[Qemu-devel] [PATCH v2 03/11] block: Add overlay BDS pointer into the BlockDriverState struct

[Jeff Cody]

Now that node-names can reference an individual BlockDriverState without
needing to navigate downwards from the 'device' level, in order to find
the top-most image (active layer) we need a pointer to the overlay of a
BDS.

This will allow QMP commands to reference an image solely by its
node-name, without also needing to pass in the corresponding 'device'
string.

Signed-off-by: Jeff Cody <address@hidden>
---
 block.c                   | 5 +++++
 include/block/block_int.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/block.c b/block.c
index cf4b296..b72fe4e 100644
--- a/block.c
+++ b/block.c
@@ -1114,6 +1114,9 @@ void bdrv_set_backing_hd(BlockDriverState *bs, 
BlockDriverState *backing_hd)
     if (bs->backing_hd) {
         assert(bs->backing_blocker);
         bdrv_op_unblock_all(bs->backing_hd, bs->backing_blocker);
+        if (!backing_hd) {
+            bs->backing_hd->overlay = NULL;
+        }
     } else if (backing_hd) {
         error_setg(&bs->backing_blocker,
                    "device is used as backing hd of '%s'",
@@ -1126,6 +1129,8 @@ void bdrv_set_backing_hd(BlockDriverState *bs, 
BlockDriverState *backing_hd)
         bs->backing_blocker = NULL;
         goto out;
     }
+    backing_hd->overlay = bs;
+
     bs->open_flags &= ~BDRV_O_NO_BACKING;
     pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_hd->filename);
     pstrcpy(bs->backing_format, sizeof(bs->backing_format),
diff --git a/include/block/block_int.h b/include/block/block_int.h
index f2e753f..c0fe90b 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -303,6 +303,7 @@ struct BlockDriverState {
     char backing_format[16]; /* if non-zero and backing_file exists */
 
     BlockDriverState *backing_hd;
+    BlockDriverState *overlay;
     BlockDriverState *file;
 
     NotifierList close_notifiers;
-- 
1.8.3.1