[PATCH] NFSv4: Fix up races in nfs4_proc_setattr()

 If we do not hold a valid stateid that is open for writes, there is little
 point in doing an extra open of the file, as the RFC does not appear to
 mandate this...

 Make setattr use the correct stateid if we're holding mandatory byte
 range locks.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -756,11 +756,10 @@ static int _nfs4_do_setattr(struct nfs_server *server, struct nfs_fattr *fattr,
 
         fattr->valid = 0;
 
-	if (state != NULL)
+	if (state != NULL) {
 		msg.rpc_cred = state->owner->so_cred;
-	if (sattr->ia_valid & ATTR_SIZE)
-		nfs4_copy_stateid(&arg.stateid, state, NULL);
-	else
+		nfs4_copy_stateid(&arg.stateid, state, current->files);
+	} else
 		memcpy(&arg.stateid, &zero_stateid, sizeof(arg.stateid));
 
 	return rpc_call_sync(server->client, &msg, 0);
@@ -1124,47 +1123,31 @@ static int
 nfs4_proc_setattr(struct dentry *dentry, struct nfs_fattr *fattr,
 		  struct iattr *sattr)
 {
-	struct inode *		inode = dentry->d_inode;
-	int			size_change = sattr->ia_valid & ATTR_SIZE;
-	struct nfs4_state	*state = NULL;
-	int need_iput = 0;
+	struct rpc_cred *cred;
+	struct inode *inode = dentry->d_inode;
+	struct nfs4_state *state;
 	int status;
 
 	fattr->valid = 0;
 	
-	if (size_change) {
-		struct rpc_cred *cred = rpcauth_lookupcred(NFS_SERVER(inode)->client->cl_auth, 0);
-		if (IS_ERR(cred))
-			return PTR_ERR(cred);
+	cred = rpcauth_lookupcred(NFS_SERVER(inode)->client->cl_auth, 0);
+	if (IS_ERR(cred))
+		return PTR_ERR(cred);
+	/* Search for an existing WRITE delegation first */
+	state = nfs4_open_delegated(inode, FMODE_WRITE, cred);
+	if (!IS_ERR(state)) {
+		/* NB: nfs4_open_delegated() bumps the inode->i_count */
+		iput(inode);
+	} else {
+		/* Search for an existing open(O_WRITE) stateid */
 		state = nfs4_find_state(inode, cred, FMODE_WRITE);
-		if (state == NULL) {
-			state = nfs4_open_delegated(dentry->d_inode,
-					FMODE_WRITE, cred);
-			if (IS_ERR(state))
-				state = nfs4_do_open(dentry->d_parent->d_inode,
-						dentry, FMODE_WRITE,
-						NULL, cred);
-			need_iput = 1;
-		}
-		put_rpccred(cred);
-		if (IS_ERR(state))
-			return PTR_ERR(state);
-
-		if (state->inode != inode) {
-			printk(KERN_WARNING "nfs: raced in setattr (%p != %p), returning -EIO\n", inode, state->inode);
-			status = -EIO;
-			goto out;
-		}
 	}
+
 	status = nfs4_do_setattr(NFS_SERVER(inode), fattr,
 			NFS_FH(inode), sattr, state);
-out:
-	if (state) {
-		inode = state->inode;
+	if (state != NULL)
 		nfs4_close_state(state, FMODE_WRITE);
-		if (need_iput)
-			iput(inode);
-	}
+	put_rpccred(cred);
 	return status;
 }