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 <snitzer@xxxxxxxxxx>
---
drivers/md/dm-rq.c | 35 ++++++++++++++++++++---------------
include/linux/device-mapper.h | 1 +
2 files changed, 21 insertions(+), 15 deletions(-)
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 0d301d5..1722220 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -336,21 +336,23 @@ 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);
spin_unlock_irqrestore(q->queue_lock, flags);
}
-static void dm_requeue_original_request(struct mapped_device *md,
- struct request *rq)
+static void dm_requeue_original_request(struct dm_rq_target_io *tio, bool delay_requeue)
{
+ struct mapped_device *md = tio->md;
+ struct request *rq = tio->orig;
int rw = rq_data_dir(rq);
rq_end_stats(md, rq);
@@ -359,7 +361,7 @@ 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 +391,7 @@ 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, false);
else {
DMWARN("unimplemented target endio return value: %d", r);
BUG();
@@ -629,8 +631,8 @@ 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 +645,8 @@ 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 +654,8 @@ 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 +674,10 @@ 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(tio, true);
break;
default:
if (r > 0) {
@@ -681,10 +687,9 @@ 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 +732,7 @@ 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(tio, 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)
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