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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 102DCC10F00 for ; Thu, 21 Mar 2019 14:57:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D65CF218D4 for ; Thu, 21 Mar 2019 14:57:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553180270; bh=JWxj8nksQ6TJk06DnuIJpyiELHXjQgIu2lG938gJHBM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=rTaKIIYrFJQn4p0HanYNoHTqC3rR/XvU2bftJrdjvw9B+aZDcethhghegwjbDXalK rUXxD/G1LZICMyOOVNNgCk9GU1tvg53qMV7WvojBTvwcLfah1GRJrwfFryCJsHLOk7 0v4TM1GNF/Hbg18WUKRmds3Xl+jfwdaZwv/t5efc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728386AbfCUO5t (ORCPT ); Thu, 21 Mar 2019 10:57:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:53126 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727922AbfCUO5t (ORCPT ); Thu, 21 Mar 2019 10:57:49 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id CD105ABDC; Thu, 21 Mar 2019 14:57:46 +0000 (UTC) Date: Thu, 21 Mar 2019 15:57:45 +0100 From: Michal Hocko To: Yang Shi Cc: mgorman@techsingularity.net, vbabka@suse.cz, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mm: mempolicy: remove MPOL_MF_LAZY Message-ID: <20190321145745.GS8696@dhcp22.suse.cz> References: <1553041659-46787-1-git-send-email-yang.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1553041659-46787-1-git-send-email-yang.shi@linux.alibaba.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 20-03-19 08:27:39, Yang Shi wrote: > MPOL_MF_LAZY was added by commit b24f53a0bea3 ("mm: mempolicy: Add > MPOL_MF_LAZY"), then it was disabled by commit a720094ded8c ("mm: > mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now") > right away in 2012. So, it is never ever exported to userspace. > > And, it looks nobody is interested in revisiting it since it was > disabled 7 years ago. So, it sounds pointless to still keep it around. The above changelog owes us a lot of explanation about why this is safe and backward compatible. I am also not sure you can change MPOL_MF_INTERNAL because somebody still might use the flag from userspace and we want to guarantee it will have the exact same semantic. > Cc: Mel Gorman > Cc: Michal Hocko > Cc: Vlastimil Babka > Signed-off-by: Yang Shi > --- > Hi folks, > I'm not sure if you still would like to revisit it later. And, I may be > not the first one to try to remvoe it. IMHO, it sounds pointless to still > keep it around if nobody is interested in it. > > include/uapi/linux/mempolicy.h | 3 +-- > mm/mempolicy.c | 13 ------------- > 2 files changed, 1 insertion(+), 15 deletions(-) > > diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h > index 3354774..eb52a7a 100644 > --- a/include/uapi/linux/mempolicy.h > +++ b/include/uapi/linux/mempolicy.h > @@ -45,8 +45,7 @@ enum { > #define MPOL_MF_MOVE (1<<1) /* Move pages owned by this process to conform > to policy */ > #define MPOL_MF_MOVE_ALL (1<<2) /* Move every page to conform to policy */ > -#define MPOL_MF_LAZY (1<<3) /* Modifies '_MOVE: lazy migrate on fault */ > -#define MPOL_MF_INTERNAL (1<<4) /* Internal flags start here */ > +#define MPOL_MF_INTERNAL (1<<3) /* Internal flags start here */ > > #define MPOL_MF_VALID (MPOL_MF_STRICT | \ > MPOL_MF_MOVE | \ > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index af171cc..67886f4 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -593,15 +593,6 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, > > qp->prev = vma; > > - if (flags & MPOL_MF_LAZY) { > - /* Similar to task_numa_work, skip inaccessible VMAs */ > - if (!is_vm_hugetlb_page(vma) && > - (vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)) && > - !(vma->vm_flags & VM_MIXEDMAP)) > - change_prot_numa(vma, start, endvma); > - return 1; > - } > - > /* queue pages from current vma */ > if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) > return 0; > @@ -1181,9 +1172,6 @@ static long do_mbind(unsigned long start, unsigned long len, > if (IS_ERR(new)) > return PTR_ERR(new); > > - if (flags & MPOL_MF_LAZY) > - new->flags |= MPOL_F_MOF; > - > /* > * If we are using the default policy then operation > * on discontinuous address spaces is okay after all > @@ -1226,7 +1214,6 @@ static long do_mbind(unsigned long start, unsigned long len, > int nr_failed = 0; > > if (!list_empty(&pagelist)) { > - WARN_ON_ONCE(flags & MPOL_MF_LAZY); > nr_failed = migrate_pages(&pagelist, new_page, NULL, > start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND); > if (nr_failed) > -- > 1.8.3.1 > -- Michal Hocko SUSE Labs