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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 54D28C433FE for ; Tue, 8 Dec 2020 23:55:39 +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 E937823A6A; Tue, 8 Dec 2020 23:55:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E937823A6A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 1kmmpW-0008QW-BW; Tue, 08 Dec 2020 23:55:38 +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 1kmmpV-0008QP-Hx for linux-f2fs-devel@lists.sourceforge.net; Tue, 08 Dec 2020 23:55:37 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; 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=HjuLsRWiAcdECFRpMhcQgdKb8zX0P1YPLgXhIIIEsDA=; b=Qv0lMod98oPLtZKWycj1dzcDbK eP8PccBrYKGLPGvW+MK29clNx88XHzZiEKxftOt6BE7hFXNc242s/u+PfQAgJnc7gZOd08yLMIaMm J+W0nBUkbcUs+1lmyREV25PDbR5dlRNvTwlmk96u87vGVjP+YWaB0VX4RhrKDqn04hRU=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; 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=HjuLsRWiAcdECFRpMhcQgdKb8zX0P1YPLgXhIIIEsDA=; b=FW05gH8KWwjbItDcSUxKUTfHQF hzRmBvErUFaxk4jprtPmNREKZpVlsqb5sRsf+UHDy9GLzoKXLEkZ+Ni6RkBDYmCTb7z5oqxC9uP1Y A4Wm6mpxTokMm0oJqruAG62mKsEssJFkT5XsIzL47pyHRC39R/nlTM84HpqcwU7PInPQ=; Received: from mail.kernel.org ([198.145.29.99]) by sfi-mx-1.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.2) id 1kmmpI-004DM0-Rc for linux-f2fs-devel@lists.sourceforge.net; Tue, 08 Dec 2020 23:55:37 +0000 Date: Tue, 8 Dec 2020 15:55:17 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1607471719; bh=XYsYf5906N+mg1XwuCiho6GHsJNm2dGoMhfW56SAY8I=; h=From:To:Cc:Subject:References:In-Reply-To:From; b=mqapjCiUDt5ExNEpAupAg/ZpeOom3Aiu7KhulRwdafuvSQLKj7jGFe021y5kDSJbE eD56i7mcQqPLrFOOogLc85rv0+qh/tK3UIFH7S5CpShj6662STqFqVaiJBZy3ZgsQs c4npFfZMdBuvUDyDvGVUCHPl09N8HKv0nZFC+tvAckYBGUPXR+7MrE7dc//B+f11hh Jskw6sHp2Wr8QVY9IkC8I/kHs+mTWB8yf1rjYPBqQJKGqYN5bxkeR3kTA1AWs7z1wl /U3oklwBMSR6/x2H9f8vheTeBvL9kQ1UHWIx0y1r6Znmlx9zs7n1UAnCKs80zD570U Ns9oNGcDgMIwA== From: Jaegeuk Kim To: Eric Biggers Message-ID: References: <20201205042626.1113600-1-daeho43@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Headers-End: 1kmmpI-004DM0-Rc 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: Daeho Jeong , kernel-team@android.com, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net 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 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