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[Qemu-devel] [PATCH v2 10/10] migration: Use JSON null instead of "" to
From: |
Markus Armbruster |
Subject: |
[Qemu-devel] [PATCH v2 10/10] migration: Use JSON null instead of "" to reset parameter to default |
Date: |
Thu, 20 Jul 2017 09:53:41 +0200 |
migrate-set-parameters sets migration parameters according to is
arguments like this:
* Present means "set the parameter to this value"
* Absent means "leave the parameter unchanged"
* Except for parameters tls_creds and tls_hostname, "" means "reset
the parameter to its default value
The first two are perfectly normal: presence of the parameter makes
the command do something.
The third one overloads the parameter with a second meaning. The
overloading is *implicit*, i.e. it's not visible in the types. Works
here, because "" is neither a valid TLS credentials ID, nor a valid
host name.
Pressing argument values the schema accepts, but are semantically
invalid, into service to mean "reset to default" is not general, as
suitable invalid values need not exist. I also find it ugly.
To clean this up, we could add a separate flag argument to ask for
"reset to default", or add a distinct value to @tls_creds and
@tls_hostname. This commit implements the latter: add JSON null to
the values of @tls_creds and @tls_hostname, deprecate "".
Because we're so close to the 2.10 freeze, implement it in the
stupidest way possible: have qmp_migrate_set_parameters() rewrite null
to "" before anything else can see the null. The proper way to do it
would be rewriting "" to null, but that requires fixing up code to
work with null. Add TODO comments for that.
Signed-off-by: Markus Armbruster <address@hidden>
Reviewed-by: Daniel P. Berrange <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
hmp.c | 8 ++++++--
migration/migration.c | 27 +++++++++++++++++++++++----
qapi-schema.json | 20 ++++++++++++++++++--
3 files changed, 47 insertions(+), 8 deletions(-)
diff --git a/hmp.c b/hmp.c
index 4b6b114..fd80dce 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1586,11 +1586,15 @@ void hmp_migrate_set_parameter(Monitor *mon, const
QDict *qdict)
break;
case MIGRATION_PARAMETER_TLS_CREDS:
p->has_tls_creds = true;
- visit_type_str(v, param, &p->tls_creds, &err);
+ p->tls_creds = g_new0(StrOrNull, 1);
+ p->tls_creds->type = QTYPE_QSTRING;
+ visit_type_str(v, param, &p->tls_creds->u.s, &err);
break;
case MIGRATION_PARAMETER_TLS_HOSTNAME:
p->has_tls_hostname = true;
- visit_type_str(v, param, &p->tls_hostname, &err);
+ p->tls_hostname = g_new0(StrOrNull, 1);
+ p->tls_hostname->type = QTYPE_QSTRING;
+ visit_type_str(v, param, &p->tls_hostname->u.s, &err);
break;
case MIGRATION_PARAMETER_MAX_BANDWIDTH:
p->has_max_bandwidth = true;
diff --git a/migration/migration.c b/migration/migration.c
index 205b801..085c32c 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -770,11 +770,13 @@ static void
migrate_params_test_apply(MigrateSetParameters *params,
}
if (params->has_tls_creds) {
- dest->tls_creds = g_strdup(params->tls_creds);
+ assert(params->tls_creds->type == QTYPE_QSTRING);
+ dest->tls_creds = g_strdup(params->tls_creds->u.s);
}
if (params->has_tls_hostname) {
- dest->tls_hostname = g_strdup(params->tls_hostname);
+ assert(params->tls_hostname->type == QTYPE_QSTRING);
+ dest->tls_hostname = g_strdup(params->tls_hostname->u.s);
}
if (params->has_max_bandwidth) {
