From: Mike Snitzer <snitzer@redhat.com>
Date: Fri, 12 Jan 2018 19:53:40 -0500
Subject: [PATCH] dm mpath: delay the retry of a request if the target
responded as busy
Git-commit: ac514ffc968bf14649dd0e048447dc966ee49555
Patch-mainline: v4.16-rc1
References: bsc#1104967,FATE#325924
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."]
Acked-by: Hannes Reinecke <hare@suse.com>
---
drivers/md/dm-mpath.c | 5 ++++-
drivers/md/dm-rq.c | 4 ++++
include/linux/device-mapper.h | 3 ++-
3 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 815de2b091a5..a8b1ffc0cb3d 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1585,7 +1585,10 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone,
if (error && blk_path_error(error)) {
struct multipath *m = ti->private;
- r = DM_ENDIO_REQUEUE;
+ if (error == BLK_STS_RESOURCE)
+ r = DM_ENDIO_DELAY_REQUEUE;
+ else
+ r = DM_ENDIO_REQUEUE;
if (pgpath)
fail_path(pgpath);
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 9d32f25489c2..b78ff6921cfb 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -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();
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 9ba84532947d..da83f64952e7 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -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)( \
--
2.16.4