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1 | /* | |
2 | * Image streaming | |
3 | * | |
4 | * Copyright IBM, Corp. 2011 | |
5 | * | |
6 | * Authors: | |
7 | * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> | |
8 | * | |
9 | * This work is licensed under the terms of the GNU LGPL, version 2 or later. | |
10 | * See the COPYING.LIB file in the top-level directory. | |
11 | * | |
12 | */ | |
13 | ||
14 | #include "qemu/osdep.h" | |
15 | #include "trace.h" | |
16 | #include "block/block_int.h" | |
17 | #include "block/blockjob_int.h" | |
18 | #include "qapi/error.h" | |
19 | #include "qapi/qmp/qdict.h" | |
20 | #include "qemu/ratelimit.h" | |
21 | #include "sysemu/block-backend.h" | |
22 | #include "block/copy-on-read.h" | |
23 | ||
24 | enum { | |
25 | /* | |
26 | * Maximum chunk size to feed to copy-on-read. This should be | |
27 | * large enough to process multiple clusters in a single call, so | |
28 | * that populating contiguous regions of the image is efficient. | |
29 | */ | |
30 | STREAM_CHUNK = 512 * 1024, /* in bytes */ | |
31 | }; | |
32 | ||
33 | typedef struct StreamBlockJob { | |
34 | BlockJob common; | |
35 | BlockBackend *blk; | |
36 | BlockDriverState *base_overlay; /* COW overlay (stream from this) */ | |
37 | BlockDriverState *above_base; /* Node directly above the base */ | |
38 | BlockDriverState *cor_filter_bs; | |
39 | BlockDriverState *target_bs; | |
40 | BlockdevOnError on_error; | |
41 | char *backing_file_str; | |
42 | bool bs_read_only; | |
43 | } StreamBlockJob; | |
44 | ||
45 | static int coroutine_fn stream_populate(BlockBackend *blk, | |
46 | int64_t offset, uint64_t bytes) | |
47 | { | |
48 | assert(bytes < SIZE_MAX); | |
49 | ||
50 | return blk_co_preadv(blk, offset, bytes, NULL, BDRV_REQ_PREFETCH); | |
51 | } | |
52 | ||
53 | static int stream_prepare(Job *job) | |
54 | { | |
55 | StreamBlockJob *s = container_of(job, StreamBlockJob, common.job); | |
56 | BlockDriverState *unfiltered_bs; | |
57 | BlockDriverState *unfiltered_bs_cow; | |
58 | BlockDriverState *base; | |
59 | BlockDriverState *unfiltered_base; | |
60 | Error *local_err = NULL; | |
61 | int ret = 0; | |
62 | ||
63 | GLOBAL_STATE_CODE(); | |
64 | ||
65 | bdrv_graph_rdlock_main_loop(); | |
66 | unfiltered_bs = bdrv_skip_filters(s->target_bs); | |
67 | unfiltered_bs_cow = bdrv_cow_bs(unfiltered_bs); | |
68 | bdrv_graph_rdunlock_main_loop(); | |
69 | ||
70 | /* We should drop filter at this point, as filter hold the backing chain */ | |
71 | bdrv_cor_filter_drop(s->cor_filter_bs); | |
72 | s->cor_filter_bs = NULL; | |
73 | ||
74 | /* | |
75 | * bdrv_set_backing_hd() requires that the unfiltered_bs and the COW child | |
76 | * of unfiltered_bs is drained. Drain already here and use | |
77 | * bdrv_set_backing_hd_drained() instead because the polling during | |
78 | * drained_begin() might change the graph, and if we do this only later, we | |
79 | * may end up working with the wrong base node (or it might even have gone | |
80 | * away by the time we want to use it). | |
81 | */ | |
82 | bdrv_drained_begin(unfiltered_bs); | |
83 | if (unfiltered_bs_cow) { | |
84 | bdrv_ref(unfiltered_bs_cow); | |
85 | bdrv_drained_begin(unfiltered_bs_cow); | |
86 | } | |
87 | ||
88 | bdrv_graph_rdlock_main_loop(); | |
89 | base = bdrv_filter_or_cow_bs(s->above_base); | |
90 | unfiltered_base = bdrv_skip_filters(base); | |
91 | bdrv_graph_rdunlock_main_loop(); | |
92 | ||
93 | if (unfiltered_bs_cow) { | |
94 | const char *base_id = NULL, *base_fmt = NULL; | |
95 | if (unfiltered_base) { | |
96 | base_id = s->backing_file_str ?: unfiltered_base->filename; | |
97 | if (unfiltered_base->drv) { | |
98 | base_fmt = unfiltered_base->drv->format_name; | |
99 | } | |
100 | } | |
101 | ||
102 | bdrv_graph_wrlock(s->target_bs); | |
103 | bdrv_set_backing_hd_drained(unfiltered_bs, base, &local_err); | |
104 | bdrv_graph_wrunlock(s->target_bs); | |
105 | ||
106 | /* | |
107 | * This call will do I/O, so the graph can change again from here on. | |
108 | * We have already completed the graph change, so we are not in danger | |
109 | * of operating on the wrong node any more if this happens. | |
110 | */ | |
111 | ret = bdrv_change_backing_file(unfiltered_bs, base_id, base_fmt, false); | |
112 | if (local_err) { | |
113 | error_report_err(local_err); | |
114 | ret = -EPERM; | |
115 | goto out; | |
116 | } | |
117 | } | |
118 | ||
119 | out: | |
120 | if (unfiltered_bs_cow) { | |
121 | bdrv_drained_end(unfiltered_bs_cow); | |
122 | bdrv_unref(unfiltered_bs_cow); | |
123 | } | |
124 | bdrv_drained_end(unfiltered_bs); | |
125 | return ret; | |
126 | } | |
127 | ||
128 | static void stream_clean(Job *job) | |
129 | { | |
130 | StreamBlockJob *s = container_of(job, StreamBlockJob, common.job); | |
131 | ||
132 | if (s->cor_filter_bs) { | |
133 | bdrv_cor_filter_drop(s->cor_filter_bs); | |
134 | s->cor_filter_bs = NULL; | |
135 | } | |
136 | ||
137 | blk_unref(s->blk); | |
138 | s->blk = NULL; | |
139 | ||
140 | /* Reopen the image back in read-only mode if necessary */ | |
141 | if (s->bs_read_only) { | |
142 | /* Give up write permissions before making it read-only */ | |
143 | bdrv_reopen_set_read_only(s->target_bs, true, NULL); | |
144 | } | |
145 | ||
146 | g_free(s->backing_file_str); | |
147 | } | |
148 | ||
149 | static int coroutine_fn stream_run(Job *job, Error **errp) | |
150 | { | |
151 | StreamBlockJob *s = container_of(job, StreamBlockJob, common.job); | |
152 | BlockDriverState *unfiltered_bs; | |
153 | int64_t len; | |
154 | int64_t offset = 0; | |
155 | int error = 0; | |
156 | int64_t n = 0; /* bytes */ | |
157 | ||
158 | WITH_GRAPH_RDLOCK_GUARD() { | |
159 | unfiltered_bs = bdrv_skip_filters(s->target_bs); | |
160 | if (unfiltered_bs == s->base_overlay) { | |
161 | /* Nothing to stream */ | |
162 | return 0; | |
163 | } | |
164 | ||
165 | len = bdrv_co_getlength(s->target_bs); | |
166 | if (len < 0) { | |
167 | return len; | |
168 | } | |
169 | } | |
170 | job_progress_set_remaining(&s->common.job, len); | |
171 | ||
172 | for ( ; offset < len; offset += n) { | |
173 | bool copy; | |
174 | int ret; | |
175 | ||
176 | /* Note that even when no rate limit is applied we need to yield | |
177 | * with no pending I/O here so that bdrv_drain_all() returns. | |
178 | */ | |
179 | block_job_ratelimit_sleep(&s->common); | |
180 | if (job_is_cancelled(&s->common.job)) { | |
181 | break; | |
182 | } | |
183 | ||
184 | copy = false; | |
185 | ||
186 | WITH_GRAPH_RDLOCK_GUARD() { | |
187 | ret = bdrv_co_is_allocated(unfiltered_bs, offset, STREAM_CHUNK, &n); | |
188 | if (ret == 1) { | |
189 | /* Allocated in the top, no need to copy. */ | |
190 | } else if (ret >= 0) { | |
191 | /* | |
192 | * Copy if allocated in the intermediate images. Limit to the | |
193 | * known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE). | |
194 | */ | |
195 | ret = bdrv_co_is_allocated_above(bdrv_cow_bs(unfiltered_bs), | |
196 | s->base_overlay, true, | |
197 | offset, n, &n); | |
198 | /* Finish early if end of backing file has been reached */ | |
199 | if (ret == 0 && n == 0) { | |
200 | n = len - offset; | |
201 | } | |
202 | ||
203 | copy = (ret > 0); | |
204 | } | |
205 | } | |
206 | trace_stream_one_iteration(s, offset, n, ret); | |
207 | if (copy) { | |
208 | ret = stream_populate(s->blk, offset, n); | |
209 | } | |
210 | if (ret < 0) { | |
211 | BlockErrorAction action = | |
212 | block_job_error_action(&s->common, s->on_error, true, -ret); | |
213 | if (action == BLOCK_ERROR_ACTION_STOP) { | |
