Initial commit

vendor/github.com/hyperhq/hypercli/pkg/loopback/loopback.go

@@ -0,0 +1,63 @@
+// +build linux
+
+package loopback
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+
+	"github.com/Sirupsen/logrus"
+)
+
+func getLoopbackBackingFile(file *os.File) (uint64, uint64, error) {
+	loopInfo, err := ioctlLoopGetStatus64(file.Fd())
+	if err != nil {
+		logrus.Errorf("Error get loopback backing file: %s", err)
+		return 0, 0, ErrGetLoopbackBackingFile
+	}
+	return loopInfo.loDevice, loopInfo.loInode, nil
+}
+
+// SetCapacity reloads the size for the loopback device.
+func SetCapacity(file *os.File) error {
+	if err := ioctlLoopSetCapacity(file.Fd(), 0); err != nil {
+		logrus.Errorf("Error loopbackSetCapacity: %s", err)
+		return ErrSetCapacity
+	}
+	return nil
+}
+
+// FindLoopDeviceFor returns a loopback device file for the specified file which
+// is backing file of a loop back device.
+func FindLoopDeviceFor(file *os.File) *os.File {
+	stat, err := file.Stat()
+	if err != nil {
+		return nil
+	}
+	targetInode := stat.Sys().(*syscall.Stat_t).Ino
+	targetDevice := stat.Sys().(*syscall.Stat_t).Dev
+
+	for i := 0; true; i++ {
+		path := fmt.Sprintf("/dev/loop%d", i)
+
+		file, err := os.OpenFile(path, os.O_RDWR, 0)
+		if err != nil {
+			if os.IsNotExist(err) {
+				return nil
+			}
+
+			// Ignore all errors until the first not-exist
+			// we want to continue looking for the file
+			continue
+		}
+
+		dev, inode, err := getLoopbackBackingFile(file)
+		if err == nil && dev == targetDevice && inode == targetInode {
+			return file
+		}
+		file.Close()
+	}
+
+	return nil
+}