From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f72.google.com (mail-pa0-f72.google.com [209.85.220.72]) by kanga.kvack.org (Postfix) with ESMTP id 7041F6B0038 for ; Mon, 12 Sep 2016 04:05:20 -0400 (EDT) Received: by mail-pa0-f72.google.com with SMTP id fu12so53048738pac.1 for ; Mon, 12 Sep 2016 01:05:20 -0700 (PDT) Received: from mail-pf0-x241.google.com (mail-pf0-x241.google.com. [2607:f8b0:400e:c00::241]) by mx.google.com with ESMTPS id ta8si20477452pab.231.2016.09.12.01.05.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 12 Sep 2016 01:05:19 -0700 (PDT) Received: by mail-pf0-x241.google.com with SMTP id 128so7744432pfb.0 for ; Mon, 12 Sep 2016 01:05:19 -0700 (PDT) Date: Mon, 12 Sep 2016 18:05:07 +1000 From: Nicholas Piggin Subject: Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) Message-ID: <20160912180507.533b3549@roar.ozlabs.ibm.com> In-Reply-To: <20160912075128.GB21474@infradead.org> References: <20160908225636.GB15167@linux.intel.com> <20160912052703.GA1897@infradead.org> <20160912075128.GB21474@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Hellwig Cc: Oliver O'Halloran , Yumei Huang , Michal Hocko , Xiao Guangrong , Andrew Morton , KVM list , Linux MM , Gleb Natapov , "linux-nvdimm@lists.01.org" , mtosatti@redhat.com, "linux-kernel@vger.kernel.org" , Dave Hansen , Stefan Hajnoczi , linux-fsdevel , Paolo Bonzini On Mon, 12 Sep 2016 00:51:28 -0700 Christoph Hellwig wrote: > On Mon, Sep 12, 2016 at 05:25:15PM +1000, Oliver O'Halloran wrote: > > What are the problems here? Is this a matter of existing filesystems > > being unable/unwilling to support this or is it just fundamentally > > broken? > > It's a fundamentally broken model. See Dave's post that actually was > sent slightly earlier then mine for the list of required items, which > is fairly unrealistic. You could probably try to architect a file > system for it, but I doubt it would gain much traction. It's not fundamentally broken, it just doesn't fit well existing filesystems. Dave's post of requirements is also wrong. A filesystem does not have to guarantee all that, it only has to guarantee that is the case for a given block after it has a mapping and page fault returns, other operations can be supported by invalidating mappings, etc. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org