[LTP] [PATCH] thp02: simplify test to lower memory requirements

[Jan Stancek]

Test is using 4 hugepages per allocation, and makes 4*3 allocations
in total. This is problem for aarch64, where default huge page size
is 512M. Systems are running into unexpected OOMs, because there
is no check for available memory.

Simplify test by:
- dropping 3rd allocation, it's used only for pattern comparison
- run test function in new child process, so we don't need to worry
  about cleaning up after mremap() and it lowers overall memory
  requirements
- add a simple check if there's enough memory to setup()
- drop .needs_root, there's no need for it

Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
 testcases/kernel/mem/thp/thp02.c | 79 +++++++++++++++++++++++++---------------
 1 file changed, 50 insertions(+), 29 deletions(-)

diff --git a/testcases/kernel/mem/thp/thp02.c b/testcases/kernel/mem/thp/thp02.c
index 6502210e50de..4d0c929f91ff 100644
--- a/testcases/kernel/mem/thp/thp02.c
+++ b/testcases/kernel/mem/thp/thp02.c
@@ -47,46 +47,62 @@
 #ifdef HAVE_MREMAP_FIXED
 static int ps;
 static long hps, size;
-static void *p, *p2, *p3, *p4;
+
+/*
+ * Will try to do the following 4 mremaps cases:
+ *   mremap(p, size-ps, size-ps, flag, p3);
+ *   mremap(p, size-ps, size-ps, flag, p3+ps);
+ *   mremap(p+ps, size-ps, size-ps, flag, p3);
+ *   mremap(p+ps, size-ps, size-ps, flag, p3+ps);
+ */
+static void do_child(int i)
+{
+	long j, remap_size;
+	unsigned char *p1, *p2, *ret, *old_addr, *new_addr;
+
+	p1 = SAFE_MEMALIGN(hps, size);
+	p2 = SAFE_MEMALIGN(hps, size);
+
+	memset(p1, 0xff, size);
+	memset(p2, 0x77, size);
+
+	old_addr = p1 + ps * (i >> 1);
+	new_addr = p2 + ps * (i & 1);
+	remap_size = size - ps;
+
+	tst_res(TINFO, "mremap (%p-%p) to (%p-%p)",
+		old_addr, old_addr + remap_size,
+		new_addr, new_addr + remap_size);
+
+	ret = mremap(old_addr, remap_size, remap_size,
+		    MREMAP_FIXED | MREMAP_MAYMOVE, new_addr);
+	if (ret == MAP_FAILED)
+		tst_brk(TBROK | TERRNO, "mremap");
+
+	for (j = 0; j < size - ps; j++) {
+		if (ret[j] != 0xff)
+			tst_brk(TBROK, "mremap bug");
+	}
+
+	exit(0);
+}
 
 static void do_mremap(void)
 {
 	int i;
-	void *old_addr, *new_addr;
 
 	for (i = 0; i < 4; i++) {
-		p = SAFE_MEMALIGN(hps, size);
-		p2 = SAFE_MEMALIGN(hps, size);
-		p3 = SAFE_MEMALIGN(hps, size);
-
-		memset(p, 0xff, size);
-		memset(p2, 0xff, size);
-		memset(p3, 0x77, size);
-
-		/*
-		 * Will try to do the following 4 mremaps cases:
-		 *   mremap(p, size-ps, size-ps, flag, p3);
-		 *   mremap(p, size-ps, size-ps, flag, p3+ps);
-		 *   mremap(p+ps, size-ps, size-ps, flag, p3);
-		 *   mremap(p+ps, size-ps, size-ps, flag, p3+ps);
-		 */
-		old_addr = p + ps * (i >> 1);
-		new_addr = p3 + ps * (i & 1);
-		tst_res(TINFO, "mremap %p to %p", old_addr, new_addr);
-
-		p4 = mremap(old_addr, size - ps, size - ps,
-			    MREMAP_FIXED | MREMAP_MAYMOVE, new_addr);
-		if (p4 == MAP_FAILED)
-			tst_brk(TBROK | TERRNO, "mremap");
-		if (memcmp(p4, p2, size - ps))
-			tst_brk(TBROK, "mremap bug");
+		if (SAFE_FORK() == 0)
+			do_child(i);
+		tst_reap_children();
 	}
-
 	tst_res(TPASS, "Still alive.");
 }
 
 static void setup(void)
 {
+	long memfree;
+
 	if (access(PATH_THP, F_OK) == -1)
 		tst_brk(TCONF, "THP not enabled in kernel?");
 
@@ -95,12 +111,17 @@ static void setup(void)
 	ps = sysconf(_SC_PAGESIZE);
 	hps = SAFE_READ_MEMINFO("Hugepagesize:") * 1024;
 	size = hps * 4;
+
+	memfree = (SAFE_READ_MEMINFO("MemFree:") * 1024 +
+		SAFE_READ_MEMINFO("Cached:") * 1024);
+	if (memfree < size * 2)
+		tst_brk(TCONF, "not enough memory");
 }
 
 static struct tst_test test = {
-	.needs_root = 1,
 	.setup = setup,
 	.test_all = do_mremap,
+	.forks_child = 1,
 };
 
 #else
-- 
1.8.3.1