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

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Date:	Fri, 26 Sep 2014 11:43:44 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Liu Bo <bo.li.liu@...cle.com>,
	Chris Mason <clm@...com>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 013/142] Btrfs: fix crash on endio of reading corrupted block

From: Liu Bo <bo.li.liu@...cle.com>

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
BUG_ON.

Reported-by: Chris Murphy <lists@...orremedies.com>
Signed-off-by: Liu Bo <bo.li.liu@...cle.com>
Signed-off-by: Chris Mason <clm@...com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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;
 				continue;
 			}
 		}
-- 
2.1.0

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