test/e2e: Use nullb0 for IO limit tests

The tests for device I/O limits were using `/dev/zero`,
which is not a block device suitable for these cgroup
controls.

Update the tests to use `/dev/nullb0` if it exists.

Signed-off-by: Giuseppe Scrivano <[email protected]>

Author: giuseppe

test/e2e/common_test.go

@@ -942,6 +942,13 @@ func SkipIfNotRootless(reason string) {
 	}
 }
 
+func SkipIfNotExist(reason, path string) {
+	checkReason(reason)
+	if _, err := os.Stat(path); err != nil {
+		Skip("[doesNotExist]: " + path + " does not exist: " + reason)
+	}
+}
+
 func SkipIfSystemdNotRunning(reason string) {
 	checkReason(reason)
 
@@ -1648,3 +1655,7 @@ func makeTempDirInDir(dir string) string {
 	Expect(err).ToNot(HaveOccurred())
 	return path
 }
+
+func skipWithoutDevNullb0() {
+	SkipIfNotExist("use modprobe null_blk nr_devices=1 to create it", "/dev/nullb0")
+}

test/e2e/run_test.go

@@ -848,13 +848,14 @@ USER bin`, BB)
 
 	It("podman run device-read-bps test", func() {
 		SkipIfRootless("Setting device-read-bps not supported for rootless users")
+		skipWithoutDevNullb0()
 
 		var session *PodmanSessionIntegration
 
 		if CGROUPSV2 {
-			session = podmanTest.Podman([]string{"run", "--rm", "--device-read-bps=/dev/zero:1mb", ALPINE, "sh", "-c", "cat /sys/fs/cgroup/$(sed -e 's|0::||' < /proc/self/cgroup)/io.max"})
+			session = podmanTest.Podman([]string{"run", "--rm", "--device-read-bps=/dev/nullb0:1mb", ALPINE, "sh", "-c", "cat /sys/fs/cgroup/$(sed -e 's|0::||' < /proc/self/cgroup)/io.max"})
 		} else {
-			session = podmanTest.Podman([]string{"run", "--rm", "--device-read-bps=/dev/zero:1mb", ALPINE, "cat", "/sys/fs/cgroup/blkio/blkio.throttle.read_bps_device"})
+			session = podmanTest.Podman([]string{"run", "--rm", "--device-read-bps=/dev/nullb0:1mb", ALPINE, "cat", "/sys/fs/cgroup/blkio/blkio.throttle.read_bps_device"})
 		}
 
 		session.WaitWithDefaultTimeout()
@@ -866,13 +867,14 @@ USER bin`, BB)
 
 	It("podman run device-write-bps test", func() {
 		SkipIfRootless("Setting device-write-bps not supported for rootless users")
+		skipWithoutDevNullb0()
 
 		var session *PodmanSessionIntegration
 
 		if CGROUPSV2 {
-			session = podmanTest.Podman([]string{"run", "--rm", "--device-write-bps=/dev/zero:1mb", ALPINE, "sh", "-c", "cat /sys/fs/cgroup/$(sed -e 's|0::||' < /proc/self/cgroup)/io.max"})
+			session = podmanTest.Podman([]string{"run", "--rm", "--device-write-bps=/dev/nullb0:1mb", ALPINE, "sh", "-c", "cat /sys/fs/cgroup/$(sed -e 's|0::||' < /proc/self/cgroup)/io.max"})
 		} else {
-			session = podmanTest.Podman([]string{"run", "--rm", "--device-write-bps=/dev/zero:1mb", ALPINE, "cat", "/sys/fs/cgroup/blkio/blkio.throttle.write_bps_device"})
+			session = podmanTest.Podman([]string{"run", "--rm", "--device-write-bps=/dev/nullb0:1mb", ALPINE, "cat", "/sys/fs/cgroup/blkio/blkio.throttle.write_bps_device"})
 		}
 		session.WaitWithDefaultTimeout()
 		Expect(session).Should(ExitCleanly())
@@ -883,12 +885,14 @@ USER bin`, BB)
 
