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-rw-r--r--src/block/quorum.c1070
1 files changed, 1070 insertions, 0 deletions
diff --git a/src/block/quorum.c b/src/block/quorum.c
new file mode 100644
index 0000000..e640688
--- /dev/null
+++ b/src/block/quorum.c
@@ -0,0 +1,1070 @@
+/*
+ * Quorum Block filter
+ *
+ * Copyright (C) 2012-2014 Nodalink, EURL.
+ *
+ * Author:
+ * Benoît Canet <benoit.canet@irqsave.net>
+ *
+ * Based on the design and code of blkverify.c (Copyright (C) 2010 IBM, Corp)
+ * and blkmirror.c (Copyright (C) 2011 Red Hat, Inc).
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "block/block_int.h"
+#include "qapi/qmp/qbool.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qerror.h"
+#include "qapi/qmp/qint.h"
+#include "qapi/qmp/qjson.h"
+#include "qapi/qmp/qlist.h"
+#include "qapi/qmp/qstring.h"
+#include "qapi-event.h"
+#include "crypto/hash.h"
+
+#define HASH_LENGTH 32
+
+#define QUORUM_OPT_VOTE_THRESHOLD "vote-threshold"
+#define QUORUM_OPT_BLKVERIFY "blkverify"
+#define QUORUM_OPT_REWRITE "rewrite-corrupted"
+#define QUORUM_OPT_READ_PATTERN "read-pattern"
+
+/* This union holds a vote hash value */
+typedef union QuorumVoteValue {
+ uint8_t h[HASH_LENGTH]; /* SHA-256 hash */
+ int64_t l; /* simpler 64 bits hash */
+} QuorumVoteValue;
+
+/* A vote item */
+typedef struct QuorumVoteItem {
+ int index;
+ QLIST_ENTRY(QuorumVoteItem) next;
+} QuorumVoteItem;
+
+/* this structure is a vote version. A version is the set of votes sharing the
+ * same vote value.
+ * The set of votes will be tracked with the items field and its cardinality is
+ * vote_count.
+ */
+typedef struct QuorumVoteVersion {
+ QuorumVoteValue value;
+ int index;
+ int vote_count;
+ QLIST_HEAD(, QuorumVoteItem) items;
+ QLIST_ENTRY(QuorumVoteVersion) next;
+} QuorumVoteVersion;
+
+/* this structure holds a group of vote versions together */
+typedef struct QuorumVotes {
+ QLIST_HEAD(, QuorumVoteVersion) vote_list;
+ bool (*compare)(QuorumVoteValue *a, QuorumVoteValue *b);
+} QuorumVotes;
+
+/* the following structure holds the state of one quorum instance */
+typedef struct BDRVQuorumState {
+ BdrvChild **children; /* children BlockDriverStates */
+ int num_children; /* children count */
+ int threshold; /* if less than threshold children reads gave the
+ * same result a quorum error occurs.
+ */
+ bool is_blkverify; /* true if the driver is in blkverify mode
+ * Writes are mirrored on two children devices.
+ * On reads the two children devices' contents are
+ * compared and if a difference is spotted its
+ * location is printed and the code aborts.
+ * It is useful to debug other block drivers by
+ * comparing them with a reference one.
+ */
+ bool rewrite_corrupted;/* true if the driver must rewrite-on-read corrupted
+ * block if Quorum is reached.
+ */
+
+ QuorumReadPattern read_pattern;
+} BDRVQuorumState;
+
+typedef struct QuorumAIOCB QuorumAIOCB;
+
+/* Quorum will create one instance of the following structure per operation it
+ * performs on its children.
+ * So for each read/write operation coming from the upper layer there will be
+ * $children_count QuorumChildRequest.
+ */
+typedef struct QuorumChildRequest {
+ BlockAIOCB *aiocb;
+ QEMUIOVector qiov;
+ uint8_t *buf;
+ int ret;
+ QuorumAIOCB *parent;
+} QuorumChildRequest;
+
+/* Quorum will use the following structure to track progress of each read/write
+ * operation received by the upper layer.
+ * This structure hold pointers to the QuorumChildRequest structures instances
+ * used to do operations on each children and track overall progress.
