linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ming Lei <ming.lei@redhat.com>, Christoph Hellwig <hch@lst.de>
Subject: [PATCH V9 04/19] block: use bio_for_each_bvec() to map sg
Date: Tue, 13 Nov 2018 23:14:50 +0800	[thread overview]
Message-ID: <20181113151505.15498-5-ming.lei@redhat.com> (raw)
In-Reply-To: <20181113151505.15498-1-ming.lei@redhat.com>

It is more efficient to use bio_for_each_bvec() to map sg, meantime
we have to consider splitting multipage bvec as done in blk_bio_segment_split().

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-merge.c | 72 +++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 52 insertions(+), 20 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 6f7deb94a23f..cb9f49bcfd36 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -473,6 +473,56 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
 	return biovec_phys_mergeable(q, &end_bv, &nxt_bv);
 }
 
+static struct scatterlist *blk_next_sg(struct scatterlist **sg,
+		struct scatterlist *sglist)
+{
+	if (!*sg)
+		return sglist;
+	else {
+		/*
+		 * If the driver previously mapped a shorter
+		 * list, we could see a termination bit
+		 * prematurely unless it fully inits the sg
+		 * table on each mapping. We KNOW that there
+		 * must be more entries here or the driver
+		 * would be buggy, so force clear the
+		 * termination bit to avoid doing a full
+		 * sg_init_table() in drivers for each command.
+		 */
+		sg_unmark_end(*sg);
+		return sg_next(*sg);
+	}
+}
+
+static unsigned blk_bvec_map_sg(struct request_queue *q,
+		struct bio_vec *bvec, struct scatterlist *sglist,
+		struct scatterlist **sg)
+{
+	unsigned nbytes = bvec->bv_len;
+	unsigned nsegs = 0, total = 0;
+
+	while (nbytes > 0) {
+		unsigned seg_size;
+		struct page *pg;
+		unsigned offset, idx;
+
+		*sg = blk_next_sg(sg, sglist);
+
+		seg_size = min(nbytes, queue_max_segment_size(q));
+		offset = (total + bvec->bv_offset) % PAGE_SIZE;
+		idx = (total + bvec->bv_offset) / PAGE_SIZE;
+		pg = nth_page(bvec->bv_page, idx);
+
+		sg_set_page(*sg, pg, seg_size, offset);
+
+		total += seg_size;
+		nbytes -= seg_size;
+		nsegs++;
+	}
+
+	return nsegs;
+}
+
 static inline void
 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 		     struct scatterlist *sglist, struct bio_vec *bvprv,
@@ -490,25 +540,7 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 		(*sg)->length += nbytes;
 	} else {
 new_segment:
-		if (!*sg)
-			*sg = sglist;
-		else {
-			/*
-			 * If the driver previously mapped a shorter
-			 * list, we could see a termination bit
-			 * prematurely unless it fully inits the sg
-			 * table on each mapping. We KNOW that there
-			 * must be more entries here or the driver
-			 * would be buggy, so force clear the
-			 * termination bit to avoid doing a full
-			 * sg_init_table() in drivers for each command.
-			 */
-			sg_unmark_end(*sg);
-			*sg = sg_next(*sg);
-		}
-
-		sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
-		(*nsegs)++;
+		(*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg);
 	}
 	*bvprv = *bvec;
 }
@@ -530,7 +562,7 @@ static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 	int cluster = blk_queue_cluster(q), nsegs = 0;
 
 	for_each_bio(bio)
-		bio_for_each_segment(bvec, bio, iter)
+		bio_for_each_bvec(bvec, bio, iter)
 			__blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
 					     &nsegs, &cluster);
 
-- 
2.9.5


  parent reply	other threads:[~2018-11-13 15:15 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-13 15:14 [PATCH V9 00/19] block: support multi-page bvec Ming Lei
2018-11-13 15:14 ` [PATCH V9 01/19] block: introduce multi-page page bvec helpers Ming Lei
2018-11-13 15:14 ` [PATCH V9 02/19] block: introduce bio_for_each_bvec() Ming Lei
2018-11-13 15:14 ` [PATCH V9 03/19] block: use bio_for_each_bvec() to compute multi-page bvec count Ming Lei
2018-11-13 15:14 ` Ming Lei [this message]
2018-11-13 15:14 ` [PATCH V9 05/19] block: introduce bvec_last_segment() Ming Lei
2018-11-13 15:14 ` [PATCH V9 06/19] fs/buffer.c: use bvec iterator to truncate the bio Ming Lei
2018-11-13 15:14 ` [PATCH V9 07/19] btrfs: use bvec_last_segment to get bio's last page Ming Lei
2018-11-13 15:14 ` [PATCH V9 08/19] btrfs: move bio_pages_all() to btrfs Ming Lei
2018-11-13 15:14 ` [PATCH V9 09/19] block: introduce bio_bvecs() Ming Lei
2018-11-13 15:14 ` [PATCH V9 10/19] block: loop: pass multi-page bvec to iov_iter Ming Lei
2018-11-13 15:14 ` [PATCH V9 11/19] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages() Ming Lei
2018-11-13 15:14 ` [PATCH V9 12/19] block: allow bio_for_each_segment_all() to iterate over multi-page bvec Ming Lei
2018-11-13 15:14 ` [PATCH V9 13/19] iomap & xfs: only account for new added page Ming Lei
2018-11-13 15:15 ` [PATCH V9 14/19] block: enable multipage bvecs Ming Lei
2018-11-13 15:15 ` [PATCH V9 15/19] block: always define BIO_MAX_PAGES as 256 Ming Lei
2018-11-13 15:15 ` [PATCH V9 16/19] block: document usage of bio iterator helpers Ming Lei
2018-11-13 15:15 ` [PATCH V9 17/19] block: don't use bio->bi_vcnt to figure out segment number Ming Lei
2018-11-13 15:15 ` [PATCH V9 18/19] block: kill QUEUE_FLAG_NO_SG_MERGE Ming Lei
2018-11-13 15:15 ` [PATCH V9 19/19] block: kill BLK_MQ_F_SG_MERGE Ming Lei
2018-11-14  2:44 ` [PATCH V9 00/19] block: support multi-page bvec Dave Chinner
2018-11-14  2:57   ` Ming Lei
2018-11-14 15:22   ` Christoph Hellwig
2018-11-15  9:35     ` Ming Lei

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181113151505.15498-5-ming.lei@redhat.com \
    --to=ming.lei@redhat.com \
    --cc=axboe@kernel.dk \
    --cc=hch@lst.de \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --subject='Re: [PATCH V9 04/19] block: use bio_for_each_bvec() to map sg' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox