From 76d110ca405bd327860d5d9f790a6ef2351cba04 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@google.com>
Date: Wed, 4 Jan 2023 12:59:55 -0800
Subject: [PATCH] Revert "fs: remove unused low-level mapping helpers"

This reverts commit d6e05a802452680e92c9ef83acc90e8c21066640.
---
 include/linux/mnt_idmapping.h | 56 +++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/include/linux/mnt_idmapping.h b/include/linux/mnt_idmapping.h
index 0c6ab3f4c952..60341cd33ccc 100644
--- a/include/linux/mnt_idmapping.h
+++ b/include/linux/mnt_idmapping.h
@@ -13,6 +13,62 @@ struct user_namespace;
  */
 extern struct user_namespace init_user_ns;
 
+/**
+ * kuid_into_mnt - map a kuid down into a mnt_userns
+ * @mnt_userns: user namespace of the relevant mount
+ * @kuid: kuid to be mapped
+ *
+ * Return: @kuid mapped according to @mnt_userns.
+ * If @kuid has no mapping INVALID_UID is returned.
+ */
+static inline kuid_t kuid_into_mnt(struct user_namespace *mnt_userns,
+				   kuid_t kuid)
+{
+	return make_kuid(mnt_userns, __kuid_val(kuid));
+}
+
+/**
+ * kgid_into_mnt - map a kgid down into a mnt_userns
+ * @mnt_userns: user namespace of the relevant mount
+ * @kgid: kgid to be mapped
+ *
+ * Return: @kgid mapped according to @mnt_userns.
+ * If @kgid has no mapping INVALID_GID is returned.
+ */
+static inline kgid_t kgid_into_mnt(struct user_namespace *mnt_userns,
+				   kgid_t kgid)
+{
+	return make_kgid(mnt_userns, __kgid_val(kgid));
+}
+
+/**
+ * kuid_from_mnt - map a kuid up into a mnt_userns
+ * @mnt_userns: user namespace of the relevant mount
+ * @kuid: kuid to be mapped
+ *
+ * Return: @kuid mapped up according to @mnt_userns.
+ * If @kuid has no mapping INVALID_UID is returned.
+ */
+static inline kuid_t kuid_from_mnt(struct user_namespace *mnt_userns,
+				   kuid_t kuid)
+{
+	return KUIDT_INIT(from_kuid(mnt_userns, kuid));
+}
+
+/**
+ * kgid_from_mnt - map a kgid up into a mnt_userns
+ * @mnt_userns: user namespace of the relevant mount
+ * @kgid: kgid to be mapped
+ *
+ * Return: @kgid mapped up according to @mnt_userns.
+ * If @kgid has no mapping INVALID_GID is returned.
+ */
+static inline kgid_t kgid_from_mnt(struct user_namespace *mnt_userns,
+				   kgid_t kgid)
+{
+	return KGIDT_INIT(from_kgid(mnt_userns, kgid));
+}
+
 /**
  * initial_idmapping - check whether this is the initial mapping
  * @ns: idmapping to check