From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932229AbbCQTY1 (ORCPT ); Tue, 17 Mar 2015 15:24:27 -0400 Received: from gum.cmpxchg.org ([85.214.110.215]:49990 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932093AbbCQTY0 (ORCPT ); Tue, 17 Mar 2015 15:24:26 -0400 Date: Tue, 17 Mar 2015 15:24:13 -0400 From: Johannes Weiner To: Linus Torvalds Cc: Huang Ying , Michal Hocko , Tetsuo Handa , David Rientjes , Andrew Morton , Dave Chinner , LKML , LKP ML , linux-mm Subject: Re: [LKP] [mm] cc87317726f: WARNING: CPU: 0 PID: 1 at drivers/iommu/io-pgtable-arm.c:413 __arm_lpae_unmap+0x341/0x380() Message-ID: <20150317192413.GA7772@phnom.home.cmpxchg.org> References: <1426227621.6711.238.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 17, 2015 at 10:15:29AM -0700, Linus Torvalds wrote: > Explicitly adding the emails of other people involved with that commit > and the original oom thread to make sure people are aware, since this > didn't get any response. > > Commit cc87317726f8 fixed some behavior, but also seems to have turned > an oom situation into a complete hang. So presumably we shouldn't loop > *forever*. Hmm? It seems we are between a rock and a hard place here, as we reverted specifically to that endless looping on request of filesystem people. They said[1] they rely on these allocations never returning NULL, or they might fail inside a transactions and corrupt on-disk data. Huang, against which kernels did you first run this test on this exact setup? Is there a chance you could try to run a kernel without/before 9879de7373fc? I want to make sure I'm not missing something, but all versions preceding this commit should also have the same hang. There should only be a tiny window between 9879de7373fc and cc87317726f8 -- v3.19 -- where these allocations are allowed to fail. [1] https://www.marc.info/?l=linux-mm&m=142450545009301&w=3