Add a comment explaining that every other entry in the list is
unmapped to intentionally create fragmentation with
locked pages before invoking check_compaction().

Fixes: bd67d5c15cc1 ("Test compaction of mlocked memory")
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
---
 tools/testing/selftests/mm/compaction_test.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/testing/selftests/mm/compaction_test.c b/tools/testing/selftests/mm/compaction_test.c
index 30209c40b697..e1610e2fbdf6 100644
--- a/tools/testing/selftests/mm/compaction_test.c
+++ b/tools/testing/selftests/mm/compaction_test.c
@@ -261,6 +261,9 @@ int main(int argc, char **argv)
 		mem_fragmentable_MB -= MAP_SIZE_MB;
 	}
 
+	/* Unmap every other entry in the list to create fragmentation with
+	 * locked pages before invoking check_compaction().
+	 */
 	for (entry = list; entry != NULL; entry = entry->next) {
 		munmap(entry->map, MAP_SIZE);
 		if (!entry->next)
-- 
2.52.0