md: replace invalid function flush_rdev_wq() with flush_workqueue()

hulk inclusion
category: bugfix
bugzilla: 188553, https://gitee.com/openeuler/kernel/issues/I6TNFX
CVE: NA

--------------------------------

If we want to remove a device, first we delete it from mddev->disks list,
then init rdev->del_work to put it (see unbind_rdev_from_array()).

flush_rdev_wq() traverses mddev->disks to check if there is any pending
rdev->del_work, if so, flush it. Howerver, rdev will not be in the list of
mddev->disks if rdev->del_work exists, and flush_workqueue() will never be
executed.

Replace it with flush_workqueue() to ensure del_work has been completed
when adding devices.

Fixes: cc1ffe61 ("md: add new workqueue for delete rdev")
Signed-off-by: NLi Nan <linan122@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>

drivers/md/md.c

@@ -4592,20 +4592,6 @@ null_show(struct mddev *mddev, char *page)
 	return -EINVAL;
 }
 
-/* need to ensure rdev_delayed_delete() has completed */
-static void flush_rdev_wq(struct mddev *mddev)
-{
-	struct md_rdev *rdev;
-
-	rcu_read_lock();
-	rdev_for_each_rcu(rdev, mddev)
-		if (work_pending(&rdev->del_work)) {
-			flush_workqueue(md_rdev_misc_wq);
-			break;
-		}
-	rcu_read_unlock();
-}
-
 static ssize_t
 new_dev_store(struct mddev *mddev, const char *buf, size_t len)
 {
@@ -4633,7 +4619,7 @@ new_dev_store(struct mddev *mddev, const char *buf, size_t len)
 	    minor != MINOR(dev))
 		return -EOVERFLOW;
 
-	flush_rdev_wq(mddev);
+	flush_workqueue(md_rdev_misc_wq);
 	err = mddev_lock(mddev);
 	if (err)
 		return err;
@@ -7647,7 +7633,7 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
 	}
 
 	if (cmd == ADD_NEW_DISK || cmd == HOT_ADD_DISK)
-		flush_rdev_wq(mddev);
+		flush_workqueue(md_rdev_misc_wq);
 
 	if (cmd == HOT_REMOVE_DISK)
 		/* need to ensure recovery thread has run */