[PATCH 05/21] migration: Add a flag to track block-bitmap-mapping input

[Fabiano Rosas]

The QAPI converts an empty list on the block-bitmap-mapping input into
a NULL BitmapMigrationNodeAliasList. The empty list is a valid input
for the block-bitmap-mapping option, so commit 3cba22c9ad ("migration:
Fix block_bitmap_mapping migration") started using the
s->parameters.has_block_bitmap_mapping field to tell when the user has
passed in an empty list vs. when no list has been passed at all.

However, using the has_block_bitmap_mapping field of s->parameters is
only possible because MigrationParameters has had its members made
optional due to historical reasons.

In order to make improvements to the way configuration options are set
for a migration, we'd like to reduce the usage of the has_* fields of
the global configuration object (s->parameters).

Add a separate boolean to track the status of the block_bitmap_mapping
option.

(this was verified to not regress iotest 300, which is the test that
3cba22c9ad refers to)

Signed-off-by: Fabiano Rosas <faro...@suse.de>
---
 migration/migration.h | 7 +++++++
 migration/options.c   | 6 +++---
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/migration/migration.h b/migration/migration.h
index d53f7cad84..ab797540b0 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -510,6 +510,13 @@ struct MigrationState {
     bool rdma_migration;
 
     GSource *hup_source;
+
+    /*
+     * The block-bitmap-mapping option is allowed to be an emtpy list,
+     * therefore we need a way to know wheter the user has given
+     * anything as input.
+     */
+    bool has_block_bitmap_mapping;
 };
 
 void migrate_set_state(MigrationStatus *state, MigrationStatus old_state,
diff --git a/migration/options.c b/migration/options.c
index f64e141394..cf77826204 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -685,7 +685,7 @@ bool migrate_has_block_bitmap_mapping(void)
 {
     MigrationState *s = migrate_get_current();
 
-    return s->parameters.has_block_bitmap_mapping;
+    return s->has_block_bitmap_mapping;
 }
 
 uint32_t migrate_checkpoint_delay(void)
@@ -989,7 +989,7 @@ MigrationParameters *qmp_query_migrate_parameters(Error 
**errp)
     params->has_announce_step = true;
     params->announce_step = s->parameters.announce_step;
 
-    if (s->parameters.has_block_bitmap_mapping) {
+    if (s->has_block_bitmap_mapping) {
         params->has_block_bitmap_mapping = true;
         params->block_bitmap_mapping =
             QAPI_CLONE(BitmapMigrationNodeAliasList,
@@ -1469,7 +1469,7 @@ static void migrate_params_apply(MigrationParameters 
*params)
         qapi_free_BitmapMigrationNodeAliasList(
             s->parameters.block_bitmap_mapping);
 
-        s->parameters.has_block_bitmap_mapping = true;
+        s->has_block_bitmap_mapping = true;
         s->parameters.block_bitmap_mapping =
             QAPI_CLONE(BitmapMigrationNodeAliasList,
                        params->block_bitmap_mapping);
-- 
2.35.3