+ */
+struct QuorumAIOCB {
+ BlockAIOCB common;
+
+ /* Request metadata */
+ uint64_t sector_num;
+ int nb_sectors;
+
+ QEMUIOVector *qiov; /* calling IOV */
+
+ QuorumChildRequest *qcrs; /* individual child requests */
+ int count; /* number of completed AIOCB */
+ int success_count; /* number of successfully completed AIOCB */
+
+ int rewrite_count; /* number of replica to rewrite: count down to
+ * zero once writes are fired
+ */
+
+ QuorumVotes votes;
+
+ bool is_read;
+ int vote_ret;
+ int child_iter; /* which child to read in fifo pattern */
+};
+
+static bool quorum_vote(QuorumAIOCB *acb);
+
+static void quorum_aio_cancel(BlockAIOCB *blockacb)
+{
+ QuorumAIOCB *acb = container_of(blockacb, QuorumAIOCB, common);
+ BDRVQuorumState *s = acb->common.bs->opaque;
+ int i;
+
+ /* cancel all callbacks */
+ for (i = 0; i < s->num_children; i++) {
+ if (acb->qcrs[i].aiocb) {
+ bdrv_aio_cancel_async(acb->qcrs[i].aiocb);
+ }
+ }
+}
+
+static AIOCBInfo quorum_aiocb_info = {
+ .aiocb_size = sizeof(QuorumAIOCB),
+ .cancel_async = quorum_aio_cancel,
+};
+
+static void quorum_aio_finalize(QuorumAIOCB *acb)
+{
+ int i, ret = 0;
+
+ if (acb->vote_ret) {
+ ret = acb->vote_ret;
+ }
+
+ acb->common.cb(acb->common.opaque, ret);
+
+ if (acb->is_read) {
+ /* on the quorum case acb->child_iter == s->num_children - 1 */
+ for (i = 0; i <= acb->child_iter; i++) {
+ qemu_vfree(acb->qcrs[i].buf);
+ qemu_iovec_destroy(&acb->qcrs[i].qiov);
+ }
+ }
+
+ g_free(acb->qcrs);
+ qemu_aio_unref(acb);
+}
+
+static bool quorum_sha256_compare(QuorumVoteValue *a, QuorumVoteValue *b)
+{
+ return !memcmp(a->h, b->h, HASH_LENGTH);
+}
+
+static bool quorum_64bits_compare(QuorumVoteValue *a, QuorumVoteValue *b)
+{
+ return a->l == b->l;
+}
+
+static QuorumAIOCB *quorum_aio_get(BDRVQuorumState *s,
+ BlockDriverState *bs,
+ QEMUIOVector *qiov,
+ uint64_t sector_num,
+ int nb_sectors,
+ BlockCompletionFunc *cb,
+ void *opaque)
+{
+ QuorumAIOCB *acb = qemu_aio_get(&quorum_aiocb_info, bs, cb, opaque);
+ int i;
+
+ acb->common.bs->opaque = s;
+ acb->sector_num = sector_num;
+ acb->nb_sectors = nb_sectors;
+ acb->qiov = qiov;
+ acb->qcrs = g_new0(QuorumChildRequest, s->num_children);
+ acb->count = 0;
+ acb->success_count = 0;
+ acb->rewrite_count = 0;
+ acb->votes.compare = quorum_sha256_compare;
+ QLIST_INIT(&acb->votes.vote_list);
+ acb->is_read = false;
+ acb->vote_ret = 0;
+
+ for (i = 0; i < s->num_children; i++) {
+ acb->qcrs[i].buf = NULL;
+ acb->qcrs[i].ret = 0;
+ acb->qcrs[i].parent = acb;
+ }
+
+ return acb;
+}
+
+static void quorum_report_bad(QuorumAIOCB *acb, char *node_name, int ret)
+{
+ const char *msg = NULL;
+ if (ret < 0) {
+ msg = strerror(-ret);
+ }
+ qapi_event_send_quorum_report_bad(!!msg, msg, node_name,
+ acb->sector_num, acb->nb_sectors, &error_abort);
+}
+
+static void quorum_report_failure(QuorumAIOCB *acb)
+{
+ const char *reference = bdrv_get_device_or_node_name(acb->common.bs);
+ qapi_event_send_quorum_failure(reference, acb->sector_num,
+ acb->nb_sectors, &error_abort);
+}
+
+static int quorum_vote_error(QuorumAIOCB *acb);
+
+static bool quorum_has_too_much_io_failed(QuorumAIOCB *acb)
+{
+ BDRVQuorumState *s = acb->common.bs->opaque;
+
+ if (acb->success_count < s->threshold) {
+ acb->vote_ret = quorum_vote_error(acb);
+ quorum_report_failure(acb);
+ return true;
+ }
+
+ return false;
+}
+
+static void quorum_rewrite_aio_cb(void *opaque, int ret)
+{
+ QuorumAIOCB *acb = opaque;
+
+ /* one less rewrite to do */
+ acb->rewrite_count--;
+
+ /* wait until all rewrite callbacks have completed */
+ if (acb->rewrite_count) {
+ return;
+ }
+
+ quorum_aio_finalize(acb);
+}
+
+static BlockAIOCB *read_fifo_child(QuorumAIOCB *acb);
+
+static void quorum_copy_qiov(QEMUIOVector *dest, QEMUIOVector *source)
+{
+ int i;
+ assert(dest->niov == source->niov);
+ assert(dest->size == source->size);
+ for (i = 0; i < source->niov; i++) {
+ assert(dest->iov[i].iov_len == source->iov[i].iov_len);
+ memcpy(dest->iov[i].iov_base,
+ source->iov[i].iov_base,
+ source->iov[i].iov_len);
+ }
+}
+
+static void quorum_aio_cb(void *opaque, int ret)
+{
+ QuorumChildRequest *sacb = opaque;
+ QuorumAIOCB *acb = sacb->parent;
+ BDRVQuorumState *s = acb->common.bs->opaque;
+ bool rewrite = false;
+
+ if (acb->is_read && s->read_pattern == QUORUM_READ_PATTERN_FIFO) {
+ /* We try to read next child in FIFO order if we fail to read */
+ if (ret < 0 && ++acb->child_iter < s->num_children) {
+ read_fifo_child(acb);
+ return;
+ }
+
+ if (ret == 0) {
+ quorum_copy_qiov(acb->qiov, &acb->qcrs[acb->child_iter].qiov);
+ }
+ acb->vote_ret = ret;
+ quorum_aio_finalize(acb);
+ return;
+ }
+
+ sacb->ret = ret;
+ acb->count++;
+ if (ret == 0) {
+ acb->success_count++;
+ } else {
+ quorum_report_bad(acb, sacb->aiocb->bs->node_name, ret);
+ }
+ assert(acb->count <= s->num_children);
+ assert(acb->success_count <= s->num_children);
+ if (acb->count < s->num_children) {
+ return;
+ }
+
+ /* Do the vote on read */
+ if (acb->is_read) {
+ rewrite = quorum_vote(acb);
+ } else {
+ quorum_has_too_much_io_failed(acb);
+ }
+
+ /* if no rewrite is done the code will finish right away */
+ if (!rewrite) {
+ quorum_aio_finalize(acb);
+ }
+}
+
+static void quorum_report_bad_versions(BDRVQuorumState *s,
+ QuorumAIOCB *acb,
+ QuorumVoteValue *value)
+{
+ QuorumVoteVersion *version;
+ QuorumVoteItem *item;
+
+ QLIST_FOREACH(version, &acb->votes.vote_list, next) {
+ if (acb->votes.compare(&version->value, value)) {
+ continue;
+ }
+ QLIST_FOREACH(item, &version->items, next) {
+ quorum_report_bad(acb, s->children[item->index]->bs->node_name, 0);
+ }
+ }
+}
+
+static bool quorum_rewrite_bad_versions(BDRVQuorumState *s, QuorumAIOCB *acb,
+ QuorumVoteValue *value)
+{
+ QuorumVoteVersion *version;
+ QuorumVoteItem *item;
+ int count = 0;
+
+ /* first count the number of bad versions: done first to avoid concurrency
+ * issues.
+ */
+ QLIST_FOREACH(version, &acb->votes.vote_list, next) {
+ if (acb->votes.compare(&version->value, value)) {
+ continue;
+ }
+ QLIST_FOREACH(item, &version->items, next) {
+ count++;
+ }
+ }
+
+ /* quorum_rewrite_aio_cb will count down this to zero */
+ acb->rewrite_count = count;
+
+ /* now fire the correcting rewrites */
+ QLIST_FOREACH(version, &acb->votes.vote_list, next) {
+ if (acb->votes.compare(&version->value, value)) {
+ continue;
+ }
+ QLIST_FOREACH(item, &version->items, next) {
+ bdrv_aio_writev(s->children[item->index]->bs, acb->sector_num,
+ acb->qiov, acb->nb_sectors, quorum_rewrite_aio_cb,
+ acb);
+ }
+ }
+
+ /* return true if any rewrite is done else false */
+ return count;
+}
+
+static void quorum_count_vote(QuorumVotes *votes,
+ QuorumVoteValue *value,
+ int index)
+{
+ QuorumVoteVersion *v = NULL, *version = NULL;
+ QuorumVoteItem *item;
+
+ /* look if we have something with this hash */
+ QLIST_FOREACH(v, &votes->vote_list, next) {
+ if (votes->compare(&v->value, value)) {
+ version = v;
+ break;
+ }
+ }
+
+ /* It's a version not yet in the list add it */
+ if (!version) {
+ version = g_new0(QuorumVoteVersion, 1);
+ QLIST_INIT(&version->items);
+ memcpy(&version->value, value, sizeof(version->value));
+ version->index = index;
+ version->vote_count = 0;
+ QLIST_INSERT_HEAD(&votes->vote_list, version, next);
+ }
+
+ version->vote_count++;
+
+ item = g_new0(QuorumVoteItem, 1);
+ item->index = index;
+ QLIST_INSERT_HEAD(&version->items, item, next);
+}
+
+static void quorum_free_vote_list(QuorumVotes *votes)
+{
+ QuorumVoteVersion *version, *next_version;
+ QuorumVoteItem *item, *next_item;
+
+ QLIST_FOREACH_SAFE(version, &votes->vote_list, next, next_version) {
+ QLIST_REMOVE(version, next);
+ QLIST_FOREACH_SAFE(item, &version->items, next, next_item) {
+ QLIST_REMOVE(item, next);
+ g_free(item);
+ }
+ g_free(version);
+ }
+}
+
+static int quorum_compute_hash(QuorumAIOCB *acb, int i, QuorumVoteValue *hash)
+{
+ QEMUIOVector *qiov = &acb->qcrs[i].qiov;
+ size_t len = sizeof(hash->h);
+ uint8_t *data = hash->h;
+
+ /* XXX - would be nice if we could pass in the Error **
+ * and propagate that back, but this quorum code is
+ * restricted to just errno values currently */
+ if (qcrypto_hash_bytesv(QCRYPTO_HASH_ALG_SHA256,
+ qiov->iov, qiov->niov,
+ &data, &len,
+ NULL) < 0) {
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static QuorumVoteVersion *quorum_get_vote_winner(QuorumVotes *votes)
+{
+ int max = 0;
+ QuorumVoteVersion *candidate, *winner = NULL;
+
+ QLIST_FOREACH(candidate, &votes->vote_list, next) {
+ if (candidate->vote_count > max) {
+ max = candidate->vote_count;
+ winner = candidate;
+ }
+ }
+
+ return winner;
+}
+
+/* qemu_iovec_compare is handy for blkverify mode because it returns the first
+ * differing byte location. Yet it is handcoded to compare vectors one byte
+ * after another so it does not benefit from the libc SIMD optimizations.
+ * quorum_iovec_compare is written for speed and should be used in the non
+ * blkverify mode of quorum.
+ */
+static bool quorum_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
+{
+ int i;
+ int result;
+
+ assert(a->niov == b->niov);
+ for (i = 0; i < a->niov; i++) {
+ assert(a->iov[i].iov_len == b->iov[i].iov_len);
+ result = memcmp(a->iov[i].iov_base,
+ b->iov[i].iov_base,
+ a->iov[i].iov_len);
+ if (result) {
+ return false;
+ }
+ }
+
+ return true;
+}
+
+static void GCC_FMT_ATTR(2, 3) quorum_err(QuorumAIOCB *acb,
