reiserfs: use bdev_nr_bytes instead of open coding it

Use the proper helper to read the block device size and remove two
cargo culted checks that can't be false.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20211018101130.1838532-23-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/reiserfs/super.c

@@ -1986,9 +1986,7 @@ static int reiserfs_fill_super(struct super_block *s, void *data, int silent)
 	 * smaller than the filesystem. If the check fails then abort and
 	 * scream, because bad stuff will happen otherwise.
 	 */
-	if (s->s_bdev && s->s_bdev->bd_inode
-	    && i_size_read(s->s_bdev->bd_inode) <
-	    sb_block_count(rs) * sb_blocksize(rs)) {
+	if (bdev_nr_bytes(s->s_bdev) < sb_block_count(rs) * sb_blocksize(rs)) {
 		SWARN(silent, s, "", "Filesystem cannot be "
 		      "mounted because it is bigger than the device");
 		SWARN(silent, s, "", "You may need to run fsck "