md: make sure MD_RECOVERY_DONE is clear before starting recovery/resync

MD_RECOVERY_DONE is normally cleared by md_check_recovery after a
resync etc finished.  However it is possible for raid5_start_reshape
to race and start a reshape before MD_RECOVERY_DONE is cleared.  This
can lean to multiple reshapes running at the same time, which isn't
good.

To make sure it is cleared before starting a reshape, and also clear
it when reaping a thread, just to be safe.
Signed-off-by: NeilBrown  <neilb@suse.de>

drivers/md/md.c

@@ -8262,6 +8262,7 @@ void md_reap_sync_thread(struct mddev *mddev)
 	if (mddev_is_clustered(mddev))
 		md_cluster_ops->metadata_update_finish(mddev);
 	clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
+	clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
 	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
 	clear_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
 	clear_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);

drivers/md/raid10.c

@@ -4156,6 +4156,7 @@ static int raid10_start_reshape(struct mddev *mddev)
 
 	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
 	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
+	clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
 	set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
 	set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
 

drivers/md/raid5.c

@@ -7354,6 +7354,7 @@ static int raid5_start_reshape(struct mddev *mddev)
 
 	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
 	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
+	clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
 	set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
 	set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
 	mddev->sync_thread = md_register_thread(md_do_sync, mddev,