Revert "block: freeze the queue earlier in del_gendisk"

This reverts commit a09b314.

Dusty Mabe reported consistent hang during CoreOS shutdown with a MD
RAID1 setup.  Although apparently similar hangs happened before,
and this patch most likely is not the root cause it made it much
more severe.  Revert it until we can figure out what is going on
with the md driver.

Signed-off-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Christoph Hellwig

block/genhd.c

@@ -602,7 +602,6 @@ void del_gendisk(struct gendisk *disk)
 	 * Prevent new I/O from crossing bio_queue_enter().
 	 */
 	blk_queue_start_drain(q);
-	blk_mq_freeze_queue_wait(q);
 
 	if (!(disk->flags & GENHD_FL_HIDDEN)) {
 		sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
@@ -626,6 +625,8 @@ void del_gendisk(struct gendisk *disk)
 	pm_runtime_set_memalloc_noio(disk_to_dev(disk), false);
 	device_del(disk_to_dev(disk));
 
+	blk_mq_freeze_queue_wait(q);
+
 	blk_throtl_cancel_bios(disk->queue);
 
 	blk_sync_queue(q);