that nothing crazy happens if someone starts tinkering
 * around with ARCH_KMALLOC_MINALIGN
 */
void __init setup_kmalloc_cache_index_table(void)
{
        int i;

        BUILD_BUG_ON(KMALLOC_MIN_SIZE > 256 ||
                (KMALLOC_MIN_SIZE & (KMALLOC_MIN_SIZE - 1)));

        for (i = 8; i < KMALLOC_MIN_SIZE; i += 8) {
                int elem = size_index_elem(i);

                if (elem >= ARRAY_SIZE(size_index))
                        break;
                size_index[elem] = KMALLOC_SHIFT_LOW;
        }

        if (KMALLOC_MIN_SIZE >= 64) {
                /*
                 * The 96 byte size cache is not used if the alignment
                 * is 64 byte.
                 */
                for (i = 64 + 8; i <= 96; i += 8)
                        size_index[size_index_elem(i)] = 7;

        }

        if (KMALLOC_MIN_SIZE >= 128) {
                /*
                 * The 192 byte sized cache is not used if the alignment
                 * is 128 byte. Redirect kmalloc to use the 256 byte cache
                 * instead.
                 */
                for (i = 128 + 8; i <= 192; i += 8)
                        size_index[size_index_elem(i)] = 8;
        }
}

static void __init new_kmalloc_cache(int idx, slab_flags_t flags)
{
        kmalloc_caches[idx] = create_kmalloc_cache(kmalloc_info[idx].name,
                                        kmalloc_info[idx].size, flags);
}

/*
 * Create the kmalloc array. Some of the regular kmalloc arrays
 * may already have been created because they were needed to
 * enable allocations for slab creation.
 */
void __init create_kmalloc_caches(slab_flags_t flags)
{
        int i;

        for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++) {
                if (!kmalloc_caches[i])
                        new_kmalloc_cache(i, flags);

                /*
                 * Caches that are not of the two-to-the-power-of size.
                 * These have to be created immediately after the
                 * earlier power of two caches
                 */
                if (KMALLOC_MIN_SIZE <= 32 && !kmalloc_caches[1] && i == 6)
                        new_kmalloc_cache(1, flags);
                if (KMALLOC_MIN_SIZE <= 64 && !kmalloc_caches[2] && i == 7)
                        new_kmalloc_cache(2, flags);
        }

        /* Kmalloc array is now usable */
        slab_state = UP;

#ifdef CONFIG_ZONE_DMA
        for (i = 0; i <= KMALLOC_SHIFT_HIGH; i++) {
                struct kmem_cache *s = kmalloc_caches[i];

                if (s) {
                        int size = kmalloc_size(i);
                        char *n = kasprintf(GFP_NOWAIT,
                                 "dma-kmalloc-%d", size);

                        BUG_ON(!n);
                        kmalloc_dma_caches[i] = create_kmalloc_cache(n,
                                size, SLAB_CACHE_DMA | flags);
                }
        }
#endif
}
#endif /* !CONFIG_SLOB */

/*
 * To avoid unnecessary overhead, we pass through large allocation requests
 * directly to the page allocator. We use __GFP_COMP, because we will need to
 * know the allocation order to free the pages properly in kfree.
 */
void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
{
        void *ret;
        struct page *page;

        flags |= __GFP_COMP;
        page = alloc_pages(flags, order);
        ret = page ? page_address(page) : NULL;
        kmemleak_alloc(ret, size, 1, flags);
        kasan_kmalloc_large(ret, size, flags);
        return ret;
}
EXPORT_SYMBOL(kmalloc_order);

#ifdef CONFIG_TRACING
void *kmalloc_order_trace(size_t size, gfp_t flags, unsigned int order)
{
        void *ret = kmalloc_order(size, flags, order);
        trace_kmalloc(_RET_IP_, ret, size, PAGE_SIZE << order, flags);
        return ret;
}
EXPORT_SYMBOL(kmalloc_order_trace);
#endif

#ifdef CONFIG_SLAB_FREELIST_RANDOM
/* Randomize a generic freelist */
static void freelist_randomize(struct rnd_state *state, unsigned int *list,
                        size_t count)
{
        size_t i;
        unsigned int rand;

        for (i = 0; i < count; i++)
                list[i] = i;

        /* Fisher-Yates shuffle */
        for (i = count - 1; i > 0; i--) {
                rand = prandom_u32_state(state);
                rand %= (i + 1);
                swap(list[i], list[rand]);
        }
}

/* Create a random sequence per cache */
int cache_random_seq_create(struct kmem_cache *cachep, unsigned int count,
                                    gfp_t gfp)
{
        struct rnd_state state;

        if (count < 2 || cachep->random_seq)
                return 0;

        cachep->random_seq = kcalloc(count, sizeof(unsigned int), gfp);
        if (!cachep->random_seq)
                return -ENOMEM;

