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 = bdrv_find_overlay(active, top);
  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     if (overlay_bs && s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) {
 101         bdrv_reopen(overlay_bs, s->orig_overlay_flags, NULL);
 102     }
 103     g_free(s->backing_file_str);
 104     blk_unref(s->top);
 105     blk_unref(s->base);
 106     block_job_completed(&s->common, ret);
 107     g_free(data);
 108 }
 109
 110 static void coroutine_fn commit_run(void *opaque)
 111 {
 112     CommitBlockJob *s = opaque;
 113     CommitCompleteData *data;
 114     int64_t sector_num, end;
 115     uint64_t delay_ns = 0;
 116     int ret = 0;
 117     int n = 0;
 118     void *buf = NULL;
 119     int bytes_written = 0;
 120     int64_t base_len;
 121
 122     ret = s->common.len = blk_getlength(s->top);
 123
 124
 125     if (s->common.len < 0) {
 126         goto out;
 127     }
 128
 129     ret = base_len = blk_getlength(s->base);
 130     if (base_len < 0) {
 131         goto out;
 132     }
 133
 134     if (base_len < s->common.len) {
 135         ret = blk_truncate(s->base, s->common.len);
 136         if (ret) {
 137             goto out;
 138         }
 139     }
 140
 141     end = s->common.len >> BDRV_SECTOR_BITS;
 142     buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
 143
 144     for (sector_num = 0; sector_num < end; sector_num += n) {
 145         bool copy;
 146
 147         /* Note that even when no rate limit is applied we need to yield
 148          * with no pending I/O here so that bdrv_drain_all() returns.
 149          */
 150         block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
 151         if (block_job_is_cancelled(&s->common)) {
 152             break;
 153         }
 154         /* Copy if allocated above the base */
 155         ret = bdrv_is_allocated_above(blk_bs(s->top), blk_bs(s->base),
 156                                       sector_num,
 157                                       COMMIT_BUFFER_SIZE / BDRV_SECTOR_SIZE,
 158                                       &n);
 159         copy = (ret == 1);
 160         trace_commit_one_iteration(s, sector_num, n, ret);
 161         if (copy) {
 162             ret = commit_populate(s->top, s->base, sector_num, n, buf);
 163             bytes_written += n * BDRV_SECTOR_SIZE;
 164         }
 165         if (ret < 0) {
 166             BlockErrorAction action =
 167                 block_job_error_action(&s->common, false, s->on_error, -ret);
 168             if (action == BLOCK_ERROR_ACTION_REPORT) {
 169                 goto out;
 170             } else {
 171                 n = 0;
 172                 continue;
 173             }
 174         }
 175         /* Publish progress */
 176         s->common.offset += n * BDRV_SECTOR_SIZE;
 177
 178         if (copy && s->common.speed) {
 179             delay_ns = ratelimit_calculate_delay(&s->limit, n);
 180         }
 181     }
 182
 183     ret = 0;
 184
 185 out:
 186     qemu_vfree(buf);
 187
 188     data = g_malloc(sizeof(*data));
 189     data->ret = ret;
 190     block_job_defer_to_main_loop(&s->common, commit_complete, data);
 191 }
 192
 193 static void commit_set_speed(BlockJob *job, int64_t speed, Error **errp)
 194 {
 195     CommitBlockJob *s = container_of(job, CommitBlockJob, common);
 196
 197     if (speed < 0) {
 198         error_setg(errp, QERR_INVALID_PARAMETER, "speed");
 199         return;
 200     }
 201     ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
 202 }
 203
 204 static const BlockJobDriver commit_job_driver = {
 205     .instance_size = sizeof(CommitBlockJob),
 206     .job_type      = BLOCK_JOB_TYPE_COMMIT,
 207     .set_speed     = commit_set_speed,
 208 };
 209
 210 void commit_start(const char *job_id, BlockDriverState *bs,
 211                   BlockDriverState *base, BlockDriverState *top, int64_t speed,
 212                   BlockdevOnError on_error, BlockCompletionFunc *cb,
 213                   void *opaque, const char *backing_file_str, Error **errp)
 214 {
 215     CommitBlockJob *s;
 216     BlockReopenQueue *reopen_queue = NULL;
 217     int orig_overlay_flags;
 218     int orig_base_flags;
 219     BlockDriverState *overlay_bs;
 220     Error *local_err = NULL;
 221
 222     assert(top != bs);
 223     if (top == base) {
 224         error_setg(errp, "Invalid files for merge: top and base are the same");
 225         return;
 226     }
 227
 228     overlay_bs = bdrv_find_overlay(bs, top);
 229
 230     if (overlay_bs == NULL) {
 231         error_setg(errp, "Could not find overlay image for %s:", top->filename);
 232         return;
 233     }
 234
 235     s = block_job_create(job_id, &commit_job_driver, bs, speed,
 236                          cb, opaque, errp);
 237     if (!s) {
 238         return;
 239     }
 240
 241     orig_base_flags    = bdrv_get_flags(base);
 242     orig_overlay_flags = bdrv_get_flags(overlay_bs);
