| 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-common.h" |
| 19 | #include "block/coroutines.h" |
| 20 | #include "block/block_int.h" |
| 21 | #include "block/blockjob_int.h" |
| 22 | #include "qapi/error.h" |
| 23 | #include "qemu/ratelimit.h" |
| 24 | #include "qemu/memalign.h" |
| 25 | #include "system/block-backend.h" |
| 26 | |
| 27 | enum { |
| 28 | /* |
| 29 | * Size of data buffer for populating the image file. This should be large |
| 30 | * enough to process multiple clusters in a single call, so that populating |
| 31 | * contiguous regions of the image is efficient. |
| 32 | */ |
| 33 | COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */ |
| 34 | }; |
| 35 | |
| 36 | typedef struct CommitBlockJob { |
| 37 | BlockJob common; |
| 38 | BlockDriverState *commit_top_bs; |
| 39 | BlockBackend *top; |
| 40 | BlockBackend *base; |
| 41 | BlockDriverState *base_bs; |
| 42 | BlockDriverState *base_overlay; |
| 43 | BlockdevOnError on_error; |
| 44 | bool base_read_only; |
| 45 | bool chain_frozen; |
| 46 | char *backing_file_str; |
| 47 | bool backing_mask_protocol; |
| 48 | } CommitBlockJob; |
| 49 | |
| 50 | static int commit_prepare(Job *job) |
| 51 | { |
| 52 | CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); |
| 53 | |
| 54 | bdrv_graph_rdlock_main_loop(); |
| 55 | bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs); |
| 56 | s->chain_frozen = false; |
| 57 | bdrv_graph_rdunlock_main_loop(); |
| 58 | |
| 59 | /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before |
| 60 | * the normal backing chain can be restored. */ |
| 61 | blk_unref(s->base); |
| 62 | s->base = NULL; |
| 63 | |
| 64 | /* FIXME: bdrv_drop_intermediate treats total failures and partial failures |
| 65 | * identically. Further work is needed to disambiguate these cases. */ |
| 66 | return bdrv_drop_intermediate(s->commit_top_bs, s->base_bs, |
| 67 | s->backing_file_str, |
| 68 | s->backing_mask_protocol); |
| 69 | } |
| 70 | |
| 71 | static void GRAPH_UNLOCKED commit_abort(Job *job) |
| 72 | { |
| 73 | CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); |
| 74 | BlockDriverState *top_bs = blk_bs(s->top); |
| 75 | BlockDriverState *commit_top_backing_bs; |
| 76 | |
| 77 | if (s->chain_frozen) { |
| 78 | bdrv_graph_rdlock_main_loop(); |
| 79 | bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs); |
| 80 | bdrv_graph_rdunlock_main_loop(); |
| 81 | } |
| 82 | |
| 83 | /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */ |
| 84 | bdrv_ref(top_bs); |
| 85 | bdrv_ref(s->commit_top_bs); |
| 86 | |
| 87 | if (s->base) { |
| 88 | blk_unref(s->base); |
| 89 | } |
| 90 | |
| 91 | /* free the blockers on the intermediate nodes so that bdrv_replace_nodes |
| 92 | * can succeed */ |
| 93 | block_job_remove_all_bdrv(&s->common); |
| 94 | |
| 95 | /* If bdrv_drop_intermediate() failed (or was not invoked), remove the |
| 96 | * commit filter driver from the backing chain now. Do this as the final |
| 97 | * step so that the 'consistent read' permission can be granted. |
| 98 | * |
| 99 | * XXX Can (or should) we somehow keep 'consistent read' blocked even |
| 100 | * after the failed/cancelled commit job is gone? If we already wrote |
