[PATCH] Make the libaio fsync fallback really work
[fio.git] / engines / skeleton_external.c
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1/*
2 * Skeleton for a sample external io engine
3 *
4 * Should be compiled with:
5 *
6 * gcc -Wall -O2 -g -shared -rdynamic -fPIC -o engine.o engine.c
7 *
8 */
9#include <stdio.h>
10#include <stdlib.h>
11#include <unistd.h>
12#include <errno.h>
13#include <assert.h>
14
15#include "../fio.h"
16#include "../os.h"
17
18/*
19 * The core of the module is identical to the ones included with fio,
20 * read those. You cannot use register_ioengine() and unregister_ioengine()
21 * for external modules, they should be gotten through dlsym()
22 */
23
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24/*
25 * The ->event() hook is called to match an event number with an io_u.
26 * After the core has called ->getevents() and it has returned eg 3,
27 * the ->event() hook must return the 3 events that have completed for
28 * subsequent calls to ->event() with [0-2]. Required.
29 */
30static struct io_u *fio_skeleton_event(struct thread_data *td, int event)
31{
32 return NULL;
33}
34
35/*
36 * The ->getevents() hook is used to reap completion events from an async
37 * io engine. It returns the number of completed events since the last call,
38 * which may then be retrieved by calling the ->event() hook with the event
39 * numbers. Required.
40 */
41static int fio_skeleton_getevents(struct thread_data *td, int min, int max,
42 struct timespec *t)
43{
44 return 0;
45}
46
47/*
48 * The ->cancel() hook attempts to cancel the io_u. Only relevant for
49 * async io engines, and need not be supported.
50 */
51static int fio_skeleton_cancel(struct thread_data *td, struct io_u *io_u)
52{
53 return 0;
54}
55
56/*
57 * The ->queue() hook is responsible for initiating io on the io_u
58 * being passed in. If the io engine is a synchronous one, io may complete
59 * before ->queue() returns. Required.
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60 *
61 * The io engine must transfer in the direction noted by io_u->ddir
62 * to the buffer pointed to by io_u->xfer_buf for as many bytes as
63 * io_u->xfer_buflen. Residual data count may be set in io_u->residual
64 * for a short read/write. Should return 0 for io_u complete, < 0 for
65 * an error, and > 0 for the number of bytes transferred.
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66 */
67static int fio_skeleton_queue(struct thread_data *td, struct io_u *io_u)
68{
69 return 0;
70}
71
72/*
73 * The ->prep() function is called for each io_u prior to being submitted
74 * with ->queue(). This hook allows the io engine to perform any
75 * preperatory actions on the io_u, before being submitted. Not required.
76 */
77static int fio_skeleton_prep(struct thread_data *td, struct io_u *io_u)
78{
79 return 0;
80}
81
82/*
83 * The init function is called once per thread/process, and should set up
84 * any structures that this io engine requires to keep track of io. Not
85 * required.
86 */
87static int fio_skeleton_init(struct thread_data *td)
88{
89 return 0;
90}
91
92/*
93 * This is paired with the ->init() funtion and is called when a thread is
94 * done doing io. Should tear down anything setup by the ->init() function.
95 * Not required.
96 */
97static void fio_skeleton_cleanup(struct thread_data *td)
98{
99}
100
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101/*
102 * Note that the structure is exported, so that fio can get it via
103 * dlsym(..., "ioengine");
104 */
105struct ioengine_ops ioengine = {
106 .name = "engine_name",
107 .version = FIO_IOOPS_VERSION,
108 .init = fio_skeleton_init,
109 .prep = fio_skeleton_prep,
110 .queue = fio_skeleton_queue,
830a78b0 111 .cancel = fio_skeleton_cancel,
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112 .getevents = fio_skeleton_getevents,
113 .event = fio_skeleton_event,
114 .cleanup = fio_skeleton_cleanup,
115};