qemu: pass block pull backing file to monitor

This actually wires up the new optional parameter to block_stream:
http://wiki.qemu.org/Features/LiveBlockMigration/ImageStreamingAPI

The error checking is still sparse, since libvirt must not use
qemu-img or header probing on a qcow2 file in use by qemu to
check if the backing file name is valid; so for now, libvirt is
relying on qemu to diagnose an incorrect backing name.  Fixing this
will require libvirt to track the entire backing file chain at the
time qemu is started and keeps it updated with snapshot and pull
operations.

* src/qemu/qemu_monitor_json.c (qemuMonitorJSONBlockJob): Add
parameter, and update callers.
* src/qemu/qemu_monitor_json.h (qemuMonitorJSONBlockJob): Update
signature.
* src/qemu/qemu_monitor.h (qemuMonitorBlockJob): Likewise.
* src/qemu/qemu_driver.c (qemuDomainBlockJobImpl): Update caller.
* src/qemu/qemu_monitor.c (qemuMonitorBlockJob): Likewise.

src/qemu/qemu_driver.c

@@ -11379,14 +11379,6 @@ qemuDomainBlockJobImpl(virDomainPtr dom, const char *path, const char *base,
     if (!device) {
         goto cleanup;
     }
-    /* XXX - add a qemu capability check; if qemu 1.1 or newer, then
-     *  validate and convert non-NULL base into something that can
-     * be passed as optional base argument.  */
-    if (base)  {
-        qemuReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
-                        _("partial block pull is not supported with this QEMU binary"));
-        goto cleanup;
-    }
 
     if (qemuDomainObjBeginJobWithDriver(driver, vm, QEMU_JOB_MODIFY) < 0)
         goto cleanup;
@@ -11399,7 +11391,12 @@ qemuDomainBlockJobImpl(virDomainPtr dom, const char *path, const char *base,
 
     qemuDomainObjEnterMonitorWithDriver(driver, vm);
     priv = vm->privateData;
-    ret = qemuMonitorBlockJob(priv->mon, device, bandwidth, info, mode);
+    /* XXX - add a qemu capability check, since only qemu 1.1 or newer
+     * supports the base argument.
+     * XXX - libvirt should really be tracking the backing file chain
+     * itself, and validating that base is on the chain, rather than
+     * relying on qemu to do this.  */
+    ret = qemuMonitorBlockJob(priv->mon, device, base, bandwidth, info, mode);
     qemuDomainObjExitMonitorWithDriver(driver, vm);
 
 endjob:

src/qemu/qemu_monitor.c

@@ -2712,17 +2712,18 @@ int qemuMonitorScreendump(qemuMonitorPtr mon,
 
 int qemuMonitorBlockJob(qemuMonitorPtr mon,
                         const char *device,
+                        const char *base,
                         unsigned long bandwidth,
                         virDomainBlockJobInfoPtr info,
                         int mode)
 {
     int ret = -1;
 
-    VIR_DEBUG("mon=%p, device=%s, bandwidth=%lu, info=%p, mode=%o",
-              mon, device, bandwidth, info, mode);
+    VIR_DEBUG("mon=%p, device=%s, base=%s, bandwidth=%lu, info=%p, mode=%o",
+              mon, device, NULLSTR(base), bandwidth, info, mode);
 
     if (mon->json)
-        ret = qemuMonitorJSONBlockJob(mon, device, bandwidth, info, mode);
+        ret = qemuMonitorJSONBlockJob(mon, device, base, bandwidth, info, mode);
     else
         qemuReportError(VIR_ERR_INVALID_ARG, "%s",
                         _("block jobs require JSON monitor"));

src/qemu/qemu_monitor.h

 /*
  * qemu_monitor.h: interaction with QEMU monitor console
  *
- * Copyright (C) 2006-2011 Red Hat, Inc.
+ * Copyright (C) 2006-2012 Red Hat, Inc.
  * Copyright (C) 2006 Daniel P. Berrange
  *
  * This library is free software; you can redistribute it and/or
@@ -519,9 +519,11 @@ typedef enum {
 
 int qemuMonitorBlockJob(qemuMonitorPtr mon,
                         const char *device,
+                        const char *back,
                         unsigned long bandwidth,
                         virDomainBlockJobInfoPtr info,
-                        int mode);
+                        int mode)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(5);
 
 int qemuMonitorOpenGraphics(qemuMonitorPtr mon,
                             const char *protocol,

src/qemu/qemu_monitor_json.c

@@ -3229,17 +3229,25 @@ static int qemuMonitorJSONGetBlockJobInfo(virJSONValuePtr reply,
 }
 
 
-int qemuMonitorJSONBlockJob(qemuMonitorPtr mon,
-                             const char *device,
-                             unsigned long bandwidth,
-                             virDomainBlockJobInfoPtr info,
-                             int mode)
+int
+qemuMonitorJSONBlockJob(qemuMonitorPtr mon,
+                        const char *device,
+                        const char *base,
+                        unsigned long bandwidth,
+                        virDomainBlockJobInfoPtr info,
+                        int mode)
 {
     int ret = -1;
     virJSONValuePtr cmd = NULL;
     virJSONValuePtr reply = NULL;
     const char *cmd_name = NULL;
 
+    if (base && mode != BLOCK_JOB_PULL) {
+        qemuReportError(VIR_ERR_INTERNAL_ERROR,
+                        _("only block pull supports base: %s"), base);
+        return -1;
+    }
+
     if (mode == BLOCK_JOB_ABORT) {
         cmd_name = "block_job_cancel";
         cmd = qemuMonitorJSONMakeCommand(cmd_name, "s:device", device, NULL);
@@ -3254,8 +3262,12 @@ int qemuMonitorJSONBlockJob(qemuMonitorPtr mon,
                                          NULL);
     } else if (mode == BLOCK_JOB_PULL) {
         cmd_name = "block_stream";
-        cmd = qemuMonitorJSONMakeCommand(cmd_name, "s:device",
-                                         device, NULL);
+        if (base)
+            cmd = qemuMonitorJSONMakeCommand(cmd_name, "s:device",
+                                             device, "s:base", base, NULL);
+        else
+            cmd = qemuMonitorJSONMakeCommand(cmd_name, "s:device",
+                                             device, NULL);
     }
 
     if (!cmd)

src/qemu/qemu_monitor_json.h

 /*
  * qemu_monitor_json.h: interaction with QEMU monitor console
  *
- * Copyright (C) 2006-2009, 2011 Red Hat, Inc.
+ * Copyright (C) 2006-2009, 2011-2012 Red Hat, Inc.
  * Copyright (C) 2006 Daniel P. Berrange
  *
  * This library is free software; you can redistribute it and/or
@@ -246,6 +246,7 @@ int qemuMonitorJSONScreendump(qemuMonitorPtr mon,
 
 int qemuMonitorJSONBlockJob(qemuMonitorPtr mon,
                             const char *device,
+                            const char *base,
                             unsigned long bandwidth,
                             virDomainBlockJobInfoPtr info,
                             int mode);