From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1EC15C28CF6 for ; Sat, 28 Jul 2018 07:25:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C70E320842 for ; Sat, 28 Jul 2018 07:25:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C70E320842 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727023AbeG1IvW (ORCPT ); Sat, 28 Jul 2018 04:51:22 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:37544 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726103AbeG1IvV (ORCPT ); Sat, 28 Jul 2018 04:51:21 -0400 Received: from localhost (D57D388D.static.ziggozakelijk.nl [213.125.56.141]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 018C83EE; Sat, 28 Jul 2018 07:25:50 +0000 (UTC) Date: Sat, 28 Jul 2018 09:25:48 +0200 From: Greg Kroah-Hartman To: Gao Xiang Cc: devel@driverdev.osuosl.org, hsiangkao@aol.com, linux-erofs@lists.ozlabs.org, yuchao0@huawei.com, linux-kernel@vger.kernel.org, weidu.du@huawei.com, linux-fsdevel@vger.kernel.org, miaoxie@huawei.com, chao@kernel.org Subject: Re: [PATCH 00/25] staging: erofs: introduce erofs file system Message-ID: <20180728072548.GA1500@kroah.com> References: <1527764767-22190-1-git-send-email-gaoxiang25@huawei.com> <1532607728-103372-1-git-send-email-gaoxiang25@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1532607728-103372-1-git-send-email-gaoxiang25@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 26, 2018 at 08:21:43PM +0800, Gao Xiang wrote: > Hi, > > This is actually the 2nd patchset of erofs file system, > the original patchset can be found at > > Link: https://marc.info/?l=linux-fsdevel&m=152776480425624 > > In order to keep up with the mainline linux-kernel changes and > improve it in a more active and timely manner, we put forword > this upstream proposal for linux-staging. > > EROFS file system is a read-only file system with compression > support designed for certain devices (especially embeded > devices) with very limited physical memory and lots of memory > consumers, such as Android devices. It aimes to provide > a complete compression solution for such devices focuing > on high performance and little extra memory overhead. > > It is perferred to select larger compressed cluster sizes > (generally >= 128k) for traditional compression file systems. > It reads and decompresses a large compressed cluster at once, > which has a good-looking random read number when memory > is sufficient because all historial decompressed data > is expected to be cached in memory. However, it also > induces destructive effects when such devices have no enough > spare memory for caching and decompression. > > EROFS file system acts in some different way. It uses > fixed-sized compressed size rather than fixed-sized input > size, namely VLE (variable-length extent) compression, > which has at least three adventages: > > 1) all data read from block device at once can be > utilized, and read amplification can be easier to > estimate and control; > 2) generally, it has a better compression ratio than > fixed-sized input compression approaches configured > with the same size; > 3) aggressively optimized paths such as partial page > read can be implemented to gain better performance > for page-unaligned read (unimplemented yet, in TODO list). > > As can be seen, VLE compression does a great job in small > compressed cluster sizes, which is of course suitable for > devices with limited memory. In this patchset, an in-place > decompresion is also introduced to minimize extra memory usage. > > > Apart from compression, EROFS also has the following features > available and some limits: > o page-sized block support (currently, and no buffer-head); > o 32-bit block address (16TB for 4KB block); > o selectable v1 (32 bytes) / v2 (64 bytes) inode; > o 32-bit / 64-bit file size; > o 64-bit node number for addressing inodes; > o 64-bit s and 32-bit ns timestamps; > o inline data support; > o inline and shared xattr support; > o metadata and data can be mixed (optional); > o special inode support; > o posix acl support. > > > The file system is still actively WIP, see _TODO_ for more details. > > Any comments are welcome. :) Thanks for submitting this, the filesystem looks very interesting. I've queued it all up now in the staging-next tree. greg k-h