From 8a7ff397a900ee35eef49b0619197ed0970d8c54 Mon Sep 17 00:00:00 2001 From: Yijia Wang Date: Mon, 13 Jul 2026 17:43:19 +0800 Subject: [PATCH] selftests: mincore: count file-mmap readahead on both sides 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. Link: https://lore.kernel.org/20260713094319.771550-1-wangyijia.yeah@bytedance.com Signed-off-by: Yijia Wang Cc: "Matthew Wilcox (Oracle)" Cc: Jan Kara Cc: Muchun Song Cc: Shuah Khan Signed-off-by: Andrew Morton --- 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 cdd022c1c497..18dfbf318b1f 100644 --- a/tools/testing/selftests/mincore/mincore_selftest.c +++ b/tools/testing/selftests/mincore/mincore_selftest.c @@ -242,8 +242,10 @@ 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); @@ -252,6 +254,12 @@ 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++;