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authorRoman Gushchin <guro@fb.com>2020-08-07 09:21:10 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-07 21:33:25 +0300
commit9855609bde03e2472b99a95e869d29ee1e78a751 (patch)
treeefc534e04c3e1acbc1dcb4dcb681c30bd072fc59 /mm/slab_common.c
parent0f876e4dc55db5fafef774917fd66e1373c0f390 (diff)
downloadlinux-9855609bde03e2472b99a95e869d29ee1e78a751.tar.xz
mm: memcg/slab: use a single set of kmem_caches for all accounted allocations
This is fairly big but mostly red patch, which makes all accounted slab allocations use a single set of kmem_caches instead of creating a separate set for each memory cgroup. Because the number of non-root kmem_caches is now capped by the number of root kmem_caches, there is no need to shrink or destroy them prematurely. They can be perfectly destroyed together with their root counterparts. This allows to dramatically simplify the management of non-root kmem_caches and delete a ton of code. This patch performs the following changes: 1) introduces memcg_params.memcg_cache pointer to represent the kmem_cache which will be used for all non-root allocations 2) reuses the existing memcg kmem_cache creation mechanism to create memcg kmem_cache on the first allocation attempt 3) memcg kmem_caches are named <kmemcache_name>-memcg, e.g. dentry-memcg 4) simplifies memcg_kmem_get_cache() to just return memcg kmem_cache or schedule it's creation and return the root cache 5) removes almost all non-root kmem_cache management code (separate refcounter, reparenting, shrinking, etc) 6) makes slab debugfs to display root_mem_cgroup css id and never show :dead and :deact flags in the memcg_slabinfo attribute. Following patches in the series will simplify the kmem_cache creation. Signed-off-by: Roman Gushchin <guro@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/20200623174037.3951353-13-guro@fb.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slab_common.c')
-rw-r--r--mm/slab_common.c459
1 files changed, 47 insertions, 412 deletions
diff --git a/mm/slab_common.c b/mm/slab_common.c
index f86431d0de73..e752132eb64d 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -133,141 +133,36 @@ int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr,
#ifdef CONFIG_MEMCG_KMEM
LIST_HEAD(slab_root_caches);
-static DEFINE_SPINLOCK(memcg_kmem_wq_lock);
-
-static void kmemcg_cache_shutdown(struct percpu_ref *percpu_ref);
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);
- s->memcg_params.dying = false;
+ s->memcg_params.memcg_cache = NULL;
}
-static int init_memcg_params(struct kmem_cache *s,
- struct kmem_cache *root_cache)
+static void init_memcg_params(struct kmem_cache *s,
+ struct kmem_cache *root_cache)
{
- struct memcg_cache_array *arr;
-
- if (root_cache) {
- int ret = percpu_ref_init(&s->memcg_params.refcnt,
- kmemcg_cache_shutdown,
- 0, GFP_KERNEL);
- if (ret)
- return ret;
-
+ if (root_cache)
s->memcg_params.root_cache = root_cache;
- 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));
- } else {
- mem_cgroup_put(s->memcg_params.memcg);
- WRITE_ONCE(s->memcg_params.memcg, NULL);
- percpu_ref_exit(&s->memcg_params.refcnt);
- }
-}
-
-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;
+ else
+ slab_init_memcg_params(s);
}
-int memcg_update_all_caches(int num_memcgs)
+void memcg_link_cache(struct kmem_cache *s)
{
- 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, struct mem_cgroup *memcg)
-{
- if (is_root_cache(s)) {
+ if (is_root_cache(s))
list_add(&s->root_caches_node, &slab_root_caches);
- } else {
- css_get(&memcg->css);
- s->memcg_params.memcg = memcg;
- 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)) {
+ 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 kmem_cache *root_cache)
-{
- return 0;
-}
-
-static inline void destroy_memcg_params(struct kmem_cache *s)
+static inline void init_memcg_params(struct kmem_cache *s,
+ struct kmem_cache *root_cache)
{
}
@@ -328,14 +223,6 @@ int slab_unmergeable(struct kmem_cache *s)
if (s->refcount < 0)
return 1;
-#ifdef CONFIG_MEMCG_KMEM
- /*
- * Skip the dying kmem_cache.
