1 /* 2 * QEMU backup 3 * 4 * Copyright (C) 2013 Proxmox Server Solutions 5 * 6 * Authors: 7 * Dietmar Maurer (dietmar@proxmox.com) 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 * 12 */ 13 14 #include "qemu/osdep.h" 15 16 #include "trace.h" 17 #include "block/block.h" 18 #include "block/block_int.h" 19 #include "block/blockjob.h" 20 #include "block/block_backup.h" 21 #include "qapi/error.h" 22 #include "qapi/qmp/qerror.h" 23 #include "qemu/ratelimit.h" 24 #include "qemu/cutils.h" 25 #include "sysemu/block-backend.h" 26 #include "qemu/bitmap.h" 27 28 #define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16) 29 #define SLICE_TIME 100000000ULL /* ns */ 30 31 typedef struct BackupBlockJob { 32 BlockJob common; 33 BlockBackend *target; 34 /* bitmap for sync=incremental */ 35 BdrvDirtyBitmap *sync_bitmap; 36 MirrorSyncMode sync_mode; 37 RateLimit limit; 38 BlockdevOnError on_source_error; 39 BlockdevOnError on_target_error; 40 CoRwlock flush_rwlock; 41 uint64_t sectors_read; 42 unsigned long *done_bitmap; 43 int64_t cluster_size; 44 bool compress; 45 NotifierWithReturn before_write; 46 QLIST_HEAD(, CowRequest) inflight_reqs; 47 } BackupBlockJob; 48 49 /* Size of a cluster in sectors, instead of bytes. */ 50 static inline int64_t cluster_size_sectors(BackupBlockJob *job) 51 { 52 return job->cluster_size / BDRV_SECTOR_SIZE; 53 } 54 55 /* See if in-flight requests overlap and wait for them to complete */ 56 static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job, 57 int64_t start, 58 int64_t end) 59 { 60 CowRequest *req; 61 bool retry; 62 63 do { 64 retry = false; 65 QLIST_FOREACH(req, &job->inflight_reqs, list) { 66 if (end > req->start && start < req->end) { 67 qemu_co_queue_wait(&req->wait_queue); 68 retry = true; 69 break; 70 } 71 } 72 } while (retry); 73 } 74 75 /* Keep track of an in-flight request */ 76 static void cow_request_begin(CowRequest *req, BackupBlockJob *job, 77 int64_t start, int64_t end) 78 { 79 req->start = start; 80 req->end = end; 81 qemu_co_queue_init(&req->wait_queue); 82 QLIST_INSERT_HEAD(&job->inflight_reqs, req, list); 83 } 84 85 /* Forget about a completed request */ 86 static void cow_request_end(CowRequest *req) 87 { 88 QLIST_REMOVE(req, list); 89 qemu_co_queue_restart_all(&req->wait_queue); 90 } 91 92 static int coroutine_fn backup_do_cow(BackupBlockJob *job, 93 int64_t sector_num, int nb_sectors, 94 bool *error_is_read, 95 bool is_write_notifier) 96 { 97 BlockBackend *blk = job->common.blk; 98 CowRequest cow_request; 99 struct iovec iov; 100 QEMUIOVector bounce_qiov; 101 void *bounce_buffer = NULL; 102 int ret = 0; 103 int64_t sectors_per_cluster = cluster_size_sectors(job); 104 int64_t start, end; 105 int n; 106 107 qemu_co_rwlock_rdlock(&job->flush_rwlock); 108 109 start = sector_num / sectors_per_cluster; 110 end = DIV_ROUND_UP(sector_num + nb_sectors, sectors_per_cluster); 111 112 trace_backup_do_cow_enter(job, start, sector_num, nb_sectors); 113 114 wait_for_overlapping_requests(job, start, end); 115 cow_request_begin(&cow_request, job, start, end); 116 117 for (; start < end; start++) { 118 if (test_bit(start, job->done_bitmap)) { 119 trace_backup_do_cow_skip(job, start); 120 continue; /* already copied */ 121 } 122 123 trace_backup_do_cow_process(job, start); 124 125 n = MIN(sectors_per_cluster, 126 job->common.len / BDRV_SECTOR_SIZE - 127 start * sectors_per_cluster); 128 129 if (!bounce_buffer) { 130 bounce_buffer = blk_blockalign(blk, job->cluster_size); 131 } 132 iov.iov_base = bounce_buffer; 133 iov.iov_len = n * BDRV_SECTOR_SIZE; 134 qemu_iovec_init_external(&bounce_qiov, &iov, 1); 135 136 ret = blk_co_preadv(blk, start * job->cluster_size, 137 bounce_qiov.size, &bounce_qiov, 138 is_write_notifier ? BDRV_REQ_NO_SERIALISING : 