Re: [PATCH bpf-next v4 1/4] bpf: Add a sleepable page allocator for map memory

[Jiayuan Chen]

On 8/24/26 8:26 PM, Michal Hocko wrote:
> On Fri 21-08-26 13:06:12, Jiayuan Chen wrote:
> > bpf_map_alloc_pages() picks the allocator via can_alloc_pages(), a
> > conservative guess for BPF program context that is always false under
> > PREEMPT_RT. So even a caller that really is sleepable gets the
> > non-blocking allocator, which never reclaims and never engages the OOM
> > machinery.
> I thought one of the main motivations was reentrancy. As you cannot
> really assume the context bpf_map_alloc_pages is called from there is an
> extra care needed so that this doesn't re-enter the allocator from bpf
> program called from allocator path and deadlock.


Agreed, bpf_map_alloc_pages() is designed to be safe to run in any context.

The commit message should be precise.