Otherwise blk-mq will immediately dispatch requests that are requeued via a BLK_MQ_RQ_QUEUE_BUSY return from blk_mq_ops .queue_rq.
Delayed requeue is implemented using blk_mq_delay_kick_requeue_list() with a delay of 5 secs. In the context of DM multipath (all paths down) it doesn't make any sense to requeue more quickly. Signed-off-by: Mike Snitzer <snit...@redhat.com> --- drivers/md/dm-rq.c | 32 ++++++++++++++++++-------------- include/linux/device-mapper.h | 1 + 2 files changed, 19 insertions(+), 14 deletions(-) diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 0d301d5..9eebc8d 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -336,20 +336,21 @@ static void dm_old_requeue_request(struct request *rq) spin_unlock_irqrestore(q->queue_lock, flags); } -static void dm_mq_requeue_request(struct request *rq) +static void dm_mq_delay_requeue_request(struct request *rq, unsigned long msecs) { struct request_queue *q = rq->q; unsigned long flags; blk_mq_requeue_request(rq); + spin_lock_irqsave(q->queue_lock, flags); if (!blk_queue_stopped(q)) - blk_mq_kick_requeue_list(q); + blk_mq_delay_kick_requeue_list(q, msecs_to_jiffies(msecs)); spin_unlock_irqrestore(q->queue_lock, flags); } static void dm_requeue_original_request(struct mapped_device *md, - struct request *rq) + struct request *rq, bool delay_requeue) { int rw = rq_data_dir(rq); @@ -359,7 +360,7 @@ static void dm_requeue_original_request(struct mapped_device *md, if (!rq->q->mq_ops) dm_old_requeue_request(rq); else - dm_mq_requeue_request(rq); + dm_mq_delay_requeue_request(rq, delay_requeue ? 5000 : 0); rq_completed(md, rw, false); } @@ -389,7 +390,7 @@ static void dm_done(struct request *clone, int error, bool mapped) return; else if (r == DM_ENDIO_REQUEUE) /* The target wants to requeue the I/O */ - dm_requeue_original_request(tio->md, tio->orig); + dm_requeue_original_request(tio->md, tio->orig, false); else { DMWARN("unimplemented target endio return value: %d", r); BUG(); @@ -629,8 +630,8 @@ static int dm_old_prep_fn(struct request_queue *q, struct request *rq) /* * Returns: - * 0 : the request has been processed - * DM_MAPIO_REQUEUE : the original request needs to be requeued + * DM_MAPIO_* : the request has been processed as indicated + * DM_MAPIO_REQUEUE : the original request needs to be immediately requeued * < 0 : the request was completed due to failure */ static int map_request(struct dm_rq_target_io *tio, struct request *rq, @@ -643,6 +644,8 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq, if (tio->clone) { clone = tio->clone; r = ti->type->map_rq(ti, clone, &tio->info); + if (r == DM_MAPIO_DELAY_REQUEUE) + return DM_MAPIO_REQUEUE; /* .request_fn requeue is always immediate */ } else { r = ti->type->clone_and_map_rq(ti, rq, &tio->info, &clone); if (r < 0) { @@ -650,9 +653,8 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq, dm_kill_unmapped_request(rq, r); return r; } - if (r != DM_MAPIO_REMAPPED) - return r; - if (setup_clone(clone, rq, tio, GFP_ATOMIC)) { + if (r == DM_MAPIO_REMAPPED && + setup_clone(clone, rq, tio, GFP_ATOMIC)) { /* -ENOMEM */ ti->type->release_clone_rq(clone); return DM_MAPIO_REQUEUE; @@ -671,7 +673,10 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq, break; case DM_MAPIO_REQUEUE: /* The target wants to requeue the I/O */ - dm_requeue_original_request(md, tio->orig); + break; + case DM_MAPIO_DELAY_REQUEUE: + /* The target wants to requeue the I/O after a delay */ + dm_requeue_original_request(md, tio->orig, true); break; default: if (r > 0) { @@ -681,10 +686,9 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq, /* The target wants to complete the I/O */ dm_kill_unmapped_request(rq, r); - return r; } - return 0; + return r; } static void dm_start_request(struct mapped_device *md, struct request *orig) @@ -727,7 +731,7 @@ static void map_tio_request(struct kthread_work *work) struct mapped_device *md = tio->md; if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE) - dm_requeue_original_request(md, rq); + dm_requeue_original_request(md, rq, false); } ssize_t dm_attr_rq_based_seq_io_merge_deadline_show(struct mapped_device *md, char *buf) diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 91acfce..ef7962e 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -590,6 +590,7 @@ extern struct ratelimit_state dm_ratelimit_state; #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_sector_div64(x, y)( \ { \ -- 2.7.4 (Apple Git-66) -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html