[Qemu-block] [PATCH 3/3] block: prohibit migration during transactions

[John Snow]

Similarly to BlockJobs, prohibit migration at least
during the synchronous phase of a transaction.

In particular, this guards internal and external
snapshots, which are implemented via transaction actions
through blockdev_do_action.

Signed-off-by: John Snow <address@hidden>
---
 blockdev.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/blockdev.c b/blockdev.c
index 32b04b4..231dcf6 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -49,6 +49,7 @@
 #include "qmp-commands.h"
 #include "trace.h"
 #include "sysemu/arch_init.h"
+#include "migration/migration.h"
 
 static const char *const if_name[IF_COUNT] = {
     [IF_NONE] = "none",
@@ -1759,6 +1760,14 @@ void qmp_transaction(TransactionActionList *dev_list, 
Error **errp)
     TransactionActionList *dev_entry = dev_list;
     BlkTransactionState *state, *next;
     Error *local_err = NULL;
+    Error *blocker = NULL;
+    int ret;
+
+    error_setg(&blocker, "Block device(s) are in use by a Block Transaction");
+    ret = migrate_add_blocker(blocker, errp);
+    if (ret < 0) {
+        goto cleanup_mig;
+    }
 
     QSIMPLEQ_HEAD(snap_bdrv_states, BlkTransactionState) snap_bdrv_states;
     QSIMPLEQ_INIT(&snap_bdrv_states);
@@ -1814,6 +1823,9 @@ exit:
         }
         g_free(state);
     }
+ cleanup_mig:
+    migrate_del_blocker(blocker);
+    error_free(blocker);
 }
 
 
-- 
2.4.3