From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f179.google.com (mail-wi0-f179.google.com [209.85.212.179]) by kanga.kvack.org (Postfix) with ESMTP id 452F36B0254 for ; Tue, 1 Sep 2015 07:22:00 -0400 (EDT) Received: by wicfx3 with SMTP id fx3so8761903wic.0 for ; Tue, 01 Sep 2015 04:21:59 -0700 (PDT) Received: from mail-wi0-f173.google.com (mail-wi0-f173.google.com. [209.85.212.173]) by mx.google.com with ESMTPS id b19si2632321wiw.16.2015.09.01.04.21.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 01 Sep 2015 04:21:59 -0700 (PDT) Received: by wicge5 with SMTP id ge5so3409051wic.0 for ; Tue, 01 Sep 2015 04:21:58 -0700 (PDT) Message-ID: <55E58A54.8040805@plexistor.com> Date: Tue, 01 Sep 2015 14:21:56 +0300 From: Boaz Harrosh MIME-Version: 1.0 Subject: Re: [PATCH] mm, dax: VMA with vm_ops->pfn_mkwrite wants to be write-notified References: <1441102961-68041-1-git-send-email-kirill.shutemov@linux.intel.com> <55E583E2.9000200@plexistor.com> <20150901111020.GA7820@node.dhcp.inet.fi> In-Reply-To: <20150901111020.GA7820@node.dhcp.inet.fi> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Andrew Morton , Matthew Wilcox , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, Yigal Korman , Jan Kara , Dave Chinner On 09/01/2015 02:10 PM, Kirill A. Shutemov wrote: > On Tue, Sep 01, 2015 at 01:54:26PM +0300, Boaz Harrosh wrote: >> On 09/01/2015 01:22 PM, Kirill A. Shutemov wrote: >>> For VM_PFNMAP and VM_MIXEDMAP we use vm_ops->pfn_mkwrite instead of >>> vm_ops->page_mkwrite to notify abort write access. This means we want >>> vma->vm_page_prot to be write-protected if the VMA provides this vm_ops. >>> >> >> Hi Kirill >> >> I will test with this right away and ACK on this. >> >> Hmm so are you saying we might be missing some buffer modifications right now. >> >> What would be a theoretical scenario that will cause these missed events? > > On writable mapping with vm_ops->pfn_mkwrite, but without > vm_ops->page_mkwrite: read fault followed by write access to the pfn. > Writable pte will be set up on read fault and write fault will not be > generated. > > I found it examining Dave's complain on generic/080: > > http://lkml.kernel.org/g/20150831233803.GO3902@dastard > > Although I don't think it's the reason. > >> I would like to put a test in our test rigs that should fail today and this >> patch fixes. >> >> [In our system every modified pmem block is also RDMAed to a remote >> pmem for HA, a missed modification will make the two copies unsynced] > > It shouldn't be a problem for ext2/ext4 as they provide both pfn_mkwrite > and page_mkwrite. > Ha right we have both as well, and so should xfs I think (because of the zero pages thing, in fact any dax.c user should). Thanks so this verifies why we could not see any such breakage. ACK-by: Boaz Harrosh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org