ovl: fold ovl_getxattr() into ovl_get_redirect_xattr()

This is a partial revert (with some cleanups) of commit 993a0b2a ("ovl:
Do not lose security.capability xattr over metadata file copy-up"), which
introduced ovl_getxattr() in the first place.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/util.c

@@ -882,49 +882,26 @@ bool ovl_is_metacopy_dentry(struct dentry *dentry)
 	return (oe->numlower > 1);
 }
 
-static ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value,
-			    size_t padding)
-{
-	ssize_t res;
-	char *buf = NULL;
-
-	res = vfs_getxattr(dentry, name, NULL, 0);
-	if (res < 0) {
-		if (res == -ENODATA || res == -EOPNOTSUPP)
-			return -ENODATA;
-		goto fail;
-	}
-
-	if (res != 0) {
-		buf = kzalloc(res + padding, GFP_KERNEL);
-		if (!buf)
-			return -ENOMEM;
-
-		res = vfs_getxattr(dentry, name, buf, res);
-		if (res < 0)
-			goto fail;
-	}
-	*value = buf;
-
-	return res;
-
-fail:
-	pr_warn_ratelimited("failed to get xattr %s: err=%zi)\n",
-			    name, res);
-	kfree(buf);
-	return res;
-}
-
 char *ovl_get_redirect_xattr(struct dentry *dentry, int padding)
 {
 	int res;
 	char *s, *next, *buf = NULL;
 
-	res = ovl_getxattr(dentry, OVL_XATTR_REDIRECT, &buf, padding + 1);
-	if (res == -ENODATA)
+	res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0);
+	if (res == -ENODATA || res == -EOPNOTSUPP)
 		return NULL;
 	if (res < 0)
-		return ERR_PTR(res);
+		goto fail;
+	if (res == 0)
+		goto invalid;
+
+	buf = kzalloc(res + padding + 1, GFP_KERNEL);
+	if (!buf)
+		return ERR_PTR(-ENOMEM);
+
+	res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res);
+	if (res < 0)
+		goto fail;
 	if (res == 0)
 		goto invalid;
 
@@ -943,6 +920,10 @@ char *ovl_get_redirect_xattr(struct dentry *dentry, int padding)
 invalid:
 	pr_warn_ratelimited("invalid redirect (%s)\n", buf);
 	res = -EINVAL;
+	goto err_free;
+fail:
+	pr_warn_ratelimited("failed to get redirect (%i)\n", res);
+err_free:
 	kfree(buf);
 	return ERR_PTR(res);
 }