[PATCH 0/3] random simple block cleanups

[PATCH 0/3] random simple block cleanups

[Pavel Begunkov]

Several simple cleanups/optimisations splitted out from
the optimisation series.

Pavel Begunkov (3):
  block: optimise boundary blkdev_read_iter's checks
  block: clean up blk_mq_submit_bio() merging
  block: convert fops.c magic constants to SHIFT_SECTOR

 block/blk-mq-sched.c |  2 +-
 block/blk-mq-sched.h | 12 +-----------
 block/blk-mq.c       | 15 +++++++--------
 block/fops.c         | 37 +++++++++++++++++++++----------------
 4 files changed, 30 insertions(+), 36 deletions(-)

-- 
2.33.1

[PATCH 1/3] block: optimise boundary blkdev_read_iter's checks

[Pavel Begunkov]

Combine pos and len checks and mark unlikely. Also, don't reexpand if
it's not truncated.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 block/fops.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index 21d25ee0e4bf..8f733c919ed1 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -503,17 +503,20 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	size_t shorted = 0;
 	ssize_t ret;
 
-	if (pos >= size)
-		return 0;
-
-	size -= pos;
-	if (iov_iter_count(to) > size) {
-		shorted = iov_iter_count(to) - size;
-		iov_iter_truncate(to, size);
+	if (unlikely(pos + iov_iter_count(to) > size)) {
+		if (pos >= size)
+			return 0;
+		size -= pos;
+		if (iov_iter_count(to) > size) {
+			shorted = iov_iter_count(to) - size;
+			iov_iter_truncate(to, size);
+		}
 	}
 
 	ret = generic_file_read_iter(iocb, to);
-	iov_iter_reexpand(to, iov_iter_count(to) + shorted);
+
+	if (unlikely(shorted))
+		iov_iter_reexpand(to, iov_iter_count(to) + shorted);
 	return ret;
 }
 
-- 
2.33.1

[PATCH 2/3] block: clean up blk_mq_submit_bio() merging

[Pavel Begunkov]

Combine blk_mq_sched_bio_merge() and blk_attempt_plug_merge() under a
common if, so we don't check it twice.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 block/blk-mq-sched.c |  2 +-
 block/blk-mq-sched.h | 12 +-----------
 block/blk-mq.c       | 15 +++++++--------
 3 files changed, 9 insertions(+), 20 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index e85b7556b096..5b259fdea794 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -361,7 +361,7 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 	}
 }
 
-bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
+bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
 		unsigned int nr_segs)
 {
 	struct elevator_queue *e = q->elevator;
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 98836106b25f..25d1034952b6 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -12,7 +12,7 @@ void blk_mq_sched_assign_ioc(struct request *rq);
 
 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
 		unsigned int nr_segs, struct request **merged_request);
-bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
+bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
 		unsigned int nr_segs);
 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq,
 				   struct list_head *free);
@@ -42,16 +42,6 @@ static inline bool bio_mergeable(struct bio *bio)
 	return !(bio->bi_opf & REQ_NOMERGE_FLAGS);
 }
 
-static inline bool
-blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
-		unsigned int nr_segs)
-{
-	if (blk_queue_nomerges(q) || !bio_mergeable(bio))
-		return false;
-
-	return __blk_mq_sched_bio_merge(q, bio, nr_segs);
-}
-
 static inline bool
 blk_mq_sched_allow_merge(struct request_queue *q, struct request *rq,
 			 struct bio *bio)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index a71aeed7b987..f159d007a015 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2481,7 +2481,6 @@ void blk_mq_submit_bio(struct bio *bio)
 {
 	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
 	const int is_sync = op_is_sync(bio->bi_opf);
-	const int is_flush_fua = op_is_flush(bio->bi_opf);
 	struct request *rq;
 	struct blk_plug *plug;
 	bool same_queue_rq = false;
@@ -2495,12 +2494,12 @@ void blk_mq_submit_bio(struct bio *bio)
 	if (!bio_integrity_prep(bio))
 		goto queue_exit;
 
-	if (!is_flush_fua && !blk_queue_nomerges(q) &&
-	    blk_attempt_plug_merge(q, bio, nr_segs, &same_queue_rq))
-		goto queue_exit;
-
-	if (blk_mq_sched_bio_merge(q, bio, nr_segs))
-		goto queue_exit;
+	if (!blk_queue_nomerges(q) && bio_mergeable(bio)) {
+		if (blk_attempt_plug_merge(q, bio, nr_segs, &same_queue_rq))
+			goto queue_exit;
+		if (blk_mq_sched_bio_merge(q, bio, nr_segs))
+			goto queue_exit;
+	}
 
 	rq_qos_throttle(q, bio);
 
