aio: provide platform-independent API

This adds to aio.c a platform-independent API based on EventNotifiers, that
can be used by both POSIX and Win32.

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Makefile.objs

@@ -46,6 +46,8 @@ block-obj-y += nbd.o block.o blockjob.o aio.o aes.o qemu-config.o
 block-obj-y += qemu-progress.o qemu-sockets.o uri.o notify.o
 block-obj-y += $(coroutine-obj-y) $(qobject-obj-y) $(version-obj-y)
 block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
+block-obj-$(CONFIG_POSIX) += event_notifier-posix.o
+block-obj-$(CONFIG_WIN32) += event_notifier-win32.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
 block-obj-y += block/
 block-obj-y += $(qapi-obj-y) qapi-types.o qapi-visit.o
@@ -94,8 +96,6 @@ common-obj-y += bt-host.o bt-vhci.o
 common-obj-y += dma-helpers.o
 common-obj-y += acl.o
 common-obj-$(CONFIG_POSIX) += compatfd.o
-common-obj-$(CONFIG_POSIX) += event_notifier-posix.o
-common-obj-$(CONFIG_WIN32) += event_notifier-win32.o
 common-obj-y += qemu-timer.o qemu-timer-common.o
 common-obj-y += qtest.o
 common-obj-y += vl.o

aio.c

@@ -95,6 +95,15 @@ void qemu_aio_set_fd_handler(int fd,
     qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);
 }
 
+void qemu_aio_set_event_notifier(EventNotifier *notifier,
+                                 EventNotifierHandler *io_read,
+                                 AioFlushEventNotifierHandler *io_flush)
+{
+    qemu_aio_set_fd_handler(event_notifier_get_fd(notifier),
+                            (IOHandler *)io_read, NULL,
+                            (AioFlushHandler *)io_flush, notifier);
+}
+
 void qemu_aio_flush(void)
 {
     while (qemu_aio_wait());

qemu-aio.h

@@ -16,6 +16,7 @@
 
 #include "qemu-common.h"
 #include "qemu-char.h"
+#include "event_notifier.h"
 
 typedef struct BlockDriverAIOCB BlockDriverAIOCB;
 typedef void BlockDriverCompletionFunc(void *opaque, int ret);
@@ -39,7 +40,7 @@ void *qemu_aio_get(AIOPool *pool, BlockDriverState *bs,
 void qemu_aio_release(void *p);
 
 /* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
-typedef int (AioFlushHandler)(void *opaque);
+typedef int (AioFlushEventNotifierHandler)(EventNotifier *e);
 
 /* Flush any pending AIO operation. This function will block until all
  * outstanding AIO operations have been completed or cancelled. */
@@ -53,6 +54,10 @@ void qemu_aio_flush(void);
  * Return whether there is still any pending AIO operation.  */
 bool qemu_aio_wait(void);
 
+#ifdef CONFIG_POSIX
+/* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
+typedef int (AioFlushHandler)(void *opaque);
+
 /* Register a file descriptor and associated callbacks.  Behaves very similarly
  * to qemu_set_fd_handler2.  Unlike qemu_set_fd_handler2, these callbacks will
  * be invoked when using either qemu_aio_wait() or qemu_aio_flush().
@@ -65,5 +70,17 @@ void qemu_aio_set_fd_handler(int fd,
                              IOHandler *io_write,
                              AioFlushHandler *io_flush,
                              void *opaque);
+#endif
+
+/* Register an event notifier and associated callbacks.  Behaves very similarly
+ * to event_notifier_set_handler.  Unlike event_notifier_set_handler, these callbacks
+ * will be invoked when using either qemu_aio_wait() or qemu_aio_flush().
+ *
+ * Code that invokes AIO completion functions should rely on this function
+ * instead of event_notifier_set_handler.
+ */
+void qemu_aio_set_event_notifier(EventNotifier *notifier,
+                                 EventNotifierHandler *io_read,
+                                 AioFlushEventNotifierHandler *io_flush);
 
 #endif