| 101 | * something to base, the intermediate images aren't valid any more. */ |
| 102 | bdrv_graph_rdlock_main_loop(); |
| 103 | commit_top_backing_bs = s->commit_top_bs->backing->bs; |
| 104 | bdrv_graph_rdunlock_main_loop(); |
| 105 | |
| 106 | bdrv_drained_begin(commit_top_backing_bs); |
| 107 | bdrv_graph_wrlock(); |
| 108 | bdrv_replace_node(s->commit_top_bs, commit_top_backing_bs, &error_abort); |
| 109 | bdrv_graph_wrunlock(); |
| 110 | bdrv_drained_end(commit_top_backing_bs); |
| 111 | |
| 112 | bdrv_unref(s->commit_top_bs); |
| 113 | bdrv_unref(top_bs); |
| 114 | } |
| 115 | |
| 116 | static void commit_clean(Job *job) |
| 117 | { |
| 118 | CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); |
| 119 | |
| 120 | /* restore base open flags here if appropriate (e.g., change the base back |
| 121 | * to r/o). These reopens do not need to be atomic, since we won't abort |
| 122 | * even on failure here */ |
| 123 | if (s->base_read_only) { |
| 124 | bdrv_reopen_set_read_only(s->base_bs, true, NULL); |
| 125 | } |
| 126 | |
| 127 | g_free(s->backing_file_str); |
| 128 | blk_unref(s->top); |
| 129 | } |
| 130 | |
| 131 | static int coroutine_fn |
| 132 | commit_iteration(CommitBlockJob *s, int64_t offset, |
| 133 | int64_t *requested_bytes, void *buf) |
| 134 | { |
| 135 | BlockErrorAction action; |
| 136 | int64_t bytes = *requested_bytes; |
| 137 | int ret = 0; |
| 138 | bool error_in_source = true; |
| 139 | |
| 140 | /* Copy if allocated above the base */ |
| 141 | WITH_GRAPH_RDLOCK_GUARD() { |
| 142 | ret = bdrv_co_common_block_status_above(blk_bs(s->top), |
| 143 | s->base_overlay, true, true, offset, COMMIT_BUFFER_SIZE, |
| 144 | &bytes, NULL, NULL, NULL); |
| 145 | } |
| 146 | |
| 147 | trace_commit_one_iteration(s, offset, bytes, ret); |
| 148 | |
| 149 | if (ret < 0) { |
| 150 | goto fail; |
| 151 | } |
| 152 | |
| 153 | if (ret & BDRV_BLOCK_ALLOCATED) { |
| 154 | if (ret & BDRV_BLOCK_ZERO) { |
| 155 | /* |
| 156 | * If the top (sub)clusters are smaller than the base |
| 157 | * (sub)clusters, this will not unmap unless the underlying device |
| 158 | * does some tracking of these requests. Ideally, we would find |
| 159 | * the maximal extent of the zero clusters. |
| 160 | */ |
| 161 | ret = blk_co_pwrite_zeroes(s->base, offset, bytes, |
| 162 | BDRV_REQ_MAY_UNMAP); |
| 163 | if (ret < 0) { |
| 164 | error_in_source = false; |
| 165 | goto fail; |
| 166 | } |
| 167 | } else { |
| 168 | assert(bytes < SIZE_MAX); |
| 169 | |
| 170 | ret = blk_co_pread(s->top, offset, bytes, buf, 0); |
| 171 | if (ret < 0) { |
| 172 | goto fail; |
| 173 | } |
| 174 | |
| 175 | ret = blk_co_pwrite(s->base, offset, bytes, buf, 0); |
| 176 | if (ret < 0) { |
| 177 | error_in_source = false; |
| 178 | goto fail; |
| 179 | } |
| 180 | } |
| 181 | |
| 182 | /* |
| 183 | * Whether zeroes actually end up on disk depends on the details of |
| 184 | * the underlying driver. Therefore, this might rate limit more than |
| 185 | * is necessary. |
| 186 | */ |
| 187 | block_job_ratelimit_processed_bytes(&s->common, bytes); |
| 188 | } |
| 189 | |
| 190 | /* Publish progress */ |
| 191 | |
| 192 | job_progress_update(&s->common.job, bytes); |
| 193 | |
| 194 | *requested_bytes = bytes; |
