[Qemu-devel] [PATCH v6 for 2.1 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 da32bb0..280a167 100644
--- a/block.c
+++ b/block.c
@@ -3819,6 +3819,17 @@ 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 f15b99b..c60bd52 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -403,6 +403,7 @@ 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