[LTP] [PATCH v2 2/2] Add new test for pipe2 with/without O_NONBLOCK mode.

[laniel_francis@privacyrequired.com]

From: Francis Laniel <laniel_francis@privacyrequired.com>

The new test (pipe2_03.c) checks the following:
1. Create a pipe with O_NONBLOCK.
2. Check that this flag is set.
3. Check that pipe size is 16 * PAGE_SIZE.
4. Reduce pipe size to PAGE_SIZE.
5. Write buffer bigger than page size and see that second write fails.
6. Set pipe's flags to default.
7. Fork and do a write in the child, its state must be 'S' and is checked from
the father.
---
 testcases/kernel/syscalls/pipe2/.gitignore |   1 +
 testcases/kernel/syscalls/pipe2/pipe2_03.c | 128 +++++++++++++++++++++
 2 files changed, 129 insertions(+)
 create mode 100644 testcases/kernel/syscalls/pipe2/pipe2_03.c

diff --git a/testcases/kernel/syscalls/pipe2/.gitignore b/testcases/kernel/syscalls/pipe2/.gitignore
index cd38bb309..01d980dba 100644
--- a/testcases/kernel/syscalls/pipe2/.gitignore
+++ b/testcases/kernel/syscalls/pipe2/.gitignore
@@ -1,2 +1,3 @@
 /pipe2_01
 /pipe2_02
+/pipe2_03
diff --git a/testcases/kernel/syscalls/pipe2/pipe2_03.c b/testcases/kernel/syscalls/pipe2/pipe2_03.c
new file mode 100644
index 000000000..c2b182e02
--- /dev/null
+++ b/testcases/kernel/syscalls/pipe2/pipe2_03.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2020 Francis Laniel. All rights reserved.
+ * Author: Francis Laniel <laniel_francis@privacyrequired.com>
+ *
+ * Test Description:
+ * This Program tests getting and setting the pipe size.
+ * It also tests what happen when you write to a full pipe depending on whether
+ * O_NONBLOCK is set or not.
+ */
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <features.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <assert.h>
+#include <sys/select.h>
+
+#include "lapi/fcntl.h"
+#include "tst_test.h"
+
+#define PAGE_NR 16
+#define SECONDS 3
+#define MICROSECONDS 0
+
+static int fds[2];
+static long page_size;
+
+static void setup(void)
+{
+	/*
+	 * Create the pipe with O_NONBLOCK.
+	 */
+	SAFE_PIPE2(fds, O_NONBLOCK);
+
+	/*
+	 * Get the system page size.
+	 */
+	page_size = SAFE_SYSCONF(_SC_PAGESIZE);
+}
+
+static void test_pipe2(void)
+{
+	long flags;
+	long pipe_size;
+
+	char *buf;
+
+	pid_t pid;
+	int status;
+
+	flags = SAFE_FCNTL(fds[0], F_GETFL);
+
+	if (!(flags & O_NONBLOCK))
+		tst_res(TFAIL, "O_NONBLOCK flag must be set.");
+
+	pipe_size = SAFE_FCNTL(fds[0], F_GETPIPE_SZ);
+
+	if (pipe_size != page_size * PAGE_NR)
+		tst_res(TFAIL, "Default pipe page is 16 * 4096 = 65536B.");
+
+	/*
+	 * A pipe has two file descriptors.
+	 * But in the kernel these two file descriptors point to the same pipe.
+	 * So setting size from first file handle set size for the pipe.
+	 */
+	SAFE_FCNTL(fds[0], F_SETPIPE_SZ, 0);
+
+	/*
+	 * So getting size from the second file descriptor return the size of
+	 * the pipe which was changed before with first file descriptor.
+	 */
+	pipe_size = SAFE_FCNTL(fds[1], F_GETPIPE_SZ);
+
+	if (pipe_size != page_size)
+		tst_res(TFAIL, "Pipe size (%ld) must be page size (%ld)",
+			pipe_size, page_size);
+
+	buf = alloca(page_size);
+
+	SAFE_WRITE(1, fds[1], buf, page_size);
+
+	/*
+	 * This write should return -1 because pipe is already full.
+	 */
+	if (write(fds[1], buf, page_size) != -1)
+		tst_res(TFAIL | TERRNO, "write() succeeded and should not");
+
+	SAFE_FCNTL(fds[1], F_SETFL, flags & ~O_NONBLOCK);
+
+	flags = SAFE_FCNTL(fds[1], F_GETFL);
+
+	if (flags & O_NONBLOCK)
+		tst_res(TFAIL, "O_NONBLOCK flag must not be set.");
+
+	pid = SAFE_FORK();
+
+	/*
+	 * Since writes are now blocking the child must wait forever on this
+	 * write.
+	 */
+	if (!pid)
+		SAFE_WRITE(1, fds[1], buf, page_size);
+
+	if (TST_PROCESS_STATE_WAIT(pid, 'S', 1000))
+		tst_res(TFAIL, "Child must be stopped.");
+	else
+		tst_res(TPASS, "Child is stopped.");
+
+	SAFE_KILL(pid, SIGKILL);
+
+	SAFE_WAIT(&status);
+}
+
+static void cleanup(void)
+{
+	for (int i = 0; i < 2; i++)
+		if (fds[i] > 0)
+			SAFE_CLOSE(fds[i]);
+}
+
+static struct tst_test test = {
+	.test_all = test_pipe2,
+	.setup = setup,
+	.cleanup = cleanup,
+	.forks_child = 1,
+};
\ No newline at end of file
-- 
2.20.1