From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH 11/20] nbd: request_fn fixup Date: Wed, 13 Sep 2006 08:14:40 +0200 Message-ID: <20060913061440.GC23515@kernel.dk> References: <20060912143049.278065000@chello.nl> <20060912144904.197253000@chello.nl> <20060912224710.GB23515@kernel.dk> <45074EF2.3080407@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Peter Zijlstra , linux-mm@kvack.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Linus Torvalds , Andrew Morton , David Miller , Rik van Riel , Daniel Phillips , Pavel Machek Return-path: Received: from brick.kernel.dk ([62.242.22.158]:13088 "EHLO kernel.dk") by vger.kernel.org with ESMTP id S1751606AbWIMGQ0 (ORCPT ); Wed, 13 Sep 2006 02:16:26 -0400 To: Jeff Garzik Content-Disposition: inline In-Reply-To: <45074EF2.3080407@garzik.org> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, Sep 12 2006, Jeff Garzik wrote: > Jens Axboe wrote: > >Generally the block device rule is that once you are invoked due to an > >unplug (or whatever) event, it is the responsibility of the block device > >to run the queue until it's done. So if you bail out of queue handling > >for whatever reason (might be resource starvation in hard- or software), > >you must make sure to reenter queue handling since the device will not > >get replugged while it has requests pending. Unless you run into some > >software resource shortage, running of the queue is done > >deterministically when you know resources are available (ie an io > >completes). The device plugging itself is only ever done when you > >encounter a shortage outside of your control (memory shortage, for > >instance) _and_ you don't already have pending work where you can invoke > >queueing from again. > > Or he could employ the blk_{start,stop}_queue() functions, if that model > is easier for the driver (and brain). Definitely, yes. -- Jens Axboe