From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f177.google.com (mail-wi0-f177.google.com [209.85.212.177]) by kanga.kvack.org (Postfix) with ESMTP id C8E106B0032 for ; Tue, 17 Mar 2015 15:24:28 -0400 (EDT) Received: by wibg7 with SMTP id g7so71667371wib.1 for ; Tue, 17 Mar 2015 12:24:28 -0700 (PDT) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id ey12si4777005wid.77.2015.03.17.12.24.26 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 17 Mar 2015 12:24:27 -0700 (PDT) Date: Tue, 17 Mar 2015 15:24:13 -0400 From: Johannes Weiner 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: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Huang Ying , Michal Hocko , Tetsuo Handa , David Rientjes , Andrew Morton , Dave Chinner , LKML , LKP ML , linux-mm 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 -- 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