debian/patches/0002-add-basic-backup-support-to-block-driver.patch

   1 From 577b000e947d817cf4e0189615c0d0257cb20259 Mon Sep 17 00:00:00 2001
   2 From: Dietmar Maurer <dietmar@proxmox.com>
   3 Date: Tue, 13 Nov 2012 10:03:52 +0100
   4 Subject: [PATCH v3 2/7] add basic backup support to block driver
   5
   6 Function backup_job_create() creates a block job to backup a block device.
   7 The coroutine is started with backup_job_start().
   8
   9 We call backup_do_cow() for each write during backup. That function
  10 reads the original data and pass it to backup_dump_cb().
  11
  12 The tracked_request infrastructure is used to serialize access.
  13
  14 Currently backup cluster size is hardcoded to 65536 bytes.
  15
  16 Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>
  17 ---
  18  Makefile.objs |    1 +
  19  backup.c      |  308 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  20  backup.h      |   32 ++++++
  21  block.c       |   71 ++++++++++++-
  22  block.h       |    2 +
  23  blockjob.h    |   10 ++
  24  6 files changed, 418 insertions(+), 6 deletions(-)
  25  create mode 100644 backup.c
  26  create mode 100644 backup.h
  27
  28 diff --git a/Makefile.objs b/Makefile.objs
  29 index 3c7abca..cb46be5 100644
  30 --- a/Makefile.objs
  31 +++ b/Makefile.objs
  32 @@ -48,6 +48,7 @@ coroutine-obj-$(CONFIG_WIN32) += coroutine-win32.o
  33  block-obj-y = iov.o cache-utils.o qemu-option.o module.o async.o
  34  block-obj-y += nbd.o block.o blockjob.o aes.o qemu-config.o
  35  block-obj-y += thread-pool.o qemu-progress.o qemu-sockets.o uri.o notify.o
  36 +block-obj-y += backup.o
  37  block-obj-y += $(coroutine-obj-y) $(qobject-obj-y) $(version-obj-y)
  38  block-obj-$(CONFIG_POSIX) += event_notifier-posix.o aio-posix.o
  39  block-obj-$(CONFIG_WIN32) += event_notifier-win32.o aio-win32.o
  40 diff --git a/backup.c b/backup.c
  41 new file mode 100644
  42 index 0000000..2c13e21
  43 --- /dev/null
  44 +++ b/backup.c
  45 @@ -0,0 +1,308 @@
  46 +/*
  47 + * QEMU backup
  48 + *
  49 + * Copyright (C) 2012 Proxmox Server Solutions
  50 + *
  51 + * Authors:
  52 + *  Dietmar Maurer (dietmar@proxmox.com)
  53 + *
  54 + * This work is licensed under the terms of the GNU GPL, version 2 or later.
  55 + * See the COPYING file in the top-level directory.
  56 + *
  57 + */
  58 +
  59 +#include <stdio.h>
  60 +#include <errno.h>
  61 +#include <unistd.h>
  62 +
  63 +#include "block.h"
  64 +#include "block_int.h"
  65 +#include "blockjob.h"
  66 +#include "backup.h"
  67 +
  68 +#define DEBUG_BACKUP 0
  69 +
  70 +#define DPRINTF(fmt, ...) \
  71 +    do { if (DEBUG_BACKUP) { printf("backup: " fmt, ## __VA_ARGS__); } } \
  72 +    while (0)
  73 +
  74 +
  75 +#define BITS_PER_LONG  (sizeof(unsigned long) * 8)
  76 +
  77 +typedef struct BackupBlockJob {
  78 +    BlockJob common;
  79 +    unsigned long *bitmap;
  80 +    int bitmap_size;
  81 +    BackupDumpFunc *backup_dump_cb;
  82 +    BlockDriverCompletionFunc *backup_complete_cb;
  83 +    void *opaque;
  84 +} BackupBlockJob;
  85 +
