The patch titled
Subject: dm bufio: fully initialize shrinker
has been added to the -mm tree. Its filename is
dm-bufio-fully-initialize-shrinker.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/dm-bufio-fully-initialize-shrinker.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/dm-bufio-fully-initialize-shrinker.patch
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------------------------------------------------------
From: Greg Thelen <gthelen@xxxxxxxxxx>
Subject: dm bufio: fully initialize shrinker
1d3d4437eae1 ("vmscan: per-node deferred work") added a flags field to
struct shrinker assuming that all shrinkers were zero filled. The dm
bufio shrinker is not zero filled, which leaves arbitrary kmalloc() data
in flags. So far the only defined flags bit is SHRINKER_NUMA_AWARE.
But there are proposed patches which add other bits to shrinker.flags
(e.g. memcg awareness).
Rather than simply initializing the shrinker, this patch uses kzalloc()
when allocating the dm_bufio_client to ensure that the embedded shrinker
and any other similar structures are zeroed.
This fixes theoretical over aggressive shrinking of dm bufio objects.
If the uninitialized dm_bufio_client.shrinker.flags contains
SHRINKER_NUMA_AWARE then shrink_slab() would call the dm shrinker for
each numa node rather than just once. This has been broken since 3.12.
Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Alasdair Kergon <agk@xxxxxxxxxx>
Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: Neil Brown <neilb@xxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.12+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-bufio.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN drivers/md/dm-bufio.c~dm-bufio-fully-initialize-shrinker drivers/md/dm-bufio.c
--- a/drivers/md/dm-bufio.c~dm-bufio-fully-initialize-shrinker
+++ a/drivers/md/dm-bufio.c
@@ -1541,7 +1541,7 @@ struct dm_bufio_client *dm_bufio_client_
BUG_ON(block_size < 1 << SECTOR_SHIFT ||
(block_size & (block_size - 1)));
- c = kmalloc(sizeof(*c), GFP_KERNEL);
+ c = kzalloc(sizeof(*c), GFP_KERNEL);
if (!c) {
r = -ENOMEM;
goto bad_client;
_
Patches currently in -mm which might be from gthelen@xxxxxxxxxx are
dm-bufio-fully-initialize-shrinker.patch
memcg-remove-lookup_cgroup_page-prototype.patch
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