From patchwork Tue Nov 1 22:36:26 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 9408263 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 AAEB860721 for ; Tue, 1 Nov 2016 22:37:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9B0E929AFF for ; Tue, 1 Nov 2016 22:37:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8FD3D29B05; Tue, 1 Nov 2016 22:37:56 +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, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 39ED429AFF for ; Tue, 1 Nov 2016 22:37:56 +0000 (UTC) Received: from [127.0.0.1] (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id CBD5281D83; Tue, 1 Nov 2016 15:37:38 -0700 (PDT) X-Original-To: linux-nvdimm@lists.01.org Delivered-To: linux-nvdimm@lists.01.org Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 59A3C81D66 for ; Tue, 1 Nov 2016 15:37:36 -0700 (PDT) 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 6B883ADCB; Tue, 1 Nov 2016 22:37:36 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B36501E0FD0; Tue, 1 Nov 2016 23:37:27 +0100 (CET) From: Jan Kara To: Subject: [PATCH 17/21] mm: Change return values of finish_mkwrite_fault() Date: Tue, 1 Nov 2016 23:36:26 +0100 Message-Id: <1478039794-20253-21-git-send-email-jack@suse.cz> X-Mailer: git-send-email 2.6.6 In-Reply-To: <1478039794-20253-1-git-send-email-jack@suse.cz> References: <1478039794-20253-1-git-send-email-jack@suse.cz> X-BeenThere: linux-nvdimm@lists.01.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Linux-nvdimm developer list." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-fsdevel@vger.kernel.org, Andrew Morton , Jan Kara , linux-nvdimm@lists.01.org MIME-Version: 1.0 Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" 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. 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 1517ff91c743..b3bd6b6c6472 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2296,10 +2296,10 @@ 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; } /* @@ -2342,8 +2342,7 @@ 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;