An internal version that removes -only-migratable implications.  It can be used
for temporary migration blockers like dump-guest-memory.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/migration/blocker.h | 16 ++++++++++++++++
 migration/migration.c       | 21 +++++++++++++--------
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/include/migration/blocker.h b/include/migration/blocker.h
index acd27018e9..9cebe2ba06 100644
--- a/include/migration/blocker.h
+++ b/include/migration/blocker.h
@@ -25,6 +25,22 @@
  */
 int migrate_add_blocker(Error *reason, Error **errp);
 
+/**
+ * @migrate_add_blocker_internal - prevent migration from proceeding without
+ *                                 only-migrate implications
+ *
+ * @reason - an error to be returned whenever migration is attempted
+ *
+ * @errp - [out] The reason (if any) we cannot block migration right now.
+ *
+ * @returns - 0 on success, -EBUSY on failure, with errp set.
+ *
+ * Some of the migration blockers can be temporary (e.g., for a few seconds),
+ * so it shouldn't need to conflict with "-only-migratable".  For those cases,
+ * we can call this function rather than @migrate_add_blocker().
+ */
+int migrate_add_blocker_internal(Error *reason, Error **errp);
+
 /**
  * @migrate_del_blocker - remove a blocking error from migration
  *
diff --git a/migration/migration.c b/migration/migration.c
index 041b8451a6..41429680c2 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2053,15 +2053,8 @@ void migrate_init(MigrationState *s)
     s->threshold_size = 0;
 }
 
-int migrate_add_blocker(Error *reason, Error **errp)
+int migrate_add_blocker_internal(Error *reason, Error **errp)
 {
-    if (only_migratable) {
-        error_propagate_prepend(errp, error_copy(reason),
-                                "disallowing migration blocker "
-                                "(--only-migratable) for: ");
-        return -EACCES;
-    }
-
     if (migration_is_idle()) {
         migration_blockers = g_slist_prepend(migration_blockers, reason);
         return 0;
@@ -2073,6 +2066,18 @@ int migrate_add_blocker(Error *reason, Error **errp)
     return -EBUSY;
 }
 
+int migrate_add_blocker(Error *reason, Error **errp)
+{
+    if (only_migratable) {
+        error_propagate_prepend(errp, error_copy(reason),
+                                "disallowing migration blocker "
+                                "(--only-migratable) for: ");
+        return -EACCES;
+    }
+
+    return migrate_add_blocker_internal(reason, errp);
+}
+
 void migrate_del_blocker(Error *reason)
 {
     migration_blockers = g_slist_remove(migration_blockers, reason);
-- 
2.31.1

On Tue, Aug 24, 2021 at 7:27 PM Peter Xu <peterx@redhat.com> wrote:

> An internal version that removes -only-migratable implications.  It can be
> used
> for temporary migration blockers like dump-guest-memory.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

---
>  include/migration/blocker.h | 16 ++++++++++++++++
>  migration/migration.c       | 21 +++++++++++++--------
>  2 files changed, 29 insertions(+), 8 deletions(-)
>
> diff --git a/include/migration/blocker.h b/include/migration/blocker.h
> index acd27018e9..9cebe2ba06 100644
> --- a/include/migration/blocker.h
> +++ b/include/migration/blocker.h
> @@ -25,6 +25,22 @@
>   */
>  int migrate_add_blocker(Error *reason, Error **errp);
>
> +/**
> + * @migrate_add_blocker_internal - prevent migration from proceeding
> without
> + *                                 only-migrate implications
> + *
> + * @reason - an error to be returned whenever migration is attempted
> + *
> + * @errp - [out] The reason (if any) we cannot block migration right now.
> + *
> + * @returns - 0 on success, -EBUSY on failure, with errp set.
> + *
> + * Some of the migration blockers can be temporary (e.g., for a few
> seconds),
> + * so it shouldn't need to conflict with "-only-migratable".  For those
> cases,
> + * we can call this function rather than @migrate_add_blocker().
> + */
> +int migrate_add_blocker_internal(Error *reason, Error **errp);
> +
>  /**
>   * @migrate_del_blocker - remove a blocking error from migration
>   *
> diff --git a/migration/migration.c b/migration/migration.c
> index 041b8451a6..41429680c2 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -2053,15 +2053,8 @@ void migrate_init(MigrationState *s)
>      s->threshold_size = 0;
>  }
>
> -int migrate_add_blocker(Error *reason, Error **errp)
> +int migrate_add_blocker_internal(Error *reason, Error **errp)
>  {
> -    if (only_migratable) {
> -        error_propagate_prepend(errp, error_copy(reason),
> -                                "disallowing migration blocker "
> -                                "(--only-migratable) for: ");
> -        return -EACCES;
> -    }
> -
>      if (migration_is_idle()) {
>          migration_blockers = g_slist_prepend(migration_blockers, reason);
>          return 0;
> @@ -2073,6 +2066,18 @@ int migrate_add_blocker(Error *reason, Error **errp)
>      return -EBUSY;
>  }
>
> +int migrate_add_blocker(Error *reason, Error **errp)
> +{
> +    if (only_migratable) {
> +        error_propagate_prepend(errp, error_copy(reason),
> +                                "disallowing migration blocker "
> +                                "(--only-migratable) for: ");
> +        return -EACCES;
> +    }
> +
> +    return migrate_add_blocker_internal(reason, errp);
> +}
> +
>  void migrate_del_blocker(Error *reason)
>  {
>      migration_blockers = g_slist_remove(migration_blockers, reason);
> --
> 2.31.1
>
>

Peter Xu <peterx@redhat.com> wrote:
> An internal version that removes -only-migratable implications.  It can be used
> for temporary migration blockers like dump-guest-memory.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>