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commit 003af997c8a945493859dd1a2d015cc9387ff27a upstream.
When trying to allocate a hugepage with no reserved ones free, it may be
allowed in case a number of overcommit hugepages was configured (using
/proc/sys/vm/nr_overcommit_hugepages) and that number wasn't reached.
This allows for a behavior of having extra hugepages allocated
dynamically, if there're resources for it. Some sysadmins even prefer not
reserving any hugepages and setting a big number of overcommit hugepages.
But while attempting to allocate overcommit hugepages in a multi node
system (either NUMA or mempolicy/cpuset) said allocations might randomly
fail even when there're resources available for the allocation.
This happens due to allowed_mems_nr() only accounting for the number of
free hugepages in the nodes the current process belongs to and the surplus
hugepage allocation is done so it can be allocated in any node. 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
Repeating the execution of map_hugetlb test application will eventually
fail when the hugepage ends up allocated in a different node.
[aris@ruivo.org: v2]
Link: https://lkml.kernel.org/r/20240701212343.GG844599@cathedrallabs.org
Link: https://lkml.kernel.org/r/20240621190050.mhxwb65zn37doegp@redhat.com
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Aristeu Rozanski <aris@ruivo.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Vishal Moola <vishal.moola@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
eebc67ae0b