Merge remote-tracking branch 'remotes/edgar/tags/edgar/cris-next-2021-02-22.for-upstr...
[qemu.git] / block / commit.c
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
15 #include "qemu/osdep.h"
16 #include "qemu/cutils.h"
17 #include "trace.h"
18 #include "block/block_int.h"
19 #include "block/blockjob_int.h"
20 #include "qapi/error.h"
21 #include "qapi/qmp/qerror.h"
22 #include "qemu/ratelimit.h"
23 #include "sysemu/block-backend.h"
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 typedef struct CommitBlockJob {
35 BlockJob common;
36 BlockDriverState *commit_top_bs;
37 BlockBackend *top;
38 BlockBackend *base;
39 BlockDriverState *base_bs;
40 BlockDriverState *base_overlay;
41 BlockdevOnError on_error;
42 bool base_read_only;
43 bool chain_frozen;
44 char *backing_file_str;
45 } CommitBlockJob;
46
47 static int commit_prepare(Job *job)
48 {
49 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
50
51 bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
52 s->chain_frozen = false;
53
54 /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before
55 * the normal backing chain can be restored. */
56 blk_unref(s->base);
57 s->base = NULL;
58
59 /* FIXME: bdrv_drop_intermediate treats total failures and partial failures
60 * identically. Further work is needed to disambiguate these cases. */
61 return bdrv_drop_intermediate(s->commit_top_bs, s->base_bs,
62 s->backing_file_str);
63 }
64
65 static void commit_abort(Job *job)
66 {
67 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
68 BlockDriverState *top_bs = blk_bs(s->top);
69
70 if (s->chain_frozen) {
71 bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
72 }
73
74 /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */
75 bdrv_ref(top_bs);
76 bdrv_ref(s->commit_top_bs);
77
78 if (s->base) {
79 blk_unref(s->base);
80 }
81
82 /* free the blockers on the intermediate nodes so that bdrv_replace_nodes
83 * can succeed */
84 block_job_remove_all_bdrv(&s->common);
85
86 /* If bdrv_drop_intermediate() failed (or was not invoked), remove the
87 * commit filter driver from the backing chain now. Do this as the final
88 * step so that the 'consistent read' permission can be granted.
89 *
90 * XXX Can (or should) we somehow keep 'consistent read' blocked even
91 * after the failed/cancelled commit job is gone? If we already wrote
92 * something to base, the intermediate images aren't valid any more. */
93 bdrv_replace_node(s->commit_top_bs, s->commit_top_bs->backing->bs,
94 &error_abort);
95
96 bdrv_unref(s->commit_top_bs);
97 bdrv_unref(top_bs);
98 }
99
100 static void commit_clean(Job *job)
101 {
102 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
103
104 /* restore base open flags here if appropriate (e.g., change the base back
105 * to r/o). These reopens do not need to be atomic, since we won't abort
106 * even on failure here */
107 if (s->base_read_only) {
108 bdrv_reopen_set_read_only(s->base_bs, true, NULL);
109 }
110
111 g_free(s->backing_file_str);
112 blk_unref(s->top);
113 }
114
115 static int coroutine_fn commit_run(Job *job, Error **errp)
116 {
117 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
118 int64_t offset;
119 uint64_t delay_ns = 0;
120 int ret = 0;
121 int64_t n = 0; /* bytes */
122 void *buf = NULL;
123 int64_t len, base_len;
124
125 ret = len = blk_getlength(s->top);
126 if (len < 0) {
127 goto out;
128 }
129 job_progress_set_remaining(&s->common.job, len);
130
131 ret = base_len = blk_getlength(s->base);
132 if (base_len < 0) {
133 goto out;
134 }
135
136 if (base_len < len) {
137 ret = blk_truncate(s->base, len, false, PREALLOC_MODE_OFF, 0, NULL);
138 if (ret) {
139 goto out;
140 }
141 }
142
143 buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
144
145 for (offset = 0; offset < len; offset += n) {
146 bool copy;
147 bool error_in_source = true;
148
149 /* Note that even when no rate limit is applied we need to yield
150 * with no pending I/O here so that bdrv_drain_all() returns.
