mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG

commit 42a9a53bb394a1de2247ef78f0b802ae86798122 upstream.

Since commit 0a432dcbeb32 ("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/1575486978-45249-1-git-send-email-yang.shi@linux.alibaba.com
Fixes: 0a432dcbeb32 ("mm: shrinker: make shrinker not depend on memcg kmem")
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: <stable@vger.kernel.org>	[5.4+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ee4eecc7e1c2177041d00d8eb8d62ca64647206a..e7f10c4b40f0776d461e8d4b3def905ca132a2be 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
 {
        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