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// +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()
}
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