[libvirt] [PATCHv4 01/18] blockjob: add qemu capabilities related to block jobs

[Eric Blake]

The new block copy storage migration sequence requires both the
'drive-mirror' action in 'transaction' (present if the 'drive-mirror'
standalone monitor command also exists) and the 'drive-reopen' monitor
command (it would be nice if that were also part of a 'transaction',
but the initial qemu implementation has it standalone only).

Furthermore, qemu 1.1 will be adding 'block_job_cancel' as an
asynchronous command, but an earlier implementation (that supported
only the qed file format) existed which was synchronous only.  If
'drive-mirror' is added in time, then we can safely use 'drive-mirror'
as the witness of whether 'block_job_cancel' is synchronous or
asynchronous.

As of this[1] qemu email, both commands have been proposed but not yet
incorporated into the tree; in fact, the implementation I tested with
has changed to match this[2] email that suggested a mandatory
'full':'bool' argument rather than 'mode':'no-backing-file'.  So there
is a risk that qemu 1.1 will have yet another subtly different
implementation.
[1]https://lists.gnu.org/archive/html/qemu-devel/2012-03/msg01524.html
[2]https://lists.gnu.org/archive/html/qemu-devel/2012-04/msg00886.html

* src/qemu/qemu_capabilities.h (QEMU_CAPS_DRIVE_MIRROR)
(QEMU_CAPS_DRIVE_REOPEN): New bits.
* src/qemu/qemu_capabilities.c (qemuCaps): Name them.
* src/qemu/qemu_monitor_json.c (qemuMonitorJSONCheckCommands): Set
them.
(qemuMonitorJSONDiskSnapshot): Fix formatting issues.
---
 src/qemu/qemu_capabilities.c |    3 +++
 src/qemu/qemu_capabilities.h |    2 ++
 src/qemu/qemu_monitor_json.c |   15 ++++++++-------
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 0e09d6d..1938ae4 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -156,6 +156,9 @@ VIR_ENUM_IMPL(qemuCaps, QEMU_CAPS_LAST,
               "scsi-disk.channel",
               "scsi-block",
               "transaction",
+
+              "drive-mirror", /* 90 */
+              "drive-reopen",
     );

 struct qemu_feature_flags {
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index 78cdbe0..405bf2a 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -124,6 +124,8 @@ enum qemuCapsFlags {
     QEMU_CAPS_SCSI_DISK_CHANNEL  = 87, /* Is scsi-disk.channel available? */
     QEMU_CAPS_SCSI_BLOCK         = 88, /* -device scsi-block */
     QEMU_CAPS_TRANSACTION        = 89, /* transaction monitor command */
+    QEMU_CAPS_DRIVE_MIRROR       = 90, /* drive-mirror monitor command */
+    QEMU_CAPS_DRIVE_REOPEN       = 91, /* drive-reopen monitor command */

     QEMU_CAPS_LAST,                   /* this must always be the last item */
 };
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index d09d779..c8ed087 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -939,12 +939,14 @@ qemuMonitorJSONCheckCommands(qemuMonitorPtr mon,

         if (STREQ(name, "human-monitor-command"))
             *json_hmp = 1;
-
-        if (STREQ(name, "system_wakeup"))
+        else if (STREQ(name, "system_wakeup"))
             qemuCapsSet(qemuCaps, QEMU_CAPS_WAKEUP);
-
-        if (STREQ(name, "transaction"))
+        else if (STREQ(name, "transaction"))
             qemuCapsSet(qemuCaps, QEMU_CAPS_TRANSACTION);
+        else if (STREQ(name, "drive-mirror"))
+            qemuCapsSet(qemuCaps, QEMU_CAPS_DRIVE_MIRROR);
+        else if (STREQ(name, "drive-reopen"))
+            qemuCapsSet(qemuCaps, QEMU_CAPS_DRIVE_REOPEN);
     }

     ret = 0;
@@ -3114,7 +3116,7 @@ qemuMonitorJSONDiskSnapshot(qemuMonitorPtr mon, virJSONValuePtr actions,
                             const char *device, const char *file,
                             const char *format, bool reuse)
 {
-    int ret;
+    int ret = -1;
     virJSONValuePtr cmd;
     virJSONValuePtr reply = NULL;

@@ -3132,14 +3134,13 @@ qemuMonitorJSONDiskSnapshot(qemuMonitorPtr mon, virJSONValuePtr actions,
     if (actions) {
         if (virJSONValueArrayAppend(actions, cmd) < 0) {
             virReportOOMError();
-            ret = -1;
         } else {
             ret = 0;
             cmd = NULL;
         }
     } else {
         if ((ret = qemuMonitorJSONCommand(mon, cmd, &reply)) < 0)
-        goto cleanup;
+            goto cleanup;

         if (qemuMonitorJSONHasError(reply, "CommandNotFound") &&
             qemuMonitorCheckHMP(mon, "snapshot_blkdev")) {
-- 
1.7.7.6