lxd/instance/drivers/lxc: detect if we need to remove a target direct…

…ory when unmounting

When a disk device is removed while relying on a host directory and mapped to a target within a container,
we detect if the target directory has been created by LXD or not in order to not delete the content of a target
directory during the unmount.

Example:

- Let say we mounted a custom host empty directory (`test`) on the existing `/opt` directory of the container,
when unmounted (`lxc device remove ...`), the target `/opt` won't be removed, because we marked it as NOT being created
by LXD at mount time.

- If, however, we created a custom empty target directory at mount time:
`lxc config device add u1 test disk source=/home/user/test path=/new_dir`,
the directory `new_dir` will be created on the target instance and if we decide to unmount `test`,
the target `/new_dir` will be removed because is has been created by LXD

Signed-off-by: Gabriel Mougard <[email protected]>

lxd/instance/drivers/driver_lxc.go

@@ -1713,10 +1713,29 @@ func (d *lxc) deviceHandleMounts(mounts []deviceConfig.MountEntryItem) error {
 				}
 			}
 
+			// If the mount is a directory, create the LXD marker file.
+			if shared.IsDir(mount.DevPath) {
+				// Connect to files API.
+				files, err := d.FileSFTP()
+				if err != nil {
+					return err
+				}
+
+				defer func() { _ = files.Close() }()
+
+				_, err = files.Lstat(mount.TargetPath)
+				if err != nil {
+					err = d.deviceVolatileSetFunc(mount.DevName)(map[string]string{"last_state.created_path": mount.TargetPath})
+					if err != nil {
+						return fmt.Errorf("Error updating volatile for the device: %w", err)
+					}
+				}
+			}
+
 			// Mount it into the container.
 			err := d.insertMount(mount.DevPath, mount.TargetPath, mount.FSType, flags, idmapType)
 			if err != nil {
-				return fmt.Errorf("Failed to add mount for device inside container: %s", err)
+				return fmt.Errorf("Failed to add mount for device inside container: %w", err)
 			}
 		} else {
 			relativeTargetPath := strings.TrimPrefix(mount.TargetPath, "/")
@@ -1731,17 +1750,36 @@ func (d *lxc) deviceHandleMounts(mounts []deviceConfig.MountEntryItem) error {
 
 			_, err = files.Lstat(relativeTargetPath)
 			if err == nil {
-				err := d.removeMount(mount.TargetPath)
-				if err != nil {
-					return fmt.Errorf("Error unmounting the device path inside container: %s", err)
+				removeTargetFiles := false
+
+				// Check if the target path hasn't been created by LXD
+				mountConf := d.deviceVolatileGetFunc(mount.DevName)()
+				for k, v := range mountConf {
+					if k == "last_state.created_path" && v == mount.TargetPath {
+						removeTargetFiles = true
+						break
+					}
 				}
 
-				err = files.Remove(relativeTargetPath)
+				err = d.removeMount(mount.TargetPath)
 				if err != nil {
-					// Only warn here and don't fail as removing a directory
-					// mount may fail if there was already files inside
-					// directory before it was mouted over preventing delete.
-					d.logger.Warn("Could not remove the device path inside container", logger.Ctx{"err": err})
+					return fmt.Errorf("Error unmounting the device path inside container: %w", err)
+				}
+
+				if removeTargetFiles {
+					err = files.Remove(relativeTargetPath)
+					if err != nil {
+						// Only warn here and don't fail as removing a directory
+						// mount may fail if there was already files inside
+						// directory before it was mouted over preventing delete.
+						d.logger.Warn("Could not remove the device path inside container", logger.Ctx{"err": err})
+					}
+				} else {
+					// Remove option from the mount.
+					err = d.deviceVolatileSetFunc(mount.DevName)(map[string]string{"last_state.created_path": ""})
+					if err != nil {
+						return fmt.Errorf("Error updating volatile for the device: %w", err)
+					}
 				}
 			}
 		}