block/commit.c

   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_int.h"
  19 #include "block/blockjob_int.h"
  20 #include "qapi/error.h"
  21 #include "qapi/qmp/qerror.h"
  22 #include "qemu/ratelimit.h"
  23 #include "sysemu/block-backend.h"
  24
  25 enum {
  26     /*
  27      * Size of data buffer for populating the image file.  This should be large
  28      * enough to process multiple clusters in a single call, so that populating
  29      * contiguous regions of the image is efficient.
  30      */
  31     COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */
  32 };
  33
  34 #define SLICE_TIME 100000000ULL /* ns */
  35
  36 typedef struct CommitBlockJob {
  37     BlockJob common;
  38     RateLimit limit;
  39     BlockDriverState *active;
  40     BlockDriverState *commit_top_bs;
  41     BlockBackend *top;
  42     BlockBackend *base;
  43     BlockdevOnError on_error;
  44     int base_flags;
  45     int orig_overlay_flags;
  46     char *backing_file_str;
  47 } CommitBlockJob;
  48
  49 static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
  50                                         int64_t offset, uint64_t bytes,
  51                                         void *buf)
  52 {
  53     int ret = 0;
  54     QEMUIOVector qiov;
  55     struct iovec iov = {
  56         .iov_base = buf,
  57         .iov_len = bytes,
  58     };
  59
  60     assert(bytes < SIZE_MAX);
  61     qemu_iovec_init_external(&qiov, &iov, 1);
  62
  63     ret = blk_co_preadv(bs, offset, qiov.size, &qiov, 0);
  64     if (ret < 0) {
  65         return ret;
  66     }
  67
  68     ret = blk_co_pwritev(base, offset, qiov.size, &qiov, 0);
  69     if (ret < 0) {
  70         return ret;
  71     }
  72
  73     return 0;
  74 }
  75
  76 typedef struct {
  77     int ret;
  78 } CommitCompleteData;
  79
  80 static void commit_complete(BlockJob *job, void *opaque)
  81 {
  82     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
  83     CommitCompleteData *data = opaque;
  84     BlockDriverState *active = s->active;
  85     BlockDriverState *top = blk_bs(s->top);
  86     BlockDriverState *base = blk_bs(s->base);
  87     BlockDriverState *overlay_bs = bdrv_find_overlay(active, s->commit_top_bs);
  88     int ret = data->ret;
  89     bool remove_commit_top_bs = false;
  90
  91     /* Make sure overlay_bs and top stay around until bdrv_set_backing_hd() */
  92     bdrv_ref(top);
  93     if (overlay_bs) {
  94         bdrv_ref(overlay_bs);
  95     }
  96
  97     /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before
  98      * the normal backing chain can be restored. */
  99     blk_unref(s->base);
 100
 101     if (!block_job_is_cancelled(&s->common) && ret == 0) {
 102         /* success */
 103         ret = bdrv_drop_intermediate(active, s->commit_top_bs, base,
 104                                      s->backing_file_str);
 105     } else if (overlay_bs) {
 106         /* XXX Can (or should) we somehow keep 'consistent read' blocked even
 107          * after the failed/cancelled commit job is gone? If we already wrote
 108          * something to base, the intermediate images aren't valid any more. */
 109         remove_commit_top_bs = true;
 110     }
 111
 112     /* restore base open flags here if appropriate (e.g., change the base back
 113      * to r/o). These reopens do not need to be atomic, since we won't abort
 114      * even on failure here */
 115     if (s->base_flags != bdrv_get_flags(base)) {
 116         bdrv_reopen(base, s->base_flags, NULL);
 117     }
 118     if (overlay_bs && s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) {
 119         bdrv_reopen(overlay_bs, s->orig_overlay_flags, NULL);
 120     }
 121     g_free(s->backing_file_str);
 122     blk_unref(s->top);
 123
 124     /* If there is more than one reference to the job (e.g. if called from
 125      * block_job_finish_sync()), block_job_completed() won't free it and
