Btrfs: fix wrong write offset when replacing a device

Miao Xie reported the following issue:

The filesystem was corrupted after we did a device replace.

Steps to reproduce:
 # mkfs.btrfs -f -m single -d raid10 <device0>..<device3>
 # mount <device0> <mnt>
 # btrfs replace start -rfB 1 <device4> <mnt>
 # umount <mnt>
 # btrfsck <device4>

The reason for the issue is that we changed the write offset by mistake,
introduced by commit 625f1c8dc.

We read the data from the source device at first, and then write the
data into the corresponding place of the new device. In order to
implement the "-r" option, the source location is remapped using
btrfs_map_block(). The read takes place on the mapped location, and
the write needs to take place on the unmapped location. Currently
the write is using the mapped location, and this commit changes it
back by undoing the change to the write address that the aforementioned
commit added by mistake.

Reported-by: Miao Xie <miaox@cn.fujitsu.com>
Cc: <stable@vger.kernel.org> # 3.10+
Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 4ba2a69a60ad4ffc327697ec4a8db3d04159d0a8..64a157becbe573f778c02e9475483cff5e167ea9 100644 (file)
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2495,7 +2495,7 @@ again:
                        ret = scrub_extent(sctx, extent_logical, extent_len,
                                           extent_physical, extent_dev, flags,
                                           generation, extent_mirror_num,
-                                          extent_physical);
+                                          extent_logical - logical + physical);
                        if (ret)
                                goto out;