| 195 | |
| 196 | return 0; |
| 197 | |
| 198 | fail: |
| 199 | action = block_job_error_action(&s->common, s->on_error, |
| 200 | error_in_source, -ret); |
| 201 | if (action == BLOCK_ERROR_ACTION_REPORT) { |
| 202 | return ret; |
| 203 | } |
| 204 | |
| 205 | *requested_bytes = 0; |
| 206 | |
| 207 | return 0; |
| 208 | } |
| 209 | |
| 210 | static int coroutine_fn commit_run(Job *job, Error **errp) |
| 211 | { |
| 212 | CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); |
| 213 | int64_t offset; |
| 214 | int ret = 0; |
| 215 | int64_t n = 0; /* bytes */ |
| 216 | QEMU_AUTO_VFREE void *buf = NULL; |
| 217 | int64_t len, base_len; |
| 218 | |
| 219 | len = blk_co_getlength(s->top); |
| 220 | if (len < 0) { |
| 221 | return len; |
| 222 | } |
| 223 | job_progress_set_remaining(&s->common.job, len); |
| 224 | |
| 225 | base_len = blk_co_getlength(s->base); |
| 226 | if (base_len < 0) { |
| 227 | return base_len; |
| 228 | } |
| 229 | |
| 230 | if (base_len < len) { |
| 231 | ret = blk_co_truncate(s->base, len, false, PREALLOC_MODE_OFF, 0, NULL); |
| 232 | if (ret) { |
| 233 | return ret; |
| 234 | } |
| 235 | } |
| 236 | |
| 237 | buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE); |
| 238 | |
| 239 | for (offset = 0; offset < len; offset += n) { |
| 240 | /* Note that even when no rate limit is applied we need to yield |
| 241 | * with no pending I/O here so that bdrv_drain_all() returns. |
| 242 | */ |
| 243 | block_job_ratelimit_sleep(&s->common); |
| 244 | if (job_is_cancelled(&s->common.job)) { |
| 245 | break; |
| 246 | } |
| 247 | |
| 248 | ret = commit_iteration(s, offset, &n, buf); |
| 249 | |
| 250 | if (ret < 0) { |
| 251 | return ret; |
| 252 | } |
| 253 | } |
| 254 | |
| 255 | return 0; |
| 256 | } |
| 257 | |
| 258 | static const BlockJobDriver commit_job_driver = { |
| 259 | .job_driver = { |
| 260 | .instance_size = sizeof(CommitBlockJob), |
| 261 | .job_type = JOB_TYPE_COMMIT, |
| 262 | .free = block_job_free, |
| 263 | .user_resume = block_job_user_resume, |
| 264 | .run = commit_run, |
| 265 | .prepare = commit_prepare, |
| 266 | .abort = commit_abort, |
| 267 | .clean = commit_clean |
| 268 | }, |
| 269 | }; |
| 270 | |
| 271 | static int coroutine_fn GRAPH_RDLOCK |
| 272 | bdrv_commit_top_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes, |
| 273 | QEMUIOVector *qiov, BdrvRequestFlags flags) |
| 274 | { |
| 275 | return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags); |
| 276 | } |
| 277 | |
| 278 | static GRAPH_RDLOCK void bdrv_commit_top_refresh_filename(BlockDriverState *bs) |
| 279 | { |
| 280 | pstrcpy(bs->exact_filename, sizeof(bs->exact_filename), |
| 281 | bs->backing->bs->filename); |
| 282 | } |
| 283 | |
| 284 | static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c, |
| 285 | BdrvChildRole role, |
| 286 | BlockReopenQueue *reopen_queue, |
| 287 | uint64_t perm, uint64_t shared, |
| 288 | uint64_t *nperm, uint64_t *nshared) |
| 289 | { |
| 290 | *nperm = 0; |
| 291 | *nshared = BLK_PERM_ALL; |
| 292 | } |
| 293 | |
| 294 | /* Dummy node that provides consistent read to its users without requiring it |
| 295 | * from its backing file and that allows writes on the backing file chain. */ |
