[PATCH 5/9] nfsd: NFSv3 should allow zero length writes

[trondmy@kernel.org]

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 4d57befdac6e..38fdfcbb079e 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -969,6 +969,9 @@ 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 a3bbe5ce4570..d1ccf37a4588 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1692,7 +1692,7 @@ unsigned int svc_fill_write_vector(struct svc_rqst *rqstp, struct page **pages,
 	 * 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