Re: [libvirt] [PATCH 09/14] Add support for re-exec() of virtlockd upon SIGUSR1

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; The virtlockd daemon maintains file locks on behalf of libvirtd and any VMs it is running. These file locks must be held for as long as any VM is running. If virtlockd itself ever quits, then it is expected that a node would be fenced/rebooted. Thus to allow for software upgrads on live systemd, virtlockd needs the ability to re-exec() itself. Upon receipt of SIGUSR1, virtlockd will save its current live state out to a file /var/run/virtlockd-restart-exec.json It then re-exec()'s itself with exactly the same argv as it originally had, and loads the state file, reconstructing any objects as appropriate. The state file contains information about all locks held and all network services and clients currently active. An example state document is { "server": { "min_workers": 1, "max_workers": 20, "priority_workers": 0, "max_clients": 20, "keepaliveInterval": 4294967295, "keepaliveCount": 0, "keepaliveRequired": false, "services": [ { "auth": 0, "readonly": false, "nrequests_client_max": 1, "socks": [ { "fd": 6, "errfd": -1, "pid": 0, "isClient": false } ] } ], "clients": [ { "auth": 0, "readonly": false, "nrequests_max": 1, "sock": { "fd": 9, "errfd": -1, "pid": 0, "isClient": true }, "privateData": { "restricted": true, "ownerPid": 1722, "ownerId": 6, "ownerName": "f18x86_64", "ownerUUID": "97586ba9-df27-9459-c806-f016c8bbd224" } }, { "auth": 0, "readonly": false, "nrequests_max": 1, "sock": { "fd": 10, "errfd": -1, "pid": 0, "isClient": true }, "privateData": { "restricted": true, "ownerPid": 1784, "ownerId": 7, "ownerName": "f16x86_64", "ownerUUID": "7b8e5e42-b875-61e9-b981-91ad8fa46979" } } ] }, "defaultLockspace": { "resources": [ { "name": "/var/lib/libvirt/images/f16x86_64.raw", "path": "/var/lib/libvirt/images/f16x86_64.raw", "fd": 14, "lockHeld": true, "flags": 0, "owners": [ 1784 ] }, { "name": "/var/lib/libvirt/images/shared.img", "path": "/var/lib/libvirt/images/shared.img", "fd": 12, "lockHeld": true, "flags": 1, "owners": [ 1722, 1784 ] }, { "name": "/var/lib/libvirt/images/f18x86_64.img", "path": "/var/lib/libvirt/images/f18x86_64.img", "fd": 11, "lockHeld": true, "flags": 0, "owners": [ 1722 ] } ] }, "lockspaces": [ ], "magic": "30199" } Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- libvirt.spec.in | 5 +- src/locking/lock_daemon.c | 417 ++++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 409 insertions(+), 13 deletions(-)