[PULL 17/24] migration/block-dirty-bitmap: cancel migration on shutdown

[Eric Blake <eblake@redhat.com>]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

If target is turned off prior to postcopy finished, target crashes
because busy bitmaps are found at shutdown.
Canceling incoming migration helps, as it removes all unfinished (and
therefore busy) bitmaps.

Similarly on source we crash in bdrv_close_all which asserts that all
bdrv states are removed, because bdrv states involved into dirty bitmap
migration are referenced by it. So, we need to cancel outgoing
migration as well.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Message-Id: <20200727194236.19551-17-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 migration/migration.h          |  2 ++
 migration/block-dirty-bitmap.c | 16 ++++++++++++++++
 migration/migration.c          | 13 +++++++++++++
 3 files changed, 31 insertions(+)

diff --git a/migration/migration.h b/migration/migration.h
index ab20c756f549..6c6a931d0dc2 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -335,6 +335,8 @@ void migrate_send_rp_recv_bitmap(MigrationIncomingState *mis,
 void migrate_send_rp_resume_ack(MigrationIncomingState *mis, uint32_t value);

 void dirty_bitmap_mig_before_vm_start(void);
+void dirty_bitmap_mig_cancel_outgoing(void);
+void dirty_bitmap_mig_cancel_incoming(void);
 void migrate_add_address(SocketAddress *address);

 int foreach_not_ignored_block(RAMBlockIterFunc func, void *opaque);
diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
index f91015a4f88f..1f675b792fc9 100644
--- a/migration/block-dirty-bitmap.c
+++ b/migration/block-dirty-bitmap.c
@@ -657,6 +657,22 @@ static void cancel_incoming_locked(DBMLoadState *s)
     s->bitmaps = NULL;
 }

+void dirty_bitmap_mig_cancel_outgoing(void)
+{
+    dirty_bitmap_do_save_cleanup(&dbm_state.save);
+}
+
+void dirty_bitmap_mig_cancel_incoming(void)
+{
+    DBMLoadState *s = &dbm_state.load;
+
+    qemu_mutex_lock(&s->lock);
+
+    cancel_incoming_locked(s);
+
+    qemu_mutex_unlock(&s->lock);
+}
+
 static void dirty_bitmap_load_complete(QEMUFile *f, DBMLoadState *s)
 {
     GSList *item;
diff --git a/migration/migration.c b/migration/migration.c
index 1c61428988e9..8fe36339dbe8 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -188,6 +188,19 @@ void migration_shutdown(void)
      */
     migrate_fd_cancel(current_migration);
     object_unref(OBJECT(current_migration));
+
+    /*
+     * Cancel outgoing migration of dirty bitmaps. It should
+     * at least unref used block nodes.
+     */
+    dirty_bitmap_mig_cancel_outgoing();
+
+    /*
+     * Cancel incoming migration of dirty bitmaps. Dirty bitmaps
+     * are non-critical data, and their loss never considered as
+     * something serious.
+     */
+    dirty_bitmap_mig_cancel_incoming();
 }

 /* For outgoing */
-- 
2.27.0