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Commit | Line | Data |
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747ff602 JC |
1 | /* |
2 | * Live block commit | |
3 | * | |
4 | * Copyright Red Hat, Inc. 2012 | |
5 | * | |
6 | * Authors: | |
7 | * Jeff Cody <jcody@redhat.com> | |
8 | * Based on stream.c by Stefan Hajnoczi | |
9 | * | |
10 | * This work is licensed under the terms of the GNU LGPL, version 2 or later. | |
11 | * See the COPYING.LIB file in the top-level directory. | |
12 | * | |
13 | */ | |
14 | ||
80c71a24 | 15 | #include "qemu/osdep.h" |
dcbf37ce | 16 | #include "qemu/cutils.h" |
747ff602 | 17 | #include "trace.h" |
737e150e | 18 | #include "block/block_int.h" |
c87621ea | 19 | #include "block/blockjob_int.h" |
da34e65c | 20 | #include "qapi/error.h" |
cc7a8ea7 | 21 | #include "qapi/qmp/qerror.h" |
747ff602 | 22 | #include "qemu/ratelimit.h" |
373340b2 | 23 | #include "sysemu/block-backend.h" |
747ff602 JC |
24 | |
25 | enum { | |
26 | /* | |
27 | * Size of data buffer for populating the image file. This should be large | |
28 | * enough to process multiple clusters in a single call, so that populating | |
29 | * contiguous regions of the image is efficient. | |
30 | */ | |
31 | COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */ | |
32 | }; | |
33 | ||
34 | #define SLICE_TIME 100000000ULL /* ns */ | |
35 | ||
36 | typedef struct CommitBlockJob { | |
37 | BlockJob common; | |
38 | RateLimit limit; | |
8dfba279 | 39 | BlockDriverState *commit_top_bs; |
4653456a KW |
40 | BlockBackend *top; |
41 | BlockBackend *base; | |
92aa5c6d | 42 | BlockdevOnError on_error; |
747ff602 | 43 | int base_flags; |
54e26900 | 44 | char *backing_file_str; |
747ff602 JC |
45 | } CommitBlockJob; |
46 | ||
4653456a | 47 | static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base, |
d8a98584 | 48 | int64_t offset, uint64_t bytes, |
747ff602 JC |
49 | void *buf) |
50 | { | |
51 | int ret = 0; | |
4653456a KW |
52 | QEMUIOVector qiov; |
53 | struct iovec iov = { | |
54 | .iov_base = buf, | |
d8a98584 | 55 | .iov_len = bytes, |
4653456a | 56 | }; |
747ff602 | 57 | |
d8a98584 | 58 | assert(bytes < SIZE_MAX); |
4653456a KW |
59 | qemu_iovec_init_external(&qiov, &iov, 1); |
60 | ||
d8a98584 | 61 | ret = blk_co_preadv(bs, offset, qiov.size, &qiov, 0); |
4653456a | 62 | if (ret < 0) { |
747ff602 JC |
63 | return ret; |
64 | } | |
65 | ||
d8a98584 | 66 | ret = blk_co_pwritev(base, offset, qiov.size, &qiov, 0); |
4653456a | 67 | if (ret < 0) { |
747ff602 JC |
68 | return ret; |
69 | } | |
70 | ||
71 | return 0; | |
72 | } | |
73 | ||
9e85cd5c SH |
74 | typedef struct { |
75 | int ret; | |
76 | } CommitCompleteData; | |
77 | ||
78 | static void commit_complete(BlockJob *job, void *opaque) | |
747ff602 | 79 | { |
9e85cd5c SH |
80 | CommitBlockJob *s = container_of(job, CommitBlockJob, common); |
81 | CommitCompleteData *data = opaque; | |
4653456a KW |
82 | BlockDriverState *top = blk_bs(s->top); |
83 | BlockDriverState *base = blk_bs(s->base); | |
bde70715 | 84 | BlockDriverState *commit_top_bs = s->commit_top_bs; |
9e85cd5c | 85 | int ret = data->ret; |
8dfba279 KW |
86 | bool remove_commit_top_bs = false; |
87 | ||
bde70715 | 88 | /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */ |
19ebd13e | 89 | bdrv_ref(top); |
bde70715 | 90 | bdrv_ref(commit_top_bs); |
19ebd13e | 91 | |
8dfba279 KW |
92 | /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before |
93 | * the normal backing chain can be restored. */ | |
94 | blk_unref(s->base); | |
9e85cd5c SH |
95 | |
