migration: Fail migration on bdrv_flush_all() error

If bdrv_flush_all() returns an error, there is an inconsistency in the
view of an image file between the source and the destination host.
Completing the migration would lead to corruption. Better abort
migration in this case.

To reproduce this case, try the following (ensures that there is
something to flush, and then fails that flush):

$ qemu-img create -f qcow2 test.qcow2 1G
$ cat blkdebug.cfg
[inject-error]
event = "flush_to_os"
errno = "5"
$ qemu-system-x86_64 -hda blkdebug:blkdebug.cfg:test.qcow2 -monitor stdio
(qemu) qemu-io ide0-hd0 "write 0 4k"
(qemu) migrate ...

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/migration.c b/migration.c
index 635a7e7a08be67d194cc612d69b2fc36d6286a20..0681d8e5f18b145c7fbeea90a1c42a65f360b0b1 100644 (file)
--- a/migration.c
+++ b/migration.c
@@ -527,15 +527,26 @@ static void *migration_thread(void *opaque)
             if (pending_size && pending_size >= max_size) {
                 qemu_savevm_state_iterate(s->file);
             } else {
+                int ret;
+
                 DPRINTF("done iterating\n");
                 qemu_mutex_lock_iothread();
                 start_time = qemu_get_clock_ms(rt_clock);
                 qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
                 old_vm_running = runstate_is_running();
-                vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
-                qemu_file_set_rate_limit(s->file, INT_MAX);
-                qemu_savevm_state_complete(s->file);
+
+                ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
+                if (ret >= 0) {
+                    qemu_file_set_rate_limit(s->file, INT_MAX);
+                    qemu_savevm_state_complete(s->file);
+                }
                 qemu_mutex_unlock_iothread();
+
+                if (ret < 0) {
+                    migrate_finish_set_state(s, MIG_STATE_ERROR);
+                    break;
+                }
+
                 if (!qemu_file_get_error(s->file)) {
                     migrate_finish_set_state(s, MIG_STATE_COMPLETED);
                     break;