4 * Copyright Red Hat, Inc. 2012
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"
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"
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 {
36 BlockDriverState *commit_top_bs;
39 BlockDriverState *base_bs;
40 BlockDriverState *base_overlay;
41 BlockdevOnError on_error;
44 char *backing_file_str;
47 static int commit_prepare(Job *job)
49 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
51 bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
52 s->chain_frozen = false;
54 /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before
55 * the normal backing chain can be restored. */
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,
65 static void commit_abort(Job *job)
67 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
68 BlockDriverState *top_bs = blk_bs(s->top);
70 if (s->chain_frozen) {
71 bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
74 /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */
76 bdrv_ref(s->commit_top_bs);
82 /* free the blockers on the intermediate nodes so that bdrv_replace_nodes
84 block_job_remove_all_bdrv(&s->common);
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.
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,
96 bdrv_unref(s->commit_top_bs);
100 static void commit_clean(Job *job)
102 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
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);
111 g_free(s->backing_file_str);
115 static int coroutine_fn commit_run(Job *job, Error **errp)
117 CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
119 uint64_t delay_ns = 0;
121 int64_t n = 0; /* bytes */
123 int64_t len, base_len;
125 ret = len = blk_getlength(s->top);
129 job_progress_set_remaining(&s->common.job, len);
131 ret = base_len = blk_getlength(s->base);
136 if (base_len < len) {
137 ret = blk_truncate(s->base, len, false, PREALLOC_MODE_OFF, 0, NULL);
143 buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
145 for (offset = 0; offset < len; offset += n) {
147 bool error_in_source = true;
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.
152 job_sleep_ns(&s->common.job, delay_ns);
153 if (job_is_cancelled(&s->common.job)) {
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);
160 trace_commit_one_iteration(s, offset, n, ret);
162 assert(n < SIZE_MAX);
164 ret = blk_co_pread(s->top, offset, n, buf, 0);
166 ret = blk_co_pwrite(s->base, offset, n, buf, 0);
168 error_in_source = false;
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) {
183 /* Publish progress */
184 job_progress_update(&s->common.job, n);
187 delay_ns = block_job_ratelimit_get_delay(&s->common, n);
201 static const BlockJobDriver commit_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,
208 .prepare = commit_prepare,
209 .abort = commit_abort,
210 .clean = commit_clean
214 static int coroutine_fn bdrv_commit_top_preadv(BlockDriverState *bs,
215 uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
217 return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
220 static void bdrv_commit_top_refresh_filename(BlockDriverState *bs)
222 pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
223 bs->backing->bs->filename);
226 static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c,
228 BlockReopenQueue *reopen_queue,
229 uint64_t perm, uint64_t shared,
230 uint64_t *nperm, uint64_t *nshared)
233 *nshared = BLK_PERM_ALL;
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,
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)
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;
262 if (bdrv_skip_filters(top) == bdrv_skip_filters(base)) {
263 error_setg(errp, "Invalid files for merge: top and base are the same");
267 base_size = bdrv_getlength(base);
269 error_setg_errno(errp, -base_size, "Could not inquire base image size");
273 top_size = bdrv_getlength(top);
275 error_setg_errno(errp, -top_size, "Could not inquire top image size");
279 base_perms = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE;
280 if (base_size < top_size) {
281 base_perms |= BLK_PERM_RESIZE;
284 s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL,
285 speed, creation_flags, NULL, NULL, errp);
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) {
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,
302 if (commit_top_bs == NULL) {
305 if (!filter_node_name) {
306 commit_top_bs->implicit = true;
309 /* So that we can always drop this node */
310 commit_top_bs->never_freeze = true;
312 commit_top_bs->total_sectors = top->total_sectors;
314 ret = bdrv_append(commit_top_bs, top, errp);
315 bdrv_unref(commit_top_bs); /* referenced by new parents or failed */
317 commit_top_bs = NULL;
321 s->commit_top_bs = commit_top_bs;
324 * Block all nodes between top and base, because they will
325 * disappear from the chain after this operation.
326 * Note that this assumes that the user is fine with removing all
327 * nodes (including R/W filters) between top and base. Assuring
328 * this is the responsibility of the interface (i.e. whoever calls
331 s->base_overlay = bdrv_find_overlay(top, base);
332 assert(s->base_overlay);
335 * The topmost node with
336 * bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base)
338 filtered_base = bdrv_cow_bs(s->base_overlay);
339 assert(bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base));
342 * XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves
343 * at s->base (if writes are blocked for a node, they are also blocked
344 * for its backing file). The other options would be a second filter
345 * driver above s->base.
