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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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 */ 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