151 */
152 job_sleep_ns(&s->common.job, delay_ns);
153 if (job_is_cancelled(&s->common.job)) {
154 break;
155 }
156 /* Copy if allocated above the base */
157 ret = bdrv_is_allocated_above(blk_bs(s->top), s->base_overlay, true,
158 offset, COMMIT_BUFFER_SIZE, &n);
159 copy = (ret > 0);
160 trace_commit_one_iteration(s, offset, n, ret);
161 if (copy) {
162 assert(n < SIZE_MAX);
163
164 ret = blk_co_pread(s->top, offset, n, buf, 0);
165 if (ret >= 0) {
166 ret = blk_co_pwrite(s->base, offset, n, buf, 0);
167 if (ret < 0) {
168 error_in_source = false;
169 }
170 }
171 }
172 if (ret < 0) {
173 BlockErrorAction action =
174 block_job_error_action(&s->common, s->on_error,
175 error_in_source, -ret);
176 if (action == BLOCK_ERROR_ACTION_REPORT) {
177 goto out;
178 } else {
179 n = 0;
180 continue;
181 }
182 }
183 /* Publish progress */
184 job_progress_update(&s->common.job, n);
185
186 if (copy) {
187 delay_ns = block_job_ratelimit_get_delay(&s->common, n);
188 } else {
189 delay_ns = 0;
190 }
191 }
192
193 ret = 0;
194
195 out:
196 qemu_vfree(buf);
197
198 return ret;
199 }
200
201 static const BlockJobDriver commit_job_driver = {
202 .job_driver = {
203 .instance_size = sizeof(CommitBlockJob),
204 .job_type = JOB_TYPE_COMMIT,
205 .free = block_job_free,
206 .user_resume = block_job_user_resume,
207 .run = commit_run,
208 .prepare = commit_prepare,
209 .abort = commit_abort,
210 .clean = commit_clean
211 },
212 };
213
214 static int coroutine_fn bdrv_commit_top_preadv(BlockDriverState *bs,
215 uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
216 {
217 return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
218 }
219
220 static void bdrv_commit_top_refresh_filename(BlockDriverState *bs)
221 {
222 pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
223 bs->backing->bs->filename);
224 }
225
226 static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c,
227 BdrvChildRole role,
228 BlockReopenQueue *reopen_queue,
229 uint64_t perm, uint64_t shared,
230 uint64_t *nperm, uint64_t *nshared)
231 {
232 *nperm = 0;
233 *nshared = BLK_PERM_ALL;
234 }
235
236 /* Dummy node that provides consistent read to its users without requiring it
237 * from its backing file and that allows writes on the backing file chain. */
238 static BlockDriver bdrv_commit_top = {
239 .format_name = "commit_top",
240 .bdrv_co_preadv = bdrv_commit_top_preadv,
241 .bdrv_refresh_filename = bdrv_commit_top_refresh_filename,
242 .bdrv_child_perm = bdrv_commit_top_child_perm,
243
244 .is_filter = true,
245 };
246
247 void commit_start(const char *job_id, BlockDriverState *bs,
248 BlockDriverState *base, BlockDriverState *top,
249 int creation_flags, int64_t speed,
250 BlockdevOnError on_error, const char *backing_file_str,
251 const char *filter_node_name, Error **errp)
252 {
253 CommitBlockJob *s;
254 BlockDriverState *iter;
255 BlockDriverState *commit_top_bs = NULL;
256 BlockDriverState *filtered_base;
257 int64_t base_size, top_size;
258 uint64_t base_perms, iter_shared_perms;
259 int ret;
260
261 assert(top != bs);
262 if (bdrv_skip_filters(top) == bdrv_skip_filters(base)) {
263 error_setg(errp, "Invalid files for merge: top and base are the same");
264 return;
265 }
266
267 base_size = bdrv_getlength(base);
268 if (base_size < 0) {
269 error_setg_errno(errp, -base_size, "Could not inquire base image size");
270 return;
271 }
272
273 top_size = bdrv_getlength(top);
274 if (top_size < 0) {
275 error_setg_errno(errp, -top_size, "Could not inquire top image size");
276 return;
277 }
278
279 base_perms = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE;
280 if (base_size < top_size) {
281 base_perms |= BLK_PERM_RESIZE;
282 }
283
284 s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL,
285 speed, creation_flags, NULL, NULL, errp);
286 if (!s) {
287 return;
288 }
289
290 /* convert base to r/w, if necessary */
291 s->base_read_only = bdrv_is_read_only(base);
292 if (s->base_read_only) {
293 if (bdrv_reopen_set_read_only(base, false, errp) != 0) {
294 goto fail;
295 }
296 }
297
298 /* Insert commit_top block node above top, so we can block consistent read
299 * on the backing chain below it */
300 commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, filter_node_name, 0,
301 errp);
302 if (commit_top_bs == NULL) {
303 goto fail;
304 }
305 if (!filter_node_name) {
306 commit_top_bs->implicit = true;
307 }
308
309 /* So that we can always drop this node */
310 commit_top_bs->never_freeze = true;
311
312 commit_top_bs->total_sectors = top->total_sectors;
313
314 ret = bdrv_append(commit_top_bs, top, errp);
315 if (ret < 0) {
316 commit_top_bs = NULL;
317 goto fail;
318 }
319
320 s->commit_top_bs = commit_top_bs;
321
322 /*
323 * Block all nodes between top and base, because they will
324 * disappear from the chain after this operation.
