[PATCH 09/16] migration: Drop cached migration state in migration_maybe_pause()

[Peter Xu <peterx@redhat.com>]

I can't see why we must cache the state now after we avoided possible
CANCEL race: that's the only thing I can think of that can modify the
migration state concurrently with the migration thread itself.  Make all
the state updates to happen always, then we don't need to cache the state
anymore.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 migration/migration.c | 27 ++++++++-------------------
 1 file changed, 8 insertions(+), 19 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 5c688059de..5850c90c9f 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -102,9 +102,7 @@ static MigrationIncomingState *current_incoming;
 static GSList *migration_blockers[MIG_MODE__MAX];
 
 static bool migration_object_check(MigrationState *ms, Error **errp);
-static int migration_maybe_pause(MigrationState *s,
-                                 int *current_active_state,
-                                 int new_state);
+static int migration_maybe_pause(MigrationState *s, int new_state);
 static void migrate_fd_cancel(MigrationState *s);
 static bool close_return_path_on_source(MigrationState *s);
 static void migration_completion_end(MigrationState *s);
@@ -2502,7 +2500,6 @@ static int postcopy_start(MigrationState *ms, Error **errp)
     int ret;
     QIOChannelBuffer *bioc;
     QEMUFile *fb;
-    int cur_state = MIGRATION_STATUS_ACTIVE;
 
     /*
      * Now we're 100% sure to switch to postcopy, so JSON writer won't be
@@ -2537,8 +2534,7 @@ static int postcopy_start(MigrationState *ms, Error **errp)
         goto fail;
     }
 
-    ret = migration_maybe_pause(ms, &cur_state,
-                                MIGRATION_STATUS_POSTCOPY_ACTIVE);
+    ret = migration_maybe_pause(ms, MIGRATION_STATUS_POSTCOPY_ACTIVE);
     if (ret < 0) {
         error_setg_errno(errp, -ret, "%s: Failed in migration_maybe_pause()",
                          __func__);
@@ -2676,9 +2672,7 @@ fail:
  * migrate_pause_before_switchover called with the BQL locked
  * Returns: 0 on success
  */
-static int migration_maybe_pause(MigrationState *s,
-                                 int *current_active_state,
-                                 int new_state)
+static int migration_maybe_pause(MigrationState *s, int new_state)
 {
     if (!migrate_pause_before_switchover()) {
         return 0;
@@ -2701,21 +2695,19 @@ static int migration_maybe_pause(MigrationState *s,
      * wait for the 'pause_sem' semaphore.
      */
     if (s->state != MIGRATION_STATUS_CANCELLING) {
-        migrate_set_state(&s->state, *current_active_state,
+        migrate_set_state(&s->state, s->state,
                           MIGRATION_STATUS_PRE_SWITCHOVER);
         bql_unlock();
         qemu_sem_wait(&s->pause_sem);
         bql_lock();
         migrate_set_state(&s->state, MIGRATION_STATUS_PRE_SWITCHOVER,
                           new_state);
-        *current_active_state = new_state;
     }
 
     return s->state == new_state ? 0 : -EINVAL;
 }
 
-static int migration_completion_precopy(MigrationState *s,
-                                        int *current_active_state)
+static int migration_completion_precopy(MigrationState *s)
 {
     int ret;
 
@@ -2728,8 +2720,7 @@ static int migration_completion_precopy(MigrationState *s,
         }
     }
 
-    ret = migration_maybe_pause(s, current_active_state,
-                                MIGRATION_STATUS_DEVICE);
+    ret = migration_maybe_pause(s, MIGRATION_STATUS_DEVICE);
     if (ret < 0) {
         goto out_unlock;
     }
@@ -2782,11 +2773,10 @@ static void migration_completion_postcopy(MigrationState *s)
 static void migration_completion(MigrationState *s)
 {
     int ret = 0;
-    int current_active_state = s->state;
     Error *local_err = NULL;
 
     if (s->state == MIGRATION_STATUS_ACTIVE) {
-        ret = migration_completion_precopy(s, &current_active_state);
+        ret = migration_completion_precopy(s);
     } else if (s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
         migration_completion_postcopy(s);
     } else {
@@ -2826,8 +2816,7 @@ fail:
         error_free(local_err);
     }
 
-    migrate_set_state(&s->state, current_active_state,
-                      MIGRATION_STATUS_FAILED);
+    migrate_set_state(&s->state, s->state, MIGRATION_STATUS_FAILED);
 }
 
 /**
-- 
2.47.0