+ const char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ fprintf(stderr, "quorum: sector_num=%" PRId64 " nb_sectors=%d ",
+ acb->sector_num, acb->nb_sectors);
+ vfprintf(stderr, fmt, ap);
+ fprintf(stderr, "\n");
+ va_end(ap);
+ exit(1);
+}
+
+static bool quorum_compare(QuorumAIOCB *acb,
+ QEMUIOVector *a,
+ QEMUIOVector *b)
+{
+ BDRVQuorumState *s = acb->common.bs->opaque;
+ ssize_t offset;
+
+ /* This driver will replace blkverify in this particular case */
+ if (s->is_blkverify) {
+ offset = qemu_iovec_compare(a, b);
+ if (offset != -1) {
+ quorum_err(acb, "contents mismatch in sector %" PRId64,
+ acb->sector_num +
+ (uint64_t)(offset / BDRV_SECTOR_SIZE));
+ }
+ return true;
+ }
+
+ return quorum_iovec_compare(a, b);
+}
+
+/* Do a vote to get the error code */
+static int quorum_vote_error(QuorumAIOCB *acb)
+{
+ BDRVQuorumState *s = acb->common.bs->opaque;
+ QuorumVoteVersion *winner = NULL;
+ QuorumVotes error_votes;
+ QuorumVoteValue result_value;
+ int i, ret = 0;
+ bool error = false;
+
+ QLIST_INIT(&error_votes.vote_list);
+ error_votes.compare = quorum_64bits_compare;
+
+ for (i = 0; i < s->num_children; i++) {
+ ret = acb->qcrs[i].ret;
+ if (ret) {
+ error = true;
+ result_value.l = ret;
+ quorum_count_vote(&error_votes, &result_value, i);
+ }
+ }
+
+ if (error) {
+ winner = quorum_get_vote_winner(&error_votes);
+ ret = winner->value.l;
+ }
+
+ quorum_free_vote_list(&error_votes);
+
+ return ret;
+}
+
+static bool quorum_vote(QuorumAIOCB *acb)
+{
+ bool quorum = true;
+ bool rewrite = false;
+ int i, j, ret;
+ QuorumVoteValue hash;
+ BDRVQuorumState *s = acb->common.bs->opaque;
+ QuorumVoteVersion *winner;
+
+ if (quorum_has_too_much_io_failed(acb)) {
+ return false;
+ }
+
+ /* get the index of the first successful read */
+ for (i = 0; i < s->num_children; i++) {
+ if (!acb->qcrs[i].ret) {
+ break;
+ }
+ }
+
+ assert(i < s->num_children);
+
+ /* compare this read with all other successful reads stopping at quorum
+ * failure
+ */
+ for (j = i + 1; j < s->num_children; j++) {
+ if (acb->qcrs[j].ret) {
+ continue;
+ }
+ quorum = quorum_compare(acb, &acb->qcrs[i].qiov, &acb->qcrs[j].qiov);
+ if (!quorum) {
+ break;
+ }
+ }
+
+ /* Every successful read agrees */
+ if (quorum) {
+ quorum_copy_qiov(acb->qiov, &acb->qcrs[i].qiov);
+ return false;
+ }
+
+ /* compute hashes for each successful read, also store indexes */
+ for (i = 0; i < s->num_children; i++) {
+ if (acb->qcrs[i].ret) {
+ continue;
+ }
+ ret = quorum_compute_hash(acb, i, &hash);
+ /* if ever the hash computation failed */
+ if (ret < 0) {
+ acb->vote_ret = ret;
+ goto free_exit;
+ }
+ quorum_count_vote(&acb->votes, &hash, i);
+ }
+
+ /* vote to select the most represented version */
+ winner = quorum_get_vote_winner(&acb->votes);
+
+ /* if the winner count is smaller than threshold the read fails */
+ if (winner->vote_count < s->threshold) {
+ quorum_report_failure(acb);
+ acb->vote_ret = -EIO;
+ goto free_exit;
+ }
+
+ /* we have a winner: copy it */
+ quorum_copy_qiov(acb->qiov, &acb->qcrs[winner->index].qiov);
+
+ /* some versions are bad print them */
+ quorum_report_bad_versions(s, acb, &winner->value);
+
+ /* corruption correction is enabled */
+ if (s->rewrite_corrupted) {
+ rewrite = quorum_rewrite_bad_versions(s, acb, &winner->value);
+ }
+
+free_exit:
+ /* free lists */
+ quorum_free_vote_list(&acb->votes);
+ return rewrite;
+}
+
+static BlockAIOCB *read_quorum_children(QuorumAIOCB *acb)
+{
+ BDRVQuorumState *s = acb->common.bs->opaque;
+ int i;
+
+ for (i = 0; i < s->num_children; i++) {
