Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754931AbbHNLOQ (ORCPT ); Fri, 14 Aug 2015 07:14:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:43364 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754239AbbHNLOO (ORCPT ); Fri, 14 Aug 2015 07:14:14 -0400 Date: Fri, 14 Aug 2015 13:14:09 +0200 From: Jan Kara To: Tejun Heo Cc: Jens Axboe , Jan Kara , Eryu Guan , xfs@oss.sgi.com, axboe@fb.com, Dave Chinner , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH block/for-linus] writeback: fix syncing of I_DIRTY_TIME inodes Message-ID: <20150814111408.GB8710@quack.suse.cz> References: <20150812101204.GE17933@dhcp-13-216.nay.redhat.com> <20150813004435.GN3902@dastard> <20150813224415.GG4496@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150813224415.GG4496@mtj.duckdns.org> 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 Content-Length: 3550 Lines: 101 Hello, On Thu 13-08-15 18:44:15, Tejun Heo wrote: > e79729123f63 ("writeback: don't issue wb_writeback_work if clean") > updated writeback path to avoid kicking writeback work items if there > are no inodes to be written out; unfortunately, the avoidance logic > was too aggressive and made sync_inodes_sb() skip I_DIRTY_TIME inodes. > This patch fixes the breakage by > > * Removing bdi_has_dirty_io() shortcut from bdi_split_work_to_wbs(). > The callers are already testing the condition. > > * Removing bdi_has_dirty_io() shortcut from sync_inodes_sb() so that > it always calls into bdi_split_work_to_wbs(). > > * Making bdi_split_work_to_wbs() consider the b_dirty_time list for > WB_SYNC_ALL writebacks. > > Signed-off-by: Tejun Heo > Fixes: e79729123f63 ("writeback: don't issue wb_writeback_work if clean") > Cc: Ted Ts'o > Cc: Jan Kara So the patch looks good to me. But the fact that is fixes Eryu's problem means there is something fishy going on. Either inodes get wrongly attached to b_dirty_time list or bdi_has_dirty_io() somehow misbehaves only temporarily and we don't catch it with the debug patch. Can we add a test to wb_has_dirty_io() to also check whether it matches bdi_has_dirty_io()? Since Eryu doesn't use lazytime (I assume, Eryu, please speak up if you do), we could also warn if b_dirty_time lists get non-empty. Hmm? Honza > --- > Hello, > > So, this fixes I_DIRTY_TIME syncing problem for ext4 but AFAICS xfs > doesn't even use the generic inode metadata writeback path, so this > most likely won't do anything for the originally reported problem. > I'll post another patch for debugging. > > Thanks. > > fs/fs-writeback.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -844,14 +844,15 @@ static void bdi_split_work_to_wbs(struct > struct wb_iter iter; > > might_sleep(); > - > - if (!bdi_has_dirty_io(bdi)) > - return; > restart: > rcu_read_lock(); > bdi_for_each_wb(wb, bdi, &iter, next_blkcg_id) { > - if (!wb_has_dirty_io(wb) || > - (skip_if_busy && writeback_in_progress(wb))) > + /* SYNC_ALL writes out I_DIRTY_TIME too */ > + if (!wb_has_dirty_io(wb) && > + (base_work->sync_mode == WB_SYNC_NONE || > + list_empty(&wb->b_dirty_time))) > + continue; > + if (skip_if_busy && writeback_in_progress(wb)) > continue; > > base_work->nr_pages = wb_split_bdi_pages(wb, nr_pages); > @@ -899,8 +900,7 @@ static void bdi_split_work_to_wbs(struct > { > might_sleep(); > > - if (bdi_has_dirty_io(bdi) && > - (!skip_if_busy || !writeback_in_progress(&bdi->wb))) { > + if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) { > base_work->auto_free = 0; > base_work->single_wait = 0; > base_work->single_done = 0; > @@ -2275,8 +2275,8 @@ void sync_inodes_sb(struct super_block * > }; > struct backing_dev_info *bdi = sb->s_bdi; > > - /* Nothing to do? */ > - if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info) > + /* bdi_has_dirty() ignores I_DIRTY_TIME but we can't, always kick wbs */ > + if (bdi == &noop_backing_dev_info) > return; > WARN_ON(!rwsem_is_locked(&sb->s_umount)); > > -- Jan Kara SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/