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 "qobject/qdict.h"
20 #include "qemu/ratelimit.h"
21 #include "system/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 backing_mask_protocol;
43 bool bs_read_only;
44 } StreamBlockJob;
45
stream_populate(BlockBackend * blk,int64_t offset,uint64_t bytes)46 static int coroutine_fn stream_populate(BlockBackend *blk,
47 int64_t offset, uint64_t bytes)
48 {
49 assert(bytes < SIZE_MAX);
50
51 return blk_co_preadv(blk, offset, bytes, NULL, BDRV_REQ_PREFETCH);
52 }
53
stream_prepare(Job * job)54 static int stream_prepare(Job *job)
55 {
56 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
57 BlockDriverState *unfiltered_bs;
58 BlockDriverState *unfiltered_bs_cow;
59 BlockDriverState *base;
60 BlockDriverState *unfiltered_base;
61 Error *local_err = NULL;
62 int ret = 0;
63
64 GLOBAL_STATE_CODE();
65
66 bdrv_graph_rdlock_main_loop();
67 unfiltered_bs = bdrv_skip_filters(s->target_bs);
68 unfiltered_bs_cow = bdrv_cow_bs(unfiltered_bs);
69 bdrv_graph_rdunlock_main_loop();
70
71 /* We should drop filter at this point, as filter hold the backing chain */
72 bdrv_cor_filter_drop(s->cor_filter_bs);
73 s->cor_filter_bs = NULL;
74
75 /*
76 * bdrv_set_backing_hd() requires that the unfiltered_bs and the COW child
77 * of unfiltered_bs is drained. Drain already here and use
78 * bdrv_set_backing_hd_drained() instead because the polling during
79 * drained_begin() might change the graph, and if we do this only later, we
80 * may end up working with the wrong base node (or it might even have gone
81 * away by the time we want to use it).
82 */
83 if (unfiltered_bs_cow) {
84 bdrv_ref(unfiltered_bs_cow);
85 }
86 bdrv_drain_all_begin();
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 if (s->backing_mask_protocol &&
99 unfiltered_base->drv->protocol_name) {
100 base_fmt = "raw";
101 } else {
102 base_fmt = unfiltered_base->drv->format_name;
103 }
104 }
105 }
106
107 bdrv_graph_wrlock();
108 bdrv_set_backing_hd_drained(unfiltered_bs, base, &local_err);
109 bdrv_graph_wrunlock();
110
111 /*
112 * This call will do I/O, so the graph can change again from here on.
113 * We have already completed the graph change, so we are not in danger
114 * of operating on the wrong node any more if this happens.
115 */
116 ret = bdrv_change_backing_file(unfiltered_bs, base_id, base_fmt, false);
117 if (local_err) {
118 error_report_err(local_err);
119 ret = -EPERM;
120 goto out;
121 }
122 }
123
124 out:
125 bdrv_drain_all_end();
126 if (unfiltered_bs_cow) {
127 bdrv_unref(unfiltered_bs_cow);
128 }
129 return ret;
130 }
131
stream_clean(Job * job)132 static void stream_clean(Job *job)
133 {
134 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
135
136 if (s->cor_filter_bs) {
137 bdrv_cor_filter_drop(s->cor_filter_bs);
138 s->cor_filter_bs = NULL;
139 }
140
141 blk_unref(s->blk);
142 s->blk = NULL;
143
144 /* Reopen the image back in read-only mode if necessary */
145 if (s->bs_read_only) {
146 /* Give up write permissions before making it read-only */
147 bdrv_reopen_set_read_only(s->target_bs, true, NULL);
148 }
149
150 g_free(s->backing_file_str);
151 }
152
stream_run(Job * job,Error ** errp)153 static int coroutine_fn stream_run(Job *job, Error **errp)
154 {
155 StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
156 BlockDriverState *unfiltered_bs = NULL;
157 int64_t len = -1;
158 int64_t offset = 0;
159 int error = 0;
160 int64_t n = 0; /* bytes */
161
162 WITH_GRAPH_RDLOCK_GUARD() {
163 unfiltered_bs = bdrv_skip_filters(s->target_bs);
164 if (unfiltered_bs == s->base_overlay) {
165 /* Nothing to stream */
166 return 0;
167 }
168
169 len = bdrv_co_getlength(s->target_bs);
170 if (len < 0) {
171 return len;
172 }
173 }
174 job_progress_set_remaining(&s->common.job, len);
175
176 for ( ; offset < len; offset += n) {
177 bool copy;
178 int ret = -1;
179
180 /* Note that even when no rate limit is applied we need to yield
181 * with no pending I/O here so that bdrv_drain_all() returns.
