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([2001:b07:6468:f312:24f5:23b:4085:b879]) by smtp.gmail.com with ESMTPSA id a16sm22438727wrx.8.2020.06.23.09.23.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Jun 2020 09:23:08 -0700 (PDT) Subject: Re: [PATCH] qom: Allow object_property_add_child() to fail To: Eric Auger , eric.auger.pro@gmail.com, qemu-devel@nongnu.org, berrange@redhat.com, ehabkost@redhat.com, armbru@redhat.com References: <20200623155452.30954-1-eric.auger@redhat.com> From: Paolo Bonzini Message-ID: <36a1f20b-339e-68c3-287d-4b2d2ac8b719@redhat.com> Date: Tue, 23 Jun 2020 18:23:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200623155452.30954-1-eric.auger@redhat.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=pbonzini@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/23 01:53:54 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 23/06/20 17:54, Eric Auger wrote: > object_property_add() does not allow object_property_try_add() > to gracefully fail as &error_abort is passed as an error handle. > > However such failure can easily be triggered from the QMP shell when, > for instance, one attempts to create an object with an id that already > exists: > > For instance, call twice: > object-add qom-type=memory-backend-ram id=mem1 props.size=1073741824 > and QEMU aborts. > > This behavior is undesired as a user/management application mistake > in reusing a property ID shouldn't result in loss of the VM and live > data within. > > This patch introduces two new functions, object_property_add_err() and > object_property_add_child_err() whose prototype features an error handle. > object_property_add_child_err() now gets called from user_creatable_add_type. > This solution was chosen instead of changing the prototype of existing > functions because the number of existing callers is huge. > > The error now is returned gracefully to the QMP client. > > (QEMU) object-add qom-type=memory-backend-ram id=mem2 props.size=4294967296 > {"return": {}} > (QEMU) object-add qom-type=memory-backend-ram id=mem2 props.size=4294967296 > {"error": {"class": "GenericError", "desc": "attempt to add duplicate property > 'mem2' to object (type 'container')"}} ... also, please add a testcase for this. Paolo > Signed-off-by: Eric Auger > --- > include/qom/object.h | 24 ++++++++++++++++++++++-- > qom/object.c | 33 ++++++++++++++++++++++++++++----- > qom/object_interfaces.c | 7 +++++-- > 3 files changed, 55 insertions(+), 9 deletions(-) > > diff --git a/include/qom/object.h b/include/qom/object.h > index 94a61ccc3f..29652a1563 100644 > --- a/include/qom/object.h > +++ b/include/qom/object.h > @@ -1039,7 +1039,7 @@ Object *object_ref(Object *obj); > void object_unref(Object *obj); > > /** > - * object_property_add: > + * object_property_add_err: > * @obj: the object to add a property to > * @name: the name of the property. This can contain any character except for > * a forward slash. In general, you should use hyphens '-' instead of > @@ -1056,10 +1056,22 @@ void object_unref(Object *obj); > * meant to allow a property to free its opaque upon object > * destruction. This may be NULL. > * @opaque: an opaque pointer to pass to the callbacks for the property > + * @errp: error handle > * > * Returns: The #ObjectProperty; this can be used to set the @resolve > * callback for child and link properties. > */ > +ObjectProperty *object_property_add_err(Object *obj, const char *name, > + const char *type, > + ObjectPropertyAccessor *get, > + ObjectPropertyAccessor *set, > + ObjectPropertyRelease *release, > + void *opaque, Error **errp); > + > +/** > + * object_property_add: same as object_property_add with > + * errp hardcoded to &error_abort > + */ > ObjectProperty *object_property_add(Object *obj, const char *name, > const char *type, > ObjectPropertyAccessor *get, > @@ -1495,10 +1507,11 @@ Object *object_resolve_path_type(const char *path, const char *typename, > Object *object_resolve_path_component(Object *parent, const char *part); > > /** > - * object_property_add_child: > + * object_property_add_child_err: > * @obj: the object to add a property to > * @name: the name of the property > * @child: the child object > + * @errp: error handle > * > * Child properties form the composition tree. All objects need to be a child > * of another object. Objects can only be a child of one object. > @@ -1512,6 +1525,13 @@ Object *object_resolve_path_component(Object *parent, const char *part); > * > * Returns: The newly added property on success, or %NULL on failure. > */ > +ObjectProperty *object_property_add_child_err(Object *obj, const char *name, > + Object *child, Error **errp); > + > +/** > + * object_property_add_child: same as object_property_add_child_err with > + * errp hardcoded to &error_abort > + */ > ObjectProperty *object_property_add_child(Object *obj, const char *name, > Object *child); > > diff --git a/qom/object.c b/qom/object.c > index 6ece96bc2b..2ec72fae7c 100644 > --- a/qom/object.c > +++ b/qom/object.c > @@ -1182,6 +1182,17 @@ object_property_try_add(Object *obj, const char *name, const char *type, > return prop; > } > > +ObjectProperty * > +object_property_add_err(Object *obj, const char *name, const char *type, > + ObjectPropertyAccessor *get, > + ObjectPropertyAccessor *set, > + ObjectPropertyRelease *release, > + void *opaque, Error **errp) > +{ > + return object_property_try_add(obj, name, type, get, set, release, > + opaque, errp); > +} > + > ObjectProperty * > object_property_add(Object *obj, const char *name, const char *type, > ObjectPropertyAccessor *get, > @@ -1189,7 +1200,7 @@ object_property_add(Object *obj, const char *name, const char *type, > ObjectPropertyRelease *release, > void *opaque) > { > - return object_property_try_add(obj, name, type, get, set, release, > + return object_property_add_err(obj, name, type, get, set, release, > opaque, &error_abort); > } > > @@ -1651,8 +1662,8 @@ static void object_finalize_child_property(Object *obj, const char *name, > } > > ObjectProperty * > -object_property_add_child(Object *obj, const char *name, > - Object *child) > +object_property_add_child_err(Object *obj, const char *name, > + Object *child, Error **errp) > { > g_autofree char *type = NULL; > ObjectProperty *op; > @@ -1661,14 +1672,26 @@ object_property_add_child(Object *obj, const char *name, > > type = g_strdup_printf("child<%s>", object_get_typename(child)); > > - op = object_property_add(obj, name, type, object_get_child_property, NULL, > - object_finalize_child_property, child); > + op = object_property_add_err(obj, name, type, object_get_child_property, > + NULL, object_finalize_child_property, > + child, errp); > + if (!op) { > + goto out; > + } > op->resolve = object_resolve_child_property; > +out: > object_ref(child); > child->parent = obj; > return op; > } > > +ObjectProperty * > +object_property_add_child(Object *obj, const char *name, > + Object *child) > +{ > + return object_property_add_child_err(obj, name, child, &error_abort); > +} > + > void object_property_allow_set_link(const Object *obj, const char *name, > Object *val, Error **errp) > { > diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c > index 7e26f86fa6..c7fabda284 100644 > --- a/qom/object_interfaces.c > +++ b/qom/object_interfaces.c > @@ -82,8 +82,11 @@ Object *user_creatable_add_type(const char *type, const char *id, > } > > if (id != NULL) { > - object_property_add_child(object_get_objects_root(), > - id, obj); > + object_property_add_child_err(object_get_objects_root(), > + id, obj, &local_err); > + if (local_err) { > + goto out; > + } > } > > user_creatable_complete(USER_CREATABLE(obj), &local_err); >