NFSD: allow inter server COPY to have a STALE source server fh

The inter server to server COPY source server filehandle
is a foreign filehandle as the COPY is sent to the destination
server.
Signed-off-by: NOlga Kornievskaia <kolga@netapp.com>

fs/nfsd/Kconfig

@@ -134,6 +134,16 @@ config NFSD_FLEXFILELAYOUT
 
 	  If unsure, say N.
 
+config NFSD_V4_2_INTER_SSC
+	bool "NFSv4.2 inter server to server COPY"
+	depends on NFSD_V4 && NFS_V4_1 && NFS_V4_2
+	help
+	  This option enables support for NFSv4.2 inter server to
+	  server copy where the destination server calls the NFSv4.2
+	  client to read the data to copy from the source server.
+
+	  If unsure, say N.
+
 config NFSD_V4_SECURITY_LABEL
 	bool "Provide Security Label support for NFSv4 server"
 	depends on NFSD_V4 && SECURITY

fs/nfsd/nfs4proc.c

@@ -504,12 +504,20 @@ nfsd4_putfh(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	    union nfsd4_op_u *u)
 {
 	struct nfsd4_putfh *putfh = &u->putfh;
+	__be32 ret;
 
 	fh_put(&cstate->current_fh);
 	cstate->current_fh.fh_handle.fh_size = putfh->pf_fhlen;
 	memcpy(&cstate->current_fh.fh_handle.fh_base, putfh->pf_fhval,
 	       putfh->pf_fhlen);
-	return fh_verify(rqstp, &cstate->current_fh, 0, NFSD_MAY_BYPASS_GSS);
+	ret = fh_verify(rqstp, &cstate->current_fh, 0, NFSD_MAY_BYPASS_GSS);
+#ifdef CONFIG_NFSD_V4_2_INTER_SSC
+	if (ret == nfserr_stale && putfh->no_verify) {
+		SET_FH_FLAG(&cstate->current_fh, NFSD4_FH_FOREIGN);
+		ret = 0;
+	}
+#endif
+	return ret;
 }
 
 static __be32
@@ -1957,6 +1965,45 @@ static void svcxdr_init_encode(struct svc_rqst *rqstp,
 		- rqstp->rq_auth_slack;
 }
 
+#ifdef CONFIG_NFSD_V4_2_INTER_SSC
+static void
+check_if_stalefh_allowed(struct nfsd4_compoundargs *args)
+{
+	struct nfsd4_op	*op, *current_op = NULL, *saved_op = NULL;
+	struct nfsd4_copy *copy;
+	struct nfsd4_putfh *putfh;
+	int i;
+
+	/* traverse all operation and if it's a COPY compound, mark the
+	 * source filehandle to skip verification
+	 */
+	for (i = 0; i < args->opcnt; i++) {
+		op = &args->ops[i];
+		if (op->opnum == OP_PUTFH)
+			current_op = op;
+		else if (op->opnum == OP_SAVEFH)
+			saved_op = current_op;
+		else if (op->opnum == OP_RESTOREFH)
+			current_op = saved_op;
+		else if (op->opnum == OP_COPY) {
+			copy = (struct nfsd4_copy *)&op->u;
+			if (!saved_op) {
+				op->status = nfserr_nofilehandle;
+				return;
+			}
+			putfh = (struct nfsd4_putfh *)&saved_op->u;
+			if (!copy->cp_intra)
+				putfh->no_verify = true;
+		}
+	}
+}
+#else
+static void
+check_if_stalefh_allowed(struct nfsd4_compoundargs *args)
+{
+}
+#endif
+
 /*
  * COMPOUND call.
  */
@@ -2005,6 +2052,7 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
 		resp->opcnt = 1;
 		goto encode_op;
 	}
+	check_if_stalefh_allowed(args);
 
 	trace_nfsd_compound(rqstp, args->opcnt);
 	while (!status && resp->opcnt < args->opcnt) {
@@ -2020,13 +2068,14 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
 				op->status = nfsd4_open_omfg(rqstp, cstate, op);
 			goto encode_op;
 		}
-
-		if (!current_fh->fh_dentry) {
+		if (!current_fh->fh_dentry &&
+				!HAS_FH_FLAG(current_fh, NFSD4_FH_FOREIGN)) {
 			if (!(op->opdesc->op_flags & ALLOWED_WITHOUT_FH)) {
 				op->status = nfserr_nofilehandle;
 				goto encode_op;
 			}
-		} else if (current_fh->fh_export->ex_fslocs.migrated &&
+		} else if (current_fh->fh_export &&
+			   current_fh->fh_export->ex_fslocs.migrated &&
 			  !(op->opdesc->op_flags & ALLOWED_ON_ABSENT_FS)) {
 			op->status = nfserr_moved;
 			goto encode_op;

fs/nfsd/nfsfh.h

@@ -35,7 +35,7 @@ typedef struct svc_fh {
 
 	bool			fh_locked;	/* inode locked by us */
 	bool			fh_want_write;	/* remount protection taken */
-
+	int			fh_flags;	/* FH flags */
 #ifdef CONFIG_NFSD_V3
 	bool			fh_post_saved;	/* post-op attrs saved */
 	bool			fh_pre_saved;	/* pre-op attrs saved */
@@ -56,6 +56,9 @@ typedef struct svc_fh {
 #endif /* CONFIG_NFSD_V3 */
 
 } svc_fh;
+#define NFSD4_FH_FOREIGN (1<<0)
+#define SET_FH_FLAG(c, f) ((c)->fh_flags |= (f))
+#define HAS_FH_FLAG(c, f) ((c)->fh_flags & (f))
 
 enum nfsd_fsid {
 	FSID_DEV = 0,

fs/nfsd/xdr4.h

@@ -221,6 +221,7 @@ struct nfsd4_lookup {
 struct nfsd4_putfh {
 	u32		pf_fhlen;           /* request */
 	char		*pf_fhval;          /* request */
+	bool		no_verify;	    /* represents foreigh fh */
 };
 
 struct nfsd4_open {