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=-3.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 7050AC433DF for ; Sat, 22 Aug 2020 19:37:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51C68207CD for ; Sat, 22 Aug 2020 19:37:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=tfz-net.20150623.gappssmtp.com header.i=@tfz-net.20150623.gappssmtp.com header.b="mE1R29cU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728713AbgHVThB (ORCPT ); Sat, 22 Aug 2020 15:37:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60204 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728640AbgHVTg4 (ORCPT ); Sat, 22 Aug 2020 15:36:56 -0400 Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 28750C061574 for ; Sat, 22 Aug 2020 12:36:56 -0700 (PDT) Received: by mail-wm1-x341.google.com with SMTP id f18so3421041wmc.0 for ; Sat, 22 Aug 2020 12:36:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tfz-net.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=D2UpM4JiRz3DSJbLEVUit3CMbJBOHMsg2oZwhaPpIVA=; b=mE1R29cUE7e5dkG7Erf7qXQPY5FC1XBoN3dQ3DNlq6pOwtQs2QA/HXJg+Dgi5aOmH0 eukcJ8ZutRhpaQncdPJv6JPb+cI8dUgxhZOl7G7h/+GRuyQAtNLkf8bbjBOFeimdSOEw OaSqA1PNnbdqb/ubLToV2eloOntz6ZLCiKy70oadVyFZ6JzY3sG06ZyzadCo2EyeY4nG 3JyI0xU5lcq7UK77Ay6zWGuRPL+JSUd8q02b2LvB8p3d4NzD1i5DxjlxVKlcNoBjBOzM VtysgUcFhUiCjFFRHWw5qkE45NrxOCH/R44dGkF6SqKuKXiIW/RNpcd0ktK642yGEniJ kzBw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=D2UpM4JiRz3DSJbLEVUit3CMbJBOHMsg2oZwhaPpIVA=; b=lGf18WlywJJQmo8kmw6IYDofcOOyJcSQELp+xX8TGVZJ8NPC8H55GzSVDB+r4gVJky tWEPL+l5m3z+wrLYFkYDgpzyOpDrRI/aTuB7qeBfI/4I7/uGMAX/GURmq73bm6Iuvqlq fK+MxBVsnGkC6XvYx9bJzxcX5+7FLYRD74BZMJ/4Fd255C6EeAlhjgkg20RLz4Wtfdll 7kuZUsalp5pg8jhNPYNtUzun7/VqiH1aTOOL+S2Q+Y7T8dSj5a4wterbbZQCfQY+zn2s O8u3gbEtsTyV/IdRsCgD+KQoI0aMeI5zxf0BuNGYInJW2eTkqHORjcOzCxPxQIiF4mHb X3ng== X-Gm-Message-State: AOAM533mVRh/vGNZ7n6qHNZe7z8QYdesdq2SE5MIEUiy33vxVqYnSFll l2pZyPxTbNZHmBEVQH3gd0oqodtFX+gxk6duwGUC7w== X-Google-Smtp-Source: ABdhPJw1FjXS8okxIasqbI2eFqqO4wV94l6O3Rxxnnk5P/VzZuRcNZ/6J3YlyMeLV+ABXrCSAZNjs+lqNalSNkMLC0c= X-Received: by 2002:a7b:c15a:: with SMTP id z26mr8502959wmi.35.1598125014765; Sat, 22 Aug 2020 12:36:54 -0700 (PDT) MIME-Version: 1.0 References: <20200815182344.7469-1-kalou@tfz.net> <20200822032827.6386-1-kalou@tfz.net> <20200821205154.365e230dbf6f2b93a47443c4@linux-foundation.org> In-Reply-To: <20200821205154.365e230dbf6f2b93a47443c4@linux-foundation.org> From: Pascal Bouchareine Date: Sat, 22 Aug 2020 12:36:44 -0700 Message-ID: Subject: Re: [PATCH v2 1/2] mm: add GFP mask param to strndup_user To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, netdev@vger.kernel.org, "David S. Miller" , Jakub Kicinski , Alexey Dobriyan , Al Viro Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Thanks for taking a look! On Fri, Aug 21, 2020 at 8:51 PM Andrew Morton wrote: > Why change all existing callsites so that one callsite can pass in a > different gfp_t? My initial thought was to change strndup_user to use GFP_KERNEL_ACCOUNT (or GFP_USER | __GFP_ACCOUNT ?) unconditionally. (Would that work? that would be a simpler change for sure) In the case it was not wanted, I assumed a good proportion of callers might do the same on a case-by-case basis (esp. with regards to enabling accounting). > Also... > > why does strndup_user() use GFP_USER? Nobody will be mapping the > resulting strings into user pagetables (will they?). This was done by > Al's 6c2c97a24f096e32, which doesn't have a changelog :( FWIW, I believe related to this: https://lkml.org/lkml/2018/1/6/333 It's a bit over my head (is GFP_USER cheaper?) if strndup_user needs to follow memdup_user > In [patch 2/2], > > + desc = strndup_user(user_desc, SK_MAX_DESC_SIZE, GFP_KERNEL_ACCOUNT); > > if GFP_USER is legit then shouldn't this be GFP_USER_ACCOUNT (ie, > GFP_USER|__GFP_ACCOUNT)? Yes! I'll see clearer if I manage to wrap my head around what strndup_user should do Thanks!