test_no_kmem_bypass() needs to read /sys/kernel/debug/zswap/stored_pages via get_zswap_stored_pages() to verify that compressed pages are charged to the memcg.
When running in an environment where debugfs is not mounted or CONFIG_DEBUG_FS is disabled, get_zswap_stored_pages() fails, causing the loop to terminate early and report a false negative (KSFT_FAIL). Selftests should not fail if debugfs is unavailable, and it should print a message when it is skipped. While I'm here, also add a warning message if the test is being skipped due to totalram size and make the check for totalram more readable. Signed-off-by: Wilson Felipe Pereira <[email protected]> --- v1 -> v2: - Check for debugfs availability using access("/sys/kernel/debug/zswap/stored_pages", R_OK) instead of calling get_zswap_stored_pages() (Yosry Ahmed). - Update debugfs print message to exactly match gup_test.c (Anshuman Khandual). - Add GB(x) macro to cgroup_util.h (Yosry Ahmed). Cast to unsigned long long to prevent 32-bit truncation without altering existing MB(x) signedness. - Update RAM check to GB(4) to match comments and format totalram output with 1 decimal place (%.1fGB) (Yosry Ahmed). - Fix commit message typo (Yosry Ahmed). - Moved stored_pages back inside the for loop. v1: https://lore.kernel.org/all/[email protected]/ .../selftests/cgroup/lib/include/cgroup_util.h | 1 + tools/testing/selftests/cgroup/test_zswap.c | 13 +++++++++++-- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/cgroup/lib/include/cgroup_util.h b/tools/testing/selftests/cgroup/lib/include/cgroup_util.h index febc1723d0903..c0f07226b222f 100644 --- a/tools/testing/selftests/cgroup/lib/include/cgroup_util.h +++ b/tools/testing/selftests/cgroup/lib/include/cgroup_util.h @@ -7,6 +7,7 @@ #endif #define MB(x) (x << 20) +#define GB(x) ((unsigned long long)(x) << 30) #define USEC_PER_SEC 1000000L #define NSEC_PER_SEC 1000000000L diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index 49b36ee791606..a836337440040 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -20,6 +20,7 @@ static int page_size; #define PATH_ZSWAP "/sys/module/zswap" #define PATH_ZSWAP_ENABLED "/sys/module/zswap/parameters/enabled" +#define PATH_ZSWAP_STORED_PAGES "/sys/kernel/debug/zswap/stored_pages" static int read_int(const char *path, size_t *value) { @@ -55,7 +56,7 @@ static int read_min_free_kb(size_t *value) static int get_zswap_stored_pages(size_t *value) { - return read_int("/sys/kernel/debug/zswap/stored_pages", value); + return read_int(PATH_ZSWAP_STORED_PAGES, value); } static long get_cg_wb_count(const char *cg) @@ -570,8 +571,16 @@ static int test_no_kmem_bypass(const char *root) /* Read sys info and compute test values accordingly */ if (sysinfo(&sys_info) != 0) return KSFT_FAIL; - if (sys_info.totalram > 5000000000) + if (sys_info.totalram > GB(4)) { + ksft_print_msg( + "requires less than 4GB total ram, sys_info.totalram: %.1fGB\n", + (double)sys_info.totalram / GB(1)); return KSFT_SKIP; + } + if (access(PATH_ZSWAP_STORED_PAGES, R_OK)) { + ksft_print_msg("mount debugfs at /sys/kernel/debug\n"); + return KSFT_SKIP; + } values = mmap(0, sizeof(struct no_kmem_bypass_child_args), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); if (values == MAP_FAILED) -- 2.55.0.679.g6767b8d81c-goog
