btrfs: root->fs_info cleanup, add fs_info convenience variables

Hello Jeff Mahoney,

This is a semi-automatic email about new static checker warnings.

The patch b286384aac32: "btrfs: root->fs_info cleanup, add fs_info convenience variables" from Jun 22, 2016, leads to the following Smatch complaint:

fs/btrfs/export.c:238 btrfs_get_name()
warn: variable dereferenced before check 'inode' (see line 226)

fs/btrfs/export.c
225 struct inode *dir = d_inode(parent);

   226		struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
                                                         ^^^^^^^^^^^

New dereference.

227 struct btrfs_path *path;
228 struct btrfs_root *root = BTRFS_I(dir)->root;
229 struct btrfs_inode_ref *iref;
230 struct btrfs_root_ref *rref;
231 struct extent_buffer *leaf;
232 unsigned long name_ptr;
233 struct btrfs_key key;
234 int name_len;
235 int ret;
236 u64 ino;
237
238 if (!dir || !inode)

                             ^^^^^

Old code assumed it can be NULL.

239 return -EINVAL;
240

regards,
dan carpenter