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Message-ID: <9cb12b99feb2886a21084bf3f93fab773c93c465.1430414610.git.shli@fb.com>
Date: Thu, 30 Apr 2015 10:45:18 -0700
From: Shaohua Li <shli@...com>
To: <linux-kernel@...r.kernel.org>
CC: <axboe@...com>, <jmoyer@...hat.com>, <hch@....de>, <neilb@...e.de>
Subject: [PATCH 5/5] blk-mq: make plug work for mutiple disks and queues
Last patch makes plug work for multiple queue case. However it only
works for single disk case, because it assumes only one request in the
plug list. If a task is accessing multiple disks, eg MD/DM, the
assumption is wrong. Let blk_attempt_plug_merge() record request from
the same queue.
Cc: Jens Axboe <axboe@...com>
Cc: Christoph Hellwig <hch@....de>
Signed-off-by: Shaohua Li <shli@...com>
---
block/blk-core.c | 10 +++++++---
block/blk-mq.c | 11 ++++++-----
block/blk.h | 3 ++-
3 files changed, 15 insertions(+), 9 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index d51ed61..a5e1574 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1521,7 +1521,8 @@ bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
* Caller must ensure !blk_queue_nomerges(q) beforehand.
*/
bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
- unsigned int *request_count)
+ unsigned int *request_count,
+ struct request **same_queue_rq)
{
struct blk_plug *plug;
struct request *rq;
@@ -1541,8 +1542,10 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
list_for_each_entry_reverse(rq, plug_list, queuelist) {
int el_ret;
- if (rq->q == q)
+ if (rq->q == q) {
(*request_count)++;
+ *same_queue_rq = rq;
+ }
if (rq->q != q || !blk_rq_merge_ok(rq, bio))
continue;
@@ -1583,6 +1586,7 @@ void blk_queue_bio(struct request_queue *q, struct bio *bio)
int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
struct request *req;
unsigned int request_count = 0;
+ struct request *same_queue_rq;
/*
* low level driver can indicate that it wants pages above a
@@ -1607,7 +1611,7 @@ void blk_queue_bio(struct request_queue *q, struct bio *bio)
* any locks.
*/
if (!blk_queue_nomerges(q) &&
- blk_attempt_plug_merge(q, bio, &request_count))
+ blk_attempt_plug_merge(q, bio, &request_count, &same_queue_rq))
return;
spin_lock_irq(q->queue_lock);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5545828..c45739c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1269,6 +1269,7 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
struct request *rq;
unsigned int request_count = 0;
struct blk_plug *plug;
+ struct request *same_queue_rq = NULL;
blk_queue_bounce(q, &bio);
@@ -1278,7 +1279,7 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
}
if (likely(!is_flush_fua) && !blk_queue_nomerges(q) &&
- blk_attempt_plug_merge(q, bio, &request_count))
+ blk_attempt_plug_merge(q, bio, &request_count, &same_queue_rq))
return;
rq = blk_mq_map_request(q, bio, &data);
@@ -1308,9 +1309,8 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
* issued. So the plug list will have one request at most
*/
if (plug) {
- if (!list_empty(&plug->mq_list)) {
- old_rq = list_first_entry(&plug->mq_list,
- struct request, queuelist);
+ if (same_queue_rq) {
+ old_rq = same_queue_rq;
list_del_init(&old_rq->queuelist);
}
list_add_tail(&rq->queuelist, &plug->mq_list);
@@ -1350,6 +1350,7 @@ static void blk_sq_make_request(struct request_queue *q, struct bio *bio)
unsigned int request_count = 0;
struct blk_map_ctx data;
struct request *rq;
+ struct request *same_queue_rq;
blk_queue_bounce(q, &bio);
@@ -1359,7 +1360,7 @@ static void blk_sq_make_request(struct request_queue *q, struct bio *bio)
}
if (likely(!is_flush_fua) && !blk_queue_nomerges(q) &&
- blk_attempt_plug_merge(q, bio, &request_count))
+ blk_attempt_plug_merge(q, bio, &request_count, &same_queue_rq))
return;
rq = blk_mq_map_request(q, bio, &data);
diff --git a/block/blk.h b/block/blk.h
index 43b0361..aa8633c 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -78,7 +78,8 @@ bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
struct bio *bio);
bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
- unsigned int *request_count);
+ unsigned int *request_count,
+ struct request **same_queue_rq);
void blk_account_io_start(struct request *req, bool new_io);
void blk_account_io_completion(struct request *req, unsigned int bytes);
--
1.8.1
--
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