[LTP] [PATCH v3] madvise09: Reset cgroup limits before retrying test

[Wake Liu]

When madvise09 enters its retry loop, the cgroup limits (memory.max and
memory.swap.max) configured in the previous run remain active. If the
previous run ended due to memory pressure, the inherited limits will
cause the new child to immediately reclaim MADV_FREE pages. This
results in false-positive failures during test verification.

Reset both memory.max and memory.swap.max to "max" at the start of
child() to ensure each retry run begins in an unconstrained cgroup.

Signed-off-by: Wake Liu <wakel@google.com>
---
 testcases/kernel/syscalls/madvise/madvise09.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/testcases/kernel/syscalls/madvise/madvise09.c b/testcases/kernel/syscalls/madvise/madvise09.c
index 87fe096fb..9eb6e82ec 100644
--- a/testcases/kernel/syscalls/madvise/madvise09.c
+++ b/testcases/kernel/syscalls/madvise/madvise09.c
@@ -146,6 +146,16 @@ static void child(void)
 
 	SAFE_CG_PRINTF(tst_cg, "cgroup.procs", "%d", getpid());
 
+	/*
+	 * Reset cgroup memory limits to default ("max") in case this is a retry run.
+	 * Otherwise, the retried child inherits the strict MEM_LIMIT from the previous
+	 * run, causing MADV_FREE pages to be dropped immediately before we touch them.
+	 */
+	if (SAFE_CG_HAS(tst_cg, "memory.max"))
+		SAFE_CG_PRINT(tst_cg, "memory.max", "max");
+	if (swap_accounting_enabled && SAFE_CG_HAS(tst_cg, "memory.swap.max"))
+		SAFE_CG_PRINT(tst_cg, "memory.swap.max", "max");
+
 	ptr = SAFE_MMAP(NULL, PAGES * page_size, PROT_READ | PROT_WRITE,
 			MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 
-- 
2.55.0.795.g602f6c329a-goog