From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga04.intel.com ([192.55.52.120]:34003 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727778AbgD3Tcc (ORCPT ); Thu, 30 Apr 2020 15:32:32 -0400 From: Dave Hansen Subject: Re: [PATCH v1 1/1] fs/splice: add missing callback for inaccessible pages References: <20200428225043.3091359-1-imbrenda@linux.ibm.com> <2a1abf38-d321-e3c7-c3b1-53b6db6da310@intel.com> Message-ID: <540f483f-5e58-f342-e771-9d90c4d3fb6a@intel.com> Date: Thu, 30 Apr 2020 12:32:31 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Christian Borntraeger , Claudio Imbrenda , akpm@linux-foundation.org, jack@suse.cz, kirill@shutemov.name Cc: david@redhat.com, aarcange@redhat.com, linux-mm@kvack.org, frankja@linux.ibm.com, sfr@canb.auug.org.au, jhubbard@nvidia.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, peterz@infradead.org, sean.j.christopherson@intel.com On 4/30/20 11:12 AM, Christian Borntraeger wrote: > On 29.04.20 18:07, Dave Hansen wrote: >> On 4/28/20 3:50 PM, Claudio Imbrenda wrote: >>> If a page is inaccesible and it is used for things like sendfile, then >>> the content of the page is not always touched, and can be passed >>> directly to a driver, causing issues. >>> >>> This patch fixes the issue by adding a call to arch_make_page_accessible >>> in page_cache_pipe_buf_confirm; this fixes the issue. >> I spent about 5 minutes putting together a patch: >> >> https://sr71.net/~dave/intel/accessible.patch > You only set the page flag for compound pages. that of course leaves a big pile > of pages marked a not accessible, thus explaining the sendto trace and all kind > of other random traces. Ahh, nice catch! That does explain an oddity or two that I saw. > What do you see when you also do the SetPageAccessible(page); > in the else page of prep_new_page (order == 0). > (I do get > 10000 of these non compound page allocs just during boot). Yes, I see the same thing. I updated the patch and double-checked that it triggers properly with a socket-based sendfile().