[PATCH] selftests/mm: run_vmtests.sh: Fix hugetlb mem size calculation

[peterx@redhat.com]

From: Peter Xu <peterx@redhat.com>

The script calculates a mininum required size of hugetlb memories, but
it'll stop working with <1MB huge page sizes, reporting all zeros even if
huge pages are available.

In reality, the calculation doesn't really need to be as comlicated either.
Make it simpler and work for KB-level hugepages too.

Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tools/testing/selftests/mm/run_vmtests.sh | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index c2c542fe7b17..b1b78e45d613 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -152,9 +152,13 @@ done < /proc/meminfo
 # both of these requirements into account and attempt to increase
 # number of huge pages available.
 nr_cpus=$(nproc)
-hpgsize_MB=$((hpgsize_KB / 1024))
-half_ufd_size_MB=$((((nr_cpus * hpgsize_MB + 127) / 128) * 128))
-needmem_KB=$((half_ufd_size_MB * 2 * 1024))
+uffd_min_KB=$((hpgsize_KB * nr_cpus * 2))
+hugetlb_min_KB=$((256 * 1024))
+if [[ $uffd_min_KB -gt $hugetlb_min_KB ]]; then
+	needmem_KB=$uffd_min_KB
+else
+	needmem_KB=$hugetlb_min_KB
+fi
 
 # set proper nr_hugepages
 if [ -n "$freepgs" ] && [ -n "$hpgsize_KB" ]; then
-- 
2.44.0