Re: [PATCH v2] sched/numa, mm: do not promote folios to nodes not set N_MEMORY

[Byungchul Park]

On Fri, Feb 16, 2024 at 10:07:53AM +0100, David Hildenbrand wrote:
> On 16.02.24 08:33, Byungchul Park wrote:
> > 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>
> > 
> 
> This sounds like we need a Fixes: and want to CC stable?

Sure. I will CC stable at the next spin - might need to rewrite the
reason.

	Byungchul

> -- 
> Cheers,
> 
> David / dhildenb