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 <stdio.h> 15 #include <errno.h> 16 #include <unistd.h> 17 18 #include "trace.h" 19 #include "block/block.h" 20 #include "block/block_int.h" 21 #include "block/blockjob.h" 22 #include "qapi/qmp/qerror.h" 23 #include "qemu/ratelimit.h" 24 25 #define BACKUP_CLUSTER_BITS 16 26 #define BACKUP_CLUSTER_SIZE (1 << BACKUP_CLUSTER_BITS) 27 #define BACKUP_SECTORS_PER_CLUSTER (BACKUP_CLUSTER_SIZE / BDRV_SECTOR_SIZE) 28 29 #define SLICE_TIME 100000000ULL /* ns */ 30 31 typedef struct CowRequest { 32 int64_t start; 33 int64_t end; 34 QLIST_ENTRY(CowRequest) list; 35 CoQueue wait_queue; /* coroutines blocked on this request */ 36 } CowRequest; 37 38 typedef struct BackupBlockJob { 39 BlockJob common; 40 BlockDriverState *target; 41 /* bitmap for sync=incremental */ 42 BdrvDirtyBitmap *sync_bitmap; 43 MirrorSyncMode sync_mode; 44 RateLimit limit; 45 BlockdevOnError on_source_error; 46 BlockdevOnError on_target_error; 47 CoRwlock flush_rwlock; 48 uint64_t sectors_read; 49 HBitmap *bitmap; 50 QLIST_HEAD(, CowRequest) inflight_reqs; 51 } BackupBlockJob; 52 53 /* See if in-flight requests overlap and wait for them to complete */ 54 static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job, 55 int64_t start, 56 int64_t end) 57 { 58 CowRequest *req; 59 bool retry; 60 61 do { 62 retry = false; 63 QLIST_FOREACH(req, &job->inflight_reqs, list) { 64 if (end > req->start && start < req->end) { 65 qemu_co_queue_wait(&req->wait_queue); 66 retry = true; 67 break; 68 } 69 } 70 } while (retry); 71 } 72 73 /* Keep track of an in-flight request */ 74 static void cow_request_begin(CowRequest *req, BackupBlockJob *job, 75 int64_t start, int64_t end) 76 { 77 req->start = start; 78 req->end = end; 79 qemu_co_queue_init(&req->wait_queue); 80 QLIST_INSERT_HEAD(&job->inflight_reqs, req, list); 81 } 82 83 /* Forget about a completed request */ 84 static void cow_request_end(CowRequest *req) 85 { 86 QLIST_REMOVE(req, list); 87 qemu_co_queue_restart_all(&req->wait_queue); 88 } 89 90 static int coroutine_fn backup_do_cow(BlockDriverState *bs, 91 int64_t sector_num, int nb_sectors, 92 bool *error_is_read) 93 { 94 BackupBlockJob *job = (BackupBlockJob *)bs->job; 95 CowRequest cow_request; 96 struct iovec iov; 97 QEMUIOVector bounce_qiov; 98 void *bounce_buffer = NULL; 99 int ret = 0; 100 int64_t start, end; 101 int n; 102 103 qemu_co_rwlock_rdlock(&job->flush_rwlock); 104 105 start = sector_num / BACKUP_SECTORS_PER_CLUSTER; 106 end = DIV_ROUND_UP(sector_num + nb_sectors, BACKUP_SECTORS_PER_CLUSTER); 107 108 trace_backup_do_cow_enter(job, start, sector_num, nb_sectors); 109 110 wait_for_overlapping_requests(job, start, end); 111 cow_request_begin(&cow_request, job, start, end); 112 113 for (; start < end; start++) { 114 if (hbitmap_get(job->bitmap, start)) { 115 trace_backup_do_cow_skip(job, start); 116 continue; /* already copied */ 117 } 118 119 trace_backup_do_cow_process(job, start); 120 121 n = MIN(BACKUP_SECTORS_PER_CLUSTER, 122 job->common.len / BDRV_SECTOR_SIZE - 123 start * BACKUP_SECTORS_PER_CLUSTER); 124 125 if (!bounce_buffer) { 126 bounce_buffer = qemu_blockalign(bs, BACKUP_CLUSTER_SIZE); 127 } 128 iov.iov_base = bounce_buffer; 129 iov.iov_len = n * BDRV_SECTOR_SIZE; 130 qemu_iovec_init_external(&bounce_qiov, &iov, 1); 131 132 ret = bdrv_co_readv(bs, start * BACKUP_SECTORS_PER_CLUSTER, n, 133 &bounce_qiov); 134 if (ret < 0) { 135 trace_backup_do_cow_read_fail(job, start, ret); 136 if (error_is_read) { 137 *error_is_read = true; 138 } 139 goto out; 140 } 141 142 if (buffer_is_zero(iov.iov_base, iov.iov_len)) { 143 ret = bdrv_co_write_zeroes(job->target, 144 start * BACKUP_SECTORS_PER_CLUSTER, 145 n, BDRV_REQ_MAY_UNMAP); 146 } else { 147 ret = bdrv_co_writev(job->target, 148 start * BACKUP_SECTORS_PER_CLUSTER, n, 149 &bounce_qiov); 150 } 151 if (ret < 0) { 152 trace_backup_do_cow_write_fail(job, start, ret); 153 if (error_is_read) { 154 *error_is_read = false; 155 } 156 goto out; 157 } 158 159 hbitmap_set(job->bitmap, start, 1); 160 161 /* Publish progress, guest I/O counts as progress too. Note that the 162 * offset field is an opaque progress value, it is not a disk offset. 