On 27.09.19 12:32, Aneesh Kumar K.V wrote: > 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 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 > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx> > --- > Note: > This patch alone won't fix all the kernel crashes related wrong usage of pfn. > For ndctl destroy-namespace to work correctly we need rest of patches from > the series posted at > > https://lore.kernel.org/linux-mm/20190830091428.18399-1-david@xxxxxxxxxx > > mm/memremap.c | 14 +++++++++----- > 1 file changed, 9 insertions(+), 5 deletions(-) > > diff --git a/mm/memremap.c b/mm/memremap.c > index 32c79b51af86..4b31f0b7c42d 100644 > --- a/mm/memremap.c > +++ b/mm/memremap.c > @@ -105,7 +105,8 @@ 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 start_pfn, end_pfn; > + unsigned long pfn, nr_pages; pack all into a single line? > int nid; > > dev_pagemap_kill(pgmap); > @@ -113,14 +114,17 @@ 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)); > I am no expert on the details of the whole pgmap, what-to-add-what-to-initialize-whatsoever devmem specific stuff, but this change looks sane to me as far as I can tell. -- Thanks, David / dhildenb
