md: don't leave 'MD_RECOVERY_FROZEN' in error path of md_set_readonly()

If md_set_readonly() failed, the array could still be read-write, however
'MD_RECOVERY_FROZEN' could still be set, which leave the array in an
abnormal state that sync or recovery can't continue anymore.
Hence make sure the flag is cleared after md_set_readonly() returns.

Fixes: 88724bfa ("md: wait for pending superblock updates before switching to read-only")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231205094215.1824240-3-yukuai1@huaweicloud.com

drivers/md/md.c

@@ -6355,6 +6355,9 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
 	int err = 0;
 	int did_freeze = 0;
 
+	if (mddev->external && test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags))
+		return -EBUSY;
+
 	if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)) {
 		did_freeze = 1;
 		set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
@@ -6369,8 +6372,6 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
 	 */
 	md_wakeup_thread_directly(mddev->sync_thread);
 
-	if (mddev->external && test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags))
-		return -EBUSY;
 	mddev_unlock(mddev);
 	wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
 					  &mddev->recovery));
@@ -6383,29 +6384,30 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
 	    mddev->sync_thread ||
 	    test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
 		pr_warn("md: %s still in use.\n",mdname(mddev));
-		if (did_freeze) {
-			clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
-			set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
-			md_wakeup_thread(mddev->thread);
-		}
 		err = -EBUSY;
 		goto out;
 	}
+
 	if (mddev->pers) {
 		__md_stop_writes(mddev);
 
+		if (mddev->ro == MD_RDONLY) {
 			err  = -ENXIO;
-		if (mddev->ro == MD_RDONLY)
 			goto out;
+		}
+
 		mddev->ro = MD_RDONLY;
 		set_disk_ro(mddev->gendisk, 1);
+	}
+
+out:
+	if ((mddev->pers && !err) || did_freeze) {
 		clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 		md_wakeup_thread(mddev->thread);
 		sysfs_notify_dirent_safe(mddev->sysfs_state);
-		err = 0;
 	}
-out:
+
 	mutex_unlock(&mddev->open_mutex);
 	return err;
 }