ui/common: Don't talloc_free sysinfo and status explicitly

Currently, we talloc_free() the sysinfo and status messages in the
discover client, right after performing the ui's callback.

However, the client may wish to keep a reference to this information
beyond the callback invocation. This change introduces a per-message
talloc context, which these structures are allocated under. This allows
the callbacks to talloc_steal() anything they wish to keep a reference
to.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

diff --git a/ui/common/discover-client.c b/ui/common/discover-client.c
index de210bd785bd940af1a27eac7784dc6c87133529..b48d541050613af3b865c60fe4f684e0a2145852 100644 (file)
--- a/ui/common/discover-client.c
+++ b/ui/common/discover-client.c
@@ -115,7 +115,6 @@ static void update_status(struct discover_client *client,
 {
        if (client->ops.update_status)
                client->ops.update_status(status, client->ops.cb_arg);
-       talloc_free(status);
 }
 
 static void update_sysinfo(struct discover_client *client,
@@ -123,7 +122,6 @@ static void update_sysinfo(struct discover_client *client,
 {
        if (client->ops.update_sysinfo)
                client->ops.update_sysinfo(sysinfo, client->ops.cb_arg);
-       talloc_free(sysinfo);
 }
 
 static void update_config(struct discover_client *client,
@@ -143,16 +141,21 @@ static int discover_client_process(void *arg)
        struct config *config;
        struct device *dev;
        char *dev_id;
+       void *ctx;
        int rc;
 
-       message = pb_protocol_read_message(client, client->fd);
+       /* We use a temporary context for processing one message; persistent
+        * data is re-parented to the client in the callbacks. */
+       ctx = talloc_new(client);
+
+       message = pb_protocol_read_message(ctx, client->fd);
 
        if (!message)
                return -1;
 
        switch (message->action) {
        case PB_PROTOCOL_ACTION_DEVICE_ADD:
-               dev = talloc_zero(client, struct device);
+               dev = talloc_zero(ctx, struct device);
                list_init(&dev->boot_options);
 
                rc = pb_protocol_deserialise_device(dev, message);
@@ -164,7 +167,7 @@ static int discover_client_process(void *arg)
                device_add(client, dev);
                break;
        case PB_PROTOCOL_ACTION_BOOT_OPTION_ADD:
-               opt = talloc_zero(client, struct boot_option);
+               opt = talloc_zero(ctx, struct boot_option);
 
                rc = pb_protocol_deserialise_boot_option(opt, message);
                if (rc) {
@@ -175,7 +178,7 @@ static int discover_client_process(void *arg)
                boot_option_add(client, opt);
                break;
        case PB_PROTOCOL_ACTION_DEVICE_REMOVE:
-               dev_id = pb_protocol_deserialise_string(client, message);
+               dev_id = pb_protocol_deserialise_string(ctx, message);
                if (!dev_id) {
                        pb_log("%s: no device id?\n", __func__);
                        return 0;
@@ -183,7 +186,7 @@ static int discover_client_process(void *arg)
                device_remove(client, dev_id);
                break;
        case PB_PROTOCOL_ACTION_STATUS:
-               status = talloc_zero(client, struct boot_status);
+               status = talloc_zero(ctx, struct boot_status);
 
                rc = pb_protocol_deserialise_boot_status(status, message);
                if (rc) {
@@ -193,7 +196,7 @@ static int discover_client_process(void *arg)
                update_status(client, status);
                break;
        case PB_PROTOCOL_ACTION_SYSTEM_INFO:
-               sysinfo = talloc_zero(client, struct system_info);
+               sysinfo = talloc_zero(ctx, struct system_info);
 
                rc = pb_protocol_deserialise_system_info(sysinfo, message);
                if (rc) {
@@ -216,6 +219,7 @@ static int discover_client_process(void *arg)
                pb_log("%s: unknown action %d\n", __func__, message->action);
        }
 
+       talloc_free(ctx);
 
        return 0;
 }

diff --git a/ui/common/discover-client.h b/ui/common/discover-client.h
index 6aa0432d7a67b2d4fc3774901283b5d852c51881..fa97fa52b782a2c95f37c2c27763d38a098e9fe3 100644 (file)
--- a/ui/common/discover-client.h
+++ b/ui/common/discover-client.h
@@ -18,6 +18,15 @@ struct pb_boot_data {
  * @device_add: PB_PROTOCOL_ACTION_ADD event callback.
  * @device_remove: PB_PROTOCOL_ACTION_REMOVE event callback.
  * @cb_arg: Client managed convenience variable passed to callbacks.
+ *
+ * The discover client holds talloc references to the devices (and the
+ * devices' boot options), so callbacks may store boot options and devices
+ * as long as the client remains allocated.
+ *
+ * The boot_status and system_info structs are allocated by the client,
+ * and will be free()ed after the callback is invoked. If the callback
+ * stores these structures for usage beyond the duration of the callback,
+ * it must talloc_steal() them.
  */
 
 struct discover_client_ops {