@@ -2543,7 +2542,7 @@ void blk_mq_submit_bio(struct bio *bio)
 		return;
 	}
 
-	if (is_flush_fua && blk_insert_flush(rq))
+	if (op_is_flush(bio->bi_opf) && blk_insert_flush(rq))
 		return;
 
 	if (plug && (q->nr_hw_queues == 1 ||
-- 
2.33.1

[PATCH 3/3] block: convert fops.c magic constants to SHIFT_SECTOR

[Pavel Begunkov]

Don't use shifting by a magic number 9 but replace with a more
descriptive SHIFT_SECTOR.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 block/fops.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index 8f733c919ed1..396537598e3e 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -76,7 +76,7 @@ static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
 
 	bio_init(&bio, vecs, nr_pages);
 	bio_set_dev(&bio, bdev);
-	bio.bi_iter.bi_sector = pos >> 9;
+	bio.bi_iter.bi_sector = pos >> SECTOR_SHIFT;
 	bio.bi_write_hint = iocb->ki_hint;
 	bio.bi_private = current;
 	bio.bi_end_io = blkdev_bio_end_io_simple;
@@ -225,7 +225,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 
 	for (;;) {
 		bio_set_dev(bio, bdev);
-		bio->bi_iter.bi_sector = pos >> 9;
+		bio->bi_iter.bi_sector = pos >> SECTOR_SHIFT;
 		bio->bi_write_hint = iocb->ki_hint;
 		bio->bi_private = dio;
 		bio->bi_end_io = blkdev_bio_end_io;
@@ -565,16 +565,18 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 	switch (mode) {
 	case FALLOC_FL_ZERO_RANGE:
 	case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:
-		error = blkdev_issue_zeroout(bdev, start >> 9, len >> 9,
-					    GFP_KERNEL, BLKDEV_ZERO_NOUNMAP);
+		error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
+					     len >> SECTOR_SHIFT, GFP_KERNEL,
+					     BLKDEV_ZERO_NOUNMAP);
 		break;
 	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
-		error = blkdev_issue_zeroout(bdev, start >> 9, len >> 9,
-					     GFP_KERNEL, BLKDEV_ZERO_NOFALLBACK);
+		error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
+					     len >> SECTOR_SHIFT, GFP_KERNEL,
+					     BLKDEV_ZERO_NOFALLBACK);
 		break;
 	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE:
-		error = blkdev_issue_discard(bdev, start >> 9, len >> 9,
-					     GFP_KERNEL, 0);
+		error = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
+					     len >> SECTOR_SHIFT, GFP_KERNEL, 0);
 		break;
 	default:
 		error = -EOPNOTSUPP;
-- 
2.33.1

Re: [PATCH 2/3] block: clean up blk_mq_submit_bio() merging

[Pavel Begunkov]

On 10/20/21 20:00, Pavel Begunkov wrote:
> Combine blk_mq_sched_bio_merge() and blk_attempt_plug_merge() under a
> common if, so we don't check it twice.

Forgot to add that it's v2 with changes from Christoph's review.

-- 
Pavel Begunkov

Re: [PATCH 2/3] block: clean up blk_mq_submit_bio() merging

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 3/3] block: convert fops.c magic constants to SHIFT_SECTOR

[Christoph Hellwig]

On Wed, Oct 20, 2021 at 08:00:50PM +0100, Pavel Begunkov wrote:
> Don't use shifting by a magic number 9 but replace with a more
> descriptive SHIFT_SECTOR.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Although I wonder if two new local variables in blkdev_fallocate
wouldn't be even better..

Re: [PATCH 2/3] block: clean up blk_mq_submit_bio() merging

[Pavel Begunkov]

On 10/21/21 09:30, Christoph Hellwig wrote:
> Looks good,
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Great, thanks!

-- 
Pavel Begunkov

Re: [PATCH 0/3] random simple block cleanups

[Jens Axboe]

On Wed, 20 Oct 2021 20:00:47 +0100, Pavel Begunkov wrote:
> Several simple cleanups/optimisations splitted out from
> the optimisation series.
> 
> Pavel Begunkov (3):
>   block: optimise boundary blkdev_read_iter's checks
>   block: clean up blk_mq_submit_bio() merging
>   block: convert fops.c magic constants to SHIFT_SECTOR
> 
> [...]

Applied, thanks!

[1/3] block: optimise boundary blkdev_read_iter's checks
      commit: 6450fe1f668f410fe2ab69c79a52a0929a4a8296
[2/3] block: clean up blk_mq_submit_bio() merging
      commit: 179ae84f7ef5225e03cd29cb9a75f6e90d2d7388
[3/3] block: convert fops.c magic constants to SHIFT_SECTOR
      commit: 6549a874fb65e7ad4885d066ec314191cc137b52

Best regards,
-- 
Jens Axboe