block: Drop detached child from ignore list

bdrv_attach_child_common_abort() restores the parent's AioContext.  To
do so, the child (which was supposed to be attached, but is now detached
again by this abort handler) is added to the ignore list for the
AioContext changing functions.

However, since we modify a BDS's children list in the BdrvChildClass's
.attach and .detach handlers, the child is already effectively detached
from the parent by this point.  We do not need to put it into the ignore
list.

Use this opportunity to clean up the empty line structure: Keep setting
the ignore list, invoking the AioContext function, and freeing the
ignore list in blocks separated by empty lines.

Signed-off-by: Hanna Reitz <[email protected]>
Reviewed-by: Kevin Wolf <[email protected]>
Reviewed-by: Vladimir Sementsov-Ogievskiy <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Hanna Reitz <[email protected]>

Author: XanClic

block.c

@@ -2774,14 +2774,16 @@ static void bdrv_attach_child_common_abort(void *opaque)
     }
 
     if (bdrv_child_get_parent_aio_context(child) != s->old_parent_ctx) {
-        GSList *ignore = g_slist_prepend(NULL, child);
+        GSList *ignore;
 
+        /* No need to ignore `child`, because it has been detached already */
+        ignore = NULL;
         child->klass->can_set_aio_ctx(child, s->old_parent_ctx, &ignore,
                                       &error_abort);
         g_slist_free(ignore);
-        ignore = g_slist_prepend(NULL, child);
-        child->klass->set_aio_ctx(child, s->old_parent_ctx, &ignore);
 
+        ignore = NULL;
+        child->klass->set_aio_ctx(child, s->old_parent_ctx, &ignore);
         g_slist_free(ignore);
     }