From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753187Ab2INLNV (ORCPT ); Fri, 14 Sep 2012 07:13:21 -0400 Received: from mail.parknet.co.jp ([210.171.160.6]:38744 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751175Ab2INLNU (ORCPT ); Fri, 14 Sep 2012 07:13:20 -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> <20120913063906.GA24974@localhost> <871ui6e4tl.fsf@devron.myhome.or.jp> Date: Fri, 14 Sep 2012 20:13:05 +0900 In-Reply-To: <871ui6e4tl.fsf@devron.myhome.or.jp> (OGAWA Hirofumi's message of "Thu, 13 Sep 2012 16:53:58 +0900") Message-ID: <87wqzwn9ha.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 OGAWA Hirofumi writes: > 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. >>> >>> 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. > > I guess nobody call it in current kernel though. Hmm.., but we also have > check in __mark_inode_dirty(), nobody should be using it, right? > > If we defined it as the bug, I can't see what BDI_CAP_NO_WRITEBACK wants > to do actually. We are not going to allow to disable the writeback task? ping. You are saying we should change bdi_cap_writeback_dirty(bdi) to VM_BUG_ON() too in __mark_inode_dirty()? And probably, you are going to remove the usage of BDI_CAP_NO_WRITEBACK for sb->s_bdi? > I was going to use this to disable writeback task on my developing FS... -- OGAWA Hirofumi