NFSv4: Simplify some cache consistency post-op GETATTRs

Certain asynchronous operations such as write() do not expect
(or care) that other metadata such as the file owner, mode, acls, ...
change. All they want to do is update and/or check the change attribute,
ctime, and mtime.
By skipping the file owner and group update, we also avoid having to do a
potential idmapper upcall for these asynchronous RPC calls.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/nfs_fs_sb.h

@@ -106,6 +106,11 @@ struct nfs_server {
 	u32			attr_bitmask[2];/* V4 bitmask representing the set
 						   of attributes supported on this
 						   filesystem */
+	u32			cache_consistency_bitmask[2];
+						/* V4 bitmask representing the subset
+						   of change attribute, size, ctime
+						   and mtime attributes supported by
+						   the server */
 	u32			acl_bitmask;	/* V4 bitmask representing the ACEs
 						   that are supported on this
 						   filesystem */