From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f50.google.com (mail-pa0-f50.google.com [209.85.220.50]) by kanga.kvack.org (Postfix) with ESMTP id BA0446B0255 for ; Thu, 17 Sep 2015 11:41:33 -0400 (EDT) Received: by padhy16 with SMTP id hy16so23020500pad.1 for ; Thu, 17 Sep 2015 08:41:33 -0700 (PDT) Received: from mga03.intel.com (mga03.intel.com. [134.134.136.65]) by mx.google.com with ESMTP id rm9si6137743pab.83.2015.09.17.08.41.32 for ; Thu, 17 Sep 2015 08:41:33 -0700 (PDT) Date: Thu, 17 Sep 2015 09:41:31 -0600 From: Ross Zwisler Subject: Re: [PATCH] mm: take i_mmap_lock in unmap_mapping_range() for DAX Message-ID: <20150917154131.GA27791@linux.intel.com> References: <1438948423-128882-1-git-send-email-kirill.shutemov@linux.intel.com> <20150916111218.GB23026@node.dhcp.inet.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150916111218.GB23026@node.dhcp.inet.fi> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: 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 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. -- 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