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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 BE6CEC1B0E3 for ; Mon, 7 Dec 2020 11:35:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C369233A2 for ; Mon, 7 Dec 2020 11:35:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727393AbgLGLf2 (ORCPT ); Mon, 7 Dec 2020 06:35:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40970 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727288AbgLGLfV (ORCPT ); Mon, 7 Dec 2020 06:35:21 -0500 Received: from mail-pf1-x443.google.com (mail-pf1-x443.google.com [IPv6:2607:f8b0:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 582A7C0613D3; Mon, 7 Dec 2020 03:34:41 -0800 (PST) Received: by mail-pf1-x443.google.com with SMTP id w6so9618883pfu.1; Mon, 07 Dec 2020 03:34:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=b/DFMWcoqrBGhrdQgSqqomqzF7zS5T+kFvHPOchokBk=; b=R9NM+LrICITDCSs61NAJazJcQQLLZOkAyWgF91yroQ30cXHAJppkpODFQHCiPkKmQn Di7C72F9xbWBRqscYUPkTutsiEPfArp2uJQhUJMFrFwCQvS74l6dGAFEUlRjW/Ws/WLb i25GvziBXB93UcCddRs/vcJrzZtwz/5Tc+/VbAAIFz9dRUGeAp5DTeSbJkdcv7XB2Gwx 3sN5hKnAOKf+OmoM35ez+biBZKuU9mmCC3Z0vH8q0qPs6i2+ilvJACrd43BNKlUYdfn+ zXXNnE5OgQCQ2GjXJLLtVka3prnPTyUz7X2Y7d5VNYlzQNmiGKs5m0h9G1bEKMENRYYK JILg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=b/DFMWcoqrBGhrdQgSqqomqzF7zS5T+kFvHPOchokBk=; b=AM33PIsfFtMVq/9u+0wAHHrcqcwwQJsk0RurgnP0Odxco1X7+UVwSkBXe3JSVd2pGu UCRBcGA6IMswvlsRJcWKGQ/zXDpgksu3kmASpR26GJY1FaT1c7oaPcIg/zUfsH8cpeYP 5rbLi4Ums9MzE+wV2Zg8iWlI1TNPCtnYKb1woUmG+xV0BDxR5KIVQzERYDlFPTulMX3l dmDzj5vh39uKM3d5ZHNGdxZu1uTvz/ZfGq7O7kaXKX26RR+VdzO49WhTE4lcQt6oreHS My9BzgqsPd+7HbeU0PcAPByYGZhmOzIdpFF71izW76mwdN2MYHMt3KDDq6yRRftuDddL 5gmw== X-Gm-Message-State: AOAM533e9Dz2Fr+qhkMaWOs6rw2lLa8rqdGO1rLXfnGqS5E+ItNxgLgX tIBcbEM42dZY4TfDie7Vxpk= X-Google-Smtp-Source: ABdhPJwpLJSMFHHVuzFaNJtee4l+tKxhbMqfSGyZXpTjn8Xdsw0wr9LXWXlJyzhmY0qsdp5ekgOemg== X-Received: by 2002:aa7:928c:0:b029:19a:de9d:fb11 with SMTP id j12-20020aa7928c0000b029019ade9dfb11mr15718593pfa.21.1607340880960; Mon, 07 Dec 2020 03:34:40 -0800 (PST) Received: from localhost.localdomain ([203.205.141.39]) by smtp.gmail.com with ESMTPSA id d4sm14219822pfo.127.2020.12.07.03.34.37 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 07 Dec 2020 03:34:39 -0800 (PST) From: yulei.kernel@gmail.com X-Google-Original-From: yuleixzhang@tencent.com To: linux-mm@kvack.org, akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, naoya.horiguchi@nec.com, viro@zeniv.linux.org.uk, pbonzini@redhat.com Cc: joao.m.martins@oracle.com, rdunlap@infradead.org, sean.j.christopherson@intel.com, xiaoguangrong.eric@gmail.com, kernellwp@gmail.com, lihaiwei.kernel@gmail.com, Yulei Zhang , Chen Zhuo Subject: [RFC V2 18/37] mm: follow_pmd_mask() for dmem huge pmd Date: Mon, 7 Dec 2020 19:31:11 +0800 Message-Id: <1401155e1db8221b892fb935204ad2d358c2808f.1607332046.git.yuleixzhang@tencent.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yulei Zhang While follow_pmd_mask(), dmem huge pmd should be recognized and return error pointer of '-EEXIST' to indicate that proper page table entry exists in pmd special but no corresponding struct page, because dmem page means non struct page backend. We update pmd if foll_flags takes FOLL_TOUCH. Signed-off-by: Chen Zhuo Signed-off-by: Yulei Zhang --- mm/gup.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/mm/gup.c b/mm/gup.c index 98eb8e6..ad1aede 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -387,6 +387,42 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, return -EEXIST; } +static struct page * +follow_special_pmd(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmd, unsigned int flags) +{ + spinlock_t *ptl; + + if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) + /* Avoid special (like zero) pages in core dumps */ + return ERR_PTR(-EFAULT); + + /* No page to get reference */ + if (flags & FOLL_GET) + return ERR_PTR(-EFAULT); + + if (flags & FOLL_TOUCH) { + pmd_t _pmd; + + ptl = pmd_lock(vma->vm_mm, pmd); + if (!pmd_special(*pmd)) { + spin_unlock(ptl); + return NULL; + } + _pmd = pmd_mkyoung(*pmd); + if (flags & FOLL_WRITE) + _pmd = pmd_mkdirty(_pmd); + if (pmdp_set_access_flags(vma, address & HPAGE_PMD_MASK, + pmd, _pmd, + flags & FOLL_WRITE)) + update_mmu_cache_pmd(vma, address, pmd); + spin_unlock(ptl); + } + + /* Proper page table entry exists, but no corresponding struct page */ + return ERR_PTR(-EEXIST); +} + /* * FOLL_FORCE can write to even unwritable pte's, but only * after we've gone through a COW cycle and they are dirty. @@ -571,6 +607,12 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, return page; return no_page_table(vma, flags); } + if (pmd_special(*pmd)) { + page = follow_special_pmd(vma, address, pmd, flags); + if (page) + return page; + return no_page_table(vma, flags); + } if (is_hugepd(__hugepd(pmd_val(pmdval)))) { page = follow_huge_pd(vma, address, __hugepd(pmd_val(pmdval)), flags, -- 1.8.3.1