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authorGlauber Costa <glommer@parallels.com>2012-12-18 14:23:10 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-18 15:02:15 -0800
commitebe945c27628fca03723582eba138acc2e2f3d15 (patch)
tree5998e8dd874aedf3b8873d0ffeaf658d10505655 /mm/slab.c
parent92e793495597af4135d94314113bf13eafb0e663 (diff)
downloadop-kernel-dev-ebe945c27628fca03723582eba138acc2e2f3d15.zip
op-kernel-dev-ebe945c27628fca03723582eba138acc2e2f3d15.tar.gz
memcg: add comments clarifying aspects of cache attribute propagation
This patch clarifies two aspects of cache attribute propagation. First, the expected context for the for_each_memcg_cache macro in memcontrol.h. The usages already in the codebase are safe. In mm/slub.c, it is trivially safe because the lock is acquired right before the loop. In mm/slab.c, it is less so: the lock is acquired by an outer function a few steps back in the stack, so a VM_BUG_ON() is added to make sure it is indeed safe. A comment is also added to detail why we are returning the value of the parent cache and ignoring the children's when we propagate the attributes. Signed-off-by: Glauber Costa <glommer@parallels.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slab.c')
-rw-r--r--mm/slab.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/mm/slab.c b/mm/slab.c
index 4dcbf96..e7667a3 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4099,6 +4099,7 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
if ((ret < 0) || !is_root_cache(cachep))
return ret;
+ VM_BUG_ON(!mutex_is_locked(&slab_mutex));
for_each_memcg_cache_index(i) {
c = cache_from_memcg(cachep, i);
if (c)
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