Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752170AbbHELnN (ORCPT ); Wed, 5 Aug 2015 07:43:13 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:34593 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752110AbbHELnL (ORCPT ); Wed, 5 Aug 2015 07:43:11 -0400 Date: Wed, 5 Aug 2015 14:43:09 +0300 From: "Kirill A. Shutemov" To: Matthew Wilcox Cc: Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox Subject: Re: [PATCH 06/11] dax: Fix race between simultaneous faults Message-ID: <20150805114309.GA25784@node.dhcp.inet.fi> References: <1438718285-21168-1-git-send-email-matthew.r.wilcox@intel.com> <1438718285-21168-7-git-send-email-matthew.r.wilcox@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1438718285-21168-7-git-send-email-matthew.r.wilcox@intel.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1221 Lines: 35 On Tue, Aug 04, 2015 at 03:58:00PM -0400, Matthew Wilcox wrote: > diff --git a/mm/memory.c b/mm/memory.c > index b94b587..5f46350 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2426,11 +2426,16 @@ void unmap_mapping_range(struct address_space *mapping, > details.last_index = ULONG_MAX; > > > - /* DAX uses i_mmap_lock to serialise file truncate vs page fault */ > - i_mmap_lock_write(mapping); > + /* > + * DAX already holds i_mmap_lock to serialise file truncate vs > + * page fault and page fault vs page fault. > + */ > + if (!IS_DAX(mapping->host)) > + i_mmap_lock_write(mapping); > if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap))) > unmap_mapping_range_tree(&mapping->i_mmap, &details); > - i_mmap_unlock_write(mapping); > + if (!IS_DAX(mapping->host)) > + i_mmap_unlock_write(mapping); > } > EXPORT_SYMBOL(unmap_mapping_range); Huh? What protects mapping->i_mmap here? I don't see anything up by stack taking the lock. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/