Re: [PATCH] hugetlb: force allocating surplus hugepages on mempolicy allowed nodes

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 21 Jun 2024 17:56:09 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:

> On Fri, 21 Jun 2024 15:00:50 -0400 Aristeu Rozanski <aris@redhat.com> wrote:
> 
> > allowed_mems_nr() only accounts for the number of free hugepages in the nodes
> > the current process belongs to. In case one or more of the requested surplus
> > hugepages are allocated in a different node, the whole allocation will fail due
> > allowed_mems_nr() returning a lower value.
> > 
> > So allocate surplus hugepages in one of the nodes the current process belongs to.
> > 
> > Easy way to reproduce this issue is to use a 2+ NUMA nodes system:
> > 
> > 		# echo 0 >/proc/sys/vm/nr_hugepages
> > 		# echo 1 >/proc/sys/vm/nr_overcommit_hugepages
> > 		# numactl -m0 ./tools/testing/selftests/mm/map_hugetlb 2
> > 
> > will eventually fail when the hugepage ends up allocated in a different node.
> > 
> 
> Should we backport this into -stable kernels?

Please?

Aristeu, a description of the userspace-visible effects of the bug will
really help things along here.