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
  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=dirty-bitmap */
  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_DIRTY_BITMAP) {
 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) {
 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_DIRTY_BITMAP) {
 501         if (!sync_bitmap) {
 502             error_setg(errp, "must provide a valid bitmap name for "
 503                              "\"dirty-bitmap\" 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_DIRTY_BITMAP ?
 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 }