| 296 | static BlockDriver bdrv_commit_top = { |
| 297 | .format_name = "commit_top", |
| 298 | .bdrv_co_preadv = bdrv_commit_top_preadv, |
| 299 | .bdrv_refresh_filename = bdrv_commit_top_refresh_filename, |
| 300 | .bdrv_child_perm = bdrv_commit_top_child_perm, |
| 301 | |
| 302 | .is_filter = true, |
| 303 | .filtered_child_is_backing = true, |
| 304 | }; |
| 305 | |
| 306 | void commit_start(const char *job_id, BlockDriverState *bs, |
| 307 | BlockDriverState *base, BlockDriverState *top, |
| 308 | int creation_flags, int64_t speed, |
| 309 | BlockdevOnError on_error, const char *backing_file_str, |
| 310 | bool backing_mask_protocol, |
| 311 | const char *filter_node_name, Error **errp) |
| 312 | { |
| 313 | CommitBlockJob *s; |
| 314 | BlockDriverState *iter; |
| 315 | BlockDriverState *commit_top_bs = NULL; |
| 316 | BlockDriverState *filtered_base; |
| 317 | int64_t base_size, top_size; |
| 318 | uint64_t base_perms, iter_shared_perms; |
| 319 | int ret; |
| 320 | |
| 321 | GLOBAL_STATE_CODE(); |
| 322 | |
| 323 | assert(top != bs); |
| 324 | bdrv_graph_rdlock_main_loop(); |
| 325 | if (bdrv_skip_filters(top) == bdrv_skip_filters(base)) { |
| 326 | error_setg(errp, "Invalid files for merge: top and base are the same"); |
| 327 | bdrv_graph_rdunlock_main_loop(); |
| 328 | return; |
| 329 | } |
| 330 | bdrv_graph_rdunlock_main_loop(); |
| 331 | |
| 332 | base_size = bdrv_getlength(base); |
| 333 | if (base_size < 0) { |
| 334 | error_setg_errno(errp, -base_size, "Could not inquire base image size"); |
| 335 | return; |
| 336 | } |
| 337 | |
| 338 | top_size = bdrv_getlength(top); |
| 339 | if (top_size < 0) { |
| 340 | error_setg_errno(errp, -top_size, "Could not inquire top image size"); |
| 341 | return; |
| 342 | } |
| 343 | |
| 344 | base_perms = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE; |
| 345 | if (base_size < top_size) { |
| 346 | base_perms |= BLK_PERM_RESIZE; |
| 347 | } |
| 348 | |
| 349 | s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL, |
| 350 | speed, creation_flags, NULL, NULL, errp); |
| 351 | if (!s) { |
| 352 | return; |
| 353 | } |
| 354 | |
| 355 | /* convert base to r/w, if necessary */ |
| 356 | s->base_read_only = bdrv_is_read_only(base); |
| 357 | if (s->base_read_only) { |
| 358 | if (bdrv_reopen_set_read_only(base, false, errp) != 0) { |
| 359 | goto fail; |
| 360 | } |
| 361 | } |
| 362 | |
| 363 | /* Insert commit_top block node above top, so we can block consistent read |
| 364 | * on the backing chain below it */ |
| 365 | commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, filter_node_name, 0, |
| 366 | errp); |
| 367 | if (commit_top_bs == NULL) { |
| 368 | goto fail; |
| 369 | } |
| 370 | if (!filter_node_name) { |
| 371 | commit_top_bs->implicit = true; |
| 372 | } |
| 373 | |
| 374 | /* So that we can always drop this node */ |
| 375 | commit_top_bs->never_freeze = true; |
| 376 | |
| 377 | commit_top_bs->total_sectors = top->total_sectors; |
| 378 | |
| 379 | ret = bdrv_append(commit_top_bs, top, errp); |
| 380 | bdrv_unref(commit_top_bs); /* referenced by new parents or failed */ |
| 381 | if (ret < 0) { |
| 382 | commit_top_bs = NULL; |
| 383 | goto fail; |
| 384 | } |