+ acb->qcrs[i].buf = qemu_blockalign(s->children[i]->bs, acb->qiov->size);
+ qemu_iovec_init(&acb->qcrs[i].qiov, acb->qiov->niov);
+ qemu_iovec_clone(&acb->qcrs[i].qiov, acb->qiov, acb->qcrs[i].buf);
+ }
+
+ for (i = 0; i < s->num_children; i++) {
+ acb->qcrs[i].aiocb = bdrv_aio_readv(s->children[i]->bs, acb->sector_num,
+ &acb->qcrs[i].qiov, acb->nb_sectors,
+ quorum_aio_cb, &acb->qcrs[i]);
+ }
+
+ return &acb->common;
+}
+
+static BlockAIOCB *read_fifo_child(QuorumAIOCB *acb)
+{
+ BDRVQuorumState *s = acb->common.bs->opaque;
+
+ acb->qcrs[acb->child_iter].buf =
+ qemu_blockalign(s->children[acb->child_iter]->bs, acb->qiov->size);
+ qemu_iovec_init(&acb->qcrs[acb->child_iter].qiov, acb->qiov->niov);
+ qemu_iovec_clone(&acb->qcrs[acb->child_iter].qiov, acb->qiov,
+ acb->qcrs[acb->child_iter].buf);
+ acb->qcrs[acb->child_iter].aiocb =
+ bdrv_aio_readv(s->children[acb->child_iter]->bs, acb->sector_num,
+ &acb->qcrs[acb->child_iter].qiov, acb->nb_sectors,
+ quorum_aio_cb, &acb->qcrs[acb->child_iter]);
+
+ return &acb->common;
+}
+
+static BlockAIOCB *quorum_aio_readv(BlockDriverState *bs,
+ int64_t sector_num,
+ QEMUIOVector *qiov,
+ int nb_sectors,
+ BlockCompletionFunc *cb,
+ void *opaque)
+{
+ BDRVQuorumState *s = bs->opaque;
+ QuorumAIOCB *acb = quorum_aio_get(s, bs, qiov, sector_num,
+ nb_sectors, cb, opaque);
+ acb->is_read = true;
+
+ if (s->read_pattern == QUORUM_READ_PATTERN_QUORUM) {
+ acb->child_iter = s->num_children - 1;
+ return read_quorum_children(acb);
+ }
+
+ acb->child_iter = 0;
+ return read_fifo_child(acb);
+}
+
+static BlockAIOCB *quorum_aio_writev(BlockDriverState *bs,
+ int64_t sector_num,
+ QEMUIOVector *qiov,
+ int nb_sectors,
+ BlockCompletionFunc *cb,
+ void *opaque)
+{
+ BDRVQuorumState *s = bs->opaque;
+ QuorumAIOCB *acb = quorum_aio_get(s, bs, qiov, sector_num, nb_sectors,
+ cb, opaque);
+ int i;
+
+ for (i = 0; i < s->num_children; i++) {
+ acb->qcrs[i].aiocb = bdrv_aio_writev(s->children[i]->bs, sector_num,
+ qiov, nb_sectors, &quorum_aio_cb,
+ &acb->qcrs[i]);
+ }
+
+ return &acb->common;
+}
+
+static int64_t quorum_getlength(BlockDriverState *bs)
+{
+ BDRVQuorumState *s = bs->opaque;
+ int64_t result;
+ int i;
+
+ /* check that all file have the same length */
+ result = bdrv_getlength(s->children[0]->bs);
+ if (result < 0) {
+ return result;
+ }
+ for (i = 1; i < s->num_children; i++) {
+ int64_t value = bdrv_getlength(s->children[i]->bs);
+ if (value < 0) {
+ return value;
+ }
+ if (value != result) {
+ return -EIO;
+ }
+ }
+
+ return result;
+}
+
+static void quorum_invalidate_cache(BlockDriverState *bs, Error **errp)
+{
+ BDRVQuorumState *s = bs->opaque;
+ Error *local_err = NULL;
+ int i;
+
+ for (i = 0; i < s->num_children; i++) {
+ bdrv_invalidate_cache(s->children[i]->bs, &local_err);
+ if (local_err) {
+ error_propagate(errp, local_err);
+ return;
+ }
+ }
+}
+
+static coroutine_fn int quorum_co_flush(BlockDriverState *bs)
+{
+ BDRVQuorumState *s = bs->opaque;
+ QuorumVoteVersion *winner = NULL;
+ QuorumVotes error_votes;
+ QuorumVoteValue result_value;
+ int i;
+ int result = 0;
+
+ QLIST_INIT(&error_votes.vote_list);
+ error_votes.compare = quorum_64bits_compare;
+
+ for (i = 0; i < s->num_children; i++) {
+ result = bdrv_co_flush(s->children[i]->bs);
+ result_value.l = result;
+ quorum_count_vote(&error_votes, &result_value, i);
+ }
+
+ winner = quorum_get_vote_winner(&error_votes);
+ result = winner->value.l;
+
+ quorum_free_vote_list(&error_votes);
+
+ return result;
+}
+
