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 6F360C6FA89 for ; Thu, 15 Sep 2022 16:36:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229994AbiIOQgo (ORCPT ); Thu, 15 Sep 2022 12:36:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229912AbiIOQgk (ORCPT ); Thu, 15 Sep 2022 12:36:40 -0400 Received: from mail-pj1-x1035.google.com (mail-pj1-x1035.google.com [IPv6:2607:f8b0:4864:20::1035]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2BBB51E3F2 for ; Thu, 15 Sep 2022 09:36:39 -0700 (PDT) Received: by mail-pj1-x1035.google.com with SMTP id ge9so6799357pjb.1 for ; Thu, 15 Sep 2022 09:36:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date; bh=Bya1RG0oExfDfV/RNQQVlFWpnUEDKrN8oNZxHjwTDWM=; b=beMcfXIgIlQ37Rw00Boy9/emgcBbDamWMbRxCl6vQwVF0XXcB5L0cw7kKtX7qCraMj c8TO/bh+ipD3jyw4NGCIWnhWF0xoRNEZimvheMXhG3JJ+zfghwoleA+L81iELNWvsmuH KzATbijxHtv6P4RamBBQNK6u/DHmmeqNQRSAZU0KLC5AttJnHnHzW+rzeAmdBx+whNHT WjG4QvVJ5McStg4N4yF1eonJ1R4MutHUa+NEALtd86CzubUEMG5tZlWXeYfDQZKmfy18 Rpm9GwdkSs+z75Wr/Cd69CweuoIo9XOQA5rRuh8VwAr5G1UTQAxdPG3ZjXam6dfGdIzn fmKQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date; bh=Bya1RG0oExfDfV/RNQQVlFWpnUEDKrN8oNZxHjwTDWM=; b=VWQf96LWvopFnThuwv1adGVJzd0ohFM0Zi5DrXI/5jhiNx4a+GZN7cx7hvFOLM3oSR auQoEBm63TZTa3dlX/iykhxBO0i+Hn0v7jLxzIczbeZzXVoGt0CtTy31z/++qkzxpRKx mKtemC3BdPV4nAAxZjn+fgw0nmH80S6wYa+yznxwfufwR/yVDCUaNCAWQLJqNqiGNNoH 1esFQ8DBDBWYN0K3JMEowWjAppimNyA+HEEsfMGMMHs1bVw0SNCEUU/6X87nT17hzD9Q HFYJG12JFCxbjKS3pSrjHTp8SafXClnooxNRKp3DzENKzWaOq/vyUjlKkP+/SnGMV99z dCBg== X-Gm-Message-State: ACgBeo3Te4K7p+M0KegidCinyCdIcJAS9Mn6PgPF2Y1U+CJgze0x8o9F UZfsey3yWHTHOYrH2JHY1Zk= X-Google-Smtp-Source: AA6agR6BXHicLXK2Y8HcyH/GmEIUiIV5gJvZtxMO9SPzo8ZFrbBT3kK77GuwTTwIlCxsmJkPVfiCRQ== X-Received: by 2002:a17:90a:5783:b0:200:4aa8:a18d with SMTP id g3-20020a17090a578300b002004aa8a18dmr11735159pji.38.1663259798570; Thu, 15 Sep 2022 09:36:38 -0700 (PDT) Received: from google.com (132.197.125.34.bc.googleusercontent.com. [34.125.197.132]) by smtp.gmail.com with ESMTPSA id b37-20020a631b65000000b00434651f9a96sm11611043pgm.15.2022.09.15.09.36.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Sep 2022 09:36:38 -0700 (PDT) Sender: Minchan Kim Date: Thu, 15 Sep 2022 16:36:36 +0000 From: Minchan Kim To: Sergey Senozhatsky Cc: Andrew Morton , Nitin Gupta , Brian Geffon , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv2] zram: do not waste zram_table_entry flags bits Message-ID: References: <20220912152744.527438-1-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220912152744.527438-1-senozhatsky@chromium.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 13, 2022 at 12:27:44AM +0900, Sergey Senozhatsky wrote: > zram_table_entry::flags stores object size in the lower bits and > zram pageflags in the upper bits. However, for some reason, we > use 24 lower bits, while maximum zram object size is PAGE_SIZE, > which requires PAGE_SHIFT bits (up to 16 on arm64). This wastes > 24 - PAGE_SHIFT bits that we can use for additional zram pageflags > instead. > > Also add a BUILD_BUG_ON() to alert us should we run out of bits > in zram_table_entry::flags. > > Signed-off-by: Sergey Senozhatsky Acked-by: Minchan Kim