block: avoid repeated work in blk_mark_disk_dead

Check if GD_DEAD is already set in blk_mark_disk_dead, and don't
duplicate the work already done.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Christian Brauner <brauner@kernel.org>
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Link: https://lore.kernel.org/r/20230601094459.1350643-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -575,7 +575,9 @@ void blk_mark_disk_dead(struct gendisk *disk)
 	/*
 	 * Fail any new I/O.
 	 */
-	set_bit(GD_DEAD, &disk->state);
+	if (test_and_set_bit(GD_DEAD, &disk->state))
+		return;
+
 	if (test_bit(GD_OWNS_QUEUE, &disk->state))
 		blk_queue_flag_set(QUEUE_FLAG_DYING, disk->queue);