Re: [Qemu-devel] [PATCH 2/2] Add file-posix-dynamic-auto-read-only feature

[Markus Armbruster]

Markus Armbruster <address@hidden> writes:

> Markus Armbruster <address@hidden> writes:
>
>> Markus Armbruster <address@hidden> writes:
>>
>>> Kevin Wolf <address@hidden> writes:
>>>
>>>> auto-read-only=on changed its behaviour in file-posix for the 4.0
>>>> release.
>>>
>>> Commit hash, please.
>>
>> I guess it's commit 23dece19da4 "file-posix: Make auto-read-only
>> dynamic".
>>
>>>>          This change cannot be detected through the usual mechanisms
>>>> like schema introspection. Add a new feature to query-qemu-features to
>>>> allow libvirt to detect the presence of the new behaviour.
>>>>
>>>> Signed-off-by: Kevin Wolf <address@hidden>
> [...]
>> The "posix" in @file-posix-dynamic-auto-read-only feels weird.  To make
>> sense of it, you need to know on what kind of host QEMU runs.  If we
>> ever implement it for Windows hosts, we'd get do add
>> @file-windows-posix-dynamic-auto-read-only.
>>
>> What about instead adding @file-dynamic-auto-read-only with a suitable
>> compile-time conditional?
>>
>> [...]
>
> Incremental patch:

Too fast, use this one.

diff --git a/qapi/misc.json b/qapi/misc.json
index df23c54a65..36b5ceb595 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -3058,7 +3058,7 @@
 # Information about support for QEMU features that isn't available through
 # schema introspection.
 #
-# @file-posix-dynamic-auto-read-only:
+# @file-dynamic-auto-read-only:
 #   true if auto-read-only=on means that the image file is dynamically reopened
 #   read-only or read-write depending on whether any writers are attached to
 #   the node.
@@ -3066,7 +3066,9 @@
 # Since: 4.0
 ##
 { 'struct': 'QemuFeatures',
-  'data': { 'file-posix-dynamic-auto-read-only': 'bool' } }
+  'data': {
+      'file-dynamic-auto-read-only': { 'type': 'bool',
+                                       'if': 'defined(CONFIG_POSIX)' } } }
 
 ##
 # @query-qemu-features:
diff --git a/qmp.c b/qmp.c
index 2a887c1e7d..2f5a7d7a2e 100644
--- a/qmp.c
+++ b/qmp.c
@@ -723,7 +723,9 @@ QemuFeatures *qmp_query_qemu_features(Error **errp)
     QemuFeatures *caps = g_new(QemuFeatures, 1);
 
     *caps = (QemuFeatures) {
-        .file_posix_dynamic_auto_read_only = true,
+#ifdef CONFIG_POSIX
+        .file_dynamic_auto_read_only = true,
+#endif
     };
 
     return caps;
diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py
index 826b8066e1..ad14fadf54 100644
--- a/scripts/qapi/visit.py
+++ b/scripts/qapi/visit.py
@@ -110,14 +110,9 @@ void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s 
*obj, Error **errp)
     }
 ''')
 
-    # 'goto out' produced for base, for each member, and if variants were
-    # present
-    if base or members or variants:
-        ret += mcgen('''
-
-out:
-''')
     ret += mcgen('''
+    goto out;                   /* suppress unused label warning */
+out:
     error_propagate(errp, err);
 }
 ''')