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, 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 2D7B4C3A59E for ; Mon, 2 Sep 2019 12:51:43 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (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 00A07216C8 for ; Mon, 2 Sep 2019 12:51:42 +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="p1wdTs4X" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 00A07216C8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=driverdev-devel-bounces@linuxdriverproject.org Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id CB83385FB6; Mon, 2 Sep 2019 12:51:42 +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 RKYqCAK4_1Hs; Mon, 2 Sep 2019 12:51:39 +0000 (UTC) Received: from ash.osuosl.org (ash.osuosl.org [140.211.166.34]) by fraxinus.osuosl.org (Postfix) with ESMTP id B711D85F0A; Mon, 2 Sep 2019 12:51:39 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by ash.osuosl.org (Postfix) with ESMTP id 489901BF359 for ; Mon, 2 Sep 2019 12:51:38 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 45C06822E0 for ; Mon, 2 Sep 2019 12:51:38 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 44yY17VFbW0h for ; Mon, 2 Sep 2019 12:51:37 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by hemlock.osuosl.org (Postfix) with ESMTPS id 0F65C87DD4 for ; Mon, 2 Sep 2019 12:51:16 +0000 (UTC) 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=2SRLGmzt9ygJ+k1758a7WeMkOp6QVS9SpfevL0fmQfQ=; b=p1wdTs4XDK/LQWfm/yELbp49u phV0PdWujXYthfryE4TkwNYPNSjVRtyhrjikDgf3P3SMQVhM4XRwApkyG5tQzhuUZhc9Bz3ebmUh7 qJ3KM1c0uT+TU9dK8YwGrjAmSVzRQYI1dlCZedOFGQzdvco5MqhqYrS1C6rDLvn7gNyBDqmIo/xKW G8ajsycXwdssNAKgMAPBfcubUQjWvXjRoblHim8dRKXzpDUS1z/aSV/OxkTDhuv2tYkihbFEL8+Ig Joaenckr004Pz8x2NJ1XiFbwZSkzUEc91fCcuCSy47u20XG+/CKVdTloaqFrnExpE814on13j+pV8 EmKp8xVSg==; Received: from hch by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1i4lnZ-0004LV-VP; Mon, 02 Sep 2019 12:51:09 +0000 Date: Mon, 2 Sep 2019 05:51:09 -0700 From: Christoph Hellwig To: Gao Xiang Subject: Re: [PATCH v6 03/24] erofs: add super block operations Message-ID: <20190902125109.GA9826@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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190901085452.GA4663@hsiangkao-HP-ZHAN-66-Pro-G1> 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 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" , Christoph Hellwig , Chao Yu , linux-erofs@lists.ozlabs.org, Alexander Viro , Jaegeuk Kim , Theodore Ts'o , Pavel Machek , LKML , Li Guifu , Fang Wei , Greg Kroah-Hartman , linux-fsdevel@vger.kernel.org, Andrew Morton , Linus Torvalds Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" 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? > > > + 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. > > > + 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? > 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. _______________________________________________ devel mailing list devel@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel