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 0AA57C00140 for ; Fri, 12 Aug 2022 22:35:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235808AbiHLWff (ORCPT ); Fri, 12 Aug 2022 18:35:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230118AbiHLWfe (ORCPT ); Fri, 12 Aug 2022 18:35:34 -0400 Received: from mail-ej1-x629.google.com (mail-ej1-x629.google.com [IPv6:2a00:1450:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D216F140F5 for ; Fri, 12 Aug 2022 15:35:32 -0700 (PDT) Received: by mail-ej1-x629.google.com with SMTP id tl27so4241046ejc.1 for ; Fri, 12 Aug 2022 15:35:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc; bh=3dffNjg2V0ub9IqECEnMjPuejsK+v8sH/hcA92lXNTc=; b=hEZxHTSxBe1hplwyOwm0+i2gkHMpgTNdq52QOu5OXHE2Dnuqb0Iz8m0Vuz4T9wbOKm fVVsMc0VJTvjT24VEquLY6eBxrd+Lskz2l0Z684wl6ZwhbtORqNGYBLvDMAVP91HsfmM AMXvi4+yxzaEc+J+kxCW+6Br5sdxnDeU7Eea0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc; bh=3dffNjg2V0ub9IqECEnMjPuejsK+v8sH/hcA92lXNTc=; b=0U4UfSijxolqgzFfhbJFcbuHVKbGpVN/Db7AUYfInZEwxPd6d6kNctDetrPkPxlJ+V SxMKUlxiNuzu1gE9yUyNreofYedeVFEMC+Ebxgr8G35BOBHWLR9712j5o9PJVZJoKAbn uMix6zg+9CLpK/sCK/9sjARH8btZdTqz/bU3UU/gzHfv4VT5xoy8/zL+f0oWQB/jGamT 83ozu2IGajjBudibaVirea/8AFwit4g87sVau5U+cLysKDqdufMmA80WAjC9lTV4uTRv 8xYCBslgLgp+Bf+tpvnZBddvWHviOxDP0E9qrEjRqp4LQo1UUNG1ZL9NMsSEYhGW6o0z I3eA== X-Gm-Message-State: ACgBeo0g/gGbtah9BHpY7b72sJkl8kLjKupY1N+S0Iy+czfxh25JhHff WhnPNpP4MihzFoGTZr4AxRzLWZOn7WikQrvs X-Google-Smtp-Source: AA6agR4Qyg/3YZ+IOP0qQjmXAtSEdKokzpMiMuepP6mlaiWAjJUz+IwcSwYPH0P5Ce/TSsItDe5hTw== X-Received: by 2002:a17:906:7945:b0:731:2aeb:7941 with SMTP id l5-20020a170906794500b007312aeb7941mr3834385ejo.449.1660343731138; Fri, 12 Aug 2022 15:35:31 -0700 (PDT) Received: from mail-wr1-f45.google.com (mail-wr1-f45.google.com. [209.85.221.45]) by smtp.gmail.com with ESMTPSA id c15-20020aa7d60f000000b0043d6ece495asm2030704edr.55.2022.08.12.15.35.30 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Aug 2022 15:35:30 -0700 (PDT) Received: by mail-wr1-f45.google.com with SMTP id l22so2535721wrz.7 for ; Fri, 12 Aug 2022 15:35:30 -0700 (PDT) X-Received: by 2002:a5d:6248:0:b0:222:cd3b:94c8 with SMTP id m8-20020a5d6248000000b00222cd3b94c8mr3196936wrv.97.1660343730228; Fri, 12 Aug 2022 15:35:30 -0700 (PDT) MIME-Version: 1.0 References: <6458eb59-554a-121b-d605-0b9755232818@kernel.dk> <433f4500-427d-8581-b852-fbe257aa6120@kernel.dk> In-Reply-To: From: Linus Torvalds Date: Fri, 12 Aug 2022 15:35:13 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] io_uring fixes for 6.0-rc1 To: Keith Busch Cc: Jens Axboe , io-uring Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Fri, Aug 12, 2022 at 3:24 PM Keith Busch wrote: > > I'd prefer if we can get away with forcing struct kiocb to not grow. The below > should have the randomization move the smallest two fields together so we don't > introduce more padding than necessary: I like this concept, but I think you might hit issues on 32-bit, where "loff_t" can be a 64-bit entity with 64-bit alignment, and then you see the same "oops, now it grew because loff_t moved" there. Note that you'd never see that on x86-32, because - for strange historical reasons - even 64-bit fields only have 32-bit alignment, but other 32-bit architectures don't act that way. Honestly, I think maybe we should just stop randomizing kiocb. Because it has six fields, and basically three of them we wouldn't want to randomly move around. At some point, randomization no longer even matters. Linus