0); 139 if (ret < 0) { 140 trace_backup_do_cow_read_fail(job, start, ret); 141 if (error_is_read) { 142 *error_is_read = true; 143 } 144 goto out; 145 } 146 147 if (buffer_is_zero(iov.iov_base, iov.iov_len)) { 148 ret = blk_co_pwrite_zeroes(job->target, start * job->cluster_size, 149 bounce_qiov.size, BDRV_REQ_MAY_UNMAP); 150 } else { 151 ret = blk_co_pwritev(job->target, start * job->cluster_size, 152 bounce_qiov.size, &bounce_qiov, 153 job->compress ? BDRV_REQ_WRITE_COMPRESSED : 0); 154 } 155 if (ret < 0) { 156 trace_backup_do_cow_write_fail(job, start, ret); 157 if (error_is_read) { 158 *error_is_read = false; 159 } 160 goto out; 161 } 162 163 set_bit(start, job->done_bitmap); 164 165 /* Publish progress, guest I/O counts as progress too. Note that the 166 * offset field is an opaque progress value, it is not a disk offset. 167 */ 168 job->sectors_read += n; 169 job->common.offset += n * BDRV_SECTOR_SIZE; 170 } 171 172 out: 173 if (bounce_buffer) { 174 qemu_vfree(bounce_buffer); 175 } 176 177 cow_request_end(&cow_request); 178 179 trace_backup_do_cow_return(job, sector_num, nb_sectors, ret); 180 181 qemu_co_rwlock_unlock(&job->flush_rwlock); 182 183 return ret; 184 } 185 186 static int coroutine_fn backup_before_write_notify( 187 NotifierWithReturn *notifier, 188 void *opaque) 189 { 190 BackupBlockJob *job = container_of(notifier, BackupBlockJob, before_write); 191 BdrvTrackedRequest *req = opaque; 192 int64_t sector_num = req->offset >> BDRV_SECTOR_BITS; 193 int nb_sectors = req->bytes >> BDRV_SECTOR_BITS; 194 195 assert(req->bs == blk_bs(job->common.blk)); 196 assert((req->offset & (BDRV_SECTOR_SIZE - 1)) == 0); 197 assert((req->bytes & (BDRV_SECTOR_SIZE - 1)) == 0); 198 199 return backup_do_cow(job, sector_num, nb_sectors, NULL, true); 200 } 201 202 static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) 203 { 204 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 205 206 if (speed < 0) { 207 error_setg(errp, QERR_INVALID_PARAMETER, "speed"); 208 return; 209 } 210 ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME); 211 } 212 213 static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret) 214 { 215 BdrvDirtyBitmap *bm; 216 BlockDriverState *bs = blk_bs(job->common.blk); 217 218 if (ret < 0 || block_job_is_cancelled(&job->common)) { 219 /* Merge the successor back into the parent, delete nothing. */ 220 bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL); 221 assert(bm); 222 } else { 223 /* Everything is fine, delete this bitmap and install the backup. */ 224 bm = bdrv_dirty_bitmap_abdicate(bs, job->sync_bitmap, NULL); 225 assert(bm); 226 } 227 } 228 229 static void backup_commit(BlockJob *job) 230 { 231 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 232 if (s->sync_bitmap) { 233 backup_cleanup_sync_bitmap(s, 0); 234 } 235 } 236 237 static void backup_abort(BlockJob *job) 238 { 239 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 240 if (s->sync_bitmap) { 241 backup_cleanup_sync_bitmap(s, -1); 242 } 243 } 244 245 static void backup_attached_aio_context(BlockJob *job, AioContext *aio_context) 246 { 247 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 248 249 blk_set_aio_context(s->target, aio_context); 250 } 251 252 void backup_do_checkpoint(BlockJob *job, Error **errp) 253 { 254 BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common); 255 int64_t len; 256 257 assert(job->driver->job_type == BLOCK_JOB_TYPE_BACKUP); 258 259 if (backup_job->sync_mode != MIRROR_SYNC_MODE_NONE) { 260 error_setg(errp, "The backup job only supports block checkpoint in" 261 " sync=none mode"); 262 return; 263 } 264 265 len = DIV_ROUND_UP(backup_job->common.len, backup_job->cluster_size); 266 bitmap_zero(backup_job->done_bitmap, len); 267 } 268 269 void