block/commit.c

   1 /*
   2  * Live block commit
   3  *
   4  * Copyright Red Hat, Inc. 2012
   5  *
   6  * Authors:
   7  *  Jeff Cody   <jcody@redhat.com>
   8  *  Based on stream.c by Stefan Hajnoczi
   9  *
  10  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  11  * See the COPYING.LIB file in the top-level directory.
  12  *
  13  */
  14
  15 #include "qemu/osdep.h"
  16 #include "trace.h"
  17 #include "block/block_int.h"
  18 #include "block/blockjob.h"
  19 #include "qapi/error.h"
  20 #include "qapi/qmp/qerror.h"
  21 #include "qemu/ratelimit.h"
  22 #include "sysemu/block-backend.h"
  23
  24 enum {
  25     /*
  26      * Size of data buffer for populating the image file.  This should be large
  27      * enough to process multiple clusters in a single call, so that populating
  28      * contiguous regions of the image is efficient.
  29      */
  30     COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */
  31 };
  32
  33 #define SLICE_TIME 100000000ULL /* ns */
  34
  35 typedef struct CommitBlockJob {
  36     BlockJob common;
  37     RateLimit limit;
  38     BlockDriverState *active;
  39     BlockBackend *top;
  40     BlockBackend *base;
  41     BlockdevOnError on_error;
  42     int base_flags;
  43     int orig_overlay_flags;
  44     char *backing_file_str;
  45 } CommitBlockJob;
  46
  47 static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
  48                                         int64_t sector_num, int nb_sectors,
  49                                         void *buf)
  50 {
  51     int ret = 0;
  52     QEMUIOVector qiov;
  53     struct iovec iov = {
  54         .iov_base = buf,
  55         .iov_len = nb_sectors * BDRV_SECTOR_SIZE,
  56     };
  57
  58     qemu_iovec_init_external(&qiov, &iov, 1);
  59
  60     ret = blk_co_preadv(bs, sector_num * BDRV_SECTOR_SIZE,
  61                         qiov.size, &qiov, 0);
  62     if (ret < 0) {
  63         return ret;
  64     }
  65
  66     ret = blk_co_pwritev(base, sector_num * BDRV_SECTOR_SIZE,
  67                          qiov.size, &qiov, 0);
  68     if (ret < 0) {
  69         return ret;
  70     }
  71
  72     return 0;
  73 }
  74
  75 typedef struct {
  76     int ret;
  77 } CommitCompleteData;
  78
  79 static void commit_complete(BlockJob *job, void *opaque)
  80 {
  81     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
  82     CommitCompleteData *data = opaque;
  83     BlockDriverState *active = s->active;
  84     BlockDriverState *top = blk_bs(s->top);
  85     BlockDriverState *base = blk_bs(s->base);
  86     BlockDriverState *overlay_bs;
  87     int ret = data->ret;
  88
  89     if (!block_job_is_cancelled(&s->common) && ret == 0) {
  90         /* success */
  91         ret = bdrv_drop_intermediate(active, top, base, s->backing_file_str);
  92     }
  93
  94     /* restore base open flags here if appropriate (e.g., change the base back
  95      * to r/o). These reopens do not need to be atomic, since we won't abort
  96      * even on failure here */
  97     if (s->base_flags != bdrv_get_flags(base)) {
  98         bdrv_reopen(base, s->base_flags, NULL);
  99     }
 100     overlay_bs = bdrv_find_overlay(active, top);
 101     if (overlay_bs && s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) {
 102         bdrv_reopen(overlay_bs, s->orig_overlay_flags, NULL);
 103     }
 104     g_free(s->backing_file_str);
 105     blk_unref(s->top);
 106     blk_unref(s->base);
 107     block_job_completed(&s->common, ret);
 108     g_free(data);
 109 }
 110
 111 static void coroutine_fn commit_run(void *opaque)
 112 {
 113     CommitBlockJob *s = opaque;
 114     CommitCompleteData *data;
 115     int64_t sector_num, end;
 116     uint64_t delay_ns = 0;
 117     int ret = 0;
 118     int n = 0;
 119     void *buf = NULL;
 120     int bytes_written = 0;
 121     int64_t base_len;
 122
 123     ret = s->common.len = blk_getlength(s->top);
 124
 125
 126     if (s->common.len < 0) {
 127         goto out;
 128     }
 129
 130     ret = base_len = blk_getlength(s->base);
 131     if (base_len < 0) {
 132         goto out;
 133     }
 134
 135     if (base_len < s->common.len) {
 136         ret = blk_truncate(s->base, s->common.len);
 137         if (ret) {
 138             goto out;
 139         }
 140     }
 141
 142     end = s->common.len >> BDRV_SECTOR_BITS;
 143     buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
 144
 145     for (sector_num = 0; sector_num < end; sector_num += n) {
 146         bool copy;
 147
 148         /* Note that even when no rate limit is applied we need to yield
 149          * with no pending I/O here so that bdrv_drain_all() returns.
 150          */
 151         block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
 152         if (block_job_is_cancelled(&s->common)) {
 153             break;
 154         }
 155         /* Copy if allocated above the base */
 156         ret = bdrv_is_allocated_above(blk_bs(s->top), blk_bs(s->base),
 157                                       sector_num,
 158                                       COMMIT_BUFFER_SIZE / BDRV_SECTOR_SIZE,
 159                                       &n);
 160         copy = (ret == 1);
 161         trace_commit_one_iteration(s, sector_num, n, ret);
 162         if (copy) {
 163             ret = commit_populate(s->top, s->base, sector_num, n, buf);
 164             bytes_written += n * BDRV_SECTOR_SIZE;
 165         }
 166         if (ret < 0) {
 167             BlockErrorAction action =
 168                 block_job_error_action(&s->common, false, s->on_error, -ret);
 169             if (action == BLOCK_ERROR_ACTION_REPORT) {
 170                 goto out;
 171             } else {
 172                 n = 0;
 173                 continue;
 174             }
 175         }
 176         /* Publish progress */
 177         s->common.offset += n * BDRV_SECTOR_SIZE;
 178
 179         if (copy && s->common.speed) {
 180             delay_ns = ratelimit_calculate_delay(&s->limit, n);
 181         }
 182     }
 183
 184     ret = 0;
 185
 186 out:
 187     qemu_vfree(buf);
 188
 189     data = g_malloc(sizeof(*data));
 190     data->ret = ret;
 191     block_job_defer_to_main_loop(&s->common, commit_complete, data);
 192 }
 193
 194 static void commit_set_speed(BlockJob *job, int64_t speed, Error **errp)
 195 {
 196     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
 197
 198     if (speed < 0) {
 199         error_setg(errp, QERR_INVALID_PARAMETER, "speed");
 200         return;
 201     }
 202     ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
 203 }
 204
 205 static const BlockJobDriver commit_job_driver = {
 206     .instance_size = sizeof(CommitBlockJob),
 207     .job_type      = BLOCK_JOB_TYPE_COMMIT,
 208     .set_speed     = commit_set_speed,
 209 };
 210
 211 void commit_start(const char *job_id, BlockDriverState *bs,
 212                   BlockDriverState *base, BlockDriverState *top, int64_t speed,
 213                   BlockdevOnError on_error, BlockCompletionFunc *cb,
 214                   void *opaque, const char *backing_file_str, Error **errp)
 215 {
 216     CommitBlockJob *s;
 217     BlockReopenQueue *reopen_queue = NULL;
 218     int orig_overlay_flags;
 219     int orig_base_flags;
 220     BlockDriverState *overlay_bs;
 221     Error *local_err = NULL;
 222
 223     assert(top != bs);
 224     if (top == base) {
 225         error_setg(errp, "Invalid files for merge: top and base are the same");
 226         return;
 227     }
 228
 229     overlay_bs = bdrv_find_overlay(bs, top);
 230
 231     if (overlay_bs == NULL) {
 232         error_setg(errp, "Could not find overlay image for %s:", top->filename);
 233         return;
 234     }
 235
 236     s = block_job_create(job_id, &commit_job_driver, bs, speed,
 237                          cb, opaque, errp);
 238     if (!s) {
 239         return;
 240     }
 241
 242     orig_base_flags    = bdrv_get_flags(base);
 243     orig_overlay_flags = bdrv_get_flags(overlay_bs);
 244
 245     /* convert base & overlay_bs to r/w, if necessary */
 246     if (!(orig_overlay_flags & BDRV_O_RDWR)) {
 247         reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs, NULL,
 248                                          orig_overlay_flags | BDRV_O_RDWR);
 249     }
 250     if (!(orig_base_flags & BDRV_O_RDWR)) {
 251         reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL,
 252                                          orig_base_flags | BDRV_O_RDWR);
 253     }
 254     if (reopen_queue) {
 255         bdrv_reopen_multiple(reopen_queue, &local_err);
 256         if (local_err != NULL) {
 257             error_propagate(errp, local_err);
 258             block_job_unref(&s->common);
 259             return;
 260         }
 261     }
 262
 263
