[PATCH 3.12 013/142] Btrfs: fix crash on endio of reading corrupted block

From: Jiri Slaby
Date: Fri Sep 26 2014 - 06:39:01 EST

From: Liu Bo <bo.li.liu@xxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.


commit 38c1c2e44bacb37efd68b90b3f70386a8ee370ee upstream.

The crash is

------------[ cut here ]------------
kernel BUG at fs/btrfs/extent_io.c:2124!
Workqueue: btrfs-endio normal_work_helper [btrfs]
RIP: 0010:[<ffffffffa02d6055>] [<ffffffffa02d6055>] end_bio_extent_readpage+0xb45/0xcd0 [btrfs]

This is in fact a regression.

It is because we forgot to increase @offset properly in reading corrupted block,
so that the @offset remains, and this leads to checksum errors while reading
left blocks queued up in the same bio, and then ends up with hiting the above

Reported-by: Chris Murphy <lists@xxxxxxxxxxxxxxxxx>
Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
Signed-off-by: Chris Mason <clm@xxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
fs/btrfs/extent_io.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index b395791dd923..594bbfd4996e 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2485,6 +2485,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
test_bit(BIO_UPTODATE, &bio->bi_flags);
if (err)
uptodate = 0;
+ offset += len;

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