From: J. Bruce Fields <bfields@redhat.com>
Date: Thu, 15 Nov 2018 16:21:40 +0000 (-0500)
Subject: nfsd4: zero-length WRITE should succeed
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=fdec6114ee1f;p=linux.git

nfsd4: zero-length WRITE should succeed

Zero-length writes are legal; from 5661 section 18.32.3: "If the count
is zero, the WRITE will succeed and return a count of zero subject to
permissions checking".

This check is unnecessary and is causing zero-length reads to return
EINVAL.

Cc: stable@vger.kernel.org
Fixes: 3fd9557aec91 "NFSD: Refactor the generic write vector fill helper"
Cc: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index d505990dac7c9..c364acbb6aba0 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1016,8 +1016,6 @@ nfsd4_write(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 
 	nvecs = svc_fill_write_vector(rqstp, write->wr_pagelist,
 				      &write->wr_head, write->wr_buflen);
-	if (!nvecs)
-		return nfserr_io;
 	WARN_ON_ONCE(nvecs > ARRAY_SIZE(rqstp->rq_vec));
 
 	status = nfsd_vfs_write(rqstp, &cstate->current_fh, filp,