This patch tries to resolve a bug rooted at mm when using nr_cpus. It was reported at [1]. The root cause is: device->numa_node info is used as preferred_nid param for __alloc_pages_nodemask(), which causes NULL reference when ac->zonelist = node_zonelist(preferred_nid, gfp_mask), due to the preferred_nid is not online and not instanced. Hence the bug affects all archs if a machine having a memory less numa-node, but a device on the node is used and provide numa_node info to __alloc_pages_nodemask(). This patch makes all possible node online for ppc. [1]: https://lore.kernel.org/patchwork/patch/1020838/ Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx Cc: x86@xxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> --- Note: [1-2/3] implements one way to fix the bug, while this patch tries another way. Hence using this patch when [1-2/3] is not acceptable. arch/powerpc/mm/numa.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index ce28ae5..31d81a4 100644 --- a/arch/powerpc/mm/numa.c +++ b/arch/powerpc/mm/numa.c @@ -864,10 +864,19 @@ void __init initmem_init(void) memblock_dump_all(); - for_each_online_node(nid) { + /* Instance all possible nodes to overcome potential NULL reference + * issue on node_zonelist() when using nr_cpus + */ + for_each_node(nid) { unsigned long start_pfn, end_pfn; - get_pfn_range_for_nid(nid, &start_pfn, &end_pfn); + if (node_online(nid)) + get_pfn_range_for_nid(nid, &start_pfn, &end_pfn); + else { + start_pfn = end_pfn = 0; + /* online it, so later zonelists[] will be built */ + node_set_online(nid); + } setup_node_data(nid, start_pfn, end_pfn); sparse_memory_present_with_active_regions(nid); } -- 2.7.4
