Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2017-03-16' into staging
[qemu.git] / block / stream.c
1 /*
2 * Image streaming
3 *
4 * Copyright IBM, Corp. 2011
5 *
6 * Authors:
7 * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
8 *
9 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
10 * See the COPYING.LIB file in the top-level directory.
11 *
12 */
13
14 #include "qemu/osdep.h"
15 #include "trace.h"
16 #include "block/block_int.h"
17 #include "block/blockjob_int.h"
18 #include "qapi/error.h"
19 #include "qapi/qmp/qerror.h"
20 #include "qemu/ratelimit.h"
21 #include "sysemu/block-backend.h"
22
23 enum {
24 /*
25 * Size of data buffer for populating the image file. This should be large
26 * enough to process multiple clusters in a single call, so that populating
27 * contiguous regions of the image is efficient.
28 */
29 STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
30 };
31
32 #define SLICE_TIME 100000000ULL /* ns */
33
34 typedef struct StreamBlockJob {
35 BlockJob common;
36 RateLimit limit;
37 BlockDriverState *base;
38 BlockdevOnError on_error;
39 char *backing_file_str;
40 int bs_flags;
41 } StreamBlockJob;
42
43 static int coroutine_fn stream_populate(BlockBackend *blk,
44 int64_t sector_num, int nb_sectors,
45 void *buf)
46 {
47 struct iovec iov = {
48 .iov_base = buf,
49 .iov_len = nb_sectors * BDRV_SECTOR_SIZE,
50 };
51 QEMUIOVector qiov;
52
53 qemu_iovec_init_external(&qiov, &iov, 1);
54
55 /* Copy-on-read the unallocated clusters */
56 return blk_co_preadv(blk, sector_num * BDRV_SECTOR_SIZE, qiov.size, &qiov,
57 BDRV_REQ_COPY_ON_READ);
58 }
59
60 typedef struct {
61 int ret;
62 bool reached_end;
63 } StreamCompleteData;
64
65 static void stream_complete(BlockJob *job, void *opaque)
66 {
67 StreamBlockJob *s = container_of(job, StreamBlockJob, common);
68 StreamCompleteData *data = opaque;
69 BlockDriverState *bs = blk_bs(job->blk);
70 BlockDriverState *base = s->base;
71 Error *local_err = NULL;
72
73 if (!block_job_is_cancelled(&s->common) && data->reached_end &&
74 data->ret == 0) {
75 const char *base_id = NULL, *base_fmt = NULL;
76 if (base) {
77 base_id = s->backing_file_str;
78 if (base->drv) {
79 base_fmt = base->drv->format_name;
80 }
81 }
82 data->ret = bdrv_change_backing_file(bs, base_id, base_fmt);
83 bdrv_set_backing_hd(bs, base, &local_err);
84 if (local_err) {
85 error_report_err(local_err);
86 data->ret = -EPERM;
87 goto out;
88 }
89 }
90
91 out:
92 /* Reopen the image back in read-only mode if necessary */
93 if (s->bs_flags != bdrv_get_flags(bs)) {
94 /* Give up write permissions before making it read-only */
95 blk_set_perm(job->blk, 0, BLK_PERM_ALL, &error_abort);
96 bdrv_reopen(bs, s->bs_flags, NULL);
97 }
98
99 g_free(s->backing_file_str);
100 block_job_completed(&s->common, data->ret);
101 g_free(data);
102 }
103
104 static void coroutine_fn stream_run(void *opaque)
105 {
106 StreamBlockJob *s = opaque;
107 StreamCompleteData *data;
108 BlockBackend *blk = s->common.blk;
109 BlockDriverState *bs = blk_bs(blk);
110 BlockDriverState *base = s->base;
111 int64_t sector_num = 0;
112 int64_t end = -1;
113 uint64_t delay_ns = 0;
114 int error = 0;
115 int ret = 0;
116 int n = 0;
117 void *buf;
118
119 if (!bs->backing) {
120 goto out;
121 }
122
123 s->common.len = bdrv_getlength(bs);
124 if (s->common.len < 0) {
125 ret = s->common.len;
126 goto out;
127 }
128
129 end = s->common.len >> BDRV_SECTOR_BITS;
130 buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE);
131
132 /* Turn on copy-on-read for the whole block device so that guest read
133 * requests help us make progress. Only do this when copying the entire
134 * backing chain since the copy-on-read operation does not take base into
135 * account.
136 */
137 if (!base) {
138 bdrv_enable_copy_on_read(bs);
139 }
140
141 for (sector_num = 0; sector_num < end; sector_num += n) {
142 bool copy;
143
144 /* Note that even when no rate limit is applied we need to yield
145 * with no pending I/O here so that bdrv_drain_all() returns.
