Re: [PATCH] mm/mempolicy: ignore a bind policy whose nodes have no memory

[Zi Yan <ziy@nvidia.com>]

On 13 Nov 2026, at 15:14, Gregory Price (Meta) wrote:

> On 2026-11-13 14:47 -0500, Zi Yan wrote:
>> On 13 Nov 2026, at 14:26, Gregory Price (Meta) wrote:
>>
>>> apply_policy_zone() assumes that policy->nodes intersects N_MEMORY, so
>>> it reads a bind policy with no N_HIGH_MEMORY node as movable-only.
>>>
>>> On systems with CONFIG_CPUSETS=n, nothing rebinds policies when memory
>>> is removed, so offlining all memory on the nodes a bind policy names
>>> leaves it with none. The policy is then treated as movable-only, and
>>> movable allocations are restricted to nodes without memory.
>>>
>>> This results in allocations failures, a VM_FAULT_OOM leak, and then
>>> an infinitely retrying fault that hangs the process.
>>>
>>>   page allocation failure: order:0, mode:0x140dca ... nodemask=2
>>>   Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF
>>>
>>> Ignore a bind policy whose nodes have no memory. policy_nodemask()
>>> already ignores a bind policy that does not intersect the cpuset.
>>> This covers hugetlb's policy_mbind_nodemask() as well.
>>>
>>> If the nodes regain memory, the policy applies again.
>>>
>>> CPUSETS=n with HOTREMOVE=y is unlikely a common configuration, so this
>>> isn't marked for stable.
>>
>> Also no Fixes?
>>
>
> It wasn't quite obvious what to tag exactly.  Since I don't think it's
> worth backporting, wasn't sure I should bother spending time on the
> Fixes tag.

I can imagine that. We probably can blame mbind or hotremove, but the
commit might be too old to be meaningful. It is all good now.

Best Regards,
Yan, Zi