block/backup.c

   1 /*
   2  * QEMU backup
   3  *
   4  * Copyright (C) 2013 Proxmox Server Solutions
   5  *
   6  * Authors:
   7  *  Dietmar Maurer ([email protected])
   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     RateLimit limit;
  41     BlockdevOnError on_source_error;
  42     BlockdevOnError on_target_error;
  43     CoRwlock flush_rwlock;
  44     uint64_t sectors_read;
  45     HBitmap *bitmap;
  46     QLIST_HEAD(, CowRequest) inflight_reqs;
  47 } BackupBlockJob;
  48
  49 /* See if in-flight requests overlap and wait for them to complete */
  50 static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job,
  51                                                        int64_t start,
  52                                                        int64_t end)
  53 {
  54     CowRequest *req;
  55     bool retry;
  56
  57     do {
  58         retry = false;
  59         QLIST_FOREACH(req, &job->inflight_reqs, list) {
  60             if (end > req->start && start < req->end) {
  61                 qemu_co_queue_wait(&req->wait_queue);
  62                 retry = true;
  63                 break;
  64             }
  65         }
  66     } while (retry);
  67 }
  68
  69 /* Keep track of an in-flight request */
  70 static void cow_request_begin(CowRequest *req, BackupBlockJob *job,
  71                                      int64_t start, int64_t end)
  72 {
  73     req->start = start;
  74     req->end = end;
  75     qemu_co_queue_init(&req->wait_queue);
  76     QLIST_INSERT_HEAD(&job->inflight_reqs, req, list);
  77 }
  78
  79 /* Forget about a completed request */
  80 static void cow_request_end(CowRequest *req)
  81 {
  82     QLIST_REMOVE(req, list);
  83     qemu_co_queue_restart_all(&req->wait_queue);
  84 }
  85
  86 static int coroutine_fn backup_do_cow(BlockDriverState *bs,
  87                                       int64_t sector_num, int nb_sectors,
  88                                       bool *error_is_read)
  89 {
  90     BackupBlockJob *job = (BackupBlockJob *)bs->job;
  91     CowRequest cow_request;
  92     struct iovec iov;
  93     QEMUIOVector bounce_qiov;
  94     void *bounce_buffer = NULL;
  95     int ret = 0;
  96     int64_t start, end;
  97     int n;
  98
  99     qemu_co_rwlock_rdlock(&job->flush_rwlock);
 100
 101     start = sector_num / BACKUP_SECTORS_PER_CLUSTER;
 102     end = DIV_ROUND_UP(sector_num + nb_sectors, BACKUP_SECTORS_PER_CLUSTER);
 103
 104     trace_backup_do_cow_enter(job, start, sector_num, nb_sectors);
 105
 106     wait_for_overlapping_requests(job, start, end);
 107     cow_request_begin(&cow_request, job, start, end);
 108
 109     for (; start < end; start++) {
 110         if (hbitmap_get(job->bitmap, start)) {
 111             trace_backup_do_cow_skip(job, start);
 112             continue; /* already copied */
 113         }
 114
 115         trace_backup_do_cow_process(job, start);
 116
 117         n = MIN(BACKUP_SECTORS_PER_CLUSTER,
 118                 job->common.len / BDRV_SECTOR_SIZE -
 119                 start * BACKUP_SECTORS_PER_CLUSTER);
 120
 121         if (!bounce_buffer) {
 122             bounce_buffer = qemu_blockalign(bs, BACKUP_CLUSTER_SIZE);
 123         }
 124         iov.iov_base = bounce_buffer;
 125         iov.iov_len = n * BDRV_SECTOR_SIZE;
 126         qemu_iovec_init_external(&bounce_qiov, &iov, 1);
 127
 128         ret = bdrv_co_readv(bs, start * BACKUP_SECTORS_PER_CLUSTER, n,
 129                             &bounce_qiov);
 130         if (ret < 0) {
 131             trace_backup_do_cow_read_fail(job, start, ret);
 132             if (error_is_read) {
 133                 *error_is_read = true;
 134             }
 135             goto out;
 136         }
 137
 138         if (buffer_is_zero(iov.iov_base, iov.iov_len)) {
 139             ret = bdrv_co_write_zeroes(job->target,
 140                                        start * BACKUP_SECTORS_PER_CLUSTER, n);
 141         } else {
 142             ret = bdrv_co_writev(job->target,
 143                                  start * BACKUP_SECTORS_PER_CLUSTER, n,
 144                                  &bounce_qiov);
 145         }
 146         if (ret < 0) {
 147             trace_backup_do_cow_write_fail(job, start, ret);
 148             if (error_is_read) {
 149                 *error_is_read = false;
 150             }
 151             goto out;
 152         }
 153
 154         hbitmap_set(job->bitmap, start, 1);
 155
 156         /* Publish progress, guest I/O counts as progress too.  Note that the
 157          * offset field is an opaque progress value, it is not a disk offset.
