[1/1] blk-mq: reuse code in blk_mq_check_inflight*()

Commit Message

Pavel Begunkov Sept. 30, 2019, 8:27 a.m. UTC

From: Pavel Begunkov <[e-mail]>

1. Reuse the same walker callback for both blk_mq_in_flight() and
blk_mq_in_flight_rw().

2. Store inflight counters immediately in struct mq_inflight.
It's type-safer and removes extra indirection.

Signed-off-by: Pavel Begunkov <[e-mail]>
---
 block/blk-mq.c | 32 ++++++++------------------------
 1 file changed, 8 insertions(+), 24 deletions(-)

Comments

Christoph Hellwig Sept. 30, 2019, 8:33 a.m. UTC | #1

On Mon, Sep 30, 2019 at 11:27:32AM +0300, Pavel Begunkov (Silence) wrote:
> From: Pavel Begunkov <[e-mail]>
> 
> 1. Reuse the same walker callback for both blk_mq_in_flight() and
> blk_mq_in_flight_rw().
> 
> 2. Store inflight counters immediately in struct mq_inflight.
> It's type-safer and removes extra indirection.

You really want to split this into two patches.  Part 2 looks very
sensible to me, but I don't really see how 1 is qn equivalent
transformation right now.  Splitting it out and writing a non-trivial
changelog might help understanding it if you think it really is
equivalent as-is.

Pavel Begunkov Sept. 30, 2019, 9:20 a.m. UTC | #2

On 9/30/2019 11:33 AM, Christoph Hellwig wrote:
> On Mon, Sep 30, 2019 at 11:27:32AM +0300, Pavel Begunkov (Silence) wrote:
>> From: Pavel Begunkov <[e-mail]>
>>
>> 1. Reuse the same walker callback for both blk_mq_in_flight() and
>> blk_mq_in_flight_rw().
>>
>> 2. Store inflight counters immediately in struct mq_inflight.
>> It's type-safer and removes extra indirection.
> 
> You really want to split this into two patches.  Part 2 looks very

Good point, diff is peculiarly aligned indeed. I will resend it.

> sensible to me, but I don't really see how 1 is qn equivalent
> transformation right now.  Splitting it out and writing a non-trivial
> changelog might help understanding it if you think it really is
> equivalent as-is.
> 

blk_mq_check_inflight() increments only inflight[0].
blk_mq_check_inflight_rw() increments inflight[0] or inflight[1]
depending on a flag, so summing them gives what the first function returns.

Patch

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c4e5070c2ecd..d97181d9a3ec 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -93,7 +93,7 @@  static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
 
 struct mq_inflight {
 	struct hd_struct *part;
-	unsigned int *inflight;
+	unsigned int inflight[2];
 };
 
 static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
@@ -102,45 +102,29 @@  static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
 {
 	struct mq_inflight *mi = priv;
 
-	/*
-	 * index[0] counts the specific partition that was asked for.
-	 */
 	if (rq->part == mi->part)
-		mi->inflight[0]++;
+		mi->inflight[rq_data_dir(rq)]++;
 
 	return true;
 }
 
 unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part)
 {
-	unsigned inflight[2];
-	struct mq_inflight mi = { .part = part, .inflight = inflight, };
+	struct mq_inflight mi = { .part = part };
 
-	inflight[0] = inflight[1] = 0;
 	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
 
-	return inflight[0];
-}
-
-static bool blk_mq_check_inflight_rw(struct blk_mq_hw_ctx *hctx,
-				     struct request *rq, void *priv,
-				     bool reserved)
-{
-	struct mq_inflight *mi = priv;
-
-	if (rq->part == mi->part)
-		mi->inflight[rq_data_dir(rq)]++;
-
-	return true;
+	return mi.inflight[0] + mi.inflight[1];
 }
 
 void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
 			 unsigned int inflight[2])
 {
-	struct mq_inflight mi = { .part = part, .inflight = inflight, };
+	struct mq_inflight mi = { .part = part };
 
-	inflight[0] = inflight[1] = 0;
-	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight_rw, &mi);
+	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
+	inflight[0] = mi.inflight[0];
+	inflight[1] = mi.inflight[1];
 }
 
 void blk_freeze_queue_start(struct request_queue *q)