9p: Pass the correct end of buffer to p9stat_read

Pass the correct end of the buffer to p9stat_read.
Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_dir.c

@@ -146,7 +146,7 @@ static int v9fs_dir_readdir(struct file *filp, void *dirent, filldir_t filldir)
 		while (rdir->head < rdir->tail) {
 			p9stat_init(&st);
 			err = p9stat_read(rdir->buf + rdir->head,
-						buflen - rdir->head, &st,
+						rdir->tail - rdir->head, &st,
 						fid->clnt->proto_version);
 			if (err) {
 				P9_DPRINTK(P9_DEBUG_VFS, "returned %d\n", err);