- */
- if (s->memcg_params.dying)
- return 1;
-#endif
-
return 0;
}
@@ -390,7 +277,7 @@ static struct kmem_cache *create_cache(const char *name,
unsigned int object_size, unsigned int align,
slab_flags_t flags, unsigned int useroffset,
unsigned int usersize, void (*ctor)(void *),
- struct mem_cgroup *memcg, struct kmem_cache *root_cache)
+ struct kmem_cache *root_cache)
{
struct kmem_cache *s;
int err;
@@ -410,24 +297,20 @@ static struct kmem_cache *create_cache(const char *name,
s->useroffset = useroffset;
s->usersize = usersize;
- err = init_memcg_params(s, root_cache);
- if (err)
- goto out_free_cache;
-
+ init_memcg_params(s, root_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, memcg);
+ 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;
}
@@ -514,7 +397,7 @@ kmem_cache_create_usercopy(const char *name,
s = create_cache(cache_name, size,
calculate_alignment(flags, align, size),
- flags, useroffset, usersize, ctor, NULL, NULL);
+ flags, useroffset, usersize, ctor, NULL);
if (IS_ERR(s)) {
err = PTR_ERR(s);
kfree_const(cache_name);
@@ -639,51 +522,27 @@ static int shutdown_cache(struct kmem_cache *s)
#ifdef CONFIG_MEMCG_KMEM
/*
- * memcg_create_kmem_cache - Create a cache for a memory cgroup.
- * @memcg: The memory cgroup the new cache is for.
+ * memcg_create_kmem_cache - Create a cache for non-root memory cgroups.
* @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.
+ * requests going all non-root memory cgroups 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)
+void memcg_create_kmem_cache(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)
+ if (root_cache->memcg_params.memcg_cache)
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);
+ cache_name = kasprintf(GFP_KERNEL, "%s-memcg", root_cache->name);
if (!cache_name)
goto out_unlock;
@@ -691,7 +550,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
root_cache->align,
root_cache->flags & CACHE_CREATE_MASK,
root_cache->useroffset, root_cache->usersize,
- root_cache->ctor, memcg, root_cache);
+ root_cache->ctor, 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
@@ -708,7 +567,7 @@ void memcg_create_kmem_cache(struct mem_cgroup *memcg,
* initialized.
*/
smp_wmb();
- arr->entries[idx] = s;
+ root_cache->memcg_params.memcg_cache = s;
out_unlock:
mutex_unlock(&slab_mutex);
@@ -717,231 +576,40 @@ out_unlock:
put_online_cpus();
}
-static void kmemcg_workfn(struct work_struct *work)
-{
- struct kmem_cache *s = container_of(work, struct kmem_cache,
- memcg_params.work);
-
- get_online_cpus();
- get_online_mems();
-
- mutex_lock(&slab_mutex);
- s->memcg_params.work_fn(s);
- mutex_unlock(&slab_mutex);
-
- put_online_mems();
- put_online_cpus();
-}
-
-static void kmemcg_rcufn(struct rcu_head *head)
-{
- struct kmem_cache *s = container_of(head, struct kmem_cache,
- memcg_params.rcu_head);
-
- /*
- * We need to grab blocking locks. Bounce to ->work. The
- * work item shares the space with the RCU head and can't be
- * initialized earlier.
- */
- INIT_WORK(&s->memcg_params.work, kmemcg_workfn);
- queue_work(memcg_kmem_cache_wq, &s->memcg_params.work);
-}
-
-static void kmemcg_cache_shutdown_fn(struct kmem_cache *s)
-{
- WARN_ON(shutdown_cache(s));
-}
-
-static void kmemcg_cache_shutdown(struct percpu_ref *percpu_ref)
-{
- struct kmem_cache *s = container_of(percpu_ref, struct kmem_cache,
- memcg_params.refcnt);
- unsigned long flags;
-
- spin_lock_irqsave(&memcg_kmem_wq_lock, flags);
- if (s->memcg_params.root_cache->memcg_params.dying)
- goto unlock;
-
- s->memcg_params.work_fn = kmemcg_cache_shutdown_fn;
- INIT_WORK(&s->memcg_params.work, kmemcg_workfn);
- queue_work(memcg_kmem_cache_wq, &s->memcg_params.work);
-
-unlock:
- spin_unlock_irqrestore(&memcg_kmem_wq_lock, flags);
-}
-
-static void kmemcg_cache_deactivate_after_rcu(struct kmem_cache *s)
-{
- __kmemcg_cache_deactivate_after_rcu(s);
- percpu_ref_kill(&s->memcg_params.refcnt);
-}
-
-static void kmemcg_cache_deactivate(struct kmem_cache *s)
-{
- if (WARN_ON_ONCE(is_root_cache(s)))
- return;
-
- __kmemcg_cache_deactivate(s);
- s->flags |= SLAB_DEACTIVATED;
-
- /*
- * memcg_kmem_wq_lock is used to synchronize memcg_params.dying
- * flag and make sure that no new kmem_cache deactivation tasks
- * are queued (see flush_memcg_workqueue() ).
- */
- spin_lock_irq(&memcg_kmem_wq_lock);
- if (s->memcg_params.root_cache->memcg_params.dying)
- goto unlock;
-
- s->memcg_params.work_fn = kmemcg_cache_deactivate_after_rcu;
- call_rcu(&s->memcg_params.rcu_head, kmemcg_rcufn);
-unlock:
- spin_unlock_irq(&memcg_kmem_wq_lock);
-}
-
-void memcg_deactivate_kmem_caches(struct mem_cgroup *memcg,
- struct mem_cgroup *parent)
-{
- int idx;
- struct memcg_cache_array *arr;
- struct kmem_cache *s, *c;
- unsigned int nr_reparented;
-
- 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;
- }
- nr_reparented = 0;
- list_for_each_entry(s, &memcg->kmem_caches,
- memcg_params.kmem_caches_node) {
- WRITE_ONCE(s->memcg_params.memcg, parent);
- css_put(&memcg->css);
- nr_reparented++;
- }
- if (nr_reparented) {
- list_splice_init(&memcg->kmem_caches,
- &parent->kmem_caches);
- css_get_many(&parent->css, nr_reparented);
- }
- 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);
+ if (s->memcg_params.memcg_cache)
+ WARN_ON(shutdown_cache(s->memcg_params.memcg_cache));
- /*
- * 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;
}
-static void memcg_set_kmem_cache_dying(struct kmem_cache *s)
-{
- spin_lock_irq(&memcg_kmem_wq_lock);
- s->memcg_params.dying = true;
- spin_unlock_irq(&memcg_kmem_wq_lock);
-}
-
static void flush_memcg_workqueue(struct kmem_cache *s)
{
/*
- * SLAB and SLUB deactivate the kmem_caches through call_rcu. Make
- * sure all registered rcu callbacks have been invoked.
- */
- rcu_barrier();
-
- /*
* SLAB and SLUB create memcg kmem_caches through workqueue and SLUB
* deactivates the memcg kmem_caches through workqueue. Make sure all
* previous workitems on workqueue are processed.
*/
if (likely(memcg_kmem_cache_wq))
flush_workqueue(memcg_kmem_cache_wq);
-
- /*
- * If we're racing with children kmem_cache deactivation, it might
- * take another rcu grace period to complete their destruction.
- * At this moment the corresponding percpu_ref_kill() call should be
- * done, but it might take another rcu grace period to complete
- * switching to the atomic mode.
- * Please, note that we check without grabbing the slab_mutex. It's safe
- * because at this moment the children list can't grow.
- */
- if (!list_empty(&s->memcg_params.children))
- rcu_barrier();
}
#else
static inline int shutdown_memcg_caches(struct kmem_cache *s)
{
return 0;
}
+
+static inline void flush_memcg_workqueue(struct kmem_cache *s)
+{
+}
#endif /* CONFIG_MEMCG_KMEM */
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);
}
@@ -953,6 +621,8 @@ void kmem_cache_destroy(struct kmem_cache *s)
if (unlikely(!s))
return;
+ flush_memcg_workqueue(s);
+
get_online_cpus();
get_online_mems();
@@ -962,22 +632,6 @@ void kmem_cache_destroy(struct kmem_cache *s)
if (s->refcount)
goto out_unlock;
-#ifdef CONFIG_MEMCG_KMEM
- memcg_set_kmem_cache_dying(s);
-
- mutex_unlock(&slab_mutex);
-
- put_online_mems();
- put_online_cpus();
-
- flush_memcg_workqueue(s);
-
- get_online_cpus();
- get_online_mems();
-
- mutex_lock(&slab_mutex);
-#endif
-
err = shutdown_memcg_caches(s);
if (!err)
err = shutdown_cache(s);
@@ -1019,7 +673,7 @@ int kmem_cache_shrink(struct kmem_cache *cachep)
EXPORT_SYMBOL(kmem_cache_shrink);
/**
- * kmem_cache_shrink_all - shrink a cache and all memcg caches for root cache
+ * kmem_cache_shrink_all - shrink root and memcg caches
* @s: The cache pointer
*/
void kmem_cache_shrink_all(struct kmem_cache *s)
@@ -1036,21 +690,11 @@ void kmem_cache_shrink_all(struct kmem_cache *s)
kasan_cache_shrink(s);
__kmem_cache_shrink(s);
- /*
- * We have to take the slab_mutex to protect from the memcg list
- * modification.
