[PATCH v5 28/31] block.c: assert BQL lock held in bdrv_co_invalidate_cache

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

bdrv_co_invalidate_cache is special: it is an I/O function,
but uses the block layer permission API, which is GS.

Because of this, we can assert that either the function is
being called with BQL held, and thus can use the permission API,
or make sure that the permission API is not used, by ensuring that
bs (and parents) .open_flags does not contain BDRV_O_INACTIVE.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 block.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/block.c b/block.c
index a0309f827d..805974676b 100644
--- a/block.c
+++ b/block.c
@@ -6574,6 +6574,26 @@ void bdrv_init_with_whitelist(void)
     bdrv_init();
 }
 
+static bool bdrv_is_active(BlockDriverState *bs)
+{
+    BdrvChild *parent;
+
+    if (bs->open_flags & BDRV_O_INACTIVE) {
+        return false;
+    }
+
+    QLIST_FOREACH(parent, &bs->parents, next_parent) {
+        if (parent->klass->parent_is_bds) {
+            BlockDriverState *parent_bs = parent->opaque;
+            if (!bdrv_is_active(parent_bs)) {
+                return false;
+            }
+        }
+    }
+
+   return true;
+}
+
 int coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs, Error **errp)
 {
     BdrvChild *child, *parent;
@@ -6585,6 +6605,12 @@ int coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs, Error **errp)
         return -ENOMEDIUM;
     }
 
+    /*
+     * No need to muck with permissions if bs is active.
+     * TODO: should activation be a separate function?
+     */
+    assert(qemu_in_main_thread() || bdrv_is_active(bs));
+
     QLIST_FOREACH(child, &bs->children, next) {
         bdrv_co_invalidate_cache(child->bs, &local_err);
         if (local_err) {
-- 
2.27.0