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Message-Id: <20170930114652.32441-5-ming.lei@redhat.com>
Date: Sat, 30 Sep 2017 19:46:51 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Jens Axboe <axboe@...com>, linux-block@...r.kernel.org,
Christoph Hellwig <hch@...radead.org>,
Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com
Cc: Bart Van Assche <bart.vanassche@...disk.com>,
Laurence Oberman <loberman@...hat.com>,
linux-kernel@...r.kernel.org, Omar Sandoval <osandov@...com>,
Ming Lei <ming.lei@...hat.com>
Subject: [PATCH 4/5] dm-mpath: cache ti->clone during requeue
During requeue, block layer won't change the request any
more, such as no merge, so we can cache ti->clone and
let .clone_and_map_rq check if the cache can be hit.
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
drivers/md/dm-mpath.c | 31 ++++++++++++++++++++++++-------
drivers/md/dm-rq.c | 41 +++++++++++++++++++++++++++++------------
2 files changed, 53 insertions(+), 19 deletions(-)
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 9ee223170ee9..52e4730541fd 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -457,6 +457,11 @@ do { \
dm_noflush_suspending((m)->ti)); \
} while (0)
+static void multipath_release_clone(struct request *clone)
+{
+ blk_put_request(clone);
+}
+
/*
* Map cloned requests (request-based multipath)
*/
@@ -470,7 +475,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
struct block_device *bdev;
struct dm_mpath_io *mpio = get_mpio(map_context);
struct request_queue *q;
- struct request *clone;
+ struct request *clone = *__clone;
/* Do we need to select a new pgpath? */
pgpath = lockless_dereference(m->current_pgpath);
@@ -493,7 +498,23 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
bdev = pgpath->path.dev->bdev;
q = bdev_get_queue(bdev);
- clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE, GFP_ATOMIC);
+
+ /*
+ * This request may be from requeue path, and its clone
+ * may have been allocated before. We need to check
+ * if the cached clone can be hit.
+ */
+ if (clone) {
+ if (clone->q != q) {
+ blk_rq_unprep_clone(clone);
+ multipath_release_clone(clone);
+ clone = NULL;
+ } else
+ goto start_io;
+ }
+
+ if (!clone)
+ clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE, GFP_ATOMIC);
if (IS_ERR(clone)) {
/* EBUSY, ENODEV or EWOULDBLOCK: requeue */
bool queue_dying = blk_queue_dying(q);
@@ -520,6 +541,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
*__clone = clone;
+ start_io:
if (pgpath->pg->ps.type->start_io)
pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
&pgpath->path,
@@ -527,11 +549,6 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
return DM_MAPIO_REMAPPED;
}
-static void multipath_release_clone(struct request *clone)
-{
- blk_put_request(clone);
-}
-
/*
* Map cloned bios (bio-based multipath)
*/
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 46f012185b43..2ef524bddd38 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -221,6 +221,12 @@ static void dm_end_request(struct request *clone, blk_status_t error)
blk_rq_unprep_clone(clone);
tio->ti->type->release_clone_rq(clone);
+ /*
+ * We move the clearing from tio_init in .queue_rq to here because
+ * tio->clone may be cached during requeue
+ */
+ tio->clone = NULL;
+
rq_end_stats(md, rq);
if (!rq->q->mq_ops)
blk_end_request_all(rq, error);
@@ -267,11 +273,15 @@ static void dm_requeue_original_request(struct dm_rq_target_io *tio, bool delay_
int rw = rq_data_dir(rq);
unsigned long delay_ms = delay_requeue ? 100 : 0;
+ /*
+ * This request won't be changed any more during requeue,
+ * so we cache tio->clone and let .clone_and_map_rq decide
+ * to use the cached clone or allocate a new clone, and
+ * the cached clone has to be freed before allocating a
+ * new one.
+ */
+
rq_end_stats(md, rq);
- if (tio->clone) {
- blk_rq_unprep_clone(tio->clone);
- tio->ti->type->release_clone_rq(tio->clone);
- }
if (!rq->q->mq_ops)
dm_old_requeue_request(rq, delay_ms);
@@ -448,7 +458,6 @@ static void init_tio(struct dm_rq_target_io *tio, struct request *rq,
{
tio->md = md;
tio->ti = NULL;
- tio->clone = NULL;
tio->orig = rq;
tio->error = 0;
tio->completed = 0;
@@ -456,8 +465,12 @@ static void init_tio(struct dm_rq_target_io *tio, struct request *rq,
* Avoid initializing info for blk-mq; it passes
* target-specific data through info.ptr
* (see: dm_mq_init_request)
+ *
+ * If tio->clone is cached during requeue, we don't
+ * clear tio->info, and delay the initialization
+ * to .clone_and_map_rq if the cache isn't hit.
*/
- if (!md->init_tio_pdu)
+ if (!md->init_tio_pdu && !tio->clone)
memset(&tio->info, 0, sizeof(tio->info));
if (md->kworker_task)
kthread_init_work(&tio->work, map_tio_request);
@@ -475,7 +488,8 @@ static int map_request(struct dm_rq_target_io *tio)
struct dm_target *ti = tio->ti;
struct mapped_device *md = tio->md;
struct request *rq = tio->orig;
- struct request *clone = NULL;
+ struct request *cache = tio->clone;
+ struct request *clone = cache;
r = ti->type->clone_and_map_rq(ti, rq, &tio->info, &clone);
switch (r) {
@@ -483,10 +497,13 @@ static int map_request(struct dm_rq_target_io *tio)
/* The target has taken the I/O to submit by itself later */
break;
case DM_MAPIO_REMAPPED:
- if (setup_clone(clone, rq, tio, GFP_ATOMIC)) {
- /* -ENOMEM */
- ti->type->release_clone_rq(clone);
- return DM_MAPIO_REQUEUE;
+ /* cache not hit or not cached */
+ if (!cache || clone != cache) {
+ if (setup_clone(clone, rq, tio, GFP_ATOMIC)) {
+ /* -ENOMEM */
+ ti->type->release_clone_rq(clone);
+ return DM_MAPIO_REQUEUE;
+ }
}
/* The target has remapped the I/O so dispatch it */
@@ -555,7 +572,7 @@ static int __dm_rq_init_rq(struct mapped_device *md, struct request *rq)
* be available in dm_mq_queue_rq.
*/
tio->md = md;
-
+ tio->clone = NULL;
if (md->init_tio_pdu) {
/* target-specific per-io data is immediately after the tio */
tio->info.ptr = tio + 1;
--
2.9.5
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