- */
- mutex_lock(&slab_mutex);
- for_each_memcg_cache(c, s) {
- /*
- * Don't need to shrink deactivated memcg caches.
- */
- if (s->flags & SLAB_DEACTIVATED)
- continue;
+ c = memcg_cache(s);
+ if (c) {
kasan_cache_shrink(c);
__kmem_cache_shrink(c);
}
- mutex_unlock(&slab_mutex);
put_online_mems();
put_online_cpus();
}
@@ -1105,7 +749,7 @@ struct kmem_cache *__init create_kmalloc_cache(const char *name,
create_boot_cache(s, name, size, flags, useroffset, usersize);
list_add(&s->list, &slab_caches);
- memcg_link_cache(s, NULL);
+ memcg_link_cache(s);
s->refcount = 1;
return s;
}
@@ -1483,7 +1127,8 @@ memcg_accumulate_slabinfo(struct kmem_cache *s, struct slabinfo *info)
if (!is_root_cache(s))
return;
- for_each_memcg_cache(c, s) {
+ c = memcg_cache(s);
+ if (c) {
memset(&sinfo, 0, sizeof(sinfo));
get_slabinfo(c, &sinfo);
@@ -1614,7 +1259,7 @@ module_init(slab_proc_init);
#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_MEMCG_KMEM)
/*
- * Display information about kmem caches that have child memcg caches.
+ * Display information about kmem caches that have memcg cache.
*/
static int memcg_slabinfo_show(struct seq_file *m, void *unused)
{
@@ -1626,9 +1271,9 @@ static int memcg_slabinfo_show(struct seq_file *m, void *unused)
seq_puts(m, " <active_slabs> <num_slabs>\n");
list_for_each_entry(s, &slab_root_caches, root_caches_node) {
/*
- * Skip kmem caches that don't have any memcg children.
+ * Skip kmem caches that don't have the memcg cache.
*/
- if (list_empty(&s->memcg_params.children))
+ if (!s->memcg_params.memcg_cache)
continue;
memset(&sinfo, 0, sizeof(sinfo));
@@ -1637,23 +1282,13 @@ static int memcg_slabinfo_show(struct seq_file *m, void *unused)
cache_name(s), sinfo.active_objs, sinfo.num_objs,
sinfo.active_slabs, sinfo.num_slabs);
- for_each_memcg_cache(c, s) {
- struct cgroup_subsys_state *css;
- char *status = "";
-
- css = &c->memcg_params.memcg->css;
- if (!(css->flags & CSS_ONLINE))
- status = ":dead";
- else if (c->flags & SLAB_DEACTIVATED)
- status = ":deact";
-
- memset(&sinfo, 0, sizeof(sinfo));
- get_slabinfo(c, &sinfo);
- seq_printf(m, "%-17s %4d%-6s %6lu %6lu %6lu %6lu\n",
- cache_name(c), css->id, status,
- sinfo.active_objs, sinfo.num_objs,
- sinfo.active_slabs, sinfo.num_slabs);
- }
+ c = s->memcg_params.memcg_cache;
+ memset(&sinfo, 0, sizeof(sinfo));
+ get_slabinfo(c, &sinfo);
+ seq_printf(m, "%-17s %4d %6lu %6lu %6lu %6lu\n",
+ cache_name(c), root_mem_cgroup->css.id,
+ sinfo.active_objs, sinfo.num_objs,
+ sinfo.active_slabs, sinfo.num_slabs);
}
mutex_unlock(&slab_mutex);
return 0;