1 /* 2 * Null block driver 3 * 4 * Authors: 5 * Fam Zheng <famz@redhat.com> 6 * 7 * Copyright (C) 2014 Red Hat, Inc. 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 */ 12 13 #include "qemu/osdep.h" 14 #include "qapi/error.h" 15 #include "qapi/qmp/qdict.h" 16 #include "qapi/qmp/qstring.h" 17 #include "qemu/module.h" 18 #include "qemu/option.h" 19 #include "block/block_int.h" 20 #include "sysemu/replay.h" 21 22 #define NULL_OPT_LATENCY "latency-ns" 23 #define NULL_OPT_ZEROES "read-zeroes" 24 25 typedef struct { 26 int64_t length; 27 int64_t latency_ns; 28 bool read_zeroes; 29 } BDRVNullState; 30 31 static QemuOptsList runtime_opts = { 32 .name = "null", 33 .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head), 34 .desc = { 35 { 36 .name = BLOCK_OPT_SIZE, 37 .type = QEMU_OPT_SIZE, 38 .help = "size of the null block", 39 }, 40 { 41 .name = NULL_OPT_LATENCY, 42 .type = QEMU_OPT_NUMBER, 43 .help = "nanoseconds (approximated) to wait " 44 "before completing request", 45 }, 46 { 47 .name = NULL_OPT_ZEROES, 48 .type = QEMU_OPT_BOOL, 49 .help = "return zeroes when read", 50 }, 51 { /* end of list */ } 52 }, 53 }; 54 55 static void null_co_parse_filename(const char *filename, QDict *options, 56 Error **errp) 57 { 58 /* This functions only exists so that a null-co:// filename is accepted 59 * with the null-co driver. */ 60 if (strcmp(filename, "null-co://")) { 61 error_setg(errp, "The only allowed filename for this driver is " 62 "'null-co://'"); 63 return; 64 } 65 } 66 67 static void null_aio_parse_filename(const char *filename, QDict *options, 68 Error **errp) 69 { 70 /* This functions only exists so that a null-aio:// filename is accepted 71 * with the null-aio driver. */ 72 if (strcmp(filename, "null-aio://")) { 73 error_setg(errp, "The only allowed filename for this driver is " 74 "'null-aio://'"); 75 return; 76 } 77 } 78 79 static int null_file_open(BlockDriverState *bs, QDict *options, int flags, 80 Error **errp) 81 { 82 QemuOpts *opts; 83 BDRVNullState *s = bs->opaque; 84 int ret = 0; 85 86 opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort); 87 qemu_opts_absorb_qdict(opts, options, &error_abort); 88 s->length = 89 qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30); 90 s->latency_ns = 91 qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0); 92 if (s->latency_ns < 0) { 93 error_setg(errp, "latency-ns is invalid"); 94 ret = -EINVAL; 95 } 96 s->read_zeroes = qemu_opt_get_bool(opts, NULL_OPT_ZEROES, false); 97 qemu_opts_del(opts); 98 bs->supported_write_flags = BDRV_REQ_FUA; 99 return ret; 100 } 101 102 static int64_t null_getlength(BlockDriverState *bs) 103 { 104 BDRVNullState *s = bs->opaque; 105 return s->length; 106 } 107 108 static coroutine_fn int null_co_common(BlockDriverState *bs) 109 { 110 BDRVNullState *s = bs->opaque; 111 112 if (s->latency_ns) { 113 qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, s->latency_ns); 114 } 115 return 0; 116 } 117 118 static coroutine_fn int null_co_preadv(BlockDriverState *bs, 119 uint64_t offset, uint64_t bytes, 120 QEMUIOVector *qiov, int flags) 121 { 122 BDRVNullState *s = bs->opaque; 123 124 if (s->read_zeroes) { 125 qemu_iovec_memset(qiov, 0, 0, bytes); 126 } 127 128 return null_co_common(bs); 129 } 130 131 static coroutine_fn int null_co_pwritev(BlockDriverState *bs, 132 uint64_t offset, uint64_t bytes, 133 QEMUIOVector *qiov, int flags) 134 { 135 return null_co_common(bs); 136 } 137 138 static coroutine_fn int null_co_flush(BlockDriverState *bs) 139 { 140 return null_co_common(bs); 141 } 142 143 typedef struct { 144 BlockAIOCB common; 145 QEMUTimer timer; 146 } NullAIOCB; 147 148 static const AIOCBInfo null_aiocb_info = { 149 .aiocb_size = sizeof(NullAIOCB), 150 }; 151 152 static void null_bh_cb(void *opaque) 153 { 154 NullAIOCB *acb = opaque; 155 acb->common.cb(acb->common.opaque, 0); 156 qemu_aio_unref(acb); 157 } 158 159 static void null_timer_cb(void *opaque) 160 { 161 NullAIOCB *acb = opaque; 162 acb->common.cb(acb->common.opaque, 0); 163 timer_deinit(&acb->timer); 164 qemu_aio_unref(acb); 165 } 166 167 static inline BlockAIOCB *null_aio_common(BlockDriverState *bs, 168 BlockCompletionFunc *cb, 169 void *opaque) 