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-io.h"
20 #include "block/block_int.h"
21 #include "sysemu/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
null_co_parse_filename(const char * filename,QDict * options,Error ** errp)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
null_aio_parse_filename(const char * filename,QDict * options,Error ** errp)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
null_file_open(BlockDriverState * bs,QDict * options,int flags,Error ** errp)80 static int null_file_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
null_co_getlength(BlockDriverState * bs)103 static int64_t coroutine_fn null_co_getlength(BlockDriverState *bs)
104 {
105 BDRVNullState *s = bs->opaque;
106 return s->length;
107 }
108
null_co_common(BlockDriverState * bs)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
null_co_preadv(BlockDriverState * bs,int64_t offset,int64_t bytes,QEMUIOVector * qiov,BdrvRequestFlags flags)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
null_co_pwritev(BlockDriverState * bs,int64_t offset,int64_t bytes,QEMUIOVector * qiov,BdrvRequestFlags flags)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
null_co_flush(BlockDriverState * bs)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
null_bh_cb(void * opaque)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
null_timer_cb(void * opaque)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
null_aio_common(BlockDriverState * bs,BlockCompletionFunc * cb,void * opaque)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
177 acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
178 /* Only emulate latency after vcpu is running. */
179 if (s->latency_ns) {
180 aio_timer_init(bdrv_get_aio_context(bs), &acb->timer,
181 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(bdrv_get_aio_context(bs),
187 null_bh_cb, acb);
188 }
189 return &acb->common;
190 }
191
null_aio_preadv(BlockDriverState * bs,int64_t offset,int64_t bytes,QEMUIOVector * qiov,BdrvRequestFlags flags,BlockCompletionFunc * cb,void * opaque)192 static BlockAIOCB *null_aio_preadv(BlockDriverState *bs,
193 int64_t offset, int64_t bytes,
194 QEMUIOVector *qiov, BdrvRequestFlags flags,
195 BlockCompletionFunc *cb,
196 void *opaque)
197 {
198 BDRVNullState *s = bs->opaque;
199
200 if (s->read_zeroes) {
201 qemu_iovec_memset(qiov, 0, 0, bytes);
202 }
203
204 return null_aio_common(bs, cb, opaque);
205 }
206
null_aio_pwritev(BlockDriverState * bs,int64_t offset,int64_t bytes,QEMUIOVector * qiov,BdrvRequestFlags flags,BlockCompletionFunc * cb,void * opaque)207 static BlockAIOCB *null_aio_pwritev(BlockDriverState *bs,
208 int64_t offset, int64_t bytes,
209 QEMUIOVector *qiov, BdrvRequestFlags flags,
210 BlockCompletionFunc *cb,
211 void *opaque)
212 {
213 return null_aio_common(bs, cb, opaque);
214 }
215
null_aio_flush(BlockDriverState * bs,BlockCompletionFunc * cb,void * opaque)216 static BlockAIOCB *null_aio_flush(BlockDriverState *bs,
217 BlockCompletionFunc *cb,
218 void *opaque)
219 {
220 return null_aio_common(bs, cb, opaque);
221 }
222
null_reopen_prepare(BDRVReopenState * reopen_state,BlockReopenQueue * queue,Error ** errp)223 static int null_reopen_prepare(BDRVReopenState *reopen_state,
224 BlockReopenQueue *queue, Error **errp)
225 {
226 return 0;
227 }
228
null_co_block_status(BlockDriverState * bs,bool want_zero,int64_t offset,int64_t bytes,int64_t * pnum,int64_t * map,BlockDriverState ** file)229 static int coroutine_fn null_co_block_status(BlockDriverState *bs,
230 bool want_zero, int64_t offset,
231 int64_t bytes, int64_t *pnum,
232 int64_t *map,
233 BlockDriverState **file)
234 {
235 BDRVNullState *s = bs->opaque;
236 int ret = BDRV_BLOCK_OFFSET_VALID;
237
238 *pnum = bytes;
239 *map = offset;
240 *file = bs;
241
242 if (s->read_zeroes) {
243 ret |= BDRV_BLOCK_ZERO;
244 }
245 return ret;
246 }
247
null_refresh_filename(BlockDriverState * bs)248 static void null_refresh_filename(BlockDriverState *bs)
249 {
250 const QDictEntry *e;
251
252 for (e = qdict_first(bs->full_open_options); e;
253 e = qdict_next(bs->full_open_options, e))
254 {
255 /* These options can be ignored */
256 if (strcmp(qdict_entry_key(e), "filename") &&
257 strcmp(qdict_entry_key(e), "driver") &&
258 strcmp(qdict_entry_key(e), NULL_OPT_LATENCY))
259 {
260 return;
261 }
262 }
263
264 snprintf(bs->exact_filename, sizeof(bs->exact_filename), "%s://",
265 bs->drv->format_name);
266 }
267
268 static int64_t coroutine_fn
null_co_get_allocated_file_size(BlockDriverState * bs)269 null_co_get_allocated_file_size(BlockDriverState *bs)
270 {
271 return 0;
272 }
273
274 static const char *const null_strong_runtime_opts[] = {
275 BLOCK_OPT_SIZE,
276 NULL_OPT_ZEROES,
277
278 NULL
279 };
280
281 static BlockDriver bdrv_null_co = {
282 .format_name = "null-co",
283 .protocol_name = "null-co",
284 .instance_size = sizeof(BDRVNullState),
285
286 .bdrv_file_open = null_file_open,
287 .bdrv_parse_filename = null_co_parse_filename,
288 .bdrv_co_getlength = null_co_getlength,
289 .bdrv_co_get_allocated_file_size = null_co_get_allocated_file_size,
290
291 .bdrv_co_preadv = null_co_preadv,
292 .bdrv_co_pwritev = null_co_pwritev,
293 .bdrv_co_flush_to_disk = null_co_flush,
294 .bdrv_reopen_prepare = null_reopen_prepare,
295
296 .bdrv_co_block_status = null_co_block_status,
297
298 .bdrv_refresh_filename = null_refresh_filename,
299 .strong_runtime_opts = null_strong_runtime_opts,
300 };
301
302 static BlockDriver bdrv_null_aio = {
303 .format_name = "null-aio",
304 .protocol_name = "null-aio",
305 .instance_size = sizeof(BDRVNullState),
306
307 .bdrv_file_open = null_file_open,
308 .bdrv_parse_filename = null_aio_parse_filename,
309 .bdrv_co_getlength = null_co_getlength,
310 .bdrv_co_get_allocated_file_size = null_co_get_allocated_file_size,
311
312 .bdrv_aio_preadv = null_aio_preadv,
313 .bdrv_aio_pwritev = null_aio_pwritev,
314 .bdrv_aio_flush = null_aio_flush,
315 .bdrv_reopen_prepare = null_reopen_prepare,
316
317 .bdrv_co_block_status = null_co_block_status,
318
319 .bdrv_refresh_filename = null_refresh_filename,
320 .strong_runtime_opts = null_strong_runtime_opts,
321 };
322
bdrv_null_init(void)323 static void bdrv_null_init(void)
324 {
325 bdrv_register(&bdrv_null_co);
326 bdrv_register(&bdrv_null_aio);
327 }
328
329 block_init(bdrv_null_init);
330