96 | if (!block_job_is_cancelled(&s->common) && ret == 0) { | |
97 | /* success */ | |
bde70715 | 98 | ret = bdrv_drop_intermediate(s->commit_top_bs, base, |
8dfba279 | 99 | s->backing_file_str); |
bde70715 | 100 | } else { |
8dfba279 KW |
101 | /* XXX Can (or should) we somehow keep 'consistent read' blocked even |
102 | * after the failed/cancelled commit job is gone? If we already wrote | |
103 | * something to base, the intermediate images aren't valid any more. */ | |
104 | remove_commit_top_bs = true; | |
9e85cd5c SH |
105 | } |
106 | ||
107 | /* restore base open flags here if appropriate (e.g., change the base back | |
108 | * to r/o). These reopens do not need to be atomic, since we won't abort | |
109 | * even on failure here */ | |
110 | if (s->base_flags != bdrv_get_flags(base)) { | |
111 | bdrv_reopen(base, s->base_flags, NULL); | |
112 | } | |
9e85cd5c | 113 | g_free(s->backing_file_str); |
4653456a | 114 | blk_unref(s->top); |
4f78a16f KW |
115 | |
116 | /* If there is more than one reference to the job (e.g. if called from | |
117 | * block_job_finish_sync()), block_job_completed() won't free it and | |
118 | * therefore the blockers on the intermediate nodes remain. This would | |
119 | * cause bdrv_set_backing_hd() to fail. */ | |
120 | block_job_remove_all_bdrv(job); | |
121 | ||
9e85cd5c SH |
122 | block_job_completed(&s->common, ret); |
123 | g_free(data); | |
8dfba279 KW |
124 | |
125 | /* If bdrv_drop_intermediate() didn't already do that, remove the commit | |
126 | * filter driver from the backing chain. Do this as the final step so that | |
127 | * the 'consistent read' permission can be granted. */ | |
128 | if (remove_commit_top_bs) { | |
bde70715 KW |
129 | bdrv_child_try_set_perm(commit_top_bs->backing, 0, BLK_PERM_ALL, |
130 | &error_abort); | |
131 | bdrv_replace_node(commit_top_bs, backing_bs(commit_top_bs), | |
132 | &error_abort); | |
8dfba279 | 133 | } |
19ebd13e | 134 | |
bde70715 | 135 | bdrv_unref(commit_top_bs); |
19ebd13e | 136 | bdrv_unref(top); |
9e85cd5c SH |
137 | } |
138 | ||
139 | static void coroutine_fn commit_run(void *opaque) | |
140 | { | |
141 | CommitBlockJob *s = opaque; | |
142 | CommitCompleteData *data; | |
317a6676 | 143 | int64_t offset; |
f14a39cc | 144 | uint64_t delay_ns = 0; |
747ff602 | 145 | int ret = 0; |
51b0a488 | 146 | int64_t n = 0; /* bytes */ |
9e85cd5c | 147 | void *buf = NULL; |
747ff602 JC |
148 | int bytes_written = 0; |
149 | int64_t base_len; | |
150 | ||
4653456a | 151 | ret = s->common.len = blk_getlength(s->top); |
747ff602 | 152 | |
747ff602 | 153 | if (s->common.len < 0) { |
9e85cd5c | 154 | goto out; |
747ff602 JC |
155 | } |
156 | ||
4653456a | 157 | ret = base_len = blk_getlength(s->base); |
747ff602 | 158 | if (base_len < 0) { |
9e85cd5c | 159 | goto out; |
747ff602 JC |
160 | } |
161 | ||
162 | if (base_len < s->common.len) { | |
3a691c50 | 163 | ret = blk_truncate(s->base, s->common.len, PREALLOC_MODE_OFF, NULL); |
747ff602 | 164 | if (ret) { |
9e85cd5c | 165 | goto out; |
747ff602 JC |
166 | } |
167 | } | |
168 | ||
4653456a | 169 | buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE); |
747ff602 | 170 | |
51b0a488 | 171 | for (offset = 0; offset < s->common.len; offset += n) { |
747ff602 JC |
172 | bool copy; |
173 | ||
747ff602 | 174 | /* Note that even when no rate limit is applied we need to yield |
c57b6656 | 175 | * with no pending I/O here so that bdrv_drain_all() returns. |
747ff602 | 176 | */ |
5bf1d5a7 | 177 | block_job_sleep_ns(&s->common, delay_ns); |
747ff602 JC |
