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-rw-r--r--block/blk-merge.c54
1 files changed, 49 insertions, 5 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index a476337a8ff4..ca2e7aec8e77 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -109,6 +109,7 @@ 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) {
/*
@@ -134,12 +135,32 @@ 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;
@@ -161,6 +182,12 @@ 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;
@@ -361,16 +388,29 @@ __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:
@@ -393,6 +433,10 @@ 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;
}