[PATCH 07/14] qga: use special feature to mark those that can run when FS are frozen

["Daniel P. Berrangé" <berrange@redhat.com>]

Currently a list of commands which are safe to run when FS are frozen
is hardcoded in the source. Now that the QAPI schema allows custom
special features, a 'fs-frozen' feature can be added to track this
metadata.

This has the benefit that the restrictions on commands permitted when
frozen are now recorded in the QGA generated documentation.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 qga/main.c           | 22 ++--------------------
 qga/qapi-schema.json | 44 +++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 41 insertions(+), 25 deletions(-)

diff --git a/qga/main.c b/qga/main.c
index c7b7b0a9bc..7bf5ec49ba 100644
--- a/qga/main.c
+++ b/qga/main.c
@@ -128,17 +128,6 @@ struct GAState {
 struct GAState *ga_state;
 QmpCommandList ga_commands;
 
-/* commands that are safe to issue while filesystems are frozen */
-static const char *ga_freeze_allowlist[] = {
-    "guest-ping",
-    "guest-info",
-    "guest-sync",
-    "guest-sync-delimited",
-    "guest-fsfreeze-status",
-    "guest-fsfreeze-thaw",
-    NULL
-};
-
 #ifdef _WIN32
 DWORD WINAPI service_ctrl_handler(DWORD ctrl, DWORD type, LPVOID data,
                                   LPVOID ctx);
@@ -421,7 +410,6 @@ static gint ga_strcmp(gconstpointer str1, gconstpointer str2)
 
 static bool ga_command_is_allowed(const QmpCommand *cmd, GAState *state)
 {
-    int i = 0;
     GAConfig *config = state->config;
     const char *name = qmp_command_name(cmd);
     /* Fallback policy is allow everything */
@@ -453,15 +441,9 @@ static bool ga_command_is_allowed(const QmpCommand *cmd, GAState *state)
      * If frozen, this filtering must take priority over
      * absolutely everything
      */
-    if (state->frozen) {
+    if (state->frozen &&
+        !qmp_command_has_feature(cmd, QAPI_FEATURE_FS_FROZEN)) {
         allowed = false;
-
-        while (ga_freeze_allowlist[i] != NULL) {
-            if (strcmp(name, ga_freeze_allowlist[i]) == 0) {
-                allowed = true;
-            }
-            i++;
-        }
     }
 
     return allowed;
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 571be3a914..8b1eff3abc 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -36,7 +36,11 @@
         'guest-sync-delimited' ],
     # Types and commands with undocumented members:
     'documentation-exceptions': [
-        'GuestNVMeSmart' ] } }
+        'GuestNVMeSmart' ],
+    'command-features': [
+        # Commands permitted while FS are frozen
+        'fs-frozen'
+    ] } }
 
 ##
 # @guest-sync-delimited:
@@ -67,11 +71,16 @@
 #
 # Returns: The unique integer id passed in by the client
 #
+# Features:
+#
+# @fs-frozen: permitted to execute when filesystems are frozen
+#
 # Since: 1.1
 ##
 { 'command': 'guest-sync-delimited',
   'data':    { 'id': 'int' },
-  'returns': 'int' }
+  'returns': 'int',
+  'features': [ 'fs-frozen'] }
 
 ##
 # @guest-sync:
@@ -104,20 +113,30 @@
 #
 # Returns: The unique integer id passed in by the client
 #
+# Features:
+#
+# @fs-frozen: permitted to execute when filesystems are frozen
+#
 # Since: 0.15.0
 ##
 { 'command': 'guest-sync',
   'data':    { 'id': 'int' },
-  'returns': 'int' }
+  'returns': 'int',
+  'features': [ 'fs-frozen'] }
 
 ##
 # @guest-ping:
 #
 # Ping the guest agent, a non-error return implies success
 #
+# Features:
+#
+# @fs-frozen: permitted to execute when filesystems are frozen
+#
 # Since: 0.15.0
 ##
-{ 'command': 'guest-ping' }
+{ 'command': 'guest-ping',
+  'features': [ 'fs-frozen'] }
 
 ##
 # @guest-get-time:
@@ -196,10 +215,15 @@
 #
 # Returns: @GuestAgentInfo
 #
+# Features:
+#
+# @fs-frozen: permitted when filesystems are frozen
+#
 # Since: 0.15.0
 ##
 { 'command': 'guest-info',
-  'returns': 'GuestAgentInfo' }
+  'returns': 'GuestAgentInfo',
+  'features': [ 'fs-frozen'] }
 
 ##
 # @guest-shutdown:
@@ -426,10 +450,15 @@
 # Note: This may fail to properly report the current state as a result
 #     of some other guest processes having issued an fs freeze/thaw.
 #
+# Features:
+#
+# @fs-frozen: permitted when filesystems are frozen
+#
 # Since: 0.15.0
 ##
 { 'command': 'guest-fsfreeze-status',
   'returns': 'GuestFsfreezeStatus',
+  'features': [ 'fs-frozen'],
   'if': { 'any': ['CONFIG_WIN32', 'CONFIG_FSFREEZE'] } }
 
 ##
@@ -488,10 +517,15 @@
 #     filesystems were unfrozen before this call, and that the
 #     filesystem state may have changed before issuing this command.
 #
+# Features:
+#
+# @fs-frozen: permitted when filesystems are frozen
+#
 # Since: 0.15.0
 ##
 { 'command': 'guest-fsfreeze-thaw',
   'returns': 'int',
+  'features': [ 'fs-frozen'],
   'if': { 'any': ['CONFIG_WIN32', 'CONFIG_FSFREEZE'] } }
 
 ##
-- 
2.45.1