Suppose we are creating memcg cache A that could be merged with cache B
of the same memcg. Since any memcg cache has the same parameters as its
parent cache, parent caches PA and PB of memcg caches A and B must be
mergeable too. That means PA was merged with PB on creation or vice
versa, i.e. PA = PB. From that it follows that A = B, and we couldn't
even try to create cache B, because it already exists - a contradiction.
So let's remove unused code responsible for merging memcg caches.
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
---
mm/slab.h | 21 ++++-----------------
mm/slab_common.c | 8 +++++---
mm/slub.c | 19 +++++++++----------
3 files changed, 18 insertions(+), 30 deletions(-)
diff --git a/mm/slab.h b/mm/slab.h
index 8184a7cde272..3045316b7c9d 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -55,12 +55,12 @@ extern void create_boot_cache(struct kmem_cache *, const char *name,
struct mem_cgroup;
#ifdef CONFIG_SLUB
struct kmem_cache *
-__kmem_cache_alias(struct mem_cgroup *memcg, const char *name, size_t size,
- size_t align, unsigned long flags, void (*ctor)(void *));
+__kmem_cache_alias(const char *name, size_t size, size_t align,
+ unsigned long flags, void (*ctor)(void *));
#else
static inline struct kmem_cache *
-__kmem_cache_alias(struct mem_cgroup *memcg, const char *name, size_t size,
- size_t align, unsigned long flags, void (*ctor)(void *))
+__kmem_cache_alias(const char *name, size_t size, size_t align,
+ unsigned long flags, void (*ctor)(void *))
{ return NULL; }
#endif
@@ -119,13 +119,6 @@ static inline bool is_root_cache(struct kmem_cache *s)
return !s->memcg_params || s->memcg_params->is_root_cache;
}
-static inline bool cache_match_memcg(struct kmem_cache *cachep,
- struct mem_cgroup *memcg)
-{
- return (is_root_cache(cachep) && !memcg) ||
- (cachep->memcg_params->memcg == memcg);
-}
-
static inline void memcg_bind_pages(struct kmem_cache *s, int order)
{
if (!is_root_cache(s))
@@ -204,12 +197,6 @@ static inline bool is_root_cache(struct kmem_cache *s)
return true;
}
-static inline bool cache_match_memcg(struct kmem_cache *cachep,
- struct mem_cgroup *memcg)
-{
- return true;
-}
-
static inline void memcg_bind_pages(struct kmem_cache *s, int order)
{
}
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 152d9b118b7a..a75834bb966d 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -200,9 +200,11 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
*/
flags &= CACHE_CREATE_MASK;
- s = __kmem_cache_alias(memcg, name, size, align, flags, ctor);
- if (s)
- goto out_unlock;
+ if (!memcg) {
+ s = __kmem_cache_alias(name, size, align, flags, ctor);
+ if (s)
+ goto out_unlock;
+ }
err = -ENOMEM;
s = kmem_cache_zalloc(kmem_cache, GFP_KERNEL);
diff --git a/mm/slub.c b/mm/slub.c
index 2b1a6970e46f..962abfdfde06 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3686,9 +3686,8 @@ static int slab_unmergeable(struct kmem_cache *s)
return 0;
}
-static struct kmem_cache *find_mergeable(struct mem_cgroup *memcg, size_t size,
- size_t align, unsigned long flags, const char *name,
- void (*ctor)(void *))
+static struct kmem_cache *find_mergeable(size_t size, size_t align,
+ unsigned long flags, const char *name, void (*ctor)(void *))
{
struct kmem_cache *s;
@@ -3707,11 +3706,14 @@ static struct kmem_cache *find_mergeable(struct mem_cgroup *memcg, size_t size,
if (slab_unmergeable(s))
continue;
+ if (!is_root_cache(s))
+ continue;
+
if (size > s->size)
continue;
if ((flags & SLUB_MERGE_SAME) != (s->flags & SLUB_MERGE_SAME))
- continue;
+ continue;
/*
* Check if alignment is compatible.
* Courtesy of Adrian Drzewiecki
@@ -3722,21 +3724,18 @@ static struct kmem_cache *find_mergeable(struct mem_cgroup *memcg, size_t size,
if (s->size - size >= sizeof(void *))
continue;
- if (!cache_match_memcg(s, memcg))
- continue;
-
return s;
}
return NULL;
}
struct kmem_cache *
-__kmem_cache_alias(struct mem_cgroup *memcg, const char *name, size_t size,
- size_t align, unsigned long flags, void (*ctor)(void *))
+__kmem_cache_alias(const char *name, size_t size, size_t align,
+ unsigned long flags, void (*ctor)(void *))
{
struct kmem_cache *s;
- s = find_mergeable(memcg, size, align, flags, name, ctor);
+ s = find_mergeable(size, align, flags, name, ctor);
if (s) {
s->refcount++;
/*
--
1.7.10.4
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