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 5CF1BC3A589 for ; Tue, 20 Aug 2019 11:08:40 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 14C8022CF7 for ; Tue, 20 Aug 2019 11:08:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 14C8022CF7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46CShj5Zx7zDqTs for ; Tue, 20 Aug 2019 21:08:37 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=suse.cz (client-ip=195.135.220.15; helo=mx1.suse.de; envelope-from=vbabka@suse.cz; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=suse.cz Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 46CSfN6yH0zDqjh for ; Tue, 20 Aug 2019 21:06:29 +1000 (AEST) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id CD029AE9A; Tue, 20 Aug 2019 11:06:25 +0000 (UTC) Subject: Re: [PATCH] btrfs: fix allocation of bitmap pages. To: Christoph Hellwig , dsterba@suse.cz, Christophe Leroy , erhard_f@mailbox.org, Chris Mason , Josef Bacik , David Sterba , Andrew Morton , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org References: <20190817074439.84C6C1056A3@localhost.localdomain> <20190819174600.GN24086@twin.jikos.cz> <20190820023031.GC9594@infradead.org> From: Vlastimil Babka Message-ID: <6f99b73c-db8f-8135-b827-0a135734d7da@suse.cz> Date: Tue, 20 Aug 2019 13:06:25 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190820023031.GC9594@infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 8/20/19 4:30 AM, Christoph Hellwig wrote: > On Mon, Aug 19, 2019 at 07:46:00PM +0200, David Sterba wrote: >> Another thing that is lost is the slub debugging support for all >> architectures, because get_zeroed_pages lacking the red zones and sanity >> checks. >> >> I find working with raw pages in this code a bit inconsistent with the >> rest of btrfs code, but that's rather minor compared to the above. >> >> Summing it up, I think that the proper fix should go to copy_page >> implementation on architectures that require it or make it clear what >> are the copy_page constraints. > > The whole point of copy_page is to copy exactly one page and it makes > sense to assume that is aligned. A sane memcpy would use the same > underlying primitives as well after checking they fit. So I think the > prime issue here is btrfs' use of copy_page instead of memcpy. The > secondary issue is slub fucking up alignments for no good reason. We > just got bitten by that crap again in XFS as well :( Meh, I should finally get back to https://lwn.net/Articles/787740/ right