Ensure minimum kernel version for thin_ls

Ensure that kernel >= 4.4.0 or RHEL/Centos 7 kernel >= 3.10.0-366 exists before starting the thin
pool watcher. Prior versions have a bug in which reserving and releasing the metadata snapshot can
cause thin pool corruption.

container/docker/factory.go

@@ -19,9 +19,12 @@ import (
 	"fmt"
 	"path"
 	"regexp"
+	"strconv"
 	"strings"
 	"sync"
+	"syscall"
 
+	"github.com/blang/semver"
 	dockertypes "github.com/docker/engine-api/types"
 	"github.com/google/cadvisor/container"
 	"github.com/google/cadvisor/container/libcontainer"
@@ -178,6 +181,14 @@ func startThinPoolWatcher(dockerInfo *dockertypes.Info) (*devicemapper.ThinPoolW
 		return nil, err
 	}
 
+	kernelVersion, err := getKernelVersion()
+	if err != nil {
+		return nil, err
+	}
+	if err := ensureThinLsKernelVersion(kernelVersion); err != nil {
+		return nil, err
+	}
+
 	dockerThinPoolName, err := dockerutil.DockerThinPoolName(*dockerInfo)
 	if err != nil {
 		return nil, err
@@ -197,6 +208,80 @@ func startThinPoolWatcher(dockerInfo *dockertypes.Info) (*devicemapper.ThinPoolW
 	return thinPoolWatcher, nil
 }
 
+func getKernelVersion() (string, error) {
+	unameOutput := syscall.Utsname{}
+	err := syscall.Uname(&unameOutput)
+	if err != nil {
+		return "", err
+	}
+
+	b := make([]byte, len(unameOutput.Release))
+	for i, v := range unameOutput.Release {
+		b[i] = byte(v)
+	}
+	return string(b), nil
+}
+
+func ensureThinLsKernelVersion(kernelVersion string) error {
+	// kernel 4.4.0 has the proper bug fixes to allow thin_ls to work without corrupting the thin pool
+	version_4_4_0 := semver.MustParse("4.4.0")
+	// RHEL kernel 3.10.0 release >= 366 has the proper bug fixes backported from 4.4.0 to allow
+	// thin_ls to work without corrupting the thin pool
+	version_3_10_0 := semver.MustParse("3.10.0")
+
+	matches := version_re.FindStringSubmatch(kernelVersion)
+	if len(matches) < 4 {
+		return fmt.Errorf("error parsing kernel version %q: expected 4 matches, got %d", kernelVersion, len(matches))
+	}
+
+	sem, err := semver.Make(matches[0])
+	if err != nil {
+		return err
+	}
+
+	if sem.GTE(version_4_4_0) {
+		// kernel 4.4+ - good
+		return nil
+	}
+
+	// Certain RHEL/Centos 7.x kernels have a backport to fix the corruption bug
+	if !strings.Contains(kernelVersion, ".el7.") {
+		// not a RHEL 7.x kernel - won't work
+		return fmt.Errorf("kernel version 4.4.0 or later is required to use thin_ls - you have %q", kernelVersion)
+	}
+
+	// RHEL/Centos 7.x from here on
+	if sem.Major != 3 {
+		// only 3.x kernels *may* work correctly
+		return fmt.Errorf("RHEL/Centos 7.x kernel version 3.10.0-366 or later is required to use thin_ls - you have %q", kernelVersion)
+	}
+
+	if sem.GT(version_3_10_0) {
+		// 3.10.1+ - good
+		return nil
+	}
+
+	if sem.EQ(version_3_10_0) {
+		// need to check release
+		releaseRE := regexp.MustCompile(`^[^-]+-([^.]+)\.`)
+		releaseMatches := releaseRE.FindStringSubmatch(kernelVersion)
+		if len(releaseMatches) != 2 {
+			return fmt.Errorf("unable to determine RHEL/Centos 7.x kernel release from %q", kernelVersion)
+		}
+
+		release, err := strconv.Atoi(releaseMatches[1])
+		if err != nil {
+			return fmt.Errorf("error parsing release %q: %v", releaseMatches[1], err)
+		}
+
+		if release >= 366 {
+			return nil
+		}
+	}
+
+	return fmt.Errorf("RHEL/Centos 7.x kernel version 3.10.0-366 or later is required to use thin_ls - you have %q", kernelVersion)
+}
+
 // Register root container before running this function!
 func Register(factory info.MachineInfoFactory, fsInfo fs.FsInfo, ignoreMetrics container.MetricSet) error {
 	client, err := Client()

container/docker/factory_test.go

@@ -0,0 +1,47 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package docker
+
+import "testing"
+
+func TestEnsureThinLsKernelVersion(t *testing.T) {
+	tests := []struct {
+		version string
+		ok      bool
+	}{
+		{"4.4.0-31-generic", true},
+		{"4.4.1", true},
+		{"4.6.4-301.fc24.x86_64", true},
+		{"3.10.0-327.22.2.el7.x86_64", false},
+		{"3.10.0-366.el7.x86_64", true},
+		{"3.10.0.el7.abc", false},
+		{"3.10.0-abc.el7.blarg", false},
+		{"3.10.0-367.el7.x86_64", true},
+		{"3.10.0-366.x86_64", false},
+		{"3.10.1-1.el7.x86_64", true},
+		{"2.0.36", false},
+		{"2.1", false},
+		{"4.0.0.el7.x86_64", false},
+	}
+
+	for _, test := range tests {
+		err := ensureThinLsKernelVersion(test.version)
+		if err != nil && test.ok {
+			t.Errorf("%s: expected no error, got %v", test.version, err)
+		} else if err == nil && !test.ok {
+			t.Errorf("%s: expected an error", test.version)
+		}
+	}
+}