fanotify: split version into version and metadata_len

To implement per event type optional headers we are interested in
knowing how long the metadata structure is.  This patch slits the __u32
version field into a __u8 version and a __u16 metadata_len field (with
__u8 left over).  This should allow for backwards compat ABI.

Signed-off-by: Alexey Zaytsev <alexey.zaytsev@gmail.com>
[rewrote descrtion and changed object sizes and ordering - eparis]
Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index c73224315aee..6c6133f76e16 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -83,11 +83,13 @@
                                  FAN_ALL_PERM_EVENTS |\
                                  FAN_Q_OVERFLOW)
 
-#define FANOTIFY_METADATA_VERSION       2
+#define FANOTIFY_METADATA_VERSION       3
 
 struct fanotify_event_metadata {
         __u32 event_len;
-        __u32 vers;
+        __u8 vers;
+        __u8 reserved;
+        __u16 metadata_len;
         __aligned_u64 mask;
         __s32 fd;
         __s32 pid;