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=-18.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 13701C47082 for ; Sat, 5 Jun 2021 06:40:34 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 96AB36135D for ; Sat, 5 Jun 2021 06:40:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96AB36135D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 20A726B0036; Sat, 5 Jun 2021 02:40:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1BA8B6B006C; Sat, 5 Jun 2021 02:40:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 034286B006E; Sat, 5 Jun 2021 02:40:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0090.hostedemail.com [216.40.44.90]) by kanga.kvack.org (Postfix) with ESMTP id C35E96B0036 for ; Sat, 5 Jun 2021 02:40:32 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 6E460180AD801 for ; Sat, 5 Jun 2021 06:40:32 +0000 (UTC) X-FDA: 78218721504.10.2F0C205 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by imf24.hostedemail.com (Postfix) with ESMTP id 8B2F7A0049E8 for ; Sat, 5 Jun 2021 06:40:25 +0000 (UTC) Received: from mail-pj1-f44.google.com (mail-pj1-f44.google.com [209.85.216.44]) by linux.microsoft.com (Postfix) with ESMTPSA id 266B320B8013 for ; Fri, 4 Jun 2021 16:00:27 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 266B320B8013 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1622847627; bh=ds51mNDX2G6dtPwMYtC2iH66YJ5n86Y8klWdH2tkMc4=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=XYz4/W3rhZgn0WtZvdgmMaHRaVqzVwn6IVh4JyObNKuXoGULCr+DeklBdqctv+WLH +YDlKAaqSzKxHoPZRsN/5LrGxCvti2+suGbHEIJaEcMQRlPxlo4mWI1E3Ub2Bvhlue CimDnobsP6ICm7HD6L+rLXcj1agw6pW2LknrZfq0= Received: by mail-pj1-f44.google.com with SMTP id ei4so6332582pjb.3 for ; Fri, 04 Jun 2021 16:00:27 -0700 (PDT) X-Gm-Message-State: AOAM531TGkV7MqCUkOXilJBFCMpICXoZHPsTXiyGOqU6us4e8ZGY+ogO wDzZfEGvDe0ImTAnMDrwoKk8mYf8YX8Axpe3zl4= X-Google-Smtp-Source: ABdhPJwV60Zzvd7d6fYgOL0a7JwYyjAs1nlvuHWpkTkjNBPxUYcdJFR2UE+iVPVhb+MZfruC6CI6og/E3m0vnuc7kAY= X-Received: by 2002:a17:902:ee06:b029:10b:baee:6593 with SMTP id z6-20020a170902ee06b029010bbaee6593mr6640758plb.33.1622847626662; Fri, 04 Jun 2021 16:00:26 -0700 (PDT) MIME-Version: 1.0 References: <20210604183349.30040-1-mcroce@linux.microsoft.com> <20210604183349.30040-2-mcroce@linux.microsoft.com> In-Reply-To: From: Matteo Croce Date: Sat, 5 Jun 2021 00:59:50 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH net-next v7 1/5] mm: add a signature in struct page To: Matthew Wilcox Cc: netdev@vger.kernel.org, linux-mm@kvack.org, Ayush Sawal , Vinay Kumar Yadav , Rohit Maheshwari , "David S. Miller" , Jakub Kicinski , Thomas Petazzoni , Marcin Wojtas , Russell King , Mirko Lindner , Stephen Hemminger , Tariq Toukan , Jesper Dangaard Brouer , Ilias Apalodimas , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Boris Pismenny , Arnd Bergmann , Andrew Morton , "Peter Zijlstra (Intel)" , Vlastimil Babka , Yu Zhao , Will Deacon , Fenghua Yu , Roman Gushchin , Hugh Dickins , Peter Xu , Jason Gunthorpe , Jonathan Lemon , Alexander Lobakin , Cong Wang , wenxu , Kevin Hao , Jakub Sitnicki , Marco Elver , Willem de Bruijn , Miaohe Lin , Yunsheng Lin , Guillaume Nault , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, Eric Dumazet , David Ahern , Lorenzo Bianconi , Saeed Mahameed , Andrew Lunn , Paolo Abeni , Sven Auhagen Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux.microsoft.com header.s=default header.b="XYz4/W3r"; spf=pass (imf24.hostedemail.com: domain of mcroce@linux.microsoft.com designates 13.77.154.182 as permitted sender) smtp.mailfrom=mcroce@linux.microsoft.com; dmarc=pass (policy=none) header.from=linux.microsoft.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 8B2F7A0049E8 X-Stat-Signature: k6uodzu1tkqmrwgw7bkno1mqj1jr8x5d X-HE-Tag: 1622875225-700446 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 Fri, Jun 4, 2021 at 9:08 PM Matthew Wilcox wrote: > > On Fri, Jun 04, 2021 at 08:33:45PM +0200, Matteo Croce wrote: > > @@ -130,7 +137,10 @@ struct page { > > }; > > }; > > struct { /* Tail pages of compound page */ > > - unsigned long compound_head; /* Bit zero is set */ > > + /* Bit zero is set > > + * Bit one if pfmemalloc page > > + */ > > + unsigned long compound_head; > > I would drop this hunk. Bit 1 is not used for this purpose in tail > pages; it's used for that purpose in head and base pages. > > I suppose we could do something like ... > > static inline void set_page_pfmemalloc(struct page *page) > { > - page->index = -1UL; > + page->lru.next = (void *)2; > } > > if it's causing confusion. > If you prefer, ok for me. Why not "(void *)BIT(1)"? Just to remark that it's a single bit and not a magic like value? -- per aspera ad upstream