block: still try to split bio if the bvec crosses pages

Some device may set segment boundary as PAGE_SIZE - 1. If the bvec
crosses pages, and meantime its length is <= PAGE_SIZE, we still need
to split the bvec into 2 segments.

Fixes this issue by still splitting bio if the single bvec crosses
pages.
Reported-by: Nkernel test robot <lkp@intel.com>
Fixes: fa532287 (block: avoid blk_bio_segment_split for small I/O operations)
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/blk-merge.c

@@ -319,7 +319,8 @@ void __blk_queue_split(struct request_queue *q, struct bio **bio,
 		 */
 		if (!q->limits.chunk_sectors &&
 		    (*bio)->bi_vcnt == 1 &&
-		    (*bio)->bi_io_vec[0].bv_len <= PAGE_SIZE) {
+		    ((*bio)->bi_io_vec[0].bv_len +
+		     (*bio)->bi_io_vec[0].bv_offset) <= PAGE_SIZE) {
 			*nr_segs = 1;
 			break;
 		}