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-rw-r--r--libpod/volume_internal_linux.go128
1 files changed, 128 insertions, 0 deletions
diff --git a/libpod/volume_internal_linux.go b/libpod/volume_internal_linux.go
new file mode 100644
index 000000000..9ae4dcf69
--- /dev/null
+++ b/libpod/volume_internal_linux.go
@@ -0,0 +1,128 @@
+// +build linux
+
+package libpod
+
+import (
+ "io/ioutil"
+ "os/exec"
+
+ "github.com/pkg/errors"
+ "github.com/sirupsen/logrus"
+ "golang.org/x/sys/unix"
+)
+
+// mount mounts the volume if necessary.
+// A mount is necessary if a volume has any options set.
+// If a mount is necessary, v.state.MountCount will be incremented.
+// If it was 0 when the increment occurred, the volume will be mounted on the
+// host. Otherwise, we assume it is already mounted.
+// Must be done while the volume is locked.
+// Is a no-op on volumes that do not require a mount (as defined by
+// volumeNeedsMount())
+func (v *Volume) mount() error {
+ if !v.needsMount() {
+ return nil
+ }
+
+ // Update the volume from the DB to get an accurate mount counter.
+ if err := v.update(); err != nil {
+ return err
+ }
+
+ // If the count is non-zero, the volume is already mounted.
+ // Nothing to do.
+ if v.state.MountCount > 0 {
+ v.state.MountCount = v.state.MountCount + 1
+ logrus.Debugf("Volume %s mount count now at %d", v.Name(), v.state.MountCount)
+ return v.save()
+ }
+
+ volDevice := v.config.Options["device"]
+ volType := v.config.Options["type"]
+ volOptions := v.config.Options["o"]
+
+ // Some filesystems (tmpfs) don't have a device, but we still need to
+ // give the kernel something.
+ if volDevice == "" && volType != "" {
+ volDevice = volType
+ }
+
+ // We need to use the actual mount command.
+ // Convincing unix.Mount to use the same semantics as the mount command
+ // itself seems prohibitively difficult.
+ // TODO: might want to cache this path in the runtime?
+ mountPath, err := exec.LookPath("mount")
+ if err != nil {
+ return errors.Wrapf(err, "error locating 'mount' binary")
+ }
+ mountArgs := []string{}
+ if volOptions != "" {
+ mountArgs = append(mountArgs, "-o", volOptions)
+ }
+ if volType != "" {
+ mountArgs = append(mountArgs, "-t", volType)
+ }
+ mountArgs = append(mountArgs, volDevice, v.config.MountPoint)
+ mountCmd := exec.Command(mountPath, mountArgs...)
+
+ errPipe, err := mountCmd.StderrPipe()
+ if err != nil {
+ return errors.Wrapf(err, "error getting stderr pipe for mount")
+ }
+ if err := mountCmd.Start(); err != nil {
+ out, err2 := ioutil.ReadAll(errPipe)
+ if err2 != nil {
+ return errors.Wrapf(err2, "error reading mount STDERR")
+ }
+ return errors.Wrapf(errors.New(string(out)), "error mounting volume %s", v.Name())
+ }
+
+ logrus.Debugf("Mounted volume %s", v.Name())
+
+ // Increment the mount counter
+ v.state.MountCount = v.state.MountCount + 1
+ logrus.Debugf("Volume %s mount count now at %d", v.Name(), v.state.MountCount)
+ return v.save()
+}
+
+// unmount unmounts the volume if necessary.
+// Unmounting a volume that is not mounted is a no-op.
+// Unmounting a volume that does not require a mount is a no-op.
+// The volume must be locked for this to occur.
+// The mount counter will be decremented if non-zero. If the counter reaches 0,
+// the volume will really be unmounted, as no further containers are using the
+// volume.
+// If force is set, the volume will be unmounted regardless of mount counter.
+func (v *Volume) unmount(force bool) error {
+ if !v.needsMount() {
+ return nil
+ }
+
+ // Update the volume from the DB to get an accurate mount counter.
+ if err := v.update(); err != nil {
+ return err
+ }
+
+ if v.state.MountCount == 0 {
+ logrus.Debugf("Volume %s already unmounted", v.Name())
+ return nil
+ }
+
+ if !force {
+ v.state.MountCount = v.state.MountCount - 1
+ } else {
+ v.state.MountCount = 0
+ }
+
+ logrus.Debugf("Volume %s mount count now at %d", v.Name(), v.state.MountCount)
+
+ if v.state.MountCount == 0 {
+ // Unmount the volume
+ if err := unix.Unmount(v.config.MountPoint, unix.MNT_DETACH); err != nil {
+ return errors.Wrapf(err, "error unmounting volume %s", v.Name())
+ }
+ logrus.Debugf("Unmounted volume %s", v.Name())
+ }
+
+ return v.save()
+}