146 */
147 block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
148 if (block_job_is_cancelled(&s->common)) {
149 break;
150 }
151
152 copy = false;
153
154 ret = bdrv_is_allocated(bs, sector_num,
155 STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
156 if (ret == 1) {
157 /* Allocated in the top, no need to copy. */
158 } else if (ret >= 0) {
159 /* Copy if allocated in the intermediate images. Limit to the
160 * known-unallocated area [sector_num, sector_num+n). */
161 ret = bdrv_is_allocated_above(backing_bs(bs), base,
162 sector_num, n, &n);
163
164 /* Finish early if end of backing file has been reached */
165 if (ret == 0 && n == 0) {
166 n = end - sector_num;
167 }
168
169 copy = (ret == 1);
170 }
171 trace_stream_one_iteration(s, sector_num, n, ret);
172 if (copy) {
173 ret = stream_populate(blk, sector_num, n, buf);
174 }
175 if (ret < 0) {
176 BlockErrorAction action =
177 block_job_error_action(&s->common, s->on_error, true, -ret);
178 if (action == BLOCK_ERROR_ACTION_STOP) {
179 n = 0;
180 continue;
181 }
182 if (error == 0) {
183 error = ret;
184 }
185 if (action == BLOCK_ERROR_ACTION_REPORT) {
186 break;
187 }
188 }
189 ret = 0;
190
191 /* Publish progress */
192 s->common.offset += n * BDRV_SECTOR_SIZE;
193 if (copy && s->common.speed) {
194 delay_ns = ratelimit_calculate_delay(&s->limit, n);
195 }
196 }
197
198 if (!base) {
199 bdrv_disable_copy_on_read(bs);
200 }
201
202 /* Do not remove the backing file if an error was there but ignored. */
203 ret = error;
204
205 qemu_vfree(buf);
206
207 out:
208 /* Modify backing chain and close BDSes in main loop */
209 data = g_malloc(sizeof(*data));
210 data->ret = ret;
211 data->reached_end = sector_num == end;
212 block_job_defer_to_main_loop(&s->common, stream_complete, data);
213 }
214
215 static void stream_set_speed(BlockJob *job, int64_t speed, Error **errp)
216 {
217 StreamBlockJob *s = container_of(job, StreamBlockJob, common);
218
219 if (speed < 0) {
220 error_setg(errp, QERR_INVALID_PARAMETER, "speed");
221 return;
222 }
223 ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
224 }
225
226 static const BlockJobDriver stream_job_driver = {
227 .instance_size = sizeof(StreamBlockJob),
228 .job_type = BLOCK_JOB_TYPE_STREAM,
229 .set_speed = stream_set_speed,
230 .start = stream_run,
231 };
232
233 void stream_start(const char *job_id, BlockDriverState *bs,
234 BlockDriverState *base, const char *backing_file_str,
235 int64_t speed, BlockdevOnError on_error, Error **errp)
236 {
237 StreamBlockJob *s;
238 BlockDriverState *iter;
239 int orig_bs_flags;
240
241 /* Make sure that the image is opened in read-write mode */
242 orig_bs_flags = bdrv_get_flags(bs);
243 if (!(orig_bs_flags & BDRV_O_RDWR)) {
244 if (bdrv_reopen(bs, orig_bs_flags | BDRV_O_RDWR, errp) != 0) {
245 return;
246 }
247 }
248
249 /* Prevent concurrent jobs trying to modify the graph structure here, we
250 * already have our own plans. Also don't allow resize as the image size is
251 * queried only at the job start and then cached. */
252 s = block_job_create(job_id, &stream_job_driver, bs,
253 BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
254 BLK_PERM_GRAPH_MOD,
255 BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
256 BLK_PERM_WRITE,
257 speed, BLOCK_JOB_DEFAULT, NULL, NULL, errp);
258 if (!s) {
259 goto fail;
260 }
261
262 /* Block all intermediate nodes between bs and base, because they will
263 * disappear from the chain after this operation. The streaming job reads
264 * every block only once, assuming that it doesn't change, so block writes
265 * and resizes. */
266 for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) {
267 block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
268 BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED,
269 &error_abort);
270 }
271
272 s->base = base;
273 s->backing_file_str = g_strdup(backing_file_str);
274 s->bs_flags = orig_bs_flags;
275
276 s->on_error = on_error;
277 trace_stream_start(bs, base, s);
278 block_job_start(&s->common);
279 return;
280
281 fail:
282 if (orig_bs_flags != bdrv_get_flags(bs)) {
283 bdrv_reopen(bs, s->bs_flags, NULL);
284 }
285 }