block: Add blk_next_root_bs()

This function iterates over all BDSs attached to a BB. We are going to
need it when rewriting bdrv_next() so it no longer uses bdrv_states.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

2 files changed, 25 insertions, 0 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index b3c3d39db8..7818aa2634 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -250,6 +250,30 @@ BlockBackend *blk_next(BlockBackend *blk)
 }
 
 /*
+ * Iterates over all BlockDriverStates which are attached to a BlockBackend.
+ * This function is for use by bdrv_next().
+ *
+ * @bs must be NULL or a BDS that is attached to a BB.
+ */
+BlockDriverState *blk_next_root_bs(BlockDriverState *bs)
+{
+    BlockBackend *blk;
+
+    if (bs) {
+        assert(bs->blk);
+        blk = bs->blk;
+    } else {
+        blk = NULL;
+    }
+
+    do {
+        blk = blk_all_next(blk);
+    } while (blk && !blk->bs);
+
+    return blk ? blk->bs : NULL;
+}
+
+/*
  * Add a BlockBackend into the list of backends referenced by the monitor, with
  * the given @name acting as the handle for the monitor.
  * Strictly for use by blockdev.c.
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 60c4b070ca..d839bffeb0 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -70,6 +70,7 @@ void blk_remove_all_bs(void);
 const char *blk_name(BlockBackend *blk);
 BlockBackend *blk_by_name(const char *name);
 BlockBackend *blk_next(BlockBackend *blk);
+BlockDriverState *blk_next_root_bs(BlockDriverState *bs);
 bool monitor_add_blk(BlockBackend *blk, const char *name, Error **errp);
 void monitor_remove_blk(BlockBackend *blk);