[libvirt] [PATCHv2 02/15] blockjob: wire up qemu async virDomainBlockJobAbort

[Eric Blake]

From: Adam Litke <agl at us.ibm.com>

Without the VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC flag, libvirt will internally poll
using qemu's "query-block-jobs" API and will not return until the operation has
been completed.  API users are advised that this operation is unbounded and
further interaction with the domain during this period may block.  Future
patches may refactor things to allow other queries in parallel with this
polling.  Unfortunately, there's no good way to tell if qemu will emit the
new event, so this implementation always polls to deal with older qemu.

Signed-off-by: Adam Litke <agl at us.ibm.com>
Cc: Stefan Hajnoczi <stefanha at gmail.com>
Signed-off-by: Eric Blake <eblake at redhat.com>
---
 src/qemu/qemu_driver.c |   55 +++++++++++++++++++++++++++++++++++++++++------
 1 files changed, 48 insertions(+), 7 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 0456b34..455fa30 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -11602,7 +11602,7 @@ cleanup:
 static int
 qemuDomainBlockJobImpl(virDomainPtr dom, const char *path, const char *base,
                        unsigned long bandwidth, virDomainBlockJobInfoPtr info,
-                       int mode)
+                       int mode, unsigned int flags)
 {
     struct qemud_driver *driver = dom->conn->privateData;
     virDomainObjPtr vm = NULL;
@@ -11644,6 +11644,45 @@ qemuDomainBlockJobImpl(virDomainPtr dom, const char *path, const char *base,
     ret = qemuMonitorBlockJob(priv->mon, device, base, bandwidth, info, mode);
     qemuDomainObjExitMonitorWithDriver(driver, vm);

+    /* Qemu provides asynchronous block job cancellation, but without
+     * the VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC flag libvirt guarantees a
+     * synchronous operation.  Provide this behavior by waiting here,
+     * so we don't get confused by newly scheduled block jobs.
+     */
+    if (ret == 0 && mode == BLOCK_JOB_ABORT &&
+        !(flags & VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC)) {
+        ret = 1;
+        while (1) {
+            /* Poll every 50ms */
+            struct timespec ts = { .tv_sec = 0,
+                                   .tv_nsec = 50 * 1000 * 1000ull };
+            virDomainBlockJobInfo dummy;
+
+            qemuDomainObjEnterMonitorWithDriver(driver, vm);
+            ret = qemuMonitorBlockJob(priv->mon, device, NULL, 0, &dummy,
+                                      BLOCK_JOB_INFO);
+            qemuDomainObjExitMonitorWithDriver(driver, vm);
+
+            if (ret <= 0)
+                break;
+
+            virDomainObjUnlock(vm);
+            qemuDriverUnlock(driver);
+
+            nanosleep(&ts, NULL);
+
+            qemuDriverLock(driver);
+            virDomainObjLock(vm);
+
+            if (!virDomainObjIsActive(vm)) {
+                qemuReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                                _("domain is not running"));
+                ret = -1;
+                break;
+            }
+        }
+    }
+
 endjob:
     if (qemuDomainObjEndJob(driver, vm) == 0) {
         vm = NULL;
@@ -11661,8 +11700,9 @@ cleanup:
 static int
 qemuDomainBlockJobAbort(virDomainPtr dom, const char *path, unsigned int flags)
 {
-    virCheckFlags(0, -1);
-    return qemuDomainBlockJobImpl(dom, path, NULL, 0, NULL, BLOCK_JOB_ABORT);
+    virCheckFlags(VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC, -1);
+    return qemuDomainBlockJobImpl(dom, path, NULL, 0, NULL, BLOCK_JOB_ABORT,
+                                  flags);
 }

 static int
@@ -11670,7 +11710,8 @@ qemuDomainGetBlockJobInfo(virDomainPtr dom, const char *path,
                            virDomainBlockJobInfoPtr info, unsigned int flags)
 {
     virCheckFlags(0, -1);
-    return qemuDomainBlockJobImpl(dom, path, NULL, 0, info, BLOCK_JOB_INFO);
+    return qemuDomainBlockJobImpl(dom, path, NULL, 0, info, BLOCK_JOB_INFO,
+                                  flags);
 }

 static int
@@ -11679,7 +11720,7 @@ qemuDomainBlockJobSetSpeed(virDomainPtr dom, const char *path,
 {
     virCheckFlags(0, -1);
     return qemuDomainBlockJobImpl(dom, path, NULL, bandwidth, NULL,
-                                  BLOCK_JOB_SPEED);
+                                  BLOCK_JOB_SPEED, flags);
 }

 static int
@@ -11690,10 +11731,10 @@ qemuDomainBlockRebase(virDomainPtr dom, const char *path, const char *base,

     virCheckFlags(0, -1);
     ret = qemuDomainBlockJobImpl(dom, path, base, bandwidth, NULL,
-                                 BLOCK_JOB_PULL);
+                                 BLOCK_JOB_PULL, flags);
     if (ret == 0 && bandwidth != 0)
         ret = qemuDomainBlockJobImpl(dom, path, NULL, bandwidth, NULL,
-                                     BLOCK_JOB_SPEED);
+                                     BLOCK_JOB_SPEED, flags);
     return ret;
 }

-- 
1.7.7.6