ovl: hash non-indexed dir by upper inode for NFS export

Non-indexed upper dirs are encoded as upper file handles. When NFS export
is enabled, hash non-indexed directory inodes by upper inode, so we can
find them in inode cache using the decoded upper inode.

When NFS export is disabled, directories are not indexed on copy up, so
hash non-indexed directory inodes by origin inode, the same hash key
that is used before copy up.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/inode.c

@@ -665,6 +665,7 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
 			    struct dentry *lowerdentry, struct dentry *index,
 			    unsigned int numlower)
 {
+	struct ovl_fs *ofs = sb->s_fs_info;
 	struct inode *realinode = upperdentry ? d_inode(upperdentry) : NULL;
 	struct inode *inode;
 	/* Already indexed or could be indexed on copy up? */
@@ -684,9 +685,10 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
 	 * Hash non-dir that is or could be indexed by origin inode.
 	 * Hash dir that is or could be merged by origin inode.
 	 * Hash pure upper and non-indexed non-dir by upper inode.
+	 * Hash non-indexed dir by upper inode for NFS export.
 	 */
 	is_dir = S_ISDIR(realinode->i_mode);
-	if (is_dir)
+	if (is_dir && (indexed || !sb->s_export_op || !ofs->upper_mnt))
 		origin = lowerdentry;
 
 	if (upperdentry || origin) {