[5/6] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

Commit Message

Andrew Morton Dec. 18, 2019, 4:51 a.m. UTC

From: Yang Shi <[e-mail]>
Subject: mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

Since commit 0a432dcbeb32edc ("mm: shrinker: make shrinker not depend on
memcg kmem"), shrinkers' idr is protected by CONFIG_MEMCG instead of
CONFIG_MEMCG_KMEM, so it makes no sense to protect shrinker idr replace
with CONFIG_MEMCG_KMEM.

And in the CONFIG_MEMCG && CONFIG_SLOB case, shrinker_idr contains only
shrinker, and it is deferred_split_shrinker.  But it is never actually
called, since idr_replace() is never compiled due to the wrong #ifdef. 
The deferred_split_shrinker all the time is staying in half-registered
state, and it's never called for subordinate mem cgroups.

Link: http://lkml.kernel.org/r/[e-mail]
Fixes: 0a432dcbeb32 ("mm: shrinker: make shrinker not depend on memcg kmem")
Signed-off-by: Yang Shi <[e-mail]>
Reviewed-by: Kirill Tkhai <[e-mail]>
Acked-by: Michal Hocko <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: Shakeel Butt <[e-mail]>
Cc: Roman Gushchin <[e-mail]>
Cc: <[e-mail]>	[5.4+]
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/vmscan.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

--- a/mm/vmscan.c~mm-vmscan-protect-shrinker-idr-replace-with-config_memcg
+++ a/mm/vmscan.c
@@ -387,7 +387,7 @@  void register_shrinker_prepared(struct s
 {
 	down_write(&shrinker_rwsem);
 	list_add_tail(&shrinker->list, &shrinker_list);
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		idr_replace(&shrinker_idr, shrinker, shrinker->id);
 #endif