From patchwork Tue Nov 1 22:36:31 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 9408233 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 BC98E60721 for ; Tue, 1 Nov 2016 22:37:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id AC2CC29AFF for ; Tue, 1 Nov 2016 22:37:47 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A0DE029B05; Tue, 1 Nov 2016 22:37:47 +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 630BC29AFF for ; Tue, 1 Nov 2016 22:37:47 +0000 (UTC) Received: from [127.0.0.1] (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 5BFDD81D47; 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 9FE0381D51 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 2C534ADC4; Tue, 1 Nov 2016 22:37:35 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id BF20C1E0FDC; Tue, 1 Nov 2016 23:37:27 +0100 (CET) From: Jan Kara To: Subject: [PATCH 19/20] dax: Protect PTE modification on WP fault by radix tree entry lock Date: Tue, 1 Nov 2016 23:36:31 +0100 Message-Id: <1478039794-20253-26-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 PTE gets updated in wp_pfn_shared() after dax_pfn_mkwrite() has released corresponding radix tree entry lock. When we want to writeprotect PTE on cache flush, we need PTE modification to happen under radix tree entry lock to ensure consisten updates of PTE and radix tree (standard faults use page lock to ensure this consistency). So move update of PTE bit into dax_pfn_mkwrite(). Signed-off-by: Jan Kara --- fs/dax.c | 22 ++++++++++++++++------ mm/memory.c | 2 +- 2 files changed, 17 insertions(+), 7 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index c6cadf8413a3..a2d3781c9f4e 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1163,17 +1163,27 @@ int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) { struct file *file = vma->vm_file; struct address_space *mapping = file->f_mapping; - void *entry; + void *entry, **slot; pgoff_t index = vmf->pgoff; spin_lock_irq(&mapping->tree_lock); - entry = get_unlocked_mapping_entry(mapping, index, NULL); - if (!entry || !radix_tree_exceptional_entry(entry)) - goto out; + entry = get_unlocked_mapping_entry(mapping, index, &slot); + if (!entry || !radix_tree_exceptional_entry(entry)) { + if (entry) + put_unlocked_mapping_entry(mapping, index, entry); + spin_unlock_irq(&mapping->tree_lock); + return VM_FAULT_NOPAGE; + } radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY); - put_unlocked_mapping_entry(mapping, index, entry); -out: + entry = lock_slot(mapping, slot); spin_unlock_irq(&mapping->tree_lock); + /* + * If we race with somebody updating the PTE and finish_mkwrite_fault() + * fails, we don't care. We need to return VM_FAULT_NOPAGE and retry + * the fault in either case. + */ + finish_mkwrite_fault(vmf); + put_locked_mapping_entry(mapping, index, entry); return VM_FAULT_NOPAGE; } EXPORT_SYMBOL_GPL(dax_pfn_mkwrite); diff --git a/mm/memory.c b/mm/memory.c index e7a4a30a5e88..5fa3d0c5196e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2310,7 +2310,7 @@ static int wp_pfn_shared(struct vm_fault *vmf) pte_unmap_unlock(vmf->pte, vmf->ptl); vmf->flags |= FAULT_FLAG_MKWRITE; ret = vma->vm_ops->pfn_mkwrite(vma, vmf); - if (ret & VM_FAULT_ERROR) + if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)) return ret; return finish_mkwrite_fault(vmf); }