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
next prev 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
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