178 | if (block_job_is_cancelled(&s->common)) { |
179 | break; | |
180 | } | |
181 | /* Copy if allocated above the base */ | |
4653456a | 182 | ret = bdrv_is_allocated_above(blk_bs(s->top), blk_bs(s->base), |
51b0a488 | 183 | offset, COMMIT_BUFFER_SIZE, &n); |
747ff602 | 184 | copy = (ret == 1); |
51b0a488 | 185 | trace_commit_one_iteration(s, offset, n, ret); |
747ff602 | 186 | if (copy) { |
51b0a488 EB |
187 | ret = commit_populate(s->top, s->base, offset, n, buf); |
188 | bytes_written += n; | |
747ff602 JC |
189 | } |
190 | if (ret < 0) { | |
1e8fb7f1 KW |
191 | BlockErrorAction action = |
192 | block_job_error_action(&s->common, false, s->on_error, -ret); | |
193 | if (action == BLOCK_ERROR_ACTION_REPORT) { | |
9e85cd5c | 194 | goto out; |
747ff602 JC |
195 | } else { |
196 | n = 0; | |
197 | continue; | |
198 | } | |
199 | } | |
200 | /* Publish progress */ | |
51b0a488 | 201 | s->common.offset += n; |
f14a39cc SS |
202 | |
203 | if (copy && s->common.speed) { | |
51b0a488 | 204 | delay_ns = ratelimit_calculate_delay(&s->limit, n); |
f14a39cc | 205 | } |
747ff602 JC |
206 | } |
207 | ||
208 | ret = 0; | |
209 | ||
9e85cd5c | 210 | out: |
747ff602 JC |
211 | qemu_vfree(buf); |
212 | ||
9e85cd5c SH |
213 | data = g_malloc(sizeof(*data)); |
214 | data->ret = ret; | |
215 | block_job_defer_to_main_loop(&s->common, commit_complete, data); | |
747ff602 JC |
216 | } |
217 | ||
218 | static void commit_set_speed(BlockJob *job, int64_t speed, Error **errp) | |
219 | { | |
220 | CommitBlockJob *s = container_of(job, CommitBlockJob, common); | |
221 | ||
222 | if (speed < 0) { | |
c6bd8c70 | 223 | error_setg(errp, QERR_INVALID_PARAMETER, "speed"); |
747ff602 JC |
224 | return; |
225 | } | |
f3e4ce4a | 226 | ratelimit_set_speed(&s->limit, speed, SLICE_TIME); |
747ff602 JC |
227 | } |
228 | ||
3fc4b10a | 229 | static const BlockJobDriver commit_job_driver = { |
747ff602 | 230 | .instance_size = sizeof(CommitBlockJob), |
79e14bf7 | 231 | .job_type = BLOCK_JOB_TYPE_COMMIT, |
747ff602 | 232 | .set_speed = commit_set_speed, |
a7815a76 | 233 | .start = commit_run, |
747ff602 JC |
234 | }; |
235 | ||
8dfba279 KW |
236 | static int coroutine_fn bdrv_commit_top_preadv(BlockDriverState *bs, |
237 | uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags) | |
238 | { | |
239 | return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags); | |
240 | } | |
241 | ||
dcbf37ce KW |
242 | static void bdrv_commit_top_refresh_filename(BlockDriverState *bs, QDict *opts) |
243 | { | |
244 | bdrv_refresh_filename(bs->backing->bs); | |
245 | pstrcpy(bs->exact_filename, sizeof(bs->exact_filename), | |
246 | bs->backing->bs->filename); | |
247 | } | |
91965658 | 248 | |
8dfba279 KW |
249 | static void bdrv_commit_top_close(BlockDriverState *bs) |
250 | { | |
251 | } | |
252 | ||
253 | static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c, | |
254 | const BdrvChildRole *role, | |
e0995dc3 | 255 | BlockReopenQueue *reopen_queue, |
8dfba279 KW |
256 | uint64_t perm, uint64_t shared, |
257 | uint64_t *nperm, uint64_t *nshared) | |
258 | { | |
259 | *nperm = 0; | |
260 | *nshared = BLK_PERM_ALL; | |
261 | } | |
262 | ||
263 | /* Dummy node that provides consistent read to its users without requiring it | |
264 | * from its backing file and that allows writes on the backing file chain. */ | |
265 | static BlockDriver bdrv_commit_top = { | |
91965658 KW |
266 | .format_name = "commit_top", |
267 | .bdrv_co_preadv = bdrv_commit_top_preadv, | |
f7cc69b3 | 268 | .bdrv_co_get_block_status = bdrv_co_get_block_status_from_backing, |
