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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0C27C04E69 for ; Thu, 3 Aug 2023 14:50:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235592AbjHCOt7 (ORCPT ); Thu, 3 Aug 2023 10:49:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234240AbjHCOt5 (ORCPT ); Thu, 3 Aug 2023 10:49:57 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 520CCA3 for ; Thu, 3 Aug 2023 07:49:56 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 0C2CC21900; Thu, 3 Aug 2023 14:49:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1691074195; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=zNsMn66aPrXCwyWEFx/U4iJZBEPN4KAvlDUuVw6PgmA=; b=cD3jGFizMcCBYzd8B77P+NaaETqeAT5vbTb6+VnG+9wkzOE8XyREcov67jyuR3ZGzMuKJA 1vcevKT2NTuV91JMXUty7jRqTGXmK+Nb98Xj9lzsjeGtV80kIwI/M5F2rbxOUfatt895kN rLTMdVvsGJSTU1wX/dWwh21LiKZWLlk= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id D827A1333C; Thu, 3 Aug 2023 14:49:54 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 8ovRMZK+y2QmHAAAMHmgww (envelope-from ); Thu, 03 Aug 2023 14:49:54 +0000 Date: Thu, 3 Aug 2023 16:49:54 +0200 From: Michal Hocko To: Tetsuo Handa Cc: Sebastian Andrzej Siewior , Petr Mladek , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Luis Claudio R. Goncalves" , Andrew Morton , Boqun Feng , Ingo Molnar , John Ogness , Mel Gorman , Peter Zijlstra , Thomas Gleixner , Waiman Long , Will Deacon Subject: Re: [PATCH v2 1/2] seqlock: Do the lockdep annotation before locking in do_write_seqcount_begin_nested() Message-ID: References: <20230623171232.892937-2-bigeasy@linutronix.de> <20230626081254.XmorFrhs@linutronix.de> <20230727151029.e_M9bi8N@linutronix.de> <649fa1a7-4efd-8cc7-92c7-ac7944adc283@I-love.SAKURA.ne.jp> <60d4dc52-9281-9266-4294-b514bd09e6e8@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <60d4dc52-9281-9266-4294-b514bd09e6e8@I-love.SAKURA.ne.jp> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 03-08-23 22:18:10, Tetsuo Handa wrote: > On 2023/07/31 23:25, Michal Hocko wrote: > > On Sat 29-07-23 20:05:43, Tetsuo Handa wrote: > >> On 2023/07/29 14:31, Tetsuo Handa wrote: > >>> On 2023/07/28 0:10, Sebastian Andrzej Siewior wrote: > >>>> On 2023-06-28 21:14:16 [+0900], Tetsuo Handa wrote: > >>>>>> Anyway, please do not do this change only because of printk(). > >>>>>> IMHO, the current ordering is more logical and the printk() problem > >>>>>> should be solved another way. > >>>>> > >>>>> Then, since [PATCH 1/2] cannot be applied, [PATCH 2/2] is automatically > >>>>> rejected. > >>>> > >>>> My understanding is that this patch gets applied and your objection will > >>>> be noted. > >>> > >>> My preference is that zonelist_update_seq is not checked by !__GFP_DIRECT_RECLAIM > >>> allocations, which is a low-hanging fruit towards GFP_LOCKLESS mentioned at > >>> https://lkml.kernel.org/r/ZG3+l4qcCWTPtSMD@dhcp22.suse.cz and > >>> https://lkml.kernel.org/r/ZJWWpGZMJIADQvRS@dhcp22.suse.cz . > >>> > >>> Maybe we can defer checking zonelist_update_seq till retry check like below, > >>> for this is really an infrequent event. > >>> > >> > >> An updated version with comments added. > > > > Seriously, don't you see how hairy all this is? And for what? Nitpicking > > something that doesn't seem to be a real problem in the first place? > > Seriously, can't you find "zonelist_update_seq is not checked by !__GFP_DIRECT_RECLAIM > allocations, which is a low-hanging fruit towards GFP_LOCKLESS" !? I do not think we have concluded that we want to support GFP_LOCKLESS. This might be trivial straightforward now but it imposes some constrains for future maintainability. So far we haven't heard about many usecases where this would be needed and a single one is not sufficient IMHO. -- Michal Hocko SUSE Labs