Merge tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping

Pull vfs idmapping updates from Christian Brauner:

 - Last cycle we introduced the dedicated struct mnt_idmap type for
   mount idmapping and the required infrastucture in 256c8aed2b42 ("fs:
   introduce dedicated idmap type for mounts"). As promised in last
   cycle's pull request message this converts everything to rely on
   struct mnt_idmap.

   Currently we still pass around the plain namespace that was attached
   to a mount. This is in general pretty convenient but it makes it easy
   to conflate namespaces that are relevant on the filesystem with
   namespaces that are relevant on the mount level. Especially for
   non-vfs developers without detailed knowledge in this area this was a
   potential source for bugs.

   This finishes the conversion. Instead of passing the plain namespace
   around this updates all places that currently take a pointer to a
   mnt_userns with a pointer to struct mnt_idmap.

   Now that the conversion is done all helpers down to the really
   low-level helpers only accept a struct mnt_idmap argument instead of
   two namespace arguments.

   Conflating mount and other idmappings will now cause the compiler to
   complain loudly thus eliminating the possibility of any bugs. This
   makes it impossible for filesystem developers to mix up mount and
   filesystem idmappings as they are two distinct types and require
   distinct helpers that cannot be used interchangeably.

   Everything associated with struct mnt_idmap is moved into a single
   separate file. With that change no code can poke around in struct
   mnt_idmap. It can only be interacted with through dedicated helpers.
   That means all filesystems are and all of the vfs is completely
   oblivious to the actual implementation of idmappings.

   We are now also able to extend struct mnt_idmap as we see fit. For
   example, we can decouple it completely from namespaces for users that
   don't require or don't want to use them at all. We can also extend
   the concept of idmappings so we can cover filesystem specific
   requirements.

   In combination with the vfs{g,u}id_t work we finished in v6.2 this
   makes this feature substantially more robust and thus difficult to
   implement wrong by a given filesystem and also protects the vfs.

 - Enable idmapped mounts for tmpfs and fulfill a longstanding request.

   A long-standing request from users had been to make it possible to
   create idmapped mounts for tmpfs. For example, to share the host's
   tmpfs mount between multiple sandboxes. This is a prerequisite for
   some advanced Kubernetes cases. Systemd also has a range of use-cases
   to increase service isolation. And there are more users of this.

   However, with all of the other work going on this was way down on the
   priority list but luckily someone other than ourselves picked this
   up.

   As usual the patch is tiny as all the infrastructure work had been
   done multiple kernel releases ago. In addition to all the tests that
   we already have I requested that Rodrigo add a dedicated tmpfs
   testsuite for idmapped mounts to xfstests. It is to be included into
   xfstests during the v6.3 development cycle. This should add a slew of
   additional tests.

* tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping: (26 commits)
  shmem: support idmapped mounts for tmpfs
  fs: move mnt_idmap
  fs: port vfs{g,u}id helpers to mnt_idmap
  fs: port fs{g,u}id helpers to mnt_idmap
  fs: port i_{g,u}id_into_vfs{g,u}id() to mnt_idmap
  fs: port i_{g,u}id_{needs_}update() to mnt_idmap
  quota: port to mnt_idmap
  fs: port privilege checking helpers to mnt_idmap
  fs: port inode_owner_or_capable() to mnt_idmap
  fs: port inode_init_owner() to mnt_idmap
  fs: port acl to mnt_idmap
  fs: port xattr to mnt_idmap
  fs: port ->permission() to pass mnt_idmap
  fs: port ->fileattr_set() to pass mnt_idmap
  fs: port ->set_acl() to pass mnt_idmap
  fs: port ->get_acl() to pass mnt_idmap
  fs: port ->tmpfile() to pass mnt_idmap
  fs: port ->rename() to pass mnt_idmap
  fs: port ->mknod() to pass mnt_idmap
  fs: port ->mkdir() to pass mnt_idmap
  ...

15 files changed, 205 insertions, 384 deletions

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 65efb74c3585..03c2a613ad40 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -42,6 +42,7 @@ struct inode;
 struct dentry;
 struct task_struct;
 struct user_namespace;
+struct mnt_idmap;
 
 extern const kernel_cap_t __cap_empty_set;
 extern const kernel_cap_t __cap_init_eff_set;
@@ -248,9 +249,9 @@ static inline bool ns_capable_setid(struct user_namespace *ns, int cap)
 }
 #endif /* CONFIG_MULTIUSER */
 bool privileged_wrt_inode_uidgid(struct user_namespace *ns,
-				 struct user_namespace *mnt_userns,
+				 struct mnt_idmap *idmap,
 				 const struct inode *inode);
-bool capable_wrt_inode_uidgid(struct user_namespace *mnt_userns,
+bool capable_wrt_inode_uidgid(struct mnt_idmap *idmap,
 			      const struct inode *inode, int cap);
 extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
 extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns);
@@ -271,11 +272,11 @@ static inline bool checkpoint_restore_ns_capable(struct user_namespace *ns)
 }
 
 /* audit system wants to get cap info from files as well */
-int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
+int get_vfs_caps_from_disk(struct mnt_idmap *idmap,
 			   const struct dentry *dentry,
 			   struct cpu_vfs_cap_data *cpu_caps);
 
-int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
+int cap_convert_nscap(struct mnt_idmap *idmap, struct dentry *dentry,
 		      const void **ivalue, size_t size);
 
 #endif /* !_LINUX_CAPABILITY_H */
diff --git a/include/linux/evm.h b/include/linux/evm.h
index 7a9ee2157f69..7dc1ee74169f 100644
--- a/include/linux/evm.h
+++ b/include/linux/evm.h
@@ -21,34 +21,34 @@ extern enum integrity_status evm_verifyxattr(struct dentry *dentry,
 					     void *xattr_value,
 					     size_t xattr_value_len,
 					     struct integrity_iint_cache *iint);
-extern int evm_inode_setattr(struct user_namespace *mnt_userns,
+extern int evm_inode_setattr(struct mnt_idmap *idmap,
 			     struct dentry *dentry, struct iattr *attr);
 extern void evm_inode_post_setattr(struct dentry *dentry, int ia_valid);
-extern int evm_inode_setxattr(struct user_namespace *mnt_userns,
+extern int evm_inode_setxattr(struct mnt_idmap *idmap,
 			      struct dentry *dentry, const char *name,
 			      const void *value, size_t size);
 extern void evm_inode_post_setxattr(struct dentry *dentry,
 				    const char *xattr_name,
 				    const void *xattr_value,
 				    size_t xattr_value_len);
-extern int evm_inode_removexattr(struct user_namespace *mnt_userns,
+extern int evm_inode_removexattr(struct mnt_idmap *idmap,
 				 struct dentry *dentry, const char *xattr_name);
 extern void evm_inode_post_removexattr(struct dentry *dentry,
 				       const char *xattr_name);
-static inline void evm_inode_post_remove_acl(struct user_namespace *mnt_userns,
+static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
 					     struct dentry *dentry,
 					     const char *acl_name)
 {
 	evm_inode_post_removexattr(dentry, acl_name);
 }
-extern int evm_inode_set_acl(struct user_namespace *mnt_userns,
+extern int evm_inode_set_acl(struct mnt_idmap *idmap,
 			     struct dentry *dentry, const char *acl_name,
 			     struct posix_acl *kacl);
-static inline int evm_inode_remove_acl(struct user_namespace *mnt_userns,
+static inline int evm_inode_remove_acl(struct mnt_idmap *idmap,
 				       struct dentry *dentry,
 				       const char *acl_name)
 {
-	return evm_inode_set_acl(mnt_userns, dentry, acl_name, NULL);
+	return evm_inode_set_acl(idmap, dentry, acl_name, NULL);
 }
 static inline void evm_inode_post_set_acl(struct dentry *dentry,
 					  const char *acl_name,
@@ -90,7 +90,7 @@ static inline enum integrity_status evm_verifyxattr(struct dentry *dentry,
 }
 #endif
 
-static inline int evm_inode_setattr(struct user_namespace *mnt_userns,
+static inline int evm_inode_setattr(struct mnt_idmap *idmap,
 				    struct dentry *dentry, struct iattr *attr)
 {
 	return 0;
@@ -101,7 +101,7 @@ static inline void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
 	return;
 }
 
-static inline int evm_inode_setxattr(struct user_namespace *mnt_userns,
+static inline int evm_inode_setxattr(struct mnt_idmap *idmap,
 				     struct dentry *dentry, const char *name,
 				     const void *value, size_t size)
 {
@@ -116,7 +116,7 @@ static inline void evm_inode_post_setxattr(struct dentry *dentry,
 	return;
 }
 
-static inline int evm_inode_removexattr(struct user_namespace *mnt_userns,
+static inline int evm_inode_removexattr(struct mnt_idmap *idmap,
 					struct dentry *dentry,
 					const char *xattr_name)
 {
@@ -129,21 +129,21 @@ static inline void evm_inode_post_removexattr(struct dentry *dentry,
 	return;
 }
 
-static inline void evm_inode_post_remove_acl(struct user_namespace *mnt_userns,
+static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
 					     struct dentry *dentry,
 					     const char *acl_name)
 {
 	return;
 }
 
-static inline int evm_inode_set_acl(struct user_namespace *mnt_userns,
+static inline int evm_inode_set_acl(struct mnt_idmap *idmap,
 				    struct dentry *dentry, const char *acl_name,
 				    struct posix_acl *kacl)
 {
 	return 0;
 }
 
-static inline int evm_inode_remove_acl(struct user_namespace *mnt_userns,
+static inline int evm_inode_remove_acl(struct mnt_idmap *idmap,
 				       struct dentry *dentry,
 				       const char *acl_name)
 {
diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
index 9e37e063ac69..47c05a9851d0 100644
--- a/include/linux/fileattr.h
+++ b/include/linux/fileattr.h
@@ -53,7 +53,7 @@ static inline bool fileattr_has_fsx(const struct fileattr *fa)
 }
 
 int vfs_fileattr_get(struct dentry *dentry, struct fileattr *fa);
-int vfs_fileattr_set(struct user_namespace *mnt_userns, struct dentry *dentry,
+int vfs_fileattr_set(struct mnt_idmap *idmap, struct dentry *dentry,
 		     struct fileattr *fa);
 
 #endif /* _LINUX_FILEATTR_H */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 006278d84d2f..2acc46fb5f97 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1296,22 +1296,22 @@ static inline void i_gid_write(struct inode *inode, gid_t gid)
 }
 
 /**
- * i_uid_into_vfsuid - map an inode's i_uid down into a mnt_userns
- * @mnt_userns: user namespace of the mount the inode was found from
+ * i_uid_into_vfsuid - map an inode's i_uid down according to an idmapping
+ * @idmap: idmap of the mount the inode was found from
  * @inode: inode to map
  *
- * Return: whe inode's i_uid mapped down according to @mnt_userns.
+ * Return: whe inode's i_uid mapped down according to @idmap.
  * If the inode's i_uid has no mapping INVALID_VFSUID is returned.
  */
-static inline vfsuid_t i_uid_into_vfsuid(struct user_namespace *mnt_userns,
+static inline vfsuid_t i_uid_into_vfsuid(struct mnt_idmap *idmap,
 					 const struct inode *inode)
 {
-	return make_vfsuid(mnt_userns, i_user_ns(inode), inode->i_uid);
+	return make_vfsuid(idmap, i_user_ns(inode), inode->i_uid);
 }
 
 /**
  * i_uid_needs_update - check whether inode's i_uid needs to be updated
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  * @attr: the new attributes of @inode
  * @inode: the inode to update
  *
@@ -1320,50 +1320,50 @@ static inline vfsuid_t i_uid_into_vfsuid(struct user_namespace *mnt_userns,
  *
  * Return: true if @inode's i_uid field needs to be updated, false if not.
  */
-static inline bool i_uid_needs_update(struct user_namespace *mnt_userns,
+static inline bool i_uid_needs_update(struct mnt_idmap *idmap,
 				      const struct iattr *attr,
 				      const struct inode *inode)
 {
 	return ((attr->ia_valid & ATTR_UID) &&
 		!vfsuid_eq(attr->ia_vfsuid,
-			   i_uid_into_vfsuid(mnt_userns, inode)));
+			   i_uid_into_vfsuid(idmap, inode)));
 }
 
 /**
  * i_uid_update - update @inode's i_uid field
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  * @attr: the new attributes of @inode
  * @inode: the inode to update
  *
  * Safely update @inode's i_uid field translating the vfsuid of any idmapped
  * mount into the filesystem kuid.
  */
-static inline void i_uid_update(struct user_namespace *mnt_userns,
+static inline void i_uid_update(struct mnt_idmap *idmap,
 				const struct iattr *attr,
 				struct inode *inode)
 {
 	if (attr->ia_valid & ATTR_UID)
-		inode->i_uid = from_vfsuid(mnt_userns, i_user_ns(inode),
+		inode->i_uid = from_vfsuid(idmap, i_user_ns(inode),
 					   attr->ia_vfsuid);
 }
 
 /**
- * i_gid_into_vfsgid - map an inode's i_gid down into a mnt_userns
- * @mnt_userns: user namespace of the mount the inode was found from
+ * i_gid_into_vfsgid - map an inode's i_gid down according to an idmapping
+ * @idmap: idmap of the mount the inode was found from
  * @inode: inode to map
  *
- * Return: the inode's i_gid mapped down according to @mnt_userns.
+ * Return: the inode's i_gid mapped down according to @idmap.
  * If the inode's i_gid has no mapping INVALID_VFSGID is returned.
  */
-static inline vfsgid_t i_gid_into_vfsgid(struct user_namespace *mnt_userns,
+static inline vfsgid_t i_gid_into_vfsgid(struct mnt_idmap *idmap,
 					 const struct inode *inode)
 {
-	return make_vfsgid(mnt_userns, i_user_ns(inode), inode->i_gid);
+	return make_vfsgid(idmap, i_user_ns(inode), inode->i_gid);
 }
 
 /**
  * i_gid_needs_update - check whether inode's i_gid needs to be updated
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  * @attr: the new attributes of @inode
  * @inode: the inode to update
  *
@@ -1372,83 +1372,83 @@ static inline vfsgid_t i_gid_into_vfsgid(struct user_namespace *mnt_userns,
  *
  * Return: true if @inode's i_gid field needs to be updated, false if not.
  */
-static inline bool i_gid_needs_update(struct user_namespace *mnt_userns,
+static inline bool i_gid_needs_update(struct mnt_idmap *idmap,
 				      const struct iattr *attr,
 				      const struct inode *inode)
 {
 	return ((attr->ia_valid & ATTR_GID) &&
 		!vfsgid_eq(attr->ia_vfsgid,
-			   i_gid_into_vfsgid(mnt_userns, inode)));
+			   i_gid_into_vfsgid(idmap, inode)));
 }
 
 /**
  * i_gid_update - update @inode's i_gid field
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  * @attr: the new attributes of @inode
  * @inode: the inode to update
  *
  * Safely update @inode's i_gid field translating the vfsgid of any idmapped
  * mount into the filesystem kgid.
  */
-static inline void i_gid_update(struct user_namespace *mnt_userns,
+static inline void i_gid_update(struct mnt_idmap *idmap,
 				const struct iattr *attr,
 				struct inode *inode)
 {
 	if (attr->ia_valid & ATTR_GID)
-		inode->i_gid = from_vfsgid(mnt_userns, i_user_ns(inode),
+		inode->i_gid = from_vfsgid(idmap, i_user_ns(inode),
 					   attr->ia_vfsgid);
 }
 
 /**
  * inode_fsuid_set - initialize inode's i_uid field with callers fsuid
  * @inode: inode to initialize
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  *
  * Initialize the i_uid field of @inode. If the inode was found/created via
- * an idmapped mount map the caller's fsuid according to @mnt_users.
+ * an idmapped mount map the caller's fsuid according to @idmap.
  */
 static inline void inode_fsuid_set(struct inode *inode,
-				   struct user_namespace *mnt_userns)
+				   struct mnt_idmap *idmap)
 {
-	inode->i_uid = mapped_fsuid(mnt_userns, i_user_ns(inode));
+	inode->i_uid = mapped_fsuid(idmap, i_user_ns(inode));
 }
 
 /**
  * inode_fsgid_set - initialize inode's i_gid field with callers fsgid
  * @inode: inode to initialize
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  *
  * Initialize the i_gid field of @inode. If the inode was found/created via
- * an idmapped mount map the caller's fsgid according to @mnt_users.
+ * an idmapped mount map the caller's fsgid according to @idmap.
  */
 static inline void inode_fsgid_set(struct inode *inode,
-				   struct user_namespace *mnt_userns)
+				   struct mnt_idmap *idmap)
 {
-	inode->i_gid = mapped_fsgid(mnt_userns, i_user_ns(inode));
+	inode->i_gid = mapped_fsgid(idmap, i_user_ns(inode));
 }
 
