Implement the stats for the image_fs_info command

Signed-off-by: Bo Zhao <bzhao@lyft.com>

utils/filesystem.go

@@ -0,0 +1,109 @@
+package utils
+
+import (
+	"fmt"
+	"golang.org/x/sys/unix"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"syscall"
+
+	"github.com/docker/docker/pkg/mount"
+)
+
+// GetDiskUsageStats accepts a path to a directory or file
+// and returns the number of bytes and inodes used by the path
+func GetDiskUsageStats(path string) (uint64, uint64, error) {
+	var dirSize, inodeCount uint64
+
+	err := filepath.Walk(path, func(path string, info os.FileInfo, err error) error {
+		fileStat, error := os.Lstat(path)
+		if error != nil {
+			if fileStat.Mode()&os.ModeSymlink != 0 {
+				// Is a symlink; no error should be returned
+				return nil
+			}
+			return error
+		}
+
+		dirSize += uint64(info.Size())
+		inodeCount++
+
+		return nil
+	})
+
+	if err != nil {
+		return 0, 0, err
+	}
+
+	return dirSize, inodeCount, err
+}
+
+// GetDeviceUUIDFromPath accepts a path, and will find the device
+// corresponding to the path and return the UUID of that device
+func GetDeviceUUIDFromPath(devicePath string) (string, error) {
+	const dir = "/dev/disk/by-uuid"
+
+	if _, err := os.Stat(dir); os.IsNotExist(err) {
+		return "", nil
+	}
+
+	files, err := ioutil.ReadDir(dir)
+	if err != nil {
+		return "", err
+	}
+
+	for _, file := range files {
+		path := filepath.Join(dir, file.Name())
+		target, err := os.Readlink(path)
+		if err != nil {
+			continue
+		}
+		device, err := filepath.Abs(filepath.Join(dir, target))
+		if err != nil {
+			return "", fmt.Errorf("failed to resolve the absolute path of %q", filepath.Join(dir, target))
+		}
+		if strings.Compare(device, devicePath) == 0 {
+			return file.Name(), nil
+		}
+	}
+
+	return "", fmt.Errorf("device path %s not found", devicePath)
+}
+
+// GetStattFromPath is a helper function that returns the Stat_t
+// object for a given path
+func GetStattFromPath(path string) (syscall.Stat_t, error) {
+	statInfo := syscall.Stat_t{}
+	err := syscall.Lstat(path, &statInfo)
+	if err != nil {
+		return statInfo, err
+	}
+	return statInfo, nil
+}
+
+// GetDeviceNameFromPath iterates through the mounts and matches
+// the one that the provided path is on
+func GetDeviceNameFromPath(path string) (string, error) {
+	statInfo, err := GetStattFromPath(path)
+	if err != nil {
+		return "", err
+	}
+
+	mounts, err := mount.GetMounts()
+	if err != nil {
+		return "", err
+	}
+
+	queryMajor := int(unix.Major(uint64(statInfo.Dev)))
+	queryMinor := int(unix.Minor(uint64(statInfo.Dev)))
+
+	for _, mount := range mounts {
+		if mount.Minor == queryMinor && mount.Major == queryMajor {
+			return mount.Source, nil
+		}
+	}
+
+	return "", fmt.Errorf("no match found")
+}