 126      * therefore the blockers on the intermediate nodes remain. This would
 127      * cause bdrv_set_backing_hd() to fail. */
 128     block_job_remove_all_bdrv(job);
 129
 130     block_job_completed(&s->common, ret);
 131     g_free(data);
 132
 133     /* If bdrv_drop_intermediate() didn't already do that, remove the commit
 134      * filter driver from the backing chain. Do this as the final step so that
 135      * the 'consistent read' permission can be granted.  */
 136     if (remove_commit_top_bs) {
 137         bdrv_set_backing_hd(overlay_bs, top, &error_abort);
 138     }
 139
 140     bdrv_unref(overlay_bs);
 141     bdrv_unref(top);
 142 }
 143
 144 static void coroutine_fn commit_run(void *opaque)
 145 {
 146     CommitBlockJob *s = opaque;
 147     CommitCompleteData *data;
 148     int64_t offset;
 149     uint64_t delay_ns = 0;
 150     int ret = 0;
 151     int64_t n = 0; /* bytes */
 152     void *buf = NULL;
 153     int bytes_written = 0;
 154     int64_t base_len;
 155
 156     ret = s->common.len = blk_getlength(s->top);
 157
 158     if (s->common.len < 0) {
 159         goto out;
 160     }
 161
 162     ret = base_len = blk_getlength(s->base);
 163     if (base_len < 0) {
 164         goto out;
 165     }
 166
 167     if (base_len < s->common.len) {
 168         ret = blk_truncate(s->base, s->common.len, PREALLOC_MODE_OFF, NULL);
 169         if (ret) {
 170             goto out;
 171         }
 172     }
 173
 174     buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
 175
 176     for (offset = 0; offset < s->common.len; offset += n) {
 177         bool copy;
 178
 179         /* Note that even when no rate limit is applied we need to yield
 180          * with no pending I/O here so that bdrv_drain_all() returns.
 181          */
 182         block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
 183         if (block_job_is_cancelled(&s->common)) {
 184             break;
 185         }
 186         /* Copy if allocated above the base */
 187         ret = bdrv_is_allocated_above(blk_bs(s->top), blk_bs(s->base),
 188                                       offset, COMMIT_BUFFER_SIZE, &n);
 189         copy = (ret == 1);
 190         trace_commit_one_iteration(s, offset, n, ret);
 191         if (copy) {
 192             ret = commit_populate(s->top, s->base, offset, n, buf);
 193             bytes_written += n;
 194         }
 195         if (ret < 0) {
 196             BlockErrorAction action =
 197                 block_job_error_action(&s->common, false, s->on_error, -ret);
 198             if (action == BLOCK_ERROR_ACTION_REPORT) {
 199                 goto out;
 200             } else {
 201                 n = 0;
 202                 continue;
 203             }
 204         }
 205         /* Publish progress */
 206         s->common.offset += n;
 207
 208         if (copy && s->common.speed) {
 209             delay_ns = ratelimit_calculate_delay(&s->limit, n);
 210         }
 211     }
 212
 213     ret = 0;
 214
 215 out:
 216     qemu_vfree(buf);
 217
 218     data = g_malloc(sizeof(*data));
 219     data->ret = ret;
 220     block_job_defer_to_main_loop(&s->common, commit_complete, data);
 221 }
 222
 223 static void commit_set_speed(BlockJob *job, int64_t speed, Error **errp)
 224 {
 225     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
 226
 227     if (speed < 0) {
 228         error_setg(errp, QERR_INVALID_PARAMETER, "speed");
 229         return;
 230     }
 231     ratelimit_set_speed(&s->limit, speed, SLICE_TIME);
 232 }
 233
 234 static const BlockJobDriver commit_job_driver = {
 235     .instance_size = sizeof(CommitBlockJob),
 236     .job_type      = BLOCK_JOB_TYPE_COMMIT,
 237     .set_speed     = commit_set_speed,
 238     .start         = commit_run,
 239 };
 240
 241 static int coroutine_fn bdrv_commit_top_preadv(BlockDriverState *bs,
 242     uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
 243 {
 244     return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
 245 }
 246
 247 static void bdrv_commit_top_refresh_filename(BlockDriverState *bs, QDict *opts)
 248 {
 249     bdrv_refresh_filename(bs->backing->bs);
 250     pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
 251             bs->backing->bs->filename);
 252 }
 253
 254 static void bdrv_commit_top_close(BlockDriverState *bs)
 255 {
 256 }
 257
 258 static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c,
 259                                        const BdrvChildRole *role,
 260                                        uint64_t perm, uint64_t shared,
 261                                        uint64_t *nperm, uint64_t *nshared)
 262 {
 263     *nperm = 0;
 264     *nshared = BLK_PERM_ALL;
 265 }
 266
 267 /* Dummy node that provides consistent read to its users without requiring it
 268  * from its backing file and that allows writes on the backing file chain. */
 269 static BlockDriver bdrv_commit_top = {
 270     .format_name                = "commit_top",
 271     .bdrv_co_preadv             = bdrv_commit_top_preadv,
 272     .bdrv_co_get_block_status   = bdrv_co_get_block_status_from_backing,
 273     .bdrv_refresh_filename      = bdrv_commit_top_refresh_filename,
 274     .bdrv_close                 = bdrv_commit_top_close,
 275     .bdrv_child_perm            = bdrv_commit_top_child_perm,
 276 };
 277
 278 void commit_start(const char *job_id, BlockDriverState *bs,
 279                   BlockDriverState *base, BlockDriverState *top, int64_t speed,
 280                   BlockdevOnError on_error, const char *backing_file_str,
 281                   const char *filter_node_name, Error **errp)
 282 {
 283     CommitBlockJob *s;
 284     BlockReopenQueue *reopen_queue = NULL;
 285     int orig_overlay_flags;
 286     int orig_base_flags;
 287     BlockDriverState *iter;
 288     BlockDriverState *overlay_bs;
 289     BlockDriverState *commit_top_bs = NULL;
 290     Error *local_err = NULL;
 291     int ret;
 292
 293     assert(top != bs);
 294     if (top == base) {
 295         error_setg(errp, "Invalid files for merge: top and base are the same");
 296         return;
 297     }
 298
 299     overlay_bs = bdrv_find_overlay(bs, top);
 300
 301     if (overlay_bs == NULL) {
 302         error_setg(errp, "Could not find overlay image for %s:", top->filename);
 303         return;
 304     }
 305
 306     s = block_job_create(job_id, &commit_job_driver, bs, 0, BLK_PERM_ALL,
 307                          speed, BLOCK_JOB_DEFAULT, NULL, NULL, errp);
 308     if (!s) {
 309         return;
 310     }
 311
 312     orig_base_flags    = bdrv_get_flags(base);
 313     orig_overlay_flags = bdrv_get_flags(overlay_bs);
 314
 315     /* convert base & overlay_bs to r/w, if necessary */
 316     if (!(orig_base_flags & BDRV_O_RDWR)) {
 317         reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL,
 318                                          orig_base_flags | BDRV_O_RDWR);
 319     }
 320     if (!(orig_overlay_flags & BDRV_O_RDWR)) {
 321         reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs, NULL,
 322                                          orig_overlay_flags | BDRV_O_RDWR);
 323     }
 324     if (reopen_queue) {
 325         bdrv_reopen_multiple(bdrv_get_aio_context(bs), reopen_queue, &local_err);
 326         if (local_err != NULL) {
 327             error_propagate(errp, local_err);
 328             goto fail;
 329         }
 330     }
 331
 332     /* Insert commit_top block node above top, so we can block consistent read
 333      * on the backing chain below it */
 334     commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, filter_node_name, 0,
 335                                          errp);
 336     if (commit_top_bs == NULL) {
 337         goto fail;
 338     }
 339     if (!filter_node_name) {
 340         commit_top_bs->implicit = true;
 341     }
 342     commit_top_bs->total_sectors = top->total_sectors;
 343     bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(top));
 344
 345     bdrv_set_backing_hd(commit_top_bs, top, &local_err);
 346     if (local_err) {
 347         bdrv_unref(commit_top_bs);
 348         commit_top_bs = NULL;
 349         error_propagate(errp, local_err);
 350         goto fail;
 351     }
 352     bdrv_set_backing_hd(overlay_bs, commit_top_bs, &local_err);
 353     if (local_err) {
 354         bdrv_unref(commit_top_bs);
 355         commit_top_bs = NULL;
 356         error_propagate(errp, local_err);
 357         goto fail;
 358     }
 359
 360     s->commit_top_bs = commit_top_bs;
 361     bdrv_unref(commit_top_bs);
 362
 363     /* Block all nodes between top and base, because they will
 364      * disappear from the chain after this operation. */
 365     assert(bdrv_chain_contains(top, base));
 366     for (iter = top; iter != base; iter = backing_bs(iter)) {
 367         /* XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves
 368          * at s->base (if writes are blocked for a node, they are also blocked
 369          * for its backing file). The other options would be a second filter
 370          * driver above s->base. */
 371         ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
 372                                  BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE,
 373                                  errp);
 374         if (ret < 0) {
 375             goto fail;
 376         }
 377     }
 378
 379     ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp);
 380     if (ret < 0) {
 381         goto fail;
 382     }
 383
 384     /* overlay_bs must be blocked because it needs to be modified to
 385      * update the backing image string. */
 386     ret = block_job_add_bdrv(&s->common, "overlay of top", overlay_bs,
 387                              BLK_PERM_GRAPH_MOD, BLK_PERM_ALL, errp);
 388     if (ret < 0) {
 389         goto fail;
 390     }
 391
 392     s->base = blk_new(BLK_PERM_CONSISTENT_READ
 393                       | BLK_PERM_WRITE
 394                       | BLK_PERM_RESIZE,
 395                       BLK_PERM_CONSISTENT_READ
 396                       | BLK_PERM_GRAPH_MOD
 397                       | BLK_PERM_WRITE_UNCHANGED);
 398     ret = blk_insert_bs(s->base, base, errp);
 399     if (ret < 0) {
 400         goto fail;
 401     }
 402
 403     /* Required permissions are already taken with block_job_add_bdrv() */
 404     s->top = blk_new(0, BLK_PERM_ALL);
 405     ret = blk_insert_bs(s->top, top, errp);
 406     if (ret < 0) {
 407         goto fail;
 408     }
 409
 410     s->active = bs;
 411
 412     s->base_flags          = orig_base_flags;
 413     s->orig_overlay_flags  = orig_overlay_flags;
 414
 415     s->backing_file_str = g_strdup(backing_file_str);
 416
 417     s->on_error = on_error;
 418
 419     trace_commit_start(bs, base, top, s);
 420     block_job_start(&s->common);
 421     return;
 422
 423 fail:
 424     if (s->base) {
 425         blk_unref(s->base);
 426     }
 427     if (s->top) {
 428         blk_unref(s->top);
 429     }
 430     if (commit_top_bs) {
 431         bdrv_set_backing_hd(overlay_bs, top, &error_abort);
 432     }
 433     block_job_early_fail(&s->common);
 434 }
 435
 436
 437 #define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE)
 438
 439 /* commit COW file into the raw image */
 440 int bdrv_commit(BlockDriverState *bs)
 441 {
 442     BlockBackend *src, *backing;
 443     BlockDriverState *backing_file_bs = NULL;
 444     BlockDriverState *commit_top_bs = NULL;
 445     BlockDriver *drv = bs->drv;
 446     int64_t offset, length, backing_length;
 447     int ro, open_flags;
 448     int64_t n;
 449     int ret = 0;
 450     uint8_t *buf = NULL;
 451     Error *local_err = NULL;
 452
 453     if (!drv)
 454         return -ENOMEDIUM;
 455
 456     if (!bs->backing) {
 457         return -ENOTSUP;
 458     }
 459
 460     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
 461         bdrv_op_is_blocked(bs->backing->bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) {
 462         return -EBUSY;
 463     }
 464
 465     ro = bs->backing->bs->read_only;
 466     open_flags =  bs->backing->bs->open_flags;
 467
 468     if (ro) {
 469         if (bdrv_reopen(bs->backing->bs, open_flags | BDRV_O_RDWR, NULL)) {
 470             return -EACCES;
 471         }
 472     }
 473
 474     src = blk_new(BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL);
 475     backing = blk_new(BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
 476
 477     ret = blk_insert_bs(src, bs, &local_err);
 478     if (ret < 0) {
 479         error_report_err(local_err);
 480         goto ro_cleanup;
 481     }
 482
 483     /* Insert commit_top block node above backing, so we can write to it */
 484     backing_file_bs = backing_bs(bs);
 485
 486     commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR,
 487                                          &local_err);
 488     if (commit_top_bs == NULL) {
 489         error_report_err(local_err);
 490         goto ro_cleanup;
 491     }
 492     bdrv_set_aio_context(commit_top_bs, bdrv_get_aio_context(backing_file_bs));
 493
 494     bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort);
 495     bdrv_set_backing_hd(bs, commit_top_bs, &error_abort);
 496
 497     ret = blk_insert_bs(backing, backing_file_bs, &local_err);
 498     if (ret < 0) {
 499         error_report_err(local_err);
 500         goto ro_cleanup;
 501     }
 502
 503     length = blk_getlength(src);
 504     if (length < 0) {
 505         ret = length;
 506         goto ro_cleanup;
 507     }
 508
 509     backing_length = blk_getlength(backing);
 510     if (backing_length < 0) {
 511         ret = backing_length;
 512         goto ro_cleanup;
 513     }
 514
 515     /* If our top snapshot is larger than the backing file image,
 516      * grow the backing file image if possible.  If not possible,
 517      * we must return an error */
 518     if (length > backing_length) {
 519         ret = blk_truncate(backing, length, PREALLOC_MODE_OFF, &local_err);
 520         if (ret < 0) {
 521             error_report_err(local_err);
 522             goto ro_cleanup;
 523         }
 524     }
 525
 526     /* blk_try_blockalign() for src will choose an alignment that works for
 527      * backing as well, so no need to compare the alignment manually. */
 528     buf = blk_try_blockalign(src, COMMIT_BUF_SIZE);
 529     if (buf == NULL) {
 530         ret = -ENOMEM;
 531         goto ro_cleanup;
 532     }
 533
 534     for (offset = 0; offset < length; offset += n) {
 535         ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n);
 536         if (ret < 0) {
 537             goto ro_cleanup;
 538         }
 539         if (ret) {
 540             ret = blk_pread(src, offset, buf, n);
 541             if (ret < 0) {
 542                 goto ro_cleanup;
 543             }
 544
 545             ret = blk_pwrite(backing, offset, buf, n, 0);
 546             if (ret < 0) {
 547                 goto ro_cleanup;
 548             }
 549         }
 550     }
 551
 552     if (drv->bdrv_make_empty) {
 553         ret = drv->bdrv_make_empty(bs);
 554         if (ret < 0) {
 555             goto ro_cleanup;
 556         }
 557         blk_flush(src);
 558     }
 559
 560     /*
 561      * Make sure all data we wrote to the backing device is actually
 562      * stable on disk.
 563      */
 564     blk_flush(backing);
 565
 566     ret = 0;
 567 ro_cleanup:
 568     qemu_vfree(buf);
 569
 570     blk_unref(backing);
 571     if (backing_file_bs) {
 572         bdrv_set_backing_hd(bs, backing_file_bs, &error_abort);
 573     }
 574     bdrv_unref(commit_top_bs);
 575     blk_unref(src);
 576
 577     if (ro) {
 578         /* ignoring error return here */
 579         bdrv_reopen(bs->backing->bs, open_flags & ~BDRV_O_RDWR, NULL);
 580     }
 581
 582     return ret;
 583 }