From: Yijia Wang <[email protected]> check_file_mmap() faults a page in the middle of a file mapping and expects the mmap read-around path to make neighbouring pages resident. The test currently counts only pages after the faulted page.
That misses valid read-around on systems with large base page sizes. On arm64 with 64K pages and the default 128K readahead setting, the read-around window is two pages wide and centred on the faulting page. Faulting page 32 makes pages 31 and 32 resident, so the forward-only scan from page 33 reports ra_pages == 0 even though a neighbouring page was brought in. Keep the existing readahead assertion, but count resident neighbouring pages on both sides of the faulted page. This fixes the 64K-page false failure without teaching the selftest to compute the expected readahead window from sysfs or other implementation details. Signed-off-by: Yijia Wang <[email protected]> --- Changes in v4: - Drop the sysfs read_ahead_kb helper and skip logic from v3. - Keep the existing ra_pages assertion and count resident readahead pages on both sides of the faulted page. tools/testing/selftests/mincore/mincore_selftest.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/mincore/mincore_selftest.c b/tools/testing/selftests/mincore/mincore_selftest.c index 3182043..ebf2b06 100644 --- a/tools/testing/selftests/mincore/mincore_selftest.c +++ b/tools/testing/selftests/mincore/mincore_selftest.c @@ -243,8 +243,10 @@ TEST(check_file_mmap) } /* - * Touch a page in the middle of the mapping. We expect the next - * few pages (the readahead window) to be populated too. + * Touch a page in the middle of the mapping. We expect some + * surrounding pages (the readahead window) to be populated too. + * Depending on the page size and readahead setting, the pages may + * land before the faulted page rather than after it. */ addr[FILE_SIZE / 2] = 1; retval = mincore(addr, FILE_SIZE, vec); @@ -253,6 +255,12 @@ TEST(check_file_mmap) TH_LOG("Page not found in memory after use"); } + i = FILE_SIZE / 2 / page_size - 1; + while (i >= 0 && vec[i]) { + ra_pages++; + i--; + } + i = FILE_SIZE / 2 / page_size + 1; while (i < vec_size && vec[i]) { ra_pages++; -- 2.43.0
