| 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 "qobject/qdict.h" |
| 16 | #include "qobject/qstring.h" |
| 17 | #include "qemu/module.h" |
| 18 | #include "qemu/option.h" |
| 19 | #include "block/block-io.h" |
| 20 | #include "block/block_int.h" |
| 21 | #include "system/replay.h" |
| 22 | |
| 23 | #define NULL_OPT_LATENCY "latency-ns" |
| 24 | #define NULL_OPT_ZEROES "read-zeroes" |
| 25 | |
| 26 | typedef struct { |
| 27 | int64_t length; |
| 28 | int64_t latency_ns; |
| 29 | bool read_zeroes; |
| 30 | } BDRVNullState; |
| 31 | |
| 32 | static QemuOptsList runtime_opts = { |
| 33 | .name = "null", |
| 34 | .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head), |
| 35 | .desc = { |
| 36 | { |
| 37 | .name = BLOCK_OPT_SIZE, |
| 38 | .type = QEMU_OPT_SIZE, |
| 39 | .help = "size of the null block", |
| 40 | }, |
| 41 | { |
| 42 | .name = NULL_OPT_LATENCY, |
| 43 | .type = QEMU_OPT_NUMBER, |
| 44 | .help = "nanoseconds (approximated) to wait " |
| 45 | "before completing request", |
| 46 | }, |
| 47 | { |
| 48 | .name = NULL_OPT_ZEROES, |
| 49 | .type = QEMU_OPT_BOOL, |
| 50 | .help = "return zeroes when read", |
| 51 | }, |
| 52 | { /* end of list */ } |
| 53 | }, |
| 54 | }; |
| 55 | |
| 56 | static void null_co_parse_filename(const char *filename, QDict *options, |
| 57 | Error **errp) |
| 58 | { |
| 59 | /* This functions only exists so that a null-co:// filename is accepted |
| 60 | * with the null-co driver. */ |
| 61 | if (strcmp(filename, "null-co://")) { |
| 62 | error_setg(errp, "The only allowed filename for this driver is " |
| 63 | "'null-co://'"); |
| 64 | return; |
| 65 | } |
| 66 | } |
| 67 | |
| 68 | static void null_aio_parse_filename(const char *filename, QDict *options, |
| 69 | Error **errp) |
| 70 | { |
| 71 | /* This functions only exists so that a null-aio:// filename is accepted |
| 72 | * with the null-aio driver. */ |
| 73 | if (strcmp(filename, "null-aio://")) { |
| 74 | error_setg(errp, "The only allowed filename for this driver is " |
| 75 | "'null-aio://'"); |
| 76 | return; |
| 77 | } |
| 78 | } |
| 79 | |
| 80 | static int null_open(BlockDriverState *bs, QDict *options, int flags, |
| 81 | Error **errp) |
| 82 | { |
| 83 | QemuOpts *opts; |
| 84 | BDRVNullState *s = bs->opaque; |
| 85 | int ret = 0; |
| 86 | |
| 87 | opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort); |
| 88 | qemu_opts_absorb_qdict(opts, options, &error_abort); |
| 89 | s->length = |
| 90 | qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30); |
| 91 | s->latency_ns = |
| 92 | qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0); |
| 93 | if (s->latency_ns < 0) { |
| 94 | error_setg(errp, "latency-ns is invalid"); |
| 95 | ret = -EINVAL; |
| 96 | } |
| 97 | s->read_zeroes = qemu_opt_get_bool(opts, NULL_OPT_ZEROES, false); |
| 98 | qemu_opts_del(opts); |
| 99 | bs->supported_write_flags = BDRV_REQ_FUA; |
| 100 | return ret; |
| 101 | } |
| 102 | |
| 103 | static int64_t coroutine_fn null_co_getlength(BlockDriverState *bs) |
| 104 | { |
| 105 | BDRVNullState *s = bs->opaque; |
| 106 | return s->length; |
| 107 | } |
| 108 | |
| 109 | static coroutine_fn int null_co_common(BlockDriverState *bs) |
| 110 | { |
| 111 | BDRVNullState *s = bs->opaque; |
| 112 | |
| 113 | if (s->latency_ns) { |
| 114 | qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, s->latency_ns); |
| 115 | } |
| 116 | return 0; |