| 385 | |
| 386 | s->commit_top_bs = commit_top_bs; |
| 387 | |
| 388 | /* |
| 389 | * Block all nodes between top and base, because they will |
| 390 | * disappear from the chain after this operation. |
| 391 | * Note that this assumes that the user is fine with removing all |
| 392 | * nodes (including R/W filters) between top and base. Assuring |
| 393 | * this is the responsibility of the interface (i.e. whoever calls |
| 394 | * commit_start()). |
| 395 | */ |
| 396 | bdrv_graph_wrlock_drained(); |
| 397 | s->base_overlay = bdrv_find_overlay(top, base); |
| 398 | assert(s->base_overlay); |
| 399 | |
| 400 | /* |
| 401 | * The topmost node with |
| 402 | * bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base) |
| 403 | */ |
| 404 | filtered_base = bdrv_cow_bs(s->base_overlay); |
| 405 | assert(bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base)); |
| 406 | |
| 407 | /* |
| 408 | * XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves |
| 409 | * at s->base (if writes are blocked for a node, they are also blocked |
| 410 | * for its backing file). The other options would be a second filter |
| 411 | * driver above s->base. |
| 412 | */ |
| 413 | iter_shared_perms = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE; |
| 414 | |
| 415 | for (iter = top; iter != base; iter = bdrv_filter_or_cow_bs(iter)) { |
| 416 | if (iter == filtered_base) { |
| 417 | /* |
| 418 | * From here on, all nodes are filters on the base. This |
| 419 | * allows us to share BLK_PERM_CONSISTENT_READ. |
| 420 | */ |
| 421 | iter_shared_perms |= BLK_PERM_CONSISTENT_READ; |
| 422 | } |
| 423 | |
| 424 | ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0, |
| 425 | iter_shared_perms, errp); |
| 426 | if (ret < 0) { |
| 427 | bdrv_graph_wrunlock(); |
| 428 | goto fail; |
| 429 | } |
| 430 | } |
| 431 | |
| 432 | if (bdrv_freeze_backing_chain(commit_top_bs, base, errp) < 0) { |
| 433 | bdrv_graph_wrunlock(); |
| 434 | goto fail; |
| 435 | } |
| 436 | s->chain_frozen = true; |
| 437 | |
| 438 | ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp); |
| 439 | bdrv_graph_wrunlock(); |
| 440 | |
| 441 | if (ret < 0) { |
| 442 | goto fail; |
| 443 | } |
| 444 | |
| 445 | s->base = blk_new(s->common.job.aio_context, |
| 446 | base_perms, |
| 447 | BLK_PERM_CONSISTENT_READ |
| 448 | | BLK_PERM_WRITE_UNCHANGED); |
| 449 | ret = blk_insert_bs(s->base, base, errp); |
| 450 | if (ret < 0) { |
| 451 | goto fail; |
| 452 | } |
| 453 | blk_set_disable_request_queuing(s->base, true); |
| 454 | s->base_bs = base; |
| 455 | |
| 456 | /* Required permissions are already taken with block_job_add_bdrv() */ |
| 457 | s->top = blk_new(s->common.job.aio_context, 0, BLK_PERM_ALL); |
| 458 | ret = blk_insert_bs(s->top, top, errp); |
| 459 | if (ret < 0) { |
| 460 | goto fail; |
| 461 | } |
| 462 | blk_set_disable_request_queuing(s->top, true); |
| 463 | |
| 464 | s->backing_file_str = g_strdup(backing_file_str); |
| 465 | s->backing_mask_protocol = backing_mask_protocol; |
| 466 | s->on_error = on_error; |
| 467 | |
| 468 | trace_commit_start(bs, base, top, s); |
| 469 | job_start(&s->common.job); |
| 470 | return; |
| 471 | |
| 472 | fail: |
| 473 | if (s->chain_frozen) { |