 /**
  * fsuidgid_has_mapping() - check whether caller's fsuid/fsgid is mapped
  * @sb: the superblock we want a mapping in
- * @mnt_userns: user namespace of the relevant mount
+ * @idmap: idmap of the relevant mount
  *
  * Check whether the caller's fsuid and fsgid have a valid mapping in the
  * s_user_ns of the superblock @sb. If the caller is on an idmapped mount map
- * the caller's fsuid and fsgid according to the @mnt_userns first.
+ * the caller's fsuid and fsgid according to the @idmap first.
  *
  * Return: true if fsuid and fsgid is mapped, false if not.
  */
 static inline bool fsuidgid_has_mapping(struct super_block *sb,
-					struct user_namespace *mnt_userns)
+					struct mnt_idmap *idmap)
 {
 	struct user_namespace *fs_userns = sb->s_user_ns;
 	kuid_t kuid;
 	kgid_t kgid;
 
-	kuid = mapped_fsuid(mnt_userns, fs_userns);
+	kuid = mapped_fsuid(idmap, fs_userns);
 	if (!uid_valid(kuid))
 		return false;
-	kgid = mapped_fsgid(mnt_userns, fs_userns);
+	kgid = mapped_fsgid(idmap, fs_userns);
 	if (!gid_valid(kgid))
 		return false;
 	return kuid_has_mapping(fs_userns, kuid) &&
@@ -1602,42 +1602,42 @@ static inline bool sb_start_intwrite_trylock(struct super_block *sb)
 	return __sb_start_write_trylock(sb, SB_FREEZE_FS);
 }
 
-bool inode_owner_or_capable(struct user_namespace *mnt_userns,
+bool inode_owner_or_capable(struct mnt_idmap *idmap,
 			    const struct inode *inode);
 
 /*
  * VFS helper functions..
  */
-int vfs_create(struct user_namespace *, struct inode *,
+int vfs_create(struct mnt_idmap *, struct inode *,
 	       struct dentry *, umode_t, bool);
-int vfs_mkdir(struct user_namespace *, struct inode *,
+int vfs_mkdir(struct mnt_idmap *, struct inode *,
 	      struct dentry *, umode_t);
-int vfs_mknod(struct user_namespace *, struct inode *, struct dentry *,
+int vfs_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
               umode_t, dev_t);
-int vfs_symlink(struct user_namespace *, struct inode *,
+int vfs_symlink(struct mnt_idmap *, struct inode *,
 		struct dentry *, const char *);
-int vfs_link(struct dentry *, struct user_namespace *, struct inode *,
+int vfs_link(struct dentry *, struct mnt_idmap *, struct inode *,
 	     struct dentry *, struct inode **);
-int vfs_rmdir(struct user_namespace *, struct inode *, struct dentry *);
-int vfs_unlink(struct user_namespace *, struct inode *, struct dentry *,
+int vfs_rmdir(struct mnt_idmap *, struct inode *, struct dentry *);
+int vfs_unlink(struct mnt_idmap *, struct inode *, struct dentry *,
 	       struct inode **);
 
 /**
  * struct renamedata - contains all information required for renaming
- * @old_mnt_userns:    old user namespace of the mount the inode was found from
+ * @old_mnt_idmap:     idmap of the old mount the inode was found from
  * @old_dir:           parent of source
  * @old_dentry:                source
- * @new_mnt_userns:    new user namespace of the mount the inode was found from
+ * @new_mnt_idmap:     idmap of the new mount the inode was found from
  * @new_dir:           parent of destination
  * @new_dentry:                destination
  * @delegated_inode:   returns an inode needing a delegation break
  * @flags:             rename flags
  */
 struct renamedata {
-	struct user_namespace *old_mnt_userns;
+	struct mnt_idmap *old_mnt_idmap;
 	struct inode *old_dir;
 	struct dentry *old_dentry;
-	struct user_namespace *new_mnt_userns;
+	struct mnt_idmap *new_mnt_idmap;
 	struct inode *new_dir;
 	struct dentry *new_dentry;
 	struct inode **delegated_inode;
@@ -1646,14 +1646,14 @@ struct renamedata {
 
 int vfs_rename(struct renamedata *);
 
-static inline int vfs_whiteout(struct user_namespace *mnt_userns,
+static inline int vfs_whiteout(struct mnt_idmap *idmap,
 			       struct inode *dir, struct dentry *dentry)
 {
-	return vfs_mknod(mnt_userns, dir, dentry, S_IFCHR | WHITEOUT_MODE,
+	return vfs_mknod(idmap, dir, dentry, S_IFCHR | WHITEOUT_MODE,
 			 WHITEOUT_DEV);
 }
 
-struct file *vfs_tmpfile_open(struct user_namespace *mnt_userns,
+struct file *vfs_tmpfile_open(struct mnt_idmap *idmap,
 			const struct path *parentpath,
 			umode_t mode, int open_flag, const struct cred *cred);
 
@@ -1677,10 +1677,10 @@ extern long compat_ptr_ioctl(struct file *file, unsigned int cmd,
 /*
  * VFS file helper functions.
  */
-void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode,
+void inode_init_owner(struct mnt_idmap *idmap, struct inode *inode,
 		      const struct inode *dir, umode_t mode);
 extern bool may_open_dev(const struct path *path);
-umode_t mode_strip_sgid(struct user_namespace *mnt_userns,
+umode_t mode_strip_sgid(struct mnt_idmap *idmap,
 			const struct inode *dir, umode_t mode);
 
 /*
@@ -1798,27 +1798,26 @@ struct file_operations {
 struct inode_operations {
 	struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
 	const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
-	int (*permission) (struct user_namespace *, struct inode *, int);
+	int (*permission) (struct mnt_idmap *, struct inode *, int);
 	struct posix_acl * (*get_inode_acl)(struct inode *, int, bool);
 
 	int (*readlink) (struct dentry *, char __user *,int);
 
-	int (*create) (struct user_namespace *, struct inode *,struct dentry *,
+	int (*create) (struct mnt_idmap *, struct inode *,struct dentry *,
 		       umode_t, bool);
 	int (*link) (struct dentry *,struct inode *,struct dentry *);
 	int (*unlink) (struct inode *,struct dentry *);
-	int (*symlink) (struct user_namespace *, struct inode *,struct dentry *,
+	int (*symlink) (struct mnt_idmap *, struct inode *,struct dentry *,
 			const char *);
-	int (*mkdir) (struct user_namespace *, struct inode *,struct dentry *,
+	int (*mkdir) (struct mnt_idmap *, struct inode *,struct dentry *,
 		      umode_t);
 	int (*rmdir) (struct inode *,struct dentry *);
-	int (*mknod) (struct user_namespace *, struct inode *,struct dentry *,
+	int (*mknod) (struct mnt_idmap *, struct inode *,struct dentry *,
 		      umode_t,dev_t);
-	int (*rename) (struct user_namespace *, struct inode *, struct dentry *,
+	int (*rename) (struct mnt_idmap *, struct inode *, struct dentry *,
 			struct inode *, struct dentry *, unsigned int);
-	int (*setattr) (struct user_namespace *, struct dentry *,
-			struct iattr *);
-	int (*getattr) (struct user_namespace *, const struct path *,
+	int (*setattr) (struct mnt_idmap *, struct dentry *, struct iattr *);
+	int (*getattr) (struct mnt_idmap *, const struct path *,
 			struct kstat *, u32, unsigned int);
 	ssize_t (*listxattr) (struct dentry *, char *, size_t);
 	int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
@@ -1827,13 +1826,13 @@ struct inode_operations {
 	int (*atomic_open)(struct inode *, struct dentry *,
 			   struct file *, unsigned open_flag,
 			   umode_t create_mode);
-	int (*tmpfile) (struct user_namespace *, struct inode *,
+	int (*tmpfile) (struct mnt_idmap *, struct inode *,
 			struct file *, umode_t);
-	struct posix_acl *(*get_acl)(struct user_namespace *, struct dentry *,
+	struct posix_acl *(*get_acl)(struct mnt_idmap *, struct dentry *,
 				     int);
-	int (*set_acl)(struct user_namespace *, struct dentry *,
+	int (*set_acl)(struct mnt_idmap *, struct dentry *,
 		       struct posix_acl *, int);
-	int (*fileattr_set)(struct user_namespace *mnt_userns,
+	int (*fileattr_set)(struct mnt_idmap *idmap,
 			    struct dentry *dentry, struct fileattr *fa);
 	int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa);
 } ____cacheline_aligned;
@@ -1987,11 +1986,11 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags
 #define IS_WHITEOUT(inode)	(S_ISCHR(inode->i_mode) && \
 				 (inode)->i_rdev == WHITEOUT_DEV)
 
