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Subject[PATCH 2/2] mm: do not warn on offline nodes unless the specific node is explicitly requested
Date
From: Michal Hocko <mhocko@suse.com>

Oscar has noticed that we splat
linux kernel: WARNING: CPU: 0 PID: 64 at ./include/linux/gfp.h:467 vmemmap_alloc_block+0x4e/0xc9
[...]
linux kernel: CPU: 0 PID: 64 Comm: kworker/u4:1 Tainted: G W E 4.17.0-rc5-next-20180517-1-default+ #66
linux kernel: Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014
linux kernel: Workqueue: kacpi_hotplug acpi_hotplug_work_fn
linux kernel: RIP: 0010:vmemmap_alloc_block+0x4e/0xc9
linux kernel: Code: fb ff 8d 69 01 75 07 65 8b 1d 9d cb 93 7e 81 fb ff 03 00 00 76 02 0f 0b 48 63 c3 48 0f a3 05 c8 b1 b4 00 0f 92 c0 84 c0 75 02 <0f> 0b 31 c9 89 da 89 ee bf c0 06 40 01 e8 0f d1 ad ff 48 85 c0 74
linux kernel: RSP: 0018:ffffc90000d03bf0 EFLAGS: 00010246
linux kernel: RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000008
linux kernel: RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000000001ff
linux kernel: RBP: 0000000000000009 R08: 0000000000000001 R09: ffffc90000d03ae8
linux kernel: R10: 0000000000000001 R11: 0000000000000000 R12: ffffea0006000000
linux kernel: R13: ffffea0005e00000 R14: ffffea0006000000 R15: 0000000000000001
linux kernel: FS: 0000000000000000(0000) GS:ffff88013fc00000(0000) knlGS:0000000000000000
linux kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
linux kernel: CR2: 00007fa92a698018 CR3: 00000001184ce000 CR4: 00000000000006f0
linux kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
linux kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
linux kernel: Call Trace:
linux kernel: vmemmap_populate+0xf2/0x2ae
linux kernel: sparse_mem_map_populate+0x28/0x35
linux kernel: sparse_add_one_section+0x4c/0x187
linux kernel: __add_pages+0xe7/0x1a0
linux kernel: add_pages+0x16/0x70
linux kernel: add_memory_resource+0xa3/0x1d0
linux kernel: add_memory+0xe4/0x110
linux kernel: acpi_memory_device_add+0x134/0x2e0
linux kernel: acpi_bus_attach+0xd9/0x190
linux kernel: acpi_bus_scan+0x37/0x70
linux kernel: acpi_device_hotplug+0x389/0x4e0
linux kernel: acpi_hotplug_work_fn+0x1a/0x30
linux kernel: process_one_work+0x146/0x340
linux kernel: worker_thread+0x47/0x3e0
linux kernel: kthread+0xf5/0x130
linux kernel: ? max_active_store+0x60/0x60
linux kernel: ? kthread_bind+0x10/0x10
linux kernel: ret_from_fork+0x35/0x40
linux kernel: ---[ end trace 2e2241f4e2f2f018 ]---
====

when adding memory to a node that is currently offline.

The VM_WARN_ON is just too loud without a good reason. In this
particular case we are doing
alloc_pages_node(node, GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN, order)

so we do not insist on allocating from the given node (it is more a
hint) so we can fall back to any other populated node and moreover we
explicitly ask to not warn for the allocation failure.

Soften the warning only to cases when somebody asks for the given node
explicitly by __GFP_THISNODE.

Reported-by: Oscar Salvador <osalvador@techadventures.net>
Tested-by: Oscar Salvador <osalvador@techadventures.net>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
include/linux/gfp.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 036846fc00a6..7f860ea29ec6 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -464,7 +464,7 @@ static inline struct page *
__alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
{
VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
- VM_WARN_ON(!node_online(nid));
+ VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid));

return __alloc_pages(gfp_mask, order, nid);
}
--
2.17.0
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