xref: /openbmc/qemu/block/backup.c (revision 5983021e)
1  /*
2   * QEMU backup
3   *
4   * Copyright (C) 2013 Proxmox Server Solutions
5   * Copyright (c) 2019 Virtuozzo International GmbH.
6   *
7   * Authors:
8   *  Dietmar Maurer (dietmar@proxmox.com)
9   *
10   * This work is licensed under the terms of the GNU GPL, version 2 or later.
11   * See the COPYING file in the top-level directory.
12   *
13   */
14  
15  #include "qemu/osdep.h"
16  
17  #include "trace.h"
18  #include "block/block.h"
19  #include "block/block_int.h"
20  #include "block/blockjob_int.h"
21  #include "block/block_backup.h"
22  #include "block/block-copy.h"
23  #include "qapi/error.h"
24  #include "qapi/qmp/qerror.h"
25  #include "qemu/ratelimit.h"
26  #include "qemu/cutils.h"
27  #include "sysemu/block-backend.h"
28  #include "qemu/bitmap.h"
29  #include "qemu/error-report.h"
30  
31  #include "block/backup-top.h"
32  
33  #define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16)
34  
35  typedef struct BackupBlockJob {
36      BlockJob common;
37      BlockDriverState *backup_top;
38      BlockDriverState *source_bs;
39  
40      BdrvDirtyBitmap *sync_bitmap;
41  
42      MirrorSyncMode sync_mode;
43      BitmapSyncMode bitmap_mode;
44      BlockdevOnError on_source_error;
45      BlockdevOnError on_target_error;
46      uint64_t len;
47      uint64_t bytes_read;
48      int64_t cluster_size;
49  
50      BlockCopyState *bcs;
51  } BackupBlockJob;
52  
53  static const BlockJobDriver backup_job_driver;
54  
55  static void backup_progress_bytes_callback(int64_t bytes, void *opaque)
56  {
57      BackupBlockJob *s = opaque;
58  
59      s->bytes_read += bytes;
60  }
61  
62  static int coroutine_fn backup_do_cow(BackupBlockJob *job,
63                                        int64_t offset, uint64_t bytes,
64                                        bool *error_is_read)
65  {
66      int ret = 0;
67      int64_t start, end; /* bytes */
68  
69      start = QEMU_ALIGN_DOWN(offset, job->cluster_size);
70      end = QEMU_ALIGN_UP(bytes + offset, job->cluster_size);
71  
72      trace_backup_do_cow_enter(job, start, offset, bytes);
73  
74      ret = block_copy(job->bcs, start, end - start, error_is_read);
75  
76      trace_backup_do_cow_return(job, offset, bytes, ret);
77  
78      return ret;
79  }
80  
81  static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret)
82  {
83      BdrvDirtyBitmap *bm;
84      bool sync = (((ret == 0) || (job->bitmap_mode == BITMAP_SYNC_MODE_ALWAYS)) \
85                   && (job->bitmap_mode != BITMAP_SYNC_MODE_NEVER));
86  
87      if (sync) {
88          /*
89           * We succeeded, or we always intended to sync the bitmap.
90           * Delete this bitmap and install the child.
91           */
92          bm = bdrv_dirty_bitmap_abdicate(job->sync_bitmap, NULL);
93      } else {
94          /*
95           * We failed, or we never intended to sync the bitmap anyway.
96           * Merge the successor back into the parent, keeping all data.
97           */
98          bm = bdrv_reclaim_dirty_bitmap(job->sync_bitmap, NULL);
99      }
100  
101      assert(bm);
102  
103      if (ret < 0 && job->bitmap_mode == BITMAP_SYNC_MODE_ALWAYS) {
104          /* If we failed and synced, merge in the bits we didn't copy: */
105          bdrv_dirty_bitmap_merge_internal(bm, block_copy_dirty_bitmap(job->bcs),
106                                           NULL, true);
107      }
108  }
109  
110  static void backup_commit(Job *job)
111  {
112      BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
113      if (s->sync_bitmap) {
114          backup_cleanup_sync_bitmap(s, 0);
115      }
116  }
117  
118  static void backup_abort(Job *job)
119  {
120      BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
121      if (s->sync_bitmap) {
122          backup_cleanup_sync_bitmap(s, -1);
123      }
124  }
125  
126  static void backup_clean(Job *job)
127  {
128      BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
129      bdrv_backup_top_drop(s->backup_top);
130  }
131  
132  void backup_do_checkpoint(BlockJob *job, Error **errp)
133  {
134      BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common);
135  
136      assert(block_job_driver(job) == &backup_job_driver);
137  
138      if (backup_job->sync_mode != MIRROR_SYNC_MODE_NONE) {
139          error_setg(errp, "The backup job only supports block checkpoint in"
140                     " sync=none mode");
141          return;
142      }
143  
144      bdrv_set_dirty_bitmap(block_copy_dirty_bitmap(backup_job->bcs), 0,
145                            backup_job->len);
146  }
147  
148  static BlockErrorAction backup_error_action(BackupBlockJob *job,
149                                              bool read, int error)
150  {
151      if (read) {
152          return block_job_error_action(&job->common, job->on_source_error,
153                                        true, error);
154      } else {
155          return block_job_error_action(&job->common, job->on_target_error,
156                                        false, error);
157      }
158  }
159  
160  static bool coroutine_fn yield_and_check(BackupBlockJob *job)
161  {
162      uint64_t delay_ns;
163  
164      if (job_is_cancelled(&job->common.job)) {
165          return true;
166      }
167  
168      /*
169       * We need to yield even for delay_ns = 0 so that bdrv_drain_all() can
170       * return. Without a yield, the VM would not reboot.
171       */
172      delay_ns = block_job_ratelimit_get_delay(&job->common, job->bytes_read);
173      job->bytes_read = 0;
174      job_sleep_ns(&job->common.job, delay_ns);
175  
176      if (job_is_cancelled(&job->common.job)) {
177          return true;
178      }
179  
180      return false;
181  }
182  
183  static int coroutine_fn backup_loop(BackupBlockJob *job)
184  {
185      bool error_is_read;
186      int64_t offset;
187      BdrvDirtyBitmapIter *bdbi;
188      int ret = 0;
189  
190      bdbi = bdrv_dirty_iter_new(block_copy_dirty_bitmap(job->bcs));
191      while ((offset = bdrv_dirty_iter_next(bdbi)) != -1) {
192          do {
193              if (yield_and_check(job)) {
194                  goto out;
195              }
196              ret = backup_do_cow(job, offset, job->cluster_size, &error_is_read);
197              if (ret < 0 && backup_error_action(job, error_is_read, -ret) ==
198                             BLOCK_ERROR_ACTION_REPORT)
199              {
200                  goto out;
201              }
202          } while (ret < 0);
203      }
204  
205   out:
206      bdrv_dirty_iter_free(bdbi);
207      return ret;
208  }
209  
210  static void backup_init_bcs_bitmap(BackupBlockJob *job)
211  {
212      bool ret;
213      uint64_t estimate;
214      BdrvDirtyBitmap *bcs_bitmap = block_copy_dirty_bitmap(job->bcs);
215  
216      if (job->sync_mode == MIRROR_SYNC_MODE_BITMAP) {
217          ret = bdrv_dirty_bitmap_merge_internal(bcs_bitmap, job->sync_bitmap,
218                                                 NULL, true);
219          assert(ret);
220      } else {
221          if (job->sync_mode == MIRROR_SYNC_MODE_TOP) {
222              /*
223               * We can't hog the coroutine to initialize this thoroughly.
224               * Set a flag and resume work when we are able to yield safely.
225               */
226              block_copy_set_skip_unallocated(job->bcs, true);
227          }
228          bdrv_set_dirty_bitmap(bcs_bitmap, 0, job->len);
229      }
230  
231      estimate = bdrv_get_dirty_count(bcs_bitmap);
232      job_progress_set_remaining(&job->common.job, estimate);
233  }
234  
235  static int coroutine_fn backup_run(Job *job, Error **errp)
236  {
237      BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
238      int ret = 0;
239  
240      backup_init_bcs_bitmap(s);
241  
242      if (s->sync_mode == MIRROR_SYNC_MODE_TOP) {
243          int64_t offset = 0;
244          int64_t count;
245  
246          for (offset = 0; offset < s->len; ) {
247              if (yield_and_check(s)) {
248                  ret = -ECANCELED;
249                  goto out;
250              }
251  
252              ret = block_copy_reset_unallocated(s->bcs, offset, &count);
253              if (ret < 0) {
254                  goto out;
255              }
256  
257              offset += count;
258          }
259          block_copy_set_skip_unallocated(s->bcs, false);
260      }
261  
262      if (s->sync_mode == MIRROR_SYNC_MODE_NONE) {
263          /*
264           * All bits are set in bcs bitmap to allow any cluster to be copied.
265           * This does not actually require them to be copied.
266           */
267          while (!job_is_cancelled(job)) {
268              /*
269               * Yield until the job is cancelled.  We just let our before_write
270               * notify callback service CoW requests.
271               */
272              job_yield(job);
273          }
274      } else {
275          ret = backup_loop(s);
276      }
277  
278   out:
279      return ret;
280  }
281  
282  static const BlockJobDriver backup_job_driver = {
283      .job_driver = {
284          .instance_size          = sizeof(BackupBlockJob),
285          .job_type               = JOB_TYPE_BACKUP,
286          .free                   = block_job_free,
287          .user_resume            = block_job_user_resume,
288          .run                    = backup_run,
289          .commit                 = backup_commit,
290          .abort                  = backup_abort,
291          .clean                  = backup_clean,
292      }
293  };
294  
295  static int64_t backup_calculate_cluster_size(BlockDriverState *target,
296                                               Error **errp)
297  {
298      int ret;
299      BlockDriverInfo bdi;
300      bool target_does_cow = bdrv_backing_chain_next(target);
301  
302      /*
303       * If there is no backing file on the target, we cannot rely on COW if our
304       * backup cluster size is smaller than the target cluster size. Even for
305       * targets with a backing file, try to avoid COW if possible.
306       */
307      ret = bdrv_get_info(target, &bdi);
308      if (ret == -ENOTSUP && !target_does_cow) {
309          /* Cluster size is not defined */
310          warn_report("The target block device doesn't provide "
311                      "information about the block size and it doesn't have a "
312                      "backing file. The default block size of %u bytes is "
313                      "used. If the actual block size of the target exceeds "
314                      "this default, the backup may be unusable",
315                      BACKUP_CLUSTER_SIZE_DEFAULT);
316          return BACKUP_CLUSTER_SIZE_DEFAULT;
317      } else if (ret < 0 && !target_does_cow) {
318          error_setg_errno(errp, -ret,
319              "Couldn't determine the cluster size of the target image, "
320              "which has no backing file");
321          error_append_hint(errp,
322              "Aborting, since this may create an unusable destination image\n");
323          return ret;
324      } else if (ret < 0 && target_does_cow) {
325          /* Not fatal; just trudge on ahead. */
326          return BACKUP_CLUSTER_SIZE_DEFAULT;
327      }
328  
329      return MAX(BACKUP_CLUSTER_SIZE_DEFAULT, bdi.cluster_size);
330  }
331  
332  BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
333                    BlockDriverState *target, int64_t speed,
334                    MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
335                    BitmapSyncMode bitmap_mode,
336                    bool compress,
337                    const char *filter_node_name,
338                    BlockdevOnError on_source_error,
339                    BlockdevOnError on_target_error,
340                    int creation_flags,
341                    BlockCompletionFunc *cb, void *opaque,
342                    JobTxn *txn, Error **errp)
343  {
344      int64_t len, target_len;
345      BackupBlockJob *job = NULL;
346      int64_t cluster_size;
347      BdrvRequestFlags write_flags;
348      BlockDriverState *backup_top = NULL;
349      BlockCopyState *bcs = NULL;
350  
351      assert(bs);
352      assert(target);
353  
354      /* QMP interface protects us from these cases */
355      assert(sync_mode != MIRROR_SYNC_MODE_INCREMENTAL);
356      assert(sync_bitmap || sync_mode != MIRROR_SYNC_MODE_BITMAP);
357  
358      if (bs == target) {
359          error_setg(errp, "Source and target cannot be the same");
360          return NULL;
361      }
362  
363      if (!bdrv_is_inserted(bs)) {
364          error_setg(errp, "Device is not inserted: %s",
365                     bdrv_get_device_name(bs));
366          return NULL;
367      }
368  
369      if (!bdrv_is_inserted(target)) {
370          error_setg(errp, "Device is not inserted: %s",
