[53/91] UBIFS: fix shrinker object count reports

From: Greg KH
Date: Thu Jun 16 2011 - 03:06:15 EST

2.6.32-longterm review patch. If anyone has any objections, please let us know.


From: Artem Bityutskiy <Artem.Bityutskiy@xxxxxxxxx>

commit cf610bf4199770420629d3bc273494bd27ad6c1d upstream.

Sometimes VM asks the shrinker to return amount of objects it can shrink,
and we return the ubifs_clean_zn_cnt in that case. However, it is possible
that this counter is negative for a short period of time, due to the way
UBIFS TNC code updates it. And I can observe the following warnings sometimes:

shrink_slab: ubifs_shrinker+0x0/0x2b7 [ubifs] negative objects to delete nr=-8541616642706119788

This patch makes sure UBIFS never returns negative count of objects.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

fs/ubifs/shrinker.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/ubifs/shrinker.c
+++ b/fs/ubifs/shrinker.c
@@ -283,7 +283,11 @@ int ubifs_shrinker(int nr, gfp_t gfp_mas
long clean_zn_cnt = atomic_long_read(&ubifs_clean_zn_cnt);

if (nr == 0)
- return clean_zn_cnt;
+ /*
+ * Due to the way UBIFS updates the clean znode counter it may
+ * temporarily be negative.
+ */
+ return clean_zn_cnt >= 0 ? clean_zn_cnt : 1;

if (!clean_zn_cnt) {

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