On 13.06.25 03:49, Baolin Wang wrote:
When running the khugepaged selftest for shmem (./khugepaged all:shmem), I encountered the following test failures: " Run test: collapse_full (khugepaged:shmem) Collapse multiple fully populated PTE table.... Fail ... Run test: collapse_single_pte_entry (khugepaged:shmem) Collapse PTE table with single PTE entry present.... Fail ... Run test: collapse_full_of_compound (khugepaged:shmem) Allocate huge page... OK Split huge page leaving single PTE page table full of compound pages... OK Collapse PTE table full of compound pages.... Fail "The reason for the failure is that, it will set MADV_NOHUGEPAGE to prevent khugepaged from continuing to scan shmem VMA after khugepaged finishes scanning in the wait_for_scan() function. Moreover, shmem requires a refault to establish PMD mappings. However, after commit 2b0f922323cc ("mm: don't install PMD mappings when THPs are disabled by the hw/process/vma"), PMD mappings are prevented if the VMA is set with MADV_NOHUGEPAGE flag, so shmem cannot establish PMD mappings during refault. One way to fix this issue is to move the MADV_NOHUGEPAGE setting after the shmem refault. After shmem refault and check huge, the test case will unmap the shmem immediately. So it seems unnecessary to set the MADV_NOHUGEPAGE. Then we can simply drop the MADV_NOHUGEPAGE setting, and all khugepaged test cases passed. Fixes: 2b0f922323cc ("mm: don't install PMD mappings when THPs are disabled by the hw/process/vma") Reviewed-by: Zi Yan <[email protected]> Signed-off-by: Baolin Wang <[email protected]> ---
Acked-by: David Hildenbrand <[email protected]> -- Cheers, David / dhildenb
