9p: Pass the correct end of buffer to p9dirent_read

A patch was accepted recently for sending correct buffer size to p9stat_read.
We need a similar patch in v9fs_dir_readdir_dotl to send correct end of buffer
to p9dirent_read.
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_dir.c

@@ -242,7 +242,8 @@ static int v9fs_dir_readdir_dotl(struct file *filp, void *dirent,
 		while (rdir->head < rdir->tail) {
 
 			err = p9dirent_read(rdir->buf + rdir->head,
-						buflen - rdir->head, &curdirent,
+						rdir->tail - rdir->head,
+						&curdirent,
 						fid->clnt->proto_version);
 			if (err < 0) {
 				P9_DPRINTK(P9_DEBUG_VFS, "returned %d\n", err);