On 03/03/20 at 09:34am, David Hildenbrand wrote: > On 20.02.20 05:33, Baoquan He wrote: > > In section_deactivate(), pfn_to_page() doesn't work any more after > > ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. > > It caused hot remove failure: > > > > kernel BUG at mm/page_alloc.c:4806! > > invalid opcode: 0000 [#1] SMP PTI > > CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G W 5.5.0-next-20200205+ #340 > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 > > Workqueue: kacpi_hotplug acpi_hotplug_work_fn > > RIP: 0010:free_pages+0x85/0xa0 > > Call Trace: > > __remove_pages+0x99/0xc0 > > arch_remove_memory+0x23/0x4d > > try_remove_memory+0xc8/0x130 > > ? walk_memory_blocks+0x72/0xa0 > > __remove_memory+0xa/0x11 > > acpi_memory_device_remove+0x72/0x100 > > acpi_bus_trim+0x55/0x90 > > acpi_device_hotplug+0x2eb/0x3d0 > > acpi_hotplug_work_fn+0x1a/0x30 > > process_one_work+0x1a7/0x370 > > worker_thread+0x30/0x380 > > ? flush_rcu_work+0x30/0x30 > > kthread+0x112/0x130 > > ? kthread_create_on_node+0x60/0x60 > > ret_from_fork+0x35/0x40 > > > > Let's move the ->section_mem_map resetting after depopulate_section_memmap() > > to fix it. > > > > Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> > > --- > > mm/sparse.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/mm/sparse.c b/mm/sparse.c > > index 596b2a45b100..b8e52c8fed7f 100644 > > --- a/mm/sparse.c > > +++ b/mm/sparse.c > > @@ -779,13 +779,15 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, > > ms->usage = NULL; > > } > > memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr); > > - ms->section_mem_map = (unsigned long)NULL; > > } > > > > if (section_is_early && memmap) > > free_map_bootmem(memmap); > > else > > depopulate_section_memmap(pfn, nr_pages, altmap); > > + > > + if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) > > + ms->section_mem_map = (unsigned long)NULL; > > } > > > > static struct page * __meminit section_activate(int nid, unsigned long pfn, > > > > As discussed, I think this is broken here already. As you explained, the > subsection_map can get freed via kfree(ms->usage) after the first > bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION) check. Yes, I will correct it as you suggested in another reply.
