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[RFC,24/41] block: Add BdrvChildRole.stay_at_node

Message ID 1487006583-24350-25-git-send-email-kwolf@redhat.com
State New
Headers show

Commit Message

Kevin Wolf Feb. 13, 2017, 5:22 p.m. UTC 
When the parents' child links are updated in bdrv_append() or
bdrv_replace_in_backing_chain(), this should affect all child links of
BlockBackends or other nodes, but not on child links held for other
purposes (like for setting permissions). This patch allows to control
the behaviour per BdrvChildRole.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c                   | 3 +++
 include/block/block_int.h | 4 ++++
 2 files changed, 7 insertions(+)
diff mbox

Patch

diff --git a/block.c b/block.c
index d743f50..842ac78 100644
--- a/block.c
+++ b/block.c
@@ -2713,6 +2713,9 @@  static void change_parent_backing_link(BlockDriverState *from,
     BdrvChild *c, *next, *to_c;
 
     QLIST_FOREACH_SAFE(c, &from->parents, next_parent, next) {
+        if (c->role->stay_at_node) {
+            continue;
+        }
         if (c->role == &child_backing) {
             /* @from is generally not allowed to be a backing file, except for
              * when @to is the overlay. In that case, @from may not be replaced
diff --git a/include/block/block_int.h b/include/block/block_int.h
index a5557b1..b24fc49 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -427,6 +427,10 @@  typedef struct BdrvAioNotifier {
 } BdrvAioNotifier;
 
 struct BdrvChildRole {
+    /* If true, bdrv_replace_in_backing_chain() doesn't change the node this
+     * BdrvChild points to. */
+    bool stay_at_node;
+
     void (*inherit_options)(int *child_flags, QDict *child_options,
                             int parent_flags, QDict *parent_options);