md: use separate work_struct for md_start_sync()

It's a little weird to borrow 'del_work' for md_start_sync(), declare
a new work_struct 'sync_work' for md_start_sync().
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230825031622.1530464-2-yukuai1@huaweicloud.com

drivers/md/md.c

@@ -631,13 +631,13 @@ void mddev_put(struct mddev *mddev)
 		 * flush_workqueue() after mddev_find will succeed in waiting
 		 * for the work to be done.
 		 */
-		INIT_WORK(&mddev->del_work, mddev_delayed_delete);
 		queue_work(md_misc_wq, &mddev->del_work);
 	}
 	spin_unlock(&all_mddevs_lock);
 }
 
 static void md_safemode_timeout(struct timer_list *t);
+static void md_start_sync(struct work_struct *ws);
 
 void mddev_init(struct mddev *mddev)
 {
@@ -662,6 +662,9 @@ void mddev_init(struct mddev *mddev)
 	mddev->resync_min = 0;
 	mddev->resync_max = MaxSector;
 	mddev->level = LEVEL_NONE;
+
+	INIT_WORK(&mddev->sync_work, md_start_sync);
+	INIT_WORK(&mddev->del_work, mddev_delayed_delete);
 }
 EXPORT_SYMBOL_GPL(mddev_init);
 
@@ -9256,7 +9259,7 @@ static int remove_and_add_spares(struct mddev *mddev,
 
 static void md_start_sync(struct work_struct *ws)
 {
-	struct mddev *mddev = container_of(ws, struct mddev, del_work);
+	struct mddev *mddev = container_of(ws, struct mddev, sync_work);
 
 	rcu_assign_pointer(mddev->sync_thread,
 			   md_register_thread(md_do_sync, mddev, "resync"));
@@ -9469,8 +9472,7 @@ void md_check_recovery(struct mddev *mddev)
 				 */
 				md_bitmap_write_all(mddev->bitmap);
 			}
-			INIT_WORK(&mddev->del_work, md_start_sync);
-			queue_work(md_misc_wq, &mddev->del_work);
+			queue_work(md_misc_wq, &mddev->sync_work);
 			goto unlock;
 		}
 	not_running:

drivers/md/md.h

@@ -453,7 +453,10 @@ struct mddev {
 	struct kernfs_node		*sysfs_degraded;	/*handle for 'degraded' */
 	struct kernfs_node		*sysfs_level;		/*handle for 'level' */
 
-	struct work_struct del_work;	/* used for delayed sysfs removal */
+	/* used for delayed sysfs removal */
+	struct work_struct del_work;
+	/* used for register new sync thread */
+	struct work_struct sync_work;
 
 	/* "lock" protects:
 	 *   flush_bio transition from NULL to !NULL