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