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* QEMU aio implementation
* Copyright IBM, Corp. 2008
* Authors:
* Anthony Liguori <>
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
#ifndef QEMU_AIO_H
#define QEMU_AIO_H
#include "qemu-common.h"
#include "qemu-char.h"
/* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
typedef int (AioFlushHandler)(void *opaque);
/* Runs all currently allowed AIO callbacks of completed requests in the
* respective AIO backend. Returns 0 if no requests was handled, non-zero
* if at least one queued request was handled. */
typedef int (AioProcessQueue)(void *opaque);
/* Flush any pending AIO operation. This function will block until all
* outstanding AIO operations have been completed or cancelled. */
void qemu_aio_flush(void);
/* Wait for a single AIO completion to occur. This function will wait
* until a single AIO event has completed and it will ensure something
* has moved before returning. This can issue new pending aio as
* result of executing I/O completion or bh callbacks. */
void qemu_aio_wait(void);
* Runs all currently allowed AIO callbacks of completed requests. Returns 0
* if no requests were handled, non-zero if at least one request was
* processed.
int qemu_aio_process_queue(void);
/* 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().
* Code that invokes AIO completion functions should rely on this function
* instead of qemu_set_fd_handler[2].
int qemu_aio_set_fd_handler(int fd,
IOHandler *io_read,
IOHandler *io_write,
AioFlushHandler *io_flush,
AioProcessQueue *io_process_queue,
void *opaque);