block_resize: Define the new API

The new API is named as "virDomainBlockResize", intending to add
support for qemu monitor command "block_resize" (both HMP and QMP).

Similar with APIs like "virDomainSetMemoryFlags", the units for
argument "size" is kilobytes.

include/libvirt/libvirt.h.in

@@ -1400,7 +1400,10 @@ int                     virDomainBlockPeek (virDomainPtr dom,
                                             size_t size,
                                             void *buffer,
                                             unsigned int flags);
-
+int                     virDomainBlockResize (virDomainPtr dom,
+                                              const char *disk,
+                                              unsigned long long size,
+                                              unsigned int flags);
 
 /** virDomainBlockInfo:
  *

src/driver.h

@@ -377,7 +377,12 @@ typedef int
                      unsigned long long offset, size_t size,
                      void *buffer,
                      unsigned int flags);
-
+typedef int
+    (*virDrvDomainBlockResize)
+                    (virDomainPtr domain,
+                     const char *path,
+                     unsigned long long size,
+                     unsigned int flags);
 typedef int
     (*virDrvDomainMemoryPeek)
                     (virDomainPtr domain,
@@ -846,6 +851,7 @@ struct _virDriver {
     virDrvDomainMigratePrepare	domainMigratePrepare;
     virDrvDomainMigratePerform	domainMigratePerform;
     virDrvDomainMigrateFinish	domainMigrateFinish;
+    virDrvDomainBlockResize     domainBlockResize;
     virDrvDomainBlockStats      domainBlockStats;
     virDrvDomainBlockStatsFlags domainBlockStatsFlags;
     virDrvDomainInterfaceStats  domainInterfaceStats;

src/libvirt.c

@@ -7090,6 +7090,74 @@ error:
     return -1;
 }
 
+/**
+ * virDomainBlockResize:
+ * @dom: pointer to the domain object
+ * @disk: path to the block image, or shorthand
+ * @size: new size of the block image in kilobytes
+ * @flags: unused, always pass 0
+ *
+ * Note that this call may fail if the underlying virtualization hypervisor
+ * does not support it. And this call requires privileged access to the
+ * hypervisor.
+ *
+ * The @disk parameter is either an unambiguous source name of the
+ * block device (the <source file='...'/> sub-element, such as
+ * "/path/to/image"), or (since 0.9.5) the device target shorthand
+ * (the <target dev='...'/> sub-element, such as "xvda").  Valid names
+ * can be found by calling virDomainGetXMLDesc() and inspecting
+ * elements within //domain/devices/disk.
+ *
+ * Resize a block device of domain while the domain is running.
+ *
+ * Returns: 0 in case of success or -1 in case of failure.
+ */
+
+int
+virDomainBlockResize (virDomainPtr dom,
+                      const char *disk,
+                      unsigned long long size,
+                      unsigned int flags)
+{
+    virConnectPtr conn;
+
+    VIR_DOMAIN_DEBUG(dom, "disk=%s, size=%llu, flags=%x", disk, size, flags);
+
+    virResetLastError();
+
+    if (!VIR_IS_CONNECTED_DOMAIN (dom)) {
+        virLibDomainError(VIR_ERR_INVALID_DOMAIN, __FUNCTION__);
+        virDispatchError(NULL);
+        return -1;
+    }
+    conn = dom->conn;
+
+    if (dom->conn->flags & VIR_CONNECT_RO) {
+        virLibDomainError(VIR_ERR_OPERATION_DENIED, __FUNCTION__);
+        goto error;
+    }
+
+    if (!disk) {
+        virLibDomainError(VIR_ERR_INVALID_ARG,
+                           _("disk is NULL"));
+        goto error;
+    }
+
+    if (conn->driver->domainBlockResize) {
+        int ret;
+        ret =conn->driver->domainBlockResize(dom, disk, size, flags);
+        if (ret < 0)
+            goto error;
+        return ret;
+    }
+
+    virLibDomainError(VIR_ERR_NO_SUPPORT, __FUNCTION__);
+
+error:
+    virDispatchError(dom->conn);
+    return -1;
+}
+
 /**
  * virDomainMemoryPeek:
  * @dom: pointer to the domain object

src/libvirt_public.syms

@@ -503,6 +503,7 @@ LIBVIRT_0.9.8 {
         virConnectIsAlive;
         virConnectSetKeepAlive;
         virNodeSuspendForDuration;
+        virDomainBlockResize;
 } LIBVIRT_0.9.7;
 
 # .... define new API here using predicted next version number ....