| 117 | } |
| 118 | |
| 119 | static coroutine_fn int null_co_preadv(BlockDriverState *bs, |
| 120 | int64_t offset, int64_t bytes, |
| 121 | QEMUIOVector *qiov, |
| 122 | BdrvRequestFlags flags) |
| 123 | { |
| 124 | BDRVNullState *s = bs->opaque; |
| 125 | |
| 126 | if (s->read_zeroes) { |
| 127 | qemu_iovec_memset(qiov, 0, 0, bytes); |
| 128 | } |
| 129 | |
| 130 | return null_co_common(bs); |
| 131 | } |
| 132 | |
| 133 | static coroutine_fn int null_co_pwritev(BlockDriverState *bs, |
| 134 | int64_t offset, int64_t bytes, |
| 135 | QEMUIOVector *qiov, |
| 136 | BdrvRequestFlags flags) |
| 137 | { |
| 138 | return null_co_common(bs); |
| 139 | } |
| 140 | |
| 141 | static coroutine_fn int null_co_flush(BlockDriverState *bs) |
| 142 | { |
| 143 | return null_co_common(bs); |
| 144 | } |
| 145 | |
| 146 | typedef struct { |
| 147 | BlockAIOCB common; |
| 148 | QEMUTimer timer; |
| 149 | } NullAIOCB; |
| 150 | |
| 151 | static const AIOCBInfo null_aiocb_info = { |
| 152 | .aiocb_size = sizeof(NullAIOCB), |
| 153 | }; |
| 154 | |
| 155 | static void null_bh_cb(void *opaque) |
| 156 | { |
| 157 | NullAIOCB *acb = opaque; |
| 158 | acb->common.cb(acb->common.opaque, 0); |
| 159 | qemu_aio_unref(acb); |
| 160 | } |
| 161 | |
| 162 | static void null_timer_cb(void *opaque) |
| 163 | { |
| 164 | NullAIOCB *acb = opaque; |
| 165 | acb->common.cb(acb->common.opaque, 0); |
| 166 | timer_deinit(&acb->timer); |
| 167 | qemu_aio_unref(acb); |
| 168 | } |
| 169 | |
| 170 | static inline BlockAIOCB *null_aio_common(BlockDriverState *bs, |
| 171 | BlockCompletionFunc *cb, |
| 172 | void *opaque) |
| 173 | { |
| 174 | NullAIOCB *acb; |
| 175 | BDRVNullState *s = bs->opaque; |
| 176 | AioContext *ctx = qemu_get_current_aio_context(); |
| 177 | |
| 178 | acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque); |
| 179 | /* Only emulate latency after vcpu is running. */ |
| 180 | if (s->latency_ns) { |
| 181 | aio_timer_init(ctx, &acb->timer, QEMU_CLOCK_REALTIME, SCALE_NS, |
| 182 | null_timer_cb, acb); |
| 183 | timer_mod_ns(&acb->timer, |
| 184 | qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + s->latency_ns); |
| 185 | } else { |
| 186 | replay_bh_schedule_oneshot_event(ctx, null_bh_cb, acb); |
| 187 | } |
| 188 | return &acb->common; |
| 189 | } |
| 190 | |
| 191 | static BlockAIOCB *null_aio_preadv(BlockDriverState *bs, |
| 192 | int64_t offset, int64_t bytes, |
| 193 | QEMUIOVector *qiov, BdrvRequestFlags flags, |
| 194 | BlockCompletionFunc *cb, |
| 195 | void *opaque) |
| 196 | { |
| 197 | BDRVNullState *s = bs->opaque; |
| 198 | |
| 199 | if (s->read_zeroes) { |
| 200 | qemu_iovec_memset(qiov, 0, 0, bytes); |
| 201 | } |
| 202 | |
| 203 | return null_aio_common(bs, cb, opaque); |
| 204 | } |
| 205 | |
| 206 | static BlockAIOCB *null_aio_pwritev(BlockDriverState *bs, |
| 207 | int64_t offset, int64_t bytes, |
| 208 | QEMUIOVector *qiov, BdrvRequestFlags flags, |
| 209 | BlockCompletionFunc *cb, |
| 210 | void *opaque) |
| 211 | { |
| 212 | return null_aio_common(bs, cb, opaque); |
| 213 | } |
| 214 | |
| 215 | static BlockAIOCB *null_aio_flush(BlockDriverState *bs, |
| 216 | BlockCompletionFunc *cb, |
| 217 | void *opaque) |
| 218 | { |
| 219 | return null_aio_common(bs, cb, opaque); |
| 220 | } |
| 221 | |
| 222 | static int null_reopen_prepare(BDRVReopenState *reopen_state, |
| 223 | BlockReopenQueue *queue, Error **errp) |