170 { 171 NullAIOCB *acb; 172 BDRVNullState *s = bs->opaque; 173 174 acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque); 175 /* Only emulate latency after vcpu is running. */ 176 if (s->latency_ns) { 177 aio_timer_init(bdrv_get_aio_context(bs), &acb->timer, 178 QEMU_CLOCK_REALTIME, SCALE_NS, 179 null_timer_cb, acb); 180 timer_mod_ns(&acb->timer, 181 qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + s->latency_ns); 182 } else { 183 replay_bh_schedule_oneshot_event(bdrv_get_aio_context(bs), 184 null_bh_cb, acb); 185 } 186 return &acb->common; 187 } 188 189 static BlockAIOCB *null_aio_preadv(BlockDriverState *bs, 190 uint64_t offset, uint64_t bytes, 191 QEMUIOVector *qiov, int flags, 192 BlockCompletionFunc *cb, 193 void *opaque) 194 { 195 BDRVNullState *s = bs->opaque; 196 197 if (s->read_zeroes) { 198 qemu_iovec_memset(qiov, 0, 0, bytes); 199 } 200 201 return null_aio_common(bs, cb, opaque); 202 } 203 204 static BlockAIOCB *null_aio_pwritev(BlockDriverState *bs, 205 uint64_t offset, uint64_t bytes, 206 QEMUIOVector *qiov, int flags, 207 BlockCompletionFunc *cb, 208 void *opaque) 209 { 210 return null_aio_common(bs, cb, opaque); 211 } 212 213 static BlockAIOCB *null_aio_flush(BlockDriverState *bs, 214 BlockCompletionFunc *cb, 215 void *opaque) 216 { 217 return null_aio_common(bs, cb, opaque); 218 } 219 220 static int null_reopen_prepare(BDRVReopenState *reopen_state, 221 BlockReopenQueue *queue, Error **errp) 222 { 223 return 0; 224 } 225 226 static int coroutine_fn null_co_block_status(BlockDriverState *bs, 227 bool want_zero, int64_t offset, 228 int64_t bytes, int64_t *pnum, 229 int64_t *map, 230 BlockDriverState **file) 231 { 232 BDRVNullState *s = bs->opaque; 233 int ret = BDRV_BLOCK_OFFSET_VALID; 234 235 *pnum = bytes; 236 *map = offset; 237 *file = bs; 238 239 if (s->read_zeroes) { 240 ret |= BDRV_BLOCK_ZERO; 241 } 242 return ret; 243 } 244 245 static void null_refresh_filename(BlockDriverState *bs) 246 { 247 const QDictEntry *e; 248 249 for (e = qdict_first(bs->full_open_options); e; 250 e = qdict_next(bs->full_open_options, e)) 251 { 252 /* These options can be ignored */ 253 if (strcmp(qdict_entry_key(e), "filename") && 254 strcmp(qdict_entry_key(e), "driver") && 255 strcmp(qdict_entry_key(e), NULL_OPT_LATENCY)) 256 { 257 return; 258 } 259 } 260 261 snprintf(bs->exact_filename, sizeof(bs->exact_filename), "%s://", 262 bs->drv->format_name); 263 } 264 265 static int64_t null_allocated_file_size(BlockDriverState *bs) 266 { 267 return 0; 268 } 269 270 static const char *const null_strong_runtime_opts[] = { 271 BLOCK_OPT_SIZE, 272 NULL_OPT_ZEROES, 273 274 NULL 275 }; 276 277 static BlockDriver bdrv_null_co = { 278 .format_name = "null-co", 279 .protocol_name = "null-co", 280 .instance_size = sizeof(BDRVNullState), 281 282 .bdrv_file_open = null_file_open, 283 .bdrv_parse_filename = null_co_parse_filename, 284 .bdrv_getlength = null_getlength, 285 .bdrv_get_allocated_file_size = null_allocated_file_size, 286 287 .bdrv_co_preadv = null_co_preadv, 288 .bdrv_co_pwritev = null_co_pwritev, 289 .bdrv_co_flush_to_disk = null_co_flush, 290 .bdrv_reopen_prepare = null_reopen_prepare, 291 292 .bdrv_co_block_status = null_co_block_status, 293 294 .bdrv_refresh_filename = null_refresh_filename, 295 .strong_runtime_opts = null_strong_runtime_opts, 296 }; 297 298 static BlockDriver bdrv_null_aio = { 299 .format_name = "null-aio", 300 .protocol_name = "null-aio", 301 .instance_size = sizeof(BDRVNullState), 302 303 .bdrv_file_open = null_file_open, 304 .bdrv_parse_filename = null_aio_parse_filename, 305 .bdrv_getlength = null_getlength, 306 .bdrv_get_allocated_file_size = null_allocated_file_size, 307 308 .bdrv_aio_preadv = null_aio_preadv, 309 .bdrv_aio_pwritev = null_aio_pwritev, 310 .bdrv_aio_flush = null_aio_flush, 311 .bdrv_reopen_prepare = null_reopen_prepare, 312 313 .bdrv_co_block_status = null_co_block_status, 314 315 .bdrv_refresh_filename = null_refresh_filename, 316 .strong_runtime_opts = null_strong_runtime_opts, 317 }; 318 319 static void bdrv_null_init(void) 320 { 321 bdrv_register(&bdrv_null_co); 322 bdrv_register(&bdrv_null_aio); 323 } 324 325 block_init(bdrv_null_init); 326