 158          */
 159         job->sectors_read += n;
 160         job->common.offset += n * BDRV_SECTOR_SIZE;
 161     }
 162
 163 out:
 164     if (bounce_buffer) {
 165         qemu_vfree(bounce_buffer);
 166     }
 167
 168     cow_request_end(&cow_request);
 169
 170     trace_backup_do_cow_return(job, sector_num, nb_sectors, ret);
 171
 172     qemu_co_rwlock_unlock(&job->flush_rwlock);
 173
 174     return ret;
 175 }
 176
 177 static int coroutine_fn backup_before_write_notify(
 178         NotifierWithReturn *notifier,
 179         void *opaque)
 180 {
 181     BdrvTrackedRequest *req = opaque;
 182
 183     return backup_do_cow(req->bs, req->sector_num, req->nb_sectors, NULL);
 184 }
 185
 186 static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp)
 187 {
 188     BackupBlockJob *s = container_of(job, BackupBlockJob, common);
 189
 190     if (speed < 0) {
 191         error_set(errp, QERR_INVALID_PARAMETER, "speed");
 192         return;
 193     }
 194     ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
 195 }
 196
 197 static void backup_iostatus_reset(BlockJob *job)
 198 {
 199     BackupBlockJob *s = container_of(job, BackupBlockJob, common);
 200
 201     bdrv_iostatus_reset(s->target);
 202 }
 203
 204 static const BlockJobType backup_job_type = {
 205     .instance_size  = sizeof(BackupBlockJob),
 206     .job_type       = "backup",
 207     .set_speed      = backup_set_speed,
 208     .iostatus_reset = backup_iostatus_reset,
 209 };
 210
 211 static BlockErrorAction backup_error_action(BackupBlockJob *job,
 212                                             bool read, int error)
 213 {
 214     if (read) {
 215         return block_job_error_action(&job->common, job->common.bs,
 216                                       job->on_source_error, true, error);
 217     } else {
 218         return block_job_error_action(&job->common, job->target,
 219                                       job->on_target_error, false, error);
 220     }
 221 }
 222
 223 static void coroutine_fn backup_run(void *opaque)
 224 {
 225     BackupBlockJob *job = opaque;
 226     BlockDriverState *bs = job->common.bs;
 227     BlockDriverState *target = job->target;
 228     BlockdevOnError on_target_error = job->on_target_error;
 229     NotifierWithReturn before_write = {
 230         .notify = backup_before_write_notify,
 231     };
 232     int64_t start, end;
 233     int ret = 0;
 234
 235     QLIST_INIT(&job->inflight_reqs);
 236     qemu_co_rwlock_init(&job->flush_rwlock);
 237
 238     start = 0;
 239     end = DIV_ROUND_UP(job->common.len / BDRV_SECTOR_SIZE,
 240                        BACKUP_SECTORS_PER_CLUSTER);
 241
 242     job->bitmap = hbitmap_alloc(end, 0);
 243
 244     bdrv_set_enable_write_cache(target, true);
 245     bdrv_set_on_error(target, on_target_error, on_target_error);
 246     bdrv_iostatus_enable(target);
 247
 248     bdrv_add_before_write_notifier(bs, &before_write);
 249
 250     for (; start < end; start++) {
 251         bool error_is_read;
 252
 253         if (block_job_is_cancelled(&job->common)) {
 254             break;
 255         }
 256
 257         /* we need to yield so that qemu_aio_flush() returns.
 258          * (without, VM does not reboot)
 259          */
 260         if (job->common.speed) {
 261             uint64_t delay_ns = ratelimit_calculate_delay(
 262                 &job->limit, job->sectors_read);
 263             job->sectors_read = 0;
 264             block_job_sleep_ns(&job->common, rt_clock, delay_ns);
 265         } else {
 266             block_job_sleep_ns(&job->common, rt_clock, 0);
 267         }
 268
 269         if (block_job_is_cancelled(&job->common)) {
 270             break;
 271         }
 272
 273         ret = backup_do_cow(bs, start * BACKUP_SECTORS_PER_CLUSTER,
 274                             BACKUP_SECTORS_PER_CLUSTER, &error_is_read);
 275         if (ret < 0) {
 276             /* Depending on error action, fail now or retry cluster */
 277             BlockErrorAction action =
 278                 backup_error_action(job, error_is_read, -ret);
 279             if (action == BDRV_ACTION_REPORT) {
 280                 break;
 281             } else {
 282                 start--;
 283                 continue;
 284             }
 285         }
 286     }
 287
 288     notifier_with_return_remove(&before_write);
 289
 290     /* wait until pending backup_do_cow() calls have completed */
 291     qemu_co_rwlock_wrlock(&job->flush_rwlock);
 292     qemu_co_rwlock_unlock(&job->flush_rwlock);
 293
 294     hbitmap_free(job->bitmap);
 295
 296     bdrv_iostatus_disable(target);
 297     bdrv_delete(target);
 298
 299     block_job_completed(&job->common, ret);
 300 }
 301
 302 void backup_start(BlockDriverState *bs, BlockDriverState *target,
 303                   int64_t speed,
 304                   BlockdevOnError on_source_error,
 305                   BlockdevOnError on_target_error,
 306                   BlockDriverCompletionFunc *cb, void *opaque,
 307                   Error **errp)
 308 {
 309     int64_t len;
 310
 311     assert(bs);
 312     assert(target);
 313     assert(cb);
 314
 315     if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
 316          on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
 317         !bdrv_iostatus_is_enabled(bs)) {
 318         error_set(errp, QERR_INVALID_PARAMETER, "on-source-error");
 319         return;
 320     }
 321
 322     len = bdrv_getlength(bs);
 323     if (len < 0) {
 324         error_setg_errno(errp, -len, "unable to get length for '%s'",
 325                          bdrv_get_device_name(bs));
 326         return;
 327     }
 328
 329     BackupBlockJob *job = block_job_create(&backup_job_type, bs, speed,
 330                                            cb, opaque, errp);
 331     if (!job) {
 332         return;
 333     }
 334
 335     job->on_source_error = on_source_error;
 336     job->on_target_error = on_target_error;
 337     job->target = target;
 338     job->common.len = len;
 339     job->common.co = qemu_coroutine_create(backup_run);
 340     qemu_coroutine_enter(job->common.co, job);
 341 }