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[libvirt] [PATCH 4/5] block_resize: Implement qemu driver method



It requires the domain is running, otherwise fails. Resize to a lower
size is supported, but should be used with extreme caution.

In order to prohibit the "size" overflowing after multiplied by
1024. We do checking in the codes. This might be not quite properly,
as for QMP mode, the default units is Bytes, the passed size needs
to be multiplied by 1024, however, for HMP mode, the default units
is "Megabytes", the passed "size" needs to be divided by 1024 then.
---
 src/qemu/qemu_driver.c |   98 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 98 insertions(+), 0 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 5df58b1..6ee24b7 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -6513,6 +6513,103 @@ qemuGetSchedulerParameters(virDomainPtr dom,
                                            VIR_DOMAIN_AFFECT_CURRENT);
 }
 
+/**
+ * Resize a block device while a guest is running. Resize to a lower size
+ * is supported, but should be used with extreme caution.  Note that it
+ * only supports to resize image files, it can not resize block devices
+ * like LVM volumes.
+ */
+static int
+qemuDomainBlockResize (virDomainPtr dom,
+                       const char *path,
+                       unsigned long long size,
+                       unsigned int flags)
+{
+    struct qemud_driver *driver = dom->conn->privateData;
+    virDomainObjPtr vm;
+    qemuDomainObjPrivatePtr priv;
+    int ret = -1, i;
+    char *device = NULL;
+    bool found = false;
+
+    virCheckFlags(0, -1);
+
+    if (path[0] == '\0') {
+        qemuReportError(VIR_ERR_INVALID_ARG,
+                        "%s", _("empty path"));
+        return -1;
+    }
+
+    if (size > ULLONG_MAX / 1024) {
+        qemuReportError(VIR_ERR_INVALID_ARG,
+                        _("size must be less than %llu"),
+                        ULLONG_MAX / 1024);
+        return -1;
+    }
+
+    qemuDriverLock(driver);
+    vm = virDomainFindByUUID(&driver->domains, dom->uuid);
+    qemuDriverUnlock(driver);
+
+    if (!vm) {
+        char uuidstr[VIR_UUID_STRING_BUFLEN];
+        virUUIDFormat(dom->uuid, uuidstr);
+        qemuReportError(VIR_ERR_NO_DOMAIN,
+                        _("no domain matching uuid '%s'"), uuidstr);
+        goto cleanup;
+    }
+
+    priv = vm->privateData;
+
+    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
+        goto cleanup;
+
+    if (!virDomainObjIsActive(vm)) {
+        qemuReportError(VIR_ERR_OPERATION_INVALID,
+                        "%s", _("domain is not running"));
+        goto endjob;
+    }
+
+    for (i = 0 ; i < vm->def->ndisks ; i++) {
+        if (vm->def->disks[i]->src != NULL &&
+            STREQ (vm->def->disks[i]->src, path)) {
+            found = true;
+            break;
+        }
+    }
+
+    if (!found) {
+        qemuReportError(VIR_ERR_INVALID_ARG,
+                        _("no domain disk matching path '%s'"), path);
+        goto endjob;
+    }
+
+    if (virAsprintf(&device, "%s%s", QEMU_DRIVE_HOST_PREFIX,
+                    vm->def->disks[i]->info.alias) < 0) {
+        virReportOOMError();
+        goto endjob;
+    }
+
+    ignore_value(qemuDomainObjEnterMonitor(driver, vm));
+    if (qemuMonitorBlockResize(priv->mon, device, size) < 0) {
+        qemuDomainObjExitMonitor(driver, vm);
+        goto endjob;
+    }
+    qemuDomainObjExitMonitor(driver, vm);
+
+    ret = 0;
+
+endjob:
+    if (qemuDomainObjEndJob(driver, vm) == 0)
+        vm = NULL;
+
+cleanup:
+    VIR_FREE(device);
+    if (vm)
+        virDomainObjUnlock(vm);
+    return ret;
+}
+
 /* This uses the 'info blockstats' monitor command which was
  * integrated into both qemu & kvm in late 2007.  If the command is
  * not supported we detect this and return the appropriate error.
@@ -9189,6 +9286,7 @@ static virDriver qemuDriver = {
     .domainSetSchedulerParameters = qemuSetSchedulerParameters, /* 0.7.0 */
     .domainSetSchedulerParametersFlags = qemuSetSchedulerParametersFlags, /* 0.9.2 */
     .domainMigratePerform = qemudDomainMigratePerform, /* 0.5.0 */
+    .domainBlockResize = qemuDomainBlockResize, /* 0.9.5 */
     .domainBlockStats = qemudDomainBlockStats, /* 0.4.1 */
     .domainInterfaceStats = qemudDomainInterfaceStats, /* 0.4.1 */
     .domainMemoryStats = qemudDomainMemoryStats, /* 0.7.5 */
-- 
1.7.6


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