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 CBFCA6B0253 for ; Mon, 12 Sep 2016 11:01:56 -0400 (EDT) Received: by mail-pa0-f72.google.com with SMTP id fu12so72396101pac.1 for ; Mon, 12 Sep 2016 08:01:56 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org. [2001:1868:205::9]) by mx.google.com with ESMTPS id p75si1292599pfd.106.2016.09.12.08.01.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 12 Sep 2016 08:01:56 -0700 (PDT) Date: Mon, 12 Sep 2016 08:01:48 -0700 From: Christoph Hellwig Subject: Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps) Message-ID: <20160912150148.GA10039@infradead.org> References: <20160908225636.GB15167@linux.intel.com> <20160912052703.GA1897@infradead.org> <20160912075128.GB21474@infradead.org> <20160912180507.533b3549@roar.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160912180507.533b3549@roar.ozlabs.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Nicholas Piggin Cc: Christoph Hellwig , 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, Sep 12, 2016 at 06:05:07PM +1000, Nicholas Piggin wrote: > It's not fundamentally broken, it just doesn't fit well existing > filesystems. Or the existing file system architecture for that matter. Which makes it a fundamentally broken model. > 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. Which doesn't really matter if your use case is manipulating fully mapped files. But back to the point: if you want to use a full blown Linux or Unix filesystem you will always have to fsync (or variants of it like msync), period. If you want a volume manager on stereoids that hands out large chunks of storage memory that can't ever be moved, truncated, shared, allocated on demand, etc - implement it in your library on top of a device file. -- 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