From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754529AbYKKSWV (ORCPT ); Tue, 11 Nov 2008 13:22:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751646AbYKKSWN (ORCPT ); Tue, 11 Nov 2008 13:22:13 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:34436 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751002AbYKKSWM (ORCPT ); Tue, 11 Nov 2008 13:22:12 -0500 Date: Tue, 11 Nov 2008 13:22:11 -0500 From: Christoph Hellwig To: Mikulas Patocka Cc: Alasdair G Kergon , Christoph Hellwig , axboe@kernel.dk, dm-devel , linux-kernel@vger.kernel.org Subject: Re: Queue upcall locking (was: [dm-devel] [RFC][PATCH] fix dm_any_congested() to properly sync up with suspend code path) Message-ID: <20081111182211.GC25049@infradead.org> References: <1225944008.14830.1101.camel@chandra-ubuntu> <20081110135401.GA11606@infradead.org> <20081110142715.GD16649@agk.fab.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 10, 2008 at 09:40:18AM -0500, Mikulas Patocka wrote: > > - If the device is suspended, the response should be that it is > > congested, I'd have thought. > > Yes, but these congestion upcalls are used only for optimization and the > device is suspended for so small time, that it doesn't matter if we > optimize io acces in small moment or not. We use device congested to not block pdflush on a device that can't currently accept I/O. For a suspended device congested is always correct, pdflush will just come back a little later and in the mean time write out stuff that doesn't delay it.