block/bounce: count bytes instead of sectors

Individual bv_len's may not be a sector size.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220610195830.3574005-8-kbusch@fb.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/bounce.c

@@ -205,19 +205,26 @@ 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;
 
+	/*
+	 * Individual bvecs might not be logical block aligned. Round down
+	 * the split size so that each bio is properly block size aligned,
+	 * even if we do not use the full hardware limits.
+	 */
+	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);