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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 BB8BCC4708B for ; Thu, 27 May 2021 20:19:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D493613EB for ; Thu, 27 May 2021 20:19:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236017AbhE0UVU (ORCPT ); Thu, 27 May 2021 16:21:20 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:52733 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235818AbhE0UVQ (ORCPT ); Thu, 27 May 2021 16:21:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622146782; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wtpikodp79ycSP9XpJQBScIRhvTfN0ZcMiLJ1ThP9JQ=; b=iqQuAbPIsdOB5+uVKWixWFNYEESGn83iQJqCEUZZ1qcOyJgnhM5/zaD34Ep834iknw44Be A5oSMFLaMII5ibkU3Nsl975yIBJjXM0efGiEC+YqfZx4WL2Ylv74PhaV7SyY/73rPS07JG XkAXUCVGNf5VjLN5W0RFAub99jtqTIc= Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-586-L9Vee-K_M4OQFb8j3pFnnw-1; Thu, 27 May 2021 16:19:40 -0400 X-MC-Unique: L9Vee-K_M4OQFb8j3pFnnw-1 Received: by mail-qk1-f197.google.com with SMTP id o14-20020a05620a130eb02902ea53a6ef80so1342599qkj.6 for ; Thu, 27 May 2021 13:19:40 -0700 (PDT) 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=wtpikodp79ycSP9XpJQBScIRhvTfN0ZcMiLJ1ThP9JQ=; b=fPGbG/QlkHEu6yKP4SpaVwCLMFY+PKEvTDVtA1ext+WB1piHgQHnevqK4T1OkF7mE/ 4QTbuj08wG/rEc11GmCIeFVLMBrJXKAkhejO8aTny/ApqTFDQC0oUZHJ2MfHR+8Ni/Hc +g3rldrJX8e+nHnZOleiLwMalTTUn/R1YAbBYzXxsRufcdDh9C8tBSK+hcEjcq1ANggK aHBGKd0QPi/pq/6iWu1UUYdrJhkASkDSBXHoxhirRRphkm19Z0Bw6k2lssBiUfXo7Z3Z Ua6L7T3OVTv9RKMTedFGsFk5zu87BX12RMMdJvyCrfD4LO6cy+OM7J9oPEEUJadFPYAH ltdw== X-Gm-Message-State: AOAM532a74EPIHUhPXSMKrEgIqqy4uqenIrnn9sR+/iwgvAqf7Iykj85 cIS3Uplr0E1jRDrrL+oNxCJ+UgNrQDzFivcBiffoSUIUqVG7NgAk3inrlXm61BfVT7wdNXEexqX sJUxfV3SjhFrLYdr0nRbxfSxmBEWs96oJAoVqZhTwQsF/pbtdTP4TOo0Zcbr4ZhKkl7/erdfD2g == X-Received: by 2002:a37:9b84:: with SMTP id d126mr286664qke.209.1622146779835; Thu, 27 May 2021 13:19:39 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy4BrGFtNQT6/UXbcwV9vau/8TD3QkZQ1uE6aEORoTDdjOwC1wOoNc2OKlNxy0x4hF1f7DlsQ== X-Received: by 2002:a37:9b84:: with SMTP id d126mr286628qke.209.1622146779507; Thu, 27 May 2021 13:19:39 -0700 (PDT) Received: from localhost.localdomain (bras-base-toroon474qw-grc-72-184-145-4-219.dsl.bell.ca. [184.145.4.219]) by smtp.gmail.com with ESMTPSA id u14sm2089536qkp.80.2021.05.27.13.19.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 May 2021 13:19:38 -0700 (PDT) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Axel Rasmussen , "Kirill A . Shutemov" , Hugh Dickins , Andrew Morton , Miaohe Lin , Mike Rapoport , Jerome Glisse , Andrea Arcangeli , Nadav Amit , Mike Kravetz , peterx@redhat.com, Jason Gunthorpe , Matthew Wilcox Subject: [PATCH v3 03/27] mm: Clear vmf->pte after pte_unmap_same() returns Date: Thu, 27 May 2021 16:19:03 -0400 Message-Id: <20210527201927.29586-4-peterx@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210527201927.29586-1-peterx@redhat.com> References: <20210527201927.29586-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org pte_unmap_same() will always unmap the pte pointer. After the unmap, vmf->pte will not be valid any more. We should clear it. It was safe only because no one is accessing vmf->pte after pte_unmap_same() returns, since the only caller of pte_unmap_same() (so far) is do_swap_page(), where vmf->pte will in most cases be overwritten very soon. pte_unmap_same() will be used in other places in follow up patches, so that vmf->pte will not always be re-written. This patch enables us to call functions like finish_fault() because that'll conditionally unmap the pte by checking vmf->pte first. Or, alloc_set_pte() will make sure to allocate a new pte even after calling pte_unmap_same(). Since we'll need to modify vmf->pte, directly pass in vmf into pte_unmap_same() and then we can also avoid the long parameter list. Reviewed-by: Miaohe Lin Signed-off-by: Peter Xu --- mm/memory.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 2b7ffcbca175..0ccaae2647c0 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2710,19 +2710,20 @@ EXPORT_SYMBOL_GPL(apply_to_existing_page_range); * proceeding (but do_wp_page is only called after already making such a check; * and do_anonymous_page can safely check later on). */ -static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd, - pte_t *page_table, pte_t orig_pte) +static inline int pte_unmap_same(struct vm_fault *vmf) { int same = 1; #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPTION) if (sizeof(pte_t) > sizeof(unsigned long)) { - spinlock_t *ptl = pte_lockptr(mm, pmd); + spinlock_t *ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); spin_lock(ptl); - same = pte_same(*page_table, orig_pte); + same = pte_same(*vmf->pte, vmf->orig_pte); spin_unlock(ptl); } #endif - pte_unmap(page_table); + pte_unmap(vmf->pte); + /* After unmap of pte, the pointer is invalid now - clear it. */ + vmf->pte = NULL; return same; } @@ -3441,7 +3442,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) vm_fault_t ret = 0; void *shadow = NULL; - if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte)) + if (!pte_unmap_same(vmf)) goto out; entry = pte_to_swp_entry(vmf->orig_pte); -- 2.31.1