test/maps01: document mmap() failures

Arm32 devices often have poor amount of RAM. E.g., RPI2 board
has only 1Gb memory. This lead to failures with maps01 test,
which tries to mmap() 1Gb of memory. The failures of test is
not very evident - let's document mmap() errors here to
blow some light on the situation.
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

test/zdtm/static/maps01.c

@@ -11,10 +11,10 @@
 #include <linux/limits.h>
 #include "zdtmtst.h"
 
-#define MEM_SIZE (1L << 30)
-#define MEM_OFFSET (1L << 29)
+#define MEM_SIZE (1LU << 30)
+#define MEM_OFFSET (1LU << 29)
 #define MEM_OFFSET2 (MEM_SIZE - PAGE_SIZE)
-#define MEM_OFFSET3 (20 * PAGE_SIZE)
+#define MEM_OFFSET3 (20LU * PAGE_SIZE)
 
 const char *test_doc	= "Test shared memory";
 const char *test_author	= "Andrew Vagin <avagin@openvz.org";
@@ -35,29 +35,42 @@ int main(int argc, char ** argv)
 	m = mmap(NULL, MEM_SIZE, PROT_WRITE | PROT_READ,
 				MAP_SHARED | MAP_ANONYMOUS, -1, 0);
 
-	if (m == MAP_FAILED)
+	if (m == MAP_FAILED) {
+		pr_err("Failed to mmap %lu Mb shared anonymous R/W memory\n",
+				MEM_SIZE >> 20);
 		goto err;
+	}
 
 	p = mmap(NULL, MEM_SIZE, PROT_WRITE | PROT_READ,
 				MAP_SHARED | MAP_ANONYMOUS, -1, 0);
 
-	if (p == MAP_FAILED)
+	if (p == MAP_FAILED) {
+		pr_err("Failed to mmap %ld Mb shared anonymous R/W memory\n",
+				MEM_SIZE >> 20);
 		goto err;
+	}
 
 	p2 = mmap(NULL, MEM_OFFSET, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-	if (p2 == MAP_FAILED)
+	if (p2 == MAP_FAILED) {
+		pr_err("Failed to mmap %lu Mb anonymous memory\n",
+				MEM_OFFSET >> 20);
 		goto err;
+	}
 
 	pid = test_fork();
 	if (pid < 0) {
+		pr_err("Fork failed with %d\n", pid);
 		goto err;
 	} else if (pid == 0) {
 		void *p3;
 
 		p3 = mmap(NULL, MEM_OFFSET3, PROT_READ | PROT_WRITE,
 					MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-		if (p3 == MAP_FAILED)
+		if (p3 == MAP_FAILED) {
+			pr_err("Failed to mmap %lu Mb anonymous R/W memory\n",
+					MEM_OFFSET3 >> 20);
 			goto err;
+		}
 
 		crc = ~0;
 		datagen(m + MEM_OFFSET, PAGE_SIZE, &crc);