Merge remote-tracking branch 'remotes/mst/tags/for_upstream' into staging
[qemu/ar7.git] / block / commit.c
blobdd9ba87349e3bfa721996c59cbb1ddd9765aa90a
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  */
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"
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 */
34 typedef struct CommitBlockJob {
35     BlockJob common;
36     BlockDriverState *commit_top_bs;
37     BlockBackend *top;
38     BlockBackend *base;
39     BlockDriverState *base_bs;
40     BlockDriverState *base_overlay;
41     BlockdevOnError on_error;
42     bool base_read_only;
43     bool chain_frozen;
44     char *backing_file_str;
45 } CommitBlockJob;
47 static int commit_prepare(Job *job)
49     CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
51     bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
52     s->chain_frozen = false;
54     /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before
55      * the normal backing chain can be restored. */
56     blk_unref(s->base);
57     s->base = NULL;
59     /* FIXME: bdrv_drop_intermediate treats total failures and partial failures
60      * identically. Further work is needed to disambiguate these cases. */
61     return bdrv_drop_intermediate(s->commit_top_bs, s->base_bs,
62                                   s->backing_file_str);
65 static void commit_abort(Job *job)
67     CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
68     BlockDriverState *top_bs = blk_bs(s->top);
70     if (s->chain_frozen) {
71         bdrv_unfreeze_backing_chain(s->commit_top_bs, s->base_bs);
72     }
74     /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */
75     bdrv_ref(top_bs);
76     bdrv_ref(s->commit_top_bs);
78     if (s->base) {
79         blk_unref(s->base);
80     }
82     /* free the blockers on the intermediate nodes so that bdrv_replace_nodes
83      * can succeed */
84     block_job_remove_all_bdrv(&s->common);
86     /* If bdrv_drop_intermediate() failed (or was not invoked), remove the
87      * commit filter driver from the backing chain now. Do this as the final
88      * step so that the 'consistent read' permission can be granted.
89      *
90      * XXX Can (or should) we somehow keep 'consistent read' blocked even
91      * after the failed/cancelled commit job is gone? If we already wrote
92      * something to base, the intermediate images aren't valid any more. */
93     bdrv_replace_node(s->commit_top_bs, s->commit_top_bs->backing->bs,
94                       &error_abort);
96     bdrv_unref(s->commit_top_bs);
97     bdrv_unref(top_bs);
100 static void commit_clean(Job *job)
102     CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
104     /* restore base open flags here if appropriate (e.g., change the base back
105      * to r/o). These reopens do not need to be atomic, since we won't abort
106      * even on failure here */
107     if (s->base_read_only) {
108         bdrv_reopen_set_read_only(s->base_bs, true, NULL);
109     }
111     g_free(s->backing_file_str);
112     blk_unref(s->top);
115 static int coroutine_fn commit_run(Job *job, Error **errp)
117     CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
118     int64_t offset;
119     uint64_t delay_ns = 0;
120     int ret = 0;
121     int64_t n = 0; /* bytes */
122     void *buf = NULL;
123     int64_t len, base_len;
125     ret = len = blk_getlength(s->top);
126     if (len < 0) {
127         goto out;
128     }
129     job_progress_set_remaining(&s->common.job, len);
131     ret = base_len = blk_getlength(s->base);
132     if (base_len < 0) {
133         goto out;
134     }
136     if (base_len < len) {
137         ret = blk_truncate(s->base, len, false, PREALLOC_MODE_OFF, 0, NULL);
138         if (ret) {
139             goto out;
140         }
141     }
143     buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
145     for (offset = 0; offset < len; offset += n) {
146         bool copy;
147         bool error_in_source = true;
149         /* Note that even when no rate limit is applied we need to yield
150          * with no pending I/O here so that bdrv_drain_all() returns.
