nfsd: fix inclusive vfs_fsync_range() end

The vfs_fsync_range() call during write processing got the end of the
range off by one.  The range is inclusive, not exclusive.  The error has
nfsd sync more data than requested -- it's correct but unnecessary
overhead.

The call during commit processing is correct so I copied that pattern in
write processing.  Maybe a helper would be nice but I kept it trivial.

This is untested.  I found it while reviewing code for something else
entirely.
Signed-off-by: Zach Brown <zab@zabbo.net>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/vfs.c

@@ -938,6 +938,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
 	int			stable = *stablep;
 	int			use_wgather;
 	loff_t			pos = offset;
+	loff_t			end = LLONG_MAX;
 	unsigned int		pflags = current->flags;
 
 	if (rqstp->rq_local)
@@ -969,10 +970,13 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
 	fsnotify_modify(file);
 
 	if (stable) {
-		if (use_wgather)
+		if (use_wgather) {
 			host_err = wait_for_concurrent_writes(file);
-		else
-			host_err = vfs_fsync_range(file, offset, offset+*cnt, 0);
+		} else {
+			if (*cnt)
+				end = offset + *cnt - 1;
+			host_err = vfs_fsync_range(file, offset, end, 0);
+		}
 	}
 
 out_nfserr: