block/quorum.c

   1 /*
   2  * Quorum Block filter
   3  *
   4  * Copyright (C) 2012-2014 Nodalink, EURL.
   5  *
   6  * Author:
   7  *   Benoît Canet <benoit.canet@irqsave.net>
   8  *
   9  * Based on the design and code of blkverify.c (Copyright (C) 2010 IBM, Corp)
  10  * and blkmirror.c (Copyright (C) 2011 Red Hat, Inc).
  11  *
  12  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  13  * See the COPYING file in the top-level directory.
  14  */
  15
  16 #include <gnutls/gnutls.h>
  17 #include <gnutls/crypto.h>
  18 #include "block/block_int.h"
  19 #include "qapi/qmp/qbool.h"
  20 #include "qapi/qmp/qdict.h"
  21 #include "qapi/qmp/qint.h"
  22 #include "qapi/qmp/qjson.h"
  23 #include "qapi/qmp/qlist.h"
  24 #include "qapi/qmp/qstring.h"
  25 #include "qapi-event.h"
  26
  27 #define HASH_LENGTH 32
  28
  29 #define QUORUM_OPT_VOTE_THRESHOLD "vote-threshold"
  30 #define QUORUM_OPT_BLKVERIFY      "blkverify"
  31 #define QUORUM_OPT_REWRITE        "rewrite-corrupted"
  32 #define QUORUM_OPT_READ_PATTERN   "read-pattern"
  33
  34 /* This union holds a vote hash value */
  35 typedef union QuorumVoteValue {
  36     char h[HASH_LENGTH];       /* SHA-256 hash */
  37     int64_t l;                 /* simpler 64 bits hash */
  38 } QuorumVoteValue;
  39
  40 /* A vote item */
  41 typedef struct QuorumVoteItem {
  42     int index;
  43     QLIST_ENTRY(QuorumVoteItem) next;
  44 } QuorumVoteItem;
  45
  46 /* this structure is a vote version. A version is the set of votes sharing the
  47  * same vote value.
  48  * The set of votes will be tracked with the items field and its cardinality is
  49  * vote_count.
  50  */
  51 typedef struct QuorumVoteVersion {
  52     QuorumVoteValue value;
  53     int index;
  54     int vote_count;
  55     QLIST_HEAD(, QuorumVoteItem) items;
  56     QLIST_ENTRY(QuorumVoteVersion) next;
  57 } QuorumVoteVersion;
  58
  59 /* this structure holds a group of vote versions together */
  60 typedef struct QuorumVotes {
  61     QLIST_HEAD(, QuorumVoteVersion) vote_list;
  62     bool (*compare)(QuorumVoteValue *a, QuorumVoteValue *b);
  63 } QuorumVotes;
  64
  65 /* the following structure holds the state of one quorum instance */
  66 typedef struct BDRVQuorumState {
  67     BlockDriverState **bs; /* children BlockDriverStates */
  68     int num_children;      /* children count */
  69     int threshold;         /* if less than threshold children reads gave the
  70                             * same result a quorum error occurs.
  71                             */
  72     bool is_blkverify;     /* true if the driver is in blkverify mode
  73                             * Writes are mirrored on two children devices.
  74                             * On reads the two children devices' contents are
  75                             * compared and if a difference is spotted its
  76                             * location is printed and the code aborts.
  77                             * It is useful to debug other block drivers by
  78                             * comparing them with a reference one.
  79                             */
  80     bool rewrite_corrupted;/* true if the driver must rewrite-on-read corrupted
  81                             * block if Quorum is reached.
  82                             */
  83
  84     QuorumReadPattern read_pattern;
  85 } BDRVQuorumState;
  86
  87 typedef struct QuorumAIOCB QuorumAIOCB;
  88
  89 /* Quorum will create one instance of the following structure per operation it
  90  * performs on its children.
  91  * So for each read/write operation coming from the upper layer there will be
  92  * $children_count QuorumChildRequest.
  93  */
  94 typedef struct QuorumChildRequest {
  95     BlockAIOCB *aiocb;
  96     QEMUIOVector qiov;
  97     uint8_t *buf;
  98     int ret;
  99     QuorumAIOCB *parent;
 100 } QuorumChildRequest;
 101
 102 /* Quorum will use the following structure to track progress of each read/write
 103  * operation received by the upper layer.
 104  * This structure hold pointers to the QuorumChildRequest structures instances
 105  * used to do operations on each children and track overall progress.
 106  */
 107 struct QuorumAIOCB {
 108     BlockAIOCB common;
 109
 110     /* Request metadata */
 111     uint64_t sector_num;
 112     int nb_sectors;
 113
 114     QEMUIOVector *qiov;         /* calling IOV */
 115
 116     QuorumChildRequest *qcrs;   /* individual child requests */
 117     int count;                  /* number of completed AIOCB */
 118     int success_count;          /* number of successfully completed AIOCB */
 119
 120     int rewrite_count;          /* number of replica to rewrite: count down to
 121                                  * zero once writes are fired
 122                                  */
 123
 124     QuorumVotes votes;
 125
 126     bool is_read;
 127     int vote_ret;
 128     int child_iter;             /* which child to read in fifo pattern */
 129 };
 130
 131 static bool quorum_vote(QuorumAIOCB *acb);
 132
 133 static void quorum_aio_cancel(BlockAIOCB *blockacb)
 134 {
 135     QuorumAIOCB *acb = container_of(blockacb, QuorumAIOCB, common);
 136     BDRVQuorumState *s = acb->common.bs->opaque;
 137     int i;
 138
 139     /* cancel all callbacks */
 140     for (i = 0; i < s->num_children; i++) {
 141         if (acb->qcrs[i].aiocb) {
 142             bdrv_aio_cancel_async(acb->qcrs[i].aiocb);
 143         }
 144     }
 145 }
 146
 147 static AIOCBInfo quorum_aiocb_info = {
 148     .aiocb_size         = sizeof(QuorumAIOCB),
 149     .cancel_async       = quorum_aio_cancel,
 150 };
 151
 152 static void quorum_aio_finalize(QuorumAIOCB *acb)
 153 {
 154     int i, ret = 0;
 155
 156     if (acb->vote_ret) {
 157         ret = acb->vote_ret;
 158     }
 159
 160     acb->common.cb(acb->common.opaque, ret);
 161
 162     if (acb->is_read) {
 163         /* on the quorum case acb->child_iter == s->num_children - 1 */
 164         for (i = 0; i <= acb->child_iter; i++) {
 165             qemu_vfree(acb->qcrs[i].buf);
 166             qemu_iovec_destroy(&acb->qcrs[i].qiov);
 167         }
 168     }
 169
 170     g_free(acb->qcrs);
 171     qemu_aio_unref(acb);
 172 }
 173
 174 static bool quorum_sha256_compare(QuorumVoteValue *a, QuorumVoteValue *b)
 175 {
 176     return !memcmp(a->h, b->h, HASH_LENGTH);
 177 }
 178
 179 static bool quorum_64bits_compare(QuorumVoteValue *a, QuorumVoteValue *b)
 180 {
 181     return a->l == b->l;
 182 }
 183
 184 static QuorumAIOCB *quorum_aio_get(BDRVQuorumState *s,
 185                                    BlockDriverState *bs,
 186                                    QEMUIOVector *qiov,
 187                                    uint64_t sector_num,
 188                                    int nb_sectors,
 189                                    BlockCompletionFunc *cb,
 190                                    void *opaque)
 191 {
 192     QuorumAIOCB *acb = qemu_aio_get(&quorum_aiocb_info, bs, cb, opaque);
 193     int i;
 194
 195     acb->common.bs->opaque = s;
 196     acb->sector_num = sector_num;
 197     acb->nb_sectors = nb_sectors;
 198     acb->qiov = qiov;
 199     acb->qcrs = g_new0(QuorumChildRequest, s->num_children);
 200     acb->count = 0;
 201     acb->success_count = 0;
 202     acb->rewrite_count = 0;
 203     acb->votes.compare = quorum_sha256_compare;
 204     QLIST_INIT(&acb->votes.vote_list);
 205     acb->is_read = false;
 206     acb->vote_ret = 0;
 207
 208     for (i = 0; i < s->num_children; i++) {
 209         acb->qcrs[i].buf = NULL;
 210         acb->qcrs[i].ret = 0;
 211         acb->qcrs[i].parent = acb;
 212     }
 213
 214     return acb;
 215 }
 216
 217 static void quorum_report_bad(QuorumAIOCB *acb, char *node_name, int ret)
 218 {
 219     const char *msg = NULL;
 220     if (ret < 0) {
 221         msg = strerror(-ret);
 222     }
 223     qapi_event_send_quorum_report_bad(!!msg, msg, node_name,
 224                                       acb->sector_num, acb->nb_sectors, &error_abort);
 225 }
 226
 227 static void quorum_report_failure(QuorumAIOCB *acb)
 228 {
 229     const char *reference = bdrv_get_device_name(acb->common.bs)[0] ?
