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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,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 41D3AC07E99 for ; Mon, 5 Jul 2021 11:48:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E562B613FC for ; Mon, 5 Jul 2021 11:48:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E562B613FC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8EB336B0036; Mon, 5 Jul 2021 07:48:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 89B916B005D; Mon, 5 Jul 2021 07:48:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 73C646B006C; Mon, 5 Jul 2021 07:48:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0075.hostedemail.com [216.40.44.75]) by kanga.kvack.org (Postfix) with ESMTP id 496CD6B0036 for ; Mon, 5 Jul 2021 07:48:13 -0400 (EDT) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id BB1CA1F358 for ; Mon, 5 Jul 2021 11:48:12 +0000 (UTC) X-FDA: 78328360824.09.91F7CF9 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf29.hostedemail.com (Postfix) with ESMTP id 4B7049000250 for ; Mon, 5 Jul 2021 11:48:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=EwWN7+UAKQIxLsDpSIp+JET9XMdfQgDUShXvpWDBlhk=; b=eAwDlJOBU+Tx+dEU6uv0PcpZ5Z RasJ+GroFUsGWxd2fKjoXsLzNuziTWVLUWfQutkeScELYfij7yZ7HJykLLat5dLYOcHcAvrHwDQwU W1CdwKpLbG4hh5TtyOOLcasY8ml+FqSPjWqH8XaH8/hkTt4v96+Ef5IeS+AurC8CDoczbLR9f7ubh mGx5mtZ7RbC++4TlVSaPOwifGtDvKqJWcQiiQ3oAFxNyUYBX1J/INz+UfIMpO79Tcc67eKXlrKkG5 cphdgL9rx/FDAFW4Z26AGNEqDbHAU/OgDLaArnEVfPfpK10O4WOojU0P9+IYI6yTwpEfBFK+ogBhX +itC8tLQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1m0N4m-00AD6s-JQ; Mon, 05 Jul 2021 11:47:50 +0000 Date: Mon, 5 Jul 2021 12:47:48 +0100 From: Matthew Wilcox To: Chao Yu Cc: Jaegeuk Kim , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org Subject: Re: [f2fs-dev] [PATCH] f2fs: initialize page->private when using for our internal use Message-ID: References: <20210705052216.831989-1-jaegeuk@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=eAwDlJOB; dmarc=none; spf=none (imf29.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Stat-Signature: q35q4twjn3gi16mjffbtaf5q46d3piij X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 4B7049000250 X-HE-Tag: 1625485692-627517 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 05, 2021 at 07:33:35PM +0800, Chao Yu wrote: > On 2021/7/5 16:56, Jaegeuk Kim wrote: > > On 07/05, Chao Yu wrote: > > > On 2021/7/5 13:22, Jaegeuk Kim wrote: > > > > We need to guarantee it's initially zero. Otherwise, it'll hurt entire flag > > > > operations. > > > > > > Oops, I didn't get the point, shouldn't .private be zero after page was > > > just allocated by filesystem? What's the case we will encounter stall > > > private data left in page? > > > > I'm seeing f2fs_migrate_page() has the newpage with some value without Private > > flag. That causes a kernel panic later due to wrong private flag used in f2fs. > > I'm not familiar with that part of codes, so Cc mm mailing list for help. > > My question is newpage in .migrate_page() may contain non-zero value in .private > field but w/o setting PagePrivate flag, is it a normal case? I think freshly allocated pages have a page->private of 0. ie this code in mm/page_alloc.c: page = rmqueue(ac->preferred_zoneref->zone, zone, order, gfp_mask, alloc_flags, ac->migratetype); if (page) { prep_new_page(page, order, gfp_mask, alloc_flags); where prep_new_page() calls post_alloc_hook() which contains: set_page_private(page, 0); Now, I do see in __buffer_migrate_page() (mm/migrate.c): attach_page_private(newpage, detach_page_private(page)); but as far as I can tell, f2fs doesn't call any of the buffer_migrate_page() paths. So I'm not sure why you're seeing a non-zero page->private.