md/raid1: don't abort a resync on the first badblock.

commit b7219ccb33aa0df9949a60c68b5e9f712615e56f upstream.

If a resync of a RAID1 array with 2 devices finds a known bad block
one device it will neither read from, or write to, that device for
this block offset.
So there will be one read_target (The other device) and zero write
targets.
This condition causes md/raid1 to abort the resync assuming that it
has finished - without known bad blocks this would be true.

When there are no write targets because of the presence of bad blocks
we should only skip over the area covered by the bad block.
RAID10 already gets this right, raid1 doesn't.  Or didn't.

As this can cause a 'sync' to abort early and appear to have succeeded
it could lead to some data corruption, so it suitable for -stable.

Reported-by: Alexander Lyakas <alex.bolshoy@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index d7add9d5bac203aa4fecdf2ea99c1cf6c5716bbe..23904d233735240bc5f3fe3465a85fe4c0c2b22e 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2429,7 +2429,10 @@ static sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int *skipp
                /* There is nowhere to write, so all non-sync
                 * drives must be failed - so we are finished
                 */
-               sector_t rv = max_sector - sector_nr;
+               sector_t rv;
+               if (min_bad > 0)
+                       max_sector = sector_nr + min_bad;
+               rv = max_sector - sector_nr;
                *skipped = 1;
                put_buf(r1_bio);
                return rv;