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 int64_t sector_num = req->offset >> BDRV_SECTOR_BITS; 185 int nb_sectors = req->bytes >> BDRV_SECTOR_BITS; 186 187 assert((req->offset & (BDRV_SECTOR_SIZE - 1)) == 0); 188 assert((req->bytes & (BDRV_SECTOR_SIZE - 1)) == 0); 189 190 return backup_do_cow(req->bs, sector_num, nb_sectors, NULL); 191 } 192 193 static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) 194 { 195 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 196 197 if (speed < 0) { 198 error_set(errp, QERR_INVALID_PARAMETER, "speed"); 199 return; 200 } 201 ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME); 202 } 203 204 static void backup_iostatus_reset(BlockJob *job) 205 { 206 BackupBlockJob *s = container_of(job, BackupBlockJob, common); 207 208 bdrv_iostatus_reset(s->target); 209 } 210 211 static const BlockJobDriver backup_job_driver = { 212 .instance_size = sizeof(BackupBlockJob), 213 .job_type = BLOCK_JOB_TYPE_BACKUP, 214 .set_speed = backup_set_speed, 215 .iostatus_reset = backup_iostatus_reset, 216 }; 217 218 static BlockErrorAction backup_error_action(BackupBlockJob *job, 219 bool read, int error) 220 { 221 if (read) { 222 return block_job_error_action(&job->common, job->common.bs, 223 job->on_source_error, true, error); 224 } else { 225 return block_job_error_action(&job->common, job->target, 226 job->on_target_error, false, error); 227 } 228 } 229 230 static void coroutine_fn backup_run(void *opaque) 231 { 232 BackupBlockJob *job = opaque; 233 BlockDriverState *bs = job->common.bs; 234 BlockDriverState *target = job->target; 235 BlockdevOnError on_target_error = job->on_target_error; 236 NotifierWithReturn before_write = { 237 .notify = backup_before_write_notify, 238 }; 239 int64_t start, end; 240 int ret = 0; 241 242 QLIST_INIT(&job->inflight_reqs); 243 qemu_co_rwlock_init(&job->flush_rwlock); 244 245 start = 0; 246 end = DIV_ROUND_UP(job->common.len / BDRV_SECTOR_SIZE, 247 BACKUP_SECTORS_PER_CLUSTER); 248 249 job->bitmap = hbitmap_alloc(end, 0); 250 251 bdrv_set_enable_write_cache(target, true); 252 bdrv_set_on_error(target, on_target_error, on_target_error); 253 bdrv_iostatus_enable(target); 254 255 bdrv_add_before_write_notifier(bs, &before_write); 256 257 if (job->sync_mode == MIRROR_SYNC_MODE_NONE) { 258 while (!block_job_is_cancelled(&job->common)) { 259 /* Yield until the job is cancelled. We just let our before_write 260 * notify callback service CoW requests. */ 261 job->common.busy = false; 262 qemu_coroutine_yield(); 263 job->common.busy = true; 264 } 265 } else { 266 /* Both FULL and TOP SYNC_MODE's require copying.. */ 267 for (; start < end; start++) { 268 bool error_is_read; 269 270 if (block_job_is_cancelled(&job->common)) { 271 break; 272 } 273 274 /* we need to yield so that qemu_aio_flush() returns. 275 * (without, VM does not reboot) 276 */ 277 if (job->common.speed) { 278 uint64_t delay_ns = ratelimit_calculate_delay( 279 &job->limit, job->sectors_read); 280 job->sectors_read = 0; 281 block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, delay_ns); 282 } else { 283 block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, 0); 284 } 285 286 if (block_job_is_cancelled(&job->common)) { 287 break; 288 } 289 290 if (job->sync_mode == MIRROR_SYNC_MODE_TOP) { 291 int i, n; 292 int alloced = 0; 293 294 /* Check to see if these blocks are already in the 295 * backing file. */ 296 297 for (i = 0; i < BACKUP_SECTORS_PER_CLUSTER;) { 298 /* bdrv_is_allocated() only returns true/false based 299 * on the first set of sectors it comes across that 300 * are are all in the same state. 301 * For that reason we must verify each sector in the 302 * backup cluster length. We end up copying more than 303 * needed but at some point that is always the case. */ 304 alloced = 305 bdrv_is_allocated(bs, 306 start * BACKUP_SECTORS_PER_CLUSTER + i, 307 BACKUP_SECTORS_PER_CLUSTER - i, &n); 308 i += n; 309 310 if (alloced == 1) { 311 break; 312 } 313 } 314 315 /* If the above loop never found any sectors that are in 316 * the topmost image, skip this backup. */ 317 if (alloced == 0) { 318 continue; 319 } 320 } 321 /* FULL sync mode we copy the whole drive. */ 322 ret = backup_do_cow(bs, start * BACKUP_SECTORS_PER_CLUSTER, 323 BACKUP_SECTORS_PER_CLUSTER, &error_is_read); 324 if (ret < 0) { 325 /* Depending on error action, fail now or retry cluster */ 326 BlockErrorAction action = 327 backup_error_action(job, error_is_read, -ret); 328 if (action == BDRV_ACTION_REPORT) { 329 break; 330 } else { 331 start--; 332 continue; 333 } 334 } 335 } 336 } 337 338 notifier_with_return_remove(&before_write); 339 340 /* wait until pending backup_do_cow() calls have completed */ 341 qemu_co_rwlock_wrlock(&job->flush_rwlock); 342 qemu_co_rwlock_unlock(&job->flush_rwlock); 343 344 hbitmap_free(job->bitmap); 345 346 bdrv_iostatus_disable(target); 347 bdrv_unref(target); 348 349 block_job_completed(&job->common, ret); 350 } 351 352 void backup_start(BlockDriverState *bs, BlockDriverState *target, 353 int64_t speed, MirrorSyncMode sync_mode, 354 BlockdevOnError on_source_error, 355 BlockdevOnError on_target_error, 356 BlockDriverCompletionFunc *cb, void *opaque, 357 Error **errp) 358 { 359 int64_t len; 360 361 assert(bs); 362 assert(target); 363 assert(cb); 364 365 if ((on_source_error == BLOCKDEV_ON_ERROR_STOP || 366 on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) && 367 !bdrv_iostatus_is_enabled(bs)) { 368 error_set(errp, QERR_INVALID_PARAMETER, "on-source-error"); 369 return; 370 } 371 372 len = bdrv_getlength(bs); 373 if (len < 0) { 374 error_setg_errno(errp, -len, "unable to get length for '%s'", 375 bdrv_get_device_name(bs)); 376 return; 377 } 378 379 BackupBlockJob *job = block_job_create(&backup_job_driver, bs, speed, 380 cb, opaque, errp); 381 if (!job) { 382 return; 383 } 384 385 job->on_source_error = on_source_error; 386 job->on_target_error = on_target_error; 387 job->target = target; 388 job->sync_mode = sync_mode; 389 job->common.len = len; 390 job->common.co = qemu_coroutine_create(backup_run); 391 qemu_coroutine_enter(job->common.co, job); 392 } 393