        /* Get best entropy at this stage of boot */
        prandom_seed_state(&state, get_random_long());

        freelist_randomize(&state, cachep->random_seq, count);
        return 0;
}

/* Destroy the per-cache random freelist sequence */
void cache_random_seq_destroy(struct kmem_cache *cachep)
{
        kfree(cachep->random_seq);
        cachep->random_seq = NULL;
}
#endif /* CONFIG_SLAB_FREELIST_RANDOM */

#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG)
#ifdef CONFIG_SLAB
#define SLABINFO_RIGHTS (S_IWUSR | S_IRUSR)
#else
#define SLABINFO_RIGHTS S_IRUSR
#endif

static void print_slabinfo_header(struct seq_file *m)
{
        /*
         * Output format version, so at least we can change it
         * without _too_ many complaints.
         */
#ifdef CONFIG_DEBUG_SLAB
        seq_puts(m, "slabinfo - version: 2.1 (statistics)\n");
#else
        seq_puts(m, "slabinfo - version: 2.1\n");
#endif
        seq_puts(m, "# name            <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab>");
        seq_puts(m, " : tunables <limit> <batchcount> <sharedfactor>");
        seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail>");
#ifdef CONFIG_DEBUG_SLAB
        seq_puts(m, " : globalstat <listallocs> <maxobjs> <grown> <reaped> <error> <maxfreeable> <nodeallocs> <remotefrees> <alienoverflow>");
        seq_puts(m, " : cpustat <allochit> <allocmiss> <freehit> <freemiss>");
#endif
        seq_putc(m, '\n');
}

void *slab_start(struct seq_file *m, loff_t *pos)
{
        mutex_lock(&slab_mutex);
        return seq_list_start(&slab_root_caches, *pos);
}

void *slab_next(struct seq_file *m, void *p, loff_t *pos)
{
        return seq_list_next(p, &slab_root_caches, pos);
}

void slab_stop(struct seq_file *m, void *p)
{
        mutex_unlock(&slab_mutex);
}

static void
memcg_accumulate_slabinfo(struct kmem_cache *s, struct slabinfo *info)
{
        struct kmem_cache *c;
        struct slabinfo sinfo;

        if (!is_root_cache(s))
                return;

        for_each_memcg_cache(c, s) {
                memset(&sinfo, 0, sizeof(sinfo));
                get_slabinfo(c, &sinfo);

                info->active_slabs += sinfo.active_slabs;
                info->num_slabs += sinfo.num_slabs;
                info->shared_avail += sinfo.shared_avail;
                info->active_objs += sinfo.active_objs;
                info->num_objs += sinfo.num_objs;
        }
}

static void cache_show(struct kmem_cache *s, struct seq_file *m)
{
        struct slabinfo sinfo;

        memset(&sinfo, 0, sizeof(sinfo));
        get_slabinfo(s, &sinfo);

        memcg_accumulate_slabinfo(s, &sinfo);

        seq_printf(m, "%-17s %6lu %6lu %6u %4u %4d",
                   cache_name(s), sinfo.active_objs, sinfo.num_objs, s->size,
                   sinfo.objects_per_slab, (1 << sinfo.cache_order));

        seq_printf(m, " : tunables %4u %4u %4u",
                   sinfo.limit, sinfo.batchcount, sinfo.shared);
        seq_printf(m, " : slabdata %6lu %6lu %6lu",
                   sinfo.active_slabs, sinfo.num_slabs, sinfo.shared_avail);
        slabinfo_show_stats(m, s);
        seq_putc(m, '\n');
}

static int slab_show(struct seq_file *m, void *p)
{
        struct kmem_cache *s = list_entry(p, struct kmem_cache, root_caches_node);

        if (p == slab_root_caches.next)
                print_slabinfo_header(m);
        cache_show(s, m);
        return 0;
}

void dump_unreclaimable_slab(void)
{
        struct kmem_cache *s, *s2;
        struct slabinfo sinfo;

        /*
         * Here acquiring slab_mutex is risky since we don't prefer to get
         * sleep in oom path. But, without mutex hold, it may introduce a
         * risk of crash.
         * Use mutex_trylock to protect the list traverse, dump nothing
         * without acquiring the mutex.
         */
        if (!mutex_trylock(&slab_mutex)) {
                pr_warn("excessive unreclaimable slab but cannot dump stats\n");
                return;
        }

        pr_info("Unreclaimable slab info:\n");
        pr_info("Name                      Used          Total\n");

        list_for_each_entry_safe(s, s2, &slab_caches, list) {
                if (!is_root_cache(s) || (s->flags & SLAB_RECLAIM_ACCOUNT))
                        continue;

                get_slabinfo(s, &sinfo);

                if (sinfo.num_objs > 0)
                        pr_info("%-17s %10luKB %10luKB\n", cache_name(s),
                                (sinfo.active_objs * s->size) / 1024,
                                (sinfo.num_objs * s->size) / 1024);
        }
        mutex_unlock(&slab_mutex);
}

