From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: Queue upcall locking (was: [dm-devel] [RFC][PATCH] fix dm_any_congested() to properly sync up with suspend code path) Date: Tue, 11 Nov 2008 13:22:11 -0500 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 Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Mikulas Patocka Cc: Alasdair G Kergon , Christoph Hellwig , axboe@kernel.dk, dm-devel , linux-kernel@vger.kernel.org List-Id: dm-devel.ids 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.