  86 +static int backup_get_bitmap(BackupBlockJob *job, int64_t cluster_num)
  87 +{
  88 +    assert(job);
  89 +    assert(job->bitmap);
  90 +
  91 +    unsigned long val, idx, bit;
  92 +
  93 +    idx = cluster_num / BITS_PER_LONG;
  94 +
  95 +    assert(job->bitmap_size > idx);
  96 +
  97 +    bit = cluster_num % BITS_PER_LONG;
  98 +    val = job->bitmap[idx];
  99 +
 100 +    return !!(val & (1UL << bit));
 101 +}
 102 +
 103 +static void backup_set_bitmap(BackupBlockJob *job, int64_t cluster_num,
 104 +                              int dirty)
 105 +{
 106 +    assert(job);
 107 +    assert(job->bitmap);
 108 +
 109 +    unsigned long val, idx, bit;
 110 +
 111 +    idx = cluster_num / BITS_PER_LONG;
 112 +
 113 +    assert(job->bitmap_size > idx);
 114 +
 115 +    bit = cluster_num % BITS_PER_LONG;
 116 +    val = job->bitmap[idx];
 117 +    if (dirty) {
 118 +        if (!(val & (1UL << bit))) {
 119 +            val |= 1UL << bit;
 120 +        }
 121 +    } else {
 122 +        if (val & (1UL << bit)) {
 123 +            val &= ~(1UL << bit);
 124 +        }
 125 +    }
 126 +    job->bitmap[idx] = val;
 127 +}
 128 +
 129 +static int backup_in_progress_count;
 130 +
 131 +static int coroutine_fn backup_do_cow(BlockDriverState *bs,
 132 +                                      int64_t sector_num, int nb_sectors)
 133 +{
 134 +    assert(bs);
 135 +    BackupBlockJob *job = (BackupBlockJob *)bs->job;
 136 +    assert(job);
 137 +
 138 +    BlockDriver *drv = bs->drv;
 139 +    struct iovec iov;
 140 +    QEMUIOVector bounce_qiov;
 141 +    void *bounce_buffer = NULL;
 142 +    int ret = 0;
 143 +
 144 +    backup_in_progress_count++;
 145 +
 146 +    int64_t start, end;
 147 +
 148 +    start = sector_num / BACKUP_BLOCKS_PER_CLUSTER;
 149 +    end = (sector_num + nb_sectors + BACKUP_BLOCKS_PER_CLUSTER - 1) /
 150 +        BACKUP_BLOCKS_PER_CLUSTER;
 151 +
 152 +    DPRINTF("brdv_co_backup_cow enter %s C%zd %zd %d\n",
 153 +            bdrv_get_device_name(bs), start, sector_num, nb_sectors);
 154 +
 155 +    for (; start < end; start++) {
 156 +        if (backup_get_bitmap(job, start)) {
 157 +            DPRINTF("brdv_co_backup_cow skip C%zd\n", start);
 158 +            continue; /* already copied */
 159 +        }
 160 +
 161 +        /* immediately set bitmap (avoid coroutine race) */
 162 +        backup_set_bitmap(job, start, 1);
 163 +
 164 +        DPRINTF("brdv_co_backup_cow C%zd\n", start);
 165 +
 166 +        if (!bounce_buffer) {
 167 +            iov.iov_len = BACKUP_CLUSTER_SIZE;
 168 +            iov.iov_base = bounce_buffer = qemu_blockalign(bs, iov.iov_len);
 169 +            qemu_iovec_init_external(&bounce_qiov, &iov, 1);
 170 +        }
 171 +
 172 +        ret = drv->bdrv_co_readv(bs, start * BACKUP_BLOCKS_PER_CLUSTER,
 173 +                                 BACKUP_BLOCKS_PER_CLUSTER,
 174 +                                 &bounce_qiov);
 175 +        if (ret < 0) {
 176 +            DPRINTF("brdv_co_backup_cow bdrv_read C%zd failed\n", start);
 177 +            goto out;
 178 +        }
 179 +
 180 +        ret = job->backup_dump_cb(job->opaque, bs, start, bounce_buffer);
