Commit 5dae8e5f authored by Stefan Hajnoczi's avatar Stefan Hajnoczi Committed by Kevin Wolf

notify: add NotiferWithReturn so notifier list can abort

notifier_list_notify() has no return value.  This is fine when we just
want to invoke side-effects.

Sometimes it's useful for notifiers to produce a return value.  This
allows notifiers to "veto" an operation and will be used by the block
layer before-write notifier.
Reviewed-by: default avatarEric Blake <>
Reviewed-by: default avatarKevin Wolf <>
Signed-off-by: default avatarStefan Hajnoczi <>
Signed-off-by: default avatarKevin Wolf <>
parent a5c5ea3f
......@@ -40,4 +40,33 @@ void notifier_remove(Notifier *notifier);
void notifier_list_notify(NotifierList *list, void *data);
/* Same as Notifier but allows .notify() to return errors */
typedef struct NotifierWithReturn NotifierWithReturn;
struct NotifierWithReturn {
* Return 0 on success (next notifier will be invoked), otherwise
* notifier_with_return_list_notify() will stop and return the value.
int (*notify)(NotifierWithReturn *notifier, void *data);
QLIST_ENTRY(NotifierWithReturn) node;
typedef struct NotifierWithReturnList {
QLIST_HEAD(, NotifierWithReturn) notifiers;
} NotifierWithReturnList;
{ QLIST_HEAD_INITIALIZER((head).notifiers) }
void notifier_with_return_list_init(NotifierWithReturnList *list);
void notifier_with_return_list_add(NotifierWithReturnList *list,
NotifierWithReturn *notifier);
void notifier_with_return_remove(NotifierWithReturn *notifier);
int notifier_with_return_list_notify(NotifierWithReturnList *list,
void *data);
......@@ -39,3 +39,33 @@ void notifier_list_notify(NotifierList *list, void *data)
notifier->notify(notifier, data);
void notifier_with_return_list_init(NotifierWithReturnList *list)
void notifier_with_return_list_add(NotifierWithReturnList *list,
NotifierWithReturn *notifier)
QLIST_INSERT_HEAD(&list->notifiers, notifier, node);
void notifier_with_return_remove(NotifierWithReturn *notifier)
QLIST_REMOVE(notifier, node);
int notifier_with_return_list_notify(NotifierWithReturnList *list, void *data)
NotifierWithReturn *notifier, *next;
int ret = 0;
QLIST_FOREACH_SAFE(notifier, &list->notifiers, node, next) {
ret = notifier->notify(notifier, data);
if (ret != 0) {
return ret;
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