From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756188Ab2IMAdp (ORCPT ); Wed, 12 Sep 2012 20:33:45 -0400 Received: from mga01.intel.com ([192.55.52.88]:7188 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751929Ab2IMAdn (ORCPT ); Wed, 12 Sep 2012 20:33:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.80,413,1344236400"; d="scan'208";a="221447563" Date: Thu, 13 Sep 2012 08:33:37 +0800 From: Fengguang Wu To: OGAWA Hirofumi Cc: viro@zeniv.linux.org.uk, jack@suse.cz, hch@lst.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Fix queueing work if !bdi_cap_writeback_dirty() Message-ID: <20120913003337.GA16363@localhost> References: <87wr002z39.fsf@devron.myhome.or.jp> <20120912024249.GB17922@localhost> <87sjan3c27.fsf@devron.myhome.or.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87sjan3c27.fsf@devron.myhome.or.jp> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 12, 2012 at 05:00:48PM +0900, OGAWA Hirofumi wrote: > Fengguang Wu writes: > > > On Wed, Sep 12, 2012 at 03:28:42AM +0900, OGAWA Hirofumi wrote: > >> > >> If bdi has BDI_CAP_NO_WRITEBACK, bdi_forker_thread() doesn't start > >> writeback thread. This means there is no consumer of work item made > >> by bdi_queue_work(). > >> > >> This adds to checking of !bdi_cap_writeback_dirty(sb->s_bdi) before > >> calling bdi_queue_work(), otherwise queued work never be consumed. > > > > Thanks for catching this! Does this bug have any side effects other > > than memory leaking? > > > > It may be possible for some caller that actually expect it to do some > > work to make progress, otherwise will eventually block. If so, we'll > > need to fix the caller. > > If used custom bdi with BDI_CAP_NO_WRITEBACK, wait_for_completion() > (e.g. sync_inodes_sb()) will be blocked forever. The sync(2) block cannot be fixed by this patch? > I tested by custom bdi with BDI_CAP_NO_WRITEBACK - sync(2) blocked > forever by this reason. What's your test script? How do you create/use that custom bdi? Thanks, Fengguang