 181 +        if (ret < 0) {
 182 +            DPRINTF("brdv_co_backup_cow dump_cluster_cb C%zd failed\n", start);
 183 +            goto out;
 184 +        }
 185 +
 186 +        DPRINTF("brdv_co_backup_cow done C%zd\n", start);
 187 +    }
 188 +
 189 +out:
 190 +    if (bounce_buffer) {
 191 +        qemu_vfree(bounce_buffer);
 192 +    }
 193 +
 194 +    backup_in_progress_count--;
 195 +
 196 +    return ret;
 197 +}
 198 +
 199 +static int coroutine_fn backup_before_read(BlockDriverState *bs,
 200 +                                           int64_t sector_num,
 201 +                                           int nb_sectors, QEMUIOVector *qiov)
 202 +{
 203 +    return backup_do_cow(bs, sector_num, nb_sectors);
 204 +}
 205 +
 206 +static int coroutine_fn backup_before_write(BlockDriverState *bs,
 207 +                                            int64_t sector_num,
 208 +                                            int nb_sectors, QEMUIOVector *qiov)
 209 +{
 210 +    return backup_do_cow(bs, sector_num, nb_sectors);
 211 +}
 212 +
 213 +
 214 +static BlockJobType backup_job_type = {
 215 +    .instance_size = sizeof(BackupBlockJob),
 216 +    .before_read = backup_before_read,
 217 +    .before_write = backup_before_write,
 218 +    .job_type      = "backup",
 219 +};
 220 +
 221 +static void coroutine_fn backup_run(void *opaque)
 222 +{
 223 +    BackupBlockJob *job = opaque;
 224 +    BlockDriverState *bs = job->common.bs;
 225 +    assert(bs);
 226 +
 227 +    int64_t start, end;
 228 +
 229 +    start = 0;
 230 +    end = (bs->total_sectors + BACKUP_BLOCKS_PER_CLUSTER - 1) /
 231 +        BACKUP_BLOCKS_PER_CLUSTER;
 232 +
 233 +    DPRINTF("backup_run start %s %zd %zd\n", bdrv_get_device_name(bs),
 234 +            start, end);
 235 +
 236 +    int ret = 0;
 237 +
 238 +    for (; start < end; start++) {
 239 +        if (block_job_is_cancelled(&job->common)) {
 240 +            ret = -1;
 241 +            break;
 242 +        }
 243 +
 244 +        if (backup_get_bitmap(job, start)) {
 245 +            continue; /* already copied */
 246 +        }
 247 +
 248 +        /* we need to yield so that qemu_aio_flush() returns.
 249 +         * (without, VM does not reboot)
 250 +         * todo: can we avoid that?
 251 +        * Note: use 1000 instead of 0 (0 priorize this task too much)
 252 +         */
 253 +        block_job_sleep_ns(&job->common, rt_clock, 1000);
 254 +        if (block_job_is_cancelled(&job->common)) {
 255 +            ret = -1;
 256 +            break;
 257 +        }
 258 +        DPRINTF("backup_run loop C%zd\n", start);
 259 +
 260 +        /**
 261 +         * This triggers a cluster copy
 262 +         * Note: avoid direct call to brdv_co_backup_cow, because
 263 +         * this does not call tracked_request_begin()
 264 +         */
 265 +        ret = bdrv_co_backup(bs, start*BACKUP_BLOCKS_PER_CLUSTER, 1);
 266 +        if (ret < 0) {
 267 +            break;
 268 +        }
 269 +        /* Publish progress */
 270 +        job->common.offset += BACKUP_CLUSTER_SIZE;
 271 +    }
 272 +
