ovl: encode non-indexed upper file handles

#include <linux/ratelimit.h>

#include "overlayfs.h"

/*

 * We only need to encode origin if there is a chance that the same object was

 * encoded pre copy up and then we need to stay consistent with the same

 * encoding also after copy up. If non-pure upper is not indexed, then it was

 * copied up before NFS export was enabled. In that case we don't need to worry

 * about staying consistent with pre copy up encoding and we encode an upper

 * file handle. Overlay root dentry is a private case of non-indexed upper.

 *

 * The following table summarizes the different file handle encodings used for

 * different overlay object types:

 *

 *  Object type		| Encoding

 * --------------------------------

 *  Pure upper		| U

 *  Non-indexed upper	| U

 *  Indexed upper	| L

 *  Non-upper		| L

 *

 * U = upper file handle

 * L = lower file handle

 */

static bool ovl_should_encode_origin(struct dentry *dentry)

{

	if (!ovl_dentry_lower(dentry))

		return false;

	/* Decoding a non-indexed upper from origin is not implemented */

	if (ovl_dentry_upper(dentry) &&

	    !ovl_test_flag(OVL_INDEX, d_inode(dentry)))

		return false;

	return true;

}

static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen)

{

	struct dentry *upper = ovl_dentry_upper(dentry);

	struct ovl_fh *fh = NULL;

	int err;

	/*

	 * On overlay with an upper layer, overlay root inode is encoded as

	 * an upper file handle, because upper root dir is not indexed.

	 */

	if (dentry == dentry->d_sb->s_root && upper)

	if (!ovl_should_encode_origin(dentry))

		origin = NULL;

	err = -EACCES;