-static inline bool HAS_UNMAPPED_ID(struct user_namespace *mnt_userns,
+static inline bool HAS_UNMAPPED_ID(struct mnt_idmap *idmap,
 				   struct inode *inode)
 {
-	return !vfsuid_valid(i_uid_into_vfsuid(mnt_userns, inode)) ||
-	       !vfsgid_valid(i_gid_into_vfsgid(mnt_userns, inode));
+	return !vfsuid_valid(i_uid_into_vfsuid(idmap, inode)) ||
+	       !vfsgid_valid(i_gid_into_vfsgid(idmap, inode));
 }
 
 static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
@@ -2296,11 +2295,6 @@ struct filename {
 };
 static_assert(offsetof(struct filename, iname) % sizeof(long) == 0);
 
-static inline struct user_namespace *file_mnt_user_ns(struct file *file)
-{
-	return mnt_user_ns(file->f_path.mnt);
-}
-
 static inline struct mnt_idmap *file_mnt_idmap(struct file *file)
 {
 	return mnt_idmap(file->f_path.mnt);
@@ -2320,7 +2314,7 @@ static inline bool is_idmapped_mnt(const struct vfsmount *mnt)
 }
 
 extern long vfs_truncate(const struct path *, loff_t);
-int do_truncate(struct user_namespace *, struct dentry *, loff_t start,
+int do_truncate(struct mnt_idmap *, struct dentry *, loff_t start,
 		unsigned int time_attrs, struct file *filp);
 extern int vfs_fallocate(struct file *file, int mode, loff_t offset,
 			loff_t len);
@@ -2475,21 +2469,21 @@ static inline int bmap(struct inode *inode,  sector_t *block)
 }
 #endif
 
-int notify_change(struct user_namespace *, struct dentry *,
+int notify_change(struct mnt_idmap *, struct dentry *,
 		  struct iattr *, struct inode **);
-int inode_permission(struct user_namespace *, struct inode *, int);
-int generic_permission(struct user_namespace *, struct inode *, int);
+int inode_permission(struct mnt_idmap *, struct inode *, int);
+int generic_permission(struct mnt_idmap *, struct inode *, int);
 static inline int file_permission(struct file *file, int mask)
 {
-	return inode_permission(file_mnt_user_ns(file),
+	return inode_permission(file_mnt_idmap(file),
 				file_inode(file), mask);
 }
 static inline int path_permission(const struct path *path, int mask)
 {
-	return inode_permission(mnt_user_ns(path->mnt),
+	return inode_permission(mnt_idmap(path->mnt),
 				d_inode(path->dentry), mask);
 }
-int __check_sticky(struct user_namespace *mnt_userns, struct inode *dir,
+int __check_sticky(struct mnt_idmap *idmap, struct inode *dir,
 		   struct inode *inode);
 
 static inline bool execute_ok(struct inode *inode)
@@ -2677,7 +2671,7 @@ extern void __destroy_inode(struct inode *);
 extern struct inode *new_inode_pseudo(struct super_block *sb);
 extern struct inode *new_inode(struct super_block *sb);
 extern void free_inode_nonrcu(struct inode *inode);
-extern int setattr_should_drop_suidgid(struct user_namespace *, struct inode *);
+extern int setattr_should_drop_suidgid(struct mnt_idmap *, struct inode *);
 extern int file_remove_privs(struct file *);
 
 /*
@@ -2836,7 +2830,7 @@ extern void page_put_link(void *);
 extern int page_symlink(struct inode *inode, const char *symname, int len);
 extern const struct inode_operations page_symlink_inode_operations;
 extern void kfree_link(void *);
-void generic_fillattr(struct user_namespace *, struct inode *, struct kstat *);
+void generic_fillattr(struct mnt_idmap *, struct inode *, struct kstat *);
 void generic_fill_statx_attr(struct inode *inode, struct kstat *stat);
 extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int);
 extern int vfs_getattr(const struct path *, struct kstat *, u32, unsigned int);
@@ -2887,9 +2881,9 @@ extern int dcache_dir_open(struct inode *, struct file *);
 extern int dcache_dir_close(struct inode *, struct file *);
 extern loff_t dcache_dir_lseek(struct file *, loff_t, int);
 extern int dcache_readdir(struct file *, struct dir_context *);
-extern int simple_setattr(struct user_namespace *, struct dentry *,
+extern int simple_setattr(struct mnt_idmap *, struct dentry *,
 			  struct iattr *);
-extern int simple_getattr(struct user_namespace *, const struct path *,
+extern int simple_getattr(struct mnt_idmap *, const struct path *,
 			  struct kstat *, u32, unsigned int);
 extern int simple_statfs(struct dentry *, struct kstatfs *);
 extern int simple_open(struct inode *inode, struct file *file);
@@ -2898,7 +2892,7 @@ extern int simple_unlink(struct inode *, struct dentry *);
 extern int simple_rmdir(struct inode *, struct dentry *);
 extern int simple_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
 				  struct inode *new_dir, struct dentry *new_dentry);
-extern int simple_rename(struct user_namespace *, struct inode *,
+extern int simple_rename(struct mnt_idmap *, struct inode *,
 			 struct dentry *, struct inode *, struct dentry *,
 			 unsigned int);
 extern void simple_recursive_removal(struct dentry *,
@@ -2940,11 +2934,11 @@ extern int generic_check_addressable(unsigned, u64);
 
 extern void generic_set_encrypted_ci_d_ops(struct dentry *dentry);
 
-int may_setattr(struct user_namespace *mnt_userns, struct inode *inode,
+int may_setattr(struct mnt_idmap *idmap, struct inode *inode,
 		unsigned int ia_valid);
-int setattr_prepare(struct user_namespace *, struct dentry *, struct iattr *);
+int setattr_prepare(struct mnt_idmap *, struct dentry *, struct iattr *);
 extern int inode_newsize_ok(const struct inode *, loff_t offset);
-void setattr_copy(struct user_namespace *, struct inode *inode,
+void setattr_copy(struct mnt_idmap *, struct inode *inode,
 		  const struct iattr *attr);
 
 extern int file_update_time(struct file *file);
@@ -3111,13 +3105,13 @@ static inline bool is_sxid(umode_t mode)
 	return mode & (S_ISUID | S_ISGID);
 }
 
-static inline int check_sticky(struct user_namespace *mnt_userns,
+static inline int check_sticky(struct mnt_idmap *idmap,
 			       struct inode *dir, struct inode *inode)
 {
 	if (!(dir->i_mode & S_ISVTX))
 		return 0;
 
-	return __check_sticky(mnt_userns, dir, inode);
+	return __check_sticky(idmap, dir, inode);
 }
 
 static inline void inode_has_no_xattr(struct inode *inode)
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 5a0b2a285a18..172b113a9864 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -18,7 +18,7 @@ struct linux_binprm;
 extern enum hash_algo ima_get_current_hash_algo(void);
 extern int ima_bprm_check(struct linux_binprm *bprm);
 extern int ima_file_check(struct file *file, int mask);
-extern void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
+extern void ima_post_create_tmpfile(struct mnt_idmap *idmap,
 				    struct inode *inode);
 extern void ima_file_free(struct file *file);
 extern int ima_file_mmap(struct file *file, unsigned long prot);
@@ -30,7 +30,7 @@ extern int ima_read_file(struct file *file, enum kernel_read_file_id id,
 			 bool contents);
 extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
 			      enum kernel_read_file_id id);
-extern void ima_post_path_mknod(struct user_namespace *mnt_userns,
+extern void ima_post_path_mknod(struct mnt_idmap *idmap,
 				struct dentry *dentry);
 extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
 extern int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size);
@@ -66,7 +66,7 @@ static inline int ima_file_check(struct file *file, int mask)
 	return 0;
 }
 
-static inline void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
+static inline void ima_post_create_tmpfile(struct mnt_idmap *idmap,
 					   struct inode *inode)
 {
 }
@@ -111,7 +111,7 @@ static inline int ima_post_read_file(struct file *file, void *buf, loff_t size,
 	return 0;
 }
 
-static inline void ima_post_path_mknod(struct user_namespace *mnt_userns,
+static inline void ima_post_path_mknod(struct mnt_idmap *idmap,
 				       struct dentry *dentry)
 {
 	return;
@@ -183,18 +183,18 @@ static inline void ima_post_key_create_or_update(struct key *keyring,
 
