reiserfs: use sb_bdev_nr_blocks

Use the sb_bdev_nr_blocks helper instead of open coding it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20211018101130.1838532-30-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/reiserfs/super.c

@@ -1199,9 +1199,7 @@ static int reiserfs_parse_options(struct super_block *s,
 
 			if (!strcmp(arg, "auto")) {
 				/* From JFS code, to auto-get the size. */
-				*blocks =
-				    i_size_read(s->s_bdev->bd_inode) >> s->
-				    s_blocksize_bits;
+				*blocks = sb_bdev_nr_blocks(s);
 			} else {
 				*blocks = simple_strtoul(arg, &p, 0);
 				if (*p != '\0') {