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 typedef struct BlockDriverAIOCB BlockDriverAIOCB;
  21 typedef void BlockDriverCompletionFunc(void *opaque, int ret);
  22
  23 typedef struct AIOPool {
  24     void (*cancel)(BlockDriverAIOCB *acb);
  25     int aiocb_size;
  26     BlockDriverAIOCB *free_aiocb;
  27 } AIOPool;
  28
  29 struct BlockDriverAIOCB {
  30     AIOPool *pool;
  31     BlockDriverState *bs;
  32     BlockDriverCompletionFunc *cb;
  33     void *opaque;
  34     BlockDriverAIOCB *next;
  35 };
  36
  37 void *qemu_aio_get(AIOPool *pool, BlockDriverState *bs,
  38                    BlockDriverCompletionFunc *cb, void *opaque);
  39 void qemu_aio_release(void *p);
  40
  41 /* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
  42 typedef int (AioFlushHandler)(void *opaque);
  43
  44 /* Runs all currently allowed AIO callbacks of completed requests in the
  45  * respective AIO backend. Returns 0 if no requests was handled, non-zero
  46  * if at least one queued request was handled. */
  47 typedef int (AioProcessQueue)(void *opaque);
  48
  49 /* Flush any pending AIO operation. This function will block until all
  50  * outstanding AIO operations have been completed or cancelled. */
  51 void qemu_aio_flush(void);
  52
  53 /* Wait for a single AIO completion to occur.  This function will wait
  54  * until a single AIO event has completed and it will ensure something
  55  * has moved before returning. This can issue new pending aio as
  56  * result of executing I/O completion or bh callbacks. */
  57 void qemu_aio_wait(void);
  58
  59 /*
  60  * Runs all currently allowed AIO callbacks of completed requests. Returns 0
  61  * if no requests were handled, non-zero if at least one request was
  62  * processed.
  63  */
  64 int qemu_aio_process_queue(void);
  65
  66 /* Register a file descriptor and associated callbacks.  Behaves very similarly
  67  * to qemu_set_fd_handler2.  Unlike qemu_set_fd_handler2, these callbacks will
  68  * be invoked when using either qemu_aio_wait() or qemu_aio_flush().
  69  *
  70  * Code that invokes AIO completion functions should rely on this function
  71  * instead of qemu_set_fd_handler[2].
  72  */
  73 int qemu_aio_set_fd_handler(int fd,
  74                             IOHandler *io_read,
  75                             IOHandler *io_write,
  76                             AioFlushHandler *io_flush,
  77                             AioProcessQueue *io_process_queue,
  78                             void *opaque);
  79
  80 #endif