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authorMing Lei <ming.lei@redhat.com>2019-07-25 10:04:59 +0800
committerJens Axboe <axboe@kernel.dk>2019-08-04 21:42:06 -0600
commit226b4fc75c78f9c497c5182d939101b260cfb9f3 (patch)
tree2ae8ba0317c5214237ce32b767c46dc4fa5eafbf /drivers/md/dm-rq.c
parenta61dbfb12bc6dadce91600fe3409a3675751c716 (diff)
downloadlinux-226b4fc75c78f9c497c5182d939101b260cfb9f3.tar.bz2
blk-mq: add callback of .cleanup_rq
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>
Diffstat (limited to 'drivers/md/dm-rq.c')
-rw-r--r--drivers/md/dm-rq.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index c9e44ac1f9a6..21d5c1784d0c 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -408,6 +408,7 @@ static int map_request(struct dm_rq_target_io *tio)
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;
return DM_MAPIO_REQUEUE;