 273 +    while (backup_in_progress_count > 0) {
 274 +        DPRINTF("backup_run backup_in_progress_count != 0 (%d)",
 275 +                backup_in_progress_count);
 276 +        co_sleep_ns(rt_clock, 10000);
 277 +    }
 278 +
 279 +    DPRINTF("backup_run complete %d\n", ret);
 280 +    block_job_completed(&job->common, ret);
 281 +}
 282 +
 283 +static void backup_job_cleanup_cb(void *opaque, int ret)
 284 +{
 285 +    BlockDriverState *bs = opaque;
 286 +    assert(bs);
 287 +    BackupBlockJob *job = (BackupBlockJob *)bs->job;
 288 +    assert(job);
 289 +
 290 +    DPRINTF("backup_job_cleanup_cb start %d\n", ret);
 291 +
 292 +    job->backup_complete_cb(job->opaque, ret);
 293 +
 294 +    DPRINTF("backup_job_cleanup_cb end\n");
 295 +
 296 +    g_free(job->bitmap);
 297 +}
 298 +
 299 +void
 300 +backup_job_start(BlockDriverState *bs)
 301 +{
 302 +    assert(bs);
 303 +    assert(bs->job);
 304 +    assert(bs->job->co == NULL);
 305 +
 306 +    bs->job->co = qemu_coroutine_create(backup_run);
 307 +    qemu_coroutine_enter(bs->job->co, bs->job);
 308 +}
 309 +
 310 +int
 311 +backup_job_create(BlockDriverState *bs, BackupDumpFunc *backup_dump_cb,
 312 +                  BlockDriverCompletionFunc *backup_complete_cb,
 313 +                  void *opaque)
 314 +{
 315 +    assert(bs);
 316 +    assert(backup_dump_cb);
 317 +    assert(backup_complete_cb);
 318 +
 319 +    if (bs->job) {
 320 +        DPRINTF("bdrv_backup_init failed - running job on %s\n",
 321 +                bdrv_get_device_name(bs));
 322 +        return -1;
 323 +    }
 324 +
 325 +    int64_t bitmap_size;
 326 +    const char *devname = bdrv_get_device_name(bs);
 327 +
 328 +    if (!devname || !devname[0]) {
 329 +        return -1;
 330 +    }
 331 +
 332 +    DPRINTF("bdrv_backup_init %s\n", bdrv_get_device_name(bs));
 333 +
 334 +    Error *errp;
 335 +    BackupBlockJob *job = block_job_create(&backup_job_type, bs, 0,
 336 +                                           backup_job_cleanup_cb, bs, &errp);
 337 +
 338 +    job->common.cluster_size = BACKUP_CLUSTER_SIZE;
 339 +
 340 +    bitmap_size = bs->total_sectors +
 341 +        BACKUP_BLOCKS_PER_CLUSTER * BITS_PER_LONG - 1;
 342 +    bitmap_size /= BACKUP_BLOCKS_PER_CLUSTER * BITS_PER_LONG;
 343 +
 344 +    job->backup_dump_cb = backup_dump_cb;
 345 +    job->backup_complete_cb = backup_complete_cb;
 346 +    job->opaque = opaque;
 347 +    job->bitmap_size = bitmap_size;
 348 +    job->bitmap = g_new0(unsigned long, bitmap_size);
 349 +
 350 +    job->common.len = bs->total_sectors*BDRV_SECTOR_SIZE;
 351 +
 352 +    return 0;
 353 +}
 354 diff --git a/backup.h b/backup.h
 355 new file mode 100644
 356 index 0000000..87b9942
 357 --- /dev/null
 358 +++ b/backup.h
 359 @@ -0,0 +1,32 @@
 360 +/*
 361 + * QEMU backup related definitions
 362 + *
 363 + * Copyright (C) Proxmox Server Solutions
 364 + *
 365 + * Authors:
 366 + *  Dietmar Maurer (dietmar@proxmox.com)
 367 + *
 368 + * This work is licensed under the terms of the GNU GPL, version 2 or later.
 369 + * See the COPYING file in the top-level directory.
