From patchwork Wed Mar 4 16:41:48 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Boaz Harrosh X-Patchwork-Id: 5938351 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id DD1B69F380 for ; Wed, 4 Mar 2015 16:42:00 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id EE4C7201F5 for ; Wed, 4 Mar 2015 16:41:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C7B9720123 for ; Wed, 4 Mar 2015 16:41:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933548AbbCDQl4 (ORCPT ); Wed, 4 Mar 2015 11:41:56 -0500 Received: from mail-we0-f169.google.com ([74.125.82.169]:36309 "EHLO mail-we0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933268AbbCDQly (ORCPT ); Wed, 4 Mar 2015 11:41:54 -0500 Received: by wesq59 with SMTP id q59so10586118wes.3 for ; Wed, 04 Mar 2015 08:41:53 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :subject:references:in-reply-to:content-type :content-transfer-encoding; bh=KSonZ4qmqT4TUoUXV4QYQjsfXtjPVZYiWR2st6vAFs8=; b=PAsdeE9jdzRJIBpW7tdCMQ31tAXb7aliFqqP7WQcFpsVhcdjIQwx290DjErAGEE2Ud 1P5xlA/N6lxZMdxRafaHFA/BH9477pMiQkjaMpoPyzIWfH0j5kaX6pAX/InctuRJN3jU 2zftE3/H2NFoe8bo14I+U40DP88//fo3sHBv+LpA2SwCopUsOLEORGxZzRI0202a3xEA hAtXqIZ+D1DtXX8mJrKaZP3JuevClXL5wb8Ht8raiRIRd0AUjMfXe19+kylF497nc9tk 7SVqMvN/7joMmDFFEa7Z6hBtnXuL6d8z0ltt7rpuoniiw/1d3o9dwhALEIYhQLq/tSN9 eHmQ== X-Gm-Message-State: ALoCoQnpVVrYQDKxjIM8j5F4kl0Hyq1qeQTpFnD+4UeNP4gftV+yW3oDsv7eS3lteSD7RrFTDiyy X-Received: by 10.181.12.105 with SMTP id ep9mr57919817wid.85.1425487313402; Wed, 04 Mar 2015 08:41:53 -0800 (PST) Received: from [10.0.0.5] ([207.232.55.62]) by mx.google.com with ESMTPSA id k6sm25915857wia.6.2015.03.04.08.41.49 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 04 Mar 2015 08:41:52 -0800 (PST) Message-ID: <54F735CC.4010608@plexistor.com> Date: Wed, 04 Mar 2015 18:41:48 +0200 From: Boaz Harrosh User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Dave Chinner , Matthew Wilcox , Andrew Morton , "Kirill A. Shutemov" , Jan Kara , Hugh Dickins , Mel Gorman , linux-mm@kvack.org, linux-nvdimm , linux-fsdevel Subject: [PATCH 2/3] mm: New pfn_mkwrite same as page_mkwrite for VM_PFNMAP References: <54F733BD.7060807@plexistor.com> In-Reply-To: <54F733BD.7060807@plexistor.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Yigal Korman This will allow FS that uses VM_PFNMAP | VM_MIXEDMAP (no page structs) to get notified when access is a write to a read-only PFN. This can happen if we mmap() a file then first mmap-read from it to page-in a read-only PFN, than we mmap-write to the same page. We need this functionality to fix a DAX bug, where in the scenario above we fail to set ctime/mtime though we modified the file. An xfstest is attached to this patchset that shows the failure and the fix. (A DAX patch will follow) This functionality is extra important for us, because upon dirtying of a pmem page we also want to RDMA the page to a remote cluster node. We define a new pfn_mkwrite and do not reuse page_mkwrite because 1 - The name ;-) 2 - But mainly because it would take a very long and tedious audit of all page_mkwrite functions of VM_MIXEDMAP/VM_PFNMAP users. To make sure they do not now CRASH. For example current DAX code (which this is for) would crash. If we would want to reuse page_mkwrite, We will need to first patch all users, so to not-crash-on-no-page. Then enable this patch. But even if I did that I would not sleep so well at night. Adding a new vector is the safest thing to do, and is not that expensive. an extra pointer at a static function vector per driver. Also the new vector is better for performance, because else we Will call all current Kernel vectors, so to: check-ha-no-page-do-nothing and return. No need to call it from do_shared_fault because do_wp_page is called to change pte permissions anyway. CC: Matthew Wilcox CC: Kirill A. Shutemov CC: Jan Kara CC: Andrew Morton CC: Hugh Dickins CC: Mel Gorman CC: linux-mm@kvack.org Signed-off-by: Yigal Korman Signed-off-by: Boaz Harrosh --- include/linux/mm.h | 2 ++ mm/memory.c | 27 ++++++++++++++++++++++++++- 2 files changed, 28 insertions(+), 1 deletion(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 47a9392..1cd820c 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -250,6 +250,8 @@ struct vm_operations_struct { /* notification that a previously read-only page is about to become * writable, if an error is returned it will cause a SIGBUS */ int (*page_mkwrite)(struct vm_area_struct *vma, struct vm_fault *vmf); + /* same as page_mkwrite when using VM_PFNMAP|VM_MIXEDMAP */ + int (*pfn_mkwrite)(struct vm_area_struct *vma, struct vm_fault *vmf); /* called by access_process_vm when get_user_pages() fails, typically * for use by special VMAs that can switch between memory and hardware diff --git a/mm/memory.c b/mm/memory.c index 8068893..ebef8f6 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1982,6 +1982,22 @@ static int do_page_mkwrite(struct vm_area_struct *vma, struct page *page, return ret; } +static int do_pfn_mkwrite(struct vm_area_struct *vma, unsigned long address) +{ + struct vm_fault vmf; + + if (!vma->vm_ops || !vma->vm_ops->pfn_mkwrite) + return 0; + + vmf.page = 0; + vmf.pgoff = (((address & PAGE_MASK) - vma->vm_start) >> PAGE_SHIFT) + + vma->vm_pgoff; + vmf.virtual_address = (void __user *)(address & PAGE_MASK); + vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE; + + return vma->vm_ops->pfn_mkwrite(vma, &vmf); +} + /* * This routine handles present pages, when users try to write * to a shared page. It is done by copying the page to a new address @@ -2025,8 +2041,17 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, * accounting on raw pfn maps. */ if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) == - (VM_WRITE|VM_SHARED)) + (VM_WRITE|VM_SHARED)) { + pte_unmap_unlock(page_table, ptl); + ret = do_pfn_mkwrite(vma, address); + if (ret & VM_FAULT_ERROR) + return ret; + page_table = pte_offset_map_lock(mm, pmd, address, + &ptl); + if (!pte_same(*page_table, orig_pte)) + goto unlock; goto reuse; + } goto gotten; }