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 "block/block_int.h" 18 19 #define NULL_OPT_LATENCY "latency-ns" 20 #define NULL_OPT_ZEROES "read-zeroes" 21 22 typedef struct { 23 int64_t length; 24 int64_t latency_ns; 25 bool read_zeroes; 26 } BDRVNullState; 27 28 static QemuOptsList runtime_opts = { 29 .name = "null", 30 .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head), 31 .desc = { 32 { 33 .name = BLOCK_OPT_SIZE, 34 .type = QEMU_OPT_SIZE, 35 .help = "size of the null block", 36 }, 37 { 38 .name = NULL_OPT_LATENCY, 39 .type = QEMU_OPT_NUMBER, 40 .help = "nanoseconds (approximated) to wait " 41 "before completing request", 42 }, 43 { 44 .name = NULL_OPT_ZEROES, 45 .type = QEMU_OPT_BOOL, 46 .help = "return zeroes when read", 47 }, 48 { /* end of list */ } 49 }, 50 }; 51 52 static void null_co_parse_filename(const char *filename, QDict *options, 53 Error **errp) 54 { 55 /* This functions only exists so that a null-co:// filename is accepted 56 * with the null-co driver. */ 57 if (strcmp(filename, "null-co://")) { 58 error_setg(errp, "The only allowed filename for this driver is " 59 "'null-co://'"); 60 return; 61 } 62 } 63 64 static void null_aio_parse_filename(const char *filename, QDict *options, 65 Error **errp) 66 { 67 /* This functions only exists so that a null-aio:// filename is accepted 68 * with the null-aio driver. */ 69 if (strcmp(filename, "null-aio://")) { 70 error_setg(errp, "The only allowed filename for this driver is " 71 "'null-aio://'"); 72 return; 73 } 74 } 75 76 static int null_file_open(BlockDriverState *bs, QDict *options, int flags, 77 Error **errp) 78 { 79 QemuOpts *opts; 80 BDRVNullState *s = bs->opaque; 81 int ret = 0; 82 83 opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort); 84 qemu_opts_absorb_qdict(opts, options, &error_abort); 85 s->length = 86 qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30); 87 s->latency_ns = 88 qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0); 89 if (s->latency_ns < 0) { 90 error_setg(errp, "latency-ns is invalid"); 91 ret = -EINVAL; 92 } 93 s->read_zeroes = qemu_opt_get_bool(opts, NULL_OPT_ZEROES, false); 94 qemu_opts_del(opts); 95 return ret; 96 } 97 98 static void null_close(BlockDriverState *bs) 99 { 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 co_aio_sleep_ns(bdrv_get_aio_context(bs), QEMU_CLOCK_REALTIME, 114 s->latency_ns); 115 } 116 return 0; 117 } 118 119 static coroutine_fn int null_co_readv(BlockDriverState *bs, 120 int64_t sector_num, int nb_sectors, 121 QEMUIOVector *qiov) 122 { 123 BDRVNullState *s = bs->opaque; 124 125 if (s->read_zeroes) { 126 qemu_iovec_memset(qiov, 0, 0, nb_sectors * BDRV_SECTOR_SIZE); 127 } 128 129 return null_co_common(bs); 130 } 131 132 static coroutine_fn int null_co_writev(BlockDriverState *bs, 133 int64_t sector_num, int nb_sectors, 134 QEMUIOVector *qiov) 135 { 136 return null_co_common(bs); 137 } 138 139 static coroutine_fn int null_co_flush(BlockDriverState *bs) 140 { 141 return null_co_common(bs); 142 } 143 144 typedef struct { 145 BlockAIOCB common; 146 QEMUTimer timer; 147 } NullAIOCB; 148 149 static const AIOCBInfo null_aiocb_info = { 150 .aiocb_size = sizeof(NullAIOCB), 151 }; 152 153 static void null_bh_cb(void *opaque) 154 { 155 NullAIOCB *acb = opaque; 156 acb->common.cb(acb->common.opaque, 0); 157 qemu_aio_unref(acb); 158 } 159 160 static void null_timer_cb(void *opaque) 161 { 162 NullAIOCB *acb = opaque; 163 