| 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 | |
| 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 | |
| 54 | static int GRAPH_UNLOCKED 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 all block nodes are drained. Drain |
| 77 | * already here, because the polling during drained_begin() might change the |
| 78 | * graph, and if we do this only later, we may end up working with the wrong |
| 79 | * base node (or it might even have gone away by the time we want to use |
| 80 | * it). |
| 81 | */ |
| 82 | if (unfiltered_bs_cow) { |
| 83 | bdrv_ref(unfiltered_bs_cow); |
| 84 | } |
| 85 | bdrv_drain_all_begin(); |
| 86 | |
| 87 | bdrv_graph_rdlock_main_loop(); |
| 88 | base = bdrv_filter_or_cow_bs(s->above_base); |
| 89 | unfiltered_base = bdrv_skip_filters(base); |
| 90 | bdrv_graph_rdunlock_main_loop(); |
| 91 | |
| 92 | if (unfiltered_bs_cow) { |
| 93 | const char *base_id = NULL, *base_fmt = NULL; |
| 94 | if (unfiltered_base) { |
| 95 | base_id = s->backing_file_str ?: unfiltered_base->filename; |
| 96 | if (unfiltered_base->drv) { |
| 97 | if (s->backing_mask_protocol && |
| 98 | unfiltered_base->drv->protocol_name) { |
| 99 | base_fmt = "raw"; |
| 100 | } else { |
| 101 | base_fmt = unfiltered_base->drv->format_name; |
| 102 | } |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | bdrv_graph_wrlock(); |
| 107 | bdrv_set_backing_hd(unfiltered_bs, base, &local_err); |
| 108 | bdrv_graph_wrunlock(); |
| 109 | |
| 110 | /* |
| 111 | * This call will do I/O, so the graph can change again from here on. |
| 112 | * We have already completed the graph change, so we are not in danger |
| 113 | * of operating on the wrong node any more if this happens. |
| 114 | */ |
| 115 | ret = bdrv_change_backing_file(unfiltered_bs, base_id, base_fmt, false); |
| 116 | if (local_err) { |
| 117 | error_report_err(local_err); |
| 118 | ret = -EPERM; |
| 119 | goto out; |
| 120 | } |
| 121 | } |
| 122 | |
| 123 | out: |
| 124 | bdrv_drain_all_end(); |
| 125 | if (unfiltered_bs_cow) { |
| 126 | bdrv_unref(unfiltered_bs_cow); |
| 127 | } |
| 128 | return ret; |
| 129 | } |
| 130 | |
| 131 | static void stream_clean(Job *job) |
| 132 | { |
| 133 | StreamBlockJob *s = container_of(job, StreamBlockJob, common.job); |
| 134 | |
| 135 | if (s->cor_filter_bs) { |
| 136 | bdrv_cor_filter_drop(s->cor_filter_bs); |
| 137 | s->cor_filter_bs = NULL; |
| 138 | } |
| 139 | |
| 140 | blk_unref(s->blk); |
| 141 | s->blk = NULL; |
| 142 | |
| 143 | /* Reopen the image back in read-only mode if necessary */ |
| 144 | if (s->bs_read_only) { |
| 145 | /* Give up write permissions before making it read-only */ |
| 146 | bdrv_reopen_set_read_only(s->target_bs, true, NULL); |
| 147 | } |
| 148 | |
| 149 | g_free(s->backing_file_str); |
| 150 | } |
| 151 | |
| 152 | static int coroutine_fn stream_run(Job *job, Error **errp) |
| 153 | { |
| 154 | StreamBlockJob *s = container_of(job, StreamBlockJob, common.job); |
| 155 | BlockDriverState *unfiltered_bs = NULL; |
| 156 | int64_t len = -1; |
| 157 | int64_t offset = 0; |
| 158 | int error = 0; |
| 159 | int64_t n = 0; /* bytes */ |
| 160 | |
| 161 | WITH_GRAPH_RDLOCK_GUARD() { |
| 162 | unfiltered_bs = bdrv_skip_filters(s->target_bs); |
| 163 | if (unfiltered_bs == s->base_overlay) { |
| 164 | /* Nothing to stream */ |
| 165 | return 0; |
| 166 | } |
| 167 | |
| 168 | len = bdrv_co_getlength(s->target_bs); |
| 169 | if (len < 0) { |
| 170 | return len; |
| 171 | } |
| 172 | } |
| 173 | job_progress_set_remaining(&s->common.job, len); |
| 174 | |
| 175 | for ( ; offset < len; offset += n) { |
| 176 | bool copy; |
| 177 | int ret = -1; |
| 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_ratelimit_sleep(&s->common); |
| 183 | if (job_is_cancelled(&s->common.job)) { |
| 184 | break; |
| 185 | } |
| 186 | |
| 187 | copy = false; |
| 188 | |
| 189 | WITH_GRAPH_RDLOCK_GUARD() { |
| 190 | ret = bdrv_co_is_allocated(unfiltered_bs, offset, STREAM_CHUNK, &n); |
| 191 | if (ret == 1) { |
| 192 | /* Allocated in the top, no need to copy. */ |
| 193 | } else if (ret >= 0) { |
| 194 | /* |
| 195 | * Copy if allocated in the intermediate images. Limit to the |
| 196 | * known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE). |
| 197 | */ |
| 198 | ret = bdrv_co_is_allocated_above(bdrv_cow_bs(unfiltered_bs), |
| 199 | s->base_overlay, true, |
| 200 | offset, n, &n); |
| 201 | /* Finish early if end of backing file has been reached */ |
| 202 | if (ret == 0 && n == 0) { |
| 203 | n = len - offset; |
| 204 | } |
| 205 | |
| 206 | copy = (ret > 0); |
| 207 | } |
| 208 | } |
| 209 | trace_stream_one_iteration(s, offset, n, ret); |
| 210 | if (copy) { |
| 211 | ret = stream_populate(s->blk, offset, n); |
| 212 | } |
| 213 | if (ret < 0) { |
| 214 | BlockErrorAction action = |
| 215 | block_job_error_action(&s->common, s->on_error, true, -ret); |
| 216 | if (action == BLOCK_ERROR_ACTION_STOP) { |
| 217 | n = 0; |
| 218 | continue; |
| 219 | } |
| 220 | if (error == 0) { |
| 221 | error = ret; |
| 222 | } |
| 223 | if (action == BLOCK_ERROR_ACTION_REPORT) { |
| 224 | break; |
| 225 | } |
| 226 | } |
| 227 | |
| 228 | /* Publish progress */ |
| 229 | job_progress_update(&s->common.job, n); |
| 230 | if (copy) { |
| 231 | block_job_ratelimit_processed_bytes(&s->common, n); |
| 232 | } |
| 233 | } |
| 234 | |
| 235 | /* Do not remove the backing file if an error was there but ignored. */ |
| 236 | return error; |
| 237 | } |
| 238 | |
| 239 | static const BlockJobDriver stream_job_driver = { |
| 240 | .job_driver = { |
| 241 | .instance_size = sizeof(StreamBlockJob), |
| 242 | .job_type = JOB_TYPE_STREAM, |
| 243 | .free = block_job_free, |
| 244 | .run = stream_run, |
| 245 | .prepare = stream_prepare, |
| 246 | .clean = stream_clean, |
| 247 | .user_resume = block_job_user_resume, |
| 248 | }, |
| 249 | }; |
| 250 | |
| 251 | void stream_start(const char *job_id, BlockDriverState *bs, |
| 252 | BlockDriverState *base, const char *backing_file_str, |
| 253 | bool backing_mask_protocol, |
| 254 | BlockDriverState *bottom, |
| 255 | int creation_flags, int64_t speed, |
| 256 | BlockdevOnError on_error, |
| 257 | const char *filter_node_name, |
| 258 | Error **errp) |
| 259 | { |
| 260 | StreamBlockJob *s = NULL; |