 230                             bdrv_get_device_name(acb->common.bs) :
 231                             acb->common.bs->node_name;
 232
 233     qapi_event_send_quorum_failure(reference, acb->sector_num,
 234                                    acb->nb_sectors, &error_abort);
 235 }
 236
 237 static int quorum_vote_error(QuorumAIOCB *acb);
 238
 239 static bool quorum_has_too_much_io_failed(QuorumAIOCB *acb)
 240 {
 241     BDRVQuorumState *s = acb->common.bs->opaque;
 242
 243     if (acb->success_count < s->threshold) {
 244         acb->vote_ret = quorum_vote_error(acb);
 245         quorum_report_failure(acb);
 246         return true;
 247     }
 248
 249     return false;
 250 }
 251
 252 static void quorum_rewrite_aio_cb(void *opaque, int ret)
 253 {
 254     QuorumAIOCB *acb = opaque;
 255
 256     /* one less rewrite to do */
 257     acb->rewrite_count--;
 258
 259     /* wait until all rewrite callbacks have completed */
 260     if (acb->rewrite_count) {
 261         return;
 262     }
 263
 264     quorum_aio_finalize(acb);
 265 }
 266
 267 static BlockAIOCB *read_fifo_child(QuorumAIOCB *acb);
 268
 269 static void quorum_copy_qiov(QEMUIOVector *dest, QEMUIOVector *source)
 270 {
 271     int i;
 272     assert(dest->niov == source->niov);
 273     assert(dest->size == source->size);
 274     for (i = 0; i < source->niov; i++) {
 275         assert(dest->iov[i].iov_len == source->iov[i].iov_len);
 276         memcpy(dest->iov[i].iov_base,
 277                source->iov[i].iov_base,
 278                source->iov[i].iov_len);
 279     }
 280 }
 281
 282 static void quorum_aio_cb(void *opaque, int ret)
 283 {
 284     QuorumChildRequest *sacb = opaque;
 285     QuorumAIOCB *acb = sacb->parent;
 286     BDRVQuorumState *s = acb->common.bs->opaque;
 287     bool rewrite = false;
 288
 289     if (acb->is_read && s->read_pattern == QUORUM_READ_PATTERN_FIFO) {
 290         /* We try to read next child in FIFO order if we fail to read */
 291         if (ret < 0 && ++acb->child_iter < s->num_children) {
 292             read_fifo_child(acb);
 293             return;
 294         }
 295
 296         if (ret == 0) {
 297             quorum_copy_qiov(acb->qiov, &acb->qcrs[acb->child_iter].qiov);
 298         }
 299         acb->vote_ret = ret;
 300         quorum_aio_finalize(acb);
 301         return;
 302     }
 303
 304     sacb->ret = ret;
 305     acb->count++;
 306     if (ret == 0) {
 307         acb->success_count++;
 308     } else {
 309         quorum_report_bad(acb, sacb->aiocb->bs->node_name, ret);
 310     }
 311     assert(acb->count <= s->num_children);
 312     assert(acb->success_count <= s->num_children);
 313     if (acb->count < s->num_children) {
 314         return;
 315     }
 316
 317     /* Do the vote on read */
 318     if (acb->is_read) {
 319         rewrite = quorum_vote(acb);
 320     } else {
 321         quorum_has_too_much_io_failed(acb);
 322     }
 323
 324     /* if no rewrite is done the code will finish right away */
 325     if (!rewrite) {
 326         quorum_aio_finalize(acb);
 327     }
 328 }
 329
 330 static void quorum_report_bad_versions(BDRVQuorumState *s,
 331                                        QuorumAIOCB *acb,
 332                                        QuorumVoteValue *value)
 333 {
 334     QuorumVoteVersion *version;
 335     QuorumVoteItem *item;
 336
 337     QLIST_FOREACH(version, &acb->votes.vote_list, next) {
 338         if (acb->votes.compare(&version->value, value)) {
 339             continue;
 340         }
 341         QLIST_FOREACH(item, &version->items, next) {
 342             quorum_report_bad(acb, s->bs[item->index]->node_name, 0);
 343         }
 344     }
 345 }
 346
 347 static bool quorum_rewrite_bad_versions(BDRVQuorumState *s, QuorumAIOCB *acb,
 348                                         QuorumVoteValue *value)
 349 {
 350     QuorumVoteVersion *version;
 351     QuorumVoteItem *item;
 352     int count = 0;
 353
 354     /* first count the number of bad versions: done first to avoid concurrency
 355      * issues.
 356      */
 357     QLIST_FOREACH(version, &acb->votes.vote_list, next) {
 358         if (acb->votes.compare(&version->value, value)) {
 359             continue;
 360         }
 361         QLIST_FOREACH(item, &version->items, next) {
 362             count++;
 363         }
 364     }
 365
 366     /* quorum_rewrite_aio_cb will count down this to zero */
 367     acb->rewrite_count = count;
 368
 369     /* now fire the correcting rewrites */
 370     QLIST_FOREACH(version, &acb->votes.vote_list, next) {
 371         if (acb->votes.compare(&version->value, value)) {
 372             continue;
 373         }
 374         QLIST_FOREACH(item, &version->items, next) {
 375             bdrv_aio_writev(s->bs[item->index], acb->sector_num, acb->qiov,
 376                             acb->nb_sectors, quorum_rewrite_aio_cb, acb);
 377         }
 378     }
 379
 380     /* return true if any rewrite is done else false */
 381     return count;
 382 }
 383
 384 static void quorum_count_vote(QuorumVotes *votes,
 385                               QuorumVoteValue *value,
 386                               int index)
 387 {
 388     QuorumVoteVersion *v = NULL, *version = NULL;
 389     QuorumVoteItem *item;
 390
 391     /* look if we have something with this hash */
 392     QLIST_FOREACH(v, &votes->vote_list, next) {
 393         if (votes->compare(&v->value, value)) {
 394             version = v;
 395             break;
 396         }
 397     }
 398
 399     /* It's a version not yet in the list add it */
 400     if (!version) {
 401         version = g_new0(QuorumVoteVersion, 1);
 402         QLIST_INIT(&version->items);
 403         memcpy(&version->value, value, sizeof(version->value));
 404         version->index = index;
 405         version->vote_count = 0;
 406         QLIST_INSERT_HEAD(&votes->vote_list, version, next);
 407     }
 408
 409     version->vote_count++;
 410
 411     item = g_new0(QuorumVoteItem, 1);
 412     item->index = index;
 413     QLIST_INSERT_HEAD(&version->items, item, next);
 414 }
 415
 416 static void quorum_free_vote_list(QuorumVotes *votes)
 417 {
 418     QuorumVoteVersion *version, *next_version;
 419     QuorumVoteItem *item, *next_item;
 420
 421     QLIST_FOREACH_SAFE(version, &votes->vote_list, next, next_version) {
 422         QLIST_REMOVE(version, next);
 423         QLIST_FOREACH_SAFE(item, &version->items, next, next_item) {
 424             QLIST_REMOVE(item, next);
 425             g_free(item);
 426         }
 427         g_free(version);
 428     }
 429 }
 430
 431 static int quorum_compute_hash(QuorumAIOCB *acb, int i, QuorumVoteValue *hash)
 432 {
 433     int j, ret;
 434     gnutls_hash_hd_t dig;
 435     QEMUIOVector *qiov = &acb->qcrs[i].qiov;
 436
 437     ret = gnutls_hash_init(&dig, GNUTLS_DIG_SHA256);
 438
 439     if (ret < 0) {
 440         return ret;
 441     }
 442
 443     for (j = 0; j < qiov->niov; j++) {
 444         ret = gnutls_hash(dig, qiov->iov[j].iov_base, qiov->iov[j].iov_len);
 445         if (ret < 0) {
 446             break;
 447         }
 448     }
 449
 450     gnutls_hash_deinit(dig, (void *) hash);
 451     return ret;
 452 }
 453
 454 static QuorumVoteVersion *quorum_get_vote_winner(QuorumVotes *votes)
 455 {
 456     int max = 0;
 457     QuorumVoteVersion *candidate, *winner = NULL;
 458
 459     QLIST_FOREACH(candidate, &votes->vote_list, next) {
 460         if (candidate->vote_count > max) {
 461             max = candidate->vote_count;
 462             winner = candidate;
 463         }
 464     }
 465
 466     return winner;
 467 }
 468
 469 /* qemu_iovec_compare is handy for blkverify mode because it returns the first
 470  * differing byte location. Yet it is handcoded to compare vectors one byte
 471  * after another so it does not benefit from the libc SIMD optimizations.
 472  * quorum_iovec_compare is written for speed and should be used in the non
 473  * blkverify mode of quorum.
 474  */
 475 static bool quorum_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
 476 {
 477     int i;
 478     int result;
 479
 480     assert(a->niov == b->niov);
 481     for (i = 0; i < a->niov; i++) {
 482         assert(a->iov[i].iov_len == b->iov[i].iov_len);
 483         result = memcmp(a->iov[i].iov_base,
 484                         b->iov[i].iov_base,
 485                         a->iov[i].iov_len);
 486         if (result) {
 487             return false;
 488         }
 489     }
 490
 491     return true;
 492 }
 493
 494 static void GCC_FMT_ATTR(2, 3) quorum_err(QuorumAIOCB *acb,
 495                                           const char *fmt, ...)
 496 {
 497     va_list ap;
 498
 499     va_start(ap, fmt);
 500     fprintf(stderr, "quorum: sector_num=%" PRId64 " nb_sectors=%d ",
 501             acb->sector_num, acb->nb_sectors);
 502     vfprintf(stderr, fmt, ap);
 503     fprintf(stderr, "\n");
 504     va_end(ap);
 505     exit(1);
 506 }
 507
 508 static bool quorum_compare(QuorumAIOCB *acb,
 509                            QEMUIOVector *a,
 510                            QEMUIOVector *b)
 511 {
 512     BDRVQuorumState *s = acb->common.bs->opaque;
 513     ssize_t offset;
 514
 515     /* This driver will replace blkverify in this particular case */
 516     if (s->is_blkverify) {
 517         offset = qemu_iovec_compare(a, b);
 518         if (offset != -1) {
 519             quorum_err(acb, "contents mismatch in sector %" PRId64,
 520                        acb->sector_num +
 521                        (uint64_t)(offset / BDRV_SECTOR_SIZE));
 522         }
 523         return true;
 524     }
 525
 526     return quorum_iovec_compare(a, b);
 527 }
 528
 529 /* Do a vote to get the error code */
 530 static int quorum_vote_error(QuorumAIOCB *acb)
 531 {
 532     BDRVQuorumState *s = acb->common.bs->opaque;
 533     QuorumVoteVersion *winner = NULL;
 534     QuorumVotes error_votes;
 535     QuorumVoteValue result_value;
 536     int i, ret = 0;
 537     bool error = false;
 538
 539     QLIST_INIT(&error_votes.vote_list);
 540     error_votes.compare = quorum_64bits_compare;
 541
 542     for (i = 0; i < s->num_children; i++) {
 543         ret = acb->qcrs[i].ret;
 544         if (ret) {
 545             error = true;
 546             result_value.l = ret;
 547             quorum_count_vote(&error_votes, &result_value, i);
 548         }
 549     }
 550
 551     if (error) {
 552         winner = quorum_get_vote_winner(&error_votes);
 553         ret = winner->value.l;
 554     }
 555
 556     quorum_free_vote_list(&error_votes);
 557
 558     return ret;
 559 }
 560
 561 static bool quorum_vote(QuorumAIOCB *acb)
 562 {
 563     bool quorum = true;
 564     bool rewrite = false;
 565     int i, j, ret;
 566     QuorumVoteValue hash;
 567     BDRVQuorumState *s = acb->common.bs->opaque;
 568     QuorumVoteVersion *winner;
 569
 570     if (quorum_has_too_much_io_failed(acb)) {
 571         return false;
 572     }
 573
 574     /* get the index of the first successful read */
 575     for (i = 0; i < s->num_children; i++) {
 576         if (!acb->qcrs[i].ret) {
 577             break;
 578         }
 579     }
 580
 581     assert(i < s->num_children);
 582
 583     /* compare this read with all other successful reads stopping at quorum
 584      * failure
 585      */
 586     for (j = i + 1; j < s->num_children; j++) {
 587         if (acb->qcrs[j].ret) {
 588             continue;
 589         }
 590         quorum = quorum_compare(acb, &acb->qcrs[i].qiov, &acb->qcrs[j].qiov);
 591         if (!quorum) {
 592             break;
 593        }
 594     }
 595
 596     /* Every successful read agrees */
 597     if (quorum) {
 598         quorum_copy_qiov(acb->qiov, &acb->qcrs[i].qiov);
 599         return false;
 600     }
 601
 602     /* compute hashes for each successful read, also store indexes */
 603     for (i = 0; i < s->num_children; i++) {
 604         if (acb->qcrs[i].ret) {
 605             continue;
 606         }
 607         ret = quorum_compute_hash(acb, i, &hash);
 608         /* if ever the hash computation failed */
 609         if (ret < 0) {
 610             acb->vote_ret = ret;
 611             goto free_exit;
 612         }
 613         quorum_count_vote(&acb->votes, &hash, i);
 614     }
 615
 616     /* vote to select the most represented version */
 617     winner = quorum_get_vote_winner(&acb->votes);
 618
 619     /* if the winner count is smaller than threshold the read fails */
 620     if (winner->vote_count < s->threshold) {
 621         quorum_report_failure(acb);
 622         acb->vote_ret = -EIO;
 623         goto free_exit;
 624     }
 625
 626     /* we have a winner: copy it */
 627     quorum_copy_qiov(acb->qiov, &acb->qcrs[winner->index].qiov);
 628
 629     /* some versions are bad print them */
 630     quorum_report_bad_versions(s, acb, &winner->value);
 631
 632     /* corruption correction is enabled */
 633     if (s->rewrite_corrupted) {
 634         rewrite = quorum_rewrite_bad_versions(s, acb, &winner->value);
 635     }
 636
 637 free_exit:
 638     /* free lists */
 639     quorum_free_vote_list(&acb->votes);
 640     return rewrite;
 641 }
 642
 643 static BlockAIOCB *read_quorum_children(QuorumAIOCB *acb)
 644 {
 645     BDRVQuorumState *s = acb->common.bs->opaque;
 646     int i;
 647
 648     for (i = 0; i < s->num_children; i++) {
 649         acb->qcrs[i].buf = qemu_blockalign(s->bs[i], acb->qiov->size);
 650         qemu_iovec_init(&acb->qcrs[i].qiov, acb->qiov->niov);
 651         qemu_iovec_clone(&acb->qcrs[i].qiov, acb->qiov, acb->qcrs[i].buf);
 652     }
 653
 654     for (i = 0; i < s->num_children; i++) {
 655         bdrv_aio_readv(s->bs[i], acb->sector_num, &acb->qcrs[i].qiov,
 656                        acb->nb_sectors, quorum_aio_cb, &acb->qcrs[i]);
 657     }
 658
 659     return &acb->common;
 660 }
 661
 662 static BlockAIOCB *read_fifo_child(QuorumAIOCB *acb)
 663 {
 664     BDRVQuorumState *s = acb->common.bs->opaque;
 665
 666     acb->qcrs[acb->child_iter].buf = qemu_blockalign(s->bs[acb->child_iter],
 667                                                      acb->qiov->size);
 668     qemu_iovec_init(&acb->qcrs[acb->child_iter].qiov, acb->qiov->niov);
 669     qemu_iovec_clone(&acb->qcrs[acb->child_iter].qiov, acb->qiov,