214 | n = 0; | |
215 | continue; | |
216 | } | |
217 | if (error == 0) { | |
218 | error = ret; | |
219 | } | |
220 | if (action == BLOCK_ERROR_ACTION_REPORT) { | |
221 | break; | |
222 | } | |
223 | } | |
224 | ||
225 | /* Publish progress */ | |
226 | job_progress_update(&s->common.job, n); | |
227 | if (copy) { | |
228 | block_job_ratelimit_processed_bytes(&s->common, n); | |
229 | } | |
230 | } | |
231 | ||
232 | /* Do not remove the backing file if an error was there but ignored. */ | |
233 | return error; | |
234 | } | |
235 | ||
236 | static const BlockJobDriver stream_job_driver = { | |
237 | .job_driver = { | |
238 | .instance_size = sizeof(StreamBlockJob), | |
239 | .job_type = JOB_TYPE_STREAM, | |
240 | .free = block_job_free, | |
241 | .run = stream_run, | |
242 | .prepare = stream_prepare, | |
243 | .clean = stream_clean, | |
244 | .user_resume = block_job_user_resume, | |
245 | }, | |
246 | }; | |
247 | ||
248 | void stream_start(const char *job_id, BlockDriverState *bs, | |
249 | BlockDriverState *base, const char *backing_file_str, | |
250 | BlockDriverState *bottom, | |
251 | int creation_flags, int64_t speed, | |
252 | BlockdevOnError on_error, | |
253 | const char *filter_node_name, | |
254 | Error **errp) | |
255 | { | |
256 | StreamBlockJob *s = NULL; | |
257 | BlockDriverState *iter; | |
258 | bool bs_read_only; | |
259 | int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED; | |
260 | BlockDriverState *base_overlay; | |
261 | BlockDriverState *cor_filter_bs = NULL; | |
262 | BlockDriverState *above_base; | |
263 | QDict *opts; | |
264 | int ret; | |
265 | ||
266 | GLOBAL_STATE_CODE(); | |
267 | ||
268 | assert(!(base && bottom)); | |
269 | assert(!(backing_file_str && bottom)); | |
270 | ||
271 | bdrv_graph_rdlock_main_loop(); | |
272 | ||
273 | if (bottom) { | |
274 | /* | |
275 | * New simple interface. The code is written in terms of old interface | |
276 | * with @base parameter (still, it doesn't freeze link to base, so in | |
277 | * this mean old code is correct for new interface). So, for now, just | |
278 | * emulate base_overlay and above_base. Still, when old interface | |
279 | * finally removed, we should refactor code to use only "bottom", but | |
280 | * not "*base*" things. | |
281 | */ | |
282 | assert(!bottom->drv->is_filter); | |
283 | base_overlay = above_base = bottom; | |
284 | } else { | |
285 | base_overlay = bdrv_find_overlay(bs, base); | |
286 | if (!base_overlay) { | |
287 | error_setg(errp, "'%s' is not in the backing chain of '%s'", | |
288 | base->node_name, bs->node_name); | |
289 | goto out_rdlock; | |
290 | } | |
291 | ||
292 | /* | |
293 | * Find the node directly above @base. @base_overlay is a COW overlay, | |
294 | * so it must have a bdrv_cow_child(), but it is the immediate overlay | |
295 | * of @base, so between the two there can only be filters. | |
296 | */ | |
297 | above_base = base_overlay; | |
298 | if (bdrv_cow_bs(above_base) != base) { | |
299 | above_base = bdrv_cow_bs(above_base); | |
300 | while (bdrv_filter_bs(above_base) != base) { | |
301 | above_base = bdrv_filter_bs(above_base); | |
302 | } | |
303 | } | |
304 | } | |
305 | ||
306 | /* Make sure that the image is opened in read-write mode */ | |
307 | bs_read_only = bdrv_is_read_only(bs); | |
308 | if (bs_read_only) { | |
309 | /* Hold the chain during reopen */ | |
310 | if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) { | |
311 | goto out_rdlock; | |
312 | } | |
313 | ||
314 | ret = bdrv_reopen_set_read_only(bs, false, errp); | |
315 | ||
316 | /* failure, or cor-filter will hold the chain */ | |
317 | bdrv_unfreeze_backing_chain(bs, above_base); | |
318 | ||
319 | if (ret < 0) { | |
320 | goto out_rdlock; | |