backup_wait_for_overlapping_requests(BlockJob *job, int64_t sector_num, 270 int nb_sectors) 271 { 272 BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common); 273 int64_t sectors_per_cluster = cluster_size_sectors(backup_job); 274 int64_t start, end; 275 276 assert(job->driver->job_type == BLOCK_JOB_TYPE_BACKUP); 277 278 start = sector_num / sectors_per_cluster; 279 end = DIV_ROUND_UP(sector_num + nb_sectors, sectors_per_cluster); 280 wait_for_overlapping_requests(backup_job, start, end); 281 } 282 283 void backup_cow_request_begin(CowRequest *req, BlockJob *job, 284 int64_t sector_num, 285 int nb_sectors) 286 { 287 BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common); 288 int64_t sectors_per_cluster = cluster_size_sectors(backup_job); 289 int64_t start, end; 290 291 assert(job->driver->job_type == BLOCK_JOB_TYPE_BACKUP); 292 293 start = sector_num / sectors_per_cluster; 294 end = DIV_ROUND_UP(sector_num + nb_sectors, sectors_per_cluster); 295 cow_request_begin(req, backup_job, start, end); 296 } 297 298 void backup_cow_request_end(CowRequest *req) 299 { 300 cow_request_end(req); 301 } 302 303 static const BlockJobDriver backup_job_driver = { 304 .instance_size = sizeof(BackupBlockJob), 305 .job_type = BLOCK_JOB_TYPE_BACKUP, 306 .set_speed = backup_set_speed, 307 .commit = backup_commit, 308 .abort = backup_abort, 309 .attached_aio_context = backup_attached_aio_context, 310 }; 311 312 static BlockErrorAction backup_error_action(BackupBlockJob *job, 313 bool read, int error) 314 { 315 if (read) { 316 return block_job_error_action(&job->common, job->on_source_error, 317 true, error); 318 } else { 319 return block_job_error_action(&job->common, job->on_target_error, 320 false, error); 321 } 322 } 323 324 typedef struct { 325 int ret; 326 } BackupCompleteData; 327 328 static void backup_complete(BlockJob *job, void *opaque) 329 { 330 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 331 BackupCompleteData *data = opaque; 332 333 blk_unref(s->target); 334 335 block_job_completed(job, data->ret); 336 g_free(data); 337 } 338 339 static bool coroutine_fn yield_and_check(BackupBlockJob *job) 340 { 341 if (block_job_is_cancelled(&job->common)) { 342 return true; 343 } 344 345 /* we need to yield so that bdrv_drain_all() returns. 346 * (without, VM does not reboot) 347 */ 348 if (job->common.speed) { 349 uint64_t delay_ns = ratelimit_calculate_delay(&job->limit, 350 job->sectors_read); 351 job->sectors_read = 0; 352 block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, delay_ns); 353 } else { 354 block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, 0); 355 } 356 357 if (block_job_is_cancelled(&job->common)) { 358 return true; 359 } 360 361 return false; 362 } 363 364 static int coroutine_fn backup_run_incremental(BackupBlockJob *job) 365 { 366 bool error_is_read; 367 int ret = 0; 368 int clusters_per_iter; 369 uint32_t granularity; 370 int64_t sector; 371 int64_t cluster; 372 int64_t end; 373 int64_t last_cluster = -1; 374 int64_t sectors_per_cluster = cluster_size_sectors(job); 375 BdrvDirtyBitmapIter *dbi; 376 377 granularity = bdrv_dirty_bitmap_granularity(job->sync_bitmap); 378 clusters_per_iter = MAX((granularity / job->cluster_size), 1); 379 dbi = bdrv_dirty_iter_new(job->sync_bitmap, 0); 380 381 /* Find the next dirty sector(s) */ 382 while ((sector = bdrv_dirty_iter_next(dbi)) != -1) { 383 cluster = sector / sectors_per_cluster; 384 385 /* Fake progress updates for any clusters we skipped */ 386 if (cluster != last_cluster + 1) { 387 job->common.offset += ((cluster - last_cluster - 1) * 388 job->cluster_size); 389 } 390 391 for (end = cluster + clusters_per_iter; cluster < end; cluster++) { 392 do { 393 if (yield_and_check(job)) { 394 goto out; 395 } 396 ret = backup_do_cow(job, cluster * sectors_per_cluster, 397 sectors_per_cluster, &error_is_read, 398 false); 399 if ((ret < 0) && 400 backup_error_action(job, error_is_read, -ret) == 401 BLOCK_ERROR_ACTION_REPORT) { 402 goto out; 403 } 404 } while (ret < 0); 405 } 406 407 /* If the bitmap granularity is smaller than the backup granularity, 408 * we need to advance the iterator pointer to the next cluster. */ 409 if (granularity < job->cluster_size) { 410 bdrv_set_dirty_iter(dbi, cluster * sectors_per_cluster); 411 } 412 413 last_cluster = cluster - 1; 414 } 415 416 /* Play some final catchup with the progress meter */ 417 end = DIV_ROUND_UP(job->common.len, job->cluster_size); 418 if (last_cluster + 1 < end) { 419 job->common.offset += ((end - last_cluster - 1) * job->cluster_size); 420 } 421 422 out: 423 bdrv_dirty_iter_free(dbi); 424 return ret; 425 } 426 427 static void coroutine_fn backup_run(void *opaque) 428 { 429 BackupBlockJob *job = opaque; 430 BackupCompleteData *data; 431 BlockDriverState *bs = blk_bs(job->common.blk); 432 BlockBackend *target = job->target; 433 int64_t start, end; 434 int64_t sectors_per_cluster = cluster_size_sectors(job); 435 int ret = 0; 436 437 QLIST_INIT(&job->inflight_reqs); 438 qemu_co_rwlock_init(&job->flush_rwlock); 439 440 start = 0; 441 end = DIV_ROUND_UP(job->common.len, job->cluster_size); 442 443 job->done_bitmap = bitmap_new(end); 444 445 job->before_write.notify = backup_before_write_notify; 446 bdrv_add_before_write_notifier(bs, &job->before_write); 447 448 if (job->sync_mode == MIRROR_SYNC_MODE_NONE) { 449 while (!block_job_is_cancelled(&job->common)) { 450 /* Yield until the job is cancelled. We just let our before_write 451 * notify callback service CoW requests. */ 452 block_job_yield(&job->common); 453 } 454 } else if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { 455 ret = backup_run_incremental(job); 456 } else { 457 /* Both FULL and TOP SYNC_MODE's require copying.. */ 458 for (; start < end; start++) { 459 bool error_is_read; 460 if (yield_and_check(job)) { 461 break; 462 } 463 464 if (job->sync_mode == MIRROR_SYNC_MODE_TOP) { 465 int i, n; 466 int alloced = 0; 467 468 /* Check to see if these blocks are already in the 469 * backing file. */ 470 471 for (i = 0; i < sectors_per_cluster;) { 472 /* bdrv_is_allocated() only returns true/false based 473 * on the first set of sectors it comes across that 474 * are are all in the same state. 475 * For that reason we must verify each sector in the 476 * backup cluster length. We end up copying more than 477 * needed but at some point that is always the case. */ 478 alloced = 479 bdrv_is_allocated(bs, 480 start * sectors_per_cluster + i, 481 sectors_per_cluster - i, &n); 482 i += n; 483 484 if (alloced == 1 || n == 0) { 485 break; 486 } 487 } 488 489 /* If the above loop never found any sectors that are in 490 * the topmost image, skip this backup. */ 491 if (alloced == 0) { 492 continue; 493 } 494 } 495 /* FULL sync mode we copy the whole drive. */ 496 ret = backup_do_cow(job, start * sectors_per_cluster, 497 sectors_per_cluster, &error_is_read, false); 498 if (ret < 0) { 499 /* Depending on error action, fail now or retry cluster */ 500 BlockErrorAction action = 501 backup_error_action(job, error_is_read, -ret); 502 if (action == BLOCK_ERROR_ACTION_REPORT) { 503 break; 504 } else { 505 start--; 506 continue; 507 } 508 } 509 } 510 } 511 512 notifier_with_return_remove(&job->before_write); 513 514 /* wait until pending backup_do_cow() calls have completed */ 515 qemu_co_rwlock_wrlock(&job->flush_rwlock); 516 qemu_co_rwlock_unlock(&job->flush_rwlock); 517 g_free(job->done_bitmap); 518 519 bdrv_op_unblock_all(blk_bs(target), job->common.blocker); 520 521 data = g_malloc(sizeof(*data)); 