[LTP] [PATCH v2] syscalls/write06: Add new test

[Dai Shili]

Like pwrite04.c, test the write() system call with O_APPEND.

Signed-off-by: Dai Shili <daisl.fnst@fujitsu.com>
---
 runtest/syscalls                           |  1 +
 testcases/kernel/syscalls/write/.gitignore |  1 +
 testcases/kernel/syscalls/write/write06.c  | 95 ++++++++++++++++++++++++++++++
 3 files changed, 97 insertions(+)
 create mode 100644 testcases/kernel/syscalls/write/write06.c

diff --git a/runtest/syscalls b/runtest/syscalls
index bcf3d56..32fcda4 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -1699,6 +1699,7 @@ write02 write02
 write03 write03
 write04 write04
 write05 write05
+write06 write06
 
 writev01 writev01
 writev02 writev02
diff --git a/testcases/kernel/syscalls/write/.gitignore b/testcases/kernel/syscalls/write/.gitignore
index 7f36194..8529aae 100644
--- a/testcases/kernel/syscalls/write/.gitignore
+++ b/testcases/kernel/syscalls/write/.gitignore
@@ -3,3 +3,4 @@
 /write03
 /write04
 /write05
+/write06
diff --git a/testcases/kernel/syscalls/write/write06.c b/testcases/kernel/syscalls/write/write06.c
new file mode 100644
index 0000000..ea30d73
--- /dev/null
+++ b/testcases/kernel/syscalls/write/write06.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2021 FUJITSU LIMITED. All rights reserved.
+ * Author: Dai Shili <daisl.fnst@fujitsu.com>
+ */
+
+/*\
+ * [Description]
+ *
+ * Test the write() system call with O_APPEND.
+ *
+ * The full description of O_APPEND is in open(2) man-pages:
+ * O_APPEND
+ *        The file is opened in append mode.  Before each write(2), the
+ * file offset is positioned at the end of the file, as if with lseek(2).
+ * The modification of the file offset and the write operation are
+ * performed as a single atomic step.
+ *
+ * Writing 2k data to the file, close it and reopen it with O_APPEND.
+ * Verify that the file size is 3k and offset is moved to the end of the file.
+ */
+
+#include <stdlib.h>
+#include <inttypes.h>
+#include "tst_test.h"
+#include "tst_safe_prw.h"
+
+#define K1              1024
+#define K2              (K1 * 2)
+#define K3              (K1 * 3)
+#define DATA_FILE       "write06_file"
+
+static int fd = -1;
+static char *write_buf[2];
+
+static void verify_write(void)
+{
+	off_t off;
+	struct stat statbuf;
+
+	fd = SAFE_OPEN(DATA_FILE, O_RDWR | O_CREAT | O_TRUNC);
+	SAFE_WRITE(1, fd, write_buf[0], K2);
+	SAFE_CLOSE(fd);
+
+	fd = SAFE_OPEN(DATA_FILE, O_RDWR | O_APPEND);
+	SAFE_FSTAT(fd, &statbuf);
+	if (statbuf.st_size != K2)
+		tst_res(TFAIL, "file size is %ld != K2", statbuf.st_size);
+
+	off = SAFE_LSEEK(fd, K1, SEEK_SET);
+	if (off != K1)
+		tst_brk(TBROK, "Failed to seek to K1");
+
+	SAFE_WRITE(1, fd, write_buf[1], K1);
+
+	off = SAFE_LSEEK(fd, 0, SEEK_CUR);
+	if (off != K3)
+		tst_res(TFAIL, "Wrong offset after write %zu expected %u", off, K3);
+	else
+		tst_res(TPASS, "Offset is correct after write %zu", off);
+
+	SAFE_FSTAT(fd, &statbuf);
+	if (statbuf.st_size != K3)
+		tst_res(TFAIL, "Wrong file size after append %zu expected %u", statbuf.st_size, K3);
+	else
+		tst_res(TPASS, "Correct file size after append %u", K3);
+
+	SAFE_CLOSE(fd);
+}
+
+static void setup(void)
+{
+	memset(write_buf[0], 0, K2);
+	memset(write_buf[1], 1, K1);
+}
+
+static void cleanup(void)
+{
+	if (fd != -1)
+		SAFE_CLOSE(fd);
+
+	SAFE_UNLINK(DATA_FILE);
+}
+
+static struct tst_test test = {
+	.needs_tmpdir = 1,
+	.setup = setup,
+	.cleanup = cleanup,
+	.test_all = verify_write,
+	.bufs = (struct tst_buffers[]) {
+		{&write_buf[0], .size = K2},
+		{&write_buf[1], .size = K1},
+		{}
+	}
+};
-- 
1.8.3.1