md: restore 'noio_flag' for the last mddev_resume()

memalloc_noio_save() is called for the first mddev_suspend(), and
repeated mddev_suspend() only increase 'suspended'. However,
memalloc_noio_restore() is also called for the first mddev_resume(),
which means that memory reclaim will be enabled before the last
mddev_resume() is called, while the array is still suspended.

Fix this problem by restore 'noio_flag' for the last mddev_resume().

Fixes: 78f57ef9 ("md: use memalloc scope APIs in mddev_suspend()/mddev_resume()")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20230628012931.88911-3-yukuai1@huaweicloud.comSigned-off-by: Song Liu <song@kernel.org>

drivers/md/md.c

@@ -464,11 +464,13 @@ EXPORT_SYMBOL_GPL(mddev_suspend);
 
 void mddev_resume(struct mddev *mddev)
 {
-	/* entred the memalloc scope from mddev_suspend() */
-	memalloc_noio_restore(mddev->noio_flag);
 	lockdep_assert_held(&mddev->reconfig_mutex);
 	if (--mddev->suspended)
 		return;
+
+	/* entred the memalloc scope from mddev_suspend() */
+	memalloc_noio_restore(mddev->noio_flag);
+
 	percpu_ref_resurrect(&mddev->active_io);
 	wake_up(&mddev->sb_wait);