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-rw-r--r--include/block/block.h25
1 files changed, 25 insertions, 0 deletions
diff --git a/include/block/block.h b/include/block/block.h
index a81645e..60f0047 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -612,6 +612,9 @@ void bdrv_parent_drained_begin_single(BdrvChild *c, bool poll);
* bdrv_parent_drained_end_single:
*
* End a quiesced section for the parent of @c.
+ *
+ * This polls @bs's AioContext until all scheduled sub-drained_ends
+ * have settled, which may result in graph changes.
*/
void bdrv_parent_drained_end_single(BdrvChild *c);
@@ -661,10 +664,32 @@ void bdrv_subtree_drained_begin(BlockDriverState *bs);
* bdrv_drained_end:
*
* End a quiescent section started by bdrv_drained_begin().
+ *
+ * This polls @bs's AioContext until all scheduled sub-drained_ends
+ * have settled. On one hand, that may result in graph changes. On
+ * the other, this requires that all involved nodes (@bs and all of
+ * its parents) are in the same AioContext, and that the caller has
+ * acquired it.
+ * If there are any nodes that are in different contexts from @bs,
+ * these contexts must not be acquired.
*/
void bdrv_drained_end(BlockDriverState *bs);
/**
+ * bdrv_drained_end_no_poll:
+ *
+ * Same as bdrv_drained_end(), but do not poll for the subgraph to
+ * actually become unquiesced. Therefore, no graph changes will occur
+ * with this function.
+ *
+ * *drained_end_counter is incremented for every background operation
+ * that is scheduled, and will be decremented for every operation once
+ * it settles. The caller must poll until it reaches 0. The counter
+ * should be accessed using atomic operations only.
+ */
+void bdrv_drained_end_no_poll(BlockDriverState *bs, int *drained_end_counter);
+
+/**
* End a quiescent section started by bdrv_subtree_drained_begin().
*/
void bdrv_subtree_drained_end(BlockDriverState *bs);