From patchwork Tue Nov 1 22:36:25 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 9408257 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 B496B60721 for ; Tue, 1 Nov 2016 22:37:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A22B529AFF for ; Tue, 1 Nov 2016 22:37:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 96E5829B05; Tue, 1 Nov 2016 22:37:54 +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 3EBEB29AFF for ; Tue, 1 Nov 2016 22:37:54 +0000 (UTC) Received: from [127.0.0.1] (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id B375581D7B; 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 C3F4C81D57 for ; Tue, 1 Nov 2016 15:37:35 -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 2D5ABADC5; Tue, 1 Nov 2016 22:37:35 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B08EA1E0FCE; Tue, 1 Nov 2016 23:37:27 +0100 (CET) From: Jan Kara To: Subject: [PATCH 16/21] mm: Provide helper for finishing mkwrite faults Date: Tue, 1 Nov 2016 23:36:25 +0100 Message-Id: <1478039794-20253-20-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 Provide a helper function for finishing write faults due to PTE being read-only. The helper will be used by DAX to avoid the need of complicating generic MM code with DAX locking specifics. Reviewed-by: Ross Zwisler Signed-off-by: Jan Kara --- include/linux/mm.h | 1 + mm/memory.c | 67 ++++++++++++++++++++++++++++++++---------------------- 2 files changed, 41 insertions(+), 27 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 56fdd79e5d1e..0920adb6ec1b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -615,6 +615,7 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg, struct page *page); int finish_fault(struct vm_fault *vmf); +int finish_mkwrite_fault(struct vm_fault *vmf); #endif /* diff --git a/mm/memory.c b/mm/memory.c index 06aba4203104..1517ff91c743 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2270,6 +2270,38 @@ static int wp_page_copy(struct vm_fault *vmf) return VM_FAULT_OOM; } +/** + * finish_mkwrite_fault - finish page fault for a shared mapping, making PTE + * writeable once the page is prepared + * + * @vmf: structure describing the fault + * + * This function handles all that is needed to finish a write page fault in a + * shared mapping due to PTE being read-only once the mapped page is prepared. + * It handles locking of PTE and modifying it. The function returns + * VM_FAULT_WRITE on success, 0 when PTE got changed before we acquired PTE + * lock. + * + * The function expects the page to be locked or other protection against + * concurrent faults / writeback (such as DAX radix tree locks). + */ +int finish_mkwrite_fault(struct vm_fault *vmf) +{ + WARN_ON_ONCE(!(vmf->vma->vm_flags & VM_SHARED)); + vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, vmf->address, + &vmf->ptl); + /* + * We might have raced with another page fault while we released the + * pte_offset_map_lock. + */ + if (!pte_same(*vmf->pte, vmf->orig_pte)) { + pte_unmap_unlock(vmf->pte, vmf->ptl); + return 0; + } + wp_page_reuse(vmf); + return VM_FAULT_WRITE; +} + /* * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED * mapping @@ -2286,16 +2318,7 @@ static int wp_pfn_shared(struct vm_fault *vmf) ret = vma->vm_ops->pfn_mkwrite(vma, vmf); if (ret & VM_FAULT_ERROR) return ret; - vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, - vmf->address, &vmf->ptl); - /* - * We might have raced with another page fault while we - * released the pte_offset_map_lock. - */ - if (!pte_same(*vmf->pte, vmf->orig_pte)) { - pte_unmap_unlock(vmf->pte, vmf->ptl); - return 0; - } + return finish_mkwrite_fault(vmf); } wp_page_reuse(vmf); return VM_FAULT_WRITE; @@ -2305,7 +2328,6 @@ static int wp_page_shared(struct vm_fault *vmf) __releases(vmf->ptl) { struct vm_area_struct *vma = vmf->vma; - int page_mkwrite = 0; get_page(vmf->page); @@ -2319,26 +2341,17 @@ static int wp_page_shared(struct vm_fault *vmf) put_page(vmf->page); return tmp; } - /* - * Since we dropped the lock we need to revalidate - * the PTE as someone else may have changed it. If - * they did, we just return, as we can count on the - * MMU to tell us if they didn't also make it writable. - */ - vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, - vmf->address, &vmf->ptl); - if (!pte_same(*vmf->pte, vmf->orig_pte)) { + tmp = finish_mkwrite_fault(vmf); + if (unlikely(!tmp || (tmp & + (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) { unlock_page(vmf->page); - pte_unmap_unlock(vmf->pte, vmf->ptl); put_page(vmf->page); - return 0; + return tmp; } - page_mkwrite = 1; - } - - wp_page_reuse(vmf); - if (!page_mkwrite) + } else { + wp_page_reuse(vmf); lock_page(vmf->page); + } fault_dirty_shared_page(vma, vmf->page); put_page(vmf->page);