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=-8.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 28333C31E45 for ; Thu, 13 Jun 2019 17:12:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F25D22053B for ; Thu, 13 Jun 2019 17:12:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="MYkh3U+J" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393611AbfFMRMn (ORCPT ); Thu, 13 Jun 2019 13:12:43 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:52434 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729007AbfFLWGm (ORCPT ); Wed, 12 Jun 2019 18:06:42 -0400 Received: from pps.filterd (m0044008.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5CLx9JR025975 for ; Wed, 12 Jun 2019 15:06:41 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-type; s=facebook; bh=kq4OSN4555gAGkuBdC1pCdofeLuUMnKNDEdg6BpuyMo=; b=MYkh3U+Ju7SqSxVPQrNXSAF+zvZ9PcRsQQDXJE24KvAVT9tY7UMNyR+CJi3WNtay3Uqh A2Gd0CQrwjeMl8FMIvWIQa+WwTyvwpbAQzh2ItVZvgwSI/YPjM7YuEJJTYMZMxLfcSli WR6tRr0HbvftJ4if31pP0NfFpizKrmvQquU= Received: from mail.thefacebook.com (mailout.thefacebook.com [199.201.64.23]) by mx0a-00082601.pphosted.com with ESMTP id 2t38x6r6mb-7 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT) for ; Wed, 12 Jun 2019 15:06:41 -0700 Received: from mx-out.facebook.com (2620:10d:c081:10::13) by mail.thefacebook.com (2620:10d:c081:35::125) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA) id 15.1.1713.5; Wed, 12 Jun 2019 15:06:16 -0700 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id B9B4B62E2D1F; Wed, 12 Jun 2019 15:03:45 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig006.ftw2.facebook.com To: , CC: , , , , , , , , Song Liu Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH v3 6/6] mm, thp: introduce FOLL_SPLIT_PMD Date: Wed, 12 Jun 2019 15:03:20 -0700 Message-ID: <20190612220320.2223898-7-songliubraving@fb.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190612220320.2223898-1-songliubraving@fb.com> References: <20190612220320.2223898-1-songliubraving@fb.com> X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-12_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906120153 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patches introduces a new foll_flag: FOLL_SPLIT_PMD. As the name says FOLL_SPLIT_PMD splits huge pmd for given mm_struct, the underlining huge page stays as-is. FOLL_SPLIT_PMD is useful for cases where we need to use regular pages, but would switch back to huge page and huge pmd on. One of such example is uprobe. The following patches use FOLL_SPLIT_PMD in uprobe. Signed-off-by: Song Liu --- include/linux/mm.h | 1 + mm/gup.c | 38 +++++++++++++++++++++++++++++++++++--- 2 files changed, 36 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 0ab8c7d84cd0..e605acc4fc81 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2642,6 +2642,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, #define FOLL_COW 0x4000 /* internal GUP flag */ #define FOLL_ANON 0x8000 /* don't do file mappings */ #define FOLL_LONGTERM 0x10000 /* mapping lifetime is indefinite: see below */ +#define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */ /* * NOTE on FOLL_LONGTERM: diff --git a/mm/gup.c b/mm/gup.c index ddde097cf9e4..3d05bddb56c9 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -398,7 +398,7 @@ 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)) { @@ -407,7 +407,7 @@ 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); @@ -419,8 +419,40 @@ 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 */ + unsigned long addr; + pgprot_t prot; + pte_t *pte; + int i; + + spin_unlock(ptl); + split_huge_pmd(vma, pmd, address); + lock_page(page); + pte = get_locked_pte(mm, address, &ptl); + if (!pte) { + unlock_page(page); + return no_page_table(vma, flags); + } + /* get refcount for every small page */ + page_ref_add(page, HPAGE_PMD_NR); + + prot = READ_ONCE(vma->vm_page_prot); + for (i = 0, addr = address & PMD_MASK; + i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { + struct page *p = page + i; + + pte = pte_offset_map(pmd, addr); + VM_BUG_ON(!pte_none(*pte)); + set_pte_at(mm, addr, pte, mk_pte(p, prot)); + page_add_file_rmap(p, false); + } + + spin_unlock(ptl); + unlock_page(page); + add_mm_counter(mm, mm_counter_file(page), HPAGE_PMD_NR); + ret = 0; + } return ret ? ERR_PTR(ret) : follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); } -- 2.17.1