block: setup bi_phys_segments after splitting

The number of bio->bi_phys_segments is always obtained
during bio splitting, so it is natural to setup it
just after bio splitting, then we can avoid to compute
nr_segment again during merge.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 22 insertions, 7 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index c4e9c37f3e38..22293fdf6514 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -11,13 +11,16 @@
 
 static struct bio *blk_bio_discard_split(struct request_queue *q,
                                          struct bio *bio,
-                                         struct bio_set *bs)
+                                         struct bio_set *bs,
+                                         unsigned *nsegs)
 {
         unsigned int max_discard_sectors, granularity;
         int alignment;
         sector_t tmp;
         unsigned split_sectors;
 
+        *nsegs = 1;
+
         /* Zero-sector (unknown) and one-sector granularities are the same.  */
         granularity = max(q->limits.discard_granularity >> 9, 1U);
 
@@ -51,8 +54,11 @@ static struct bio *blk_bio_discard_split(struct request_queue *q,
 
 static struct bio *blk_bio_write_same_split(struct request_queue *q,
                                             struct bio *bio,
-                                            struct bio_set *bs)
+                                            struct bio_set *bs,
+                                            unsigned *nsegs)
 {
+        *nsegs = 1;
+
         if (!q->limits.max_write_same_sectors)
                 return NULL;
 
@@ -64,7 +70,8 @@ static struct bio *blk_bio_write_same_split(struct request_queue *q,
 
 static struct bio *blk_bio_segment_split(struct request_queue *q,
                                          struct bio *bio,
-                                         struct bio_set *bs)
+                                         struct bio_set *bs,
+                                         unsigned *segs)
 {
         struct bio_vec bv, bvprv, *bvprvp = NULL;
         struct bvec_iter iter;
@@ -106,22 +113,30 @@ new_segment:
                 sectors += bv.bv_len >> 9;
         }
 
+        *segs = nsegs;
         return NULL;
 split:
+        *segs = nsegs;
         return bio_split(bio, sectors, GFP_NOIO, bs);
 }
 
 void blk_queue_split(struct request_queue *q, struct bio **bio,
                      struct bio_set *bs)
 {
-        struct bio *split;
+        struct bio *split, *res;
+        unsigned nsegs;
 
         if ((*bio)->bi_rw & REQ_DISCARD)
-                split = blk_bio_discard_split(q, *bio, bs);
+                split = blk_bio_discard_split(q, *bio, bs, &nsegs);
         else if ((*bio)->bi_rw & REQ_WRITE_SAME)
-                split = blk_bio_write_same_split(q, *bio, bs);
+                split = blk_bio_write_same_split(q, *bio, bs, &nsegs);
         else
-                split = blk_bio_segment_split(q, *bio, q->bio_split);
+                split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs);
+
+        /* physical segments can be figured out during splitting */
+        res = split ? split : *bio;
+        res->bi_phys_segments = nsegs;
+        bio_set_flag(res, BIO_SEG_VALID);
 
         if (split) {
                 bio_chain(split, *bio);