163 */ 164 job->sectors_read += n; 165 job->common.offset += n * BDRV_SECTOR_SIZE; 166 } 167 168 out: 169 if (bounce_buffer) { 170 qemu_vfree(bounce_buffer); 171 } 172 173 cow_request_end(&cow_request); 174 175 trace_backup_do_cow_return(job, sector_num, nb_sectors, ret); 176 177 qemu_co_rwlock_unlock(&job->flush_rwlock); 178 179 return ret; 180 } 181 182 static int coroutine_fn backup_before_write_notify( 183 NotifierWithReturn *notifier, 184 void *opaque) 185 { 186 BdrvTrackedRequest *req = opaque; 187 int64_t sector_num = req->offset >> BDRV_SECTOR_BITS; 188 int nb_sectors = req->bytes >> BDRV_SECTOR_BITS; 189 190 assert((req->offset & (BDRV_SECTOR_SIZE - 1)) == 0); 191 assert((req->bytes & (BDRV_SECTOR_SIZE - 1)) == 0); 192 193 return backup_do_cow(req->bs, sector_num, nb_sectors, NULL); 194 } 195 196 static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) 197 { 198 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 199 200 if (speed < 0) { 201 error_setg(errp, QERR_INVALID_PARAMETER, "speed"); 202 return; 203 } 204 ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME); 205 } 206 207 static void backup_iostatus_reset(BlockJob *job) 208 { 209 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 210 211 bdrv_iostatus_reset(s->target); 212 } 213 214 static const BlockJobDriver backup_job_driver = { 215 .instance_size = sizeof(BackupBlockJob), 216 .job_type = BLOCK_JOB_TYPE_BACKUP, 217 .set_speed = backup_set_speed, 218 .iostatus_reset = backup_iostatus_reset, 219 }; 220 221 static BlockErrorAction backup_error_action(BackupBlockJob *job, 222 bool read, int error) 223 { 224 if (read) { 225 return block_job_error_action(&job->common, job->common.bs, 226 job->on_source_error, true, error); 227 } else { 228 return block_job_error_action(&job->common, job->target, 229 job->on_target_error, false, error); 230 } 231 } 232 233 typedef struct { 234 int ret; 235 } BackupCompleteData; 236 237 static void backup_complete(BlockJob *job, void *opaque) 238 { 239 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 240 BackupCompleteData *data = opaque; 241 242 bdrv_unref(s->target); 243 244 block_job_completed(job, data->ret); 245 g_free(data); 246 } 247 248 static bool coroutine_fn yield_and_check(BackupBlockJob *job) 249 { 250 if (block_job_is_cancelled(&job->common)) { 251 return true; 252 } 253 254 /* we need to yield so that bdrv_drain_all() returns. 255 * (without, VM does not reboot) 256 */ 257 if (job->common.speed) { 258 uint64_t delay_ns = ratelimit_calculate_delay(&job->limit, 259 job->sectors_read); 260 job->sectors_read = 0; 261 block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, delay_ns); 262 } else { 263 block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, 0); 264 } 265 266 if (block_job_is_cancelled(&job->common)) { 267 return true; 268 } 269 270 return false; 271 } 272 273 static int coroutine_fn backup_run_incremental(BackupBlockJob *job) 274 { 275 bool error_is_read; 276 int ret = 0; 277 int clusters_per_iter; 278 uint32_t granularity; 279 int64_t sector; 280 int64_t cluster; 281 int64_t end; 282 int64_t last_cluster = -1; 283 BlockDriverState *bs = job->common.bs; 284 HBitmapIter hbi; 285 286 granularity = bdrv_dirty_bitmap_granularity(job->sync_bitmap); 287 clusters_per_iter = MAX((granularity / BACKUP_CLUSTER_SIZE), 1); 288 bdrv_dirty_iter_init(job->sync_bitmap, &hbi); 289 290 /* Find the next dirty sector(s) */ 