#if defined(CONFIG_MEMCG)
void *memcg_slab_start(struct seq_file *m, loff_t *pos)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));

        mutex_lock(&slab_mutex);
        return seq_list_start(&memcg->kmem_caches, *pos);
}

void *memcg_slab_next(struct seq_file *m, void *p, loff_t *pos)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));

        return seq_list_next(p, &memcg->kmem_caches, pos);
}

void memcg_slab_stop(struct seq_file *m, void *p)
{
        mutex_unlock(&slab_mutex);
}

int memcg_slab_show(struct seq_file *m, void *p)
{
        struct kmem_cache *s = list_entry(p, struct kmem_cache,
                                          memcg_params.kmem_caches_node);
        struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));

        if (p == memcg->kmem_caches.next)
                print_slabinfo_header(m);
        cache_show(s, m);
        return 0;
}
#endif

/*
 * slabinfo_op - iterator that generates /proc/slabinfo
 *
 * Output layout:
 * cache-name
 * num-active-objs
 * total-objs
 * object size
 * num-active-slabs
 * total-slabs
 * num-pages-per-slab
 * + further values on SMP and with statistics enabled
 */
static const struct seq_operations slabinfo_op = {
        .start = slab_start,
        .next = slab_next,
        .stop = slab_stop,
        .show = slab_show,
};

static int slabinfo_open(struct inode *inode, struct file *file)
{
        return seq_open(file, &slabinfo_op);
}

static const struct file_operations proc_slabinfo_operations = {
        .open           = slabinfo_open,
        .read           = seq_read,
        .write          = slabinfo_write,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

static int __init slab_proc_init(void)
{
        proc_create("slabinfo", SLABINFO_RIGHTS, NULL,
                                                &proc_slabinfo_operations);
        return 0;
}
module_init(slab_proc_init);
#endif /* CONFIG_SLAB || CONFIG_SLUB_DEBUG */

static __always_inline void *__do_krealloc(const void *p, size_t new_size,
                                           gfp_t flags)
{
        void *ret;
        size_t ks = 0;

        if (p)
                ks = ksize(p);

        if (ks >= new_size) {
                kasan_krealloc((void *)p, new_size, flags);
                return (void *)p;
        }

        ret = kmalloc_track_caller(new_size, flags);
        if (ret && p)
                memcpy(ret, p, ks);

        return ret;
}

/**
 * __krealloc - like krealloc() but don't free @p.
 * @p: object to reallocate memory for.
 * @new_size: how many bytes of memory are required.
 * @flags: the type of memory to allocate.
 *
 * This function is like krealloc() except it never frees the originally
 * allocated buffer. Use this if you don't want to free the buffer immediately
 * like, for example, with RCU.
 */
void *__krealloc(const void *p, size_t new_size, gfp_t flags)
{
        if (unlikely(!new_size))
                return ZERO_SIZE_PTR;

        return __do_krealloc(p, new_size, flags);

}
EXPORT_SYMBOL(__krealloc);

/**
 * krealloc - reallocate memory. The contents will remain unchanged.
 * @p: object to reallocate memory for.
 * @new_size: how many bytes of memory are required.
 * @flags: the type of memory to allocate.
 *
 * The contents of the object pointed to are preserved up to the
 * lesser of the new and old sizes.  If @p is %NULL, krealloc()
 * behaves exactly like kmalloc().  If @new_size is 0 and @p is not a
 * %NULL pointer, the object pointed to is freed.
 */
void *krealloc(const void *p, size_t new_size, gfp_t flags)
{
        void *ret;

        if (unlikely(!new_size)) {
                kfree(p);
                return ZERO_SIZE_PTR;
        }

        ret = __do_krealloc(p, new_size, flags);
        if (ret && p != ret)
                kfree(p);

        return ret;
}
EXPORT_SYMBOL(krealloc);

/**
 * kzfree - like kfree but zero memory
 * @p: object to free memory of
 *
 * The memory of the object @p points to is zeroed before freed.
 * If @p is %NULL, kzfree() does nothing.
 *
 * Note: this function zeroes the whole allocated buffer which can be a good
 * deal bigger than the requested buffer size passed to kmalloc(). So be
 * careful when using this function in performance sensitive code.
 */
void kzfree(const void *p)
{
        size_t ks;
        void *mem = (void *)p;

        if (unlikely(ZERO_OR_NULL_PTR(mem)))
                return;
        ks = ksize(mem);
        memset(mem, 0, ks);
        kfree(mem);
}
EXPORT_SYMBOL(kzfree);

/* Tracepoints definitions. */
EXPORT_TRACEPOINT_SYMBOL(kmalloc);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
EXPORT_TRACEPOINT_SYMBOL(kmalloc_node);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
EXPORT_TRACEPOINT_SYMBOL(kfree);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);