 #ifdef CONFIG_IMA_APPRAISE
 extern bool is_ima_appraise_enabled(void);
-extern void ima_inode_post_setattr(struct user_namespace *mnt_userns,
+extern void ima_inode_post_setattr(struct mnt_idmap *idmap,
 				   struct dentry *dentry);
 extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 		       const void *xattr_value, size_t xattr_value_len);
-extern int ima_inode_set_acl(struct user_namespace *mnt_userns,
+extern int ima_inode_set_acl(struct mnt_idmap *idmap,
 			     struct dentry *dentry, const char *acl_name,
 			     struct posix_acl *kacl);
-static inline int ima_inode_remove_acl(struct user_namespace *mnt_userns,
+static inline int ima_inode_remove_acl(struct mnt_idmap *idmap,
 				       struct dentry *dentry,
 				       const char *acl_name)
 {
-	return ima_inode_set_acl(mnt_userns, dentry, acl_name, NULL);
+	return ima_inode_set_acl(idmap, dentry, acl_name, NULL);
 }
 extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name);
 #else
@@ -203,7 +203,7 @@ static inline bool is_ima_appraise_enabled(void)
 	return 0;
 }
 
-static inline void ima_inode_post_setattr(struct user_namespace *mnt_userns,
+static inline void ima_inode_post_setattr(struct mnt_idmap *idmap,
 					  struct dentry *dentry)
 {
 	return;
@@ -217,7 +217,7 @@ static inline int ima_inode_setxattr(struct dentry *dentry,
 	return 0;
 }
 
-static inline int ima_inode_set_acl(struct user_namespace *mnt_userns,
+static inline int ima_inode_set_acl(struct mnt_idmap *idmap,
 				    struct dentry *dentry, const char *acl_name,
 				    struct posix_acl *kacl)
 {
@@ -231,7 +231,7 @@ static inline int ima_inode_removexattr(struct dentry *dentry,
 	return 0;
 }
 
-static inline int ima_inode_remove_acl(struct user_namespace *mnt_userns,
+static inline int ima_inode_remove_acl(struct mnt_idmap *idmap,
 				       struct dentry *dentry,
 				       const char *acl_name)
 {
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index ed6cb2ac55fa..094b76dc7164 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -136,25 +136,25 @@ LSM_HOOK(int, 0, inode_follow_link, struct dentry *dentry, struct inode *inode,
 LSM_HOOK(int, 0, inode_permission, struct inode *inode, int mask)
 LSM_HOOK(int, 0, inode_setattr, struct dentry *dentry, struct iattr *attr)
 LSM_HOOK(int, 0, inode_getattr, const struct path *path)
-LSM_HOOK(int, 0, inode_setxattr, struct user_namespace *mnt_userns,
+LSM_HOOK(int, 0, inode_setxattr, struct mnt_idmap *idmap,
 	 struct dentry *dentry, const char *name, const void *value,
 	 size_t size, int flags)
 LSM_HOOK(void, LSM_RET_VOID, inode_post_setxattr, struct dentry *dentry,
 	 const char *name, const void *value, size_t size, int flags)
 LSM_HOOK(int, 0, inode_getxattr, struct dentry *dentry, const char *name)
 LSM_HOOK(int, 0, inode_listxattr, struct dentry *dentry)
-LSM_HOOK(int, 0, inode_removexattr, struct user_namespace *mnt_userns,
+LSM_HOOK(int, 0, inode_removexattr, struct mnt_idmap *idmap,
 	 struct dentry *dentry, const char *name)
-LSM_HOOK(int, 0, inode_set_acl, struct user_namespace *mnt_userns,
+LSM_HOOK(int, 0, inode_set_acl, struct mnt_idmap *idmap,
 	 struct dentry *dentry, const char *acl_name, struct posix_acl *kacl)
-LSM_HOOK(int, 0, inode_get_acl, struct user_namespace *mnt_userns,
+LSM_HOOK(int, 0, inode_get_acl, struct mnt_idmap *idmap,
 	 struct dentry *dentry, const char *acl_name)
-LSM_HOOK(int, 0, inode_remove_acl, struct user_namespace *mnt_userns,
+LSM_HOOK(int, 0, inode_remove_acl, struct mnt_idmap *idmap,
 	 struct dentry *dentry, const char *acl_name)
 LSM_HOOK(int, 0, inode_need_killpriv, struct dentry *dentry)
-LSM_HOOK(int, 0, inode_killpriv, struct user_namespace *mnt_userns,
+LSM_HOOK(int, 0, inode_killpriv, struct mnt_idmap *idmap,
 	 struct dentry *dentry)
-LSM_HOOK(int, -EOPNOTSUPP, inode_getsecurity, struct user_namespace *mnt_userns,
+LSM_HOOK(int, -EOPNOTSUPP, inode_getsecurity, struct mnt_idmap *idmap,
 	 struct inode *inode, const char *name, void **buffer, bool alloc)
 LSM_HOOK(int, -EOPNOTSUPP, inode_setsecurity, struct inode *inode,
 	 const char *name, const void *value, size_t size, int flags)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 0a5ba81f7367..6e156d2acffc 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -475,7 +475,7 @@
  * @inode_killpriv:
  *	The setuid bit is being removed.  Remove similar security labels.
  *	Called with the dentry->d_inode->i_mutex held.
- *	@mnt_userns: user namespace of the mount.
+ *	@idmap: idmap of the mount.
  *	@dentry is the dentry being changed.
  *	Return 0 on success.  If error is returned, then the operation
  *	causing setuid bit removal is failed.
diff --git a/include/linux/mnt_idmapping.h b/include/linux/mnt_idmapping.h
index 0ccca33a7a6d..057c89867aa2 100644
--- a/include/linux/mnt_idmapping.h
+++ b/include/linux/mnt_idmapping.h
@@ -113,167 +113,23 @@ static inline bool vfsgid_eq_kgid(vfsgid_t vfsgid, kgid_t kgid)
 #define AS_KUIDT(val) (kuid_t){ __vfsuid_val(val) }
 #define AS_KGIDT(val) (kgid_t){ __vfsgid_val(val) }
 
-#ifdef CONFIG_MULTIUSER
-/**
- * vfsgid_in_group_p() - check whether a vfsuid matches the caller's groups
- * @vfsgid: the mnt gid to match
- *
- * This function can be used to determine whether @vfsuid matches any of the
- * caller's groups.
- *
- * Return: 1 if vfsuid matches caller's groups, 0 if not.
- */
-static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
-{
-	return in_group_p(AS_KGIDT(vfsgid));
-}
-#else
-static inline int vfsgid_in_group_p(vfsgid_t vfsgid)
-{
-	return 1;
-}
-#endif
+int vfsgid_in_group_p(vfsgid_t vfsgid);
 
-/**
- * initial_idmapping - check whether this is the initial mapping
- * @ns: idmapping to check
- *
- * Check whether this is the initial mapping, mapping 0 to 0, 1 to 1,
- * [...], 1000 to 1000 [...].
- *
- * Return: true if this is the initial mapping, false if not.
- */
-static inline bool initial_idmapping(const struct user_namespace *ns)
-{
-	return ns == &init_user_ns;
-}
+vfsuid_t make_vfsuid(struct mnt_idmap *idmap,
+		     struct user_namespace *fs_userns, kuid_t kuid);
 
-/**
- * no_idmapping - check whether we can skip remapping a kuid/gid
- * @mnt_userns: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- *
- * This function can be used to check whether a remapping between two
- * idmappings is required.
- * An idmapped mount is a mount that has an idmapping attached to it that
- * is different from the filsystem's idmapping and the initial idmapping.
- * If the initial mapping is used or the idmapping of the mount and the
- * filesystem are identical no remapping is required.
- *
- * Return: true if remapping can be skipped, false if not.
- */
-static inline bool no_idmapping(const struct user_namespace *mnt_userns,
-				const struct user_namespace *fs_userns)
-{
-	return initial_idmapping(mnt_userns) || mnt_userns == fs_userns;
-}
+vfsgid_t make_vfsgid(struct mnt_idmap *idmap,
+		     struct user_namespace *fs_userns, kgid_t kgid);
 
