md: stop using for_each_mddev in md_exit

Just do a simple list_for_each_entry_safe on all_mddevs, and only grab a
reference when we drop the lock and delete the now unused for_each_mddev
macro.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/md.c

@@ -368,28 +368,6 @@ EXPORT_SYMBOL_GPL(md_new_event);
 static LIST_HEAD(all_mddevs);
 static DEFINE_SPINLOCK(all_mddevs_lock);
 
-/*
- * iterates through all used mddevs in the system.
- * We take care to grab the all_mddevs_lock whenever navigating
- * the list, and to always hold a refcount when unlocked.
- * Any code which breaks out of this loop while own
- * a reference to the current mddev and must mddev_put it.
- */
-#define for_each_mddev(_mddev,_tmp)					\
-									\
-	for (({ spin_lock(&all_mddevs_lock);				\
-		_tmp = all_mddevs.next;					\
-		_mddev = NULL;});					\
-	     ({ if (_tmp != &all_mddevs)				\
-			mddev_get(list_entry(_tmp, struct mddev, all_mddevs));\
-		spin_unlock(&all_mddevs_lock);				\
-		if (_mddev) mddev_put(_mddev);				\
-		_mddev = list_entry(_tmp, struct mddev, all_mddevs);	\
-		_tmp != &all_mddevs;});					\
-	     ({ spin_lock(&all_mddevs_lock);				\
-		_tmp = _tmp->next;})					\
-		)
-
 /* Rather than calling directly into the personality make_request function,
  * IO requests come here first so that we can check if the device is
  * being suspended pending a reconfiguration.
@@ -9923,8 +9901,7 @@ void md_autostart_arrays(int part)
 
 static __exit void md_exit(void)
 {
-	struct mddev *mddev;
-	struct list_head *tmp;
+	struct mddev *mddev, *n;
 	int delay = 1;
 
 	unregister_blkdev(MD_MAJOR,"md");
@@ -9944,17 +9921,23 @@ static __exit void md_exit(void)
 	}
 	remove_proc_entry("mdstat", NULL);
 
-	for_each_mddev(mddev, tmp) {
+	spin_lock(&all_mddevs_lock);
+	list_for_each_entry_safe(mddev, n, &all_mddevs, all_mddevs) {
+		mddev_get(mddev);
+		spin_unlock(&all_mddevs_lock);
 		export_array(mddev);
 		mddev->ctime = 0;
 		mddev->hold_active = 0;
 		/*
-		 * for_each_mddev() will call mddev_put() at the end of each
-		 * iteration.  As the mddev is now fully clear, this will
-		 * schedule the mddev for destruction by a workqueue, and the
+		 * As the mddev is now fully clear, mddev_put will schedule
+		 * the mddev for destruction by a workqueue, and the
 		 * destroy_workqueue() below will wait for that to complete.
 		 */
+		mddev_put(mddev);
+		spin_lock(&all_mddevs_lock);
 	}
+	spin_unlock(&all_mddevs_lock);
+
 	destroy_workqueue(md_rdev_misc_wq);
 	destroy_workqueue(md_misc_wq);
 	destroy_workqueue(md_wq);