[PATCH V8 13/18] 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 <hch@xxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 block/bio.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 6486722d4d4b..b2ce42e89076 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -767,12 +767,23 @@ 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)
+			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