From:   trondmy@kernel.org
To:     Chuck Lever <chuck.lever@oracle.com>,
        "J. Bruce Fields" <bfields@redhat.com>
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH v2 06/10] nfsd: NFSv3 should allow zero length writes
Date:   Sat, 18 Dec 2021 20:37:59 -0500
Message-Id: <20211219013803.324724-7-trondmy@kernel.org>
In-Reply-To: <20211219013803.324724-6-trondmy@kernel.org>
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From: Trond Myklebust <trond.myklebust@hammerspace.com>

According to RFC1813: "If count is 0, the WRITE will succeed
and return a count of 0, barring errors due to permissions checking."

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfsd/vfs.c    | 3 +++
 net/sunrpc/svc.c | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index eb9818432149..85e579aa6944 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -967,6 +967,9 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 
 	trace_nfsd_write_opened(rqstp, fhp, offset, *cnt);
 
+	if (!*cnt)
+		return nfs_ok;
+
 	if (sb->s_export_op)
 		exp_op_flags = sb->s_export_op->flags;
 
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 4292278a9552..72a7822fd257 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1638,7 +1638,7 @@ unsigned int svc_fill_write_vector(struct svc_rqst *rqstp,
 	 * entirely in rq_arg.pages. In this case, @first is empty.
 	 */
 	i = 0;
-	if (first->iov_len) {
+	if (first->iov_len || !total) {
 		vec[i].iov_base = first->iov_base;
 		vec[i].iov_len = min_t(size_t, total, first->iov_len);
 		total -= vec[i].iov_len;
-- 
2.33.1