[PATCH v4 11/14] qemu: Start PR daemon on disk hotplug

[Michal Privoznik <mprivozn@xxxxxxxxxx>]

When plugging a disk into domain we need to start qemu-pr-helper
process iff this is the first disk with PR enabled for the
domain. Otherwise the helper is already running (or not needed).

Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
 src/qemu/qemu_hotplug.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/qemu/qemu_process.c |  4 ++--
 src/qemu/qemu_process.h |  5 +++++
 3 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index f0d549de38..468153c79c 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -348,6 +348,49 @@ qemuDomainChangeEjectableMedia(virQEMUDriverPtr driver,
 }
 
 
+/**
+ * qemuDomainMaybeStartPRDaemon:
+ * @vm: domain object
+ * @disk: disk to hotplug
+ *
+ * Checks if it's needed to start qemu-pr-helper and starts it.
+ *
+ * Returns: 0 if qemu-pr-helper is not needed
+ *          1 if it is needed and was started
+ *         -1 otherwise.
+ */
+static int
+qemuDomainMaybeStartPRDaemon(virDomainObjPtr vm,
+                             virDomainDiskDefPtr disk)
+{
+    size_t i;
+    qemuDomainStorageSourcePrivatePtr srcPriv;
+
+    if (!virStoragePRDefIsManaged(disk->src->pr)) {
+        /* @disk itself does not require qemu-pr-helper. */
+        return 0;
+    }
+
+    for (i = 0; i < vm->def->ndisks; i++) {
+        const virDomainDiskDef *domainDisk = vm->def->disks[i];
+
+        if (virStoragePRDefIsManaged(domainDisk->src->pr)) {
+            /* qemu-pr-helper should be already started because
+             * another disk in domain requires it. */
+            return 0;
+        }
+    }
+
+    /* @disk requires qemu-pr-helper but none is running.
+     * Start it now. */
+    srcPriv = QEMU_DOMAIN_STORAGE_SOURCE_PRIVATE(disk->src);
+    if (qemuProcessStartPRDaemon(vm, srcPriv->prd) < 0)
+        return -1;
+
+    return 1;
+}
+
+
 /**
  * qemuDomainAttachDiskGeneric:
  *
@@ -368,6 +411,7 @@ qemuDomainAttachDiskGeneric(virQEMUDriverPtr driver,
     bool driveAdded = false;
     bool secobjAdded = false;
     bool encobjAdded = false;
+    bool prdStarted = false;
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
     virJSONValuePtr secobjProps = NULL;
     virJSONValuePtr encobjProps = NULL;
@@ -384,6 +428,11 @@ qemuDomainAttachDiskGeneric(virQEMUDriverPtr driver,
     if (qemuDomainPrepareDiskSource(disk, priv, cfg) < 0)
         goto error;
 
+    if ((rv = qemuDomainMaybeStartPRDaemon(vm, disk)) < 0)
+        goto cleanup;
+    else if (rv > 0)
+        prdStarted = true;
+
     srcPriv = QEMU_DOMAIN_STORAGE_SOURCE_PRIVATE(disk->src);
     if (srcPriv) {
         secinfo = srcPriv->secinfo;
@@ -481,6 +530,8 @@ qemuDomainAttachDiskGeneric(virQEMUDriverPtr driver,
  error:
     qemuDomainDelDiskSrcTLSObject(driver, vm, disk->src);
     ignore_value(qemuHotplugPrepareDiskAccess(driver, vm, disk, NULL, true));
+    if (prdStarted)
+        qemuProcessKillPRDaemon(vm);
     goto cleanup;
 }
 
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 982c989a0a..11aaeabb38 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -2571,7 +2571,7 @@ qemuProcessBuildPRHelperPidfilePath(virDomainObjPtr vm,
 }
 
 
-static void
+void
 qemuProcessKillPRDaemon(virDomainObjPtr vm)
 {
     virErrorPtr orig_err;
@@ -2629,7 +2629,7 @@ qemuProcessStartPRDaemonHook(void *opaque)
 }
 
 
-static int
+int
 qemuProcessStartPRDaemon(virDomainObjPtr vm,
                          qemuDomainDiskPRDPtr prd)
 {
diff --git a/src/qemu/qemu_process.h b/src/qemu/qemu_process.h
index 2741115673..8df5832e23 100644
--- a/src/qemu/qemu_process.h
+++ b/src/qemu/qemu_process.h
@@ -203,4 +203,9 @@ int qemuProcessRefreshDisks(virQEMUDriverPtr driver,
                             virDomainObjPtr vm,
                             qemuDomainAsyncJob asyncJob);
 
+int qemuProcessStartPRDaemon(virDomainObjPtr vm,
+                             qemuDomainDiskPRDPtr prd);
+
+void qemuProcessKillPRDaemon(virDomainObjPtr vm);
+
 #endif /* __QEMU_PROCESS_H__ */
-- 
2.16.1

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