nfsd41: CREATE_EXCLUSIVE4_1

Implement the CREATE_EXCLUSIVE4_1 open mode conforming to
http://tools.ietf.org/html/draft-ietf-nfsv4-minorversion1-26

This mode allows the client to atomically create a file
if it doesn't exist while setting some of its attributes.

It must be implemented if the server supports persistent
reply cache and/or pnfs.
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/nfs4proc.c

@@ -93,6 +93,21 @@ do_open_lookup(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_o
 	open->op_truncate = 0;
 
 	if (open->op_create) {
+		/* FIXME: check session persistence and pnfs flags.
+		 * The nfsv4.1 spec requires the following semantics:
+		 *
+		 * Persistent   | pNFS   | Server REQUIRED | Client Allowed
+		 * Reply Cache  | server |                 |
+		 * -------------+--------+-----------------+--------------------
+		 * no           | no     | EXCLUSIVE4_1    | EXCLUSIVE4_1
+		 *              |        |                 | (SHOULD)
+		 *              |        | and EXCLUSIVE4  | or EXCLUSIVE4
+		 *              |        |                 | (SHOULD NOT)
+		 * no           | yes    | EXCLUSIVE4_1    | EXCLUSIVE4_1
+		 * yes          | no     | GUARDED4        | GUARDED4
+		 * yes          | yes    | GUARDED4        | GUARDED4
+		 */
+
 		/*
 		 * Note: create modes (UNCHECKED,GUARDED...) are the same
 		 * in NFSv4 as in v3.

fs/nfsd/nfs4xdr.c

@@ -260,6 +260,12 @@ static u32 nfsd_attrmask[] = {
 	NFSD_WRITEABLE_ATTRS_WORD2
 };
 
+static u32 nfsd41_ex_attrmask[] = {
+	NFSD_SUPPATTR_EXCLCREAT_WORD0,
+	NFSD_SUPPATTR_EXCLCREAT_WORD1,
+	NFSD_SUPPATTR_EXCLCREAT_WORD2
+};
+
 static __be32
 nfsd4_decode_fattr(struct nfsd4_compoundargs *argp, u32 *bmval, u32 *writable,
 		   struct iattr *iattr, struct nfs4_acl **acl)
@@ -684,6 +690,17 @@ nfsd4_decode_open(struct nfsd4_compoundargs *argp, struct nfsd4_open *open)
 			READ_BUF(8);
 			COPYMEM(open->op_verf.data, 8);
 			break;
+		case NFS4_CREATE_EXCLUSIVE4_1:
+			if (argp->minorversion < 1)
+				goto xdr_error;
+			READ_BUF(8);
+			COPYMEM(open->op_verf.data, 8);
+			status = nfsd4_decode_fattr(argp, open->op_bmval,
+				nfsd41_ex_attrmask, &open->op_iattr,
+				&open->op_acl);
+			if (status)
+				goto out;
+			break;
 		default:
 			goto xdr_error;
 		}

include/linux/nfs4.h

@@ -368,7 +368,13 @@ enum opentype4 {
 enum createmode4 {
 	NFS4_CREATE_UNCHECKED = 0,
 	NFS4_CREATE_GUARDED = 1,
-	NFS4_CREATE_EXCLUSIVE = 2
+	NFS4_CREATE_EXCLUSIVE = 2,
+	/*
+	 * New to NFSv4.1. If session is persistent,
+	 * GUARDED4 MUST be used. Otherwise, use
+	 * EXCLUSIVE4_1 instead of EXCLUSIVE4.
+	 */
+	NFS4_CREATE_EXCLUSIVE4_1 = 3
 };
 
 enum limit_by4 {

include/linux/nfsd/xdr4.h

@@ -219,10 +219,8 @@ struct nfsd4_open {
 	u32		op_create;     	    /* request */
 	u32		op_createmode;      /* request */
 	u32		op_bmval[3];        /* request */
-	union {                             /* request */
-		struct iattr	iattr;                      /* UNCHECKED4,GUARDED4 */
+	struct iattr	iattr;              /* UNCHECKED4, GUARDED4, EXCLUSIVE4_1 */
 	nfs4_verifier	verf;               /* EXCLUSIVE4 */
-	} u;
 	clientid_t	op_clientid;        /* request */
 	struct xdr_netobj op_owner;           /* request */
 	u32		op_seqid;           /* request */
@@ -236,8 +234,8 @@ struct nfsd4_open {
 	struct nfs4_stateowner *op_stateowner; /* used during processing */
 	struct nfs4_acl *op_acl;
 };
-#define op_iattr	u.iattr
-#define op_verf		u.verf
+#define op_iattr	iattr
+#define op_verf		verf
 
 struct nfsd4_open_confirm {
 	stateid_t	oc_req_stateid		/* request */;