dcache: close d_move race in d_splice_alias

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

/*
 * 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>
#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;

#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;
                }

#if !defined(CONFIG_SLUB)
                if (!strcmp(s->name, name)) {
                        pr_err("%s (%s): Cache name already exists.\n",
                               __func__, name);
                        dump_stack();
                        s = NULL;
                        return -EINVAL;
                }
#endif
        }

        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

#ifdef CONFIG_MEMCG_KMEM
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_caches, list) {
                if (!is_root_cache(s))
                        continue;

                ret = memcg_update_cache_size(s, num_memcgs);
                /*
                 * See comment in memcontrol.c, memcg_update_cache_size:
                 * Instead of freeing the memory, we'll just leave the caches
                 * up to this point in an updated state.
                 */
                if (ret)
                        goto out;
        }

        memcg_update_array_size(num_memcgs);
out:
        mutex_unlock(&slab_mutex);
        return ret;
}
#endif

/*
 * 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(unsigned long 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 *
do_kmem_cache_create(char *name, size_t object_size, size_t size, size_t align,
                     unsigned long 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 = memcg_alloc_cache_params(memcg, s, 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);
out:
        if (err)
                return ERR_PTR(err);
        return s;

out_free_cache:
        memcg_free_cache_params(s);
        kfree(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,
                  unsigned long flags, void (*ctor)(void *))
{
        struct kmem_cache *s;
        char *cache_name;
        int err;

        get_online_cpus();
        get_online_mems();

        mutex_lock(&slab_mutex);

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

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

out_unlock:
        mutex_unlock(&slab_mutex);

        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 {
                        printk(KERN_WARNING "kmem_cache_create(%s) failed with error %d",
                                name, err);
                        dump_stack();
                }
                return NULL;
        }
        return s;
}
EXPORT_SYMBOL(kmem_cache_create);

#ifdef CONFIG_MEMCG_KMEM
/*
 * 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.
 * @memcg_name: The name of the memory cgroup (used for naming 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.
 */
struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
                                           struct kmem_cache *root_cache,
                                           const char *memcg_name)
{
        struct kmem_cache *s = NULL;
        char *cache_name;

        get_online_cpus();
        get_online_mems();

        mutex_lock(&slab_mutex);

        cache_name = kasprintf(GFP_KERNEL, "%s(%d:%s)", root_cache->name,
                               memcg_cache_id(memcg), memcg_name);
        if (!cache_name)
                goto out_unlock;

        s = do_kmem_cache_create(cache_name, root_cache->object_size,
                                 root_cache->size, root_cache->align,
                                 root_cache->flags, root_cache->ctor,
                                 memcg, root_cache);
        if (IS_ERR(s)) {
                kfree(cache_name);
                s = NULL;
        }

out_unlock:
        mutex_unlock(&slab_mutex);

        put_online_mems();
        put_online_cpus();

        return s;
}

static int memcg_cleanup_cache_params(struct kmem_cache *s)
{
        int rc;

        if (!s->memcg_params ||
            !s->memcg_params->is_root_cache)
                return 0;

        mutex_unlock(&slab_mutex);
        rc = __memcg_cleanup_cache_params(s);
        mutex_lock(&slab_mutex);

        return rc;
}
#else
static int memcg_cleanup_cache_params(struct kmem_cache *s)
{
        return 0;
}
#endif /* CONFIG_MEMCG_KMEM */

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

void kmem_cache_destroy(struct kmem_cache *s)
{
        get_online_cpus();
        get_online_mems();

        mutex_lock(&slab_mutex);

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

        if (memcg_cleanup_cache_params(s) != 0)
                goto out_unlock;

        if (__kmem_cache_shutdown(s) != 0) {
                printk(KERN_ERR "kmem_cache_destroy %s: "
                       "Slab cache still has objects\n", s->name);
                dump_stack();
                goto out_unlock;
        }

        list_del(&s->list);

        mutex_unlock(&slab_mutex);
        if (s->flags & SLAB_DESTROY_BY_RCU)
                rcu_barrier();

        memcg_free_cache_params(s);
#ifdef SLAB_SUPPORTS_SYSFS
        sysfs_slab_remove(s);
#else
        slab_kmem_cache_release(s);
#endif
        goto out;

out_unlock:
        mutex_unlock(&slab_mutex);
out:
        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();
        ret = __kmem_cache_shrink(cachep);
        put_online_mems();
        put_online_cpus();
        return ret;
}
EXPORT_SYMBOL(kmem_cache_shrink);

int 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,
                unsigned long flags)
{
        int err;

        s->name = name;
        s->size = s->object_size = size;
        s->align = calculate_alignment(flags, ARCH_KMALLOC_MINALIGN, size);
        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,
                                unsigned long 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);
        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];
}

/*
 * 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(unsigned long flags)
{
        int i;

        /*
         * 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
         */
        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;
        }
        for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++) {
                if (!kmalloc_caches[i]) {
                        kmalloc_caches[i] = create_kmalloc_cache(NULL,
                                                        1 << 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)
                        kmalloc_caches[1] = create_kmalloc_cache(NULL, 96, flags);

                if (KMALLOC_MIN_SIZE <= 64 && !kmalloc_caches[2] && i == 7)
                        kmalloc_caches[2] = create_kmalloc_cache(NULL, 192, flags);
        }

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

        for (i = 0; i <= KMALLOC_SHIFT_HIGH; i++) {
                struct kmem_cache *s = kmalloc_caches[i];
                char *n;

                if (s) {
                        n = kasprintf(GFP_NOWAIT, "kmalloc-%d", kmalloc_size(i));

                        BUG_ON(!n);
                        s->name = n;
                }
        }

#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_kmem_pages(flags, order);
        ret = page ? page_address(page) : NULL;
        kmemleak_alloc(ret, size, 1, 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_SLABINFO

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

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');
}

static void *s_start(struct seq_file *m, loff_t *pos)
{
        loff_t n = *pos;

        mutex_lock(&slab_mutex);
        if (!n)
                print_slabinfo_header(m);

        return seq_list_start(&slab_caches, *pos);
}

void *slab_next(struct seq_file *m, void *p, loff_t *pos)
{
        return seq_list_next(p, &slab_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;
        int i;

        if (!is_root_cache(s))
                return;

        for_each_memcg_cache_index(i) {
                c = cache_from_memcg_idx(s, i);
                if (!c)
                        continue;

                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;
        }
}

int 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');
        return 0;
}

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

        if (!is_root_cache(s))
                return 0;
        return cache_show(s, m);
}

/*
 * 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 = s_start,
        .next = slab_next,
        .stop = slab_stop,
        .show = s_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_SLABINFO */