@@ -822,12 +824,14 @@ static void migrate_params_apply(MigrateSetParameters
*params)
if (params->has_tls_creds) {
g_free(s->parameters.tls_creds);
- s->parameters.tls_creds = g_strdup(params->tls_creds);
+ assert(params->tls_creds->type == QTYPE_QSTRING);
+ s->parameters.tls_creds = g_strdup(params->tls_creds->u.s);
}
if (params->has_tls_hostname) {
g_free(s->parameters.tls_hostname);
- s->parameters.tls_hostname = g_strdup(params->tls_hostname);
+ assert(params->tls_hostname->type == QTYPE_QSTRING);
+ s->parameters.tls_hostname = g_strdup(params->tls_hostname->u.s);
}
if (params->has_max_bandwidth) {
@@ -858,6 +862,21 @@ void qmp_migrate_set_parameters(MigrateSetParameters
*params, Error **errp)
{
MigrationParameters tmp;
+ /* TODO Rewrite "" to null instead */
+ if (params->has_tls_creds
+ && params->tls_creds->type == QTYPE_QNULL) {
+ QDECREF(params->tls_creds->u.n);
+ params->tls_creds->type = QTYPE_QSTRING;
+ params->tls_creds->u.s = strdup("");
+ }
+ /* TODO Rewrite "" to null instead */
+ if (params->has_tls_hostname
+ && params->tls_hostname->type == QTYPE_QNULL) {
+ QDECREF(params->tls_hostname->u.n);
+ params->tls_hostname->type = QTYPE_QSTRING;
+ params->tls_hostname->u.s = strdup("");
+ }
+
migrate_params_test_apply(params, &tmp);
if (!migrate_params_check(&tmp, errp)) {
diff --git a/qapi-schema.json b/qapi-schema.json
index 9ea45d2..df0a568 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -116,6 +116,22 @@
{ 'command': 'qmp_capabilities' }
##
+# @StrOrNull:
+#
+# This is a string value or the explicit lack of a string (null
+# pointer in C). Intended for cases when 'optional absent' already
+# has a different meaning.
+#
+# @s: the string value
+# @n: no string value
+#
+# Since: 2.10
+##
+{ 'alternate': 'StrOrNull',
+ 'data': { 's': 'str',
+ 'n': 'null' } }
+
+##
# @LostTickPolicy:
#
# Policy for handling lost ticks in timer devices.
@@ -1098,8 +1114,8 @@
'*decompress-threads': 'int',
'*cpu-throttle-initial': 'int',
'*cpu-throttle-increment': 'int',
- '*tls-creds': 'str',
- '*tls-hostname': 'str',
+ '*tls-creds': 'StrOrNull',
+ '*tls-hostname': 'StrOrNull',
'*max-bandwidth': 'int',
'*downtime-limit': 'int',
'*x-checkpoint-delay': 'int',
--
2.7.5
- [Qemu-devel] [PATCH v2 00/10] Correct two minor QMP interface design flaws, Markus Armbruster, 2017/07/20
- [Qemu-devel] [PATCH v2 10/10] migration: Use JSON null instead of "" to reset parameter to default,
Markus Armbruster <=
- [Qemu-devel] [PATCH v2 02/10] qapi: Use QNull for a more regular visit_type_null(), Markus Armbruster, 2017/07/20
- [Qemu-devel] [PATCH v2 04/10] tests/test-qobject-input-visitor: Drop redundant test, Markus Armbruster, 2017/07/20
- [Qemu-devel] [PATCH v2 08/10] migration: Add TODO comments on duplication of QAPI_CLONE(), Markus Armbruster, 2017/07/20
- [Qemu-devel] [PATCH v2 06/10] hmp: Clean up and simplify hmp_migrate_set_parameter(), Markus Armbruster, 2017/07/20
- [Qemu-devel] [PATCH v2 01/10] qapi: Separate type QNull from QObject, Markus Armbruster, 2017/07/20
- [Qemu-devel] [PATCH v2 05/10] block: Use JSON null instead of "" to disable backing file, Markus Armbruster, 2017/07/20
- [Qemu-devel] [PATCH v2 03/10] qapi: Introduce a first class 'null' type, Markus Armbruster, 2017/07/20
- [Qemu-devel] [PATCH v2 07/10] migration: Clean up around tls_creds, tls_hostname, Markus Armbruster, 2017/07/20
- [Qemu-devel] [PATCH v2 09/10] migration: Unshare MigrationParameters struct for now, Markus Armbruster, 2017/07/20