Merge remote-tracking branch 'remotes/juanquintela/tags/migration/20170206' into staging

migration/next for 20170206

# gpg: Signature made Mon 06 Feb 2017 16:13:26 GMT
# gpg:                using RSA key 0xF487EF185872D723
# gpg: Good signature from "Juan Quintela <quintela@redhat.com>"
# gpg:                 aka "Juan Quintela <quintela@trasno.org>"
# Primary key fingerprint: 1899 FF8E DEBF 58CC EE03  4B82 F487 EF18 5872 D723

* remotes/juanquintela/tags/migration/20170206:
  postcopy: Recover block devices on early failure
  Postcopy: Reset state to avoid cleanup assert
  vmstate registration: check return values
  migration: Check for ID length
  vmstate_register_with_alias_id: Take an Error **
  migration: create Migration Incoming State at init time

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 42 insertions, 21 deletions

diff --git a/migration/migration.c b/migration/migration.c
index 2766d2f586..2b179c69fa 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -111,32 +111,28 @@ MigrationState *migrate_get_current(void)
     return &current_migration;
 }
 
-/* For incoming */
-static MigrationIncomingState *mis_current;
-
 MigrationIncomingState *migration_incoming_get_current(void)
 {
-    return mis_current;
-}
-
-MigrationIncomingState *migration_incoming_state_new(QEMUFile* f)
-{
-    mis_current = g_new0(MigrationIncomingState, 1);
-    mis_current->from_src_file = f;
-    mis_current->state = MIGRATION_STATUS_NONE;
-    QLIST_INIT(&mis_current->loadvm_handlers);
-    qemu_mutex_init(&mis_current->rp_mutex);
-    qemu_event_init(&mis_current->main_thread_load_event, false);
+    static bool once;
+    static MigrationIncomingState mis_current;
 
-    return mis_current;
+    if (!once) {
+        mis_current.state = MIGRATION_STATUS_NONE;
+        memset(&mis_current, 0, sizeof(MigrationIncomingState));
+        QLIST_INIT(&mis_current.loadvm_handlers);
+        qemu_mutex_init(&mis_current.rp_mutex);
+        qemu_event_init(&mis_current.main_thread_load_event, false);
+        once = true;
+    }
+    return &mis_current;
 }
 
 void migration_incoming_state_destroy(void)
 {
-    qemu_event_destroy(&mis_current->main_thread_load_event);
-    loadvm_free_handlers(mis_current);
-    g_free(mis_current);
-    mis_current = NULL;
+    struct MigrationIncomingState *mis = migration_incoming_get_current();
+
+    qemu_event_destroy(&mis->main_thread_load_event);
+    loadvm_free_handlers(mis);
 }
 
 
@@ -382,11 +378,11 @@ static void process_incoming_migration_bh(void *opaque)
 static void process_incoming_migration_co(void *opaque)
 {
     QEMUFile *f = opaque;
-    MigrationIncomingState *mis;
+    MigrationIncomingState *mis = migration_incoming_get_current();
     PostcopyState ps;
     int ret;
 
-    mis = migration_incoming_state_new(f);
+    mis->from_src_file = f;
     postcopy_state_set(POSTCOPY_INCOMING_NONE);
     migrate_set_state(&mis->state, MIGRATION_STATUS_NONE,
                       MIGRATION_STATUS_ACTIVE);
@@ -1605,6 +1601,7 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running)
     QIOChannelBuffer *bioc;
     QEMUFile *fb;
     int64_t time_at_stop = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+    bool restart_block = false;
     migrate_set_state(&ms->state, MIGRATION_STATUS_ACTIVE,
                       MIGRATION_STATUS_POSTCOPY_ACTIVE);
 
@@ -1624,6 +1621,7 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running)
     if (ret < 0) {
         goto fail;
     }
+    restart_block = true;
 
     /*
      * Cause any non-postcopiable, but iterative devices to
@@ -1680,6 +1678,18 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running)
 
     /* <><> end of stuff going into the package */
 
+    /* Last point of recovery; as soon as we send the package the destination
+     * can open devices and potentially start running.
+     * Lets just check again we've not got any errors.
+     */
+    ret = qemu_file_get_error(ms->to_dst_file);
+    if (ret) {
+        error_report("postcopy_start: Migration stream errored (pre package)");
+        goto fail_closefb;
+    }
+
+    restart_block = false;
+
     /* Now send that blob */
     if (qemu_savevm_send_packaged(ms->to_dst_file, bioc->data, bioc->usage)) {
         goto fail_closefb;
@@ -1717,6 +1727,17 @@ fail_closefb:
 fail:
     migrate_set_state(&ms->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
                           MIGRATION_STATUS_FAILED);
+    if (restart_block) {
+        /* A failure happened early enough that we know the destination hasn't
+         * accessed block devices, so we're safe to recover.
+         */
+        Error *local_err = NULL;
+
+        bdrv_invalidate_cache_all(&local_err);
+        if (local_err) {
+            error_report_err(local_err);
+        }
+    }
     qemu_mutex_unlock_iothread();
     return -1;
 }