From: Michael Chapman <mike@very.puzzling.org>
Date: Mon, 30 Mar 2015 02:41:00 +0000 (+1100)
Subject: qemu: fix race between disk mirror fail and cancel
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=e5d729ba42d86eb3afa9799bca2944700fde41bb;p=libvirt.git

qemu: fix race between disk mirror fail and cancel

If a VM migration is aborted, a disk mirror may be failed by QEMU before
libvirt has a chance to cancel it. The disk->mirrorState remains at
_ABORT in this case, and this breaks subsequent mirrorings of that disk.

We should instead check the mirrorState directly and transition to _NONE
if it is already aborted. Do the check *after* aborting the block job in
QEMU to avoid a race.

Signed-off-by: Michael Chapman <mike@very.puzzling.org>
---

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 724e3ff24b..155333ea6f 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -1853,6 +1853,10 @@ qemuMigrationDriveMirror(virQEMUDriverPtr driver,
         } else {
             VIR_WARN("Unable to enter monitor. No block job cancelled");
         }
+
+        /* If disk mirror is already aborted, clear the mirror state now */
+        if (disk->mirrorState == VIR_DOMAIN_DISK_MIRROR_STATE_ABORT)
+            disk->mirrorState = VIR_DOMAIN_DISK_MIRROR_STATE_NONE;
     }
     if (err)
         virSetError(err);
@@ -1921,6 +1925,10 @@ qemuMigrationCancelDriveMirror(qemuMigrationCookiePtr mig,
             ret = -1;
             goto cleanup;
         }
+
+        /* If disk mirror is already aborted, clear the mirror state now */
+        if (disk->mirrorState == VIR_DOMAIN_DISK_MIRROR_STATE_ABORT)
+            disk->mirrorState = VIR_DOMAIN_DISK_MIRROR_STATE_NONE;
     }
 
  cleanup: