1 /* 2 * QEMU backup 3 * 4 * Copyright (C) 2013 Proxmox Server Solutions 5 * 6 * Authors: 7 * Dietmar Maurer (dietmar@proxmox.com) 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 * 12 */ 13 14 #include <stdio.h> 15 #include <errno.h> 16 #include <unistd.h> 17 18 #include "trace.h" 19 #include "block/block.h" 20 #include "block/block_int.h" 21 #include "block/blockjob.h" 22 #include "qemu/ratelimit.h" 23 24 #define BACKUP_CLUSTER_BITS 16 25 #define BACKUP_CLUSTER_SIZE (1 << BACKUP_CLUSTER_BITS) 26 #define BACKUP_SECTORS_PER_CLUSTER (BACKUP_CLUSTER_SIZE / BDRV_SECTOR_SIZE) 27 28 #define SLICE_TIME 100000000ULL /* ns */ 29 30 typedef struct CowRequest { 31 int64_t start; 32 int64_t end; 33 QLIST_ENTRY(CowRequest) list; 34 CoQueue wait_queue; /* coroutines blocked on this request */ 35 } CowRequest; 36 37 typedef struct BackupBlockJob { 38 BlockJob common; 39 BlockDriverState *target; 40 MirrorSyncMode sync_mode; 41 RateLimit limit; 42 BlockdevOnError on_source_error; 43 BlockdevOnError on_target_error; 44 CoRwlock flush_rwlock; 45 uint64_t sectors_read; 46 HBitmap *bitmap; 47 QLIST_HEAD(, CowRequest) inflight_reqs; 48 } BackupBlockJob; 49 50 /* See if in-flight requests overlap and wait for them to complete */ 51 static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job, 52 int64_t start, 53 int64_t end) 54 { 55 CowRequest *req; 56 bool retry; 57 58 do { 59 retry = false; 60 QLIST_FOREACH(req, &job->inflight_reqs, list) { 61 if (end > req->start && start < req->end) { 62 qemu_co_queue_wait(&req->wait_queue); 63 retry = true; 64 break; 65 } 66 } 67 } while (retry); 68 } 69 70 /* Keep track of an in-flight request */ 71 static void cow_request_begin(CowRequest *req, BackupBlockJob *job, 72 int64_t start, int64_t end) 73 { 74 req->start = start; 75 req->end = end; 76 qemu_co_queue_init(&req->wait_queue); 77 QLIST_INSERT_HEAD(&job->inflight_reqs, req, list); 78 } 79 80 /* Forget about a completed request */ 81 static void cow_request_end(CowRequest *req) 82 { 83 QLIST_REMOVE(req, list); 84 qemu_co_queue_restart_all(&req->wait_queue); 85 } 86 87 static int coroutine_fn backup_do_cow(BlockDriverState *bs, 88 int64_t sector_num, int nb_sectors, 89 bool *error_is_read) 90 { 91 BackupBlockJob *job = (BackupBlockJob *)bs->job; 92 CowRequest cow_request; 93 struct iovec iov; 94 QEMUIOVector bounce_qiov; 95 void *bounce_buffer = NULL; 96 int ret = 0; 97 int64_t start, end; 98 int n; 99 100 qemu_co_rwlock_rdlock(&job->flush_rwlock); 101 102 start = sector_num / BACKUP_SECTORS_PER_CLUSTER; 103 end = DIV_ROUND_UP(sector_num + nb_sectors, BACKUP_SECTORS_PER_CLUSTER); 104 105 trace_backup_do_cow_enter(job, start, sector_num, nb_sectors); 106 107 wait_for_overlapping_requests(job, start, end); 108 cow_request_begin(&cow_request, job, start, end); 109 110 for (; start < end; start++) { 111 if (hbitmap_get(job->bitmap, start)) { 112 trace_backup_do_cow_skip(job, start); 113 continue; /* already copied */ 114 } 115 116 trace_backup_do_cow_process(job, start); 117 118 n = MIN(BACKUP_SECTORS_PER_CLUSTER, 119 job->common.len / BDRV_SECTOR_SIZE - 120 start * BACKUP_SECTORS_PER_CLUSTER); 121 122 if (!bounce_buffer) { 123 bounce_buffer = qemu_blockalign(bs, BACKUP_CLUSTER_SIZE); 124 } 125 iov.iov_base = bounce_buffer; 126 iov.iov_len = n * BDRV_SECTOR_SIZE; 127 qemu_iovec_init_external(&bounce_qiov, &iov, 1); 128 129 ret = bdrv_co_readv(bs, start * BACKUP_SECTORS_PER_CLUSTER, n, 130 &bounce_qiov); 131 if (ret < 0) { 132 trace_backup_do_cow_read_fail(job, start, ret); 133 if (error_is_read) { 134 *error_is_read = true; 135 } 136 goto out; 137 } 138 139 if (buffer_is_zero(iov.iov_base, iov.iov_len)) { 140 ret = bdrv_co_write_zeroes(job->target, 141 start * BACKUP_SECTORS_PER_CLUSTER, 142 n, BDRV_REQ_MAY_UNMAP); 143 } else { 144 ret = bdrv_co_writev(job->target, 145 start * BACKUP_SECTORS_PER_CLUSTER, n, 146 &bounce_qiov); 147 } 148 if (ret < 0) { 149 trace_backup_do_cow_write_fail(job, start, ret); 150 if (error_is_read) { 151 *error_is_read = false; 152 } 153 goto out; 154 } 155 156 hbitmap_set(job->bitmap, start, 1); 157 158 /* Publish progress, guest I/O counts as progress too. Note that the 159 * offset field is an opaque progress value, it is not a disk offset. 160 */ 161 job->sectors_read += n; 162 job->common.offset += n * BDRV_SECTOR_SIZE; 163 } 164 165 out: 166 if (bounce_buffer) { 167 qemu_vfree(bounce_buffer); 168 } 169 170 cow_request_end(&cow_request); 171 172 trace_backup_do_cow_return(job, sector_num, nb_sectors, ret); 173 174 qemu_co_rwlock_unlock(&job->flush_rwlock); 175 176 return ret; 177 } 178 179 static int coroutine_fn backup_before_write_notify( 180 NotifierWithReturn *notifier, 181 void *opaque) 182 { 183 BdrvTrackedRequest *req = opaque; 184 185 return backup_do_cow(req->bs, req->sector_num, req->nb_sectors, NULL); 186 } 187 188 static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) 189 { 190 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 191 192 if (speed < 0) { 193 error_set(errp, QERR_INVALID_PARAMETER, "speed"); 194 return; 195 } 196 ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME); 197 } 198 199 static void backup_iostatus_reset(BlockJob *job) 200 { 201 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 202 203 bdrv_iostatus_reset(s->target); 204 } 205 206 static const BlockJobDriver backup_job_driver = { 207 .instance_size = sizeof(BackupBlockJob), 208 .job_type = BLOCK_JOB_TYPE_BACKUP, 209 .set_speed = backup_set_speed, 210 .iostatus_reset = backup_iostatus_reset, 211 }; 212 213 static BlockErrorAction backup_error_action(BackupBlockJob *job, 214 bool read, int error) 215 { 216 if (read) { 217 return block_job_error_action(&job->common, job->common.bs, 218 job->on_source_error, true, error); 219 } else { 220 return block_job_error_action(&job->common, job->target, 221 job->on_target_error, false, error); 222 } 223 } 224 225 static void coroutine_fn backup_run(void *opaque) 226 { 227 BackupBlockJob *job = opaque; 228 BlockDriverState *bs = job->common.bs; 229 BlockDriverState *target = job->target; 230 BlockdevOnError on_target_error = job->on_target_error; 231 NotifierWithReturn before_write = { 232 .notify = backup_before_write_notify, 233 }; 234 int64_t start, end; 235 int ret = 0; 236 237 QLIST_INIT(&job->inflight_reqs); 238 qemu_co_rwlock_init(&job->flush_rwlock); 239 240 start = 0; 241 end = DIV_ROUND_UP(job->common.len / BDRV_SECTOR_SIZE, 242 BACKUP_SECTORS_PER_CLUSTER); 243 244 job->bitmap = hbitmap_alloc(end, 0); 245 246 bdrv_set_enable_write_cache(target, true); 247 bdrv_set_on_error(target, on_target_error, on_target_error); 248 bdrv_iostatus_enable(target); 249 250 bdrv_add_before_write_notifier(bs, &before_write); 251 252 if (job->sync_mode == MIRROR_SYNC_MODE_NONE) { 253 while (!block_job_is_cancelled(&job->common)) { 254 /* Yield until the job is cancelled. We just let our before_write 255 * notify callback service CoW requests. */ 256 job->common.busy = false; 257 qemu_coroutine_yield(); 258 job->common.busy = true; 259 } 260 } else { 261 /* Both FULL and TOP SYNC_MODE's require copying.. */ 262 for (; start < end; start++) { 263 bool error_is_read; 264 265 if (block_job_is_cancelled(&job->common)) { 266 break; 267 } 268 269 /* we need to yield so that qemu_aio_flush() returns. 