Eric Lee / smarc-ti-linux-kernel

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Commit 49e7e7ff8d551b5b1e2f8da8497b9058cfa25672

Authored by Vladimir Davydov
Committed by Linus Torvalds
1 parent 2acb60a046
Exists in ti-lsk-linux-4.1.y and in 10 other branches dlt-processor-sdk-linux-03.00.00.04, processor-sdk-linux-02.00.01, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04

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>

Showing 1 changed file with 6 additions and 3 deletions Side-by-side Diff

... ... @@ -91,14 +91,17 @@
91 91 /*
92 92 * prune the dcache first as the icache is pinned by it, then
93 93 * prune the icache, followed by the filesystem specific caches
  94 + *
  95 + * Ensure that we always scan at least one object - memcg kmem
  96 + * accounting uses this to fully empty the caches.
94 97 */
95   - sc->nr_to_scan = dentries;
  98 + sc->nr_to_scan = dentries + 1;
96 99 freed = prune_dcache_sb(sb, sc);
97   - sc->nr_to_scan = inodes;
  100 + sc->nr_to_scan = inodes + 1;
98 101 freed += prune_icache_sb(sb, sc);
99 102  
100 103 if (fs_objects) {
101   - sc->nr_to_scan = fs_objects;
  104 + sc->nr_to_scan = fs_objects + 1;
102 105 freed += sb->s_op->free_cached_objects(sb, sc);
103 106 }
104 107