This is a note to let you know that I've just added the patch titled
staging: zcache: fix cleancache race condition with shrinker
to the 3.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
staging-zcache-fix-cleancache-race-condition-with-shrinker.patch
and it can be found in the queue-3.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 6d7d9798ad5c97ee4e911dd070dc12dc5ae55bd0 Mon Sep 17 00:00:00 2001
From: Seth Jennings <[email protected]>
Date: Wed, 29 Aug 2012 16:58:45 -0500
Subject: staging: zcache: fix cleancache race condition with shrinker
From: Seth Jennings <[email protected]>
commit 6d7d9798ad5c97ee4e911dd070dc12dc5ae55bd0 upstream.
This patch fixes a race condition that results in memory
corruption when using cleancache.
The race exists between the zcache shrinker handler,
shrink_zcache_memory() and cleancache_get_page().
In most cases, the shrinker will both evict a zbpg
from its buddy list and flush it from tmem before a
cleancache_get_page() occurs on that page. A subsequent
cleancache_get_page() will fail in the tmem layer.
In the rare case that two occur together and the
cleancache_get_page() path gets through the tmem
layer before the shrinker path can flush tmem,
zbud_decompress() does a check to see if the zbpg is a
"zombie", i.e. not on a buddy list, which means the shrinker
is in the process of reclaiming it. If the zbpg is a zombie,
zbud_decompress() returns -EINVAL.
However, this return code is being ignored by the caller,
zcache_pampd_get_data_and_free(), which results in the
caller of cleancache_get_page() thinking that the page has
been properly retrieved when it has not.
This patch modifies zcache_pampd_get_data_and_free() to
convey the failure up the stack so that the caller of
cleancache_get_page() knows the page retrieval failed.
This needs to be applied to stable trees as well.
zcache-main.c was named zcache.c before v3.1, so
I'm not sure how you want to handle trees earlier
than that.
Signed-off-by: Seth Jennings <[email protected]>
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/staging/zcache/zcache-main.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -1259,13 +1259,12 @@ static int zcache_pampd_get_data_and_fre
void *pampd, struct tmem_pool *pool,
struct tmem_oid *oid, uint32_t index)
{
- int ret = 0;
-
BUG_ON(!is_ephemeral(pool));
- zbud_decompress((struct page *)(data), pampd);
+ if (zbud_decompress((struct page *)(data), pampd) < 0)
+ return -EINVAL;
zbud_free_and_delist((struct zbud_hdr *)pampd);
atomic_dec(&zcache_curr_eph_pampd_count);
- return ret;
+ return 0;
}
/*
Patches currently in stable-queue which might be from
[email protected] are
queue-3.5/staging-zcache-fix-cleancache-race-condition-with-shrinker.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
