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Commit 03afc0e2 authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
Browse files

slab: get_online_mems for kmem_cache_{create,destroy,shrink} 



When we create a sl[au]b cache, we allocate kmem_cache_node structures
for each online NUMA node.  To handle nodes taken online/offline, we
register memory hotplug notifier and allocate/free kmem_cache_node
corresponding to the node that changes its state for each kmem cache.

To synchronize between the two paths we hold the slab_mutex during both
the cache creationg/destruction path and while tuning per-node parts of
kmem caches in memory hotplug handler, but that's not quite right,
because it does not guarantee that a newly created cache will have all
kmem_cache_nodes initialized in case it races with memory hotplug.  For
instance, in case of slub:

    CPU0                            CPU1
    ----                            ----
    kmem_cache_create:              online_pages:
     __kmem_cache_create:            slab_memory_callback:
                                      slab_mem_going_online_callback:
                                       lock slab_mutex
                                       for each slab_caches list entry
                                           allocate kmem_cache node
                                       unlock slab_mutex
      lock slab_mutex
      init_kmem_cache_nodes:
       for_each_node_state(node, N_NORMAL_MEMORY)
           allocate kmem_cache node
      add kmem_cache to slab_caches list
      unlock slab_mutex
                                    online_pages (continued):
                                     node_states_set_node

As a result we'll get a kmem cache with not all kmem_cache_nodes
allocated.

To avoid issues like that we should hold get/put_online_mems() during
the whole kmem cache creation/destruction/shrink paths, just like we
deal with cpu hotplug.  This patch does the trick.

Note, that after it's applied, there is no need in taking the slab_mutex
for kmem_cache_shrink any more, so it is removed from there.

Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Jiang Liu <liuj97@gmail.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bfc8c901

mm/slab.c

+2 −24
Original line number Diff line number Diff line
@@ -2480,8 +2480,7 @@ static int drain_freelist(struct kmem_cache *cache, 
	return nr_freed;

}



/* Called with slab_mutex held to protect against cpu hotplug */

static int __cache_shrink(struct kmem_cache *cachep)

int __kmem_cache_shrink(struct kmem_cache *cachep)

{

	int ret = 0, i = 0;

	struct kmem_cache_node *n;
@@ -2502,32 +2501,11 @@ static int __cache_shrink(struct kmem_cache *cachep) 
	return (ret ? 1 : 0);

}



/**

 * 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;

	BUG_ON(!cachep || in_interrupt());



	get_online_cpus();

	mutex_lock(&slab_mutex);

	ret = __cache_shrink(cachep);

	mutex_unlock(&slab_mutex);

	put_online_cpus();

	return ret;

}

EXPORT_SYMBOL(kmem_cache_shrink);



int __kmem_cache_shutdown(struct kmem_cache *cachep)

{

	int i;

	struct kmem_cache_node *n;

	int rc = __cache_shrink(cachep);

	int rc = __kmem_cache_shrink(cachep);



	if (rc)

		return rc;

mm/slab.h

+1 −0
Original line number Diff line number Diff line
@@ -91,6 +91,7 @@ __kmem_cache_alias(const char *name, size_t size, size_t align, 
#define CACHE_CREATE_MASK (SLAB_CORE_FLAGS | SLAB_DEBUG_FLAGS | SLAB_CACHE_FLAGS)



int __kmem_cache_shutdown(struct kmem_cache *);

int __kmem_cache_shrink(struct kmem_cache *);

void slab_kmem_cache_release(struct kmem_cache *);



struct seq_file;

mm/slab_common.c

+33 −2
Original line number Diff line number Diff line
@@ -205,6 +205,8 @@ kmem_cache_create(const char *name, size_t size, size_t align, 
	int err;



	get_online_cpus();

	get_online_mems();



	mutex_lock(&slab_mutex);



	err = kmem_cache_sanity_check(name, size);
@@ -239,6 +241,8 @@ kmem_cache_create(const char *name, size_t size, size_t align, 


out_unlock:

	mutex_unlock(&slab_mutex);



	put_online_mems();

	put_online_cpus();



	if (err) {
@@ -272,6 +276,8 @@ void kmem_cache_create_memcg(struct mem_cgroup *memcg, struct kmem_cache *root_c 
	char *cache_name;



	get_online_cpus();

	get_online_mems();



	mutex_lock(&slab_mutex);



	/*
@@ -295,6 +301,8 @@ void kmem_cache_create_memcg(struct mem_cgroup *memcg, struct kmem_cache *root_c 


out_unlock:

	mutex_unlock(&slab_mutex);



	put_online_mems();

	put_online_cpus();

}
@@ -328,6 +336,8 @@ void slab_kmem_cache_release(struct kmem_cache *s) 
void kmem_cache_destroy(struct kmem_cache *s)

{

	get_online_cpus();

	get_online_mems();



	mutex_lock(&slab_mutex);



	s->refcount--;
@@ -359,15 +369,36 @@ void kmem_cache_destroy(struct kmem_cache *s) 
#else

	slab_kmem_cache_release(s);

#endif

	goto out_put_cpus;

	goto out;



out_unlock:

	mutex_unlock(&slab_mutex);

out_put_cpus:

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;

mm/slob.c

+1 −2
Original line number Diff line number Diff line
@@ -620,11 +620,10 @@ int __kmem_cache_shutdown(struct kmem_cache *c) 
	return 0;

}



int kmem_cache_shrink(struct kmem_cache *d)

int __kmem_cache_shrink(struct kmem_cache *d)

{

	return 0;

}

EXPORT_SYMBOL(kmem_cache_shrink);



struct kmem_cache kmem_cache_boot = {

	.name = "kmem_cache",

mm/slub.c

+2 −3
Original line number Diff line number Diff line
@@ -3398,7 +3398,7 @@ EXPORT_SYMBOL(kfree); 
 * being allocated from last increasing the chance that the last objects

 * are freed in them.

 */

int kmem_cache_shrink(struct kmem_cache *s)

int __kmem_cache_shrink(struct kmem_cache *s)

{

	int node;

	int i;
@@ -3454,7 +3454,6 @@ int kmem_cache_shrink(struct kmem_cache *s) 
	kfree(slabs_by_inuse);

	return 0;

}

EXPORT_SYMBOL(kmem_cache_shrink);



static int slab_mem_going_offline_callback(void *arg)

{
@@ -3462,7 +3461,7 @@ static int slab_mem_going_offline_callback(void *arg) 


	mutex_lock(&slab_mutex);

	list_for_each_entry(s, &slab_caches, list)

		kmem_cache_shrink(s);

		__kmem_cache_shrink(s);

	mutex_unlock(&slab_mutex);



	return 0;