 670                      acb->qcrs[acb->child_iter].buf);
 671     bdrv_aio_readv(s->bs[acb->child_iter], acb->sector_num,
 672                    &acb->qcrs[acb->child_iter].qiov, acb->nb_sectors,
 673                    quorum_aio_cb, &acb->qcrs[acb->child_iter]);
 674
 675     return &acb->common;
 676 }
 677
 678 static BlockAIOCB *quorum_aio_readv(BlockDriverState *bs,
 679                                     int64_t sector_num,
 680                                     QEMUIOVector *qiov,
 681                                     int nb_sectors,
 682                                     BlockCompletionFunc *cb,
 683                                     void *opaque)
 684 {
 685     BDRVQuorumState *s = bs->opaque;
 686     QuorumAIOCB *acb = quorum_aio_get(s, bs, qiov, sector_num,
 687                                       nb_sectors, cb, opaque);
 688     acb->is_read = true;
 689
 690     if (s->read_pattern == QUORUM_READ_PATTERN_QUORUM) {
 691         acb->child_iter = s->num_children - 1;
 692         return read_quorum_children(acb);
 693     }
 694
 695     acb->child_iter = 0;
 696     return read_fifo_child(acb);
 697 }
 698
 699 static BlockAIOCB *quorum_aio_writev(BlockDriverState *bs,
 700                                      int64_t sector_num,
 701                                      QEMUIOVector *qiov,
 702                                      int nb_sectors,
 703                                      BlockCompletionFunc *cb,
 704                                      void *opaque)
 705 {
 706     BDRVQuorumState *s = bs->opaque;
 707     QuorumAIOCB *acb = quorum_aio_get(s, bs, qiov, sector_num, nb_sectors,
 708                                       cb, opaque);
 709     int i;
 710
 711     for (i = 0; i < s->num_children; i++) {
 712         acb->qcrs[i].aiocb = bdrv_aio_writev(s->bs[i], sector_num, qiov,
 713                                              nb_sectors, &quorum_aio_cb,
 714                                              &acb->qcrs[i]);
 715     }
 716
 717     return &acb->common;
 718 }
 719
 720 static int64_t quorum_getlength(BlockDriverState *bs)
 721 {
 722     BDRVQuorumState *s = bs->opaque;
 723     int64_t result;
 724     int i;
 725
 726     /* check that all file have the same length */
 727     result = bdrv_getlength(s->bs[0]);
 728     if (result < 0) {
 729         return result;
 730     }
 731     for (i = 1; i < s->num_children; i++) {
 732         int64_t value = bdrv_getlength(s->bs[i]);
 733         if (value < 0) {
 734             return value;
 735         }
 736         if (value != result) {
 737             return -EIO;
 738         }
 739     }
 740
 741     return result;
 742 }
 743
 744 static void quorum_invalidate_cache(BlockDriverState *bs, Error **errp)
 745 {
 746     BDRVQuorumState *s = bs->opaque;
 747     Error *local_err = NULL;
 748     int i;
 749
 750     for (i = 0; i < s->num_children; i++) {
 751         bdrv_invalidate_cache(s->bs[i], &local_err);
 752         if (local_err) {
 753             error_propagate(errp, local_err);
 754             return;
 755         }
 756     }
 757 }
 758
 759 static coroutine_fn int quorum_co_flush(BlockDriverState *bs)
 760 {
 761     BDRVQuorumState *s = bs->opaque;
 762     QuorumVoteVersion *winner = NULL;
 763     QuorumVotes error_votes;
 764     QuorumVoteValue result_value;
 765     int i;
 766     int result = 0;
 767
 768     QLIST_INIT(&error_votes.vote_list);
 769     error_votes.compare = quorum_64bits_compare;
 770
 771     for (i = 0; i < s->num_children; i++) {
 772         result = bdrv_co_flush(s->bs[i]);
 773         result_value.l = result;
 774         quorum_count_vote(&error_votes, &result_value, i);
 775     }
 776
 777     winner = quorum_get_vote_winner(&error_votes);
 778     result = winner->value.l;
 779
 780     quorum_free_vote_list(&error_votes);
 781
 782     return result;
 783 }
 784
 785 static bool quorum_recurse_is_first_non_filter(BlockDriverState *bs,
 786                                                BlockDriverState *candidate)
 787 {
 788     BDRVQuorumState *s = bs->opaque;
 789     int i;
 790
 791     for (i = 0; i < s->num_children; i++) {
 792         bool perm = bdrv_recurse_is_first_non_filter(s->bs[i],
 793                                                      candidate);
 794         if (perm) {
 795             return true;
 796         }
 797     }
 798
 799     return false;
 800 }
 801
 802 static int quorum_valid_threshold(int threshold, int num_children, Error **errp)
 803 {
 804
 805     if (threshold < 1) {
 806         error_set(errp, QERR_INVALID_PARAMETER_VALUE,
 807                   "vote-threshold", "value >= 1");
 808         return -ERANGE;
 809     }
 810
 811     if (threshold > num_children) {
