1 files changed, 194 insertions, 0 deletions
diff --git a/libpod/volume_internal_common.go b/libpod/volume_internal_common.go
new file mode 100644
index 000000000..440bceec3
--- /dev/null
+++ b/libpod/volume_internal_common.go
@@ -0,0 +1,194 @@
+//go:build linux
+// +build linux
+
+package libpod
+
+import (
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+
+	"github.com/containers/podman/v4/libpod/define"
+	pluginapi "github.com/docker/go-plugins-helpers/volume"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+// This is a pseudo-container ID to use when requesting a mount or unmount from
+// the volume plugins.
+// This is the shas256 of the string "placeholder\n".
+const pseudoCtrID = "2f73349cfc4630255319c6c8dfc1b46a8996ace9d14d8e07563b165915918ec2"
+
+// 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++
+		logrus.Debugf("Volume %s mount count now at %d", v.Name(), v.state.MountCount)
+		return v.save()
+	}
+
+	// Volume plugins implement their own mount counter, based on the ID of
+	// the mounting container. But we already have one, and honestly I trust
+	// ours more. So hardcode container ID to something reasonable, and use
+	// the same one for everything.
+	if v.UsesVolumeDriver() {
+		if v.plugin == nil {
+			return fmt.Errorf("volume plugin %s (needed by volume %s) missing: %w", v.Driver(), v.Name(), define.ErrMissingPlugin)
+		}
+
+		req := new(pluginapi.MountRequest)
+		req.Name = v.Name()
+		req.ID = pseudoCtrID
+		mountPoint, err := v.plugin.MountVolume(req)
+		if err != nil {
+			return err
+		}
+
+		v.state.MountCount++
+		v.state.MountPoint = mountPoint
+		return v.save()
+	} else if v.config.Driver == define.VolumeDriverImage {
+		mountPoint, err := v.runtime.storageService.MountContainerImage(v.config.StorageID)
+		if err != nil {
+			return fmt.Errorf("mounting volume %s image failed: %w", v.Name(), err)
+		}
+
+		v.state.MountCount++
+		v.state.MountPoint = mountPoint
+		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 fmt.Errorf("locating 'mount' binary: %w", err)
+	}
+	mountArgs := []string{}
+	if volOptions != "" {
+		mountArgs = append(mountArgs, "-o", volOptions)
+	}
+	switch volType {
+	case "":
+	case "bind":
+		mountArgs = append(mountArgs, "-o", volType)
+	default:
+		mountArgs = append(mountArgs, "-t", volType)
+	}
+
+	mountArgs = append(mountArgs, volDevice, v.config.MountPoint)
+	mountCmd := exec.Command(mountPath, mountArgs...)
+
+	logrus.Debugf("Running mount command: %s %s", mountPath, strings.Join(mountArgs, " "))
+	if output, err := mountCmd.CombinedOutput(); err != nil {
+		logrus.Debugf("Mount %v failed with %v", mountCmd, err)
+		return errors.New(string(output))
+	}
+
+	logrus.Debugf("Mounted volume %s", v.Name())
+
+	// Increment the mount counter
+	v.state.MountCount++
+	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--
+	} else {
+		v.state.MountCount = 0
+	}
+
+	logrus.Debugf("Volume %s mount count now at %d", v.Name(), v.state.MountCount)
+
+	if v.state.MountCount == 0 {
+		if v.UsesVolumeDriver() {
+			if v.plugin == nil {
+				return fmt.Errorf("volume plugin %s (needed by volume %s) missing: %w", v.Driver(), v.Name(), define.ErrMissingPlugin)
+			}
+
+			req := new(pluginapi.UnmountRequest)
+			req.Name = v.Name()
+			req.ID = pseudoCtrID
+			if err := v.plugin.UnmountVolume(req); err != nil {
+				return err
+			}
+
+			v.state.MountPoint = ""
+			return v.save()
+		} else if v.config.Driver == define.VolumeDriverImage {
+			if _, err := v.runtime.storageService.UnmountContainerImage(v.config.StorageID, force); err != nil {
+				return fmt.Errorf("unmounting volume %s image: %w", v.Name(), err)
+			}
+
+			v.state.MountPoint = ""
+			return v.save()
+		}
+
+		// Unmount the volume
+		if err := unix.Unmount(v.config.MountPoint, unix.MNT_DETACH); err != nil {
+			if err == unix.EINVAL {
+				// Ignore EINVAL - the mount no longer exists.
+				return nil
+			}
+			return fmt.Errorf("unmounting volume %s: %w", v.Name(), err)
+		}
+		logrus.Debugf("Unmounted volume %s", v.Name())
+	}
+
+	return v.save()
+}