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Fri, 4 Oct 2019 09:33:03 +0000 (UTC) Received: from [10.36.117.182] (ovpn-117-182.ams2.redhat.com [10.36.117.182]) by smtp.corp.redhat.com (Postfix) with ESMTP id DAF2F19C5B; Fri, 4 Oct 2019 09:33:00 +0000 (UTC) Subject: Re: [PATCH v5 01/10] mm/memunmap: Use the correct start and end pfn when removing pages from zone From: David Hildenbrand To: "Aneesh Kumar K.V" , 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 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> <6e71cd24-7696-e7ca-15a1-8f126b0860ee@redhat.com> <25a72fa3-9859-3fdb-ffd3-deb7bf154fe0@redhat.com> Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <25a72fa3-9859-3fdb-ffd3-deb7bf154fe0@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Fri, 04 Oct 2019 09:33:04 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 04.10.19 11:03, David Hildenbrand wrote: > On 04.10.19 11:00, David Hildenbrand wrote: >> On 03.10.19 18:48, Aneesh Kumar K.V wrote: >>> 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 init= ializing >>>>>> 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 altm= ap >>>>>> 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 =3D 3669, comm =3D 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_pag= emap *pgmap) >>>>>> void memunmap_pages(struct dev_pagemap *pgmap) >>>>>> { >>>>>> struct resource *res =3D &pgmap->res; >>>>>> - unsigned long pfn; >>>>>> + unsigned long pfn, nr_pages, start_pfn, end_pfn; >>>>>> int nid; >>>>>> =20 >>>>>> dev_pagemap_kill(pgmap); >>>>>> @@ -131,14 +131,17 @@ void memunmap_pages(struct dev_pagemap *pgma= p) >>>>>> put_page(pfn_to_page(pfn)); >>>>>> dev_pagemap_cleanup(pgmap); >>>>>> =20 >>>>>> + start_pfn =3D pfn_first(pgmap); >>>>>> + end_pfn =3D pfn_end(pgmap); >>>>>> + nr_pages =3D end_pfn - start_pfn; >>>>>> + >>>>>> /* pages are dead and unused, undo the arch mapping */ >>>>>> - nid =3D page_to_nid(pfn_to_page(PHYS_PFN(res->start))); >>>>>> + nid =3D page_to_nid(pfn_to_page(start_pfn)); >>>>>> =20 >>>>>> mem_hotplug_begin(); >>>>>> if (pgmap->type =3D=3D MEMORY_DEVICE_PRIVATE) { >>>>>> - pfn =3D 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 i= f 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? >> >> Okay, let's recap. We should call add_pages()/__remove_pages() >> and arch_add_memory()/arch_remove_memory() with the exact same ranges. >> >> So with PHYS_PFN(res->start) and PHYS_PFN(resource_size(res) >> >> Now, only a subset of the pages gets actually initialized, >> meaning the NID and the ZONE we read could be stale. >> That, we have to fix. >> >> What about something like this (am I missing something?): >> >> From d77b5c50f86570819a437517a897cc40ed29eefb Mon Sep 17 00:00:00 2001 >> From: "Aneesh Kumar K.V" >> Date: Fri, 27 Sep 2019 16:02:24 +0530 >> Subject: [PATCH] mm/memunmap: Don't access uninitialized memmap in >> memunmap_pages() >> >> With an altmap, the memmap falling into the reserved altmap space are >> not initialized and, therefore, contain a garbage NID and a garbage >> zone. Make sure to read the NID/zone from a memmap that was initialzed= . >> >> 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 =3D 3669, comm =3D 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+0x1= 74/0x240 >> [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 >> Signed-off-by: Aneesh Kumar K.V >> [ minimze code changes, rephrase description ] >> Signed-off-by: David Hildenbrand >> --- >> mm/memremap.c | 11 +++++++---- >> 1 file changed, 7 insertions(+), 4 deletions(-) >> >> diff --git a/mm/memremap.c b/mm/memremap.c >> index 557e53c6fb46..8b11c0da345c 100644 >> --- a/mm/memremap.c >> +++ b/mm/memremap.c >> @@ -123,6 +123,7 @@ static void dev_pagemap_cleanup(struct dev_pagemap= *pgmap) >> void memunmap_pages(struct dev_pagemap *pgmap) >> { >> struct resource *res =3D &pgmap->res; >> + struct page *first_page; >> unsigned long pfn; >> int nid; >> =20 >> @@ -131,14 +132,16 @@ void memunmap_pages(struct dev_pagemap *pgmap) >> put_page(pfn_to_page(pfn)); >> dev_pagemap_cleanup(pgmap); >> =20 >> + /* make sure to access a memmap that was actually initialized */ >> + first_page =3D pfn_to_page(pfn_first(pgmap)); >> + >> /* pages are dead and unused, undo the arch mapping */ >> - nid =3D page_to_nid(pfn_to_page(PHYS_PFN(res->start))); >> + nid =3D page_to_nid(first_page); >> =20 >> mem_hotplug_begin(); >> if (pgmap->type =3D=3D MEMORY_DEVICE_PRIVATE) { >> - pfn =3D PHYS_PFN(res->start); >> - __remove_pages(page_zone(pfn_to_page(pfn)), pfn, >> - PHYS_PFN(resource_size(res)), NULL); >> + __remove_pages(page_zone(first_page), res->start, >> + resource_size(res), NULL); >=20 > Keeping the PHYS_PFN() calls of course ... >=20 >> } else { >> arch_remove_memory(nid, res->start, resource_size(res), >> pgmap_altmap(pgmap)); >> >=20 >=20 The current state (with the modified patch) can be found at: https://github.com/davidhildenbrand/linux/tree/zone_offline @Aneesh, It would be great if you could test the namespace removal thingy and tell me if we are still missing something :) --=20 Thanks, David / dhildenb