325 * Note that this assumes that the user is fine with removing all
326 * nodes (including R/W filters) between top and base. Assuring
327 * this is the responsibility of the interface (i.e. whoever calls
328 * commit_start()).
329 */
330 s->base_overlay = bdrv_find_overlay(top, base);
331 assert(s->base_overlay);
332
333 /*
334 * The topmost node with
335 * bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base)
336 */
337 filtered_base = bdrv_cow_bs(s->base_overlay);
338 assert(bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base));
339
340 /*
341 * XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves
342 * at s->base (if writes are blocked for a node, they are also blocked
343 * for its backing file). The other options would be a second filter
344 * driver above s->base.
345 */
346 iter_shared_perms = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE;
347
348 for (iter = top; iter != base; iter = bdrv_filter_or_cow_bs(iter)) {
349 if (iter == filtered_base) {
350 /*
351 * From here on, all nodes are filters on the base. This
352 * allows us to share BLK_PERM_CONSISTENT_READ.
353 */
354 iter_shared_perms |= BLK_PERM_CONSISTENT_READ;
355 }
356
357 ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
358 iter_shared_perms, errp);
359 if (ret < 0) {
360 goto fail;
361 }
362 }
363
364 if (bdrv_freeze_backing_chain(commit_top_bs, base, errp) < 0) {
365 goto fail;
366 }
367 s->chain_frozen = true;
368
369 ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp);
370 if (ret < 0) {
371 goto fail;
372 }
373
374 s->base = blk_new(s->common.job.aio_context,
375 base_perms,
376 BLK_PERM_CONSISTENT_READ
377 | BLK_PERM_GRAPH_MOD
378 | BLK_PERM_WRITE_UNCHANGED);
379 ret = blk_insert_bs(s->base, base, errp);
380 if (ret < 0) {
381 goto fail;
382 }
383 blk_set_disable_request_queuing(s->base, true);
384 s->base_bs = base;
385
386 /* Required permissions are already taken with block_job_add_bdrv() */
387 s->top = blk_new(s->common.job.aio_context, 0, BLK_PERM_ALL);
388 ret = blk_insert_bs(s->top, top, errp);
389 if (ret < 0) {
390 goto fail;
391 }
392 blk_set_disable_request_queuing(s->top, true);
393
394 s->backing_file_str = g_strdup(backing_file_str);
395 s->on_error = on_error;
396
397 trace_commit_start(bs, base, top, s);
398 job_start(&s->common.job);
399 return;
400
401 fail:
402 if (s->chain_frozen) {
403 bdrv_unfreeze_backing_chain(commit_top_bs, base);
404 }
405 if (s->base) {
406 blk_unref(s->base);
407 }
408 if (s->top) {
409 blk_unref(s->top);
410 }
411 if (s->base_read_only) {
412 bdrv_reopen_set_read_only(base, true, NULL);
413 }
414 job_early_fail(&s->common.job);
415 /* commit_top_bs has to be replaced after deleting the block job,
416 * otherwise this would fail because of lack of permissions. */
417 if (commit_top_bs) {
418 bdrv_replace_node(commit_top_bs, top, &error_abort);
419 }
420 }
421
422
423 #define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE)
424
425 /* commit COW file into the raw image */
426 int bdrv_commit(BlockDriverState *bs)
427 {
428 BlockBackend *src, *backing;
429 BlockDriverState *backing_file_bs = NULL;
430 BlockDriverState *commit_top_bs = NULL;
431 BlockDriver *drv = bs->drv;
432 AioContext *ctx;
433 int64_t offset, length, backing_length;
434 int ro;
435 int64_t n;
436 int ret = 0;
437 uint8_t *buf = NULL;
438 Error *local_err = NULL;
439
