commit: Make base read-only if there is an early failure
[qemu/ar7.git] / block / commit.c
blob27537d995b6050ebb2992e6833c2af77fbf331a7
1 /*
2 * Live block commit
4 * Copyright Red Hat, Inc. 2012
6 * Authors:
7 * Jeff Cody <jcody@redhat.com>
8 * Based on stream.c by Stefan Hajnoczi
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.
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"
25 enum {
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.
31 COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */
34 typedef struct CommitBlockJob {
35 BlockJob common;
36 BlockDriverState *commit_top_bs;
37 BlockBackend *top;
38 BlockBackend *base;
39 BlockDriverState *base_bs;
40 BlockdevOnError on_error;
41 bool base_read_only;
42 bool chain_frozen;
43 char *backing_file_str;
44 } CommitBlockJob;
46 static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
47 int64_t offset, uint64_t bytes,
48 void *buf)
50 int ret = 0;
52 assert(bytes < SIZE_MAX);
54 ret = blk_co_pread(bs, offset, bytes, buf, 0);
55 if (ret < 0) {
56 return ret;
59 ret = blk_co_pwrite(base, offset, bytes, buf, 0);
60 if (ret < 0) {
61 return ret;
64 return 0;
67 static int commit_prepare(Job *job)
69 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
71 bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
72 s->chain_frozen = false;
74 /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before
75 * the normal backing chain can be restored. */
76 blk_unref(s->base);
77 s->base = NULL;
79 /* FIXME: bdrv_drop_intermediate treats total failures and partial failures
80 * identically. Further work is needed to disambiguate these cases. */
81 return bdrv_drop_intermediate(s->commit_top_bs, s->base_bs,
82 s->backing_file_str);
85 static void commit_abort(Job *job)
87 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
88 BlockDriverState *top_bs = blk_bs(s->top);
90 if (s->chain_frozen) {
91 bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
94 /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */
95 bdrv_ref(top_bs);
96 bdrv_ref(s->commit_top_bs);
98 if (s->base) {
99 blk_unref(s->base);
102 /* free the blockers on the intermediate nodes so that bdrv_replace_nodes
103 * can succeed */
104 block_job_remove_all_bdrv(&s->common);
106 /* If bdrv_drop_intermediate() failed (or was not invoked), remove the
107 * commit filter driver from the backing chain now. Do this as the final
108 * step so that the 'consistent read' permission can be granted.
110 * XXX Can (or should) we somehow keep 'consistent read' blocked even
111 * after the failed/cancelled commit job is gone? If we already wrote
112 * something to base, the intermediate images aren't valid any more. */
113 bdrv_child_try_set_perm(s->commit_top_bs->backing, 0, BLK_PERM_ALL,
114 &error_abort);
115 bdrv_replace_node(s->commit_top_bs, backing_bs(s->commit_top_bs),
116 &error_abort);
118 bdrv_unref(s->commit_top_bs);
119 bdrv_unref(top_bs);
122 static void commit_clean(Job *job)
124 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
126 /* restore base open flags here if appropriate (e.g., change the base back
127 * to r/o). These reopens do not need to be atomic, since we won't abort
128 * even on failure here */
129 if (s->base_read_only) {
130 bdrv_reopen_set_read_only(s->base_bs, true, NULL);
133 g_free(s->backing_file_str);
134 blk_unref(s->top);
137 static int coroutine_fn commit_run(Job *job, Error **errp)
139 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
140 int64_t offset;
141 uint64_t delay_ns = 0;
142 int ret = 0;
143 int64_t n = 0; /* bytes */
144 void *buf = NULL;
145 int bytes_written = 0;
146 int64_t len, base_len;
148 ret = len = blk_getlength(s->top);
149 if (len < 0) {
150 goto out;
152 job_progress_set_remaining(&s->common.job, len);
154 ret = base_len = blk_getlength(s->base);
155 if (base_len < 0) {
156 goto out;
159 if (base_len < len) {
160 ret = blk_truncate(s->base, len, PREALLOC_MODE_OFF, NULL);
161 if (ret) {
162 goto out;
166 buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
168 for (offset = 0; offset < len; offset += n) {
169 bool copy;
171 /* Note that even when no rate limit is applied we need to yield
172 * with no pending I/O here so that bdrv_drain_all() returns.
