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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, stable@vger.kernel.org,
        Chris Murphy <lists@colorremedies.com>, Liu Bo <bo.li.liu@oracle.com>,
        Chris Mason <clm@fb.com>
Subject: [PATCH 3.16 089/125] Btrfs: fix crash on endio of reading corrupted block
Date: Wed,  3 Sep 2014 15:07:26 -0700
Message-Id: <20140903220626.346231505@linuxfoundation.org>
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3.16-stable review patch.  If anyone has any objections, please let me know.

------------------

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

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@colorremedies.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/btrfs/extent_io.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2532,6 +2532,7 @@ static void end_bio_extent_readpage(stru
 					test_bit(BIO_UPTODATE, &bio->bi_flags);
 				if (err)
 					uptodate = 0;
+				offset += len;
 				continue;
 			}
 		}