[PATCH 1/5] block: fix gap checking in __bio_add_pc_page

[Christoph Hellwig <hch@lst.de>]

If we can add more data into an existing segment we do not create a gap
per definition, so move the check for a gap after the attempt to merge
into the segment.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/bio.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 683cbb40f051..6db39699aab9 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -722,18 +722,18 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
 			goto done;
 		}
 
+		if (page_is_mergeable(bvec, page, len, offset, false) &&
+		    can_add_page_to_seg(q, bvec, page, len, offset)) {
+			bvec->bv_len += len;
+			goto done;
+		}
+
 		/*
 		 * If the queue doesn't support SG gaps and adding this
 		 * offset would create a gap, disallow it.
 		 */
 		if (bvec_gap_to_prev(q, bvec, offset))
 			return 0;
-
-		if (page_is_mergeable(bvec, page, len, offset, false) &&
-		    can_add_page_to_seg(q, bvec, page, len, offset)) {
-			bvec->bv_len += len;
-			goto done;
-		}
 	}
 
 	if (bio_full(bio))
-- 
2.20.1