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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 3348BC3A59E for ; Mon, 2 Sep 2019 15:19:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 080C6217D7 for ; Mon, 2 Sep 2019 15:19:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="hg55rG0H" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731962AbfIBPTR (ORCPT ); Mon, 2 Sep 2019 11:19:17 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:44270 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729971AbfIBPTQ (ORCPT ); Mon, 2 Sep 2019 11:19:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=2EGoFqF4zos5OWv6WNlwPBiBbR4EbKkewLh/Q5wrwzg=; b=hg55rG0HzZ77yWw3lDcHMwEJH 4h8tXaA10F6hxvy5EoMJeMlsFgva45iKJC3AS9g/Ap2If6wlb+9lOoQjF6RautWXs7fuH2KbLPGpN TokyPVRzEED9kDfKmX0u4MhmhuRBVRYt+Z3SxO5dLwR2lBE5cfOK80/paYacTHWmSW0sdGT1Na+S7 7aF0pm3wH2AIQejEdf+A1hMOAsn/lirsJZGtZPGXN77GBmAO/1wDvwfOk84jnwhxPVK1KEgzMy3sG 1aboGacoWyhc+tMzP691PSZ/lxTmBIA7WJAdPZghGGSWUKZNLU67+qXiJdEu+WBVcVmXLOES8qJf1 UBT+u7T5g==; Received: from hch by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1i4o6o-0004hD-LX; Mon, 02 Sep 2019 15:19:10 +0000 Date: Mon, 2 Sep 2019 08:19:10 -0700 From: Christoph Hellwig To: Gao Xiang Cc: Christoph Hellwig , Gao Xiang , Jan Kara , Chao Yu , Dave Chinner , LKML , Miao Xie , devel@driverdev.osuosl.org, Stephen Rothwell , "Darrick J . Wong" , Linus Torvalds , Amir Goldstein , Alexander Viro , Jaegeuk Kim , Theodore Ts'o , Pavel Machek , David Sterba , Li Guifu , Fang Wei , Greg Kroah-Hartman , linux-fsdevel@vger.kernel.org, Andrew Morton , linux-erofs@lists.ozlabs.org Subject: Re: [PATCH v6 03/24] erofs: add super block operations Message-ID: <20190902151910.GA14009@infradead.org> References: <20190802125347.166018-1-gaoxiang25@huawei.com> <20190802125347.166018-4-gaoxiang25@huawei.com> <20190829101545.GC20598@infradead.org> <20190901085452.GA4663@hsiangkao-HP-ZHAN-66-Pro-G1> <20190902125109.GA9826@infradead.org> <20190902144303.GF2664@architecture4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190902144303.GF2664@architecture4> User-Agent: Mutt/1.11.4 (2019-03-13) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 02, 2019 at 10:43:04PM +0800, Gao Xiang wrote: > Hi Christoph, > > > ... > > > 24 __le32 features; /* (aka. feature_compat) */ > > > ... > > > 38 __le32 requirements; /* (aka. feature_incompat) */ > > > ... > > > 41 }; > > > > This is only cosmetic, why not stick to feature_compat and > > feature_incompat? > > Okay, will fix. (however, in my mind, I'm some confused why > "features" could be incompatible...) The feature is incompatible if it requires changes to the driver. An easy to understand historic example is that ext3 originally did not have the file types in the directory entry. Adding them means old file system drivers can not read a file system with this new feature, so an incompat flag has to be added. > > > > > + memcpy(&sb->s_uuid, layout->uuid, sizeof(layout->uuid)); > > > > > + memcpy(sbi->volume_name, layout->volume_name, > > > > > + sizeof(layout->volume_name)); > > > > > > > > s_uuid should preferably be a uuid_t (assuming it is a real BE uuid, > > > > if it is le it should be a guid_t). > > > > > > For this case, I have no idea how to deal with... > > > I have little knowledge about this uuid stuff, so I just copied > > > from f2fs... (Could be no urgent of this field...) > > > > Who fills out this field in the on-disk format and how? > > mkfs.erofs, but this field leaves 0 for now. Is that reasonable? > (using libuuid can generate it easily...) If the filed is always zero for now please don't fill it out. If you decide it is worth adding the uuid eventually please add a compat feature flag that you have a valid uuid and only fill out the field if the file system actualy has a valid uuid.