NFS: Don't hash the negative dentry when optimising for an O_EXCL open

We don't want to leave an unverified hashed negative dentry if the
exclusive create fails to complete.

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

fs/nfs/dir.c

@@ -992,9 +992,10 @@ static struct dentry *nfs_atomic_lookup(struct inode *dir, struct dentry *dentry
 	}
 	dentry->d_op = NFS_PROTO(dir)->dentry_ops;
 
-	/* Let vfs_create() deal with O_EXCL */
+	/* Let vfs_create() deal with O_EXCL. Instantiate, but don't hash
+	 * the dentry. */
 	if (nd->intent.open.flags & O_EXCL) {
-		d_add(dentry, NULL);
+		d_instantiate(dentry, NULL);
 		goto out;
 	}
 

fs/nfs/nfs4proc.c

@@ -1879,11 +1879,12 @@ nfs4_proc_create(struct inode *dir, struct dentry *dentry, struct iattr *sattr,
 	}
 	state = nfs4_do_open(dir, &path, flags, sattr, cred);
 	put_rpccred(cred);
+	d_drop(dentry);
 	if (IS_ERR(state)) {
 		status = PTR_ERR(state);
 		goto out;
 	}
-	d_instantiate(dentry, igrab(state->inode));
+	d_add(dentry, igrab(state->inode));
 	if (flags & O_EXCL) {
 		struct nfs_fattr fattr;
 		status = nfs4_do_setattr(state->inode, &fattr, sattr, state);