Commit ac514ffc authored by Mike Snitzer's avatar Mike Snitzer
Browse files

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: default avatarBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Acked-by: default avatarBart Van Assche <bart.vanassche@wdc.com>
[as interpreted from Bart's "... patch looks fine to me."]
parent 459b5401

drivers/md/dm-mpath.c

+4 −1
Original line number Diff line number Diff line
@@ -1585,6 +1585,9 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone, 
	if (error && !noretry_error(error)) {

		struct multipath *m = ti->private;



		if (error == BLK_STS_RESOURCE)

			r = DM_ENDIO_DELAY_REQUEUE;

		else

			r = DM_ENDIO_REQUEUE;



		if (pgpath)

drivers/md/dm-rq.c

+4 −0
Original line number Diff line number Diff line
@@ -315,6 +315,10 @@ static void dm_done(struct request *clone, blk_status_t error, bool mapped) 
		/* The target wants to requeue the I/O */

		dm_requeue_original_request(tio, false);

		break;

	case DM_ENDIO_DELAY_REQUEUE:

		/* The target wants to requeue the I/O after a delay */

		dm_requeue_original_request(tio, true);

		break;

	default:

		DMWARN("unimplemented target endio return value: %d", r);

		BUG();

include/linux/device-mapper.h

+2 −1
Original line number Diff line number Diff line
@@ -550,6 +550,7 @@ do { \ 
#define DM_ENDIO_DONE		0

#define DM_ENDIO_INCOMPLETE	1

#define DM_ENDIO_REQUEUE	2

#define DM_ENDIO_DELAY_REQUEUE	3



/*

 * Definitions of return values from target map function.
@@ -557,7 +558,7 @@ do { \ 
#define DM_MAPIO_SUBMITTED	0

#define DM_MAPIO_REMAPPED	1

#define DM_MAPIO_REQUEUE	DM_ENDIO_REQUEUE

#define DM_MAPIO_DELAY_REQUEUE	3

#define DM_MAPIO_DELAY_REQUEUE	DM_ENDIO_DELAY_REQUEUE

#define DM_MAPIO_KILL		4



#define dm_sector_div64(x, y)( \

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