371                     bdrv_get_device_name(target));
372          return NULL;
373      }
374  
375      if (compress && !bdrv_supports_compressed_writes(target)) {
376          error_setg(errp, "Compression is not supported for this drive %s",
377                     bdrv_get_device_name(target));
378          return NULL;
379      }
380  
381      if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
382          return NULL;
383      }
384  
385      if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) {
386          return NULL;
387      }
388  
389      if (sync_bitmap) {
390          /* If we need to write to this bitmap, check that we can: */
391          if (bitmap_mode != BITMAP_SYNC_MODE_NEVER &&
392              bdrv_dirty_bitmap_check(sync_bitmap, BDRV_BITMAP_DEFAULT, errp)) {
393              return NULL;
394          }
395  
396          /* Create a new bitmap, and freeze/disable this one. */
397          if (bdrv_dirty_bitmap_create_successor(sync_bitmap, errp) < 0) {
398              return NULL;
399          }
400      }
401  
402      len = bdrv_getlength(bs);
403      if (len < 0) {
404          error_setg_errno(errp, -len, "Unable to get length for '%s'",
405                           bdrv_get_device_or_node_name(bs));
406          goto error;
407      }
408  
409      target_len = bdrv_getlength(target);
410      if (target_len < 0) {
411          error_setg_errno(errp, -target_len, "Unable to get length for '%s'",
412                           bdrv_get_device_or_node_name(bs));
413          goto error;
414      }
415  
416      if (target_len != len) {
417          error_setg(errp, "Source and target image have different sizes");
418          goto error;
419      }
420  
421      cluster_size = backup_calculate_cluster_size(target, errp);
422      if (cluster_size < 0) {
423          goto error;
424      }
425  
426      /*
427       * If source is in backing chain of target assume that target is going to be
428       * used for "image fleecing", i.e. it should represent a kind of snapshot of
429       * source at backup-start point in time. And target is going to be read by
430       * somebody (for example, used as NBD export) during backup job.
431       *
432       * In this case, we need to add BDRV_REQ_SERIALISING write flag to avoid
433       * intersection of backup writes and third party reads from target,
434       * otherwise reading from target we may occasionally read already updated by
435       * guest data.
436       *
437       * For more information see commit f8d59dfb40bb and test
438       * tests/qemu-iotests/222
439       */
440      write_flags = (bdrv_chain_contains(target, bs) ? BDRV_REQ_SERIALISING : 0) |
441                    (compress ? BDRV_REQ_WRITE_COMPRESSED : 0),
442  
443      backup_top = bdrv_backup_top_append(bs, target, filter_node_name,
444                                          cluster_size, write_flags, &bcs, errp);
445      if (!backup_top) {
446          goto error;
447      }
448  
449      /* job->len is fixed, so we can't allow resize */
450      job = block_job_create(job_id, &backup_job_driver, txn, backup_top,
451                             0, BLK_PERM_ALL,
452                             speed, creation_flags, cb, opaque, errp);
453      if (!job) {
454          goto error;
455      }
456  
457      job->backup_top = backup_top;
458      job->source_bs = bs;
459      job->on_source_error = on_source_error;
460      job->on_target_error = on_target_error;
461      job->sync_mode = sync_mode;
462      job->sync_bitmap = sync_bitmap;
463      job->bitmap_mode = bitmap_mode;
464      job->bcs = bcs;
465      job->cluster_size = cluster_size;
466      job->len = len;
467  
468      block_copy_set_progress_callback(bcs, backup_progress_bytes_callback, job);
469      block_copy_set_progress_meter(bcs, &job->common.job.progress);
470  
471      /* Required permissions are already taken by backup-top target */
472      block_job_add_bdrv(&job->common, "target", target, 0, BLK_PERM_ALL,
473                         &error_abort);
474  
475      return &job->common;
476  
477   error:
478      if (sync_bitmap) {
479          bdrv_reclaim_dirty_bitmap(sync_bitmap, NULL);
480      }
481      if (backup_top) {
482          bdrv_backup_top_drop(backup_top);
483      }
484  
485      return NULL;
486  }
487