NFS: Ensure we return zero if applications attempt to write zero bytes

A zero byte count direct write request should be a successful no-op, not an
error.

Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 88d5d1c..4d726e9 100644 (file)
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -890,6 +890,8 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
        retval = generic_write_checks(file, &pos, &count, 0);
        if (retval)
                goto out;
+       if (!count)
+               goto out;       /* return 0 */
 
        retval = -EINVAL;
        if ((ssize_t) count < 0)