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")
Tested-by: Venkat Rao Bagalkote <[email protected]>
Signed-off-by: Sayali Patil <[email protected]>
---
 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


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