440 if (!drv)
441 return -ENOMEDIUM;
442
443 backing_file_bs = bdrv_cow_bs(bs);
444
445 if (!backing_file_bs) {
446 return -ENOTSUP;
447 }
448
449 if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
450 bdrv_op_is_blocked(backing_file_bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL))
451 {
452 return -EBUSY;
453 }
454
455 ro = backing_file_bs->read_only;
456
457 if (ro) {
458 if (bdrv_reopen_set_read_only(backing_file_bs, false, NULL)) {
459 return -EACCES;
460 }
461 }
462
463 ctx = bdrv_get_aio_context(bs);
464 /* WRITE_UNCHANGED is required for bdrv_make_empty() */
465 src = blk_new(ctx, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED,
466 BLK_PERM_ALL);
467 backing = blk_new(ctx, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
468
469 ret = blk_insert_bs(src, bs, &local_err);
470 if (ret < 0) {
471 error_report_err(local_err);
472 goto ro_cleanup;
473 }
474
475 /* Insert commit_top block node above backing, so we can write to it */
476 commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR,
477 &local_err);
478 if (commit_top_bs == NULL) {
479 error_report_err(local_err);
480 goto ro_cleanup;
481 }
482
483 bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort);
484 bdrv_set_backing_hd(bs, commit_top_bs, &error_abort);
485
486 ret = blk_insert_bs(backing, backing_file_bs, &local_err);
487 if (ret < 0) {
488 error_report_err(local_err);
489 goto ro_cleanup;
490 }
491
492 length = blk_getlength(src);
493 if (length < 0) {
494 ret = length;
495 goto ro_cleanup;
496 }
497
498 backing_length = blk_getlength(backing);
499 if (backing_length < 0) {
500 ret = backing_length;
501 goto ro_cleanup;
502 }
503
504 /* If our top snapshot is larger than the backing file image,
505 * grow the backing file image if possible. If not possible,
506 * we must return an error */
507 if (length > backing_length) {
508 ret = blk_truncate(backing, length, false, PREALLOC_MODE_OFF, 0,
509 &local_err);
510 if (ret < 0) {
511 error_report_err(local_err);
512 goto ro_cleanup;
513 }
514 }
515
516 /* blk_try_blockalign() for src will choose an alignment that works for
517 * backing as well, so no need to compare the alignment manually. */
518 buf = blk_try_blockalign(src, COMMIT_BUF_SIZE);
519 if (buf == NULL) {
520 ret = -ENOMEM;
521 goto ro_cleanup;
522 }
523
524 for (offset = 0; offset < length; offset += n) {
525 ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n);
526 if (ret < 0) {
527 goto ro_cleanup;
528 }
529 if (ret) {
530 ret = blk_pread(src, offset, buf, n);
531 if (ret < 0) {
532 goto ro_cleanup;
533 }
534
535 ret = blk_pwrite(backing, offset, buf, n, 0);
536 if (ret < 0) {
537 goto ro_cleanup;
538 }
539 }
540 }
541
542 ret = blk_make_empty(src, NULL);
543 /* Ignore -ENOTSUP */
544 if (ret < 0 && ret != -ENOTSUP) {
545 goto ro_cleanup;
546 }
547
548 blk_flush(src);
549
550 /*
551 * Make sure all data we wrote to the backing device is actually
552 * stable on disk.
553 */
554 blk_flush(backing);
555
556 ret = 0;
557 ro_cleanup:
558 qemu_vfree(buf);
559
560 blk_unref(backing);
561 if (bdrv_cow_bs(bs) != backing_file_bs) {
562 bdrv_set_backing_hd(bs, backing_file_bs, &error_abort);
563 }
564 bdrv_unref(commit_top_bs);
565 blk_unref(src);
566
567 if (ro) {
568 /* ignoring error return here */
569 bdrv_reopen_set_read_only(backing_file_bs, true, NULL);
570 }
571
572 return ret;
573 }