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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 18301C433FF for ; Thu, 8 Aug 2019 16:37:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E818B217D7 for ; Thu, 8 Aug 2019 16:37:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390171AbfHHQhs (ORCPT ); Thu, 8 Aug 2019 12:37:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16383 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725535AbfHHQhs (ORCPT ); Thu, 8 Aug 2019 12:37:48 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 327817BDDA; Thu, 8 Aug 2019 16:37:48 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.136]) by smtp.corp.redhat.com (Postfix) with SMTP id 6AEDE5D784; Thu, 8 Aug 2019 16:37:46 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 8 Aug 2019 18:37:47 +0200 (CEST) Date: Thu, 8 Aug 2019 18:37:45 +0200 From: Oleg Nesterov To: Song Liu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, matthew.wilcox@oracle.com, kirill.shutemov@linux.intel.com, kernel-team@fb.com, william.kucharski@oracle.com, srikar@linux.vnet.ibm.com Subject: Re: [PATCH v12 3/6] mm, thp: introduce FOLL_SPLIT_PMD Message-ID: <20190808163745.GC7934@redhat.com> References: <20190807233729.3899352-1-songliubraving@fb.com> <20190807233729.3899352-4-songliubraving@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190807233729.3899352-4-songliubraving@fb.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 08 Aug 2019 16:37:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/07, Song Liu wrote: > > @@ -399,7 +399,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, > spin_unlock(ptl); > return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); > } > - if (flags & FOLL_SPLIT) { > + if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) { > int ret; > page = pmd_page(*pmd); > if (is_huge_zero_page(page)) { > @@ -408,7 +408,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, > split_huge_pmd(vma, pmd, address); > if (pmd_trans_unstable(pmd)) > ret = -EBUSY; > - } else { > + } else if (flags & FOLL_SPLIT) { > if (unlikely(!try_get_page(page))) { > spin_unlock(ptl); > return ERR_PTR(-ENOMEM); > @@ -420,6 +420,10 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, > put_page(page); > if (pmd_none(*pmd)) > return no_page_table(vma, flags); > + } else { /* flags & FOLL_SPLIT_PMD */ > + spin_unlock(ptl); > + split_huge_pmd(vma, pmd, address); > + ret = pte_alloc(mm, pmd) ? -ENOMEM : 0; > } Can't resist, let me repeat that I do not like this patch because imo it complicates this code for no reason. But I can't insist and of course I could miss something. Oleg.