[libvirt] [PATCH 09/14] qemu: Start PR daemons on domain startup

[Michal Privoznik]

Before we exec() qemu we have to spawn pr-helper processes for
all managed reservations (well, technically there can only one).
The only caveat there is that we should place the process into
the same namespace and cgroup as qemu (so that it shares the same
view of the system). But we can do that only after we've forked.
That means calling the setup function between fork() and exec().

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/qemu/qemu_process.c | 151 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 151 insertions(+)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 25ec464d3..02608c1f3 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -2507,6 +2507,151 @@ qemuProcessSetupEmulator(virDomainObjPtr vm)
 }
 
 
+static int
+qemuProcessSetupOnePRDaemonHook(void *opaque)
+{
+    virDomainObjPtr vm = opaque;
+    size_t i, nfds = 0;
+    int *fds = NULL;
+    int ret = -1;
+
+    if (virProcessGetNamespaces(vm->pid, &nfds, &fds) < 0)
+        return ret;
+
+    if (virProcessSetNamespaces(nfds, fds) < 0)
+        goto cleanup;
+
+    ret = 0;
+ cleanup:
+    for (i = 0; i < nfds; i++)
+        VIR_FORCE_CLOSE(fds[i]);
+    VIR_FREE(fds);
+    return ret;
+}
+
+
+static int
+qemuProcessSetupOnePRDaemon(void *payload,
+                            const void *name,
+                            void *opaque)
+{
+    qemuDomainDiskPRObjectPtr prObj = payload;
+    virDomainObjPtr vm = opaque;
+    qemuDomainObjPrivatePtr priv = vm->privateData;
+    virQEMUDriverPtr driver = priv->driver;
+    virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
+    char *pidfile = NULL;
+    pid_t cpid = -1;
+    virCommandPtr cmd = NULL;
+    virTimeBackOffVar timebackoff;
+    const unsigned long long timeout = 500000; /* ms */
+    int ret = -1;
+
+    if (!prObj->managed)
+        return 0;
+
+    if (!virFileIsExecutable(cfg->prHelperName)) {
+        virReportSystemError(errno, _("'%s' is not a suitable pr helper"),
+                             cfg->prHelperName);
+        goto cleanup;
+    }
+
+    if (!(pidfile = virPidFileBuildPath(cfg->stateDir, name)))
+        goto cleanup;
+
+    if (unlink(pidfile) < 0 &&
+        errno != ENOENT) {
+        virReportSystemError(errno,
+                             _("Cannot remove stale PID file %s"),
+                             pidfile);
+        goto cleanup;
+    }
+
+    if (!(cmd = virCommandNewArgList(cfg->prHelperName,
+                                     "-k", prObj->path,
+                                     NULL)))
+        goto cleanup;
+
+    virCommandDaemonize(cmd);
+    virCommandSetPidFile(cmd, pidfile);
+    virCommandSetPreExecHook(cmd, qemuProcessSetupOnePRDaemonHook, vm);
+
+#ifdef CAP_SYS_RAWIO
+    virCommandAllowCap(cmd, CAP_SYS_RAWIO);
+#else
+    virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                   _("Raw I/O is not supported on this platform"));
+    goto cleanup;
+#endif
+
+    if (virCommandRun(cmd, NULL) < 0)
+        goto cleanup;
+
+    if (virPidFileReadPath(pidfile, &cpid) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("pr helper %s didn't show up"), (const char *) name);
+        goto cleanup;
+    }
+
+    if (virTimeBackOffStart(&timebackoff, 1, timeout) < 0)
+        goto cleanup;
+    while (virTimeBackOffWait(&timebackoff)) {
+        if (virFileExists(prObj->path))
+            break;
+
+        if (virProcessKill(cpid, 0) == 0)
+            continue;
+
+        virReportSystemError(errno, "%s",
+                             _("pr helper died unexpectedly"));
+        goto cleanup;
+    }
+
+    if (priv->cgroup &&
+        virCgroupAddMachineTask(priv->cgroup, cpid) < 0)
+        goto cleanup;
+
+    if (qemuSecurityDomainSetPathLabel(driver->securityManager,
+                                       vm->def, prObj->path, true) < 0)
+        goto cleanup;
+
+    prObj->pid = cpid;
+    ret = 0;
+ cleanup:
+    if (ret < 0) {
+        virCommandAbort(cmd);
+        virProcessKillPainfully(cpid, true);
+    }
+    virCommandFree(cmd);
+    if (unlink(pidfile) < 0 &&
+        errno != ENOENT &&
+        !virGetLastError())
+        virReportSystemError(errno,
+                             _("Cannot remove stale PID file %s"),
+                             pidfile);
+    VIR_FREE(pidfile);
+    virObjectUnref(cfg);
+    return ret;
+}
+
+
+static int
+qemuProcessSetupPRDaemons(virDomainObjPtr vm)
+{
+    qemuDomainObjPrivatePtr priv = vm->privateData;
+    int ret = -1;
+
+    if (priv->prHelpers &&
+        virHashForEach(priv->prHelpers,
+                       qemuProcessSetupOnePRDaemon, vm) < 0)
+        goto cleanup;
+
+    ret = 0;
+ cleanup:
+    return ret;
+}
+
+
 static int
 qemuProcessInitPasswords(virConnectPtr conn,
                          virQEMUDriverPtr driver,
@@ -5896,6 +6041,10 @@ qemuProcessLaunch(virConnectPtr conn,
     if (qemuProcessSetupEmulator(vm) < 0)
         goto cleanup;
 
+    VIR_DEBUG("Setting up PR daemons");
+    if (qemuProcessSetupPRDaemons(vm) < 0)
+        goto cleanup;
+
     VIR_DEBUG("Setting domain security labels");
     if (qemuSecuritySetAllLabel(driver,
                                 vm,
@@ -6475,6 +6624,8 @@ void qemuProcessStop(virQEMUDriverPtr driver,
         VIR_FREE(vm->def->seclabels[i]->imagelabel);
     }
 
+    qemuDomainDiskPRObjectKillAll(priv);
+
     qemuHostdevReAttachDomainDevices(driver, vm->def);
 
     def = vm->def;
-- 
2.13.6