[PATCH] block: return the correct first bvec when checking for gaps

[longli]

From: Long Li <longli@xxxxxxxxxxxxx>

After commit 07173c3ec276 ("block: enable multipage bvecs"), a bvec can
have multiple pages. But bio_will_gap() still assumes one page bvec while
checking for merging. This causes data corruption on drivers relying on
the correct merging on virt_boundary_mask.

Fix this by returning the bvec for multi-page bvec.

Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Cc: Pavel Begunkov <asml.silence@xxxxxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Cc: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 07173c3ec276 ("block: enable multipage bvecs")
Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
---
 include/linux/bio.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index a0b4cfdf62a4..e89242a53bbc 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -271,7 +271,7 @@ static inline void bio_clear_flag(struct bio *bio, unsigned int bit)
 
 static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
 {
-	*bv = bio_iovec(bio);
+	*bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
 }
 
 static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv)
-- 
2.17.1