[5.6.0-rc2-next-20200218/powerpc] Boot failure on POWER9

[Sachin Sant]

Todays next fails to boot on a POWER9 PowerVM logical partition
with following trace:

[    8.767660] random: systemd: uninitialized urandom read (16 bytes read)
[    8.768629] BUG: Kernel NULL pointer dereference on read at 0x000073b0
[    8.768635] Faulting instruction address: 0xc0000000003d55f4
[    8.768641] Oops: Kernel access of bad area, sig: 11 [#1]
[    8.768645] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[    8.768650] Modules linked in:
[    8.768655] CPU: 19 PID: 1 Comm: systemd Not tainted 5.6.0-rc2-next-20200218-autotest #1
[    8.768660] NIP:  c0000000003d55f4 LR: c0000000003d5b94 CTR: 0000000000000000
[    8.768666] REGS: c0000008b37836d0 TRAP: 0300   Not tainted  (5.6.0-rc2-next-20200218-autotest)
[    8.768671] MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 24004844  XER: 00000000
[    8.768679] CFAR: c00000000000dec4 DAR: 00000000000073b0 DSISR: 40000000 IRQMASK: 1
[    8.768679] GPR00: c0000000003d5b94 c0000008b3783960 c00000000155d400 c0000008b301f500
[    8.768679] GPR04: 0000000000000dc0 0000000000000002 c0000000003443d8 c0000008bb398620
[    8.768679] GPR08: 00000008ba2f0000 0000000000000001 0000000000000000 0000000000000000
[    8.768679] GPR12: 0000000024004844 c00000001ec52a00 0000000000000000 0000000000000000
[    8.768679] GPR16: c0000008a1b20048 c000000001595898 c000000001750c18 0000000000000002
[    8.768679] GPR20: c000000001750c28 c000000001624470 0000000fffffffe0 5deadbeef0000122
[    8.768679] GPR24: 0000000000000001 0000000000000dc0 0000000000000002 c0000000003443d8
[    8.768679] GPR28: c0000008b301f500 c0000008bb398620 0000000000000000 c00c000002287180
[    8.768727] NIP [c0000000003d55f4] ___slab_alloc+0x1f4/0x760
[    8.768732] LR [c0000000003d5b94] __slab_alloc+0x34/0x60
[    8.768735] Call Trace:
[    8.768739] [c0000008b3783960] [c0000000003d5734] ___slab_alloc+0x334/0x760 (unreliable)
[    8.768745] [c0000008b3783a40] [c0000000003d5b94] __slab_alloc+0x34/0x60
[    8.768751] [c0000008b3783a70] [c0000000003d6fa0] __kmalloc_node+0x110/0x490
[    8.768757] [c0000008b3783af0] [c0000000003443d8] kvmalloc_node+0x58/0x110
[    8.768763] [c0000008b3783b30] [c0000000003fee38] mem_cgroup_css_online+0x108/0x270
[    8.768769] [c0000008b3783b90] [c000000000235aa8] online_css+0x48/0xd0
[    8.768775] [c0000008b3783bc0] [c00000000023eaec] cgroup_apply_control_enable+0x2ec/0x4d0
[    8.768781] [c0000008b3783ca0] [c000000000242318] cgroup_mkdir+0x228/0x5f0
[    8.768786] [c0000008b3783d10] [c00000000051e170] kernfs_iop_mkdir+0x90/0xf0
[    8.768792] [c0000008b3783d50] [c00000000043dc00] vfs_mkdir+0x110/0x230
[    8.768797] [c0000008b3783da0] [c000000000441c90] do_mkdirat+0xb0/0x1a0
[    8.768804] [c0000008b3783e20] [c00000000000b278] system_call+0x5c/0x68
[    8.768808] Instruction dump:
[    8.768811] 7c421378 e95f0000 714a0001 4082fff0 4bffff64 60000000 60000000 faa10088
[    8.768818] 3ea2000c 3ab57070 7b4a1f24 7d55502a <e94a73b0> 2faa0000 409e0394 3d02002a
[    8.768826] ---[ end trace 631af2cb73507891 ]---
[    8.770876]
[    9.770887] Kernel panic - not syncing: Fatal exception

Bisect reveals the problem was introduced in next-20200217 by following commit 

commit a75056fc1e7c 
mm/memcontrol.c: allocate shrinker_map on appropriate NUMA node

I can boot the kernel successfully if the patch is reverted. 

Boot log attached.

Thanks
-Sachin

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