+static bool quorum_recurse_is_first_non_filter(BlockDriverState *bs,
+ BlockDriverState *candidate)
+{
+ BDRVQuorumState *s = bs->opaque;
+ int i;
+
+ for (i = 0; i < s->num_children; i++) {
+ bool perm = bdrv_recurse_is_first_non_filter(s->children[i]->bs,
+ candidate);
+ if (perm) {
+ return true;
+ }
+ }
+
+ return false;
+}
+
+static int quorum_valid_threshold(int threshold, int num_children, Error **errp)
+{
+
+ if (threshold < 1) {
+ error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
+ "vote-threshold", "value >= 1");
+ return -ERANGE;
+ }
+
+ if (threshold > num_children) {
+ error_setg(errp, "threshold may not exceed children count");
+ return -ERANGE;
+ }
+
+ return 0;
+}
+
+static QemuOptsList quorum_runtime_opts = {
+ .name = "quorum",
+ .head = QTAILQ_HEAD_INITIALIZER(quorum_runtime_opts.head),
+ .desc = {
+ {
+ .name = QUORUM_OPT_VOTE_THRESHOLD,
+ .type = QEMU_OPT_NUMBER,
+ .help = "The number of vote needed for reaching quorum",
+ },
+ {
+ .name = QUORUM_OPT_BLKVERIFY,
+ .type = QEMU_OPT_BOOL,
+ .help = "Trigger block verify mode if set",
+ },
+ {
+ .name = QUORUM_OPT_REWRITE,
+ .type = QEMU_OPT_BOOL,
+ .help = "Rewrite corrupted block on read quorum",
+ },
+ {
+ .name = QUORUM_OPT_READ_PATTERN,
+ .type = QEMU_OPT_STRING,
+ .help = "Allowed pattern: quorum, fifo. Quorum is default",
+ },
+ { /* end of list */ }
+ },
+};
+
+static int parse_read_pattern(const char *opt)
+{
+ int i;
+
+ if (!opt) {
+ /* Set quorum as default */
+ return QUORUM_READ_PATTERN_QUORUM;
+ }
+
+ for (i = 0; i < QUORUM_READ_PATTERN_MAX; i++) {
+ if (!strcmp(opt, QuorumReadPattern_lookup[i])) {
+ return i;
+ }
+ }
+
+ return -EINVAL;
+}
+
+static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
+ Error **errp)
+{
+ BDRVQuorumState *s = bs->opaque;
+ Error *local_err = NULL;
+ QemuOpts *opts = NULL;
+ bool *opened;
+ int i;
+ int ret = 0;
+
+ qdict_flatten(options);
+
+ /* count how many different children are present */
+ s->num_children = qdict_array_entries(options, "children.");
+ if (s->num_children < 0) {
+ error_setg(&local_err, "Option children is not a valid array");
+ ret = -EINVAL;
+ goto exit;
+ }
+ if (s->num_children < 2) {
+ error_setg(&local_err,
+ "Number of provided children must be greater than 1");
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ opts = qemu_opts_create(&quorum_runtime_opts, NULL, 0, &error_abort);
+ qemu_opts_absorb_qdict(opts, options, &local_err);
+ if (local_err) {
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ s->threshold = qemu_opt_get_number(opts, QUORUM_OPT_VOTE_THRESHOLD, 0);
+ /* and validate it against s->num_children */
+ ret = quorum_valid_threshold(s->threshold, s->num_children, &local_err);
+ if (ret < 0) {
+ goto exit;
+ }
+
+ ret = parse_read_pattern(qemu_opt_get(opts, QUORUM_OPT_READ_PATTERN));
+ if (ret < 0) {
+ error_setg(&local_err, "Please set read-pattern as fifo or quorum");
+ goto exit;
+ }
+ s->read_pattern = ret;
+
+ if (s->read_pattern == QUORUM_READ_PATTERN_QUORUM) {
+ /* is the driver in blkverify mode */
+ if (qemu_opt_get_bool(opts, QUORUM_OPT_BLKVERIFY, false) &&
+ s->num_children == 2 && s->threshold == 2) {
+ s->is_blkverify = true;
+ } else if (qemu_opt_get_bool(opts, QUORUM_OPT_BLKVERIFY, false)) {
+ fprintf(stderr, "blkverify mode is set by setting blkverify=on "
+ "and using two files with vote_threshold=2\n");
+ }
+
+ s->rewrite_corrupted = qemu_opt_get_bool(opts, QUORUM_OPT_REWRITE,
+ false);
+ if (s->rewrite_corrupted && s->is_blkverify) {
+ error_setg(&local_err,