 243
 244     /* convert base & overlay_bs to r/w, if necessary */
 245     if (!(orig_overlay_flags & BDRV_O_RDWR)) {
 246         reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs, NULL,
 247                                          orig_overlay_flags | BDRV_O_RDWR);
 248     }
 249     if (!(orig_base_flags & BDRV_O_RDWR)) {
 250         reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL,
 251                                          orig_base_flags | BDRV_O_RDWR);
 252     }
 253     if (reopen_queue) {
 254         bdrv_reopen_multiple(reopen_queue, &local_err);
 255         if (local_err != NULL) {
 256             error_propagate(errp, local_err);
 257             block_job_unref(&s->common);
 258             return;
 259         }
 260     }
 261
 262
 263     s->base = blk_new();
 264     blk_insert_bs(s->base, base);
 265
 266     s->top = blk_new();
 267     blk_insert_bs(s->top, top);
 268
 269     s->active = bs;
 270
 271     s->base_flags          = orig_base_flags;
 272     s->orig_overlay_flags  = orig_overlay_flags;
 273
 274     s->backing_file_str = g_strdup(backing_file_str);
 275
 276     s->on_error = on_error;
 277     s->common.co = qemu_coroutine_create(commit_run, s);
 278
 279     trace_commit_start(bs, base, top, s, s->common.co, opaque);
 280     qemu_coroutine_enter(s->common.co);
 281 }
 282
 283
 284 #define COMMIT_BUF_SECTORS 2048
 285
 286 /* commit COW file into the raw image */
 287 int bdrv_commit(BlockDriverState *bs)
 288 {
 289     BlockBackend *src, *backing;
 290     BlockDriver *drv = bs->drv;
 291     int64_t sector, total_sectors, length, backing_length;
 292     int n, ro, open_flags;
 293     int ret = 0;
 294     uint8_t *buf = NULL;
 295
 296     if (!drv)
 297         return -ENOMEDIUM;
 298
 299     if (!bs->backing) {
 300         return -ENOTSUP;
 301     }
 302
 303     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
 304         bdrv_op_is_blocked(bs->backing->bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) {
 305         return -EBUSY;
 306     }
 307
 308     ro = bs->backing->bs->read_only;
 309     open_flags =  bs->backing->bs->open_flags;
 310
 311     if (ro) {
 312         if (bdrv_reopen(bs->backing->bs, open_flags | BDRV_O_RDWR, NULL)) {
 313             return -EACCES;
 314         }
 315     }
 316
 317     src = blk_new();
 318     blk_insert_bs(src, bs);
 319
 320     backing = blk_new();
 321     blk_insert_bs(backing, bs->backing->bs);
 322
 323     length = blk_getlength(src);
 324     if (length < 0) {
 325         ret = length;
 326         goto ro_cleanup;
 327     }
 328
 329     backing_length = blk_getlength(backing);
 330     if (backing_length < 0) {
 331         ret = backing_length;
 332         goto ro_cleanup;
 333     }
 334
 335     /* If our top snapshot is larger than the backing file image,
 336      * grow the backing file image if possible.  If not possible,
 337      * we must return an error */
 338     if (length > backing_length) {
 339         ret = blk_truncate(backing, length);
 340         if (ret < 0) {
 341             goto ro_cleanup;
 342         }
 343     }
 344
 345     total_sectors = length >> BDRV_SECTOR_BITS;
 346
 347     /* blk_try_blockalign() for src will choose an alignment that works for
 348      * backing as well, so no need to compare the alignment manually. */
 349     buf = blk_try_blockalign(src, COMMIT_BUF_SECTORS * BDRV_SECTOR_SIZE);
 350     if (buf == NULL) {
 351         ret = -ENOMEM;
 352         goto ro_cleanup;
 353     }
 354
 355     for (sector = 0; sector < total_sectors; sector += n) {
 356         ret = bdrv_is_allocated(bs, sector, COMMIT_BUF_SECTORS, &n);
 357         if (ret < 0) {
 358             goto ro_cleanup;
 359         }
 360         if (ret) {
 361             ret = blk_pread(src, sector * BDRV_SECTOR_SIZE, buf,
 362                             n * BDRV_SECTOR_SIZE);
 363             if (ret < 0) {
 364                 goto ro_cleanup;
 365             }
 366
 367             ret = blk_pwrite(backing, sector * BDRV_SECTOR_SIZE, buf,
 368                              n * BDRV_SECTOR_SIZE, 0);
 369             if (ret < 0) {
 370                 goto ro_cleanup;
 371             }
 372         }
 373     }
 374
 375     if (drv->bdrv_make_empty) {
 376         ret = drv->bdrv_make_empty(bs);
 377         if (ret < 0) {
 378             goto ro_cleanup;
 379         }
 380         blk_flush(src);
 381     }
 382
 383     /*
 384      * Make sure all data we wrote to the backing device is actually
 385      * stable on disk.
 386      */
 387     blk_flush(backing);
 388
 389     ret = 0;
 390 ro_cleanup:
 391     qemu_vfree(buf);
 392
 393     blk_unref(src);
 394     blk_unref(backing);
 395
 396     if (ro) {
 397         /* ignoring error return here */
 398         bdrv_reopen(bs->backing->bs, open_flags & ~BDRV_O_RDWR, NULL);
 399     }
 400
 401     return ret;
 402 }