qemu-aio.h

   1 /*
   2  * QEMU aio implementation
   3  *
   4  * Copyright IBM, Corp. 2008
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #ifndef QEMU_AIO_H
  15 #define QEMU_AIO_H
  16
  17 #include "qemu-common.h"
  18 #include "qemu-char.h"
  19
  20 /* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
  21 typedef int (AioFlushHandler)(void *opaque);
  22
  23 /* Runs all currently allowed AIO callbacks of completed requests in the
  24  * respective AIO backend. Returns 0 if no requests was handled, non-zero
  25  * if at least one queued request was handled. */
  26 typedef int (AioProcessQueue)(void *opaque);
  27
  28 /* Flush any pending AIO operation. This function will block until all
  29  * outstanding AIO operations have been completed or cancelled. */
  30 void qemu_aio_flush(void);
  31
  32 /* Wait for a single AIO completion to occur.  This function will wait
  33  * until a single AIO event has completed and it will ensure something
  34  * has moved before returning. This can issue new pending aio as
  35  * result of executing I/O completion or bh callbacks. */
  36 void qemu_aio_wait(void);
  37
  38 /*
  39  * Runs all currently allowed AIO callbacks of completed requests. Returns 0
  40  * if no requests were handled, non-zero if at least one request was
  41  * processed.
  42  */
  43 int qemu_aio_process_queue(void);
  44
  45 /* Register a file descriptor and associated callbacks.  Behaves very similarly
  46  * to qemu_set_fd_handler2.  Unlike qemu_set_fd_handler2, these callbacks will
  47  * be invoked when using either qemu_aio_wait() or qemu_aio_flush().
  48  *
  49  * Code that invokes AIO completion functions should rely on this function
  50  * instead of qemu_set_fd_handler[2].
  51  */
  52 int qemu_aio_set_fd_handler(int fd,
  53                             IOHandler *io_read,
  54                             IOHandler *io_write,
  55                             AioFlushHandler *io_flush,
  56                             AioProcessQueue *io_process_queue,
  57                             void *opaque);
  58
  59 #endif