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authorChristoph Hellwig <hch@lst.de>2019-04-11 08:23:27 +0200
committerJens Axboe <axboe@kernel.dk>2019-04-12 09:06:36 -0600
commit8a96a0e408102fb7aa73d8aa0b5e2219cfd51e55 (patch)
treea62d8c0f583ee464e40b5a41fae7cd4b891b7f31 /block/blk-merge.c
parent22391ac30ab9cc2ba610bf7ea2244840b83c8017 (diff)
downloadlinux-8a96a0e408102fb7aa73d8aa0b5e2219cfd51e55.tar.bz2
block: rewrite blk_bvec_map_sg to avoid a nth_page call
The offset in scatterlists is allowed to be larger than the page size, so don't go to great length to avoid that case and simplify the arithmetics. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-merge.c')
-rw-r--r--block/blk-merge.c21
1 files changed, 6 insertions, 15 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 895795cdb145..247b17f2a0f6 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -469,26 +469,17 @@ static unsigned blk_bvec_map_sg(struct request_queue *q,
struct scatterlist **sg)
{
unsigned nbytes = bvec->bv_len;
- unsigned nsegs = 0, total = 0, offset = 0;
+ unsigned nsegs = 0, total = 0;
while (nbytes > 0) {
- unsigned seg_size;
- struct page *pg;
- unsigned idx;
+ unsigned offset = bvec->bv_offset + total;
+ unsigned len = min(get_max_segment_size(q, offset), nbytes);
*sg = blk_next_sg(sg, sglist);
+ sg_set_page(*sg, bvec->bv_page, len, offset);
- seg_size = get_max_segment_size(q, bvec->bv_offset + total);
- seg_size = min(nbytes, seg_size);
-
- offset = (total + bvec->bv_offset) % PAGE_SIZE;
- idx = (total + bvec->bv_offset) / PAGE_SIZE;
- pg = bvec_nth_page(bvec->bv_page, idx);
-
- sg_set_page(*sg, pg, seg_size, offset);
-
- total += seg_size;
- nbytes -= seg_size;
+ total += len;
+ nbytes -= len;
nsegs++;
}