From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752210AbbIQPrV (ORCPT ); Thu, 17 Sep 2015 11:47:21 -0400 Received: from mga09.intel.com ([134.134.136.24]:53642 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751418AbbIQPrT (ORCPT ); Thu, 17 Sep 2015 11:47:19 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,547,1437462000"; d="scan'208";a="807367056" From: "Kirill A. Shutemov" To: Ross Zwisler Cc: "Kirill A. Shutemov" , Matthew Wilcox , Dan Williams , "Kirill A. Shutemov" , Andrew Morton , linux-mm@kvack.org, linux-fsdevel , Linux Kernel Mailing List , "linux-nvdimm@lists.01.org" , ross.zwisler@linux.intel.com In-Reply-To: <20150917154131.GA27791@linux.intel.com> References: <1438948423-128882-1-git-send-email-kirill.shutemov@linux.intel.com> <20150916111218.GB23026@node.dhcp.inet.fi> <20150917154131.GA27791@linux.intel.com> Subject: Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX Content-Transfer-Encoding: 7bit Message-Id: <20150917154715.7A857B8@black.fi.intel.com> Date: Thu, 17 Sep 2015 18:47:15 +0300 (EEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ross Zwisler wrote: > On Wed, Sep 16, 2015 at 02:12:18PM +0300, Kirill A. Shutemov wrote: > > On Tue, Sep 15, 2015 at 04:52:42PM -0700, Dan Williams wrote: > > > Hi Kirill, > > > > > > On Fri, Aug 7, 2015 at 4:53 AM, Kirill A. Shutemov > > > wrote: > > > > DAX is not so special: we need i_mmap_lock to protect mapping->i_mmap. > > > > > > > > __dax_pmd_fault() uses unmap_mapping_range() shoot out zero page from > > > > all mappings. We need to drop i_mmap_lock there to avoid lock deadlock. > > > > > > > > Re-aquiring the lock should be fine since we check i_size after the > > > > point. > > > > > > > > Not-yet-signed-off-by: Matthew Wilcox > > > > Signed-off-by: Kirill A. Shutemov > > > > --- > > > > fs/dax.c | 35 +++++++++++++++++++---------------- > > > > mm/memory.c | 11 ++--------- > > > > 2 files changed, 21 insertions(+), 25 deletions(-) > > > > > > > > diff --git a/fs/dax.c b/fs/dax.c > > > > index 9ef9b80cc132..ed54efedade6 100644 > > > > --- a/fs/dax.c > > > > +++ b/fs/dax.c > > > > @@ -554,6 +554,25 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, > > > > if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) > > > > goto fallback; > > > > > > > > + if (buffer_unwritten(&bh) || buffer_new(&bh)) { > > > > + int i; > > > > + for (i = 0; i < PTRS_PER_PMD; i++) > > > > + clear_page(kaddr + i * PAGE_SIZE); > > > > > > This patch, now upstream as commit 46c043ede471, moves the call to > > > clear_page() earlier in __dax_pmd_fault(). However, 'kaddr' is not > > > set at this point, so I'm not sure this path was ever tested. > > > > Ughh. It's obviously broken. > > > > I took fs/dax.c part of the patch from Matthew. And I'm not sure now we > > would need to move this "if (buffer_unwritten(&bh) || buffer_new(&bh)) {" > > block around. It should work fine where it was before. Right? > > Matthew? > > Moving the "if (buffer_unwritten(&bh) || buffer_new(&bh)) {" block back seems > correct to me. Matthew is out for a while, so we should probably take care of > this without him. > > Kirill, do you want to whip up a quick patch? I'm happy to do it if you're > busy. I would be better if you'll prepare the patch. Thanks. -- Kirill