From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-la0-f42.google.com (mail-la0-f42.google.com [209.85.215.42]) by kanga.kvack.org (Postfix) with ESMTP id E58576B0035 for ; Wed, 27 Aug 2014 19:04:55 -0400 (EDT) Received: by mail-la0-f42.google.com with SMTP id mc6so207841lab.1 for ; Wed, 27 Aug 2014 16:04:54 -0700 (PDT) Received: from lxorguk.ukuu.org.uk (7.3.c.8.2.a.e.f.f.f.8.1.0.3.2.0.9.6.0.7.2.3.f.b.0.b.8.0.1.0.0.2.ip6.arpa. [2001:8b0:bf32:7069:230:18ff:fea2:8c37]) by mx.google.com with ESMTPS id mq2si2833256lbb.9.2014.08.27.16.04.53 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Aug 2014 16:04:53 -0700 (PDT) Date: Thu, 28 Aug 2014 00:04:40 +0100 From: One Thousand Gnomes Subject: Re: [PATCH v10 00/21] Support ext4 on NV-DIMMs Message-ID: <20140828000440.5d9f5bff@alan.etchedpixels.co.uk> In-Reply-To: <20140827143055.5210c5fb9696e460b456eb26@linux-foundation.org> References: <20140827130613.c8f6790093d279a447196f17@linux-foundation.org> <20140827143055.5210c5fb9696e460b456eb26@linux-foundation.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: Andrew Morton Cc: Christoph Lameter , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, willy@linux.intel.com On Wed, 27 Aug 2014 14:30:55 -0700 Andrew Morton wrote: > On Wed, 27 Aug 2014 16:22:20 -0500 (CDT) Christoph Lameter wrote: > > > > Some explanation of why one would use ext4 instead of, say, > > > suitably-modified ramfs/tmpfs/rd/etc? > > > > The NVDIMM contents survive reboot and therefore ramfs and friends wont > > work with it. > > See "suitably modified". Presumably this type of memory would need to > come from a particular page allocator zone. ramfs would be unweildy > due to its use to dentry/inode caches, but rd/etc should be feasible. If you took one of the existing ramfs types you would then need to - make it persistent in its storage, and put all the objects in the store - add journalling for failures mid transaction. Your dimm may retain its bits but if your CPU reset mid fs operation its got to be recovered - write an fsck tool for it - validate it at which point it's probably turned into ext4 8) It's persistent but that doesn't solve the 'my box crashed' problem. Alan -- 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