 370 + *
 371 + */
 372 +
 373 +#ifndef QEMU_BACKUP_H
 374 +#define QEMU_BACKUP_H
 375 +
 376 +#include <uuid/uuid.h>
 377 +
 378 +#define BACKUP_CLUSTER_BITS 16
 379 +#define BACKUP_CLUSTER_SIZE (1<<BACKUP_CLUSTER_BITS)
 380 +#define BACKUP_BLOCKS_PER_CLUSTER (BACKUP_CLUSTER_SIZE/BDRV_SECTOR_SIZE)
 381 +
 382 +typedef int BackupDumpFunc(void *opaque, BlockDriverState *bs,
 383 +                           int64_t cluster_num, unsigned char *buf);
 384 +
 385 +void backup_job_start(BlockDriverState *bs);
 386 +
 387 +int backup_job_create(BlockDriverState *bs, BackupDumpFunc *backup_dump_cb,
 388 +                     BlockDriverCompletionFunc *backup_complete_cb,
 389 +                     void *opaque);
 390 +
 391 +#endif /* QEMU_BACKUP_H */
 392 diff --git a/block.c b/block.c
 393 index c05875f..4de7fbd 100644
 394 --- a/block.c
 395 +++ b/block.c
 396 @@ -54,6 +54,7 @@
 397  typedef enum {
 398      BDRV_REQ_COPY_ON_READ = 0x1,
 399      BDRV_REQ_ZERO_WRITE   = 0x2,
 400 +    BDRV_REQ_BACKUP_ONLY  = 0x4,
 401  } BdrvRequestFlags;
 402
 403  static void bdrv_dev_change_media_cb(BlockDriverState *bs, bool load);
 404 @@ -1542,7 +1543,7 @@ int bdrv_commit(BlockDriverState *bs)
 405
 406      if (!drv)
 407          return -ENOMEDIUM;
 408 -
 409 +
 410      if (!bs->backing_hd) {
 411          return -ENOTSUP;
 412      }
 413 @@ -1679,6 +1680,22 @@ static void round_to_clusters(BlockDriverState *bs,
 414      }
 415  }
 416
 417 +/**
 418 + * Round a region to job cluster boundaries
 419 + */
 420 +static void round_to_job_clusters(BlockDriverState *bs,
 421 +                                  int64_t sector_num, int nb_sectors,
 422 +                                  int job_cluster_size,
 423 +                                  int64_t *cluster_sector_num,
 424 +                                  int *cluster_nb_sectors)
 425 +{
 426 +    int64_t c = job_cluster_size/BDRV_SECTOR_SIZE;
 427 +
 428 +    *cluster_sector_num = QEMU_ALIGN_DOWN(sector_num, c);
 429 +    *cluster_nb_sectors = QEMU_ALIGN_UP(sector_num - *cluster_sector_num +
 430 +                                        nb_sectors, c);
 431 +}
 432 +
 433  static bool tracked_request_overlaps(BdrvTrackedRequest *req,
 434                                       int64_t sector_num, int nb_sectors) {
 435      /*        aaaa   bbbb */
 436 @@ -1693,7 +1710,9 @@ static bool tracked_request_overlaps(BdrvTrackedRequest *req,
 437  }
 438
 439  static void coroutine_fn wait_for_overlapping_requests(BlockDriverState *bs,
 440 -        int64_t sector_num, int nb_sectors)
 441 +                                                       int64_t sector_num,
 442 +                                                       int nb_sectors,
 443 +                                                       int job_cluster_size)
 444  {
 445      BdrvTrackedRequest *req;
 446      int64_t cluster_sector_num;
 447 @@ -1709,6 +1728,11 @@ static void coroutine_fn wait_for_overlapping_requests(BlockDriverState *bs,
 448      round_to_clusters(bs, sector_num, nb_sectors,
 449                        &cluster_sector_num, &cluster_nb_sectors);
 450
 451 +    if (job_cluster_size) {
 452 +        round_to_job_clusters(bs, sector_num, nb_sectors, job_cluster_size,
 453 +                              &cluster_sector_num, &cluster_nb_sectors);
 454 +    }
 455 +
 456      do {
 457          retry = false;
 458          QLIST_FOREACH(req, &bs->tracked_requests, list) {
 459 @@ -2278,12 +2302,24 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
 460          bs->copy_on_read_in_flight++;
 461      }
 462
 463 -    if (bs->copy_on_read_in_flight) {
 464 -        wait_for_overlapping_requests(bs, sector_num, nb_sectors);
 465 +    int job_cluster_size = bs->job && bs->job->cluster_size ?