151          */
152         job_sleep_ns(&s->common.job, delay_ns);
153         if (job_is_cancelled(&s->common.job)) {
154             break;
155         }
156         /* Copy if allocated above the base */
157         ret = bdrv_is_allocated_above(blk_bs(s->top), s->base_overlay, true,
158                                       offset, COMMIT_BUFFER_SIZE, &n);
159         copy = (ret > 0);
160         trace_commit_one_iteration(s, offset, n, ret);
161         if (copy) {
162             assert(n < SIZE_MAX);
164             ret = blk_co_pread(s->top, offset, n, buf, 0);
165             if (ret >= 0) {
166                 ret = blk_co_pwrite(s->base, offset, n, buf, 0);
167                 if (ret < 0) {
168                     error_in_source = false;
169                 }
170             }
171         }
172         if (ret < 0) {
173             BlockErrorAction action =
174                 block_job_error_action(&s->common, s->on_error,
175                                        error_in_source, -ret);
176             if (action == BLOCK_ERROR_ACTION_REPORT) {
177                 goto out;
178             } else {
179                 n = 0;
180                 continue;
181             }
182         }
183         /* Publish progress */
184         job_progress_update(&s->common.job, n);
186         if (copy) {
187             delay_ns = block_job_ratelimit_get_delay(&s->common, n);
188         } else {
189             delay_ns = 0;
190         }
191     }
193     ret = 0;
195 out:
196     qemu_vfree(buf);
198     return ret;
201 static const BlockJobDriver commit_job_driver = {
202     .job_driver = {
203         .instance_size = sizeof(CommitBlockJob),
204         .job_type      = JOB_TYPE_COMMIT,
205         .free          = block_job_free,
206         .user_resume   = block_job_user_resume,
207         .run           = commit_run,
208         .prepare       = commit_prepare,
209         .abort         = commit_abort,
210         .clean         = commit_clean
211     },
214 static int coroutine_fn bdrv_commit_top_preadv(BlockDriverState *bs,
215     uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
217     return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
220 static void bdrv_commit_top_refresh_filename(BlockDriverState *bs)
222     pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
223             bs->backing->bs->filename);
226 static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c,
227                                        BdrvChildRole role,
228                                        BlockReopenQueue *reopen_queue,
229                                        uint64_t perm, uint64_t shared,
230                                        uint64_t *nperm, uint64_t *nshared)
232     *nperm = 0;
233     *nshared = BLK_PERM_ALL;
236 /* Dummy node that provides consistent read to its users without requiring it
237  * from its backing file and that allows writes on the backing file chain. */
238 static BlockDriver bdrv_commit_top = {
239     .format_name                = "commit_top",
240     .bdrv_co_preadv             = bdrv_commit_top_preadv,
241     .bdrv_refresh_filename      = bdrv_commit_top_refresh_filename,
242     .bdrv_child_perm            = bdrv_commit_top_child_perm,
244     .is_filter                  = true,
247 void commit_start(const char *job_id, BlockDriverState *bs,
248                   BlockDriverState *base, BlockDriverState *top,
249                   int creation_flags, int64_t speed,
250                   BlockdevOnError on_error, const char *backing_file_str,
251                   const char *filter_node_name, Error **errp)
253     CommitBlockJob *s;
254     BlockDriverState *iter;
255     BlockDriverState *commit_top_bs = NULL;
256     BlockDriverState *filtered_base;
257     int64_t base_size, top_size;
258     uint64_t base_perms, iter_shared_perms;
259     int ret;
261     assert(top != bs);
262     if (bdrv_skip_filters(top) == bdrv_skip_filters(base)) {
263         error_setg(errp, "Invalid files for merge: top and base are the same");
264         return;
265     }
267     base_size = bdrv_getlength(base);
268     if (base_size < 0) {
269         error_setg_errno(errp, -base_size, "Could not inquire base image size");
270         return;
271     }
273     top_size = bdrv_getlength(top);
274     if (top_size < 0) {
275         error_setg_errno(errp, -top_size, "Could not inquire top image size");
276         return;
277     }
279     base_perms = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE;
280     if (base_size < top_size) {
281         base_perms |= BLK_PERM_RESIZE;
282     }
284     s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL,
285                          speed, creation_flags, NULL, NULL, errp);
286     if (!s) {
287         return;
288     }
290     /* convert base to r/w, if necessary */
291     s->base_read_only = bdrv_is_read_only(base);
292     if (s->base_read_only) {
293         if (bdrv_reopen_set_read_only(base, false, errp) != 0) {
294             goto fail;
295         }
296     }
298     /* Insert commit_top block node above top, so we can block consistent read
299      * on the backing chain below it */
300     commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, filter_node_name, 0,
301                                          errp);
302     if (commit_top_bs == NULL) {
303         goto fail;
304     }
305     if (!filter_node_name) {
306         commit_top_bs->implicit = true;
307     }
309     /* So that we can always drop this node */
310     commit_top_bs->never_freeze = true;
312     commit_top_bs->total_sectors = top->total_sectors;
314     ret = bdrv_append(commit_top_bs, top, errp);
315     if (ret < 0) {
316         commit_top_bs = NULL;
317         goto fail;
318     }
320     s->commit_top_bs = commit_top_bs;
322     /*
323      * Block all nodes between top and base, because they will
324      * disappear from the chain after this operation.
