[PATCH v7 02/47] block: Add chain helper functions

[Max Reitz]

Add some helper functions for skipping filters in a chain of block
nodes.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 include/block/block_int.h |  3 +++
 block.c                   | 55 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index bb3457c5e8..5da793bfc3 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -1382,6 +1382,9 @@ BdrvChild *bdrv_cow_child(BlockDriverState *bs);
 BdrvChild *bdrv_filter_child(BlockDriverState *bs);
 BdrvChild *bdrv_filter_or_cow_child(BlockDriverState *bs);
 BdrvChild *bdrv_primary_child(BlockDriverState *bs);
+BlockDriverState *bdrv_skip_implicit_filters(BlockDriverState *bs);
+BlockDriverState *bdrv_skip_filters(BlockDriverState *bs);
+BlockDriverState *bdrv_backing_chain_next(BlockDriverState *bs);
 
 static inline BlockDriverState *child_bs(BdrvChild *child)
 {
diff --git a/block.c b/block.c
index 5a42ef49fd..0a0b855261 100644
--- a/block.c
+++ b/block.c
@@ -7008,3 +7008,58 @@ BdrvChild *bdrv_primary_child(BlockDriverState *bs)
 
     return NULL;
 }
+
+static BlockDriverState *bdrv_do_skip_filters(BlockDriverState *bs,
+                                              bool stop_on_explicit_filter)
+{
+    BdrvChild *c;
+
+    if (!bs) {
+        return NULL;
+    }
+
+    while (!(stop_on_explicit_filter && !bs->implicit)) {
+        c = bdrv_filter_child(bs);
+        if (!c) {
+            break;
+        }
+        bs = c->bs;
+    }
+    /*
+     * Note that this treats nodes with bs->drv == NULL as not being
+     * filters (bs->drv == NULL should be replaced by something else
+     * anyway).
+     * The advantage of this behavior is that this function will thus
+     * always return a non-NULL value (given a non-NULL @bs).
+     */
+
+    return bs;
+}
+
+/*
+ * Return the first BDS that has not been added implicitly or that
+ * does not have a filtered child down the chain starting from @bs
+ * (including @bs itself).
+ */
+BlockDriverState *bdrv_skip_implicit_filters(BlockDriverState *bs)
+{
+    return bdrv_do_skip_filters(bs, true);
+}
+
+/*
+ * Return the first BDS that does not have a filtered child down the
+ * chain starting from @bs (including @bs itself).
+ */
+BlockDriverState *bdrv_skip_filters(BlockDriverState *bs)
+{
+    return bdrv_do_skip_filters(bs, false);
+}
+
+/*
+ * For a backing chain, return the first non-filter backing image of
+ * the first non-filter image.
+ */
+BlockDriverState *bdrv_backing_chain_next(BlockDriverState *bs)
+{
+    return bdrv_skip_filters(bdrv_cow_bs(bdrv_skip_filters(bs)));
+}
-- 
2.26.2