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authorAndrea Righi <andrea.righi@canonical.com>2019-03-14 08:56:28 +0100
committerDavid Sterba <dsterba@suse.com>2019-03-18 19:47:36 +0100
commit3897b6f0a859288c22fb793fad11ec2327e60fcd (patch)
treed34a7d81bd112d7d772dd0555193915e1a3082eb
parent0cc068e6ee59c1fffbfa977d8bf868b7551d80ac (diff)
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btrfs: raid56: properly unmap parity page in finish_parity_scrub()
Parity page is incorrectly unmapped in finish_parity_scrub(), triggering a reference counter bug on i386, i.e.: [ 157.662401] kernel BUG at mm/highmem.c:349! [ 157.666725] invalid opcode: 0000 [#1] SMP PTI The reason is that kunmap(p_page) was completely left out, so we never did an unmap for the p_page and the loop unmapping the rbio page was iterating over the wrong number of stripes: unmapping should be done with nr_data instead of rbio->real_stripes. Test case to reproduce the bug: - create a raid5 btrfs filesystem: # mkfs.btrfs -m raid5 -d raid5 /dev/sdb /dev/sdc /dev/sdd /dev/sde - mount it: # mount /dev/sdb /mnt - run btrfs scrub in a loop: # while :; do btrfs scrub start -BR /mnt; done BugLink: https://bugs.launchpad.net/bugs/1812845 Fixes: 5a6ac9eacb49 ("Btrfs, raid56: support parity scrub on raid56") CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Andrea Righi <andrea.righi@canonical.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
-rw-r--r--fs/btrfs/raid56.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index e74455eb42f9..6976e2280771 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -2429,8 +2429,9 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio,
bitmap_clear(rbio->dbitmap, pagenr, 1);
kunmap(p);
- for (stripe = 0; stripe < rbio->real_stripes; stripe++)
+ for (stripe = 0; stripe < nr_data; stripe++)
kunmap(page_in_rbio(rbio, stripe, pagenr, 0));
+ kunmap(p_page);
}
__free_page(p_page);