Ensure that zswap.writeback check goes up the cgroup tree, i.e. is hierarchical. Create a subcgroup which has zswap.writeback set to 1, and the upper hierarchy's restrictions shall apply. Changes in v3: - Skip the zswap.writeback test if root cgroup has it disabled (I still think adding a whole new test is a bit of overkill, though, instead came up with this alternative approach) - Add comment about hardcoding child cg's zswap.writeback=1 which might not be obvious Link to v2: https://lore.kernel.org/all/20240816144344.18135-2-me@xxxxxxxxxxx/ Signed-off-by: Mike Yuan <me@xxxxxxxxxxx> --- tools/testing/selftests/cgroup/test_zswap.c | 75 +++++++++++++++------ 1 file changed, 54 insertions(+), 21 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index 190096017f80..40de679248b8 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -263,15 +263,13 @@ static int test_zswapin(const char *root) static int attempt_writeback(const char *cgroup, void *arg) { long pagesize = sysconf(_SC_PAGESIZE); - char *test_group = arg; size_t memsize = MB(4); char buf[pagesize]; long zswap_usage; - bool wb_enabled; + bool wb_enabled = *(bool *) arg; int ret = -1; char *mem; - wb_enabled = cg_read_long(test_group, "memory.zswap.writeback"); mem = (char *)malloc(memsize); if (!mem) return ret; @@ -288,12 +286,12 @@ static int attempt_writeback(const char *cgroup, void *arg) memcpy(&mem[i], buf, pagesize); /* Try and reclaim allocated memory */ - if (cg_write_numeric(test_group, "memory.reclaim", memsize)) { + if (cg_write_numeric(cgroup, "memory.reclaim", memsize)) { ksft_print_msg("Failed to reclaim all of the requested memory\n"); goto out; } - zswap_usage = cg_read_long(test_group, "memory.zswap.current"); + zswap_usage = cg_read_long(cgroup, "memory.zswap.current"); /* zswpin */ for (int i = 0; i < memsize; i += pagesize) { @@ -303,7 +301,7 @@ static int attempt_writeback(const char *cgroup, void *arg) } } - if (cg_write_numeric(test_group, "memory.zswap.max", zswap_usage/2)) + if (cg_write_numeric(cgroup, "memory.zswap.max", zswap_usage/2)) goto out; /* @@ -312,7 +310,7 @@ static int attempt_writeback(const char *cgroup, void *arg) * If writeback is disabled, memory reclaim will fail as zswap is limited and * it can't writeback to swap. */ - ret = cg_write_numeric(test_group, "memory.reclaim", memsize); + ret = cg_write_numeric(cgroup, "memory.reclaim", memsize); if (!wb_enabled) ret = (ret == -EAGAIN) ? 0 : -1; @@ -321,12 +319,41 @@ static int attempt_writeback(const char *cgroup, void *arg) return ret; } +static int test_zswap_writeback_one(const char *cgroup, bool wb) +{ + long zswpwb_before, zswpwb_after; + + zswpwb_before = get_cg_wb_count(cgroup); + if (zswpwb_before != 0) { + ksft_print_msg("zswpwb_before = %ld instead of 0\n", zswpwb_before); + return -1; + } + + if (cg_run(cgroup, attempt_writeback, (void *) &wb)) + return -1; + + /* Verify that zswap writeback occurred only if writeback was enabled */ + zswpwb_after = get_cg_wb_count(cgroup); + if (zswpwb_after < 0) + return -1; + + if (wb != !!zswpwb_after) { + ksft_print_msg("zswpwb_after is %ld while wb is %s", + zswpwb_after, wb ? "enabled" : "disabled"); + return -1; + } + + return 0; +} + /* Test to verify the zswap writeback path */ static int test_zswap_writeback(const char *root, bool wb) { - long zswpwb_before, zswpwb_after; int ret = KSFT_FAIL; - char *test_group; + char *test_group, *test_group_child = NULL; + + if (cg_read_strcmp(root, "memory.zswap.writeback", "1")) + return KSFT_SKIP; test_group = cg_name(root, "zswap_writeback_test"); if (!test_group) @@ -336,29 +363,35 @@ static int test_zswap_writeback(const char *root, bool wb) if (cg_write(test_group, "memory.zswap.writeback", wb ? "1" : "0")) goto out; - zswpwb_before = get_cg_wb_count(test_group); - if (zswpwb_before != 0) { - ksft_print_msg("zswpwb_before = %ld instead of 0\n", zswpwb_before); + if (test_zswap_writeback_one(test_group, wb)) goto out; - } - if (cg_run(test_group, attempt_writeback, (void *) test_group)) + /* Reset memory.zswap.max to max (modified by attempt_writeback), and + * set up child cgroup, whose memory.zswap.writeback is hardcoded to 1. + * Thus, the parent's setting shall be what's in effect. */ + if (cg_write(test_group, "memory.zswap.max", "max")) + goto out; + if (cg_write(test_group, "cgroup.subtree_control", "+memory")) goto out; - /* Verify that zswap writeback occurred only if writeback was enabled */ - zswpwb_after = get_cg_wb_count(test_group); - if (zswpwb_after < 0) + test_group_child = cg_name(test_group, "zswap_writeback_test_child"); + if (!test_group_child) + goto out; + if (cg_create(test_group_child)) + goto out; + if (cg_write(test_group_child, "memory.zswap.writeback", "1")) goto out; - if (wb != !!zswpwb_after) { - ksft_print_msg("zswpwb_after is %ld while wb is %s", - zswpwb_after, wb ? "enabled" : "disabled"); + if (test_zswap_writeback_one(test_group_child, wb)) goto out; - } ret = KSFT_PASS; out: + if (test_group_child) { + cg_destroy(test_group_child); + free(test_group_child); + } cg_destroy(test_group); free(test_group); return ret; -- 2.46.0
