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 9CA3CC433EF for ; Sat, 8 Jan 2022 00:50:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232071AbiAHAuO (ORCPT ); Fri, 7 Jan 2022 19:50:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43364 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232014AbiAHAuN (ORCPT ); Fri, 7 Jan 2022 19:50:13 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA0BBC061574 for ; Fri, 7 Jan 2022 16:50:13 -0800 (PST) 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=eUv3q0GNQyMCM3aaZjusm8wlJcTIDvHI/q+X9aUjFH4=; b=SJgTCDMS8b3BwoNM4hS4iRhEL6 C4QZljs9ObpUUWkp3iHgx67sLYngrh4NtN8nAi80gaDvwVHnGauEPfTKl8QCm8B3lkiiBeVcAoBPa ErNs24afNWNFk/gXjJq2p8A0hDGG4KXYk1qJ1g+iZBNEB5RKcg5jJ4sXLkQ9SdxZhiM8BD1RqojiM EfyNxTc3zGD5+n0CDxYVhbVJ/KvX2nlqMtAMNMll4Vhw5qTftA6YiQKIrTweNaw3zt70Xi2h6/Utq i/WdtEmAWsbaXpOvJ8LT2xbrkLHr7hITtYVlEZx7aT9o+jqjBBNtCKuzmId2qlUfA6Q7+oHEPpVk6 nDz/kG4Q==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1n5zvd-000ItP-Vt; Sat, 08 Jan 2022 00:49:54 +0000 Date: Sat, 8 Jan 2022 00:49:53 +0000 From: Matthew Wilcox To: Andrew Morton Cc: Wei Yang , peterz@infradead.org, vbabka@suse.cz, will@kernel.org, linyunsheng@huawei.com, aarcange@redhat.com, feng.tang@intel.com, ebiederm@xmission.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: remove offset check on page->compound_head and folio->lru Message-ID: References: <20220106235254.19190-1-richard.weiyang@gmail.com> <20220107134059.flxr2hcd6ilb6vt7@master> <20220107160825.13c71fdd871d7d5611d116b9@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220107160825.13c71fdd871d7d5611d116b9@linux-foundation.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 07, 2022 at 04:08:25PM -0800, Andrew Morton wrote: > On Fri, 7 Jan 2022 22:11:20 +0000 Matthew Wilcox wrote: > > > On Fri, Jan 07, 2022 at 01:40:59PM +0000, Wei Yang wrote: > > > On Fri, Jan 07, 2022 at 03:59:01AM +0000, Matthew Wilcox wrote: > > > >On Thu, Jan 06, 2022 at 11:52:54PM +0000, Wei Yang wrote: > > > >> FOLIO_MATCH() is used to make sure struct page and folio has identical > > > >> layout for the first several words. > > > >> > > > >> The comparison of offset between page->compound_head and folio->lru is > > > >> more like an internal check in struct page. > > > >> > > > >> This patch just removes it. > > > >> > > > >> Signed-off-by: Wei Yang > > > > > > > >No. > > > > > > Hi, Matthew > > > > > > Would you mind sharing some insight on this check? > > > > It's right there in the comments. > > Well I can't figure out which comment you're referring to? * WARNING: bit 0 of the first word is used for PageTail(). That * means the other users of this union MUST NOT use the bit to * avoid collision and false-positive PageTail(). > > If you can't be bothered to read, why should I write? > > I don't think the punishment comes close to fitting the crime here :( I felt I had to NACk it as quickly as possible so you didn't apply it. Otherwise I'd've waited until I was back from holiday before replying to the earlier patch. But you applied that lickety-split, so clearly I'm not allowed to take a week off.