[LTP] [PATCH v2 3/3] cgroups: Add first IO controller test

[Richard Palethorpe]

In V1 there is the blkio controller. This was renamed to just io on
V2. The interface and functionality is significantly
different. Presently there do not appear to be any tests for the V2
controller.

Note that one can not simply stat a file on BTRFS to find the actual
block device the filesystem is using. Nor can you read
/proc/self/mountinfo. BTRFS seems to generate "anonymous"
devices (e.g. 0:27) and this is what is reported by stat. These
however are invisible to the IO controller.

So instead we have to look in /proc/mounts for the device path then
stat the special (/dev/<device>) file to get the actual major and
minor device number.

Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
---
 runtest/controllers                           |   3 +
 testcases/kernel/controllers/io/.gitignore    |   1 +
 testcases/kernel/controllers/io/Makefile      |   6 +
 .../kernel/controllers/io/io_control01.c      | 155 ++++++++++++++++++
 4 files changed, 165 insertions(+)
 create mode 100644 testcases/kernel/controllers/io/.gitignore
 create mode 100644 testcases/kernel/controllers/io/Makefile
 create mode 100644 testcases/kernel/controllers/io/io_control01.c

diff --git a/runtest/controllers b/runtest/controllers
index 3108a2561..22d482050 100644
--- a/runtest/controllers
+++ b/runtest/controllers
@@ -360,6 +360,9 @@ cpuset_regression_test cpuset_regression_test.sh
 