 466 +        bs->job->cluster_size : 0;
 467 +
 468 +    if (bs->copy_on_read_in_flight || job_cluster_size) {
 469 +        wait_for_overlapping_requests(bs, sector_num, nb_sectors,
 470 +                                      job_cluster_size);
 471      }
 472
 473      tracked_request_begin(&req, bs, sector_num, nb_sectors, false);
 474
 475 +    if (bs->job && bs->job->job_type->before_read) {
 476 +        ret = bs->job->job_type->before_read(bs, sector_num, nb_sectors, qiov);
 477 +        if ((ret < 0) || (flags & BDRV_REQ_BACKUP_ONLY)) {
 478 +            /* Note: We do not return any data to the caller */
 479 +            goto out;
 480 +        }
 481 +    }
 482 +
 483      if (flags & BDRV_REQ_COPY_ON_READ) {
 484          int pnum;
 485
 486 @@ -2327,6 +2363,17 @@ int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
 487                              BDRV_REQ_COPY_ON_READ);
 488  }
 489
 490 +int coroutine_fn bdrv_co_backup(BlockDriverState *bs,
 491 +    int64_t sector_num, int nb_sectors)
 492 +{
 493 +    if (!bs->job) {
 494 +        return -ENOTSUP;
 495 +    }
 496 +
 497 +    return bdrv_co_do_readv(bs, sector_num, nb_sectors, NULL,
 498 +                            BDRV_REQ_BACKUP_ONLY);
 499 +}
 500 +
 501  static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
 502      int64_t sector_num, int nb_sectors)
 503  {
 504 @@ -2384,12 +2431,23 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
 505          bdrv_io_limits_intercept(bs, true, nb_sectors);
 506      }
 507
 508 -    if (bs->copy_on_read_in_flight) {
 509 -        wait_for_overlapping_requests(bs, sector_num, nb_sectors);
 510 +    int job_cluster_size = bs->job && bs->job->cluster_size ?
 511 +        bs->job->cluster_size : 0;
 512 +
 513 +    if (bs->copy_on_read_in_flight || job_cluster_size) {
 514 +        wait_for_overlapping_requests(bs, sector_num, nb_sectors,
 515 +                                      job_cluster_size);
 516      }
 517
 518      tracked_request_begin(&req, bs, sector_num, nb_sectors, true);
 519
 520 +    if (bs->job && bs->job->job_type->before_write) {
 521 +        ret = bs->job->job_type->before_write(bs, sector_num, nb_sectors, qiov);
 522 +        if (ret < 0) {
 523 +            goto out;
 524 +        }
 525 +    }
 526 +
 527      if (flags & BDRV_REQ_ZERO_WRITE) {
 528          ret = bdrv_co_do_write_zeroes(bs, sector_num, nb_sectors);
 529      } else {
 530 @@ -2408,6 +2466,7 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
 531          bs->wr_highest_sector = sector_num + nb_sectors - 1;
 532      }
 533
 534 +out:
 535      tracked_request_end(&req);
 536
 537      return ret;
 538 diff --git a/block.h b/block.h
 539 index 722c620..94e5903 100644
 540 --- a/block.h
 541 +++ b/block.h
 542 @@ -172,6 +172,8 @@ int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num,
 543      int nb_sectors, QEMUIOVector *qiov);
 544  int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
 545      int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
 546 +int coroutine_fn bdrv_co_backup(BlockDriverState *bs,
 547 +    int64_t sector_num, int nb_sectors);
 548  int coroutine_fn bdrv_co_writev(BlockDriverState *bs, int64_t sector_num,
 549      int nb_sectors, QEMUIOVector *qiov);
 550  /*
 551 diff --git a/blockjob.h b/blockjob.h
 552 index 3792b73..6621173 100644
 553 --- a/blockjob.h
 554 +++ b/blockjob.h
 555 @@ -50,6 +50,13 @@ typedef struct BlockJobType {
 556       * manually.
 557       */
 558      void (*complete)(BlockJob *job, Error **errp);
 559 +
 560 +    /** tracked requests */
 561 +    int coroutine_fn (*before_read)(BlockDriverState *bs, int64_t sector_num,
 562 +                                    int nb_sectors, QEMUIOVector *qiov);
 563 +    int coroutine_fn (*before_write)(BlockDriverState *bs, int64_t sector_num,
 564 +                                     int nb_sectors, QEMUIOVector *qiov);
 565 +
 566  } BlockJobType;
 567
 568  /**
 569 @@ -103,6 +110,9 @@ struct BlockJob {
 570      /** Speed that was set with @block_job_set_speed.  */
 571      int64_t speed;
 572
 573 +    /** tracked requests */
 574 +    int cluster_size;
 575 +
 576      /** The completion function that will be called when the job completes.  */
 577      BlockDriverCompletionFunc *cb;
 578
 579 --
 580 1.7.2.5
 581