block: New bdrv_next()

This is a more flexible alternative to bdrv_iterate().
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block.c

@@ -1330,6 +1330,14 @@ BlockDriverState *bdrv_find(const char *name)
     return NULL;
 }
 
+BlockDriverState *bdrv_next(BlockDriverState *bs)
+{
+    if (!bs) {
+        return QTAILQ_FIRST(&bdrv_states);
+    }
+    return QTAILQ_NEXT(bs, list);
+}
+
 void bdrv_iterate(void (*it)(void *opaque, BlockDriverState *bs), void *opaque)
 {
     BlockDriverState *bs;

block.h

@@ -168,6 +168,7 @@ void bdrv_set_change_cb(BlockDriverState *bs,
                         void (*change_cb)(void *opaque), void *opaque);
 void bdrv_get_format(BlockDriverState *bs, char *buf, int buf_size);
 BlockDriverState *bdrv_find(const char *name);
+BlockDriverState *bdrv_next(BlockDriverState *bs);
 void bdrv_iterate(void (*it)(void *opaque, BlockDriverState *bs),
                   void *opaque);
 int bdrv_is_encrypted(BlockDriverState *bs);