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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, 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 679C8C433FE for ; Wed, 9 Dec 2020 01:34:34 +0000 (UTC) Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (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 E99342389E; Wed, 9 Dec 2020 01:34:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E99342389E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-f2fs-devel-bounces@lists.sourceforge.net Received: from [127.0.0.1] (helo=sfs-ml-2.v29.lw.sourceforge.com) by sfs-ml-2.v29.lw.sourceforge.com with esmtp (Exim 4.90_1) (envelope-from ) id 1kmoNE-0004H4-M9; Wed, 09 Dec 2020 01:34:32 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kmoND-0004Gx-HA for linux-f2fs-devel@lists.sourceforge.net; Wed, 09 Dec 2020 01:34:31 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:CC:To:Subject:Sender:Reply-To: 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=BNzy3mPSEsWf2padmVwfMzST40N8of74D5wBwR4sa9I=; b=aqB4xr8G86t5yyC7eNG1RjwSsv WX7Ns5LIXGrpWHUYmcH+9I4Nf8ugIxE/GuA8dKIEQrmQSQ02sxU9O6Wrg4FGe8tCfUbbjSQwuBP0H dz8VBlzqTM2yvSAa3Bsq1F3JcHUOYyUVH/eGZFi4SqsaGhcd1xeEPA/j68quZz6CRK2s=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:MIME-Version:Date: Message-ID:From:References:CC:To:Subject:Sender:Reply-To: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=BNzy3mPSEsWf2padmVwfMzST40N8of74D5wBwR4sa9I=; b=mLJJ0IfXScGoCBsWfmQvPgFacO r3bZ2hbiuQl6V7HHycmo6pH9kj72anmnX1nyW9tdQ3mVU0ybs9EJezDzHBpc99IpCx5M3zP8xFAsy p9P8yrz/eWwDVq0lbLCQQGQME1ygdQJN03xvtlBZO0Gxt4xaPwXAqDpzFIyPe1WikrJU=; Received: from szxga05-in.huawei.com ([45.249.212.191]) by sfi-mx-1.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.2) id 1kmoMz-004J1D-50 for linux-f2fs-devel@lists.sourceforge.net; Wed, 09 Dec 2020 01:34:31 +0000 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4CrKLx3kDKzM22W; Wed, 9 Dec 2020 09:33:29 +0800 (CST) Received: from [10.136.114.67] (10.136.114.67) by smtp.huawei.com (10.3.19.202) with Microsoft SMTP Server (TLS) id 14.3.487.0; Wed, 9 Dec 2020 09:34:07 +0800 To: Jaegeuk Kim , Eric Biggers References: <20201205042626.1113600-1-daeho43@gmail.com> From: Chao Yu Message-ID: <55db08c3-6b3f-a78b-c40d-7f61cd7693b7@huawei.com> Date: Wed, 9 Dec 2020 09:34:06 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Originating-IP: [10.136.114.67] X-CFilter-Loop: Reflected X-Headers-End: 1kmoMz-004J1D-50 Subject: Re: [f2fs-dev] [PATCH v3] f2fs: fix race of pending_pages in decompression X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com, Daeho Jeong , linux-kernel@vger.kernel.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2020/12/9 7:55, Jaegeuk Kim wrote: > On 12/07, Eric Biggers wrote: >> On Tue, Dec 08, 2020 at 08:51:45AM +0900, Daeho Jeong wrote: >>>> I am trying to review this but it is very hard, as the f2fs compression code is >>>> very hard to understand. >>>> >>>> It looks like a 'struct decompress_io_ctx' represents the work to decompress a >>>> particular cluster. Since the compressed data of the cluster can be read using >>>> multiple bios, there is a reference count of how many pages are remaining to be >>>> read before all the cluster's pages have been read and decompression can start. >>>> >>>> What I don't understand is why that reference counting needs to work differently >>>> depending on whether verity is enabled or not. Shouldn't it be exactly the >>>> same? >>>> >>>> There also seems to be some confusion about the scope of STEP_VERITY. Before >>>> f2fs compression was added, it was a per-bio thing. But now in a compressed >>>> file, it's really a per-cluster thing, since all decompressed pages in a >>>> compressed cluster are verified (or not verified) at once. >>>> >>>> Wouldn't it make a lot more sense to, when a cluster needs both compression and >>>> verity, *not* set STEP_VERITY on the bios, but rather set a similar flag in the >>>> decompress_io_ctx? >>>> >>> >>> Eric, >>> >>> Decompression and verity can be executed in different thread contexts >>> in different timing, so we need separate counts for each. >>> >>> We already use STEP_VERITY for non-compression case, so I think using >>> this flag in here looks more making sense. >>> >>> Thanks, >> >> That didn't really answer my questions. >> >> I gave up trying to review this patch as the compression post-read handling is >> just way too weird and hard to understand. I wrote a patch to clean it all up >> instead, please take a look: >> https://lkml.kernel.org/r/20201208060328.2237091-1-ebiggers@kernel.org > > Eric, > I also tried to review your patch, but it's quite hard to follow quickly and Me too, it needs more time to check whether the cleanup doesn't miss any cases. Thanks, > requires stress tests for a while. Given upcoming merge window and urgency of > the bug, let me apply Daeho's fix first. By any chance, may I ask revisiting > your clean-up on top of the fix in the next cycle? > > Thanks, > >> >> - Eric > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > . > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel