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dm mpath: delay the retry of a request if the target responded as busy

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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."]
This commit is contained in:
Mike Snitzer 2018-01-12 19:53:40 -05:00
parent 459b54019c
commit ac514ffc96
3 changed files with 10 additions and 2 deletions
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5
drivers/md/dm-mpath.c
View File

@ -1585,7 +1585,10 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone,
if (error && !noretry_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);

4
drivers/md/dm-rq.c
View File

@ -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();

3
include/linux/device-mapper.h
View File

@ -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)( \