From patchwork Fri Nov 18 09:17:20 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 9436063 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 4FDD160238 for ; Fri, 18 Nov 2016 09:18:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3C98729854 for ; Fri, 18 Nov 2016 09:18:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 318A92985A; Fri, 18 Nov 2016 09:18:24 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.9 required=2.0 tests=BAYES_00 autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2459729854 for ; Fri, 18 Nov 2016 09:18:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753122AbcKRJSH (ORCPT ); Fri, 18 Nov 2016 04:18:07 -0500 Received: from mx2.suse.de ([195.135.220.15]:58686 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752940AbcKRJRi (ORCPT ); Fri, 18 Nov 2016 04:17:38 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id E3217AD8A; Fri, 18 Nov 2016 09:17:29 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id BE4AA1E0FE0; Fri, 18 Nov 2016 10:17:27 +0100 (CET) From: Jan Kara To: Cc: "Kirill A. Shutemov" , Ross Zwisler , Andrew Morton , , linux-nvdimm@lists.01.org, Jan Kara Subject: [PATCH 16/20] mm: Change return values of finish_mkwrite_fault() Date: Fri, 18 Nov 2016 10:17:20 +0100 Message-Id: <1479460644-25076-17-git-send-email-jack@suse.cz> X-Mailer: git-send-email 2.6.6 In-Reply-To: <1479460644-25076-1-git-send-email-jack@suse.cz> References: <1479460644-25076-1-git-send-email-jack@suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Currently finish_mkwrite_fault() returns 0 when PTE got changed before we acquired PTE lock and VM_FAULT_WRITE when we succeeded in modifying the PTE. This is somewhat confusing since 0 generally means success, it is also inconsistent with finish_fault() which returns 0 on success. Change finish_mkwrite_fault() to return 0 on success and VM_FAULT_NOPAGE when PTE changed. Practically, there should be no behavioral difference since we bail out from the fault the same way regardless whether we return 0, VM_FAULT_NOPAGE, or VM_FAULT_WRITE. Also note that VM_FAULT_WRITE has no effect for shared mappings since the only two places that check it - KSM and GUP - care about private mappings only. Generally the meaning of VM_FAULT_WRITE for shared mappings is not well defined and we should probably clean that up. Acked-by: Kirill A. Shutemov Signed-off-by: Jan Kara --- mm/memory.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 5bb6773375ec..bf87081c8a37 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2299,10 +2299,10 @@ int finish_mkwrite_fault(struct vm_fault *vmf) */ if (!pte_same(*vmf->pte, vmf->orig_pte)) { pte_unmap_unlock(vmf->pte, vmf->ptl); - return 0; + return VM_FAULT_NOPAGE; } wp_page_reuse(vmf); - return VM_FAULT_WRITE; + return 0; } /* @@ -2345,8 +2345,7 @@ static int wp_page_shared(struct vm_fault *vmf) return tmp; } tmp = finish_mkwrite_fault(vmf); - if (unlikely(!tmp || (tmp & - (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) { + if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) { unlock_page(vmf->page); put_page(vmf->page); return tmp;