[1/8] blk-mq: move hctx lock/unlock into a helper

Commit Message

Tejun Heo Jan. 8, 2018, 7:15 p.m. UTC

From: Jens Axboe <[e-mail]>

Move the RCU vs SRCU logic into lock/unlock helpers, which makes
the actual functional bits within the locked region much easier
to read.

tj: Reordered in front of timeout revamp patches and added the missing
    blk_mq_run_hw_queue() conversion.

Signed-off-by: Jens Axboe <[e-mail]>
Signed-off-by: Tejun Heo <[e-mail]>
---
 block/blk-mq.c | 66 ++++++++++++++++++++++++++++------------------------------
 1 file changed, 32 insertions(+), 34 deletions(-)

Comments

Bart Van Assche Jan. 8, 2018, 7:24 p.m. UTC | #1

On Mon, 2018-01-08 at 11:15 -0800, Tejun Heo wrote:
> +static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)

> +{

> +	if (!(hctx->flags & BLK_MQ_F_BLOCKING))

> +		rcu_read_unlock();

> +	else

> +		srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);

> +}

> +

> +static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)

> +{

> +	if (!(hctx->flags & BLK_MQ_F_BLOCKING))

> +		rcu_read_lock();

> +	else

> +		*srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);

> +}


A minor comment: please consider to reorder these two functions such that the
lock function appears first and the unlock function second. Anyway:

Reviewed-by: Bart Van Assche <[e-mail]>

Patch

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 111e1aa..ddc9261 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -557,6 +557,22 @@  static void __blk_mq_complete_request(struct request *rq)
 	put_cpu();
 }
 
+static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
+{
+	if (!(hctx->flags & BLK_MQ_F_BLOCKING))
+		rcu_read_unlock();
+	else
+		srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
+}
+
+static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
+{
+	if (!(hctx->flags & BLK_MQ_F_BLOCKING))
+		rcu_read_lock();
+	else
+		*srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
+}
+
 /**
  * blk_mq_complete_request - end I/O on a request
  * @rq:		the request being processed
@@ -1214,17 +1230,11 @@  static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
 	 */
 	WARN_ON_ONCE(in_interrupt());
 
-	if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
-		rcu_read_lock();
-		blk_mq_sched_dispatch_requests(hctx);
-		rcu_read_unlock();
-	} else {
-		might_sleep();
+	might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
 
-		srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
-		blk_mq_sched_dispatch_requests(hctx);
-		srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
-	}
+	hctx_lock(hctx, &srcu_idx);
+	blk_mq_sched_dispatch_requests(hctx);
+	hctx_unlock(hctx, srcu_idx);
 }
 
 /*
@@ -1296,17 +1306,10 @@  bool blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 	 * And queue will be rerun in blk_mq_unquiesce_queue() if it is
 	 * quiesced.
 	 */
-	if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
-		rcu_read_lock();
-		need_run = !blk_queue_quiesced(hctx->queue) &&
-			blk_mq_hctx_has_pending(hctx);
-		rcu_read_unlock();
-	} else {
-		srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
-		need_run = !blk_queue_quiesced(hctx->queue) &&
-			blk_mq_hctx_has_pending(hctx);
-		srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
-	}
+	hctx_lock(hctx, &srcu_idx);
+	need_run = !blk_queue_quiesced(hctx->queue) &&
+		blk_mq_hctx_has_pending(hctx);
+	hctx_unlock(hctx, srcu_idx);
 
 	if (need_run) {
 		__blk_mq_delay_run_hw_queue(hctx, async, 0);
@@ -1618,7 +1621,7 @@  static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx, struct request *rq)
 
 static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 					struct request *rq,
-					blk_qc_t *cookie, bool may_sleep)
+					blk_qc_t *cookie)
 {
 	struct request_queue *q = rq->q;
 	struct blk_mq_queue_data bd = {
@@ -1668,25 +1671,20 @@  static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 	}
 
 insert:
-	blk_mq_sched_insert_request(rq, false, run_queue, false, may_sleep);
+	blk_mq_sched_insert_request(rq, false, run_queue, false,
+					hctx->flags & BLK_MQ_F_BLOCKING);
 }
 
 static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 		struct request *rq, blk_qc_t *cookie)
 {
-	if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
-		rcu_read_lock();
-		__blk_mq_try_issue_directly(hctx, rq, cookie, false);
-		rcu_read_unlock();
-	} else {
-		unsigned int srcu_idx;
+	int srcu_idx;
 
-		might_sleep();
+	might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
 
-		srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
-		__blk_mq_try_issue_directly(hctx, rq, cookie, true);
-		srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
-	}
+	hctx_lock(hctx, &srcu_idx);
+	__blk_mq_try_issue_directly(hctx, rq, cookie);
+	hctx_unlock(hctx, srcu_idx);
 }
 
 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)