174 job_sleep_ns(&s->common.job, delay_ns);
175 if (job_is_cancelled(&s->common.job)) {
176 break;
178 /* Copy if allocated above the base */
179 ret = bdrv_is_allocated_above(blk_bs(s->top), blk_bs(s->base),
180 offset, COMMIT_BUFFER_SIZE, &n);
181 copy = (ret == 1);
182 trace_commit_one_iteration(s, offset, n, ret);
183 if (copy) {
184 ret = commit_populate(s->top, s->base, offset, n, buf);
185 bytes_written += n;
187 if (ret < 0) {
188 BlockErrorAction action =
189 block_job_error_action(&s->common, false, s->on_error, -ret);
190 if (action == BLOCK_ERROR_ACTION_REPORT) {
191 goto out;
192 } else {
193 n = 0;
194 continue;
197 /* Publish progress */
198 job_progress_update(&s->common.job, n);
200 if (copy) {
201 delay_ns = block_job_ratelimit_get_delay(&s->common, n);
202 } else {
203 delay_ns = 0;
207 ret = 0;
209 out:
210 qemu_vfree(buf);
212 return ret;
215 static const BlockJobDriver commit_job_driver = {
216 .job_driver = {
217 .instance_size = sizeof(CommitBlockJob),
218 .job_type = JOB_TYPE_COMMIT,
219 .free = block_job_free,
220 .user_resume = block_job_user_resume,
221 .drain = block_job_drain,
222 .run = commit_run,
223 .prepare = commit_prepare,
224 .abort = commit_abort,
225 .clean = commit_clean
229 static int coroutine_fn bdrv_commit_top_preadv(BlockDriverState *bs,
230 uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
232 return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
235 static void bdrv_commit_top_refresh_filename(BlockDriverState *bs)
237 pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
238 bs->backing->bs->filename);
241 static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c,
242 const BdrvChildRole *role,
243 BlockReopenQueue *reopen_queue,
244 uint64_t perm, uint64_t shared,
245 uint64_t *nperm, uint64_t *nshared)
247 *nperm = 0;
248 *nshared = BLK_PERM_ALL;
251 /* Dummy node that provides consistent read to its users without requiring it
252 * from its backing file and that allows writes on the backing file chain. */
253 static BlockDriver bdrv_commit_top = {
254 .format_name = "commit_top",
255 .bdrv_co_preadv = bdrv_commit_top_preadv,
256 .bdrv_co_block_status = bdrv_co_block_status_from_backing,
257 .bdrv_refresh_filename = bdrv_commit_top_refresh_filename,
258 .bdrv_child_perm = bdrv_commit_top_child_perm,
261 void commit_start(const char *job_id, BlockDriverState *bs,
262 BlockDriverState *base, BlockDriverState *top,
263 int creation_flags, int64_t speed,
264 BlockdevOnError on_error, const char *backing_file_str,
265 const char *filter_node_name, Error **errp)
267 CommitBlockJob *s;
268 BlockDriverState *iter;
269 BlockDriverState *commit_top_bs = NULL;
270 Error *local_err = NULL;
271 int ret;
273 assert(top != bs);
274 if (top == base) {
275 error_setg(errp, "Invalid files for merge: top and base are the same");
276 return;
279 s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL,
280 speed, creation_flags, NULL, NULL, errp);
281 if (!s) {
282 return;
285 /* convert base to r/w, if necessary */
286 s->base_read_only = bdrv_is_read_only(base);
287 if (s->base_read_only) {
288 if (bdrv_reopen_set_read_only(base, false, errp) != 0) {
289 goto fail;
293 /* Insert commit_top block node above top, so we can block consistent read
294 * on the backing chain below it */
295 commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, filter_node_name, 0,
296 errp);
297 if (commit_top_bs == NULL) {
298 goto fail;
300 if (!filter_node_name) {
301 commit_top_bs->implicit = true;
303 commit_top_bs->total_sectors = top->total_sectors;
304 bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(top));
306 bdrv_set_backing_hd(commit_top_bs, top, &local_err);
307 if (local_err) {
308 bdrv_unref(commit_top_bs);
309 commit_top_bs = NULL;
310 error_propagate(errp, local_err);
311 goto fail;
313 bdrv_replace_node(top, commit_top_bs, &local_err);
314 if (local_err) {
315 bdrv_unref(commit_top_bs);
316 commit_top_bs = NULL;
317 error_propagate(errp, local_err);
318 goto fail;
321 s->commit_top_bs = commit_top_bs;
322 bdrv_unref(commit_top_bs);
324 /* Block all nodes between top and base, because they will
325 * disappear from the chain after this operation. */
326 assert(bdrv_chain_contains(top, base));
327 for (iter = top; iter != base; iter = backing_bs(iter)) {
328 /* XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves
329 * at s->base (if writes are blocked for a node, they are also blocked
330 * for its backing file). The other options would be a second filter
331 * driver above s->base. */
332 ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
333 BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE,
334 errp);
335 if (ret < 0) {
336 goto fail;
340 if (bdrv_freeze_backing_chain(commit_top_bs, base, errp) < 0) {
