Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756504AbcDNRj1 (ORCPT ); Thu, 14 Apr 2016 13:39:27 -0400 Received: from mga01.intel.com ([192.55.52.88]:31236 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755365AbcDNRj0 (ORCPT ); Thu, 14 Apr 2016 13:39:26 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,485,1455004800"; d="scan'208";a="785001566" Date: Thu, 14 Apr 2016 13:39:22 -0400 From: Matthew Wilcox To: Hugh Dickins Cc: Andrew Morton , "Kirill A. Shutemov" , Andrea Arcangeli , Andres Lagar-Cavilla , Yang Shi , Ning Qu , David Rientjes , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 09/10] huge pagecache: mmap_sem is unlocked when truncation splits pmd Message-ID: <20160414173922.GE3120@linux.intel.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 478 Lines: 10 On Tue, Apr 05, 2016 at 01:55:23PM -0700, Hugh Dickins wrote: > zap_pmd_range()'s CONFIG_DEBUG_VM !rwsem_is_locked(&mmap_sem) BUG() > will be invalid with huge pagecache, in whatever way it is implemented: > truncation of a hugely-mapped file to an unhugely-aligned size would > easily hit it. We can reproduce this BUG() in the current Linus tree with DAX PMDs. Andrew, can you send this patch to Linus for inclusion in 4.7? Tested-by: Matthew Wilcox