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 267C0C25B08 for ; Fri, 5 Aug 2022 02:44:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236553AbiHECow (ORCPT ); Thu, 4 Aug 2022 22:44:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54448 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233983AbiHECou (ORCPT ); Thu, 4 Aug 2022 22:44:50 -0400 Received: from mail-pf1-x42d.google.com (mail-pf1-x42d.google.com [IPv6:2607:f8b0:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C444270E69 for ; Thu, 4 Aug 2022 19:44:49 -0700 (PDT) Received: by mail-pf1-x42d.google.com with SMTP id 17so1168961pfy.0 for ; Thu, 04 Aug 2022 19:44:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc; bh=Ge650nsibp9BJRcwR8vjT9DTFibFHRWpu3X6S8ZIxw4=; b=EhC8cdWn6CptK/UCyIMOwYDGIEL4wVO1KUvpBFSm4ssWHjz13EnExX5VpGtd1Ls2TM qgh3dw24BJ715TduWcIiaUEtTt0s+DzZnR6lJgadXcbZVwl2JfOR17IDWhzibNOgKXLE Ji6f2HrahxQYIMQlsWI5RO9vzTGa25axFYdvLx464MCyQAJTKvo+clPrL6Olu4Oe7caF Yhwi2VUekDd2F3gYqgnejYcE7KjvEFJeUsYqktBUI608MNQjVrSARgmToBehGsNyXZ49 /Ze2bjhdsmBBnB/YQyTcPsrXAtpfdpIBhaqbiMokVJ6AkCmISlpJTfdJOSlguySGbm51 EH2A== 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:x-gm-message-state:from:to:cc; bh=Ge650nsibp9BJRcwR8vjT9DTFibFHRWpu3X6S8ZIxw4=; b=C/74T6Eclxr6lUjNm0hBKKC4D6zZUJERhftuVJSZ+uvT/MogIgYMXGK7+tTRATv9LT SpVD/ojsR8GPxVBlpEmK7dn6L8DJT4Y3Rm/4efs2OLTEjxdJeStosBc/CenlTC6xINmu fPSOxI6YeGgXQ9xdNUVIb7BHQFQ4yKLYbYIk+0emNx11MMbsFvOD7WSAkaB7UnQ6t5K1 eyhjU+XjUrumYgBZbGbsRIGO5vwjzDtevbAQbWHzV/CcNk7K/FsNYFL5M4WK8MXeWNNK QupKyq6zVc7rwKl2Ea27oputoWj+909ybfR5OUdnfRK+6QYojbBKJPyDuXvupblzlpRb SM9w== X-Gm-Message-State: ACgBeo0WRS05Eml4D+9Aw7iIRb3VDRGlVzCFapvBgKImRWgn7jR4KFAS LV7XIu2p8cXfjQbQiDEj7CVVBw== X-Google-Smtp-Source: AA6agR4ckl2JHPiW/tp9tke26knPbADR0uC+WjekY6sh31/R9hzVRt0A1VAItLW5bvJatvE9mF0jNQ== X-Received: by 2002:aa7:909a:0:b0:52b:3afb:fc49 with SMTP id i26-20020aa7909a000000b0052b3afbfc49mr4622761pfa.39.1659667489212; Thu, 04 Aug 2022 19:44:49 -0700 (PDT) Received: from localhost ([139.177.225.249]) by smtp.gmail.com with ESMTPSA id c78-20020a624e51000000b0052ce1737ee1sm1748693pfb.37.2022.08.04.19.44.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Aug 2022 19:44:48 -0700 (PDT) Date: Fri, 5 Aug 2022 10:44:35 +0800 From: Muchun Song To: Feng Tang Cc: Andrew Morton , Mike Kravetz , Michal Hocko , Dave Hansen , Ben Widawsky , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/hugetlb: add dedicated func to get 'allowed' nodemask for current process Message-ID: References: <20220805005903.95563-1-feng.tang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220805005903.95563-1-feng.tang@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 05, 2022 at 08:59:03AM +0800, Feng Tang wrote: > Muchun Song found that after MPOL_PREFERRED_MANY policy was introduced > in commit b27abaccf8e8 ("mm/mempolicy: add MPOL_PREFERRED_MANY for multiple preferred nodes"), > the policy_nodemask_current()'s semantics for this new policy has been > changed, which returns 'preferred' nodes instead of 'allowed' nodes. > > With the changed semantic of policy_nodemask_current, a task with > MPOL_PREFERRED_MANY policy could fail to get its reservation even though > it can fall back to other nodes (either defined by cpusets or all online > nodes) for that reservation failing mmap calles unnecessarily early. > > The fix is to not consider MPOL_PREFERRED_MANY for reservations at all > because they, unlike MPOL_MBIND, do not pose any actual hard constrain. > > Michal suggested the policy_nodemask_current() is only used by hugetlb, > and could be moved to hugetlb code with more explicit name to enforce > the 'allowed' semantics for which only MPOL_BIND policy matters. > > apply_policy_zone() is made extern to be called in hugetlb code > and its return value is changed to bool. > > [1]. https://lore.kernel.org/lkml/20220801084207.39086-1-songmuchun@bytedance.com/t/ > > Fixes: b27abaccf8e8 ("mm/mempolicy: add MPOL_PREFERRED_MANY for multiple preferred nodes") > Reported-by: Muchun Song > Suggested-by: Michal Hocko > Signed-off-by: Feng Tang > Acked-by: Michal Hocko Thanks for fixing this. Reviewed-by: Muchun Song