dcbf37ce | 269 | .bdrv_refresh_filename = bdrv_commit_top_refresh_filename, |
91965658 KW |
270 | .bdrv_close = bdrv_commit_top_close, |
271 | .bdrv_child_perm = bdrv_commit_top_child_perm, | |
8dfba279 KW |
272 | }; |
273 | ||
fd62c609 AG |
274 | void commit_start(const char *job_id, BlockDriverState *bs, |
275 | BlockDriverState *base, BlockDriverState *top, int64_t speed, | |
8254b6d9 | 276 | BlockdevOnError on_error, const char *backing_file_str, |
0db832f4 | 277 | const char *filter_node_name, Error **errp) |
747ff602 JC |
278 | { |
279 | CommitBlockJob *s; | |
280 | BlockReopenQueue *reopen_queue = NULL; | |
747ff602 | 281 | int orig_base_flags; |
3e4c5122 | 282 | BlockDriverState *iter; |
8dfba279 | 283 | BlockDriverState *commit_top_bs = NULL; |
747ff602 | 284 | Error *local_err = NULL; |
d7086422 | 285 | int ret; |
747ff602 | 286 | |
18da7f94 | 287 | assert(top != bs); |
747ff602 JC |
288 | if (top == base) { |
289 | error_setg(errp, "Invalid files for merge: top and base are the same"); | |
290 | return; | |
291 | } | |
292 | ||
c6cc12bf KW |
293 | s = block_job_create(job_id, &commit_job_driver, bs, 0, BLK_PERM_ALL, |
294 | speed, BLOCK_JOB_DEFAULT, NULL, NULL, errp); | |
834fe28d AG |
295 | if (!s) { |
296 | return; | |
297 | } | |
298 | ||
bde70715 KW |
299 | /* convert base to r/w, if necessary */ |
300 | orig_base_flags = bdrv_get_flags(base); | |
3db2bd55 AG |
301 | if (!(orig_base_flags & BDRV_O_RDWR)) { |
302 | reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL, | |
303 | orig_base_flags | BDRV_O_RDWR); | |
304 | } | |
bde70715 | 305 | |
747ff602 | 306 | if (reopen_queue) { |
720150f3 | 307 | bdrv_reopen_multiple(bdrv_get_aio_context(bs), reopen_queue, &local_err); |
747ff602 JC |
308 | if (local_err != NULL) { |
309 | error_propagate(errp, local_err); | |
d7086422 | 310 | goto fail; |
747ff602 JC |
311 | } |
312 | } | |
313 | ||
8dfba279 KW |
314 | /* Insert commit_top block node above top, so we can block consistent read |
315 | * on the backing chain below it */ | |
0db832f4 KW |
316 | commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, filter_node_name, 0, |
317 | errp); | |
8dfba279 KW |
318 | if (commit_top_bs == NULL) { |
319 | goto fail; | |
320 | } | |
d3c8c674 KW |
321 | if (!filter_node_name) { |
322 | commit_top_bs->implicit = true; | |
323 | } | |
0d0676a1 | 324 | commit_top_bs->total_sectors = top->total_sectors; |
02be4aeb | 325 | bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(top)); |
8dfba279 | 326 | |
b69f00dd FZ |
327 | bdrv_set_backing_hd(commit_top_bs, top, &local_err); |
328 | if (local_err) { | |
329 | bdrv_unref(commit_top_bs); | |
330 | commit_top_bs = NULL; | |
331 | error_propagate(errp, local_err); | |
332 | goto fail; | |
333 | } | |
61f09cea | 334 | bdrv_replace_node(top, commit_top_bs, &local_err); |
b69f00dd FZ |
335 | if (local_err) { |
336 | bdrv_unref(commit_top_bs); | |
337 | commit_top_bs = NULL; | |
338 | error_propagate(errp, local_err); | |
339 | goto fail; | |
340 | } | |
8dfba279 KW |
341 | |
342 | s->commit_top_bs = commit_top_bs; | |
343 | bdrv_unref(commit_top_bs); | |
747ff602 | 344 | |
3e4c5122 AG |
345 | /* Block all nodes between top and base, because they will |
346 | * disappear from the chain after this operation. */ | |
347 | assert(bdrv_chain_contains(top, base)); | |
8dfba279 KW |
348 | for (iter = top; iter != base; iter = backing_bs(iter)) { |
349 | /* XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves | |
350 | * at s->base (if writes are blocked for a node, they are also blocked | |
