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
17 /*
18 * The core of the module is identical to the ones included with fio,
19 * read those. You cannot use register_ioengine() and unregister_ioengine()
20 * for external modules, they should be gotten through dlsym()
21 */
22
23 /*
24 * The ->event() hook is called to match an event number with an io_u.
25 * After the core has called ->getevents() and it has returned eg 3,
26 * the ->event() hook must return the 3 events that have completed for
27 * subsequent calls to ->event() with [0-2]. Required.
28 */
fio_skeleton_event(struct thread_data * td,int event)29 static struct io_u *fio_skeleton_event(struct thread_data *td, int event)
30 {
31 return NULL;
32 }
33
34 /*
35 * The ->getevents() hook is used to reap completion events from an async
36 * io engine. It returns the number of completed events since the last call,
37 * which may then be retrieved by calling the ->event() hook with the event
38 * numbers. Required.
39 */
fio_skeleton_getevents(struct thread_data * td,unsigned int min,unsigned int max,const struct timespec * t)40 static int fio_skeleton_getevents(struct thread_data *td, unsigned int min,
41 unsigned int max, const struct timespec *t)
42 {
43 return 0;
44 }
45
46 /*
47 * The ->cancel() hook attempts to cancel the io_u. Only relevant for
48 * async io engines, and need not be supported.
49 */
fio_skeleton_cancel(struct thread_data * td,struct io_u * io_u)50 static int fio_skeleton_cancel(struct thread_data *td, struct io_u *io_u)
51 {
52 return 0;
53 }
54
55 /*
56 * The ->queue() hook is responsible for initiating io on the io_u
57 * being passed in. If the io engine is a synchronous one, io may complete
58 * before ->queue() returns. Required.
59 *
60 * The io engine must transfer in the direction noted by io_u->ddir
61 * to the buffer pointed to by io_u->xfer_buf for as many bytes as
62 * io_u->xfer_buflen. Residual data count may be set in io_u->resid
63 * for a short read/write.
64 */
fio_skeleton_queue(struct thread_data * td,struct io_u * io_u)65 static int fio_skeleton_queue(struct thread_data *td, struct io_u *io_u)
66 {
67 /*
68 * Double sanity check to catch errant write on a readonly setup
69 */
70 fio_ro_check(td, io_u);
71
72 /*
73 * Could return FIO_Q_QUEUED for a queued request,
74 * FIO_Q_COMPLETED for a completed request, and FIO_Q_BUSY
75 * if we could queue no more at this point (you'd have to
76 * define ->commit() to handle that.
77 */
78 return FIO_Q_COMPLETED;
79 }
80
81 /*
82 * The ->prep() function is called for each io_u prior to being submitted
83 * with ->queue(). This hook allows the io engine to perform any
84 * preparatory actions on the io_u, before being submitted. Not required.
85 */
fio_skeleton_prep(struct thread_data * td,struct io_u * io_u)86 static int fio_skeleton_prep(struct thread_data *td, struct io_u *io_u)
87 {
88 return 0;
89 }
90
91 /*
92 * The init function is called once per thread/process, and should set up
93 * any structures that this io engine requires to keep track of io. Not
94 * required.
95 */
fio_skeleton_init(struct thread_data * td)96 static int fio_skeleton_init(struct thread_data *td)
97 {
98 return 0;
99 }
100
101 /*
102 * This is paired with the ->init() function and is called when a thread is
103 * done doing io. Should tear down anything setup by the ->init() function.
104 * Not required.
105 */
fio_skeleton_cleanup(struct thread_data * td)106 static void fio_skeleton_cleanup(struct thread_data *td)
107 {
108 }
109
110 /*
111 * Hook for opening the given file. Unless the engine has special
112 * needs, it usually just provides generic_file_open() as the handler.
113 */
fio_skeleton_open(struct thread_data * td,struct fio_file * f)114 static int fio_skeleton_open(struct thread_data *td, struct fio_file *f)
115 {
116 return generic_file_open(td, f);
117 }
118
119 /*
120 * Hook for closing a file. See fio_skeleton_open().
121 */
fio_skeleton_close(struct thread_data * td,struct fio_file * f)122 static int fio_skeleton_close(struct thread_data *td, struct fio_file *f)
123 {
124 generic_file_close(td, f);
125 }
126
127 /*
128 * Note that the structure is exported, so that fio can get it via
129 * dlsym(..., "ioengine");
130 */
131 struct ioengine_ops ioengine = {
132 .name = "engine_name",
133 .version = FIO_IOOPS_VERSION,
134 .init = fio_skeleton_init,
135 .prep = fio_skeleton_prep,
136 .queue = fio_skeleton_queue,
137 .cancel = fio_skeleton_cancel,
138 .getevents = fio_skeleton_getevents,
139 .event = fio_skeleton_event,
140 .cleanup = fio_skeleton_cleanup,
141 .open_file = fio_skeleton_open,
142 .close_file = fio_skeleton_close,
143 };
144