From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755224Ab2IMGjN (ORCPT ); Thu, 13 Sep 2012 02:39:13 -0400 Received: from mga11.intel.com ([192.55.52.93]:50314 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750726Ab2IMGjL (ORCPT ); Thu, 13 Sep 2012 02:39:11 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.80,415,1344236400"; d="scan'208";a="221540340" Date: Thu, 13 Sep 2012 14:39:06 +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: <20120913063906.GA24974@localhost> References: <87wr002z39.fsf@devron.myhome.or.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87wr002z39.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 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. > > Signed-off-by: OGAWA Hirofumi > --- > > fs/fs-writeback.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff -puN fs/fs-writeback.c~noop_backing_dev_info-check-fix fs/fs-writeback.c > --- linux/fs/fs-writeback.c~noop_backing_dev_info-check-fix 2012-09-11 06:12:30.000000000 +0900 > +++ linux-hirofumi/fs/fs-writeback.c 2012-09-11 06:12:30.000000000 +0900 > @@ -120,6 +120,9 @@ __bdi_start_writeback(struct backing_dev > { > struct wb_writeback_work *work; > > + if (!bdi_cap_writeback_dirty(bdi)) > + return; Will someone in the current kernel actually call __bdi_start_writeback() on a BDI_CAP_NO_WRITEBACK bdi? If the answer is no, VM_BUG_ON(!bdi_cap_writeback_dirty(bdi)) looks better. Thanks, Fengguang