291 while ((sector = hbitmap_iter_next(&hbi)) != -1) { 292 cluster = sector / BACKUP_SECTORS_PER_CLUSTER; 293 294 /* Fake progress updates for any clusters we skipped */ 295 if (cluster != last_cluster + 1) { 296 job->common.offset += ((cluster - last_cluster - 1) * 297 BACKUP_CLUSTER_SIZE); 298 } 299 300 for (end = cluster + clusters_per_iter; cluster < end; cluster++) { 301 do { 302 if (yield_and_check(job)) { 303 return ret; 304 } 305 ret = backup_do_cow(bs, cluster * BACKUP_SECTORS_PER_CLUSTER, 306 BACKUP_SECTORS_PER_CLUSTER, &error_is_read); 307 if ((ret < 0) && 308 backup_error_action(job, error_is_read, -ret) == 309 BLOCK_ERROR_ACTION_REPORT) { 310 return ret; 311 } 312 } while (ret < 0); 313 } 314 315 /* If the bitmap granularity is smaller than the backup granularity, 316 * we need to advance the iterator pointer to the next cluster. */ 317 if (granularity < BACKUP_CLUSTER_SIZE) { 318 bdrv_set_dirty_iter(&hbi, cluster * BACKUP_SECTORS_PER_CLUSTER); 319 } 320 321 last_cluster = cluster - 1; 322 } 323 324 /* Play some final catchup with the progress meter */ 325 end = DIV_ROUND_UP(job->common.len, BACKUP_CLUSTER_SIZE); 326 if (last_cluster + 1 < end) { 327 job->common.offset += ((end - last_cluster - 1) * BACKUP_CLUSTER_SIZE); 328 } 329 330 return ret; 331 } 332 333 static void coroutine_fn backup_run(void *opaque) 334 { 335 BackupBlockJob *job = opaque; 336 BackupCompleteData *data; 337 BlockDriverState *bs = job->common.bs; 338 BlockDriverState *target = job->target; 339 BlockdevOnError on_target_error = job->on_target_error; 340 NotifierWithReturn before_write = { 341 .notify = backup_before_write_notify, 342 }; 343 int64_t start, end; 344 int ret = 0; 345 346 QLIST_INIT(&job->inflight_reqs); 347 qemu_co_rwlock_init(&job->flush_rwlock); 348 349 start = 0; 350 end = DIV_ROUND_UP(job->common.len, BACKUP_CLUSTER_SIZE); 351 352 job->bitmap = hbitmap_alloc(end, 0); 353 354 bdrv_set_enable_write_cache(target, true); 355 bdrv_set_on_error(target, on_target_error, on_target_error); 356 bdrv_iostatus_enable(target); 357 358 bdrv_add_before_write_notifier(bs, &before_write); 359 360 if (job->sync_mode == MIRROR_SYNC_MODE_NONE) { 361 while (!block_job_is_cancelled(&job->common)) { 362 /* Yield until the job is cancelled. We just let our before_write 363 * notify callback service CoW requests. */ 364 job->common.busy = false; 365 qemu_coroutine_yield(); 366 job->common.busy = true; 367 } 368 } else if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { 369 ret = backup_run_incremental(job); 370 } else { 371 /* Both FULL and TOP SYNC_MODE's require copying.. */ 372 for (; start < end; start++) { 373 bool error_is_read; 374 if (yield_and_check(job)) { 375 break; 376 } 377 378 if (job->sync_mode == MIRROR_SYNC_MODE_TOP) { 379 int i, n; 380 int alloced = 0; 381 382 /* Check to see if these blocks are already in the 383 * backing file. */ 384 385 for (i = 0; i < BACKUP_SECTORS_PER_CLUSTER;) { 386 /* bdrv_is_allocated() only returns true/false based 387 * on the first set of sectors it comes across that 388 * are are all in the same state. 389 * For that reason we must verify each sector in the 390 * backup cluster length. We end up copying more than 391 * needed but at some point that is always the case. */ 392 alloced = 393 bdrv_is_allocated(bs, 394 start * BACKUP_SECTORS_PER_CLUSTER + i, 395 BACKUP_SECTORS_PER_CLUSTER - i, &n); 396 i += n; 397 398 if (alloced == 1 || n == 0) { 399 break; 400 } 401 } 402 403 /* If the above loop never found any sectors that are in 404 * the topmost image, skip this backup. */ 405 if (alloced == 0) { 406 continue; 407 } 408 } 409 /* FULL sync mode we copy the whole drive. */ 410 ret = backup_do_cow(bs, start * BACKUP_SECTORS_PER_CLUSTER, 411 BACKUP_SECTORS_PER_CLUSTER, &error_is_read); 412 if (ret < 0) { 413 /* Depending on error action, fail now or retry cluster */ 414 BlockErrorAction action = 415 backup_error_action(job, error_is_read, -ret); 416 if (action == BLOCK_ERROR_ACTION_REPORT) { 417 break; 418 } else { 419 start--; 420 continue; 421 } 422 } 423 } 424 } 425 426 notifier_with_return_remove(&before_write); 427 428 /* wait until pending backup_do_cow() calls have completed */ 429 qemu_co_rwlock_wrlock(&job->flush_rwlock); 430 qemu_co_rwlock_unlock(&job->flush_rwlock); 431 432 if (job->sync_bitmap) { 433 BdrvDirtyBitmap *bm; 434 if (ret < 0 || block_job_is_cancelled(&job->common)) { 435 /* Merge the successor back into the parent, delete nothing. */ 436 bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL); 437 assert(bm); 438 } else { 439 /* Everything is fine, delete this bitmap and install the backup. */ 440 bm = bdrv_dirty_bitmap_abdicate(bs, job->sync_bitmap, NULL); 441 assert(bm); 442 } 443 } 444 hbitmap_free(job->bitmap); 445 446 bdrv_iostatus_disable(target); 447 bdrv_op_unblock_all(target, job->common.blocker); 448 449 data = g_malloc(sizeof(*data)); 450 data->ret = ret; 451 block_job_defer_to_main_loop(&job->common, backup_complete, data); 452 } 453 454 void backup_start(BlockDriverState *bs, BlockDriverState *target, 455 int64_t speed, MirrorSyncMode sync_mode, 456 BdrvDirtyBitmap *sync_bitmap, 457 BlockdevOnError on_source_error, 458 BlockdevOnError on_target_error, 459 BlockCompletionFunc *cb, void *opaque, 460 Error **errp) 461 { 462 int64_t len; 463 464 assert(bs); 465 assert(target); 466 assert(cb); 467 468 if (bs == target) { 469 error_setg(errp, "Source and target cannot be the same"); 470 return; 471 } 472 473 if ((on_source_error == BLOCKDEV_ON_ERROR_STOP || 474 on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) && 475 !bdrv_iostatus_is_enabled(bs)) { 476 error_setg(errp, QERR_INVALID_PARAMETER, "on-source-error"); 477 return; 478 } 479 480 if (!bdrv_is_inserted(bs)) { 481 error_setg(errp, "Device is not inserted: %s", 482 bdrv_get_device_name(bs)); 483 return; 484 } 485 486 if (!bdrv_is_inserted(target)) { 487 error_setg(errp, "Device is not inserted: %s", 488 bdrv_get_device_name(target)); 489 return; 490 } 491 492 if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) { 493 return; 494 } 495 496 if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) { 497 return; 498 } 499 500 if (sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { 501 if (!sync_bitmap) { 502 error_setg(errp, "must provide a valid bitmap name for " 503 "\"incremental\" sync mode"); 504 return; 505 } 506 507 /* Create a new bitmap, and freeze/disable this one. */ 508 if (bdrv_dirty_bitmap_create_successor(bs, sync_bitmap, errp) < 0) { 509 return; 510 } 511 } else if (sync_bitmap) { 512 error_setg(errp, 513 "a sync_bitmap was provided to backup_run, " 514 "but received an incompatible sync_mode (%s)", 515 MirrorSyncMode_lookup[sync_mode]); 516 return; 517 } 518 519 len = bdrv_getlength(bs); 520 if (len < 0) { 521 error_setg_errno(errp, -len, "unable to get length for '%s'", 522 bdrv_get_device_name(bs)); 523 goto error; 524 } 525 526 BackupBlockJob *job = block_job_create(&backup_job_driver, bs, speed, 527 cb, opaque, errp); 528 if (!job) { 529 goto error; 530 } 531 532 bdrv_op_block_all(target, job->common.blocker); 533 534 job->on_source_error = on_source_error; 535 job->on_target_error = on_target_error; 536 job->target = target; 537 job->sync_mode = sync_mode; 538 job->sync_bitmap = sync_mode == MIRROR_SYNC_MODE_INCREMENTAL ? 539 sync_bitmap : NULL; 540 job->common.len = len; 541 job->common.co = qemu_coroutine_create(backup_run); 542 qemu_coroutine_enter(job->common.co, job); 543 return; 544 545 error: 546 if (sync_bitmap) { 547 bdrv_reclaim_dirty_bitmap(bs, sync_bitmap, NULL); 548 } 549 } 550