-/**
- * make_vfsuid - map a filesystem kuid into a mnt_userns
- * @mnt_userns: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- * @kuid : kuid to be mapped
- *
- * Take a @kuid and remap it from @fs_userns into @mnt_userns. Use this
- * function when preparing a @kuid to be reported to userspace.
- *
- * If no_idmapping() determines that this is not an idmapped mount we can
- * simply return @kuid unchanged.
- * If initial_idmapping() tells us that the filesystem is not mounted with an
- * idmapping we know the value of @kuid won't change when calling
- * from_kuid() so we can simply retrieve the value via __kuid_val()
- * directly.
- *
- * Return: @kuid mapped according to @mnt_userns.
- * If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is
- * returned.
- */
+kuid_t from_vfsuid(struct mnt_idmap *idmap,
+		   struct user_namespace *fs_userns, vfsuid_t vfsuid);
 
-static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns,
-				   struct user_namespace *fs_userns,
-				   kuid_t kuid)
-{
-	uid_t uid;
-
-	if (no_idmapping(mnt_userns, fs_userns))
-		return VFSUIDT_INIT(kuid);
-	if (initial_idmapping(fs_userns))
-		uid = __kuid_val(kuid);
-	else
-		uid = from_kuid(fs_userns, kuid);
-	if (uid == (uid_t)-1)
-		return INVALID_VFSUID;
-	return VFSUIDT_INIT(make_kuid(mnt_userns, uid));
-}
-
-/**
- * make_vfsgid - map a filesystem kgid into a mnt_userns
- * @mnt_userns: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- * @kgid : kgid to be mapped
- *
- * Take a @kgid and remap it from @fs_userns into @mnt_userns. Use this
- * function when preparing a @kgid to be reported to userspace.
- *
- * If no_idmapping() determines that this is not an idmapped mount we can
- * simply return @kgid unchanged.
- * If initial_idmapping() tells us that the filesystem is not mounted with an
- * idmapping we know the value of @kgid won't change when calling
- * from_kgid() so we can simply retrieve the value via __kgid_val()
- * directly.
- *
- * Return: @kgid mapped according to @mnt_userns.
- * If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is
- * returned.
- */
-
-static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns,
-				   struct user_namespace *fs_userns,
-				   kgid_t kgid)
-{
-	gid_t gid;
-
-	if (no_idmapping(mnt_userns, fs_userns))
-		return VFSGIDT_INIT(kgid);
-	if (initial_idmapping(fs_userns))
-		gid = __kgid_val(kgid);
-	else
-		gid = from_kgid(fs_userns, kgid);
-	if (gid == (gid_t)-1)
-		return INVALID_VFSGID;
-	return VFSGIDT_INIT(make_kgid(mnt_userns, gid));
-}
-
-/**
- * from_vfsuid - map a vfsuid into the filesystem idmapping
- * @mnt_userns: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- * @vfsuid : vfsuid to be mapped
- *
- * Map @vfsuid into the filesystem idmapping. This function has to be used in
- * order to e.g. write @vfsuid to inode->i_uid.
- *
- * Return: @vfsuid mapped into the filesystem idmapping
- */
-static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
-				 struct user_namespace *fs_userns,
-				 vfsuid_t vfsuid)
-{
-	uid_t uid;
-
-	if (no_idmapping(mnt_userns, fs_userns))
-		return AS_KUIDT(vfsuid);
-	uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid));
-	if (uid == (uid_t)-1)
-		return INVALID_UID;
-	if (initial_idmapping(fs_userns))
-		return KUIDT_INIT(uid);
-	return make_kuid(fs_userns, uid);
-}
+kgid_t from_vfsgid(struct mnt_idmap *idmap,
+		   struct user_namespace *fs_userns, vfsgid_t vfsgid);
 
 /**
  * vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem
- * @mnt_userns: the mount's idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsuid: vfsuid to be mapped
  *
@@ -283,11 +139,11 @@ static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
  *
  * Return: true if @vfsuid has a mapping in the filesystem, false if not.
  */
-static inline bool vfsuid_has_fsmapping(struct user_namespace *mnt_userns,
+static inline bool vfsuid_has_fsmapping(struct mnt_idmap *idmap,
 					struct user_namespace *fs_userns,
 					vfsuid_t vfsuid)
 {
-	return uid_valid(from_vfsuid(mnt_userns, fs_userns, vfsuid));
+	return uid_valid(from_vfsuid(idmap, fs_userns, vfsuid));
 }
 
 static inline bool vfsuid_has_mapping(struct user_namespace *userns,
@@ -310,35 +166,8 @@ static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid)
 }
 
 /**
- * from_vfsgid - map a vfsgid into the filesystem idmapping
- * @mnt_userns: the mount's idmapping
- * @fs_userns: the filesystem's idmapping
- * @vfsgid : vfsgid to be mapped
- *
- * Map @vfsgid into the filesystem idmapping. This function has to be used in
- * order to e.g. write @vfsgid to inode->i_gid.
- *
- * Return: @vfsgid mapped into the filesystem idmapping
- */
-static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
-				 struct user_namespace *fs_userns,
-				 vfsgid_t vfsgid)
-{
-	gid_t gid;
-
-	if (no_idmapping(mnt_userns, fs_userns))
-		return AS_KGIDT(vfsgid);
-	gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid));
-	if (gid == (gid_t)-1)
-		return INVALID_GID;
-	if (initial_idmapping(fs_userns))
-		return KGIDT_INIT(gid);
-	return make_kgid(fs_userns, gid);
-}
-
-/**
  * vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem
- * @mnt_userns: the mount's idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsgid: vfsgid to be mapped
  *
@@ -348,11 +177,11 @@ static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
  *
  * Return: true if @vfsgid has a mapping in the filesystem, false if not.
  */
-static inline bool vfsgid_has_fsmapping(struct user_namespace *mnt_userns,
+static inline bool vfsgid_has_fsmapping(struct mnt_idmap *idmap,
 					struct user_namespace *fs_userns,
 					vfsgid_t vfsgid)
 {
-	return gid_valid(from_vfsgid(mnt_userns, fs_userns, vfsgid));
+	return gid_valid(from_vfsgid(idmap, fs_userns, vfsgid));
 }
 
 static inline bool vfsgid_has_mapping(struct user_namespace *userns,
@@ -375,8 +204,8 @@ static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid)
 }
 
 /**
- * mapped_fsuid - return caller's fsuid mapped up into a mnt_userns
- * @mnt_userns: the mount's idmapping
+ * mapped_fsuid - return caller's fsuid mapped according to an idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  *
  * Use this helper to initialize a new vfs or filesystem object based on
@@ -385,18 +214,17 @@ static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid)
  * O_CREAT. Other examples include the allocation of quotas for a specific
  * user.
  *
- * Return: the caller's current fsuid mapped up according to @mnt_userns.
+ * Return: the caller's current fsuid mapped up according to @idmap.
  */
-static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns,
+static inline kuid_t mapped_fsuid(struct mnt_idmap *idmap,
 				  struct user_namespace *fs_userns)
 {
-	return from_vfsuid(mnt_userns, fs_userns,
-			   VFSUIDT_INIT(current_fsuid()));
+	return from_vfsuid(idmap, fs_userns, VFSUIDT_INIT(current_fsuid()));
 }
 
 /**
- * mapped_fsgid - return caller's fsgid mapped up into a mnt_userns
- * @mnt_userns: the mount's idmapping
+ * mapped_fsgid - return caller's fsgid mapped according to an idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  *
  * Use this helper to initialize a new vfs or filesystem object based on
@@ -405,13 +233,15 @@ static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns,
  * O_CREAT. Other examples include the allocation of quotas for a specific
  * user.
  *
- * Return: the caller's current fsgid mapped up according to @mnt_userns.
+ * Return: the caller's current fsgid mapped up according to @idmap.
  */
-static inline kgid_t mapped_fsgid(struct user_namespace *mnt_userns,
+static inline kgid_t mapped_fsgid(struct mnt_idmap *idmap,
 				  struct user_namespace *fs_userns)
 {
-	return from_vfsgid(mnt_userns, fs_userns,
-			   VFSGIDT_INIT(current_fsgid()));
+	return from_vfsgid(idmap, fs_userns, VFSGIDT_INIT(current_fsgid()));
 }
 
+bool check_fsmapping(const struct mnt_idmap *idmap,
+		     const struct super_block *sb);
+
 #endif /* _LINUX_MNT_IDMAPPING_H */
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 62475996fac6..52f452b2259a 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -74,8 +74,6 @@ struct vfsmount {
 	struct mnt_idmap *mnt_idmap;
 } __randomize_layout;
 