347 iter_shared_perms = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE;
349 for (iter = top; iter != base; iter = bdrv_filter_or_cow_bs(iter)) {
350 if (iter == filtered_base) {
352 * From here on, all nodes are filters on the base. This
353 * allows us to share BLK_PERM_CONSISTENT_READ.
355 iter_shared_perms |= BLK_PERM_CONSISTENT_READ;
358 ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
359 iter_shared_perms, errp);
365 if (bdrv_freeze_backing_chain(commit_top_bs, base, errp) < 0) {
368 s->chain_frozen = true;
370 ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp);
375 s->base = blk_new(s->common.job.aio_context,
377 BLK_PERM_CONSISTENT_READ
379 | BLK_PERM_WRITE_UNCHANGED);
380 ret = blk_insert_bs(s->base, base, errp);
384 blk_set_disable_request_queuing(s->base, true);
387 /* Required permissions are already taken with block_job_add_bdrv() */
388 s->top = blk_new(s->common.job.aio_context, 0, BLK_PERM_ALL);
389 ret = blk_insert_bs(s->top, top, errp);
393 blk_set_disable_request_queuing(s->top, true);
395 s->backing_file_str = g_strdup(backing_file_str);
396 s->on_error = on_error;
398 trace_commit_start(bs, base, top, s);
399 job_start(&s->common.job);
403 if (s->chain_frozen) {
404 bdrv_unfreeze_backing_chain(commit_top_bs, base);
412 if (s->base_read_only) {
413 bdrv_reopen_set_read_only(base, true, NULL);
415 job_early_fail(&s->common.job);
416 /* commit_top_bs has to be replaced after deleting the block job,
417 * otherwise this would fail because of lack of permissions. */
419 bdrv_replace_node(commit_top_bs, top, &error_abort);
424 #define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE)
426 /* commit COW file into the raw image */
427 int bdrv_commit(BlockDriverState *bs)
429 BlockBackend *src, *backing;
430 BlockDriverState *backing_file_bs = NULL;
431 BlockDriverState *commit_top_bs = NULL;
432 BlockDriver *drv = bs->drv;
434 int64_t offset, length, backing_length;
439 Error *local_err = NULL;
444 backing_file_bs = bdrv_cow_bs(bs);
446 if (!backing_file_bs) {
450 if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
451 bdrv_op_is_blocked(backing_file_bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL))
456 ro = backing_file_bs->read_only;
459 if (bdrv_reopen_set_read_only(backing_file_bs, false, NULL)) {
464 ctx = bdrv_get_aio_context(bs);
465 /* WRITE_UNCHANGED is required for bdrv_make_empty() */
466 src = blk_new(ctx, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED,
468 backing = blk_new(ctx, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
470 ret = blk_insert_bs(src, bs, &local_err);
472 error_report_err(local_err);
476 /* Insert commit_top block node above backing, so we can write to it */
477 commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR,
479 if (commit_top_bs == NULL) {
480 error_report_err(local_err);
484 bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort);
485 bdrv_set_backing_hd(bs, commit_top_bs, &error_abort);
487 ret = blk_insert_bs(backing, backing_file_bs, &local_err);
489 error_report_err(local_err);
493 length = blk_getlength(src);
499 backing_length = blk_getlength(backing);
500 if (backing_length < 0) {
501 ret = backing_length;
505 /* If our top snapshot is larger than the backing file image,
506 * grow the backing file image if possible. If not possible,
507 * we must return an error */
508 if (length > backing_length) {
509 ret = blk_truncate(backing, length, false, PREALLOC_MODE_OFF, 0,
512 error_report_err(local_err);
517 /* blk_try_blockalign() for src will choose an alignment that works for
518 * backing as well, so no need to compare the alignment manually. */
519 buf = blk_try_blockalign(src, COMMIT_BUF_SIZE);
525 for (offset = 0; offset < length; offset += n) {
526 ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n);
531 ret = blk_pread(src, offset, buf, n);
536 ret = blk_pwrite(backing, offset, buf, n, 0);
543 ret = blk_make_empty(src, NULL);
544 /* Ignore -ENOTSUP */
545 if (ret < 0 && ret != -ENOTSUP) {
552 * Make sure all data we wrote to the backing device is actually
562 if (bdrv_cow_bs(bs) != backing_file_bs) {
563 bdrv_set_backing_hd(bs, backing_file_bs, &error_abort);
565 bdrv_unref(commit_top_bs);
569 /* ignoring error return here */
570 bdrv_reopen_set_read_only(backing_file_bs, true, NULL);