From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932653AbZIDGx6 (ORCPT ); Fri, 4 Sep 2009 02:53:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756638AbZIDGx4 (ORCPT ); Fri, 4 Sep 2009 02:53:56 -0400 Received: from brick.kernel.dk ([93.163.65.50]:54588 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756606AbZIDGxz (ORCPT ); Fri, 4 Sep 2009 02:53:55 -0400 Date: Fri, 4 Sep 2009 08:53:57 +0200 From: Jens Axboe To: Christoph Hellwig Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, chris.mason@oracle.com, david@fromorbit.com, tytso@mit.edu, akpm@linux-foundation.org, jack@suse.cz Subject: Re: [PATCH 2/8] writeback: move dirty inodes from super_block to backing_dev_info Message-ID: <20090904065357.GP18599@kernel.dk> References: <1251880967-1136-1-git-send-email-jens.axboe@oracle.com> <1251880967-1136-3-git-send-email-jens.axboe@oracle.com> <20090904025609.GC3658@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090904025609.GC3658@infradead.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 03 2009, Christoph Hellwig wrote: > Clean bdi_start_writeback up a bit: > > > Index: linux-2.6/fs/fs-writeback.c > =================================================================== > --- linux-2.6.orig/fs/fs-writeback.c 2009-09-03 23:50:12.880832607 -0300 > +++ linux-2.6/fs/fs-writeback.c 2009-09-03 23:54:42.372832985 -0300 > @@ -70,13 +70,6 @@ static inline void bdi_work_init(struct > work->state = WS_USED; > } > > -static inline void bdi_work_init_on_stack(struct bdi_work *work, > - struct writeback_control *wbc) > -{ > - bdi_work_init(work, wbc); > - work->state |= WS_ONSTACK; > -} > - > /** > * writeback_in_progress - determine whether there is writeback in progress > * @bdi: the device's backing_dev_info structure. > @@ -207,35 +200,26 @@ static struct bdi_work *bdi_alloc_work(s > > void bdi_start_writeback(struct writeback_control *wbc) > { > - const bool must_wait = wbc->sync_mode == WB_SYNC_ALL; > - struct bdi_work work_stack, *work = NULL; > - > - if (!must_wait) > - work = bdi_alloc_work(wbc); > + struct bdi_work work; > > - if (!work) { > - work = &work_stack; > - bdi_work_init_on_stack(work, wbc); > + if (wbc->sync_mode != WB_SYNC_ALL) { > + struct bdi_work *w = bdi_alloc_work(wbc); > + if (w) { > + bdi_queue_work(wbc->bdi, w); > + return; > + } > } > > - bdi_queue_work(wbc->bdi, work); > + bdi_work_init(&work, wbc); > + work.state |= WS_ONSTACK; > + bdi_queue_work(wbc->bdi, &work); > > /* > * If the sync mode is WB_SYNC_ALL, block waiting for the work to > - * complete. If not, we only need to wait for the work to be started, > - * if we allocated it on-stack. We use the same mechanism, if the > - * wait bit is set in the bdi_work struct, then threads will not > - * clear pending until after they are done. > - * > - * Note that work == &work_stack if must_wait is true, so we don't > - * need to do call_rcu() here ever, since the completion path will > - * have done that for us. > + * complete. > */ > - if (must_wait || work == &work_stack) { > - bdi_wait_on_work_clear(work); > - if (work != &work_stack) > - call_rcu(&work->rcu_head, bdi_work_free); > - } > + if (wbc->sync_mode == WB_SYNC_ALL) > + bdi_wait_on_work_clear(&work); > } That doesn't work, you have to wait for on-stack work. So either we just punt and not do anything for WB_SYNC_NONE if the allocation fails, or we punt to stack and do the wait. Since it's a cleaning action and allocation fails, falling back to the stack and waiting seems like the most appropriate choice. -- Jens Axboe