[PATCH] blk: start bypass mode in blk_unregister_queue

[Aaron Lu <aaron.lu@intel.com>]

In blk_register_queue, we will end bypass mode for the queue; but in
blk_unregister_queue, we didn't start bypass mode for it. This would
cause the WARN_ON_ONCE(q->bypass_depth < 0) to trigger if the queue gets
registered, unregistered and then again registered, e.g. unload scsi
cdrom module driver sr_mod and then reload it will trigger such a
warning.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
---
 block/blk-sysfs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 6206a93..bd322a1 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -615,4 +615,6 @@ void blk_unregister_queue(struct gendisk *disk)
 	kobject_del(&q->kobj);
 	blk_trace_remove_sysfs(disk_to_dev(disk));
 	kobject_put(&disk_to_dev(disk)->kobj);
+
+	blk_queue_bypass_start(q);
 }
-- 
1.8.1.5