522 data->ret = ret; 523 block_job_defer_to_main_loop(&job->common, backup_complete, data); 524 } 525 526 void backup_start(const char *job_id, BlockDriverState *bs, 527 BlockDriverState *target, int64_t speed, 528 MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap, 529 bool compress, 530 BlockdevOnError on_source_error, 531 BlockdevOnError on_target_error, 532 BlockCompletionFunc *cb, void *opaque, 533 BlockJobTxn *txn, Error **errp) 534 { 535 int64_t len; 536 BlockDriverInfo bdi; 537 BackupBlockJob *job = NULL; 538 int ret; 539 540 assert(bs); 541 assert(target); 542 543 if (bs == target) { 544 error_setg(errp, "Source and target cannot be the same"); 545 return; 546 } 547 548 if (!bdrv_is_inserted(bs)) { 549 error_setg(errp, "Device is not inserted: %s", 550 bdrv_get_device_name(bs)); 551 return; 552 } 553 554 if (!bdrv_is_inserted(target)) { 555 error_setg(errp, "Device is not inserted: %s", 556 bdrv_get_device_name(target)); 557 return; 558 } 559 560 if (compress && target->drv->bdrv_co_pwritev_compressed == NULL) { 561 error_setg(errp, "Compression is not supported for this drive %s", 562 bdrv_get_device_name(target)); 563 return; 564 } 565 566 if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) { 567 return; 568 } 569 570 if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) { 571 return; 572 } 573 574 if (sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { 575 if (!sync_bitmap) { 576 error_setg(errp, "must provide a valid bitmap name for " 577 "\"incremental\" sync mode"); 578 return; 579 } 580 581 /* Create a new bitmap, and freeze/disable this one. */ 582 if (bdrv_dirty_bitmap_create_successor(bs, sync_bitmap, errp) < 0) { 583 return; 584 } 585 } else if (sync_bitmap) { 586 error_setg(errp, 587 "a sync_bitmap was provided to backup_run, " 588 "but received an incompatible sync_mode (%s)", 589 MirrorSyncMode_lookup[sync_mode]); 590 return; 591 } 592 593 len = bdrv_getlength(bs); 594 if (len < 0) { 595 error_setg_errno(errp, -len, "unable to get length for '%s'", 596 bdrv_get_device_name(bs)); 597 goto error; 598 } 599 600 job = block_job_create(job_id, &backup_job_driver, bs, speed, 601 cb, opaque, errp); 602 if (!job) { 603 goto error; 604 } 605 606 job->target = blk_new(); 607 blk_insert_bs(job->target, target); 608 609 job->on_source_error = on_source_error; 610 job->on_target_error = on_target_error; 611 job->sync_mode = sync_mode; 612 job->sync_bitmap = sync_mode == MIRROR_SYNC_MODE_INCREMENTAL ? 613 sync_bitmap : NULL; 614 job->compress = compress; 615 616 /* If there is no backing file on the target, we cannot rely on COW if our 617 * backup cluster size is smaller than the target cluster size. Even for 618 * targets with a backing file, try to avoid COW if possible. */ 619 ret = bdrv_get_info(target, &bdi); 620 if (ret < 0 && !target->backing) { 621 error_setg_errno(errp, -ret, 622 "Couldn't determine the cluster size of the target image, " 623 "which has no backing file"); 624 error_append_hint(errp, 625 "Aborting, since this may create an unusable destination image\n"); 626 goto error; 627 } else if (ret < 0 && target->backing) { 628 /* Not fatal; just trudge on ahead. */ 629 job->cluster_size = BACKUP_CLUSTER_SIZE_DEFAULT; 630 } else { 631 job->cluster_size = MAX(BACKUP_CLUSTER_SIZE_DEFAULT, bdi.cluster_size); 632 } 633 634 bdrv_op_block_all(target, job->common.blocker); 635 job->common.len = len; 636 job->common.co = qemu_coroutine_create(backup_run, job); 637 block_job_txn_add_job(txn, &job->common); 638 qemu_coroutine_enter(job->common.co); 639 return; 640 641 error: 642 if (sync_bitmap) { 643 bdrv_reclaim_dirty_bitmap(bs, sync_bitmap, NULL); 644 } 645 if (job) { 646 blk_unref(job->target); 647 block_job_unref(&job->common); 648 } 649 } 650