[PATCH v3 25/49] block: use bio_for_each_segment_mp() to map sg

[Ming Lei]

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

Signed-off-by: Ming Lei 
---
 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 c9b300f91fba..33353ed8c32e 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -439,6 +439,56 @@ static int blk_phys_contig_segment(struct request_queue 
*q, struct bio *bio,
return 0;
 }
 
+static inline 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 inline 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,
@@ -472,25 +522,7 @@ __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);
 
/* for making iterator happy */
bvec->bv_offset -= advance;
@@ -516,7 +548,7 @@ 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_segment_mp(bvec, bio, iter)
__blk_segment_map_sg(q, , sglist, , sg,
 , );
 
-- 
2.9.4

[PATCH v3 25/49] block: use bio_for_each_segment_mp() to map sg

[Ming Lei]

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

Signed-off-by: Ming Lei 
---
 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 c9b300f91fba..33353ed8c32e 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -439,6 +439,56 @@ static int blk_phys_contig_segment(struct request_queue 
*q, struct bio *bio,
return 0;
 }
 
+static inline 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 inline 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,
@@ -472,25 +522,7 @@ __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);
 
/* for making iterator happy */
bvec->bv_offset -= advance;
@@ -516,7 +548,7 @@ 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_segment_mp(bvec, bio, iter)
__blk_segment_map_sg(q, , sglist, , sg,
 , );
 
-- 
2.9.4