glusterfs.py文件
cinder/volume/drivers/glusterfs.py就是cinder调用glusterfs的驱动了
glusterfs.py只有一个GlusterfsDriver class，如下图所示
from os_brick.remotefs import remotefs as remotefs_brick # client端操作 from oslo_concurrency import processutils from oslo_config import cfg from oslo_log import log as logging from oslo_utils import fileutils from oslo_utils import units from cinder import exception from cinder.i18n import _, _LE, _LI, _LW from cinder.p_w_picpath import p_w_picpath_utils from cinder import utils from cinder.volume import driver # 很多定义的方法还没具体实现 from cinder.volume.drivers import remotefs as remotefs_drv # 基类 class GlusterfsDriver(remotefs_drv.RemoteFSSnapDriver, driver.CloneableVD, driver.ExtendVD): """Gluster based cinder driver. Creates file on Gluster share for using it as block device on hypervisor. Operations such as create/delete/extend volume/snapshot use locking on a per-process basis to prevent multiple threads from modifying qcow2 chains or the snapshot .info file simultaneously. """
class GlusterfsDriver的父类remotefs_drv.RemoteFSSnapDriver(主要看这个)
cinder/volume/drivers/remotefs.py有两个class，类RemoteFSSnapDriver从类RemoteFSDriver继承
class RemoteFSSnapDriver(RemoteFSDriver, driver.SnapshotVD): """Base class for remotefs drivers implementing qcow2 snapshots. Driver must implement: _local_volume_dir(self, volume) """
类RemoteFSSnapDriver主要是针对volume snapshot的一系列操作。
类RemoteFSDriver可以认为是一个base class，里面定义了很多基本方法
上面提到的class都是关于server端的封装。
client端的封装已经独立为一个项目：os-brick
os_brick/remotefs/remotefs.py，只有一个class RemoteFsClient，右边是类中定义的方法。
cinder后端是glusterfs作为openstack的附加盘来使用，glusterfs本身没有快照机制，云硬盘快照是通过qemu来实现的，代码位置：
cinder做快照的时候，分为两种：
1、volume available的时候，cinder使用qemu-img直接做快照
2、volume in-use的时候，cinder会call nova来完成
cinder/volume/drivers/remotefs.py
qemu-img rebase的作用见这里：http://linux.die.net/man/1/qemu-img
-u是非安全模式，适用于backing-file重命名和移动
简而言之，就是对比backing_filename和旧的backing_filename的差异部分写入new_snap_path
关于Cinder QuiescedSnapshot介绍：
https://specs.openstack.org/openstack/nova-specs/specs/kilo/implemented/quiesced-p_w_picpath-snapshots-with-qemu-guest-agent.html
https://wiki.openstack.org/wiki/Cinder/QuiescedSnapshotWithQemuGuestAgent
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Virtualization_Deployment_and_Administration_Guide/sect-QEMU_Guest_Agent-Using_the_QEMU_guest_virtual_machine_agent_protocol_CLI.html
cinder删除快照的时候，分为两种：
1、volume available的时候，cinder使用qemu-img直接删除快照
2、volume in-use的时候，cinder会先计算快照链如何整合( 需要Libvirt版本'1.2.7'以上)，最终call nova来完成
大致流程：
cinder/volume/drivers/remotefs.py ->> cinder/volume/drivers/glusterfs.py ->> cinder/compute/nova.py ->> novaclient/v1_1/contrib/assisted_volume_snapshots.py ->> novaclient/base.py ->> nova/virt/libvirt/driver.py
nova/virt/libvirt/driver.py:
这里可以看到Cinder QuiescedSnapshot，第一次会先尝试做Quiesce快照，如果抛异常了，就执行下面不带Quiesce的快照。
cinder run unit test http://docs.openstack.org/developer/cinder/devref/unit_tests.html