acb->common.cb(acb->common.opaque, 0); 164 timer_deinit(&acb->timer); 165 qemu_aio_unref(acb); 166 } 167 168 static inline BlockAIOCB *null_aio_common(BlockDriverState *bs, 169 BlockCompletionFunc *cb, 170 void *opaque) 171 { 172 NullAIOCB *acb; 173 BDRVNullState *s = bs->opaque; 174 175 acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque); 176 /* Only emulate latency after vcpu is running. */ 177 if (s->latency_ns) { 178 aio_timer_init(bdrv_get_aio_context(bs), &acb->timer, 179 QEMU_CLOCK_REALTIME, SCALE_NS, 180 null_timer_cb, acb); 181 timer_mod_ns(&acb->timer, 182 qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + s->latency_ns); 183 } else { 184 aio_bh_schedule_oneshot(bdrv_get_aio_context(bs), null_bh_cb, acb); 185 } 186 return &acb->common; 187 } 188 189 static BlockAIOCB *null_aio_readv(BlockDriverState *bs, 190 int64_t sector_num, QEMUIOVector *qiov, 191 int nb_sectors, 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, nb_sectors * BDRV_SECTOR_SIZE); 199 } 200 201 return null_aio_common(bs, cb, opaque); 202 } 203 204 static BlockAIOCB *null_aio_writev(BlockDriverState *bs, 205 int64_t sector_num, QEMUIOVector *qiov, 206 int nb_sectors, 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 int64_t coroutine_fn null_co_get_block_status(BlockDriverState *bs, 227 int64_t sector_num, 228 int nb_sectors, int *pnum, 229 BlockDriverState **file) 230 { 231 BDRVNullState *s = bs->opaque; 232 off_t start = sector_num * BDRV_SECTOR_SIZE; 233 234 *pnum = nb_sectors; 235 *file = bs; 236 237 if (s->read_zeroes) { 238 return BDRV_BLOCK_OFFSET_VALID | start | BDRV_BLOCK_ZERO; 239 } else { 240 return BDRV_BLOCK_OFFSET_VALID | start; 241 } 242 } 243 244 static void null_refresh_filename(BlockDriverState *bs, QDict *opts) 245 { 246 QINCREF(opts); 247 qdict_del(opts, "filename"); 248 249 if (!qdict_size(opts)) { 250 snprintf(bs->exact_filename, sizeof(bs->exact_filename), "%s://", 251 bs->drv->format_name); 252 } 253 254 qdict_put_str(opts, "driver", bs->drv->format_name); 255 bs->full_open_options = opts; 256 } 257 258 static BlockDriver bdrv_null_co = { 259 .format_name = "null-co", 260 .protocol_name = "null-co", 261 .instance_size = sizeof(BDRVNullState), 262 263 .bdrv_file_open = null_file_open, 264 .bdrv_parse_filename = null_co_parse_filename, 265 .bdrv_close = null_close, 266 .bdrv_getlength = null_getlength, 267 268 .bdrv_co_readv = null_co_readv, 269 .bdrv_co_writev = null_co_writev, 270 .bdrv_co_flush_to_disk = null_co_flush, 271 .bdrv_reopen_prepare = null_reopen_prepare, 272 273 .bdrv_co_get_block_status = null_co_get_block_status, 274 275 .bdrv_refresh_filename = null_refresh_filename, 276 }; 277 278 static BlockDriver bdrv_null_aio = { 279 .format_name = "null-aio", 280 .protocol_name = "null-aio", 281 .instance_size = sizeof(BDRVNullState), 282 283 .bdrv_file_open = null_file_open, 284 .bdrv_parse_filename = null_aio_parse_filename, 285 .bdrv_close = null_close, 286 .bdrv_getlength = null_getlength, 287 288 .bdrv_aio_readv = null_aio_readv, 289 .bdrv_aio_writev = null_aio_writev, 290 .bdrv_aio_flush = null_aio_flush, 291 .bdrv_reopen_prepare = null_reopen_prepare, 292 293 .bdrv_co_get_block_status = null_co_get_block_status, 294 295 .bdrv_refresh_filename = null_refresh_filename, 296 }; 297 298 static void bdrv_null_init(void) 299 { 300 bdrv_register(&bdrv_null_co); 301 bdrv_register(&bdrv_null_aio); 302 } 303 304 block_init(bdrv_null_init); 305