| 261 | BlockDriverState *iter; |
| 262 | bool bs_read_only; |
| 263 | int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED; |
| 264 | BlockDriverState *base_overlay; |
| 265 | BlockDriverState *cor_filter_bs = NULL; |
| 266 | BlockDriverState *above_base; |
| 267 | QDict *opts; |
| 268 | int ret; |
| 269 | |
| 270 | GLOBAL_STATE_CODE(); |
| 271 | |
| 272 | assert(!(base && bottom)); |
| 273 | assert(!(backing_file_str && bottom)); |
| 274 | |
| 275 | bdrv_graph_rdlock_main_loop(); |
| 276 | |
| 277 | if (bottom) { |
| 278 | /* |
| 279 | * New simple interface. The code is written in terms of old interface |
| 280 | * with @base parameter (still, it doesn't freeze link to base, so in |
| 281 | * this mean old code is correct for new interface). So, for now, just |
| 282 | * emulate base_overlay and above_base. Still, when old interface |
| 283 | * finally removed, we should refactor code to use only "bottom", but |
| 284 | * not "*base*" things. |
| 285 | */ |
| 286 | assert(!bottom->drv->is_filter); |
| 287 | base_overlay = above_base = bottom; |
| 288 | } else { |
| 289 | base_overlay = bdrv_find_overlay(bs, base); |
| 290 | if (!base_overlay) { |
| 291 | error_setg(errp, "'%s' is not in the backing chain of '%s'", |
| 292 | base->node_name, bs->node_name); |
| 293 | goto out_rdlock; |
| 294 | } |
| 295 | |
| 296 | /* |
| 297 | * Find the node directly above @base. @base_overlay is a COW overlay, |
| 298 | * so it must have a bdrv_cow_child(), but it is the immediate overlay |
| 299 | * of @base, so between the two there can only be filters. |
| 300 | */ |
| 301 | above_base = base_overlay; |
| 302 | if (bdrv_cow_bs(above_base) != base) { |
| 303 | above_base = bdrv_cow_bs(above_base); |
| 304 | while (bdrv_filter_bs(above_base) != base) { |
| 305 | above_base = bdrv_filter_bs(above_base); |
| 306 | } |
| 307 | } |
| 308 | } |
| 309 | |
| 310 | /* Make sure that the image is opened in read-write mode */ |
| 311 | bs_read_only = bdrv_is_read_only(bs); |
| 312 | if (bs_read_only) { |
| 313 | /* Hold the chain during reopen */ |
| 314 | if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) { |
| 315 | goto out_rdlock; |
| 316 | } |
| 317 | |
| 318 | ret = bdrv_reopen_set_read_only(bs, false, errp); |
| 319 | |
| 320 | /* failure, or cor-filter will hold the chain */ |
| 321 | bdrv_unfreeze_backing_chain(bs, above_base); |
| 322 | |
| 323 | if (ret < 0) { |
| 324 | goto out_rdlock; |
| 325 | } |
| 326 | } |
| 327 | |
| 328 | bdrv_graph_rdunlock_main_loop(); |
| 329 | |
| 330 | opts = qdict_new(); |
| 331 | |
| 332 | qdict_put_str(opts, "driver", "copy-on-read"); |
| 333 | qdict_put_str(opts, "file", bdrv_get_node_name(bs)); |
| 334 | /* Pass the base_overlay node name as 'bottom' to COR driver */ |
| 335 | qdict_put_str(opts, "bottom", base_overlay->node_name); |
| 336 | if (filter_node_name) { |
| 337 | qdict_put_str(opts, "node-name", filter_node_name); |
| 338 | } |
| 339 | |
| 340 | cor_filter_bs = bdrv_insert_node(bs, opts, BDRV_O_RDWR, errp); |
| 341 | if (!cor_filter_bs) { |
| 342 | goto fail; |
| 343 | } |
| 344 | |
| 345 | if (!filter_node_name) { |
