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Subject[PATCH] mm/alloc: fallback to first node if the wanted node offline
Date
During my test on some AMD machine, with kexec -l nr_cpus=x option, the
kernel failed to bootup, because some node's data struct can not be allocated,
e.g, on x86, initialized by init_cpu_to_node()->init_memory_less_node(). But
device->numa_node info is used as preferred_nid param for
__alloc_pages_nodemask(), which causes NULL reference
ac->zonelist = node_zonelist(preferred_nid, gfp_mask);
This patch tries to fix the issue by falling back to the first online node,
when encountering such corner case.

Notes about the crashing info:
-1. kexec -l with nr_cpus=4
-2. system info
NUMA node0 CPU(s): 0,8,16,24
NUMA node1 CPU(s): 2,10,18,26
NUMA node2 CPU(s): 4,12,20,28
NUMA node3 CPU(s): 6,14,22,30
NUMA node4 CPU(s): 1,9,17,25
NUMA node5 CPU(s): 3,11,19,27
NUMA node6 CPU(s): 5,13,21,29
NUMA node7 CPU(s): 7,15,23,31
-3. panic stack
[...]
[ 5.721547] atomic64_test: passed for x86-64 platform with CX8 and with SSE
[ 5.729187] pcieport 0000:00:01.1: Signaling PME with IRQ 34
[ 5.735187] pcieport 0000:00:01.2: Signaling PME with IRQ 35
[ 5.741168] pcieport 0000:00:01.3: Signaling PME with IRQ 36
[ 5.747189] pcieport 0000:00:07.1: Signaling PME with IRQ 37
[ 5.754061] pcieport 0000:00:08.1: Signaling PME with IRQ 39
[ 5.760727] pcieport 0000:20:07.1: Signaling PME with IRQ 40
[ 5.766955] pcieport 0000:20:08.1: Signaling PME with IRQ 42
[ 5.772742] BUG: unable to handle kernel paging request at 0000000000002088
[ 5.773618] PGD 0 P4D 0
[ 5.773618] Oops: 0000 [#1] SMP NOPTI
[ 5.773618] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.20.0-rc1+ #3
[ 5.773618] Hardware name: Dell Inc. PowerEdge R7425/02MJ3T, BIOS 1.4.3 06/29/2018
[ 5.773618] RIP: 0010:__alloc_pages_nodemask+0xe2/0x2a0
[ 5.773618] Code: 00 00 44 89 ea 80 ca 80 41 83 f8 01 44 0f 44 ea 89 da c1 ea 08 83 e2 01 88 54 24 20 48 8b 54 24 08 48 85 d2 0f 85 46 01 00 00 <3b> 77 08 0f 82 3d 01 00 00 48 89 f8 44 89 ea 48 89
e1 44 89 e6 89
[ 5.773618] RSP: 0018:ffffaa600005fb20 EFLAGS: 00010246
[ 5.773618] RAX: 0000000000000000 RBX: 00000000006012c0 RCX: 0000000000000000
[ 5.773618] RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000002080
[ 5.773618] RBP: 00000000006012c0 R08: 0000000000000000 R09: 0000000000000002
[ 5.773618] R10: 00000000006080c0 R11: 0000000000000002 R12: 0000000000000000
[ 5.773618] R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000002
[ 5.773618] FS: 0000000000000000(0000) GS:ffff8c69afe00000(0000) knlGS:0000000000000000
[ 5.773618] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 5.773618] CR2: 0000000000002088 CR3: 000000087e00a000 CR4: 00000000003406e0
[ 5.773618] Call Trace:
[ 5.773618] new_slab+0xa9/0x570
[ 5.773618] ___slab_alloc+0x375/0x540
[ 5.773618] ? pinctrl_bind_pins+0x2b/0x2a0
[ 5.773618] __slab_alloc+0x1c/0x38
[ 5.773618] __kmalloc_node_track_caller+0xc8/0x270
[ 5.773618] ? pinctrl_bind_pins+0x2b/0x2a0
[ 5.773618] devm_kmalloc+0x28/0x60
[ 5.773618] pinctrl_bind_pins+0x2b/0x2a0
[ 5.773618] really_probe+0x73/0x420
[ 5.773618] driver_probe_device+0x115/0x130
[ 5.773618] __driver_attach+0x103/0x110
[ 5.773618] ? driver_probe_device+0x130/0x130
[ 5.773618] bus_for_each_dev+0x67/0xc0
[ 5.773618] ? klist_add_tail+0x3b/0x70
[ 5.773618] bus_add_driver+0x41/0x260
[ 5.773618] ? pcie_port_setup+0x4d/0x4d
[ 5.773618] driver_register+0x5b/0xe0
[ 5.773618] ? pcie_port_setup+0x4d/0x4d
[ 5.773618] do_one_initcall+0x4e/0x1d4
[ 5.773618] ? init_setup+0x25/0x28
[ 5.773618] kernel_init_freeable+0x1c1/0x26e
[ 5.773618] ? loglevel+0x5b/0x5b
[ 5.773618] ? rest_init+0xb0/0xb0
[ 5.773618] kernel_init+0xa/0x110
[ 5.773618] ret_from_fork+0x22/0x40
[ 5.773618] Modules linked in:
[ 5.773618] CR2: 0000000000002088
[ 5.773618] ---[ end trace 1030c9120a03d081 ]---
[...]

Other notes about the reproduction of this bug:
After appling the following patch:
commit 0d76bcc960e6057750fcf556b65da13f8bbdfd2b
Author: Bjorn Helgaas <bhelgaas@google.com>
Date: Tue Nov 13 08:38:17 2018 -0600

Revert "ACPI/PCI: Pay attention to device-specific _PXM node values"

This bug is covered and not triggered on my test AMD machine.
But it should still exist since dev->numa_node info can be set by other
method on other archs when using nr_cpus param

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
include/linux/gfp.h | 2 ++
1 file changed, 2 insertions(+)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 76f8db0..8324953 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -453,6 +453,8 @@ static inline int gfp_zonelist(gfp_t flags)
*/
static inline struct zonelist *node_zonelist(int nid, gfp_t flags)
{
+ if (unlikely(!node_online(nid)))
+ nid = first_online_node;
return NODE_DATA(nid)->node_zonelists + gfp_zonelist(flags);
}

--
2.7.4
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