| 474 | bdrv_graph_rdlock_main_loop(); |
| 475 | bdrv_unfreeze_backing_chain(commit_top_bs, base); |
| 476 | bdrv_graph_rdunlock_main_loop(); |
| 477 | } |
| 478 | if (s->base) { |
| 479 | blk_unref(s->base); |
| 480 | } |
| 481 | if (s->top) { |
| 482 | blk_unref(s->top); |
| 483 | } |
| 484 | if (s->base_read_only) { |
| 485 | bdrv_reopen_set_read_only(base, true, NULL); |
| 486 | } |
| 487 | job_early_fail(&s->common.job); |
| 488 | /* commit_top_bs has to be replaced after deleting the block job, |
| 489 | * otherwise this would fail because of lack of permissions. */ |
| 490 | if (commit_top_bs) { |
| 491 | bdrv_drained_begin(top); |
| 492 | bdrv_graph_wrlock(); |
| 493 | bdrv_replace_node(commit_top_bs, top, &error_abort); |
| 494 | bdrv_graph_wrunlock(); |
| 495 | bdrv_drained_end(top); |
| 496 | } |
| 497 | } |
| 498 | |
| 499 | |
| 500 | #define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE) |
| 501 | |
| 502 | /* commit COW file into the raw image */ |
| 503 | int bdrv_commit(BlockDriverState *bs) |
| 504 | { |
| 505 | BlockBackend *src, *backing; |
| 506 | BlockDriverState *backing_file_bs = NULL; |
| 507 | BlockDriverState *commit_top_bs = NULL; |
| 508 | BlockDriver *drv = bs->drv; |
| 509 | AioContext *ctx; |
| 510 | int64_t offset, length, backing_length; |
| 511 | int ro; |
| 512 | int64_t n; |
| 513 | int ret = 0; |
| 514 | QEMU_AUTO_VFREE uint8_t *buf = NULL; |
| 515 | Error *local_err = NULL; |
| 516 | |
| 517 | GLOBAL_STATE_CODE(); |
| 518 | |
| 519 | if (!drv) |
| 520 | return -ENOMEDIUM; |
| 521 | |
| 522 | bdrv_drain_all_begin(); |
| 523 | bdrv_graph_rdlock_main_loop(); |
| 524 | |
| 525 | backing_file_bs = bdrv_cow_bs(bs); |
| 526 | |
| 527 | if (!backing_file_bs) { |
| 528 | ret = -ENOTSUP; |
| 529 | goto out; |
| 530 | } |
| 531 | |
| 532 | if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) || |
| 533 | bdrv_op_is_blocked(backing_file_bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) |
| 534 | { |
| 535 | ret = -EBUSY; |
| 536 | goto out; |
| 537 | } |
| 538 | |
| 539 | ro = bdrv_is_read_only(backing_file_bs); |
| 540 | |
| 541 | if (ro) { |
| 542 | if (bdrv_reopen_set_read_only(backing_file_bs, false, NULL)) { |
| 543 | ret = -EACCES; |
| 544 | goto out; |
| 545 | } |
| 546 | } |
| 547 | |
| 548 | ctx = bdrv_get_aio_context(bs); |
| 549 | /* WRITE_UNCHANGED is required for bdrv_make_empty() */ |
| 550 | src = blk_new(ctx, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED, |
| 551 | BLK_PERM_ALL); |
| 552 | backing = blk_new(ctx, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL); |
| 553 | |
| 554 | /* We drained all nodes, but still make requests through BlockBackends */ |
| 555 | blk_set_disable_request_queuing(src, true); |
| 556 | blk_set_disable_request_queuing(backing, true); |
| 557 | |
| 558 | ret = blk_insert_bs(src, bs, &local_err); |
| 559 | if (ret < 0) { |
| 560 | error_report_err(local_err); |
| 561 | goto ro_cleanup; |
| 562 | } |
| 563 | |
| 564 | /* Insert commit_top block node above backing, so we can write to it */ |
| 565 | commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR, |
| 566 | &local_err); |
| 567 | if (commit_top_bs == NULL) { |
| 568 | error_report_err(local_err); |
