Changes from v1: 1. Trim the verbose oops in the commit message. (feedbacked by Phil Auld) 2. Rewrite a comment in code. (feedbacked by Phil Auld) --->8--- >From 6830b59db267a31b78f6f09af12ae0e3132b4bca Mon Sep 17 00:00:00 2001 From: Byungchul Park <byungchul@xxxxxx> Date: Fri, 16 Feb 2024 16:26:23 +0900 Subject: [PATCH v2] sched/numa, mm: do not promote folios to nodes not set N_MEMORY While running qemu with a configuration where some CPUs don't have their local memory and with a kernel numa balancing on, the following oops has been observed. It's because of null pointers of ->zone_pgdat of zones of those nodes that are not initialized properly at booting time. So should avoid nodes not set N_MEMORY from getting promoted. > BUG: unable to handle page fault for address: 00000000000033f3 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: 0000 [#1] PREEMPT SMP NOPTI > CPU: 2 PID: 895 Comm: masim Not tainted 6.6.0-dirty #255 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 > RIP: 0010:wakeup_kswapd (./linux/mm/vmscan.c:7812) > Code: (omitted) > RSP: 0000:ffffc90004257d58 EFLAGS: 00010286 > RAX: ffffffffffffffff RBX: ffff88883fff0480 RCX: 0000000000000003 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88883fff0480 > RBP: ffffffffffffffff R08: ff0003ffffffffff R09: ffffffffffffffff > R10: ffff888106c95540 R11: 0000000055555554 R12: 0000000000000003 > R13: 0000000000000000 R14: 0000000000000000 R15: ffff88883fff0940 > FS: 00007fc4b8124740(0000) GS:ffff888827c00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00000000000033f3 CR3: 000000026cc08004 CR4: 0000000000770ee0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > PKRU: 55555554 > Call Trace: > <TASK> > ? __die > ? page_fault_oops > ? __pte_offset_map_lock > ? exc_page_fault > ? asm_exc_page_fault > ? wakeup_kswapd > migrate_misplaced_page > __handle_mm_fault > handle_mm_fault > do_user_addr_fault > exc_page_fault > asm_exc_page_fault > RIP: 0033:0x55b897ba0808 > Code: (omitted) > RSP: 002b:00007ffeefa821a0 EFLAGS: 00010287 > RAX: 000055b89983acd0 RBX: 00007ffeefa823f8 RCX: 000055b89983acd0 > RDX: 00007fc2f8122010 RSI: 0000000000020000 RDI: 000055b89983acd0 > RBP: 00007ffeefa821a0 R08: 0000000000000037 R09: 0000000000000075 > R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 > R13: 00007ffeefa82410 R14: 000055b897ba5dd8 R15: 00007fc4b8340000 > </TASK> Signed-off-by: Byungchul Park <byungchul@xxxxxx> Reported-by: Hyeongtak Ji <hyeongtak.ji@xxxxxx> --- kernel/sched/fair.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d7a3c63a2171..859ef78ef72b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1828,6 +1828,15 @@ bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio, int dst_nid = cpu_to_node(dst_cpu); int last_cpupid, this_cpupid; + /* + * A node of dst_nid might not have its local memory. Promoting + * a folio to the node is meaningless. What's even worse, oops + * can be observed by the null pointer of ->zone_pgdat in + * various points of the code during migration. + */ + if (!node_state(dst_nid, N_MEMORY)) + return false; + /* * The pages in slow memory node should be migrated according * to hot/cold instead of private/shared. -- 2.17.1
