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Message-Id: <20170930102720.30219-2-ming.lei@redhat.com>
Date: Sat, 30 Sep 2017 18:27:14 +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>,
Paolo Valente <paolo.valente@...aro.org>,
Oleksandr Natalenko <oleksandr@...alenko.name>,
Tom Nguyen <tom81094@...il.com>, linux-kernel@...r.kernel.org,
linux-scsi@...r.kernel.org, Omar Sandoval <osandov@...com>,
Ming Lei <ming.lei@...hat.com>
Subject: [PATCH V5 1/7] blk-mq: issue rq directly in blk_mq_request_bypass_insert()
With issuing rq directly in blk_mq_request_bypass_insert(),
we can:
1) avoid to acquire hctx->lock.
2) the dispatch result can be returned to dm-rq, so that dm-rq
can use this information for improving I/O performance, and
part2 of this patchset will do that.
3) Also the following patch for improving sequential I/O performance
uses hctx->dispatch to decide if hctx is busy, so we need to avoid
to add rq into hctx->dispatch direclty.
There will be another patch in which we move blk_mq_request_direct_insert()
out since it is better for dm-rq to deal with this situation, and
the IO scheduler is actually in dm-rq side.
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
block/blk-core.c | 3 +--
block/blk-mq.c | 70 ++++++++++++++++++++++++++++++++++++++----------------
block/blk-mq.h | 2 +-
drivers/md/dm-rq.c | 2 +-
4 files changed, 52 insertions(+), 25 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 048be4aa6024..4c7fd2231145 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2350,8 +2350,7 @@ blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *
* bypass a potential scheduler on the bottom device for
* insert.
*/
- blk_mq_request_bypass_insert(rq);
- return BLK_STS_OK;
+ return blk_mq_request_bypass_insert(rq);
}
spin_lock_irqsave(q->queue_lock, flags);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 98a18609755e..d1b9fb539eba 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -39,6 +39,8 @@
static void blk_mq_poll_stats_start(struct request_queue *q);
static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
+static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+ struct request *rq, blk_qc_t *cookie, bool dispatch_only);
static int blk_mq_poll_stats_bkt(const struct request *rq)
{
@@ -1401,20 +1403,31 @@ void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
blk_mq_hctx_mark_pending(hctx, ctx);
}
+static void blk_mq_request_direct_insert(struct blk_mq_hw_ctx *hctx,
+ struct request *rq)
+{
+ spin_lock(&hctx->lock);
+ list_add_tail(&rq->queuelist, &hctx->dispatch);
+ spin_unlock(&hctx->lock);
+
+ blk_mq_run_hw_queue(hctx, false);
+}
+
/*
* Should only be used carefully, when the caller knows we want to
* bypass a potential IO scheduler on the target device.
*/
-void blk_mq_request_bypass_insert(struct request *rq)
+blk_status_t blk_mq_request_bypass_insert(struct request *rq)
{
struct blk_mq_ctx *ctx = rq->mq_ctx;
struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(rq->q, ctx->cpu);
+ blk_qc_t cookie;
+ blk_status_t ret;
- spin_lock(&hctx->lock);
- list_add_tail(&rq->queuelist, &hctx->dispatch);
- spin_unlock(&hctx->lock);
-
- blk_mq_run_hw_queue(hctx, false);
+ ret = blk_mq_try_issue_directly(hctx, rq, &cookie, true);
+ if (ret == BLK_STS_RESOURCE)
+ blk_mq_request_direct_insert(hctx, rq);
+ return ret;
}
void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
@@ -1527,9 +1540,14 @@ static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx, struct request *rq)
return blk_tag_to_qc_t(rq->internal_tag, hctx->queue_num, true);
}
-static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
- struct request *rq,
- blk_qc_t *cookie, bool may_sleep)
+/*
+ * 'dispatch_only' means we only try to dispatch it out, and
+ * don't deal with dispatch failure if BLK_STS_RESOURCE or
+ * BLK_STS_IOERR happens.
+ */
+static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+ struct request *rq, blk_qc_t *cookie, bool may_sleep,
+ bool dispatch_only)
{
struct request_queue *q = rq->q;
struct blk_mq_queue_data bd = {
@@ -1537,7 +1555,7 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
.last = true,
};
blk_qc_t new_cookie;
- blk_status_t ret;
+ blk_status_t ret = BLK_STS_OK;
bool run_queue = true;
/* RCU or SRCU read lock is needed before checking quiesced flag */
@@ -1546,9 +1564,10 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
goto insert;
}
- if (q->elevator)
+ if (q->elevator && !dispatch_only)
goto insert;
+ ret = BLK_STS_RESOURCE;
if (!blk_mq_get_driver_tag(rq, NULL, false))
goto insert;
@@ -1563,26 +1582,32 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
switch (ret) {
case BLK_STS_OK:
*cookie = new_cookie;
- return;
+ return ret;
case BLK_STS_RESOURCE:
__blk_mq_requeue_request(rq);
goto insert;
default:
*cookie = BLK_QC_T_NONE;
- blk_mq_end_request(rq, ret);
- return;
+ if (!dispatch_only)
+ blk_mq_end_request(rq, ret);
+ return ret;
}
insert:
- blk_mq_sched_insert_request(rq, false, run_queue, false, may_sleep);
+ if (!dispatch_only)
+ blk_mq_sched_insert_request(rq, false, run_queue, false, may_sleep);
+ return ret;
}
-static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
- struct request *rq, blk_qc_t *cookie)
+static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+ struct request *rq, blk_qc_t *cookie, bool dispatch_only)
{
+ blk_status_t ret;
+
if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
rcu_read_lock();
- __blk_mq_try_issue_directly(hctx, rq, cookie, false);
+ ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false,
+ dispatch_only);
rcu_read_unlock();
} else {
unsigned int srcu_idx;
@@ -1590,9 +1615,12 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
might_sleep();
srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
- __blk_mq_try_issue_directly(hctx, rq, cookie, true);
+ ret = __blk_mq_try_issue_directly(hctx, rq, cookie, true,
+ dispatch_only);
srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
}
+
+ return ret;
}
static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
@@ -1697,12 +1725,12 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
data.hctx = blk_mq_map_queue(q,
same_queue_rq->mq_ctx->cpu);
blk_mq_try_issue_directly(data.hctx, same_queue_rq,
- &cookie);
+ &cookie, false);
}
} else if (q->nr_hw_queues > 1 && is_sync) {
blk_mq_put_ctx(data.ctx);
blk_mq_bio_to_request(rq, bio);
- blk_mq_try_issue_directly(data.hctx, rq, &cookie);
+ blk_mq_try_issue_directly(data.hctx, rq, &cookie, false);
} else if (q->elevator) {
blk_mq_put_ctx(data.ctx);
blk_mq_bio_to_request(rq, bio);
diff --git a/block/blk-mq.h b/block/blk-mq.h
index ef15b3414da5..61aecf398a4b 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -54,7 +54,7 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
*/
void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
bool at_head);
-void blk_mq_request_bypass_insert(struct request *rq);
+blk_status_t blk_mq_request_bypass_insert(struct request *rq);
void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
struct list_head *list);
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 29b237dcc39d..f5e2b6967357 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -404,7 +404,7 @@ static void dm_dispatch_clone_request(struct request *clone, struct request *rq)
clone->start_time = jiffies;
r = blk_insert_cloned_request(clone->q, clone);
- if (r)
+ if (r != BLK_STS_OK && r != BLK_STS_RESOURCE)
/* must complete clone in terms of original request */
dm_complete_request(rq, r);
}
--
2.9.5
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