 812         error_setg(errp, "threshold may not exceed children count");
 813         return -ERANGE;
 814     }
 815
 816     return 0;
 817 }
 818
 819 static QemuOptsList quorum_runtime_opts = {
 820     .name = "quorum",
 821     .head = QTAILQ_HEAD_INITIALIZER(quorum_runtime_opts.head),
 822     .desc = {
 823         {
 824             .name = QUORUM_OPT_VOTE_THRESHOLD,
 825             .type = QEMU_OPT_NUMBER,
 826             .help = "The number of vote needed for reaching quorum",
 827         },
 828         {
 829             .name = QUORUM_OPT_BLKVERIFY,
 830             .type = QEMU_OPT_BOOL,
 831             .help = "Trigger block verify mode if set",
 832         },
 833         {
 834             .name = QUORUM_OPT_REWRITE,
 835             .type = QEMU_OPT_BOOL,
 836             .help = "Rewrite corrupted block on read quorum",
 837         },
 838         {
 839             .name = QUORUM_OPT_READ_PATTERN,
 840             .type = QEMU_OPT_STRING,
 841             .help = "Allowed pattern: quorum, fifo. Quorum is default",
 842         },
 843         { /* end of list */ }
 844     },
 845 };
 846
 847 static int parse_read_pattern(const char *opt)
 848 {
 849     int i;
 850
 851     if (!opt) {
 852         /* Set quorum as default */
 853         return QUORUM_READ_PATTERN_QUORUM;
 854     }
 855
 856     for (i = 0; i < QUORUM_READ_PATTERN_MAX; i++) {
 857         if (!strcmp(opt, QuorumReadPattern_lookup[i])) {
 858             return i;
 859         }
 860     }
 861
 862     return -EINVAL;
 863 }
 864
 865 static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
 866                        Error **errp)
 867 {
 868     BDRVQuorumState *s = bs->opaque;
 869     Error *local_err = NULL;
 870     QemuOpts *opts = NULL;
 871     bool *opened;
 872     QDict *sub = NULL;
 873     QList *list = NULL;
 874     const QListEntry *lentry;
 875     int i;
 876     int ret = 0;
 877
 878     qdict_flatten(options);
 879     qdict_extract_subqdict(options, &sub, "children.");
 880     qdict_array_split(sub, &list);
 881
 882     if (qdict_size(sub)) {
 883         error_setg(&local_err, "Invalid option children.%s",
 884                    qdict_first(sub)->key);
 885         ret = -EINVAL;
 886         goto exit;
 887     }
 888
 889     /* count how many different children are present */
 890     s->num_children = qlist_size(list);
 891     if (s->num_children < 2) {
 892         error_setg(&local_err,
 893                    "Number of provided children must be greater than 1");
 894         ret = -EINVAL;
 895         goto exit;
 896     }
 897
 898     opts = qemu_opts_create(&quorum_runtime_opts, NULL, 0, &error_abort);
 899     qemu_opts_absorb_qdict(opts, options, &local_err);
 900     if (local_err) {
 901         ret = -EINVAL;
 902         goto exit;
 903     }
 904
 905     s->threshold = qemu_opt_get_number(opts, QUORUM_OPT_VOTE_THRESHOLD, 0);
 906     ret = parse_read_pattern(qemu_opt_get(opts, QUORUM_OPT_READ_PATTERN));
 907     if (ret < 0) {
 908         error_setg(&local_err, "Please set read-pattern as fifo or quorum");
 909         goto exit;
 910     }
 911     s->read_pattern = ret;
 912
 913     if (s->read_pattern == QUORUM_READ_PATTERN_QUORUM) {
 914         /* and validate it against s->num_children */
 915         ret = quorum_valid_threshold(s->threshold, s->num_children, &local_err);
 916         if (ret < 0) {
 917             goto exit;
 918         }
 919
 920         /* is the driver in blkverify mode */
 921         if (qemu_opt_get_bool(opts, QUORUM_OPT_BLKVERIFY, false) &&
 922             s->num_children == 2 && s->threshold == 2) {
 923             s->is_blkverify = true;
 924         } else if (qemu_opt_get_bool(opts, QUORUM_OPT_BLKVERIFY, false)) {
 925             fprintf(stderr, "blkverify mode is set by setting blkverify=on "
 926                     "and using two files with vote_threshold=2\n");
 927         }
 928
 929         s->rewrite_corrupted = qemu_opt_get_bool(opts, QUORUM_OPT_REWRITE,
 930                                                  false);
 931         if (s->rewrite_corrupted && s->is_blkverify) {
 932             error_setg(&local_err,
 933                        "rewrite-corrupted=on cannot be used with blkverify=on");
 934             ret = -EINVAL;
 935             goto exit;
 936         }
 937     }
 938
 939     /* allocate the children BlockDriverState array */
 940     s->bs = g_new0(BlockDriverState *, s->num_children);
 941     opened = g_new0(bool, s->num_children);
 942
 943     for (i = 0, lentry = qlist_first(list); lentry;
 944          lentry = qlist_next(lentry), i++) {
 945         QDict *d;
 946         QString *string;
 947
 948         switch (qobject_type(lentry->value))
 949         {
