[PATCH V9 14/19] block: enable multipage bvecs

[Ming Lei]

This patch pulls the trigger for multi-page bvecs.

Now any request queue which supports queue cluster will see multi-page
bvecs.

Cc: Christoph Hellwig <h...@lst.de>
Signed-off-by: Ming Lei <ming....@redhat.com>
---
 block/bio.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 6486722d4d4b..ed6df6f8e63d 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -767,12 +767,24 @@ bool __bio_try_merge_page(struct bio *bio, struct page 
*page,
 
        if (bio->bi_vcnt > 0) {
                struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
-
-               if (page == bv->bv_page && off == bv->bv_offset + bv->bv_len) {
-                       bv->bv_len += len;
-                       bio->bi_iter.bi_size += len;
-                       return true;
-               }
+               struct request_queue *q = NULL;
+
+               if (page == bv->bv_page && off == (bv->bv_offset + bv->bv_len)
+                               && (off + len) <= PAGE_SIZE)
+                       goto merge;
+
+               if (bio->bi_disk)
+                       q = bio->bi_disk->queue;
+
+               /* disable multi-page bvec too if cluster isn't enabled */
+               if (!q || !blk_queue_cluster(q) ||
+                   ((page_to_phys(bv->bv_page) + bv->bv_offset + bv->bv_len) !=
+                    (page_to_phys(page) + off)))
+                       return false;
+ merge:
+               bv->bv_len += len;
+               bio->bi_iter.bi_size += len;
+               return true;
        }
        return false;
 }
-- 
2.9.5