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Subject[PATCH V2 1/2] blk-mq: abstract out blk-mq-sched rq list iteration bio merge helper
Date
From: Jens Axboe <axboe@kernel.dk>

No functional changes in this patch, just a prep patch for utilizing
this in an IO scheduler.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/blk-mq-sched.c | 34 ++++++++++++++++++++++++----------
include/linux/blk-mq.h | 3 ++-
2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 25c14c5..b0f2c2a 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -268,19 +268,16 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);

/*
- * Reverse check our software queue for entries that we could potentially
- * merge with. Currently includes a hand-wavy stop count of 8, to not spend
- * too much time checking for merges.
+ * Iterate list of requests and see if we can merge this bio with any
+ * of them.
*/
-static bool blk_mq_attempt_merge(struct request_queue *q,
- struct blk_mq_ctx *ctx, struct bio *bio)
+bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
+ struct bio *bio)
{
struct request *rq;
int checked = 8;

- lockdep_assert_held(&ctx->lock);
-
- list_for_each_entry_reverse(rq, &ctx->rq_list, queuelist) {
+ list_for_each_entry_reverse(rq, list, queuelist) {
bool merged = false;

if (!checked--)
@@ -305,13 +302,30 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
continue;
}

- if (merged)
- ctx->rq_merged++;
return merged;
}

return false;
}
+EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge);
+
+/*
+ * Reverse check our software queue for entries that we could potentially
+ * merge with. Currently includes a hand-wavy stop count of 8, to not spend
+ * too much time checking for merges.
+ */
+static bool blk_mq_attempt_merge(struct request_queue *q,
+ struct blk_mq_ctx *ctx, struct bio *bio)
+{
+ lockdep_assert_held(&ctx->lock);
+
+ if (blk_mq_bio_list_merge(q, &ctx->rq_list, bio)) {
+ ctx->rq_merged++;
+ return true;
+ }
+
+ return false;
+}

bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
{
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index ebc34a5..fb35517 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -259,7 +259,8 @@ void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
void blk_mq_kick_requeue_list(struct request_queue *q);
void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs);
void blk_mq_complete_request(struct request *rq);
-
+bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
+ struct bio *bio);
bool blk_mq_queue_stopped(struct request_queue *q);
void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);
void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx);
--
2.7.4
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