[Qemu-devel] [PATCH v4 02/10] block: add helper function to determine if a BDS is in a chain

[Jeff Cody]

This is a small helper function, to determine if 'base' is in the
chain of BlockDriverState 'top'.  It returns true if it is in the chain,
and false otherwise.

If either argument is NULL, it will also return false.

Reviewed-by: Benoit Canet <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Signed-off-by: Jeff Cody <address@hidden>
---
 block.c               | 11 +++++++++++
 include/block/block.h |  1 +
 2 files changed, 12 insertions(+)

diff --git a/block.c b/block.c
index 9882d3f..ad3fbc1 100644
--- a/block.c
+++ b/block.c
@@ -3812,6 +3812,17 @@ BlockDriverState *bdrv_lookup_bs(const char *device,
     return NULL;
 }
 
+/* If 'base' is in the same chain as 'top', return true. Otherwise,
+ * return false.  If either argument is NULL, return false. */
+bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base)
+{
+    while (top && top != base) {
+        top = top->backing_hd;
+    }
+
+    return top != NULL;
+}
+
 BlockDriverState *bdrv_next(BlockDriverState *bs)
 {
     if (!bs) {
diff --git a/include/block/block.h b/include/block/block.h
index faee3aa..4dc68be 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -404,6 +404,7 @@ BlockDeviceInfoList *bdrv_named_nodes_list(void);
 BlockDriverState *bdrv_lookup_bs(const char *device,
                                  const char *node_name,
                                  Error **errp);
+bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base);
 BlockDriverState *bdrv_next(BlockDriverState *bs);
 void bdrv_iterate(void (*it)(void *opaque, BlockDriverState *bs),
                   void *opaque);
-- 
1.9.3