nfs: add support for the umask attribute

Clients can set the umask attribute when creating files to cause the
server to apply it always except when inheriting permissions from the
parent directory.  That way, the new files will end up with the same
permissions as files created locally.

See https://tools.ietf.org/html/draft-ietf-nfsv4-umask-02 for more details.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

include/linux/nfs4.h

@@ -440,6 +440,7 @@ enum lock_type4 {
 #define FATTR4_WORD2_MDSTHRESHOLD       (1UL << 4)
 #define FATTR4_WORD2_CLONE_BLKSIZE	(1UL << 13)
 #define FATTR4_WORD2_SECURITY_LABEL     (1UL << 16)
+#define FATTR4_WORD2_MODE_UMASK		(1UL << 17)
 
 /* MDS threshold bitmap bits */
 #define THRESHOLD_RD                    (1UL << 0)

include/linux/nfs_xdr.h

@@ -433,6 +433,7 @@ struct nfs_openargs {
 	enum open_claim_type4	claim;
 	enum createmode4	createmode;
 	const struct nfs4_label *label;
+	umode_t			umask;
 };
 
 struct nfs_openres {
@@ -958,6 +959,7 @@ struct nfs4_create_arg {
 	const struct nfs_fh *		dir_fh;
 	const u32 *			bitmask;
 	const struct nfs4_label		*label;
+	umode_t				umask;
 };
 
 struct nfs4_create_res {