From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Moyer Subject: Re: [PATCH V2] writeback: fix hung_task alarm when sync block Date: Wed, 13 Jun 2012 10:27:50 -0400 Message-ID: References: <1339562553-10035-1-git-send-email-liwp.linux@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Fengguang Wu , Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Gavin Shan To: Wanpeng Li Return-path: In-Reply-To: <1339562553-10035-1-git-send-email-liwp.linux@gmail.com> (Wanpeng Li's message of "Wed, 13 Jun 2012 12:42:33 +0800") Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Wanpeng Li writes: > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index f2d0109..df879ee 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -1311,7 +1311,11 @@ void writeback_inodes_sb_nr(struct super_block *sb, > > WARN_ON(!rwsem_is_locked(&sb->s_umount)); > bdi_queue_work(sb->s_bdi, &work); > - wait_for_completion(&done); > + if (sysctl_hung_task_timeout_secs) > + while (!wait_for_completion_timeout(&done, HZ/2)) > + ; > + else > + wait_for_completion(&done); > } > EXPORT_SYMBOL(writeback_inodes_sb_nr); Is it really expected that writeback_inodes_sb_nr will routinely queue up more than 2 seconds worth of I/O (Yes, I understand that it isn't the only entity issuing I/O)? For devices that are really slow, it may make more sense to tune the system so that you don't have too much writeback I/O submitted at once. Dropping nr_requests for the given queue should fix this situation, I would think. This really feels like we're papering over the problem. Cheers, Jeff