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_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 721BCC3A59E for ; Mon, 2 Sep 2019 14:44:42 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4B02821670 for ; Mon, 2 Sep 2019 14:44:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4B02821670 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=driverdev-devel-bounces@linuxdriverproject.org Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 1E8128669A; Mon, 2 Sep 2019 14:44:42 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OGWlS2FXgcyG; Mon, 2 Sep 2019 14:44:39 +0000 (UTC) Received: from ash.osuosl.org (ash.osuosl.org [140.211.166.34]) by whitealder.osuosl.org (Postfix) with ESMTP id 50E9086566; Mon, 2 Sep 2019 14:44:39 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by ash.osuosl.org (Postfix) with ESMTP id 469F21BF86D for ; Mon, 2 Sep 2019 14:44:38 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 42C5C84FC9 for ; Mon, 2 Sep 2019 14:44:38 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id b0UWtAHMqB5y for ; Mon, 2 Sep 2019 14:44:37 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from huawei.com (szxga01-in.huawei.com [45.249.212.187]) by fraxinus.osuosl.org (Postfix) with ESMTPS id 1726384E74 for ; Mon, 2 Sep 2019 14:44:36 +0000 (UTC) Received: from DGGEMM406-HUB.china.huawei.com (unknown [172.30.72.53]) by Forcepoint Email with ESMTP id 58F3A420F300ACFA4260; Mon, 2 Sep 2019 22:43:56 +0800 (CST) Received: from dggeme762-chm.china.huawei.com (10.3.19.108) by DGGEMM406-HUB.china.huawei.com (10.3.20.214) with Microsoft SMTP Server (TLS) id 14.3.439.0; Mon, 2 Sep 2019 22:43:55 +0800 Received: from architecture4 (10.140.130.215) by dggeme762-chm.china.huawei.com (10.3.19.108) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1591.10; Mon, 2 Sep 2019 22:43:55 +0800 Date: Mon, 2 Sep 2019 22:43:04 +0800 From: Gao Xiang To: Christoph Hellwig Subject: Re: [PATCH v6 03/24] erofs: add super block operations Message-ID: <20190902144303.GF2664@architecture4> 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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190902125109.GA9826@infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-Originating-IP: [10.140.130.215] X-ClientProxiedBy: dggeme706-chm.china.huawei.com (10.1.199.102) To dggeme762-chm.china.huawei.com (10.3.19.108) X-CFilter-Loop: Reflected X-BeenThere: driverdev-devel@linuxdriverproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Driver Project Developer List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jan Kara , Amir Goldstein , Dave Chinner , David Sterba , Miao Xie , devel@driverdev.osuosl.org, Stephen Rothwell , "Darrick J . Wong" , Chao Yu , Alexander Viro , Jaegeuk Kim , Theodore Ts'o , Pavel Machek , Linus Torvalds , LKML , Li Guifu , Fang Wei , Greg Kroah-Hartman , linux-fsdevel@vger.kernel.org, Andrew Morton , linux-erofs@lists.ozlabs.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" Hi Christoph, On Mon, Sep 02, 2019 at 05:51:09AM -0700, Christoph Hellwig wrote: > On Sun, Sep 01, 2019 at 04:54:55PM +0800, Gao Xiang wrote: > > No modification at this... (some comments already right here...) > > > 20 /* 128-byte erofs on-disk super block */ > > 21 struct erofs_super_block { > > ... > > 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...) > > > > > + bh = sb_bread(sb, 0); > > > > > > Is there any good reasons to use buffer heads like this in new code > > > vs directly using bios? > > > > As you said, I want it in the page cache. > > > > The reason "why not use read_mapping_page or similar?" is simply > > read_mapping_page -> .readpage -> (for bdev inode) block_read_full_page > > -> create_page_buffers anyway... > > > > sb_bread haven't obsoleted... It has similar function though... > > With the different that it keeps you isolated from the buffer_head > internals. This seems to be your only direct use of buffer heads, > which while not deprecated are a bit of an ugly step child. So if > you can easily avoid creating a buffer_head dependency in a new > filesystem I think you should avoid it. OK, let's use read_mapping_page instead. > > > > > + sbi->build_time = le64_to_cpu(layout->build_time); > > > > + sbi->build_time_nsec = le32_to_cpu(layout->build_time_nsec); > > > > + > > > > + 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...) > > > The background is Al's comments in erofs v2.... > > (which simplify erofs_fill_super logic) > > https://lore.kernel.org/r/20190720224955.GD17978@ZenIV.linux.org.uk/ > > > > with a specific notation... > > https://lore.kernel.org/r/20190721040547.GF17978@ZenIV.linux.org.uk/ > > > > " > > > OTOH, for the case of NULL ->s_root ->put_super() won't be called > > > at all, so in that case you need it directly in ->kill_sb(). > > " > > Yes. Although none of that is relevant for this initial version, > just after more features are added. This patch uses it actually... since no failure path in erofs_fill_super() and s_root will be filled nearly at the end of the function... Thanks, Gao Xiang _______________________________________________ devel mailing list devel@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel