block/backup.c

   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 #include "sysemu/block-backend.h"
  25
  26 #define BACKUP_CLUSTER_BITS 16
  27 #define BACKUP_CLUSTER_SIZE (1 << BACKUP_CLUSTER_BITS)
  28 #define BACKUP_SECTORS_PER_CLUSTER (BACKUP_CLUSTER_SIZE / BDRV_SECTOR_SIZE)
  29
  30 #define SLICE_TIME 100000000ULL /* ns */
  31
  32 typedef struct CowRequest {
  33     int64_t start;
  34     int64_t end;
  35     QLIST_ENTRY(CowRequest) list;
  36     CoQueue wait_queue; /* coroutines blocked on this request */
  37 } CowRequest;
  38
  39 typedef struct BackupBlockJob {
  40     BlockJob common;
  41     BlockDriverState *target;
  42     /* bitmap for sync=incremental */
  43     BdrvDirtyBitmap *sync_bitmap;
  44     MirrorSyncMode sync_mode;
  45     RateLimit limit;
  46     BlockdevOnError on_source_error;
  47     BlockdevOnError on_target_error;
  48     CoRwlock flush_rwlock;
  49     uint64_t sectors_read;
  50     HBitmap *bitmap;
  51     QLIST_HEAD(, CowRequest) inflight_reqs;
  52 } BackupBlockJob;
  53
  54 /* See if in-flight requests overlap and wait for them to complete */
  55 static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job,
  56                                                        int64_t start,
  57                                                        int64_t end)
  58 {
  59     CowRequest *req;
  60     bool retry;
  61
  62     do {
  63         retry = false;
  64         QLIST_FOREACH(req, &job->inflight_reqs, list) {
  65             if (end > req->start && start < req->end) {
  66                 qemu_co_queue_wait(&req->wait_queue);
  67                 retry = true;
  68                 break;
  69             }
  70         }
  71     } while (retry);
  72 }
  73
  74 /* Keep track of an in-flight request */
  75 static void cow_request_begin(CowRequest *req, BackupBlockJob *job,
  76                                      int64_t start, int64_t end)
  77 {
  78     req->start = start;
  79     req->end = end;
  80     qemu_co_queue_init(&req->wait_queue);
  81     QLIST_INSERT_HEAD(&job->inflight_reqs, req, list);
  82 }
  83
  84 /* Forget about a completed request */
  85 static void cow_request_end(CowRequest *req)
  86 {
  87     QLIST_REMOVE(req, list);
  88     qemu_co_queue_restart_all(&req->wait_queue);
  89 }
  90
  91 static int coroutine_fn backup_do_cow(BlockDriverState *bs,
  92                                       int64_t sector_num, int nb_sectors,
  93                                       bool *error_is_read,
  94                                       bool is_write_notifier)
  95 {
  96     BackupBlockJob *job = (BackupBlockJob *)bs->job;
  97     CowRequest cow_request;
  98     struct iovec iov;
  99     QEMUIOVector bounce_qiov;
 100     void *bounce_buffer = NULL;
 101     int ret = 0;
 102     int64_t start, end;
 103     int n;
 104
 105     qemu_co_rwlock_rdlock(&job->flush_rwlock);
 106
 107     start = sector_num / BACKUP_SECTORS_PER_CLUSTER;
 108     end = DIV_ROUND_UP(sector_num + nb_sectors, BACKUP_SECTORS_PER_CLUSTER);
 109
 110     trace_backup_do_cow_enter(job, start, sector_num, nb_sectors);
 111
 112     wait_for_overlapping_requests(job, start, end);
 113     cow_request_begin(&cow_request, job, start, end);
 114
 115     for (; start < end; start++) {
 116         if (hbitmap_get(job->bitmap, start)) {
 117             trace_backup_do_cow_skip(job, start);
 118             continue; /* already copied */
 119         }
 120
 121         trace_backup_do_cow_process(job, start);
 122
 123         n = MIN(BACKUP_SECTORS_PER_CLUSTER,
 124                 job->common.len / BDRV_SECTOR_SIZE -
 125                 start * BACKUP_SECTORS_PER_CLUSTER);
 126
 127         if (!bounce_buffer) {
 128             bounce_buffer = qemu_blockalign(bs, BACKUP_CLUSTER_SIZE);
 129         }
 130         iov.iov_base = bounce_buffer;
 131         iov.iov_len = n * BDRV_SECTOR_SIZE;
 132         qemu_iovec_init_external(&bounce_qiov, &iov, 1);
 133
 134         if (is_write_notifier) {
 135             ret = bdrv_co_no_copy_on_readv(bs,
 136                                            start * BACKUP_SECTORS_PER_CLUSTER,
 137                                            n, &bounce_qiov);
 138         } else {
 139             ret = bdrv_co_readv(bs, start * BACKUP_SECTORS_PER_CLUSTER, n,
 140                                 &bounce_qiov);
 141         }
 142         if (ret < 0) {
 143             trace_backup_do_cow_read_fail(job, start, ret);
 144             if (error_is_read) {
 145                 *error_is_read = true;
 146             }
 147             goto out;
 148         }
 149
 150         if (buffer_is_zero(iov.iov_base, iov.iov_len)) {
 151             ret = bdrv_co_write_zeroes(job->target,
 152                                        start * BACKUP_SECTORS_PER_CLUSTER,
 153                                        n, BDRV_REQ_MAY_UNMAP);
 154         } else {
 155             ret = bdrv_co_writev(job->target,
 156                                  start * BACKUP_SECTORS_PER_CLUSTER, n,
 157                                  &bounce_qiov);
 158         }
 159         if (ret < 0) {
 160             trace_backup_do_cow_write_fail(job, start, ret);
 161             if (error_is_read) {
 162                 *error_is_read = false;
 163             }
 164             goto out;
 165         }
 166
 167         hbitmap_set(job->bitmap, start, 1);
 168
 169         /* Publish progress, guest I/O counts as progress too.  Note that the
 170          * offset field is an opaque progress value, it is not a disk offset.
 171          */
 172         job->sectors_read += n;
 173         job->common.offset += n * BDRV_SECTOR_SIZE;
 174     }
 175
 176 out:
 177     if (bounce_buffer) {
 178         qemu_vfree(bounce_buffer);
 179     }
 180
 181     cow_request_end(&cow_request);
 182
 183     trace_backup_do_cow_return(job, sector_num, nb_sectors, ret);
 184
 185     qemu_co_rwlock_unlock(&job->flush_rwlock);
 186
 187     return ret;
 188 }
 189
 190 static int coroutine_fn backup_before_write_notify(
 191         NotifierWithReturn *notifier,
 192         void *opaque)
 193 {
 194     BdrvTrackedRequest *req = opaque;
 195     int64_t sector_num = req->offset >> BDRV_SECTOR_BITS;
 196     int nb_sectors = req->bytes >> BDRV_SECTOR_BITS;
 197
 198     assert((req->offset & (BDRV_SECTOR_SIZE - 1)) == 0);
 199     assert((req->bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
 200
 201     return backup_do_cow(req->bs, sector_num, nb_sectors, NULL, true);
 202 }
 203
 204 static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp)
 205 {
 206     BackupBlockJob *s = container_of(job, BackupBlockJob, common);
 207
 208     if (speed < 0) {
 209         error_setg(errp, QERR_INVALID_PARAMETER, "speed");
 210         return;
 211     }
 212     ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
 213 }
 214
 215 static void backup_iostatus_reset(BlockJob *job)
 216 {
 217     BackupBlockJob *s = container_of(job, BackupBlockJob, common);
 218
 219     if (s->target->blk) {
 220         blk_iostatus_reset(s->target->blk);
 221     }
 222 }
 223
 224 static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret)
 225 {
 226     BdrvDirtyBitmap *bm;
 227     BlockDriverState *bs = job->common.bs;
 228
 229     if (ret < 0 || block_job_is_cancelled(&job->common)) {
 230         /* Merge the successor back into the parent, delete nothing. */
 231         bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL);
 232         assert(bm);
 233     } else {
 234         /* Everything is fine, delete this bitmap and install the backup. */
 235         bm = bdrv_dirty_bitmap_abdicate(bs, job->sync_bitmap, NULL);
 236         assert(bm);
 237     }
 238 }
 239
 240 static void backup_commit(BlockJob *job)
 241 {
 242     BackupBlockJob *s = container_of(job, BackupBlockJob, common);
 243     if (s->sync_bitmap) {
 244         backup_cleanup_sync_bitmap(s, 0);
 245     }
 246 }
 247
 248 static void backup_abort(BlockJob *job)
 249 {
 250     BackupBlockJob *s = container_of(job, BackupBlockJob, common);
 251     if (s->sync_bitmap) {
 252         backup_cleanup_sync_bitmap(s, -1);
 253     }
 254 }
 255
 256 static const BlockJobDriver backup_job_driver = {
 257     .instance_size  = sizeof(BackupBlockJob),
 258     .job_type       = BLOCK_JOB_TYPE_BACKUP,
 259     .set_speed      = backup_set_speed,
 260     .iostatus_reset = backup_iostatus_reset,
 261     .commit         = backup_commit,
 262     .abort          = backup_abort,
 263 };
 264
 265 static BlockErrorAction backup_error_action(BackupBlockJob *job,
 266                                             bool read, int error)
 267 {
 268     if (read) {
 269         return block_job_error_action(&job->common, job->common.bs,
 270                                       job->on_source_error, true, error);
 271     } else {
 272         return block_job_error_action(&job->common, job->target,
 273                                       job->on_target_error, false, error);
 274     }
 275 }
 276
 277 typedef struct {
 278     int ret;
 279 } BackupCompleteData;
 280
 281 static void backup_complete(BlockJob *job, void *opaque)
 282 {
 283     BackupBlockJob *s = container_of(job, BackupBlockJob, common);
 284     BackupCompleteData *data = opaque;
 285
 286     bdrv_unref(s->target);
 287
 288     block_job_completed(job, data->ret);
 289     g_free(data);
 290 }
 291
 292 static bool coroutine_fn yield_and_check(BackupBlockJob *job)
 293 {
 294     if (block_job_is_cancelled(&job->common)) {
 295         return true;
 296     }
 297
 298     /* we need to yield so that bdrv_drain_all() returns.
 299      * (without, VM does not reboot)
 300      */
 301     if (job->common.speed) {
 302         uint64_t delay_ns = ratelimit_calculate_delay(&job->limit,
 303                                                       job->sectors_read);
 304         job->sectors_read = 0;
 305         block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, delay_ns);
 306     } else {
 307         block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, 0);
 308     }
 309
 310     if (block_job_is_cancelled(&job->common)) {
 311         return true;
 312     }
 313
 314     return false;
 315 }
 316
 317 static int coroutine_fn backup_run_incremental(BackupBlockJob *job)
 318 {
 319     bool error_is_read;
 320     int ret = 0;
 321     int clusters_per_iter;
 322     uint32_t granularity;
 323     int64_t sector;
 324     int64_t cluster;
 325     int64_t end;
 326     int64_t last_cluster = -1;
 327     BlockDriverState *bs = job->common.bs;
 328     HBitmapIter hbi;
 329
 330     granularity = bdrv_dirty_bitmap_granularity(job->sync_bitmap);
 331     clusters_per_iter = MAX((granularity / BACKUP_CLUSTER_SIZE), 1);
 332     bdrv_dirty_iter_init(job->sync_bitmap, &hbi);
 333
 334     /* Find the next dirty sector(s) */
 335     while ((sector = hbitmap_iter_next(&hbi)) != -1) {
 336         cluster = sector / BACKUP_SECTORS_PER_CLUSTER;
 337
 338         /* Fake progress updates for any clusters we skipped */
 339         if (cluster != last_cluster + 1) {
 340             job->common.offset += ((cluster - last_cluster - 1) *
 341                                    BACKUP_CLUSTER_SIZE);
 342         }
 343
 344         for (end = cluster + clusters_per_iter; cluster < end; cluster++) {
 345             do {
 346                 if (yield_and_check(job)) {
 347                     return ret;
 348                 }
 349                 ret = backup_do_cow(bs, cluster * BACKUP_SECTORS_PER_CLUSTER,
 350                                     BACKUP_SECTORS_PER_CLUSTER, &error_is_read,
 351                                     false);
 352                 if ((ret < 0) &&
 353                     backup_error_action(job, error_is_read, -ret) ==
 354                     BLOCK_ERROR_ACTION_REPORT) {
 355                     return ret;
 356                 }
 357             } while (ret < 0);
 358         }
 359
 360         /* If the bitmap granularity is smaller than the backup granularity,
 361          * we need to advance the iterator pointer to the next cluster. */
 362         if (granularity < BACKUP_CLUSTER_SIZE) {
 363             bdrv_set_dirty_iter(&hbi, cluster * BACKUP_SECTORS_PER_CLUSTER);
 364         }
 365
 366         last_cluster = cluster - 1;
 367     }
 368
 369     /* Play some final catchup with the progress meter */
 370     end = DIV_ROUND_UP(job->common.len, BACKUP_CLUSTER_SIZE);
 371     if (last_cluster + 1 < end) {
 372         job->common.offset += ((end - last_cluster - 1) * BACKUP_CLUSTER_SIZE);
 373     }
 374
 375     return ret;
 376 }
 377
 378 static void coroutine_fn backup_run(void *opaque)
 379 {
 380     BackupBlockJob *job = opaque;
 381     BackupCompleteData *data;
 382     BlockDriverState *bs = job->common.bs;
 383     BlockDriverState *target = job->target;
 384     BlockdevOnError on_target_error = job->on_target_error;
 385     NotifierWithReturn before_write = {
 386         .notify = backup_before_write_notify,
 387     };
 388     int64_t start, end;
 389     int ret = 0;
 390
 391     QLIST_INIT(&job->inflight_reqs);
 392     qemu_co_rwlock_init(&job->flush_rwlock);
 393
 394     start = 0;
 395     end = DIV_ROUND_UP(job->common.len, BACKUP_CLUSTER_SIZE);
 396
 397     job->bitmap = hbitmap_alloc(end, 0);
 398
 399     bdrv_set_enable_write_cache(target, true);
 400     if (target->blk) {
 401         blk_set_on_error(target->blk, on_target_error, on_target_error);
 402         blk_iostatus_enable(target->blk);
 403     }
 404
 405     bdrv_add_before_write_notifier(bs, &before_write);
 406
 407     if (job->sync_mode == MIRROR_SYNC_MODE_NONE) {
 408         while (!block_job_is_cancelled(&job->common)) {
 409             /* Yield until the job is cancelled.  We just let our before_write
 410              * notify callback service CoW requests. */
 411             job->common.busy = false;
 412             qemu_coroutine_yield();
 413             job->common.busy = true;
 414         }
 415     } else if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
 416         ret = backup_run_incremental(job);
 417     } else {
 418         /* Both FULL and TOP SYNC_MODE's require copying.. */
 419         for (; start < end; start++) {
 420             bool error_is_read;
 421             if (yield_and_check(job)) {
 422                 break;
 423             }
 424
 425             if (job->sync_mode == MIRROR_SYNC_MODE_TOP) {
 426                 int i, n;
 427                 int alloced = 0;
 428
 429                 /* Check to see if these blocks are already in the
 430                  * backing file. */
 431
 432                 for (i = 0; i < BACKUP_SECTORS_PER_CLUSTER;) {
 433                     /* bdrv_is_allocated() only returns true/false based
 434                      * on the first set of sectors it comes across that
 435                      * are are all in the same state.
 436                      * For that reason we must verify each sector in the
 437                      * backup cluster length.  We end up copying more than
 438                      * needed but at some point that is always the case. */
 439                     alloced =
 440                         bdrv_is_allocated(bs,
 441                                 start * BACKUP_SECTORS_PER_CLUSTER + i,
 442                                 BACKUP_SECTORS_PER_CLUSTER - i, &n);
 443                     i += n;
 444
 445                     if (alloced == 1 || n == 0) {
 446                         break;
 447                     }
 448                 }
 449
 450                 /* If the above loop never found any sectors that are in
 451                  * the topmost image, skip this backup. */
 452                 if (alloced == 0) {
 453                     continue;
 454                 }
 455             }
 456             /* FULL sync mode we copy the whole drive. */
 457             ret = backup_do_cow(bs, start * BACKUP_SECTORS_PER_CLUSTER,
 458                     BACKUP_SECTORS_PER_CLUSTER, &error_is_read, false);
 459             if (ret < 0) {
 460                 /* Depending on error action, fail now or retry cluster */
 461                 BlockErrorAction action =
 462                     backup_error_action(job, error_is_read, -ret);
 463                 if (action == BLOCK_ERROR_ACTION_REPORT) {
 464                     break;
 465                 } else {
 466                     start--;
 467                     continue;
 468                 }
 469             }
 470         }
 471     }
 472
 473     notifier_with_return_remove(&before_write);
 474
 475     /* wait until pending backup_do_cow() calls have completed */
 476     qemu_co_rwlock_wrlock(&job->flush_rwlock);
 477     qemu_co_rwlock_unlock(&job->flush_rwlock);
 478     hbitmap_free(job->bitmap);
 479
 480     if (target->blk) {
 481         blk_iostatus_disable(target->blk);
 482     }
 483     bdrv_op_unblock_all(target, job->common.blocker);
 484
 485     data = g_malloc(sizeof(*data));
 486     data->ret = ret;
 487     block_job_defer_to_main_loop(&job->common, backup_complete, data);
 488 }
 489
 490 void backup_start(BlockDriverState *bs, BlockDriverState *target,
 491                   int64_t speed, MirrorSyncMode sync_mode,
 492                   BdrvDirtyBitmap *sync_bitmap,
 493                   BlockdevOnError on_source_error,
 494                   BlockdevOnError on_target_error,
 495                   BlockCompletionFunc *cb, void *opaque,
 496                   BlockJobTxn *txn, Error **errp)
 497 {
 498     int64_t len;
 499
 500     assert(bs);
 501     assert(target);
 502     assert(cb);
 503
 504     if (bs == target) {
 505         error_setg(errp, "Source and target cannot be the same");
 506         return;
 507     }
 508
 509     if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
 510          on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
 511         (!bs->blk || !blk_iostatus_is_enabled(bs->blk))) {
 512         error_setg(errp, QERR_INVALID_PARAMETER, "on-source-error");
 513         return;
 514     }
 515
 516     if (!bdrv_is_inserted(bs)) {
 517         error_setg(errp, "Device is not inserted: %s",
 518                    bdrv_get_device_name(bs));
 519         return;
 520     }
 521
 522     if (!bdrv_is_inserted(target)) {
 523         error_setg(errp, "Device is not inserted: %s",
 524                    bdrv_get_device_name(target));
 525         return;
 526     }
 527
 528     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
 529         return;
 530     }
 531
 532     if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) {
 533         return;
 534     }
 535
 536     if (sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) {
 537         if (!sync_bitmap) {
 538             error_setg(errp, "must provide a valid bitmap name for "
 539                              "\"incremental\" sync mode");
 540             return;
 541         }
 542
 543         /* Create a new bitmap, and freeze/disable this one. */
 544         if (bdrv_dirty_bitmap_create_successor(bs, sync_bitmap, errp) < 0) {
 545             return;
 546         }
 547     } else if (sync_bitmap) {
 548         error_setg(errp,
 549                    "a sync_bitmap was provided to backup_run, "
 550                    "but received an incompatible sync_mode (%s)",
 551                    MirrorSyncMode_lookup[sync_mode]);
 552         return;
 553     }
 554
 555     len = bdrv_getlength(bs);
 556     if (len < 0) {
 557         error_setg_errno(errp, -len, "unable to get length for '%s'",
 558                          bdrv_get_device_name(bs));
 559         goto error;
 560     }
 561
 562     BackupBlockJob *job = block_job_create(&backup_job_driver, bs, speed,
 563                                            cb, opaque, errp);
 564     if (!job) {
 565         goto error;
 566     }
 567
 568     bdrv_op_block_all(target, job->common.blocker);
 569
 570     job->on_source_error = on_source_error;
 571     job->on_target_error = on_target_error;
 572     job->target = target;
 573     job->sync_mode = sync_mode;
 574     job->sync_bitmap = sync_mode == MIRROR_SYNC_MODE_INCREMENTAL ?
 575                        sync_bitmap : NULL;
 576     job->common.len = len;
 577     job->common.co = qemu_coroutine_create(backup_run);
 578     block_job_txn_add_job(txn, &job->common);
 579     qemu_coroutine_enter(job->common.co, job);
 580     return;
 581
 582  error:
 583     if (sync_bitmap) {
 584         bdrv_reclaim_dirty_bitmap(bs, sync_bitmap, NULL);
 585     }
 586 }