From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [patch 6/6] mm: fsync livelock avoidance Date: Thu, 11 Dec 2008 15:14:07 -0800 Message-ID: <20081211151407.bacd44e5.akpm@linux-foundation.org> References: <20081210072454.GB27096@wotan.suse.de> <20081210074209.GG27096@wotan.suse.de> <20081211142347.2546b16c.akpm@linux-foundation.org> <20081211224514.GE8294@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, mpatocka@redhat.com To: Nick Piggin Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:54648 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756863AbYLKXO5 (ORCPT ); Thu, 11 Dec 2008 18:14:57 -0500 In-Reply-To: <20081211224514.GE8294@wotan.suse.de> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu, 11 Dec 2008 23:45:14 +0100 Nick Piggin wrote: > On Thu, Dec 11, 2008 at 02:23:47PM -0800, Andrew Morton wrote: > > obtw, > > > > On Wed, 10 Dec 2008 08:42:09 +0100 > > Nick Piggin wrote: > > > > > For simplicity, I have removed the "don't wait for writeout if we hit -EIO" > > > logic from a couple of places. I don't know if this is really worth the added > > > complexity (EIO will still get reported, but it will just take a bit longer; > > > an app can't rely in specific behaviour or timeliness here). > > > > This is ungood. The device layer likes to twiddle thumbs for 30 > > seconds or more when it hits an IO error. We went and made that 30,000 > > or more.. > > It isn't really a good solution anyway, what isn't a good solution to what? > because I think it's much > less likely for writepage to return -EIO directly. Usually they > would come back via data IO completion asynchronously. umm, maybe. If all the file metadata is in pagecache. Often it is not. > And if we are fsyncing so many requests anyway, we are likely going > to start blocking behind them in the submission path anyway (elevator > queues fill up).