 	It("podman run device-read-iops test", func() {
 		SkipIfRootless("Setting device-read-iops not supported for rootless users")
+		skipWithoutDevNullb0()
+
 		var session *PodmanSessionIntegration
 
 		if CGROUPSV2 {
-			session = podmanTest.Podman([]string{"run", "--rm", "--device-read-iops=/dev/zero:100", ALPINE, "sh", "-c", "cat /sys/fs/cgroup/$(sed -e 's|0::||' < /proc/self/cgroup)/io.max"})
+			session = podmanTest.Podman([]string{"run", "--rm", "--device-read-iops=/dev/nullb0:100", ALPINE, "sh", "-c", "cat /sys/fs/cgroup/$(sed -e 's|0::||' < /proc/self/cgroup)/io.max"})
 		} else {
-			session = podmanTest.Podman([]string{"run", "--rm", "--device-read-iops=/dev/zero:100", ALPINE, "cat", "/sys/fs/cgroup/blkio/blkio.throttle.read_iops_device"})
+			session = podmanTest.Podman([]string{"run", "--rm", "--device-read-iops=/dev/nullb0:100", ALPINE, "cat", "/sys/fs/cgroup/blkio/blkio.throttle.read_iops_device"})
 		}
 
 		session.WaitWithDefaultTimeout()
@@ -900,12 +904,14 @@ USER bin`, BB)
 
 	It("podman run device-write-iops test", func() {
 		SkipIfRootless("Setting device-write-iops not supported for rootless users")
+		skipWithoutDevNullb0()
+
 		var session *PodmanSessionIntegration
 
 		if CGROUPSV2 {
-			session = podmanTest.Podman([]string{"run", "--rm", "--device-write-iops=/dev/zero:100", ALPINE, "sh", "-c", "cat /sys/fs/cgroup/$(sed -e 's|0::||' < /proc/self/cgroup)/io.max"})
+			session = podmanTest.Podman([]string{"run", "--rm", "--device-write-iops=/dev/nullb0:100", ALPINE, "sh", "-c", "cat /sys/fs/cgroup/$(sed -e 's|0::||' < /proc/self/cgroup)/io.max"})
 		} else {
-			session = podmanTest.Podman([]string{"run", "--rm", "--device-write-iops=/dev/zero:100", ALPINE, "cat", "/sys/fs/cgroup/blkio/blkio.throttle.write_iops_device"})
+			session = podmanTest.Podman([]string{"run", "--rm", "--device-write-iops=/dev/nullb0:100", ALPINE, "cat", "/sys/fs/cgroup/blkio/blkio.throttle.write_iops_device"})
 		}
 
 		session.WaitWithDefaultTimeout()

test/e2e/update_test.go

@@ -87,6 +87,7 @@ var _ = Describe("Podman update", func() {
 	It("podman update container all options v2", func() {
 		SkipIfCgroupV1("testing flags that only work in cgroup v2")
 		SkipIfRootless("many of these handlers are not enabled while rootless in CI")
+		skipWithoutDevNullb0()
 		session := podmanTest.Podman([]string{"run", "-dt", ALPINE})
 		session.WaitWithDefaultTimeout()
 		Expect(session).Should(ExitCleanly())
@@ -103,10 +104,10 @@ var _ = Describe("Podman update", func() {
 			"--memory-swap", "2G",
 			"--memory-reservation", "2G",
 			"--blkio-weight", "123",
-			"--device-read-bps", "/dev/zero:10mb",
-			"--device-write-bps", "/dev/zero:10mb",
-			"--device-read-iops", "/dev/zero:1000",
-			"--device-write-iops", "/dev/zero:1000",
+			"--device-read-bps", "/dev/nullb0:10mb",
+			"--device-write-bps", "/dev/nullb0:10mb",
+			"--device-read-iops", "/dev/nullb0:1000",
+			"--device-write-iops", "/dev/nullb0:1000",
 			"--pids-limit", "123",
 			ctrID}