Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755610Ab3HEWZy (ORCPT ); Mon, 5 Aug 2013 18:25:54 -0400 Received: from zene.cmpxchg.org ([85.214.230.12]:51973 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755088Ab3HEWZw (ORCPT ); Mon, 5 Aug 2013 18:25:52 -0400 Date: Mon, 5 Aug 2013 18:25:39 -0400 From: Johannes Weiner To: Andrew Morton Cc: Michal Hocko , David Rientjes , KAMEZAWA Hiroyuki , azurIt , KOSAKI Motohiro , linux-mm@kvack.org, cgroups@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch 3/7] arch: mm: pass userspace fault flag to generic fault handler Message-ID: <20130805222539.GD715@cmpxchg.org> References: <1375549200-19110-1-git-send-email-hannes@cmpxchg.org> <1375549200-19110-4-git-send-email-hannes@cmpxchg.org> <20130805150618.47d699f5ce9f42242ee2e7c3@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130805150618.47d699f5ce9f42242ee2e7c3@linux-foundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2186 Lines: 60 On Mon, Aug 05, 2013 at 03:06:18PM -0700, Andrew Morton wrote: > On Sat, 3 Aug 2013 12:59:56 -0400 Johannes Weiner wrote: > > > Unlike global OOM handling, memory cgroup code will invoke the OOM > > killer in any OOM situation because it has no way of telling faults > > occuring in kernel context - which could be handled more gracefully - > > from user-triggered faults. > > > > Pass a flag that identifies faults originating in user space from the > > architecture-specific fault handlers to generic code so that memcg OOM > > handling can be improved. > > arch/arm64/mm/fault.c has changed. Here's what I came up with: > > --- a/arch/arm64/mm/fault.c~arch-mm-pass-userspace-fault-flag-to-generic-fault-handler > +++ a/arch/arm64/mm/fault.c > @@ -199,13 +199,6 @@ static int __kprobes do_page_fault(unsig > unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC; > unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; > > - if (esr & ESR_LNX_EXEC) { > - vm_flags = VM_EXEC; > - } else if ((esr & ESR_WRITE) && !(esr & ESR_CM)) { > - vm_flags = VM_WRITE; > - mm_flags |= FAULT_FLAG_WRITE; > - } > - > tsk = current; > mm = tsk->mm; > > @@ -220,6 +213,16 @@ static int __kprobes do_page_fault(unsig > if (in_atomic() || !mm) > goto no_context; > > + if (user_mode(regs)) > + mm_flags |= FAULT_FLAG_USER; > + > + if (esr & ESR_LNX_EXEC) { > + vm_flags = VM_EXEC; > + } else if ((esr & ESR_WRITE) && !(esr & ESR_CM)) { > + vm_flags = VM_WRITE; > + mm_flags |= FAULT_FLAG_WRITE; > + } > + > /* > * As per x86, we may deadlock here. However, since the kernel only > * validly references user space from well defined areas of the code, > > But I'm not terribly confident in it. It looks good to me. They added the vm_flags but they are not used any earlier than the mm_flags (__do_page_fault), which I moved to the same location as you did in this fixup. Thanks! -- 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/