-struct user_namespace *mnt_user_ns(const struct vfsmount *mnt);
-struct user_namespace *mnt_idmap_owner(const struct mnt_idmap *idmap);
 static inline struct mnt_idmap *mnt_idmap(const struct vfsmount *mnt)
 {
 	/* Pairs with smp_store_release() in do_idmap_mount(). */
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 00fee52df842..0d4531fd46e7 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -68,11 +68,11 @@ extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int);
 extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
 extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
 extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int);
-struct dentry *lookup_one(struct user_namespace *, const char *, struct dentry *, int);
-struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns,
+struct dentry *lookup_one(struct mnt_idmap *, const char *, struct dentry *, int);
+struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
 				   const char *name, struct dentry *base,
 				   int len);
-struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
+struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
 					    const char *name,
 					    struct dentry *base, int len);
 
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index d92fdfd2444c..d6c119e31d7a 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -392,11 +392,11 @@ extern int nfs_refresh_inode(struct inode *, struct nfs_fattr *);
 extern int nfs_post_op_update_inode(struct inode *inode, struct nfs_fattr *fattr);
 extern int nfs_post_op_update_inode_force_wcc(struct inode *inode, struct nfs_fattr *fattr);
 extern int nfs_post_op_update_inode_force_wcc_locked(struct inode *inode, struct nfs_fattr *fattr);
-extern int nfs_getattr(struct user_namespace *, const struct path *,
+extern int nfs_getattr(struct mnt_idmap *, const struct path *,
 		       struct kstat *, u32, unsigned int);
 extern void nfs_access_add_cache(struct inode *, struct nfs_access_entry *, const struct cred *);
 extern void nfs_access_set_mask(struct nfs_access_entry *, u32);
-extern int nfs_permission(struct user_namespace *, struct inode *, int);
+extern int nfs_permission(struct mnt_idmap *, struct inode *, int);
 extern int nfs_open(struct inode *, struct file *);
 extern int nfs_attribute_cache_expired(struct inode *inode);
 extern int nfs_revalidate_inode(struct inode *inode, unsigned long flags);
@@ -405,7 +405,7 @@ extern int nfs_clear_invalid_mapping(struct address_space *mapping);
 extern bool nfs_mapping_need_revalidate_inode(struct inode *inode);
 extern int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping);
 extern int nfs_revalidate_mapping_rcu(struct inode *inode);
-extern int nfs_setattr(struct user_namespace *, struct dentry *, struct iattr *);
+extern int nfs_setattr(struct mnt_idmap *, struct dentry *, struct iattr *);
 extern void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr, struct nfs_fattr *);
 extern void nfs_setsecurity(struct inode *inode, struct nfs_fattr *fattr);
 extern struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ctx);
diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index ee608d22ecb9..21cc29b8a9e8 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -69,20 +69,20 @@ extern int __posix_acl_create(struct posix_acl **, gfp_t, umode_t *);
 extern int __posix_acl_chmod(struct posix_acl **, gfp_t, umode_t);
 
 extern struct posix_acl *get_posix_acl(struct inode *, int);
-int set_posix_acl(struct user_namespace *, struct dentry *, int,
+int set_posix_acl(struct mnt_idmap *, struct dentry *, int,
 		  struct posix_acl *);
 
 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type);
 struct posix_acl *posix_acl_clone(const struct posix_acl *acl, gfp_t flags);
 
 #ifdef CONFIG_FS_POSIX_ACL
-int posix_acl_chmod(struct user_namespace *, struct dentry *, umode_t);
+int posix_acl_chmod(struct mnt_idmap *, struct dentry *, umode_t);
 extern int posix_acl_create(struct inode *, umode_t *, struct posix_acl **,
 		struct posix_acl **);
-int posix_acl_update_mode(struct user_namespace *, struct inode *, umode_t *,
+int posix_acl_update_mode(struct mnt_idmap *, struct inode *, umode_t *,
 			  struct posix_acl **);
 
-int simple_set_acl(struct user_namespace *, struct dentry *,
+int simple_set_acl(struct mnt_idmap *, struct dentry *,
 		   struct posix_acl *, int);
 extern int simple_acl_create(struct inode *, struct inode *);
 
@@ -91,7 +91,7 @@ void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl);
 void forget_cached_acl(struct inode *inode, int type);
 void forget_all_cached_acls(struct inode *inode);
 int posix_acl_valid(struct user_namespace *, const struct posix_acl *);
-int posix_acl_permission(struct user_namespace *, struct inode *,
+int posix_acl_permission(struct mnt_idmap *, struct inode *,
 			 const struct posix_acl *, int);
 
 static inline void cache_no_acl(struct inode *inode)
@@ -100,14 +100,14 @@ static inline void cache_no_acl(struct inode *inode)
 	inode->i_default_acl = NULL;
 }
 
-int vfs_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+int vfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 		const char *acl_name, struct posix_acl *kacl);
-struct posix_acl *vfs_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *vfs_get_acl(struct mnt_idmap *idmap,
 			      struct dentry *dentry, const char *acl_name);
-int vfs_remove_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 		   const char *acl_name);
 #else
-static inline int posix_acl_chmod(struct user_namespace *mnt_userns,
+static inline int posix_acl_chmod(struct mnt_idmap *idmap,
 				  struct dentry *dentry, umode_t mode)
 {
 	return 0;
@@ -134,21 +134,21 @@ static inline void forget_all_cached_acls(struct inode *inode)
 {
 }
 
-static inline int vfs_set_acl(struct user_namespace *mnt_userns,
+static inline int vfs_set_acl(struct mnt_idmap *idmap,
 			      struct dentry *dentry, const char *name,
 			      struct posix_acl *acl)
 {
 	return -EOPNOTSUPP;
 }
 
-static inline struct posix_acl *vfs_get_acl(struct user_namespace *mnt_userns,
+static inline struct posix_acl *vfs_get_acl(struct mnt_idmap *idmap,
 					    struct dentry *dentry,
 					    const char *acl_name)
 {
 	return ERR_PTR(-EOPNOTSUPP);
 }
 
-static inline int vfs_remove_acl(struct user_namespace *mnt_userns,
+static inline int vfs_remove_acl(struct mnt_idmap *idmap,
 				 struct dentry *dentry, const char *acl_name)
 {
 	return -EOPNOTSUPP;
diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
index 0d8625d71733..11a4becff3a9 100644
--- a/include/linux/quotaops.h
+++ b/include/linux/quotaops.h
@@ -20,12 +20,12 @@ static inline struct quota_info *sb_dqopt(struct super_block *sb)
 }
 
 /* i_mutex must being held */
-static inline bool is_quota_modification(struct user_namespace *mnt_userns,
+static inline bool is_quota_modification(struct mnt_idmap *idmap,
 					 struct inode *inode, struct iattr *ia)
 {
 	return ((ia->ia_valid & ATTR_SIZE) ||
-		i_uid_needs_update(mnt_userns, ia, inode) ||
-		i_gid_needs_update(mnt_userns, ia, inode));
+		i_uid_needs_update(idmap, ia, inode) ||
+		i_gid_needs_update(idmap, ia, inode));
 }
 
 #if defined(CONFIG_QUOTA)
@@ -116,7 +116,7 @@ int dquot_set_dqblk(struct super_block *sb, struct kqid id,
 		struct qc_dqblk *di);
 
 int __dquot_transfer(struct inode *inode, struct dquot **transfer_to);
-int dquot_transfer(struct user_namespace *mnt_userns, struct inode *inode,
+int dquot_transfer(struct mnt_idmap *idmap, struct inode *inode,
 		   struct iattr *iattr);
 
 static inline struct mem_dqinfo *sb_dqinfo(struct super_block *sb, int type)
@@ -236,7 +236,7 @@ static inline void dquot_free_inode(struct inode *inode)
 {
 }
 
