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SubjectRe: [PATCH 2/3] mm, meminit: Always return a valid node from early_pfn_to_nid
On Fri, 8 Jul 2016, Mel Gorman wrote:

> early_pfn_to_nid can return node 0 if a PFN is invalid on machines
> that has no node 0. A machine with only node 1 was observed to crash
> with the following message
>
> BUG: unable to handle kernel paging request at 000000000002a3c8
> PGD 0
> Modules linked in:
> Hardware name: Supermicro H8DSP-8/H8DSP-8, BIOS 080011 06/30/2006
> task: ffffffff81c0d500 ti: ffffffff81c00000 task.ti: ffffffff81c00000
> RIP: 0010:[<ffffffff816dbd63>] [<ffffffff816dbd63>] reserve_bootmem_region+0x6a/0xef
> RSP: 0000:ffffffff81c03eb0 EFLAGS: 00010086
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffffffff81c03ec0 RSI: ffffffff81d205c0 RDI: ffffffff8213ee60
> R13: ffffea0000000000 R14: ffffea0000000020 R15: ffffea0000000020
> FS: 0000000000000000(0000) GS:ffff8800fba00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000002a3c8 CR3: 0000000001c06000 CR4: 00000000000006b0
> Stack:
> ffffffff81c03f00 0000000000000400 ffff8800fbfc3200 ffffffff81e2a2c0
> ffffffff81c03fb0 ffffffff81c03f20 ffffffff81dadf7d ffffea0002000040
> ffffea0000000000 0000000000000000 000000000000ffff 0000000000000001
> Call Trace:
> [<ffffffff81dadf7d>] free_all_bootmem+0x4b/0x12a
> [<ffffffff81d97122>] mem_init+0x70/0xa3
> [<ffffffff81d78f21>] start_kernel+0x25b/0x49b
>
> The problem is that early_page_uninitialised uses the early_pfn_to_nid
> helper which returns node 0 for invalid PFNs. No caller of early_pfn_to_nid
> cares except early_page_uninitialised. This patch has early_pfn_to_nid
> always return a valid node.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> Cc: <stable@vger.kernel.org> # 4.2+

Acked-by: David Rientjes <rientjes@google.com>

This makes me wonder about meminit_pfn_in_nid(), however, since if
__early_pfn_to_nid() returns -1, which is the case in this bug,
meminit_pfn_in_nid() will return true for any passed node.

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