182 */
183 block_job_ratelimit_sleep(&s->common);
184 if (job_is_cancelled(&s->common.job)) {
185 break;
186 }
187
188 copy = false;
189
190 WITH_GRAPH_RDLOCK_GUARD() {
191 ret = bdrv_co_is_allocated(unfiltered_bs, offset, STREAM_CHUNK, &n);
192 if (ret == 1) {
193 /* Allocated in the top, no need to copy. */
194 } else if (ret >= 0) {
195 /*
196 * Copy if allocated in the intermediate images. Limit to the
197 * known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE).
198 */
199 ret = bdrv_co_is_allocated_above(bdrv_cow_bs(unfiltered_bs),
200 s->base_overlay, true,
201 offset, n, &n);
202 /* Finish early if end of backing file has been reached */
203 if (ret == 0 && n == 0) {
204 n = len - offset;
205 }
206
207 copy = (ret > 0);
208 }
209 }
210 trace_stream_one_iteration(s, offset, n, ret);
211 if (copy) {
212 ret = stream_populate(s->blk, offset, n);
213 }
214 if (ret < 0) {
215 BlockErrorAction action =
216 block_job_error_action(&s->common, s->on_error, true, -ret);
217 if (action == BLOCK_ERROR_ACTION_STOP) {
218 n = 0;
219 continue;
220 }
221 if (error == 0) {
222 error = ret;
223 }
224 if (action == BLOCK_ERROR_ACTION_REPORT) {
225 break;
226 }
227 }
228
229 /* Publish progress */
230 job_progress_update(&s->common.job, n);
231 if (copy) {
232 block_job_ratelimit_processed_bytes(&s->common, n);
233 }
234 }
235
236 /* Do not remove the backing file if an error was there but ignored. */
237 return error;
238 }
239
240 static const BlockJobDriver stream_job_driver = {
241 .job_driver = {
242 .instance_size = sizeof(StreamBlockJob),
243 .job_type = JOB_TYPE_STREAM,
244 .free = block_job_free,
245 .run = stream_run,
246 .prepare = stream_prepare,
247 .clean = stream_clean,
248 .user_resume = block_job_user_resume,
249 },
250 };
251
stream_start(const char * job_id,BlockDriverState * bs,BlockDriverState * base,const char * backing_file_str,bool backing_mask_protocol,BlockDriverState * bottom,int creation_flags,int64_t speed,BlockdevOnError on_error,const char * filter_node_name,Error ** errp)252 void stream_start(const char *job_id, BlockDriverState *bs,
253 BlockDriverState *base, const char *backing_file_str,
254 bool backing_mask_protocol,
255 BlockDriverState *bottom,
256 int creation_flags, int64_t speed,
257 BlockdevOnError on_error,
258 const char *filter_node_name,
259 Error **errp)
260 {
261 StreamBlockJob *s = NULL;
262 BlockDriverState *iter;
263 bool bs_read_only;
264 int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
265 BlockDriverState *base_overlay;
266 BlockDriverState *cor_filter_bs = NULL;
267 BlockDriverState *above_base;
268 QDict *opts;
269 int ret;
270
271 GLOBAL_STATE_CODE();
272
273 assert(!(base && bottom));
274 assert(!(backing_file_str && bottom));
275
276 bdrv_graph_rdlock_main_loop();
277
278 if (bottom) {
279 /*
280 * New simple interface. The code is written in terms of old interface
281 * with @base parameter (still, it doesn't freeze link to base, so in
282 * this mean old code is correct for new interface). So, for now, just
283 * emulate base_overlay and above_base. Still, when old interface
284 * finally removed, we should refactor code to use only "bottom", but
285 * not "*base*" things.
286 */
287 assert(!bottom->drv->is_filter);
288 base_overlay = above_base = bottom;
289 } else {
290 base_overlay = bdrv_find_overlay(bs, base);
291 if (!base_overlay) {
292 error_setg(errp, "'%s' is not in the backing chain of '%s'",
293 base->node_name, bs->node_name);
294 goto out_rdlock;
295 }
296
297 /*
298 * Find the node directly above @base. @base_overlay is a COW overlay,
299 * so it must have a bdrv_cow_child(), but it is the immediate overlay
300 * of @base, so between the two there can only be filters.
