block-coroutine-wrapper: Add no_co_wrapper_bdrv_wrlock functions

Add a new wrapper type for GRAPH_WRLOCK functions that should be called
from coroutine context.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230911094620.45040-7-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

include/block/block-common.h

@@ -66,10 +66,14 @@
  * function. The coroutine yields after scheduling the BH and is reentered when
  * the wrapped function returns.
  *
+ * A no_co_wrapper_bdrv_wrlock function is a no_co_wrapper function that
+ * automatically takes the graph wrlock when calling the wrapped function.
+ *
  * If the first parameter of the function is a BlockDriverState, BdrvChild or
  * BlockBackend pointer, the AioContext lock for it is taken in the wrapper.
  */
 #define no_co_wrapper
+#define no_co_wrapper_bdrv_wrlock
 
 #include "block/blockjob.h"
 

scripts/block-coroutine-wrapper.py

@@ -71,10 +71,13 @@ class FuncDecl:
         self.args = [ParamDecl(arg.strip()) for arg in args.split(',')]
         self.create_only_co = 'mixed' not in variant
         self.graph_rdlock = 'bdrv_rdlock' in variant
+        self.graph_wrlock = 'bdrv_wrlock' in variant
 
         self.wrapper_type = wrapper_type
 
         if wrapper_type == 'co':
+            if self.graph_wrlock:
+                raise ValueError(f"co function can't be wrlock: {self.name}")
             subsystem, subname = self.name.split('_', 1)
             self.target_name = f'{subsystem}_co_{subname}'
         else:
@@ -250,6 +253,12 @@ def gen_no_co_wrapper(func: FuncDecl) -> str:
     name = func.target_name
     struct_name = func.struct_name
 
+    graph_lock=''
+    graph_unlock=''
+    if func.graph_wrlock:
+        graph_lock='    bdrv_graph_wrlock(NULL);'
+        graph_unlock='    bdrv_graph_wrunlock();'
+
     return f"""\
 /*
  * Wrappers for {name}
@@ -266,9 +275,11 @@ static void {name}_bh(void *opaque)
     {struct_name} *s = opaque;
     AioContext *ctx = {func.gen_ctx('s->')};
 
+{graph_lock}
     aio_context_acquire(ctx);
     {func.get_result}{name}({ func.gen_list('s->{name}') });
     aio_context_release(ctx);
+{graph_unlock}
 
     aio_co_wake(s->co);
 }}