+ "rewrite-corrupted=on cannot be used with blkverify=on");
+ ret = -EINVAL;
+ goto exit;
+ }
+ }
+
+ /* allocate the children array */
+ s->children = g_new0(BdrvChild *, s->num_children);
+ opened = g_new0(bool, s->num_children);
+
+ for (i = 0; i < s->num_children; i++) {
+ char indexstr[32];
+ ret = snprintf(indexstr, 32, "children.%d", i);
+ assert(ret < 32);
+
+ s->children[i] = bdrv_open_child(NULL, options, indexstr, bs,
+ &child_format, false, &local_err);
+ if (local_err) {
+ ret = -EINVAL;
+ goto close_exit;
+ }
+
+ opened[i] = true;
+ }
+
+ g_free(opened);
+ goto exit;
+
+close_exit:
+ /* cleanup on error */
+ for (i = 0; i < s->num_children; i++) {
+ if (!opened[i]) {
+ continue;
+ }
+ bdrv_unref_child(bs, s->children[i]);
+ }
+ g_free(s->children);
+ g_free(opened);
+exit:
+ qemu_opts_del(opts);
+ /* propagate error */
+ if (local_err) {
+ error_propagate(errp, local_err);
+ }
+ return ret;
+}
+
+static void quorum_close(BlockDriverState *bs)
+{
+ BDRVQuorumState *s = bs->opaque;
+ int i;
+
+ for (i = 0; i < s->num_children; i++) {
+ bdrv_unref_child(bs, s->children[i]);
+ }
+
+ g_free(s->children);
+}
+
+static void quorum_detach_aio_context(BlockDriverState *bs)
+{
+ BDRVQuorumState *s = bs->opaque;
+ int i;
+
+ for (i = 0; i < s->num_children; i++) {
+ bdrv_detach_aio_context(s->children[i]->bs);
+ }
+}
+
+static void quorum_attach_aio_context(BlockDriverState *bs,
+ AioContext *new_context)
+{
+ BDRVQuorumState *s = bs->opaque;
+ int i;
+
+ for (i = 0; i < s->num_children; i++) {
+ bdrv_attach_aio_context(s->children[i]->bs, new_context);
+ }
+}
+
+static void quorum_refresh_filename(BlockDriverState *bs)
+{
+ BDRVQuorumState *s = bs->opaque;
+ QDict *opts;
+ QList *children;
+ int i;
+
+ for (i = 0; i < s->num_children; i++) {
+ bdrv_refresh_filename(s->children[i]->bs);
+ if (!s->children[i]->bs->full_open_options) {
+ return;
+ }
+ }
+
+ children = qlist_new();
+ for (i = 0; i < s->num_children; i++) {
+ QINCREF(s->children[i]->bs->full_open_options);
+ qlist_append_obj(children,
+ QOBJECT(s->children[i]->bs->full_open_options));
+ }
+
+ opts = qdict_new();
+ qdict_put_obj(opts, "driver", QOBJECT(qstring_from_str("quorum")));
+ qdict_put_obj(opts, QUORUM_OPT_VOTE_THRESHOLD,
+ QOBJECT(qint_from_int(s->threshold)));
+ qdict_put_obj(opts, QUORUM_OPT_BLKVERIFY,
+ QOBJECT(qbool_from_bool(s->is_blkverify)));
+ qdict_put_obj(opts, QUORUM_OPT_REWRITE,
+ QOBJECT(qbool_from_bool(s->rewrite_corrupted)));
+ qdict_put_obj(opts, "children", QOBJECT(children));
+
+ bs->full_open_options = opts;
+}
+
+static BlockDriver bdrv_quorum = {
+ .format_name = "quorum",
+ .protocol_name = "quorum",
+
+ .instance_size = sizeof(BDRVQuorumState),
+
+ .bdrv_file_open = quorum_open,
+ .bdrv_close = quorum_close,
+ .bdrv_refresh_filename = quorum_refresh_filename,
+
+ .bdrv_co_flush_to_disk = quorum_co_flush,
+
+ .bdrv_getlength = quorum_getlength,
+
+ .bdrv_aio_readv = quorum_aio_readv,
+ .bdrv_aio_writev = quorum_aio_writev,
+ .bdrv_invalidate_cache = quorum_invalidate_cache,
+
+ .bdrv_detach_aio_context = quorum_detach_aio_context,
+ .bdrv_attach_aio_context = quorum_attach_aio_context,
+
+ .is_filter = true,
+ .bdrv_recurse_is_first_non_filter = quorum_recurse_is_first_non_filter,
+};
+
+static void bdrv_quorum_init(void)
+{
+ if (!qcrypto_hash_supports(QCRYPTO_HASH_ALG_SHA256)) {
+ /* SHA256 hash support is required for quorum device */
+ return;
+ }
+ bdrv_register(&bdrv_quorum);
+}
+
+block_init(bdrv_quorum_init);
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