block_dev: Fixed direct I/O bio sector calculation

A direct I/O alignment must be always checked against the device blocks size,
but the I/O offset (bio->bi_iter.bi_sector must always use 512B sector unit, and
not the actual logical block size.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

fs/block_dev.c

@@ -226,7 +226,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 	bio.bi_max_vecs = nr_pages;
 	bio.bi_io_vec = vecs;
 	bio.bi_bdev = bdev;
-	bio.bi_iter.bi_sector = pos >> blkbits;
+	bio.bi_iter.bi_sector = pos >> 9;
 	bio.bi_private = current;
 	bio.bi_end_io = blkdev_bio_end_io_simple;
 
@@ -358,7 +358,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 
 	for (;;) {
 		bio->bi_bdev = bdev;
-		bio->bi_iter.bi_sector = pos >> blkbits;
+		bio->bi_iter.bi_sector = pos >> 9;
 		bio->bi_private = dio;
 		bio->bi_end_io = blkdev_bio_end_io;