 950             /* List of options */
 951             case QTYPE_QDICT:
 952                 d = qobject_to_qdict(lentry->value);
 953                 QINCREF(d);
 954                 ret = bdrv_open(&s->bs[i], NULL, NULL, d, flags, NULL,
 955                                 &local_err);
 956                 break;
 957
 958             /* QMP reference */
 959             case QTYPE_QSTRING:
 960                 string = qobject_to_qstring(lentry->value);
 961                 ret = bdrv_open(&s->bs[i], NULL, qstring_get_str(string), NULL,
 962                                 flags, NULL, &local_err);
 963                 break;
 964
 965             default:
 966                 error_setg(&local_err, "Specification of child block device %i "
 967                            "is invalid", i);
 968                 ret = -EINVAL;
 969         }
 970
 971         if (ret < 0) {
 972             goto close_exit;
 973         }
 974         opened[i] = true;
 975     }
 976
 977     g_free(opened);
 978     goto exit;
 979
 980 close_exit:
 981     /* cleanup on error */
 982     for (i = 0; i < s->num_children; i++) {
 983         if (!opened[i]) {
 984             continue;
 985         }
 986         bdrv_unref(s->bs[i]);
 987     }
 988     g_free(s->bs);
 989     g_free(opened);
 990 exit:
 991     qemu_opts_del(opts);
 992     /* propagate error */
 993     if (local_err) {
 994         error_propagate(errp, local_err);
 995     }
 996     QDECREF(list);
 997     QDECREF(sub);
 998     return ret;
 999 }
1000
1001 static void quorum_close(BlockDriverState *bs)
1002 {
1003     BDRVQuorumState *s = bs->opaque;
1004     int i;
1005
1006     for (i = 0; i < s->num_children; i++) {
1007         bdrv_unref(s->bs[i]);
1008     }
1009
1010     g_free(s->bs);
1011 }
1012
1013 static void quorum_detach_aio_context(BlockDriverState *bs)
1014 {
1015     BDRVQuorumState *s = bs->opaque;
1016     int i;
1017
1018     for (i = 0; i < s->num_children; i++) {
1019         bdrv_detach_aio_context(s->bs[i]);
1020     }
1021 }
1022
1023 static void quorum_attach_aio_context(BlockDriverState *bs,
1024                                       AioContext *new_context)
1025 {
1026     BDRVQuorumState *s = bs->opaque;
1027     int i;
1028
1029     for (i = 0; i < s->num_children; i++) {
1030         bdrv_attach_aio_context(s->bs[i], new_context);
1031     }
1032 }
1033
1034 static void quorum_refresh_filename(BlockDriverState *bs)
1035 {
1036     BDRVQuorumState *s = bs->opaque;
1037     QDict *opts;
1038     QList *children;
1039     int i;
1040
1041     for (i = 0; i < s->num_children; i++) {
1042         bdrv_refresh_filename(s->bs[i]);
1043         if (!s->bs[i]->full_open_options) {
1044             return;
1045         }
1046     }
1047
1048     children = qlist_new();
1049     for (i = 0; i < s->num_children; i++) {
1050         QINCREF(s->bs[i]->full_open_options);
1051         qlist_append_obj(children, QOBJECT(s->bs[i]->full_open_options));
1052     }
1053
1054     opts = qdict_new();
1055     qdict_put_obj(opts, "driver", QOBJECT(qstring_from_str("quorum")));
1056     qdict_put_obj(opts, QUORUM_OPT_VOTE_THRESHOLD,
1057                   QOBJECT(qint_from_int(s->threshold)));
1058     qdict_put_obj(opts, QUORUM_OPT_BLKVERIFY,
1059                   QOBJECT(qbool_from_int(s->is_blkverify)));
1060     qdict_put_obj(opts, QUORUM_OPT_REWRITE,
1061                   QOBJECT(qbool_from_int(s->rewrite_corrupted)));
1062     qdict_put_obj(opts, "children", QOBJECT(children));
1063
1064     bs->full_open_options = opts;
1065 }
1066
1067 static BlockDriver bdrv_quorum = {
1068     .format_name                        = "quorum",
1069     .protocol_name                      = "quorum",
1070
1071     .instance_size                      = sizeof(BDRVQuorumState),
1072
1073     .bdrv_file_open                     = quorum_open,
1074     .bdrv_close                         = quorum_close,
1075     .bdrv_refresh_filename              = quorum_refresh_filename,
1076
1077     .bdrv_co_flush_to_disk              = quorum_co_flush,
1078
1079     .bdrv_getlength                     = quorum_getlength,
1080
1081     .bdrv_aio_readv                     = quorum_aio_readv,
1082     .bdrv_aio_writev                    = quorum_aio_writev,
1083     .bdrv_invalidate_cache              = quorum_invalidate_cache,
1084
1085     .bdrv_detach_aio_context            = quorum_detach_aio_context,
1086     .bdrv_attach_aio_context            = quorum_attach_aio_context,
1087
1088     .is_filter                          = true,
1089     .bdrv_recurse_is_first_non_filter   = quorum_recurse_is_first_non_filter,
1090 };
1091
1092 static void bdrv_quorum_init(void)
1093 {
1094     bdrv_register(&bdrv_quorum);
1095 }
1096
1097 block_init(bdrv_quorum_init);