From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamie Lokier Subject: Re: [PATCH 0/7] Discard requests, v2 Date: Wed, 13 Aug 2008 13:19:41 +0100 Message-ID: <20080813121941.GA8505@shareable.org> References: <20080812091446.GF20055@kernel.dk> <1218535205.2977.131.camel@pmac.infradead.org> <20080812105428.GG20055@kernel.dk> <1218539797.2977.147.camel@pmac.infradead.org> <1218543544.2977.158.camel@pmac.infradead.org> <20080812125315.GH20055@kernel.dk> <1218546257.2977.167.camel@pmac.infradead.org> <1218556054.2977.188.camel@pmac.infradead.org> <20080812180422.GA21341@shareable.org> <1218622976.2977.257.camel@pmac.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jens Axboe , Andrew Morton , Ric Wheeler , linux-fsdevel@vger.kernel.org, gilad@codefidence.com, matthew@wil.cx To: David Woodhouse Return-path: Received: from mail2.shareable.org ([80.68.89.115]:49548 "EHLO mail2.shareable.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751802AbYHMMUC (ORCPT ); Wed, 13 Aug 2008 08:20:02 -0400 Content-Disposition: inline In-Reply-To: <1218622976.2977.257.camel@pmac.infradead.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: David Woodhouse wrote: > On Tue, 2008-08-12 at 19:04 +0100, Jamie Lokier wrote: > > David Woodhouse wrote: > > > Anything else I need to address before you pull the tree? Any comment on > > > the BLKDISCARD ioctl? I've left that one using the non-barrier version > > > since it's waiting for it anyway, and shouldn't be happening > > > concurrently with anything else. > > > > What makes you think a userspace filesystem or database wouldn't call > > BLKDISCARD concurrently with anything else? > > The BLKDISCARD ioctl is synchronous -- I haven't done an aio version of > it. Issuing a write to the same sectors before it finishes would be kind > of silly. You're right, as long as it's not aio, there's no way to sensibly order it with concurrent writes; I take it back. (Aside: You would issue writes to *different* sectors before BLKDISCARD, and they must be done in that order. That is how you implement journalling.) -- Jamie