325      * Note that this assumes that the user is fine with removing all
326      * nodes (including R/W filters) between top and base.  Assuring
327      * this is the responsibility of the interface (i.e. whoever calls
328      * commit_start()).
329      */
330     s->base_overlay = bdrv_find_overlay(top, base);
331     assert(s->base_overlay);
333     /*
334      * The topmost node with
335      * bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base)
336      */
337     filtered_base = bdrv_cow_bs(s->base_overlay);
338     assert(bdrv_skip_filters(filtered_base) == bdrv_skip_filters(base));
340     /*
341      * XXX BLK_PERM_WRITE needs to be allowed so we don't block ourselves
342      * at s->base (if writes are blocked for a node, they are also blocked
343      * for its backing file). The other options would be a second filter
344      * driver above s->base.
345      */
346     iter_shared_perms = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE;
348     for (iter = top; iter != base; iter = bdrv_filter_or_cow_bs(iter)) {
349         if (iter == filtered_base) {
350             /*
351              * From here on, all nodes are filters on the base.  This
352              * allows us to share BLK_PERM_CONSISTENT_READ.
353              */
354             iter_shared_perms |= BLK_PERM_CONSISTENT_READ;
355         }
357         ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
358                                  iter_shared_perms, errp);
359         if (ret < 0) {
360             goto fail;
361         }
362     }
364     if (bdrv_freeze_backing_chain(commit_top_bs, base, errp) < 0) {
365         goto fail;
366     }
367     s->chain_frozen = true;
369     ret = block_job_add_bdrv(&s->common, "base", base, 0, BLK_PERM_ALL, errp);
370     if (ret < 0) {
371         goto fail;
372     }
374     s->base = blk_new(s->common.job.aio_context,
375                       base_perms,
376                       BLK_PERM_CONSISTENT_READ
377                       | BLK_PERM_GRAPH_MOD
378                       | BLK_PERM_WRITE_UNCHANGED);
379     ret = blk_insert_bs(s->base, base, errp);
380     if (ret < 0) {
381         goto fail;
382     }
383     blk_set_disable_request_queuing(s->base, true);
384     s->base_bs = base;
386     /* Required permissions are already taken with block_job_add_bdrv() */
387     s->top = blk_new(s->common.job.aio_context, 0, BLK_PERM_ALL);
388     ret = blk_insert_bs(s->top, top, errp);
389     if (ret < 0) {
390         goto fail;
391     }
392     blk_set_disable_request_queuing(s->top, true);
394     s->backing_file_str = g_strdup(backing_file_str);
395     s->on_error = on_error;
397     trace_commit_start(bs, base, top, s);
398     job_start(&s->common.job);
399     return;
401 fail:
402     if (s->chain_frozen) {
403         bdrv_unfreeze_backing_chain(commit_top_bs, base);
404     }
405     if (s->base) {
406         blk_unref(s->base);
407     }
408     if (s->top) {
409         blk_unref(s->top);
410     }
411     if (s->base_read_only) {
412         bdrv_reopen_set_read_only(base, true, NULL);
413     }
414     job_early_fail(&s->common.job);
415     /* commit_top_bs has to be replaced after deleting the block job,
416      * otherwise this would fail because of lack of permissions. */
417     if (commit_top_bs) {
418         bdrv_replace_node(commit_top_bs, top, &error_abort);
419     }
423 #define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE)
425 /* commit COW file into the raw image */
426 int bdrv_commit(BlockDriverState *bs)
428     BlockBackend *src, *backing;
429     BlockDriverState *backing_file_bs = NULL;
430     BlockDriverState *commit_top_bs = NULL;
431     BlockDriver *drv = bs->drv;
432     AioContext *ctx;
433     int64_t offset, length, backing_length;
434     int ro;
435     int64_t n;
436     int ret = 0;
437     uint8_t *buf = NULL;
438     Error *local_err = NULL;
440     if (!drv)
441         return -ENOMEDIUM;
