[PATCH v3 2/5] migration: Create MigrationState active field

[Juan Quintela <quintela@redhat.com>]

Right now, there is no easy way to dectect if we have already
cancelled/finished/failed a migration.  This field is setup to true
when we start a migration, and it is set to false as soon as we stop
it.

It fixes a real bug, in ram_save_iterate() we call functions that
wrote to the channel even if we know that migration has stopped for
any reason.  This gives problems with multifd because we need to
synchronize various semoaphores that we don't want to take.

Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 migration/migration.c | 5 +++++
 migration/migration.h | 5 +++++
 migration/ram.c       | 2 +-
 migration/savevm.c    | 2 ++
 4 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/migration/migration.c b/migration/migration.c
index 990bff00c0..60bc8710b6 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1583,6 +1583,8 @@ static void migrate_fd_cancel(MigrationState *s)
     QEMUFile *f = migrate_get_current()->to_dst_file;
     trace_migrate_fd_cancel();
 
+    s->active = false;
+
     if (s->rp_state.from_dst_file) {
         /* shutdown the rp socket, so causing the rp thread to shutdown */
         qemu_file_shutdown(s->rp_state.from_dst_file);
@@ -2834,6 +2836,7 @@ static void migration_completion(MigrationState *s)
     }
 
     if (!migrate_colo_enabled()) {
+        s->active = false;
         migrate_set_state(&s->state, current_active_state,
                           MIGRATION_STATUS_COMPLETED);
     }
@@ -2859,6 +2862,7 @@ fail_invalidate:
     }
 
 fail:
+    s->active = false;
     migrate_set_state(&s->state, current_active_state,
                       MIGRATION_STATUS_FAILED);
 }
@@ -3289,6 +3293,7 @@ static void *migration_thread(void *opaque)
     }
 
     qemu_savevm_state_setup(s->to_dst_file);
+    s->active = true;
 
     if (qemu_savevm_nr_failover_devices()) {
         migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
diff --git a/migration/migration.h b/migration/migration.h
index aa9ff6f27b..e0386efe95 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -169,6 +169,11 @@ struct MigrationState
 
     int state;
 
+    /* Is the migration channel still open.  When migration finish,
+     * gets an error or is cancelled this becomes false.
+     */
+
+    bool active;
     /* State related to return path */
     struct {
         QEMUFile     *from_dst_file;
diff --git a/migration/ram.c b/migration/ram.c
index 8f9f3bba5b..44ca56e1ea 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3521,7 +3521,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
     ram_control_after_iterate(f, RAM_CONTROL_ROUND);
 
 out:
-    if (ret >= 0) {
+    if (ret >= 0 && migrate_get_current()->active) {
         multifd_send_sync_main(rs);
         qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
         qemu_fflush(f);
diff --git a/migration/savevm.c b/migration/savevm.c
index adfdca26ac..3efde5b3dd 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1550,6 +1550,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
     qemu_mutex_unlock_iothread();
     qemu_savevm_state_header(f);
     qemu_savevm_state_setup(f);
+    ms->active = true;
     qemu_mutex_lock_iothread();
 
     while (qemu_file_get_error(f) == 0) {
@@ -1574,6 +1575,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
         status = MIGRATION_STATUS_COMPLETED;
     }
     migrate_set_state(&ms->state, MIGRATION_STATUS_SETUP, status);
+    ms->active = false;
 
     /* f is outer parameter, it should not stay in global migration state after
      * this function finished */
-- 
2.24.1