md/raid1,raid10: don't broken array on failfast metadata write fails

It is not intended for the array to fail when a metadata write with
MD_FAILFAST fails.
After commit 9631abd ("md: Set MD_BROKEN for RAID1 and RAID10"),
when md_error is called on the last device in RAID1/10,
the MD_BROKEN flag is set on the array.
Because of this, a failfast metadata write failure will
make the array "broken" state.

If rdev is not Faulty even after calling md_error,
the rdev is the last device, and there is nothing except
MD_BROKEN that prevents writes to the array.
Therefore, by clearing MD_BROKEN, the array will not become
"broken" after a failfast metadata write failure.

Fixes: 9631abd ("md: Set MD_BROKEN for RAID1 and RAID10")
Signed-off-by: Kenta Akagi <[email protected]>

Author: mgmlme

drivers/md/md.c

@@ -989,6 +989,7 @@ static void super_written(struct bio *bio)
 		md_error(mddev, rdev);
 		if (!test_bit(Faulty, &rdev->flags)
 		    && (bio->bi_opf & MD_FAILFAST)) {
+			clear_bit(MD_BROKEN, &mddev->flags);
 			set_bit(MD_SB_NEED_REWRITE, &mddev->sb_flags);
 			set_bit(LastDev, &rdev->flags);
 		}

drivers/md/md.h

@@ -332,7 +332,7 @@ struct md_cluster_operations;
  *			       resync lock, need to release the lock.
  * @MD_FAILFAST_SUPPORTED: Using MD_FAILFAST on metadata writes is supported as
  *			    calls to md_error() will never cause the array to
- *			    become failed.
+ *			    become failed while fail_last_dev is not set.
  * @MD_HAS_PPL:  The raid array has PPL feature set.
  * @MD_HAS_MULTIPLE_PPLS: The raid array has multiple PPLs feature set.
  * @MD_NOT_READY: do_md_run() is active, so 'array_state', ust not report that