ext4: 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>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Acked-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20211018101130.1838532-27-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/ext4/super.c

@@ -4474,7 +4474,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		goto cantfind_ext4;
 
 	/* check blocks count against device size */
-	blocks_count = sb->s_bdev->bd_inode->i_size >> sb->s_blocksize_bits;
+	blocks_count = sb_bdev_nr_blocks(sb);
 	if (blocks_count && ext4_blocks_count(es) > blocks_count) {
 		ext4_msg(sb, KERN_WARNING, "bad geometry: block count %llu "
 		       "exceeds size of device (%llu blocks)",