| 346 | cor_filter_bs->implicit = true; |
| 347 | } |
| 348 | |
| 349 | s = block_job_create(job_id, &stream_job_driver, NULL, cor_filter_bs, |
| 350 | 0, BLK_PERM_ALL, |
| 351 | speed, creation_flags, NULL, NULL, errp); |
| 352 | if (!s) { |
| 353 | goto fail; |
| 354 | } |
| 355 | |
| 356 | s->blk = blk_new_with_bs(cor_filter_bs, BLK_PERM_CONSISTENT_READ, |
| 357 | basic_flags | BLK_PERM_WRITE, errp); |
| 358 | if (!s->blk) { |
| 359 | goto fail; |
| 360 | } |
| 361 | /* |
| 362 | * Disable request queuing in the BlockBackend to avoid deadlocks on drain: |
| 363 | * The job reports that it's busy until it reaches a pause point. |
| 364 | */ |
| 365 | blk_set_disable_request_queuing(s->blk, true); |
| 366 | blk_set_allow_aio_context_change(s->blk, true); |
| 367 | |
| 368 | /* |
| 369 | * Prevent concurrent jobs trying to modify the graph structure here, we |
| 370 | * already have our own plans. Also don't allow resize as the image size is |
| 371 | * queried only at the job start and then cached. |
| 372 | */ |
| 373 | bdrv_graph_wrlock_drained(); |
| 374 | if (block_job_add_bdrv(&s->common, "active node", bs, 0, |
| 375 | basic_flags | BLK_PERM_WRITE, errp)) { |
| 376 | bdrv_graph_wrunlock(); |
| 377 | goto fail; |
| 378 | } |
| 379 | |
| 380 | /* Block all intermediate nodes between bs and base, because they will |
| 381 | * disappear from the chain after this operation. The streaming job reads |
| 382 | * every block only once, assuming that it doesn't change, so forbid writes |
| 383 | * and resizes. Reassign the base node pointer because the backing BS of the |
| 384 | * bottom node might change after the call to bdrv_reopen_set_read_only() |
| 385 | * due to parallel block jobs running. |
| 386 | * above_base node might change after the call to |
| 387 | * bdrv_reopen_set_read_only() due to parallel block jobs running. |
| 388 | */ |
| 389 | base = bdrv_filter_or_cow_bs(above_base); |
| 390 | for (iter = bdrv_filter_or_cow_bs(bs); iter != base; |
| 391 | iter = bdrv_filter_or_cow_bs(iter)) |
| 392 | { |
| 393 | ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0, |
| 394 | basic_flags, errp); |
| 395 | if (ret < 0) { |
| 396 | bdrv_graph_wrunlock(); |
| 397 | goto fail; |
| 398 | } |
| 399 | } |
| 400 | bdrv_graph_wrunlock(); |
| 401 | |
| 402 | s->base_overlay = base_overlay; |
| 403 | s->above_base = above_base; |
| 404 | s->backing_file_str = g_strdup(backing_file_str); |
| 405 | s->backing_mask_protocol = backing_mask_protocol; |
| 406 | s->cor_filter_bs = cor_filter_bs; |
| 407 | s->target_bs = bs; |
| 408 | s->bs_read_only = bs_read_only; |
| 409 | |
| 410 | s->on_error = on_error; |
| 411 | trace_stream_start(bs, base, s); |
| 412 | job_start(&s->common.job); |
| 413 | return; |
| 414 | |
| 415 | fail: |
| 416 | if (s) { |
| 417 | job_early_fail(&s->common.job); |
| 418 | } |
| 419 | if (cor_filter_bs) { |
| 420 | bdrv_cor_filter_drop(cor_filter_bs); |
| 421 | } |
| 422 | if (bs_read_only) { |
| 423 | bdrv_reopen_set_read_only(bs, true, NULL); |
| 424 | } |
| 425 | return; |
| 426 | |
| 427 | out_rdlock: |
| 428 | bdrv_graph_rdunlock_main_loop(); |
| 429 | } |