 cgroup_xattr	cgroup_xattr
 
+# V2 IO controller (was blkio)
+io_control01 io_control01
+
 pids_1_1 pids.sh 1 1 0
 pids_1_2 pids.sh 1 2 0
 pids_1_10 pids.sh 1 10 0
diff --git a/testcases/kernel/controllers/io/.gitignore b/testcases/kernel/controllers/io/.gitignore
new file mode 100644
index 000000000..d626fa80d
--- /dev/null
+++ b/testcases/kernel/controllers/io/.gitignore
@@ -0,0 +1 @@
+io_control01
diff --git a/testcases/kernel/controllers/io/Makefile b/testcases/kernel/controllers/io/Makefile
new file mode 100644
index 000000000..5ea7d67db
--- /dev/null
+++ b/testcases/kernel/controllers/io/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+top_srcdir		?= ../../../..
+
+include $(top_srcdir)/include/mk/testcases.mk
+include $(top_srcdir)/include/mk/generic_leaf_target.mk
diff --git a/testcases/kernel/controllers/io/io_control01.c b/testcases/kernel/controllers/io/io_control01.c
new file mode 100644
index 000000000..a6bf01639
--- /dev/null
+++ b/testcases/kernel/controllers/io/io_control01.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0
+/*\
+ *
+ * [Description]
+ *
+ * Perform some I/O on a file and check if at least some of it is
+ * recorded by the I/O controller.
+ *
+ * The exact amount of I/O performed is dependent on the file system,
+ * page cache, scheduler and block driver. We call sync and drop the
+ * file's page cache to force reading and writing. We also write
+ * random data to try to prevent compression.
+ *
+ * The pagecache is a particular issue for reading. If the call to
+ * fadvise is ignored then the data may only be read from the
+ * cache. So that no I/O requests are made.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/sysmacros.h>
+
+#include "tst_test.h"
+
+struct io_stats {
+	unsigned int mjr;
+	unsigned int mnr;
+	unsigned long rbytes;
+	unsigned long wbytes;
+	unsigned long rios;
+	unsigned long wios;
+	unsigned long dbytes;
+	unsigned long dios;
+};
+
+static unsigned int dev_major, dev_minor;
+
+static int read_io_stats(const char *const line, struct io_stats *const stat)
+{
+	return sscanf(line,
+		      "%u:%u rbytes=%lu wbytes=%lu rios=%lu wios=%lu dbytes=%lu dios=%lu",
+		      &stat->mjr, &stat->mnr,
+		      &stat->rbytes, &stat->wbytes, &stat->rios, &stat->wios,
+		      &stat->dbytes, &stat->dios);
+}
+
+static void run(void)
+{
+	int i, fd;
+	char *line, *buf_ptr;
+	const size_t pgsz = SAFE_SYSCONF(_SC_PAGESIZE);
+	char *buf = SAFE_MALLOC(MAX((size_t)BUFSIZ, pgsz));
+	struct io_stats start;
+
+	SAFE_CG_READ(tst_cg, "io.stat", buf, BUFSIZ - 1);
+	line = strtok_r(buf, "\n", &buf_ptr);
+	while (line) {
+		const int convs = read_io_stats(line, &start);
+
+		if (convs < 2)
+			continue;
+
+		tst_res(TINFO, "Found %u:%u in io.stat", dev_major, dev_minor);
+
+		if (start.mjr == dev_major || start.mnr == dev_minor)
+			break;
+
+		line = strtok_r(NULL, "\n", &buf_ptr);
+	}
+
+	SAFE_CG_PRINTF(tst_cg, "cgroup.procs", "%d", getpid());
+
+	fd = SAFE_OPEN("/dev/urandom", O_RDONLY, 0600);
+	SAFE_READ(1, fd, buf, pgsz);
+	SAFE_CLOSE(fd);
+
+	fd = SAFE_OPEN("mnt/dat", O_WRONLY | O_CREAT, 0600);
+
+	for (i = 0; i < 4; i++) {
+		SAFE_WRITE(1, fd, buf, pgsz);
+		SAFE_FSYNC(fd);
+		TST_EXP_PASS_SILENT(posix_fadvise(fd, pgsz * i, pgsz, POSIX_FADV_DONTNEED));
+	}
+
+	SAFE_CLOSE(fd);
+	fd = SAFE_OPEN("mnt/dat", O_RDONLY, 0600);
+
+	for (i = 0; i < 4; i++)
+		SAFE_READ(1, fd, buf, pgsz);
+
+	tst_res(TPASS, "Did some IO in the IO controller");
+
+	SAFE_CG_READ(tst_cg, "io.stat", buf, BUFSIZ - 1);
+	line = strtok_r(buf, "\n", &buf_ptr);
+	while (line) {
+		struct io_stats end;
+		const int convs = read_io_stats(line, &end);
+
+		if (convs < 8)
+			break;
+
+		if (end.mjr != dev_major || end.mnr != dev_minor) {
+			line = strtok_r(NULL, "\n", &buf_ptr);
+			continue;
+		}
+
+		tst_res(TPASS, "Found %u:%u in io.stat", dev_major, dev_minor);
+		TST_EXP_EXPR(end.rbytes > start.rbytes,
+			     "(rbytes=%lu) > (st_rbytes=%lu)",
+			     end.rbytes, start.rbytes);
+		TST_EXP_EXPR(end.wbytes > start.wbytes,
+			     "(wbytes=%lu) > (st_wbytes=%lu)",
+			     end.wbytes, start.wbytes);
+		TST_EXP_EXPR(end.rios > start.rios,
+			     "(rios=%lu) > (st_rios=%lu)",
+			     end.rios, start.rios);
+		TST_EXP_EXPR(end.wios > start.wios,
+			     "(wios=%lu) > (st_wios=%lu)",
+			     end.wios, start.wios);
+
+		goto out;
+	}
+
+	tst_res(TINFO, "io.stat:\n%s", buf);
+	tst_res(TFAIL, "Did not find %u:%u in io.stat", dev_major, dev_minor);
+out:
+	free(buf);
+	SAFE_CLOSE(fd);
+	SAFE_UNLINK("mnt/dat");
+}
+
+static void setup(void)
+{
+	char buf[PATH_MAX] = { 0 };
+	char *path = SAFE_GETCWD(buf, PATH_MAX - sizeof("mnt") - 1);
+	struct stat st;
+
+	strcpy(path + strlen(path), "/mnt");
+
+	tst_stat_mount_dev(path, &st);
+	dev_major = major(st.st_rdev);
+	dev_minor = minor(st.st_rdev);
+}
+
+static struct tst_test test = {
+	.test_all = run,
+	.setup = setup,
+	.needs_device = 1,
+	.mntpoint = "mnt",
+	.mount_device = 1,
+	.all_filesystems = 1,
+	.skip_filesystems = (const char *const[]){ "ntfs", "tmpfs", NULL },
+	.needs_cgroup_ver = TST_CG_V2,
+	.needs_cgroup_ctrls = (const char *const[]){ "io", NULL },
+};
-- 
2.35.1