 264     s->base = blk_new();
 265     blk_insert_bs(s->base, base);
 266
 267     s->top = blk_new();
 268     blk_insert_bs(s->top, top);
 269
 270     s->active = bs;
 271
 272     s->base_flags          = orig_base_flags;
 273     s->orig_overlay_flags  = orig_overlay_flags;
 274
 275     s->backing_file_str = g_strdup(backing_file_str);
 276
 277     s->on_error = on_error;
 278     s->common.co = qemu_coroutine_create(commit_run, s);
 279
 280     trace_commit_start(bs, base, top, s, s->common.co, opaque);
 281     qemu_coroutine_enter(s->common.co);
 282 }
 283
 284
 285 #define COMMIT_BUF_SECTORS 2048
 286
 287 /* commit COW file into the raw image */
 288 int bdrv_commit(BlockDriverState *bs)
 289 {
 290     BlockBackend *src, *backing;
 291     BlockDriver *drv = bs->drv;
 292     int64_t sector, total_sectors, length, backing_length;
 293     int n, ro, open_flags;
 294     int ret = 0;
 295     uint8_t *buf = NULL;
 296
 297     if (!drv)
 298         return -ENOMEDIUM;
 299
 300     if (!bs->backing) {
 301         return -ENOTSUP;
 302     }
 303
 304     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
 305         bdrv_op_is_blocked(bs->backing->bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) {
 306         return -EBUSY;
 307     }
 308
 309     ro = bs->backing->bs->read_only;
 310     open_flags =  bs->backing->bs->open_flags;
 311
 312     if (ro) {
 313         if (bdrv_reopen(bs->backing->bs, open_flags | BDRV_O_RDWR, NULL)) {
 314             return -EACCES;
 315         }
 316     }
 317
 318     src = blk_new();
 319     blk_insert_bs(src, bs);
 320
 321     backing = blk_new();
 322     blk_insert_bs(backing, bs->backing->bs);
 323
 324     length = blk_getlength(src);
 325     if (length < 0) {
 326         ret = length;
 327         goto ro_cleanup;
 328     }
 329
 330     backing_length = blk_getlength(backing);
 331     if (backing_length < 0) {
 332         ret = backing_length;
 333         goto ro_cleanup;
 334     }
 335
 336     /* If our top snapshot is larger than the backing file image,
 337      * grow the backing file image if possible.  If not possible,
 338      * we must return an error */
 339     if (length > backing_length) {
 340         ret = blk_truncate(backing, length);
 341         if (ret < 0) {
 342             goto ro_cleanup;
 343         }
 344     }
 345
 346     total_sectors = length >> BDRV_SECTOR_BITS;
 347
 348     /* blk_try_blockalign() for src will choose an alignment that works for
 349      * backing as well, so no need to compare the alignment manually. */
 350     buf = blk_try_blockalign(src, COMMIT_BUF_SECTORS * BDRV_SECTOR_SIZE);
 351     if (buf == NULL) {
 352         ret = -ENOMEM;
 353         goto ro_cleanup;
 354     }
 355
 356     for (sector = 0; sector < total_sectors; sector += n) {
 357         ret = bdrv_is_allocated(bs, sector, COMMIT_BUF_SECTORS, &n);
 358         if (ret < 0) {
 359             goto ro_cleanup;
 360         }
 361         if (ret) {
 362             ret = blk_pread(src, sector * BDRV_SECTOR_SIZE, buf,
 363                             n * BDRV_SECTOR_SIZE);
 364             if (ret < 0) {
 365                 goto ro_cleanup;
 366             }
 367
 368             ret = blk_pwrite(backing, sector * BDRV_SECTOR_SIZE, buf,
 369                              n * BDRV_SECTOR_SIZE, 0);
 370             if (ret < 0) {
 371                 goto ro_cleanup;
 372             }
 373         }
 374     }
 375
 376     if (drv->bdrv_make_empty) {
 377         ret = drv->bdrv_make_empty(bs);
 378         if (ret < 0) {
 379             goto ro_cleanup;
 380         }
 381         blk_flush(src);
 382     }
 383
 384     /*
 385      * Make sure all data we wrote to the backing device is actually
 386      * stable on disk.
 387      */
 388     blk_flush(backing);
 389
 390     ret = 0;
 391 ro_cleanup:
 392     qemu_vfree(buf);
 393
 394     blk_unref(src);
 395     blk_unref(backing);
 396
 397     if (ro) {
 398         /* ignoring error return here */
 399         bdrv_reopen(bs->backing->bs, open_flags & ~BDRV_O_RDWR, NULL);
 400     }
 401
 402     return ret;
 403 }