block, blk-mq: draining can't be skipped even if bypass_depth was non-zero

Currently, both blk_queue_bypass_start() and blk_mq_freeze_queue()
skip queue draining if bypass_depth was already above zero.  The
assumption is that the one which bumped the bypass_depth should have
performed draining already; however, there's nothing which prevents a
new instance of bypassing/freezing from starting before the previous
one finishes draining.  The current code may allow the later
bypassing/freezing instances to complete while there still are
in-flight requests which haven't finished draining.

Fix it by draining regardless of bypass_depth.  We still skip draining
from blk_queue_bypass_start() while the queue is initializing to avoid
introducing excessive delays during boot.  INIT_DONE setting is moved
above the initial blk_queue_bypass_end() so that bypassing attempts
can't slip inbetween.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 23321fbab293..4db5abf96b9e 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -554,8 +554,8 @@ int blk_register_queue(struct gendisk *disk)
 	 * Initialization must be complete by now.  Finish the initial
 	 * bypass from queue allocation.
 	 */
-	blk_queue_bypass_end(q);
 	queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q);
+	blk_queue_bypass_end(q);
 
 	ret = blk_trace_init_sysfs(dev);
 	if (ret)