301 */
302 above_base = base_overlay;
303 if (bdrv_cow_bs(above_base) != base) {
304 above_base = bdrv_cow_bs(above_base);
305 while (bdrv_filter_bs(above_base) != base) {
306 above_base = bdrv_filter_bs(above_base);
307 }
308 }
309 }
310
311 /* Make sure that the image is opened in read-write mode */
312 bs_read_only = bdrv_is_read_only(bs);
313 if (bs_read_only) {
314 /* Hold the chain during reopen */
315 if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) {
316 goto out_rdlock;
317 }
318
319 ret = bdrv_reopen_set_read_only(bs, false, errp);
320
321 /* failure, or cor-filter will hold the chain */
322 bdrv_unfreeze_backing_chain(bs, above_base);
323
324 if (ret < 0) {
325 goto out_rdlock;
326 }
327 }
328
329 bdrv_graph_rdunlock_main_loop();
330
331 opts = qdict_new();
332
333 qdict_put_str(opts, "driver", "copy-on-read");
334 qdict_put_str(opts, "file", bdrv_get_node_name(bs));
335 /* Pass the base_overlay node name as 'bottom' to COR driver */
336 qdict_put_str(opts, "bottom", base_overlay->node_name);
337 if (filter_node_name) {
338 qdict_put_str(opts, "node-name", filter_node_name);
339 }
340
341 cor_filter_bs = bdrv_insert_node(bs, opts, BDRV_O_RDWR, errp);
342 if (!cor_filter_bs) {
343 goto fail;
344 }
345
346 if (!filter_node_name) {
347 cor_filter_bs->implicit = true;
348 }
349
350 s = block_job_create(job_id, &stream_job_driver, NULL, cor_filter_bs,
351 0, BLK_PERM_ALL,
352 speed, creation_flags, NULL, NULL, errp);
353 if (!s) {
354 goto fail;
355 }
356
357 s->blk = blk_new_with_bs(cor_filter_bs, BLK_PERM_CONSISTENT_READ,
358 basic_flags | BLK_PERM_WRITE, errp);
359 if (!s->blk) {
360 goto fail;
361 }
362 /*
363 * Disable request queuing in the BlockBackend to avoid deadlocks on drain:
364 * The job reports that it's busy until it reaches a pause point.
365 */
366 blk_set_disable_request_queuing(s->blk, true);
367 blk_set_allow_aio_context_change(s->blk, true);
368
369 /*
370 * Prevent concurrent jobs trying to modify the graph structure here, we
371 * already have our own plans. Also don't allow resize as the image size is
372 * queried only at the job start and then cached.
373 */
374 bdrv_drain_all_begin();
375 bdrv_graph_wrlock();
376 if (block_job_add_bdrv(&s->common, "active node", bs, 0,
377 basic_flags | BLK_PERM_WRITE, errp)) {
378 bdrv_graph_wrunlock();
379 bdrv_drain_all_end();
380 goto fail;
381 }
382
383 /* Block all intermediate nodes between bs and base, because they will
384 * disappear from the chain after this operation. The streaming job reads
385 * every block only once, assuming that it doesn't change, so forbid writes
386 * and resizes. Reassign the base node pointer because the backing BS of the
387 * bottom node might change after the call to bdrv_reopen_set_read_only()
388 * due to parallel block jobs running.
389 * above_base node might change after the call to
390 * bdrv_reopen_set_read_only() due to parallel block jobs running.
391 */
392 base = bdrv_filter_or_cow_bs(above_base);
393 for (iter = bdrv_filter_or_cow_bs(bs); iter != base;
394 iter = bdrv_filter_or_cow_bs(iter))
395 {
396 ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
397 basic_flags, errp);
398 if (ret < 0) {
399 bdrv_graph_wrunlock();
400 bdrv_drain_all_end();
401 goto fail;
402 }
403 }
404 bdrv_graph_wrunlock();
405 bdrv_drain_all_end();
406
407 s->base_overlay = base_overlay;
408 s->above_base = above_base;
409 s->backing_file_str = g_strdup(backing_file_str);
410 s->backing_mask_protocol = backing_mask_protocol;
411 s->cor_filter_bs = cor_filter_bs;
412 s->target_bs = bs;
413 s->bs_read_only = bs_read_only;
414
415 s->on_error = on_error;
416 trace_stream_start(bs, base, s);
417 job_start(&s->common.job);
418 return;
419
420 fail:
421 if (s) {
422 job_early_fail(&s->common.job);
423 }
424 if (cor_filter_bs) {
425 bdrv_cor_filter_drop(cor_filter_bs);
426 }
427 if (bs_read_only) {
428 bdrv_reopen_set_read_only(bs, true, NULL);
429 }
430 return;
431
432 out_rdlock:
433 bdrv_graph_rdunlock_main_loop();
434 }
435