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