443     backing_file_bs = bdrv_cow_bs(bs);
445     if (!backing_file_bs) {
446         return -ENOTSUP;
447     }
449     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
450         bdrv_op_is_blocked(backing_file_bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL))
451     {
452         return -EBUSY;
453     }
455     ro = backing_file_bs->read_only;
457     if (ro) {
458         if (bdrv_reopen_set_read_only(backing_file_bs, false, NULL)) {
459             return -EACCES;
460         }
461     }
463     ctx = bdrv_get_aio_context(bs);
464     /* WRITE_UNCHANGED is required for bdrv_make_empty() */
465     src = blk_new(ctx, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED,
466                   BLK_PERM_ALL);
467     backing = blk_new(ctx, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
469     ret = blk_insert_bs(src, bs, &local_err);
470     if (ret < 0) {
471         error_report_err(local_err);
472         goto ro_cleanup;
473     }
475     /* Insert commit_top block node above backing, so we can write to it */
476     commit_top_bs = bdrv_new_open_driver(&bdrv_commit_top, NULL, BDRV_O_RDWR,
477                                          &local_err);
478     if (commit_top_bs == NULL) {
479         error_report_err(local_err);
480         goto ro_cleanup;
481     }
483     bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort);
484     bdrv_set_backing_hd(bs, commit_top_bs, &error_abort);
486     ret = blk_insert_bs(backing, backing_file_bs, &local_err);
487     if (ret < 0) {
488         error_report_err(local_err);
489         goto ro_cleanup;
490     }
492     length = blk_getlength(src);
493     if (length < 0) {
494         ret = length;
495         goto ro_cleanup;
496     }
498     backing_length = blk_getlength(backing);
499     if (backing_length < 0) {
500         ret = backing_length;
501         goto ro_cleanup;
502     }
504     /* If our top snapshot is larger than the backing file image,
505      * grow the backing file image if possible.  If not possible,
506      * we must return an error */
507     if (length > backing_length) {
508         ret = blk_truncate(backing, length, false, PREALLOC_MODE_OFF, 0,
509                            &local_err);
510         if (ret < 0) {
511             error_report_err(local_err);
512             goto ro_cleanup;
513         }
514     }
516     /* blk_try_blockalign() for src will choose an alignment that works for
517      * backing as well, so no need to compare the alignment manually. */
518     buf = blk_try_blockalign(src, COMMIT_BUF_SIZE);
519     if (buf == NULL) {
520         ret = -ENOMEM;
521         goto ro_cleanup;
522     }
524     for (offset = 0; offset < length; offset += n) {
525         ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n);
526         if (ret < 0) {
527             goto ro_cleanup;
528         }
529         if (ret) {
530             ret = blk_pread(src, offset, buf, n);
531             if (ret < 0) {
532                 goto ro_cleanup;
533             }
535             ret = blk_pwrite(backing, offset, buf, n, 0);
536             if (ret < 0) {
537                 goto ro_cleanup;
538             }
539         }
540     }
542     ret = blk_make_empty(src, NULL);
543     /* Ignore -ENOTSUP */
544     if (ret < 0 && ret != -ENOTSUP) {
545         goto ro_cleanup;
546     }
548     blk_flush(src);
550     /*
551      * Make sure all data we wrote to the backing device is actually
552      * stable on disk.
553      */
554     blk_flush(backing);
556     ret = 0;
557 ro_cleanup:
558     qemu_vfree(buf);
560     blk_unref(backing);
561     if (bdrv_cow_bs(bs) != backing_file_bs) {
562         bdrv_set_backing_hd(bs, backing_file_bs, &error_abort);
563     }
564     bdrv_unref(commit_top_bs);
565     blk_unref(src);
567     if (ro) {
568         /* ignoring error return here */
569         bdrv_reopen_set_read_only(backing_file_bs, true, NULL);
570     }
572     return ret;