351 | * for its backing file). The other options would be a second filter | |
352 | * driver above s->base. */ | |
353 | ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0, | |
354 | BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE, | |
355 | errp); | |
356 | if (ret < 0) { | |
357 | goto fail; | |
358 | } | |
3e4c5122 | 359 | } |
8dfba279 KW |
360 | |
361 | ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp); | |
362 | if (ret < 0) { | |
363 | goto fail; | |
364 | } | |
365 | ||
8dfba279 KW |
366 | s->base = blk_new(BLK_PERM_CONSISTENT_READ |
367 | | BLK_PERM_WRITE | |
368 | | BLK_PERM_RESIZE, | |
369 | BLK_PERM_CONSISTENT_READ | |
370 | | BLK_PERM_GRAPH_MOD | |
371 | | BLK_PERM_WRITE_UNCHANGED); | |
d7086422 KW |
372 | ret = blk_insert_bs(s->base, base, errp); |
373 | if (ret < 0) { | |
374 | goto fail; | |
375 | } | |
4653456a | 376 | |
8dfba279 | 377 | /* Required permissions are already taken with block_job_add_bdrv() */ |
6d0eb64d | 378 | s->top = blk_new(0, BLK_PERM_ALL); |
b247767a | 379 | ret = blk_insert_bs(s->top, top, errp); |
d7086422 KW |
380 | if (ret < 0) { |
381 | goto fail; | |
382 | } | |
4653456a | 383 | |
bde70715 | 384 | s->base_flags = orig_base_flags; |
54e26900 | 385 | s->backing_file_str = g_strdup(backing_file_str); |
747ff602 | 386 | s->on_error = on_error; |
747ff602 | 387 | |
5ccac6f1 JS |
388 | trace_commit_start(bs, base, top, s); |
389 | block_job_start(&s->common); | |
d7086422 KW |
390 | return; |
391 | ||
392 | fail: | |
393 | if (s->base) { | |
394 | blk_unref(s->base); | |
395 | } | |
396 | if (s->top) { | |
397 | blk_unref(s->top); | |
398 | } | |
8dfba279 | 399 | if (commit_top_bs) { |
bde70715 | 400 | bdrv_replace_node(commit_top_bs, top, &error_abort); |
8dfba279 | 401 | } |
05b0d8e3 | 402 | block_job_early_fail(&s->common); |
747ff602 | 403 | } |
83fd6dd3 KW |
404 | |
405 | ||
d6a644bb | 406 | #define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE) |
83fd6dd3 KW |
407 | |
408 | /* commit COW file into the raw image */ | |
409 | int bdrv_commit(BlockDriverState *bs) | |
410 | { | |
f8e2bd53 | 411 | BlockBackend *src, *backing; |
d3f06759 KW |
412 | BlockDriverState *backing_file_bs = NULL; |
413 | BlockDriverState *commit_top_bs = NULL; | |
83fd6dd3 | 414 | BlockDriver *drv = bs->drv; |
d6a644bb EB |
415 | int64_t offset, length, backing_length; |
416 | int ro, open_flags; | |
417 | int64_t n; | |
83fd6dd3 KW |
418 | int ret = 0; |
419 | uint8_t *buf = NULL; | |
d3f06759 | 420 | Error *local_err = NULL; |
83fd6dd3 KW |
421 | |
422 | if (!drv) | |
423 | return -ENOMEDIUM; | |
424 | ||
425 | if (!bs->backing) { | |
426 | return -ENOTSUP; | |
427 | } | |
428 | ||
429 | if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) || | |
430 | bdrv_op_is_blocked(bs->backing->bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) { | |
431 | return -EBUSY; | |
432 | } | |
433 | ||
434 | ro = bs->backing->bs->read_only; | |
435 | open_flags = bs->backing->bs->open_flags; | |
436 | ||
437 | if (ro) { | |
438 | if (bdrv_reopen(bs->backing->bs, open_flags | BDRV_O_RDWR, NULL)) { | |
439 | return -EACCES; | |
440 | } | |
441 | } | |
442 | ||
d3f06759 KW |
443 | src = blk_new(BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL); |
444 | backing = blk_new(BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL); | |
d7086422 | 445 | |
d3f06759 | 446 | ret = blk_insert_bs(src, bs, &local_err); |
d7086422 | 447 | if (ret < 0) { |
d3f06759 KW |
448 | error_report_err(local_err); |
449 | goto ro_cleanup; | |
