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| author | Ming Lei <ming.lei@redhat.com> | 2019-07-25 05:04:59 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-10-05 14:10:03 +0300 |
| commit | 4ec3ca2770e7ddb3424c43d03cec93006eb50f7a (patch) | |
| tree | 73e80e787053cfd944e99323bb6f6050d2ca1998 /drivers/md | |
| parent | 4848fb93243e0b8628ffcb5a3e3d097f8bcf314d (diff) | |
| download | linux-4ec3ca2770e7ddb3424c43d03cec93006eb50f7a.tar.xz | |
blk-mq: add callback of .cleanup_rq
[ Upstream commit 226b4fc75c78f9c497c5182d939101b260cfb9f3 ]
SCSI maintains its own driver private data hooked off of each SCSI
request, and the pridate data won't be freed after scsi_queue_rq()
returns BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE. An upper layer driver
(e.g. dm-rq) may need to retry these SCSI requests, before SCSI has
fully dispatched them, due to a lower level SCSI driver's resource
limitation identified in scsi_queue_rq(). Currently SCSI's per-request
private data is leaked when the upper layer driver (dm-rq) frees and
then retries these requests in response to BLK_STS_RESOURCE or
BLK_STS_DEV_RESOURCE returns from scsi_queue_rq().
This usecase is so specialized that it doesn't warrant training an
existing blk-mq interface (e.g. blk_mq_free_request) to allow SCSI to
account for freeing its driver private data -- doing so would add an
extra branch for handling a special case that all other consumers of
SCSI (and blk-mq) won't ever need to worry about.
So the most pragmatic way forward is to delegate freeing SCSI driver
private data to the upper layer driver (dm-rq). Do so by adding
new .cleanup_rq callback and calling a new blk_mq_cleanup_rq() method
from dm-rq. A following commit will implement the .cleanup_rq() hook
in scsi_mq_ops.
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: dm-devel@redhat.com
Cc: <stable@vger.kernel.org>
Fixes: 396eaf21ee17 ("blk-mq: improve DM's blk-mq IO merging via blk_insert_cloned_request feedback")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm-rq.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 17c6a73c536c..4d36373e1c0f 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -505,6 +505,7 @@ check_again: ret = dm_dispatch_clone_request(clone, rq); if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) { blk_rq_unprep_clone(clone); + blk_mq_cleanup_rq(clone); tio->ti->type->release_clone_rq(clone, &tio->info); tio->clone = NULL; if (!rq->q->mq_ops) |