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

[SJ Park <sj@kernel.org>]

On Fri, 13 Nov 2026 14:26:42 -0500 "Gregory Price (Meta)" <gourry@gourry.net> 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.

Makes sense and looks good to me.

> 
> Signed-off-by: Gregory Price (Meta) <gourry@gourry.net>

Reviewed-by: SJ Park <sj@kernel.org>


Thanks,
SJ

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