| 224 | { |
| 225 | return 0; |
| 226 | } |
| 227 | |
| 228 | static int coroutine_fn null_co_block_status(BlockDriverState *bs, |
| 229 | unsigned int mode, |
| 230 | int64_t offset, int64_t bytes, |
| 231 | int64_t *pnum, int64_t *map, |
| 232 | BlockDriverState **file) |
| 233 | { |
| 234 | BDRVNullState *s = bs->opaque; |
| 235 | int ret = BDRV_BLOCK_OFFSET_VALID; |
| 236 | |
| 237 | *pnum = bytes; |
| 238 | *map = offset; |
| 239 | *file = bs; |
| 240 | |
| 241 | if (s->read_zeroes) { |
| 242 | ret |= BDRV_BLOCK_ZERO; |
| 243 | } |
| 244 | return ret; |
| 245 | } |
| 246 | |
| 247 | static void null_refresh_filename(BlockDriverState *bs) |
| 248 | { |
| 249 | const QDictEntry *e; |
| 250 | |
| 251 | for (e = qdict_first(bs->full_open_options); e; |
| 252 | e = qdict_next(bs->full_open_options, e)) |
| 253 | { |
| 254 | /* These options can be ignored */ |
| 255 | if (strcmp(qdict_entry_key(e), "filename") && |
| 256 | strcmp(qdict_entry_key(e), "driver") && |
| 257 | strcmp(qdict_entry_key(e), NULL_OPT_LATENCY)) |
| 258 | { |
| 259 | return; |
| 260 | } |
| 261 | } |
| 262 | |
| 263 | snprintf(bs->exact_filename, sizeof(bs->exact_filename), "%s://", |
| 264 | bs->drv->format_name); |
| 265 | } |
| 266 | |
| 267 | static int64_t coroutine_fn |
| 268 | null_co_get_allocated_file_size(BlockDriverState *bs) |
| 269 | { |
| 270 | return 0; |
| 271 | } |
| 272 | |
| 273 | static const char *const null_strong_runtime_opts[] = { |
| 274 | BLOCK_OPT_SIZE, |
| 275 | NULL_OPT_ZEROES, |
| 276 | |
| 277 | NULL |
| 278 | }; |
| 279 | |
| 280 | static BlockDriver bdrv_null_co = { |
| 281 | .format_name = "null-co", |
| 282 | .protocol_name = "null-co", |
| 283 | .instance_size = sizeof(BDRVNullState), |
| 284 | |
| 285 | .bdrv_open = null_open, |
| 286 | .bdrv_parse_filename = null_co_parse_filename, |
| 287 | .bdrv_co_getlength = null_co_getlength, |
| 288 | .bdrv_co_get_allocated_file_size = null_co_get_allocated_file_size, |
| 289 | |
| 290 | .bdrv_co_preadv = null_co_preadv, |
| 291 | .bdrv_co_pwritev = null_co_pwritev, |
| 292 | .bdrv_co_flush_to_disk = null_co_flush, |
| 293 | .bdrv_reopen_prepare = null_reopen_prepare, |
| 294 | |
| 295 | .bdrv_co_block_status = null_co_block_status, |
| 296 | |
| 297 | .bdrv_refresh_filename = null_refresh_filename, |
| 298 | .strong_runtime_opts = null_strong_runtime_opts, |
| 299 | }; |
| 300 | |
| 301 | static BlockDriver bdrv_null_aio = { |
| 302 | .format_name = "null-aio", |
| 303 | .protocol_name = "null-aio", |
| 304 | .instance_size = sizeof(BDRVNullState), |
| 305 | |
| 306 | .bdrv_open = null_open, |
| 307 | .bdrv_parse_filename = null_aio_parse_filename, |
| 308 | .bdrv_co_getlength = null_co_getlength, |
| 309 | .bdrv_co_get_allocated_file_size = null_co_get_allocated_file_size, |
| 310 | |
| 311 | .bdrv_aio_preadv = null_aio_preadv, |
| 312 | .bdrv_aio_pwritev = null_aio_pwritev, |
| 313 | .bdrv_aio_flush = null_aio_flush, |
| 314 | .bdrv_reopen_prepare = null_reopen_prepare, |
| 315 | |
| 316 | .bdrv_co_block_status = null_co_block_status, |
| 317 | |
| 318 | .bdrv_refresh_filename = null_refresh_filename, |
| 319 | .strong_runtime_opts = null_strong_runtime_opts, |
| 320 | }; |
| 321 | |
| 322 | static void bdrv_null_init(void) |
| 323 | { |
| 324 | bdrv_register(&bdrv_null_co); |
| 325 | bdrv_register(&bdrv_null_aio); |
| 326 | } |
| 327 | |
| 328 | block_init(bdrv_null_init); |