ovl: don't fail copy up if no fileattr support on upper

Christoph Fritz is reporting that failure to copy up fileattr when upper
doesn't support fileattr or xattr results in a regression.

Return success in these failure cases; this reverts overlayfs to the old
behavior.

Add a pr_warn_once() in these cases to still let the user know about the
copy up failures.
Reported-by: Christoph Fritz <chf.fritz@googlemail.com>
Fixes: 72db8211 ("ovl: copy up sync/noatime fileattr flags")
Cc: <stable@vger.kernel.org> # v5.15
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/copy_up.c

@@ -157,7 +157,9 @@ static int ovl_copy_fileattr(struct inode *inode, struct path *old,
 	 */
 	if (oldfa.flags & OVL_PROT_FS_FLAGS_MASK) {
 		err = ovl_set_protattr(inode, new->dentry, &oldfa);
-		if (err)
+		if (err == -EPERM)
+			pr_warn_once("copying fileattr: no xattr on upper\n");
+		else if (err)
 			return err;
 	}
 
@@ -167,6 +169,14 @@ static int ovl_copy_fileattr(struct inode *inode, struct path *old,
 
 	err = ovl_real_fileattr_get(new, &newfa);
 	if (err) {
+		/*
+		 * Returning an error if upper doesn't support fileattr will
+		 * result in a regression, so revert to the old behavior.
+		 */
+		if (err == -ENOTTY || err == -EINVAL) {
+			pr_warn_once("copying fileattr: no support on upper\n");
+			return 0;
+		}
 		pr_warn("failed to retrieve upper fileattr (%pd2, err=%i)\n",
 			new->dentry, err);
 		return err;