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

[Zi Yan]

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?

>
> Signed-off-by: Gregory Price (Meta) <gourry@xxxxxxxxxx>
> ---
>  mm/mempolicy.c | 4 ++++
>  1 file changed, 4 insertions(+)
>

LGTM.

Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>


Best Regards,
Yan, Zi