From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:27952 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405711AbfJCQsk (ORCPT ); Thu, 3 Oct 2019 12:48:40 -0400 Subject: Re: [PATCH v5 01/10] mm/memunmap: Use the correct start and end pfn when removing pages from zone References: <20191001144011.3801-1-david@redhat.com> <20191001144011.3801-2-david@redhat.com> <933f9cd8-9a32-8566-bd97-7e475a009275@redhat.com> <09b61ab1-6099-d825-8e04-fbfb43abe4d2@redhat.com> From: "Aneesh Kumar K.V" Message-ID: Date: Thu, 3 Oct 2019 22:18:10 +0530 MIME-Version: 1.0 In-Reply-To: <09b61ab1-6099-d825-8e04-fbfb43abe4d2@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: David Hildenbrand , linux-kernel@vger.kernel.org, Dan Williams Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, Andrew Morton , Jason Gunthorpe , Logan Gunthorpe , Ira Weiny , Pankaj Gupta On 10/1/19 8:33 PM, David Hildenbrand wrote: > On 01.10.19 16:57, David Hildenbrand wrote: >> On 01.10.19 16:40, David Hildenbrand wrote: >>> From: "Aneesh Kumar K.V" >>> >>> With altmap, all the resource pfns are not initialized. While initializing >>> pfn, altmap reserve space is skipped. Hence when removing pfn from zone >>> skip pfns that were never initialized. >>> >>> Update memunmap_pages to calculate start and end pfn based on altmap >>> values. This fixes a kernel crash that is observed when destroying >>> a namespace. >>> >>> [ 81.356173] kernel BUG at include/linux/mm.h:1107! >>> cpu 0x1: Vector: 700 (Program Check) at [c000000274087890] >>> pc: c0000000004b9728: memunmap_pages+0x238/0x340 >>> lr: c0000000004b9724: memunmap_pages+0x234/0x340 >>> ... >>> pid = 3669, comm = ndctl >>> kernel BUG at include/linux/mm.h:1107! >>> [c000000274087ba0] c0000000009e3500 devm_action_release+0x30/0x50 >>> [c000000274087bc0] c0000000009e4758 release_nodes+0x268/0x2d0 >>> [c000000274087c30] c0000000009dd144 device_release_driver_internal+0x174/0x240 >>> [c000000274087c70] c0000000009d9dfc unbind_store+0x13c/0x190 >>> [c000000274087cb0] c0000000009d8a24 drv_attr_store+0x44/0x60 >>> [c000000274087cd0] c0000000005a7470 sysfs_kf_write+0x70/0xa0 >>> [c000000274087d10] c0000000005a5cac kernfs_fop_write+0x1ac/0x290 >>> [c000000274087d60] c0000000004be45c __vfs_write+0x3c/0x70 >>> [c000000274087d80] c0000000004c26e4 vfs_write+0xe4/0x200 >>> [c000000274087dd0] c0000000004c2a6c ksys_write+0x7c/0x140 >>> [c000000274087e20] c00000000000bbd0 system_call+0x5c/0x68 >>> >>> Cc: Dan Williams >>> Cc: Andrew Morton >>> Cc: Jason Gunthorpe >>> Cc: Logan Gunthorpe >>> Cc: Ira Weiny >>> Reviewed-by: Pankaj Gupta >>> Signed-off-by: Aneesh Kumar K.V >>> [ move all pfn-realted declarations into a single line ] >>> Signed-off-by: David Hildenbrand >>> --- >>> mm/memremap.c | 13 ++++++++----- >>> 1 file changed, 8 insertions(+), 5 deletions(-) >>> >>> diff --git a/mm/memremap.c b/mm/memremap.c >>> index 557e53c6fb46..026788b2ac69 100644 >>> --- a/mm/memremap.c >>> +++ b/mm/memremap.c >>> @@ -123,7 +123,7 @@ static void dev_pagemap_cleanup(struct dev_pagemap *pgmap) >>> void memunmap_pages(struct dev_pagemap *pgmap) >>> { >>> struct resource *res = &pgmap->res; >>> - unsigned long pfn; >>> + unsigned long pfn, nr_pages, start_pfn, end_pfn; >>> int nid; >>> >>> dev_pagemap_kill(pgmap); >>> @@ -131,14 +131,17 @@ void memunmap_pages(struct dev_pagemap *pgmap) >>> put_page(pfn_to_page(pfn)); >>> dev_pagemap_cleanup(pgmap); >>> >>> + start_pfn = pfn_first(pgmap); >>> + end_pfn = pfn_end(pgmap); >>> + nr_pages = end_pfn - start_pfn; >>> + >>> /* pages are dead and unused, undo the arch mapping */ >>> - nid = page_to_nid(pfn_to_page(PHYS_PFN(res->start))); >>> + nid = page_to_nid(pfn_to_page(start_pfn)); >>> >>> mem_hotplug_begin(); >>> if (pgmap->type == MEMORY_DEVICE_PRIVATE) { >>> - pfn = PHYS_PFN(res->start); >>> - __remove_pages(page_zone(pfn_to_page(pfn)), pfn, >>> - PHYS_PFN(resource_size(res)), NULL); >>> + __remove_pages(page_zone(pfn_to_page(start_pfn)), start_pfn, >>> + nr_pages, NULL); >>> } else { >>> arch_remove_memory(nid, res->start, resource_size(res), >>> pgmap_altmap(pgmap)); >>> >> >> Aneesh, I was wondering why the use of "res->start" is correct (and we >> shouldn't also witch to start_pfn/nr_pages here. It would be good if Dan >> could review. >> > > To be more precise, I wonder if it should actually be > > __remove_pages(page_zone(pfn_to_page(start_pfn)), res->start, > resource_size(res)) > yes, that would be make it much clear. But for MEMORY_DEVICE_PRIVATE start_pfn and pfn should be same? > IOW, keep calling __remove_pages() with the same parameters but read > nid/zone from the offset one. > > Hope some memunmap_pages() expert can clarify. > -aneesh