Re: [PATCH RFC 06/11] migration/block: Extend the migration_block_* API to dest side

[Peter Xu <peterx@redhat.com>]

On Tue, Dec 03, 2024 at 07:51:33PM -0500, Peter Xu wrote:
> diff --git a/migration/migration.c b/migration/migration.c
> index 8f7d09ca84..e01264168f 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -701,6 +701,12 @@ migration_incoming_state_setup(MigrationIncomingState *mis, Error **errp)
>          return false;
>      }
>  
> +    /*
> +     * Newly setup QEMU, prepared for incoming migration.  Mark the block
> +     * active state to reflect that the src currently owns the disks.
> +     */
> +    migrate_get_current()->block_active = false;
> +
>      migrate_set_state(&mis->state, current, MIGRATION_STATUS_SETUP);
>      return true;
>  }

I plan to move this over to the end of qmp_migrate_incoming(), which might
be easier to follow (where we updated "once"..), to say that we initialize
the value to FALSE once and for all for an incoming instance.

I don't think there's any functional change on the fixup.  The only
difference is when qemu_start_incoming_migration() can fail after
migration_incoming_state_setup().  I don't think it matter hugely on the
block_active flag itself.. as if that failure happens it means the next
qmp_migrate_incoming will overwrite the flag again with nobody being able
to touch it..  But still, if I'll post a new version I'll squash below into
this patch:

===8<===
diff --git a/migration/migration.c b/migration/migration.c
index 1a1c570c5b..bc3a29482a 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -701,12 +701,6 @@ migration_incoming_state_setup(MigrationIncomingState *mis, Error **errp)
         return false;
     }
 
-    /*
-     * Newly setup QEMU, prepared for incoming migration.  Mark the block
-     * active state to reflect that the src currently owns the disks.
-     */
-    migrate_get_current()->block_active = false;
-
     migrate_set_state(&mis->state, current, MIGRATION_STATUS_SETUP);
     return true;
 }
@@ -1892,6 +1886,12 @@ void qmp_migrate_incoming(const char *uri, bool has_channels,
         return;
     }
 
+    /*
+     * Newly setup incoming QEMU.  Mark the block active state to reflect
+     * that the src currently owns the disks.
+     */
+    migrate_get_current()->block_active = false;
+
     once = false;
 }

-- 
Peter Xu