Commit fa1e512f authored by Yang Shi's avatar Yang Shi Committed by Linus Torvalds

mm: vmscan: check if mem cgroup is disabled or not before calling memcg slab shrinker

Shakeel Butt reported premature oom on kernel with
"cgroup_disable=memory" since mem_cgroup_is_root() returns false even
though memcg is actually NULL.  The drop_caches is also broken.

It is because commit aeed1d32 ("mm/vmscan.c: generalize
shrink_slab() calls in shrink_node()") removed the !memcg check before
!mem_cgroup_is_root().  And, surprisingly root memcg is allocated even
though memory cgroup is disabled by kernel boot parameter.

Add mem_cgroup_disabled() check to make reclaimer work as expected.

Link: http://lkml.kernel.org/r/1563385526-20805-1-git-send-email-yang.shi@linux.alibaba.com
Fixes: aeed1d32 ("mm/vmscan.c: generalize shrink_slab() calls in shrink_node()")
Signed-off-by: default avatarYang Shi <yang.shi@linux.alibaba.com>
Reported-by: default avatarShakeel Butt <shakeelb@google.com>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
Reviewed-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Jan Hadrava <had@kam.mff.cuni.cz>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: <stable@vger.kernel.org>	[4.19+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7bc36e3c
...@@ -699,7 +699,14 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, ...@@ -699,7 +699,14 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
unsigned long ret, freed = 0; unsigned long ret, freed = 0;
struct shrinker *shrinker; struct shrinker *shrinker;
if (!mem_cgroup_is_root(memcg)) /*
* The root memcg might be allocated even though memcg is disabled
* via "cgroup_disable=memory" boot parameter. This could make
* mem_cgroup_is_root() return false, then just run memcg slab
* shrink, but skip global shrink. This may result in premature
* oom.
*/
if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
return shrink_slab_memcg(gfp_mask, nid, memcg, priority); return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
if (!down_read_trylock(&shrinker_rwsem)) if (!down_read_trylock(&shrinker_rwsem))
......
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