| 569 | goto ro_cleanup; |
| 570 | } |
| 571 | |
| 572 | bdrv_graph_rdunlock_main_loop(); |
| 573 | |
| 574 | bdrv_graph_wrlock(); |
| 575 | bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort); |
| 576 | bdrv_set_backing_hd(bs, commit_top_bs, &error_abort); |
| 577 | bdrv_graph_wrunlock(); |
| 578 | |
| 579 | bdrv_graph_rdlock_main_loop(); |
| 580 | |
| 581 | ret = blk_insert_bs(backing, backing_file_bs, &local_err); |
| 582 | if (ret < 0) { |
| 583 | error_report_err(local_err); |
| 584 | goto ro_cleanup; |
| 585 | } |
| 586 | |
| 587 | length = blk_getlength(src); |
| 588 | if (length < 0) { |
| 589 | ret = length; |
| 590 | goto ro_cleanup; |
| 591 | } |
| 592 | |
| 593 | backing_length = blk_getlength(backing); |
| 594 | if (backing_length < 0) { |
| 595 | ret = backing_length; |
| 596 | goto ro_cleanup; |
| 597 | } |
| 598 | |
| 599 | /* If our top snapshot is larger than the backing file image, |
| 600 | * grow the backing file image if possible. If not possible, |
| 601 | * we must return an error */ |
| 602 | if (length > backing_length) { |
| 603 | ret = blk_truncate(backing, length, false, PREALLOC_MODE_OFF, 0, |
| 604 | &local_err); |
| 605 | if (ret < 0) { |
| 606 | error_report_err(local_err); |
| 607 | goto ro_cleanup; |
| 608 | } |
| 609 | } |
| 610 | |
| 611 | /* blk_try_blockalign() for src will choose an alignment that works for |
| 612 | * backing as well, so no need to compare the alignment manually. */ |
| 613 | buf = blk_try_blockalign(src, COMMIT_BUF_SIZE); |
| 614 | if (buf == NULL) { |
| 615 | ret = -ENOMEM; |
| 616 | goto ro_cleanup; |
| 617 | } |
| 618 | |
| 619 | for (offset = 0; offset < length; offset += n) { |
| 620 | ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n); |
| 621 | if (ret < 0) { |
| 622 | goto ro_cleanup; |
| 623 | } |
| 624 | if (ret) { |
| 625 | ret = blk_pread(src, offset, n, buf, 0); |
| 626 | if (ret < 0) { |
| 627 | goto ro_cleanup; |
| 628 | } |
| 629 | |
| 630 | ret = blk_pwrite(backing, offset, n, buf, 0); |
| 631 | if (ret < 0) { |
| 632 | goto ro_cleanup; |
| 633 | } |
| 634 | } |
| 635 | } |
| 636 | |
| 637 | ret = blk_make_empty(src, NULL); |
| 638 | /* Ignore -ENOTSUP */ |
| 639 | if (ret < 0 && ret != -ENOTSUP) { |
| 640 | goto ro_cleanup; |
| 641 | } |
| 642 | |
| 643 | blk_flush(src); |
| 644 | |
| 645 | /* |
| 646 | * Make sure all data we wrote to the backing device is actually |
| 647 | * stable on disk. |
| 648 | */ |
| 649 | blk_flush(backing); |
| 650 | |
| 651 | ret = 0; |
| 652 | ro_cleanup: |
| 653 | blk_unref(backing); |
| 654 | |
| 655 | bdrv_graph_rdunlock_main_loop(); |
| 656 | bdrv_graph_wrlock(); |
| 657 | if (bdrv_cow_bs(bs) != backing_file_bs) { |
| 658 | bdrv_set_backing_hd(bs, backing_file_bs, &error_abort); |
| 659 | } |
| 660 | bdrv_graph_wrunlock(); |
| 661 | bdrv_graph_rdlock_main_loop(); |
| 662 | bdrv_unref(commit_top_bs); |
| 663 | blk_unref(src); |
| 664 | |
| 665 | if (ro) { |
| 666 | /* ignoring error return here */ |
| 667 | bdrv_reopen_set_read_only(backing_file_bs, true, NULL); |
| 668 | } |
| 669 | |
| 670 | out: |
| 671 | bdrv_graph_rdunlock_main_loop(); |
| 672 | bdrv_drain_all_end(); |
| 673 | |
| 674 | return ret; |
| 675 | } |