From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH v1 1/1] fs/splice: add missing callback for inaccessible pages From: Christian Borntraeger References: <20200428225043.3091359-1-imbrenda@linux.ibm.com> <2a1abf38-d321-e3c7-c3b1-53b6db6da310@intel.com> Message-ID: <4b32c162-6ea4-ba91-b6d5-8961b7dff6e8@de.ibm.com> Date: Thu, 30 Apr 2020 21:02:21 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: To: Dave Hansen , 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, Ulrich Weigand On 30.04.20 20:12, 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. > > > 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). > And yes, I think you are right that we should call the callback also for !FOLL_PIN.