block, blk-mq: draining can't be skipped even if bypass_depth was non-zero
authorTejun Heo <tj@kernel.org>
Tue, 1 Jul 2014 16:29:17 +0000 (10:29 -0600)
committerJens Axboe <axboe@fb.com>
Tue, 1 Jul 2014 16:29:17 +0000 (10:29 -0600)
commit776687bce42bb22cce48b5da950e48ebbb9a948f
tree68901461bfd070246574f1e2440ba1ef2ae93ec0
parent531ed6261e7466907418b1a9971a5c71d7d250e4
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>
block/blk-core.c
block/blk-mq.c
block/blk-sysfs.c