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Revert "block: blk-merge: try to make front segments in full size" 

This reverts commit a2d37968d7.

If max segment size isn't 512-aligned, this patch won't work well.

Also once multipage bvec is enabled, adjacent bvecs won't be physically
contiguous if page is added via bio_add_page(), so we don't need this
kind of complicated logic.

Reported-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2018-01-10 10:51:29 +08:00 committed by Jens Axboe
parent 5448aca41c
commit b4b6cb6135
1 changed files with 5 additions and 49 deletions
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54
block/blk-merge.c
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@ -109,7 +109,6 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
bool do_split = true;
struct bio *new = NULL;
const unsigned max_sectors = get_max_io_size(q, bio);
unsigned advance = 0;
bio_for_each_segment(bv, bio, iter) {
/*
@ -133,32 +132,12 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
}
if (bvprvp && blk_queue_cluster(q)) {
if (seg_size + bv.bv_len > queue_max_segment_size(q))
goto new_segment;
if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
goto new_segment;
if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
goto new_segment;
if (seg_size + bv.bv_len > queue_max_segment_size(q)) {
/*
* One assumption is that initial value of
* @seg_size(equals to bv.bv_len) won't be
* bigger than max segment size, but this
* becomes false after multipage bvecs.
*/
advance = queue_max_segment_size(q) - seg_size;
if (advance > 0) {
seg_size += advance;
sectors += advance >> 9;
bv.bv_len -= advance;
bv.bv_offset += advance;
}
/*
* Still need to put remainder of current
* bvec into a new segment.
*/
goto new_segment;
}
seg_size += bv.bv_len;
bvprv = bv;
@ -180,12 +159,6 @@ new_segment:
seg_size = bv.bv_len;
sectors += bv.bv_len >> 9;
/* restore the bvec for iterator */
if (advance) {
bv.bv_len += advance;
bv.bv_offset -= advance;
advance = 0;
}
}
do_split = false;
@ -386,29 +359,16 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
{
int nbytes = bvec->bv_len;
unsigned advance = 0;
if (*sg && *cluster) {
if ((*sg)->length + nbytes > queue_max_segment_size(q))
goto new_segment;
if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
goto new_segment;
if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
goto new_segment;
/*
* try best to merge part of the bvec into previous
* segment and follow same policy with
* blk_bio_segment_split()
*/
if ((*sg)->length + nbytes > queue_max_segment_size(q)) {
advance = queue_max_segment_size(q) - (*sg)->length;
if (advance) {
(*sg)->length += advance;
bvec->bv_offset += advance;
bvec->bv_len -= advance;
}
goto new_segment;
}
(*sg)->length += nbytes;
} else {
new_segment:
@ -431,10 +391,6 @@ new_segment:
sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
(*nsegs)++;
/* for making iterator happy */
bvec->bv_offset -= advance;
bvec->bv_len += advance;
}
*bvprv = *bvec;
}