From: "Kiryl Shutsemau (Meta)" <[email protected]> The page cache caps folio order at MAX_PAGECACHE_ORDER, and xas_split_alloc() puts that cap below the PMD order where a PMD is 512M -- arm64 with 64K base pages, as include/linux/pagemap.h says outright. shmem_huge_global_enabled() then offers no PMD order at all, so MADV_COLLAPSE of a shmem range answers -EINVAL and khugepaged passes over it.
The shmem cases nonetheless ask for a PMD-sized shmem folio, so on such a configuration four of them fail and the run bails out in the middle: not ok 2 collapse_full not ok 4 collapse_single_pte_entry # Allocate huge page...Bail out! madvise(MADV_COLLAPSE): Invalid argument (22) That is the kernel declining something it deliberately does not support, not a collapse defect. Skip those cases where the PMD order is not a shmem order, which thp_shmem_supported_orders() already reports -- it reads the same per-size shmem_enabled controls the kernel only publishes for orders the page cache can hold. A tmpfs-backed file argument is skipped on the same grounds, and a run left with nothing to collapse into skips outright. Anonymous collapse is unaffected: its orders are not capped this way, and the anonymous cases pass at a 512M PMD. Assisted-by: Claude-Code:claude-opus-5 Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> --- tools/testing/selftests/mm/khugepaged.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c index 9213ce1658d0..c5a3c3922581 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -1584,6 +1584,27 @@ int main(int argc, char **argv) hpage_pmd_nr = hpage_pmd_size / page_size; hpage_pmd_order = __builtin_ctz(hpage_pmd_nr); + /* + * The page cache caps folio order at MAX_PAGECACHE_ORDER, which + * xas_split_alloc() puts below the PMD order on arm64 with 64K pages. + * A PMD-sized page cache folio is then impossible, so the kernel + * refuses these collapses by design and there is nothing to test. + */ + if (!(thp_shmem_supported_orders() & (1UL << hpage_pmd_order))) { + if (shmem_ops) { + ksft_print_msg("no PMD-order page cache folio: skipping shmem\n"); + shmem_ops = NULL; + } + if (finfo.type == VMA_SHMEM && read_only_file_ops) { + ksft_print_msg("no PMD-order page cache folio: skipping tmpfs file\n"); + read_only_file_ops = NULL; + read_write_file_read_ops = NULL; + read_write_file_write_ops = NULL; + } + if (!anon_ops && !shmem_ops && !read_only_file_ops) + ksft_exit_skip("Nothing left to collapse into\n"); + } + if (anon_target_order && !(thp_supported_orders() & (1UL << anon_target_order))) ksft_exit_skip("Order %d is not a supported anon THP order\n", -- 2.54.0
