btrfs: Put mirror_num in bi_bdev

The error correction code wants to make sure that only the bad mirror is
rewritten. Thus, we need to know which mirror is the bad one. I did not
find a more apropriate field than bi_bdev. But I think using this is fine,
because it is modified by the block layer, anyway, and should not be read
after the bio returned.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9db4d7962f9b..18baac5a3f6c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3216,6 +3216,8 @@ static void btrfs_end_bio(struct bio *bio, int err)
                 }
                 bio->bi_private = bbio->private;
                 bio->bi_end_io = bbio->end_io;
+                bio->bi_bdev = (struct block_device *)
+                                        (unsigned long)bbio->mirror_num;
                 /* only send an error to the higher layers if it is
                  * beyond the tolerance of the multi-bio
                  */