From owner-freebsd-arch@FreeBSD.ORG Sun Jan 22 18:33:51 2012 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 8E80D106564A; Sun, 22 Jan 2012 18:33:51 +0000 (UTC) (envelope-from to.my.trociny@gmail.com) Received: from mail-bk0-f54.google.com (mail-bk0-f54.google.com [209.85.214.54]) by mx1.freebsd.org (Postfix) with ESMTP id A99738FC12; Sun, 22 Jan 2012 18:33:50 +0000 (UTC) Received: by bkbc12 with SMTP id c12so2399263bkb.13 for ; Sun, 22 Jan 2012 10:33:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=from:to:cc:subject:references:x-comment-to:sender:date:in-reply-to :message-id:user-agent:mime-version:content-type; bh=BaiUUB+cTOitl7lYmX6nW8sQs3ep0sECp5JT4PvWcY4=; b=dULoKdNuZVWX7MX3LZQv1KrhgRFKqxk4NKsVW3WpxEAoljHnnsCPXDW3B6Er2h6fbl 3kzD5DYtyzjI7yf6TjEMEXnquaf49XtRdso3jeB2ea+9vI/fb5WRw7Z9Xd3fRLzNSMD+ TrPq6yFEUGOG0lF92XNtv8cCh+F0nPd1p0xys= Received: by 10.204.150.7 with SMTP id w7mr2002241bkv.107.1327257229431; Sun, 22 Jan 2012 10:33:49 -0800 (PST) Received: from localhost ([95.69.173.122]) by mx.google.com with ESMTPS id ga13sm22466594bkc.5.2012.01.22.10.33.47 (version=TLSv1/SSLv3 cipher=OTHER); Sun, 22 Jan 2012 10:33:48 -0800 (PST) From: Mikolaj Golub To: Kostik Belousov References: <86sjjobzmn.fsf@kopusha.home.net> <86fwfnti5t.fsf@kopusha.home.net> <20120112215106.GC31224@deviant.kiev.zoral.com.ua> X-Comment-To: Kostik Belousov Sender: Mikolaj Golub Date: Sun, 22 Jan 2012 20:33:45 +0200 In-Reply-To: <20120112215106.GC31224@deviant.kiev.zoral.com.ua> (Kostik Belousov's message of "Thu, 12 Jan 2012 23:51:06 +0200") Message-ID: <86hazntwmu.fsf@kopusha.home.net> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.3 (berkeley-unix) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Robert N. M. Watson" , freebsd-arch@freebsd.org Subject: Re: unix domain sockets on nullfs(5) X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 22 Jan 2012 18:33:51 -0000 There was a bug in my patch: for vop_unpdetach it wanted the vnode to be exclusively locked, while it was called from the context (uipc_detach) where the vnode is not locked. It looks it is OK that the vnode is not locked here: the operation is to null vp->v_socket, and currently the only place where it is concurently accessed is in unp_connect(), and it is protected by the linkage lock. So I updated my patch to have "= = =" for unpdetach vp. http://people.freebsd.org/~trociny/VOP_UNP.2.patch On Thu, 12 Jan 2012 23:51:06 +0200 Kostik Belousov wrote: KB> On Thu, Jan 12, 2012 at 09:39:53PM +0000, Robert N. M. Watson wrote: >> >> I still find myself worried by the fact that unp->unp_vnode points at the >> nullfs vnode rather than the underlying vnode, but haven't yet managed to >> identify any actual bugs that would result. I'll continue pondering it >> over the weekend :-). KB> I think I know what could go wrong there, but due to other bug, this KB> wrongness cannot be realized now. KB> Issue is that for the forced unmount, the unp_vnode is reclaimed, so that KB> the unix domain sockets code references freed memory after reclaim. Just to have this clear, as I understand this problem with reclaim is orthogonal to the initial issue and would also exist without my patch too? Could you please tell what is the other bug? I see that after force unmount, in vflush() we call vgonel() for every vnode, and vgonel() does VOP_CLOSE(), VOP_INACTIVE(), VOP_RECLAIM(), sets v_type = VBAD, but vnode's usecount is not decreased so if a node was active it may not be freed when vdropl() is called. Was the usecount supposed to be dropped somewere in this path (when VOP_CLOSE() is called?) and this is the bug you mean or it is something else? Currently the usecount (for both VREG and VSOCK) is deacreased when the process finaly closes the discriptor. KB> Probably, some helper should provided by uipc_usrreq, called from VOP_RECLAIM() KB> implementations for VSOCK types of vnodes. I would not be very happy with adding the helper to every fs's VOP_RECLAIM() implementation :-). Couldn't it be somevere in the common code, e.g. in vflush()? Here is the patch I tried: http://people.freebsd.org/~trociny/vsock_reclaim.patch I don't know though how to export this helper function and what name would be appropriate: there are no other exported functions in uipc_usrreq.c. Thanks, -- Mikolaj Golub