450 | } | |
451 | ||
452 | /* Insert commit_top block node above backing, so we can write to it */ | |
453 | backing_file_bs = backing_bs(bs); | |
454 | ||
455 | commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR, | |
456 | &local_err); | |
457 | if (commit_top_bs == NULL) { | |
458 | error_report_err(local_err); | |
d7086422 KW |
459 | goto ro_cleanup; |
460 | } | |
02be4aeb | 461 | bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(backing_file_bs)); |
d7086422 | 462 | |
12fa4af6 KW |
463 | bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort); |
464 | bdrv_set_backing_hd(bs, commit_top_bs, &error_abort); | |
d3f06759 KW |
465 | |
466 | ret = blk_insert_bs(backing, backing_file_bs, &local_err); | |
d7086422 | 467 | if (ret < 0) { |
d3f06759 | 468 | error_report_err(local_err); |
d7086422 KW |
469 | goto ro_cleanup; |
470 | } | |
f8e2bd53 KW |
471 | |
472 | length = blk_getlength(src); | |
83fd6dd3 KW |
473 | if (length < 0) { |
474 | ret = length; | |
475 | goto ro_cleanup; | |
476 | } | |
477 | ||
f8e2bd53 | 478 | backing_length = blk_getlength(backing); |
83fd6dd3 KW |
479 | if (backing_length < 0) { |
480 | ret = backing_length; | |
481 | goto ro_cleanup; | |
482 | } | |
483 | ||
484 | /* If our top snapshot is larger than the backing file image, | |
485 | * grow the backing file image if possible. If not possible, | |
486 | * we must return an error */ | |
487 | if (length > backing_length) { | |
3a691c50 | 488 | ret = blk_truncate(backing, length, PREALLOC_MODE_OFF, &local_err); |
83fd6dd3 | 489 | if (ret < 0) { |
ed3d2ec9 | 490 | error_report_err(local_err); |
83fd6dd3 KW |
491 | goto ro_cleanup; |
492 | } | |
493 | } | |
494 | ||
f8e2bd53 KW |
495 | /* blk_try_blockalign() for src will choose an alignment that works for |
496 | * backing as well, so no need to compare the alignment manually. */ | |
d6a644bb | 497 | buf = blk_try_blockalign(src, COMMIT_BUF_SIZE); |
83fd6dd3 KW |
498 | if (buf == NULL) { |
499 | ret = -ENOMEM; | |
500 | goto ro_cleanup; | |
501 | } | |
502 | ||
d6a644bb EB |
503 | for (offset = 0; offset < length; offset += n) { |
504 | ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n); | |
83fd6dd3 KW |
505 | if (ret < 0) { |
506 | goto ro_cleanup; | |
507 | } | |
508 | if (ret) { | |
d6a644bb | 509 | ret = blk_pread(src, offset, buf, n); |
83fd6dd3 KW |
510 | if (ret < 0) { |
511 | goto ro_cleanup; | |
512 | } | |
513 | ||
d6a644bb | 514 | ret = blk_pwrite(backing, offset, buf, n, 0); |
83fd6dd3 KW |
515 | if (ret < 0) { |
516 | goto ro_cleanup; | |
517 | } | |
518 | } | |
519 | } | |
520 | ||
521 | if (drv->bdrv_make_empty) { | |
522 | ret = drv->bdrv_make_empty(bs); | |
523 | if (ret < 0) { | |
524 | goto ro_cleanup; | |
525 | } | |
f8e2bd53 | 526 | blk_flush(src); |
83fd6dd3 KW |
527 | } |
528 | ||
529 | /* | |
530 | * Make sure all data we wrote to the backing device is actually | |
531 | * stable on disk. | |
532 | */ | |
f8e2bd53 | 533 | blk_flush(backing); |
83fd6dd3 KW |
534 | |
535 | ret = 0; | |
536 | ro_cleanup: | |
537 | qemu_vfree(buf); | |
538 | ||
f8e2bd53 | 539 | blk_unref(backing); |
d3f06759 | 540 | if (backing_file_bs) { |
12fa4af6 | 541 | bdrv_set_backing_hd(bs, backing_file_bs, &error_abort); |
d3f06759 KW |
542 | } |
543 | bdrv_unref(commit_top_bs); | |
544 | blk_unref(src); | |
f8e2bd53 | 545 | |
83fd6dd3 KW |
546 | if (ro) { |
547 | /* ignoring error return here */ | |
548 | bdrv_reopen(bs->backing->bs, open_flags & ~BDRV_O_RDWR, NULL); | |
549 | } | |
550 | ||
551 | return ret; | |
552 | } |