341 goto fail;
343 s->chain_frozen = true;
345 ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp);
346 if (ret < 0) {
347 goto fail;
350 s->base = blk_new(BLK_PERM_CONSISTENT_READ
351 | BLK_PERM_WRITE
352 | BLK_PERM_RESIZE,
353 BLK_PERM_CONSISTENT_READ
354 | BLK_PERM_GRAPH_MOD
355 | BLK_PERM_WRITE_UNCHANGED);
356 ret = blk_insert_bs(s->base, base, errp);
357 if (ret < 0) {
358 goto fail;
360 s->base_bs = base;
362 /* Required permissions are already taken with block_job_add_bdrv() */
363 s->top = blk_new(0, BLK_PERM_ALL);
364 ret = blk_insert_bs(s->top, top, errp);
365 if (ret < 0) {
366 goto fail;
369 s->backing_file_str = g_strdup(backing_file_str);
370 s->on_error = on_error;
372 trace_commit_start(bs, base, top, s);
373 job_start(&s->common.job);
374 return;
376 fail:
377 if (s->chain_frozen) {
378 bdrv_unfreeze_backing_chain(commit_top_bs, base);
380 if (s->base) {
381 blk_unref(s->base);
383 if (s->top) {
384 blk_unref(s->top);
386 if (s->base_read_only) {
387 bdrv_reopen_set_read_only(base, true, NULL);
389 job_early_fail(&s->common.job);
390 /* commit_top_bs has to be replaced after deleting the block job,
391 * otherwise this would fail because of lack of permissions. */
392 if (commit_top_bs) {
393 bdrv_replace_node(commit_top_bs, top, &error_abort);
398 #define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE)
400 /* commit COW file into the raw image */
401 int bdrv_commit(BlockDriverState *bs)
403 BlockBackend *src, *backing;
404 BlockDriverState *backing_file_bs = NULL;
405 BlockDriverState *commit_top_bs = NULL;
406 BlockDriver *drv = bs->drv;
407 int64_t offset, length, backing_length;
408 int ro;
409 int64_t n;
410 int ret = 0;
411 uint8_t *buf = NULL;
412 Error *local_err = NULL;
414 if (!drv)
415 return -ENOMEDIUM;
417 if (!bs->backing) {
418 return -ENOTSUP;
421 if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
422 bdrv_op_is_blocked(bs->backing->bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) {
423 return -EBUSY;
426 ro = bs->backing->bs->read_only;
428 if (ro) {
429 if (bdrv_reopen_set_read_only(bs->backing->bs, false, NULL)) {
430 return -EACCES;
434 src = blk_new(BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL);
435 backing = blk_new(BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
437 ret = blk_insert_bs(src, bs, &local_err);
438 if (ret < 0) {
439 error_report_err(local_err);
440 goto ro_cleanup;
443 /* Insert commit_top block node above backing, so we can write to it */
444 backing_file_bs = backing_bs(bs);
446 commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR,
447 &local_err);
448 if (commit_top_bs == NULL) {
449 error_report_err(local_err);
450 goto ro_cleanup;
452 bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(backing_file_bs));
454 bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort);
455 bdrv_set_backing_hd(bs, commit_top_bs, &error_abort);
457 ret = blk_insert_bs(backing, backing_file_bs, &local_err);
458 if (ret < 0) {
459 error_report_err(local_err);
460 goto ro_cleanup;
463 length = blk_getlength(src);
464 if (length < 0) {
465 ret = length;
466 goto ro_cleanup;
469 backing_length = blk_getlength(backing);
470 if (backing_length < 0) {
471 ret = backing_length;
472 goto ro_cleanup;
475 /* If our top snapshot is larger than the backing file image,
476 * grow the backing file image if possible. If not possible,
477 * we must return an error */
478 if (length > backing_length) {
479 ret = blk_truncate(backing, length, PREALLOC_MODE_OFF, &local_err);
480 if (ret < 0) {
481 error_report_err(local_err);
482 goto ro_cleanup;
486 /* blk_try_blockalign() for src will choose an alignment that works for
487 * backing as well, so no need to compare the alignment manually. */
488 buf = blk_try_blockalign(src, COMMIT_BUF_SIZE);
489 if (buf == NULL) {
490 ret = -ENOMEM;
491 goto ro_cleanup;
494 for (offset = 0; offset < length; offset += n) {
495 ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n);
496 if (ret < 0) {
497 goto ro_cleanup;
499 if (ret) {
500 ret = blk_pread(src, offset, buf, n);
501 if (ret < 0) {
502 goto ro_cleanup;
505 ret = blk_pwrite(backing, offset, buf, n, 0);
506 if (ret < 0) {
507 goto ro_cleanup;
512 if (drv->bdrv_make_empty) {
513 ret = drv->bdrv_make_empty(bs);
514 if (ret < 0) {
515 goto ro_cleanup;
517 blk_flush(src);
521 * Make sure all data we wrote to the backing device is actually
522 * stable on disk.
524 blk_flush(backing);
526 ret = 0;
527 ro_cleanup:
528 qemu_vfree(buf);
530 blk_unref(backing);
531 if (backing_file_bs) {
532 bdrv_set_backing_hd(bs, backing_file_bs, &error_abort);
534 bdrv_unref(commit_top_bs);
535 blk_unref(src);
537 if (ro) {
538 /* ignoring error return here */
539 bdrv_reopen_set_read_only(bs->backing->bs, true, NULL);
542 return ret;