321 | } | |
322 | } | |
323 | ||
324 | bdrv_graph_rdunlock_main_loop(); | |
325 | ||
326 | opts = qdict_new(); | |
327 | ||
328 | qdict_put_str(opts, "driver", "copy-on-read"); | |
329 | qdict_put_str(opts, "file", bdrv_get_node_name(bs)); | |
330 | /* Pass the base_overlay node name as 'bottom' to COR driver */ | |
331 | qdict_put_str(opts, "bottom", base_overlay->node_name); | |
332 | if (filter_node_name) { | |
333 | qdict_put_str(opts, "node-name", filter_node_name); | |
334 | } | |
335 | ||
336 | cor_filter_bs = bdrv_insert_node(bs, opts, BDRV_O_RDWR, errp); | |
337 | if (!cor_filter_bs) { | |
338 | goto fail; | |
339 | } | |
340 | ||
341 | if (!filter_node_name) { | |
342 | cor_filter_bs->implicit = true; | |
343 | } | |
344 | ||
345 | s = block_job_create(job_id, &stream_job_driver, NULL, cor_filter_bs, | |
346 | 0, BLK_PERM_ALL, | |
347 | speed, creation_flags, NULL, NULL, errp); | |
348 | if (!s) { | |
349 | goto fail; | |
350 | } | |
351 | ||
352 | s->blk = blk_new_with_bs(cor_filter_bs, BLK_PERM_CONSISTENT_READ, | |
353 | basic_flags | BLK_PERM_WRITE, errp); | |
354 | if (!s->blk) { | |
355 | goto fail; | |
356 | } | |
357 | /* | |
358 | * Disable request queuing in the BlockBackend to avoid deadlocks on drain: | |
359 | * The job reports that it's busy until it reaches a pause point. | |
360 | */ | |
361 | blk_set_disable_request_queuing(s->blk, true); | |
362 | blk_set_allow_aio_context_change(s->blk, true); | |
363 | ||
364 | /* | |
365 | * Prevent concurrent jobs trying to modify the graph structure here, we | |
366 | * already have our own plans. Also don't allow resize as the image size is | |
367 | * queried only at the job start and then cached. | |
368 | */ | |
369 | bdrv_graph_wrlock(bs); | |
370 | if (block_job_add_bdrv(&s->common, "active node", bs, 0, | |
371 | basic_flags | BLK_PERM_WRITE, errp)) { | |
372 | bdrv_graph_wrunlock(bs); | |
373 | goto fail; | |
374 | } | |
375 | ||
376 | /* Block all intermediate nodes between bs and base, because they will | |
377 | * disappear from the chain after this operation. The streaming job reads | |
378 | * every block only once, assuming that it doesn't change, so forbid writes | |
379 | * and resizes. Reassign the base node pointer because the backing BS of the | |
380 | * bottom node might change after the call to bdrv_reopen_set_read_only() | |
381 | * due to parallel block jobs running. | |
382 | * above_base node might change after the call to | |
383 | * bdrv_reopen_set_read_only() due to parallel block jobs running. | |
384 | */ | |
385 | base = bdrv_filter_or_cow_bs(above_base); | |
386 | for (iter = bdrv_filter_or_cow_bs(bs); iter != base; | |
387 | iter = bdrv_filter_or_cow_bs(iter)) | |
388 | { | |
389 | ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0, | |
390 | basic_flags, errp); | |
391 | if (ret < 0) { | |
392 | bdrv_graph_wrunlock(bs); | |
393 | goto fail; | |
394 | } | |
395 | } | |
396 | bdrv_graph_wrunlock(bs); | |
397 | ||
398 | s->base_overlay = base_overlay; | |
399 | s->above_base = above_base; | |
400 | s->backing_file_str = g_strdup(backing_file_str); | |
401 | s->cor_filter_bs = cor_filter_bs; | |
402 | s->target_bs = bs; | |
403 | s->bs_read_only = bs_read_only; | |
404 | ||
405 | s->on_error = on_error; | |
406 | trace_stream_start(bs, base, s); | |
407 | job_start(&s->common.job); | |
408 | return; | |
409 | ||
410 | fail: | |
411 | if (s) { | |
412 | job_early_fail(&s->common.job); | |
413 | } | |
414 | if (cor_filter_bs) { | |
415 | bdrv_cor_filter_drop(cor_filter_bs); | |
416 | } | |
417 | if (bs_read_only) { | |
418 | bdrv_reopen_set_read_only(bs, true, NULL); | |
419 | } | |
420 | return; | |
421 | ||
422 | out_rdlock: | |
423 | bdrv_graph_rdunlock_main_loop(); | |
424 | } |