userns: use union in {g,u}idmap struct

- Add a struct containing two pointer to extents and wrap both the static extent
  array and the struct into a union. This is done in preparation for bumping the
  {g,u}idmap limits for user namespaces.
- Add brackets around anonymous union when using designated initializers to
  initialize members in order to please gcc <= 4.4.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

1 files changed, 13 insertions, 5 deletions

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index c18e01252346..7c83d7f6289b 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -12,13 +12,21 @@
 
 #define UID_GID_MAP_MAX_EXTENTS 5
 
+struct uid_gid_extent {
+	u32 first;
+	u32 lower_first;
+	u32 count;
+};
+
 struct uid_gid_map {	/* 64 bytes -- 1 cache line */
 	u32 nr_extents;
-	struct uid_gid_extent {
-		u32 first;
-		u32 lower_first;
-		u32 count;
-	} extent[UID_GID_MAP_MAX_EXTENTS];
+	union {
+		struct uid_gid_extent extent[UID_GID_MAP_MAX_EXTENTS];
+		struct {
+			struct uid_gid_extent *forward;
+			struct uid_gid_extent *reverse;
+		};
+	};
 };
 
 #define USERNS_SETGROUPS_ALLOWED 1UL