This patch adds the machinery required for protecting a guest's
disk state, when the guest disk uses a DRBD disk backend.
This patch comprises of two parts:
1. Hotplug scripts: The block-drbd-probe script is responsible for
performing sanity checks on the state of the DRBD disk before the
checkpointing process begins. This script should be invoked by
libxl for each of the guest's disk devices, when starting Remus.
2. Remus drbd disk device: Implements the interfaces required by the
remus abstract device layer. A note about the implementation:
a) setup() is called for each disk attached to the guest.
During setup():
i) The hotplug script is called to perform the sanity check.
ii) Libxl obtains a handle to the DRBD device (/dev/drbd*) and
and subsequently controls disk checkpoint replication using
this handle in the checkpoint callbacks.
c) The preresume() checkpoint callback is executed asynchronously
using libxl__ev_child_fork(), as it may potentially block for more
than few seconds in case of backup failure.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Signed-off-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This patch adds the machinery required for protecting a guest's
network device state. This patch comprises of two parts:
1. Hotplug scripts: The remus-netbuf-setup script is responsible for
setting up and tearing down the necessary infrastructure required for
network output buffering. This script should be invoked by libxl for
each of the guest's network interfaces, when starting or stopping Remus.
Apart from returning success/failure indication via the usual hotplug
entries in xenstore, this script also writes to xenstore, the name of
the REMUS_IFB device to be used to control the vif's network output.
The script relies on libnl3 command line utilities to perform various
setup/teardown functions. The script is confined to Linux platforms only
since NetBSD does not seem to have libnl3.
2. Remus network device: Implements the interfaces required by the
remus abstract device layer. A note about the implementation:
a) init_subkind_nic() & cleanup_subkind_nic() are called once per Remus
invocation. They establish and free netlink related state respectively.
b) setup() and teardown are called for each vif attached to the
guest.
During setup():
i) The hotplug script is called to setup a network buffer on a
given vif. The script chooses an available IFB device from
the system, redirects vif egress traffic to the IFB device
and sets up the plug qdisc (output buffer) on the IFB device.
The name of the IFB device is communicated via xenstore to
libxl.
ii) Libxl obtains a handle to the plug qdisc using the libnl3 API
and subsequently controls output buffering using this handle
in the checkpoint callbacks.
During teardown(), the hotplug scripts are called again to remove
the vif->ifb traffic redirection, release the ifb and the plug
qdisc associated with it.
c) The checkpoint callbacks [postsuspend(), preresume() and commit()]
are implemented as synchronous ops as the netlink calls associated
with the qdisc subsystem are very fast.
Signed-off-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Introduce an abstract device layer that allows the Remus
logic in libxl to control a guest's devices in a device-agnostic
manner. The device layer also exposes a set of internal interfaces
that a device type must implement, if it wishes to support Remus.
The following API are exposed to libxl:
One-time configuration operations:
*libxl__remus_devices_setup
> Enable output buffering for NICs, setup disk replication, etc.
*libxl__remus_devices_teardown
> Disable network output buffering and disk replication;
teardown any associated external setups like qdiscs for NICs.
Operations executed every checkpoint (in order of invocation):
*libxl__remus_devices_postsuspend
*libxl__remus_devices_preresume
*libxl__remus_devices_commit
Each device type needs to implement the interfaces specified in
the libxl__remus_device_instance_ops if it wishes to support Remus.
The high-level control flow through the Remus device layer is shown below:
xl remus
|-> libxl_domain_remus_start
|-> libxl__remus_devices_setup
|-> Per-checkpoint libxl__remus_devices_[postsuspend,preresume,commit]
...
|-> On backup failure/network error/other errors
libxl__remus_devices_teardown
callback processing
* Only call the per-device libxl__multidev_one_callback
when the iteration has succeded or failed.
* The final callback (called by multidev) is a trivial
shim to shuffle the pointers and notify our own caller.
Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Yang Hongyang