From: Keith Busch <kbusch@kernel.org>

Individual bv_len's may not be a sector size.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
v3->v4:

  Use sector shift

  Add comment explaing the ALIGN_DOWN

  Use unsigned int type for counting bytes

 block/bounce.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/block/bounce.c b/block/bounce.c
index 8f7b6fe3b4db..f6ae21ec2a70 100644
--- a/block/bounce.c
+++ b/block/bounce.c

@@ -205,19 +205,25 @@ void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
 	int rw = bio_data_dir(*bio_orig);
 	struct bio_vec *to, from;
 	struct bvec_iter iter;
-	unsigned i = 0;
+	unsigned i = 0, bytes = 0;
 	bool bounce = false;
-	int sectors = 0;
+	int sectors;
 
 	bio_for_each_segment(from, *bio_orig, iter) {
 		if (i++ < BIO_MAX_VECS)
-			sectors += from.bv_len >> 9;
+			bytes += from.bv_len;
 		if (PageHighMem(from.bv_page))
 			bounce = true;
 	}
 	if (!bounce)
 		return;
 
+	/*
+	 * If the original has more than BIO_MAX_VECS biovecs, the total bytes
+	 * may not be block size aligned. Align down to ensure both sides of
+	 * the split bio are appropriately sized.
+	 */
+	sectors = ALIGN_DOWN(bytes, queue_logical_block_size(q)) >> SECTOR_SHIFT;
 	if (sectors < bio_sectors(*bio_orig)) {
 		bio = bio_split(*bio_orig, sectors, GFP_NOIO, &bounce_bio_split);
 		bio_chain(bio, *bio_orig);