270 * (without, VM does not reboot) 271 */ 272 if (job->common.speed) { 273 uint64_t delay_ns = ratelimit_calculate_delay( 274 &job->limit, job->sectors_read); 275 job->sectors_read = 0; 276 block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, delay_ns); 277 } else { 278 block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, 0); 279 } 280 281 if (block_job_is_cancelled(&job->common)) { 282 break; 283 } 284 285 if (job->sync_mode == MIRROR_SYNC_MODE_TOP) { 286 int i, n; 287 int alloced = 0; 288 289 /* Check to see if these blocks are already in the 290 * backing file. */ 291 292 for (i = 0; i < BACKUP_SECTORS_PER_CLUSTER;) { 293 /* bdrv_is_allocated() only returns true/false based 294 * on the first set of sectors it comes across that 295 * are are all in the same state. 296 * For that reason we must verify each sector in the 297 * backup cluster length. We end up copying more than 298 * needed but at some point that is always the case. */ 299 alloced = 300 bdrv_is_allocated(bs, 301 start * BACKUP_SECTORS_PER_CLUSTER + i, 302 BACKUP_SECTORS_PER_CLUSTER - i, &n); 303 i += n; 304 305 if (alloced == 1) { 306 break; 307 } 308 } 309 310 /* If the above loop never found any sectors that are in 311 * the topmost image, skip this backup. */ 312 if (alloced == 0) { 313 continue; 314 } 315 } 316 /* FULL sync mode we copy the whole drive. */ 317 ret = backup_do_cow(bs, start * BACKUP_SECTORS_PER_CLUSTER, 318 BACKUP_SECTORS_PER_CLUSTER, &error_is_read); 319 if (ret < 0) { 320 /* Depending on error action, fail now or retry cluster */ 321 BlockErrorAction action = 322 backup_error_action(job, error_is_read, -ret); 323 if (action == BDRV_ACTION_REPORT) { 324 break; 325 } else { 326 start--; 327 continue; 328 } 329 } 330 } 331 } 332 333 notifier_with_return_remove(&before_write); 334 335 /* wait until pending backup_do_cow() calls have completed */ 336 qemu_co_rwlock_wrlock(&job->flush_rwlock); 337 qemu_co_rwlock_unlock(&job->flush_rwlock); 338 339 hbitmap_free(job->bitmap); 340 341 bdrv_iostatus_disable(target); 342 bdrv_unref(target); 343 344 block_job_completed(&job->common, ret); 345 } 346 347 void backup_start(BlockDriverState *bs, BlockDriverState *target, 348 int64_t speed, MirrorSyncMode sync_mode, 349 BlockdevOnError on_source_error, 350 BlockdevOnError on_target_error, 351 BlockDriverCompletionFunc *cb, void *opaque, 352 Error **errp) 353 { 354 int64_t len; 355 356 assert(bs); 357 assert(target); 358 assert(cb); 359 360 if ((on_source_error == BLOCKDEV_ON_ERROR_STOP || 361 on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) && 362 !bdrv_iostatus_is_enabled(bs)) { 363 error_set(errp, QERR_INVALID_PARAMETER, "on-source-error"); 364 return; 365 } 366 367 len = bdrv_getlength(bs); 368 if (len < 0) { 369 error_setg_errno(errp, -len, "unable to get length for '%s'", 370 bdrv_get_device_name(bs)); 371 return; 372 } 373 374 BackupBlockJob *job = block_job_create(&backup_job_driver, bs, speed, 375 cb, opaque, errp); 376 if (!job) { 377 return; 378 } 379 380 job->on_source_error = on_source_error; 381 job->on_target_error = on_target_error; 382 job->target = target; 383 job->sync_mode = sync_mode; 384 job->common.len = len; 385 job->common.co = qemu_coroutine_create(backup_run); 386 qemu_coroutine_enter(job->common.co, job); 387 } 388