-static inline int dquot_transfer(struct user_namespace *mnt_userns,
+static inline int dquot_transfer(struct mnt_idmap *idmap,
 				 struct inode *inode, struct iattr *iattr)
 {
 	return 0;
diff --git a/include/linux/security.h b/include/linux/security.h
index 5b67f208f7de..5984d0d550b4 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -153,12 +153,11 @@ extern int cap_capset(struct cred *new, const struct cred *old,
 extern int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file);
 int cap_inode_setxattr(struct dentry *dentry, const char *name,
 		       const void *value, size_t size, int flags);
-int cap_inode_removexattr(struct user_namespace *mnt_userns,
+int cap_inode_removexattr(struct mnt_idmap *idmap,
 			  struct dentry *dentry, const char *name);
 int cap_inode_need_killpriv(struct dentry *dentry);
-int cap_inode_killpriv(struct user_namespace *mnt_userns,
-		       struct dentry *dentry);
-int cap_inode_getsecurity(struct user_namespace *mnt_userns,
+int cap_inode_killpriv(struct mnt_idmap *idmap, struct dentry *dentry);
+int cap_inode_getsecurity(struct mnt_idmap *idmap,
 			  struct inode *inode, const char *name, void **buffer,
 			  bool alloc);
 extern int cap_mmap_addr(unsigned long addr);
@@ -356,29 +355,28 @@ int security_inode_readlink(struct dentry *dentry);
 int security_inode_follow_link(struct dentry *dentry, struct inode *inode,
 			       bool rcu);
 int security_inode_permission(struct inode *inode, int mask);
-int security_inode_setattr(struct user_namespace *mnt_userns,
+int security_inode_setattr(struct mnt_idmap *idmap,
 			   struct dentry *dentry, struct iattr *attr);
 int security_inode_getattr(const struct path *path);
-int security_inode_setxattr(struct user_namespace *mnt_userns,
+int security_inode_setxattr(struct mnt_idmap *idmap,
 			    struct dentry *dentry, const char *name,
 			    const void *value, size_t size, int flags);
-int security_inode_set_acl(struct user_namespace *mnt_userns,
+int security_inode_set_acl(struct mnt_idmap *idmap,
 			   struct dentry *dentry, const char *acl_name,
 			   struct posix_acl *kacl);
-int security_inode_get_acl(struct user_namespace *mnt_userns,
+int security_inode_get_acl(struct mnt_idmap *idmap,
 			   struct dentry *dentry, const char *acl_name);
-int security_inode_remove_acl(struct user_namespace *mnt_userns,
+int security_inode_remove_acl(struct mnt_idmap *idmap,
 			      struct dentry *dentry, const char *acl_name);
 void security_inode_post_setxattr(struct dentry *dentry, const char *name,
 				  const void *value, size_t size, int flags);
 int security_inode_getxattr(struct dentry *dentry, const char *name);
 int security_inode_listxattr(struct dentry *dentry);
-int security_inode_removexattr(struct user_namespace *mnt_userns,
+int security_inode_removexattr(struct mnt_idmap *idmap,
 			       struct dentry *dentry, const char *name);
 int security_inode_need_killpriv(struct dentry *dentry);
-int security_inode_killpriv(struct user_namespace *mnt_userns,
-			    struct dentry *dentry);
-int security_inode_getsecurity(struct user_namespace *mnt_userns,
+int security_inode_killpriv(struct mnt_idmap *idmap, struct dentry *dentry);
+int security_inode_getsecurity(struct mnt_idmap *idmap,
 			       struct inode *inode, const char *name,
 			       void **buffer, bool alloc);
 int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags);
@@ -862,7 +860,7 @@ static inline int security_inode_permission(struct inode *inode, int mask)
 	return 0;
 }
 
-static inline int security_inode_setattr(struct user_namespace *mnt_userns,
+static inline int security_inode_setattr(struct mnt_idmap *idmap,
 					 struct dentry *dentry,
 					 struct iattr *attr)
 {
@@ -874,14 +872,14 @@ static inline int security_inode_getattr(const struct path *path)
 	return 0;
 }
 
-static inline int security_inode_setxattr(struct user_namespace *mnt_userns,
+static inline int security_inode_setxattr(struct mnt_idmap *idmap,
 		struct dentry *dentry, const char *name, const void *value,
 		size_t size, int flags)
 {
 	return cap_inode_setxattr(dentry, name, value, size, flags);
 }
 
-static inline int security_inode_set_acl(struct user_namespace *mnt_userns,
+static inline int security_inode_set_acl(struct mnt_idmap *idmap,
 					 struct dentry *dentry,
 					 const char *acl_name,
 					 struct posix_acl *kacl)
@@ -889,14 +887,14 @@ static inline int security_inode_set_acl(struct user_namespace *mnt_userns,
 	return 0;
 }
 
-static inline int security_inode_get_acl(struct user_namespace *mnt_userns,
+static inline int security_inode_get_acl(struct mnt_idmap *idmap,
 					 struct dentry *dentry,
 					 const char *acl_name)
 {
 	return 0;
 }
 
-static inline int security_inode_remove_acl(struct user_namespace *mnt_userns,
+static inline int security_inode_remove_acl(struct mnt_idmap *idmap,
 					    struct dentry *dentry,
 					    const char *acl_name)
 {
@@ -918,11 +916,11 @@ static inline int security_inode_listxattr(struct dentry *dentry)
 	return 0;
 }
 
-static inline int security_inode_removexattr(struct user_namespace *mnt_userns,
+static inline int security_inode_removexattr(struct mnt_idmap *idmap,
 					     struct dentry *dentry,
 					     const char *name)
 {
-	return cap_inode_removexattr(mnt_userns, dentry, name);
+	return cap_inode_removexattr(idmap, dentry, name);
 }
 
 static inline int security_inode_need_killpriv(struct dentry *dentry)
@@ -930,18 +928,18 @@ static inline int security_inode_need_killpriv(struct dentry *dentry)
 	return cap_inode_need_killpriv(dentry);
 }
 
-static inline int security_inode_killpriv(struct user_namespace *mnt_userns,
+static inline int security_inode_killpriv(struct mnt_idmap *idmap,
 					  struct dentry *dentry)
 {
-	return cap_inode_killpriv(mnt_userns, dentry);
+	return cap_inode_killpriv(idmap, dentry);
 }
 
-static inline int security_inode_getsecurity(struct user_namespace *mnt_userns,
+static inline int security_inode_getsecurity(struct mnt_idmap *idmap,
 					     struct inode *inode,
 					     const char *name, void **buffer,
 					     bool alloc)
 {
-	return cap_inode_getsecurity(mnt_userns, inode, name, buffer, alloc);
+	return cap_inode_getsecurity(idmap, inode, name, buffer, alloc);
 }
 
 static inline int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags)
diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index 2e7dd44926e4..6af72461397d 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -42,7 +42,7 @@ struct xattr_handler {
 		   struct inode *inode, const char *name, void *buffer,
 		   size_t size);
 	int (*set)(const struct xattr_handler *,
-		   struct user_namespace *mnt_userns, struct dentry *dentry,
+		   struct mnt_idmap *idmap, struct dentry *dentry,
 		   struct inode *inode, const char *name, const void *buffer,
 		   size_t size, int flags);
 };
@@ -56,25 +56,25 @@ struct xattr {
 };
 
 ssize_t __vfs_getxattr(struct dentry *, struct inode *, const char *, void *, size_t);
-ssize_t vfs_getxattr(struct user_namespace *, struct dentry *, const char *,
+ssize_t vfs_getxattr(struct mnt_idmap *, struct dentry *, const char *,
 		     void *, size_t);
 ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
-int __vfs_setxattr(struct user_namespace *, struct dentry *, struct inode *,
+int __vfs_setxattr(struct mnt_idmap *, struct dentry *, struct inode *,
 		   const char *, const void *, size_t, int);
-int __vfs_setxattr_noperm(struct user_namespace *, struct dentry *,
+int __vfs_setxattr_noperm(struct mnt_idmap *, struct dentry *,
 			  const char *, const void *, size_t, int);
-int __vfs_setxattr_locked(struct user_namespace *, struct dentry *,
+int __vfs_setxattr_locked(struct mnt_idmap *, struct dentry *,
 			  const char *, const void *, size_t, int,
 			  struct inode **);
-int vfs_setxattr(struct user_namespace *, struct dentry *, const char *,
+int vfs_setxattr(struct mnt_idmap *, struct dentry *, const char *,
 		 const void *, size_t, int);
-int __vfs_removexattr(struct user_namespace *, struct dentry *, const char *);
-int __vfs_removexattr_locked(struct user_namespace *, struct dentry *,
+int __vfs_removexattr(struct mnt_idmap *, struct dentry *, const char *);
+int __vfs_removexattr_locked(struct mnt_idmap *, struct dentry *,
 			     const char *, struct inode **);
-int vfs_removexattr(struct user_namespace *, struct dentry *, const char *);
+int vfs_removexattr(struct mnt_idmap *, struct dentry *, const char *);
 
 ssize_t generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size);
-int vfs_getxattr_alloc(struct user_namespace *mnt_userns,
+int vfs_getxattr_alloc(struct mnt_idmap *idmap,
 		       struct dentry *dentry, const char *name,
 		       char **xattr_value, size_t size, gfp_t flags);