dm: requeue from blk-mq dm_mq_queue_rq() using BLK_MQ_RQ_QUEUE_BUSY
Use BLK_MQ_RQ_QUEUE_BUSY to requeue a blk-mq request directly from the
DM blk-mq device's .queue_rq. This cleans up the previous convoluted
handling of request requeueing that would return BLK_MQ_RQ_QUEUE_OK
(even though it wasn't) and then run blk_mq_requeue_request() followed
by blk_mq_kick_requeue_list().
Also, document that DM blk-mq ontop of old request_fn devices cannot
fail in clone_rq() since the clone request is preallocated as part of
the pdu.
Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 1c62ed8..1badfb2 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2754,13 +2754,15 @@
if (dm_table_get_type(map) == DM_TYPE_REQUEST_BASED) {
/* clone request is allocated at the end of the pdu */
tio->clone = (void *)blk_mq_rq_to_pdu(rq) + sizeof(struct dm_rq_target_io);
- if (!clone_rq(rq, md, tio, GFP_ATOMIC))
- return BLK_MQ_RQ_QUEUE_BUSY;
+ (void) clone_rq(rq, md, tio, GFP_ATOMIC);
queue_kthread_work(&md->kworker, &tio->work);
} else {
/* Direct call is fine since .queue_rq allows allocations */
- if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE)
- dm_requeue_unmapped_original_request(md, rq);
+ if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE) {
+ /* Undo dm_start_request() before requeuing */
+ rq_completed(md, rq_data_dir(rq), false);
+ return BLK_MQ_RQ_QUEUE_BUSY;
+ }
}
return BLK_MQ_RQ_QUEUE_OK;