Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759077AbZCZPqi (ORCPT ); Thu, 26 Mar 2009 11:46:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757857AbZCZPqO (ORCPT ); Thu, 26 Mar 2009 11:46:14 -0400 Received: from brick.kernel.dk ([93.163.65.50]:52757 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755645AbZCZPqN (ORCPT ); Thu, 26 Mar 2009 11:46:13 -0400 Date: Thu, 26 Mar 2009 16:46:11 +0100 From: Jens Axboe To: Hugh Dickins Cc: Ric Wheeler , Jeff Garzik , Linus Torvalds , Theodore Tso , Ingo Molnar , Alan Cox , Arjan van de Ven , Andrew Morton , Peter Zijlstra , Nick Piggin , David Rees , Jesper Krogh , Linux Kernel Mailing List Subject: Re: Linux 2.6.29 Message-ID: <20090326154610.GH27476@kernel.dk> References: <49C93AB0.6070300@garzik.org> <20090325093913.GJ27476@kernel.dk> <49CA86BD.6060205@garzik.org> <20090325194341.GB27476@kernel.dk> <49CA8ADA.3040709@redhat.com> <20090325195747.GC27476@kernel.dk> <20090326085748.GH27476@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1361 Lines: 32 On Thu, Mar 26 2009, Hugh Dickins wrote: > On Thu, 26 Mar 2009, Jens Axboe wrote: > > On Wed, Mar 25 2009, Hugh Dickins wrote: > > > > > > Tangential question, but am I right in thinking that BIO_RW_BARRIER > > > similarly bars across all partitions, whereas its WRITE_BARRIER and > > > DISCARD_BARRIER users would actually prefer it to apply to just one? > > > > All the barriers refer to just that range which the barrier itself > > references. > > Ah, thank you: then I had a fundamental misunderstanding of them, > and need to go away and work that out some more. > > Though I didn't read it before asking, doesn't the I/O Barriers section > of Documentation/block/biodoc.txt give a very different impression? I'm sensing a miscommunication here... The ordering constraint is across devices, at least that is how it is implemented. For file system barriers (like BIO_RW_BARRIER), it could be per-partition instead. Doing so would involve some changes at the block layer side, not necessarily trivial. So I think you were asking about ordering, I was answering about the write guarantee :-) -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/