fs: shrinker: always scan at least one object of each type
authorVladimir Davydov <vdavydov@parallels.com>
Thu, 12 Feb 2015 22:59:17 +0000 (14:59 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 13 Feb 2015 02:54:09 +0000 (18:54 -0800)
commit49e7e7ff8d551b5b1e2f8da8497b9058cfa25672
treeaa671bba976ba7bc0837785a49d5d83c5fc99c98
parent2acb60a0461fec8a4516686c913a295ce872697f
fs: shrinker: always scan at least one object of each type

In super_cache_scan() we divide the number of objects of particular type
by the total number of objects in order to distribute pressure among As a
result, in some corner cases we can get nr_to_scan=0 even if there are
some objects to reclaim, e.g.  dentries=1, inodes=1, fs_objects=1,
nr_to_scan=1/3=0.

This is unacceptable for per memcg kmem accounting, because this means
that some objects may never get reclaimed after memcg death, preventing it
from being freed.

This patch therefore assures that super_cache_scan() will scan at least
one object of each type if any.

[akpm@linux-foundation.org: add comment]
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/super.c