On Wed, Feb 19, 2020 at 8:34 PM Baoquan He <bhe@xxxxxxxxxx> 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; Looks good to me: Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
