dm mpath: delay the retry of a request if the target responded as busy
authorMike Snitzer <snitzer@redhat.com>
Sat, 13 Jan 2018 00:53:40 +0000 (19:53 -0500)
committerMike Snitzer <snitzer@redhat.com>
Mon, 29 Jan 2018 18:44:54 +0000 (13:44 -0500)
commitac514ffc968bf14649dd0e048447dc966ee49555
tree5f855e84e686deabbe559f2b7f4e440e5c8fd2c5
parent459b54019cfeb7330ed4863ad40f78489e0ff23d
dm mpath: delay the retry of a request if the target responded as busy

Add DM_ENDIO_DELAY_REQUEUE to allow request-based multipath's
multipath_end_io() to instruct dm-rq.c:dm_done() to delay a requeue.
This is beneficial to do if BLK_STS_RESOURCE is returned from the target
(because target is busy).

Relative to blk-mq: kick the hw queues via blk_mq_requeue_work(),
indirectly from dm-rq.c:__dm_mq_kick_requeue_list(), after a delay.

For old .request_fn: use blk_delay_queue().

bio-based multipath doesn't have feature parity with request-based for
retryable error requeues; that is something that'll need fixing in the
future.

Suggested-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Bart Van Assche <bart.vanassche@wdc.com>
[as interpreted from Bart's "... patch looks fine to me."]
drivers/md/dm-mpath.c
drivers/md/dm-rq.c
include/linux/device-mapper.h