From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753344Ab2ILIBA (ORCPT ); Wed, 12 Sep 2012 04:01:00 -0400 Received: from mail.parknet.co.jp ([210.171.160.6]:37855 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751154Ab2ILIA6 (ORCPT ); Wed, 12 Sep 2012 04:00:58 -0400 From: OGAWA Hirofumi To: Fengguang Wu 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() References: <87wr002z39.fsf@devron.myhome.or.jp> <20120912024249.GB17922@localhost> Date: Wed, 12 Sep 2012 17:00:48 +0900 In-Reply-To: <20120912024249.GB17922@localhost> (Fengguang Wu's message of "Wed, 12 Sep 2012 10:42:49 +0800") Message-ID: <87sjan3c27.fsf@devron.myhome.or.jp> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.2.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. I tested by custom bdi with BDI_CAP_NO_WRITEBACK - sync(2) blocked forever by this reason. Thanks. -- OGAWA Hirofumi