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qemu/block/quorum.c

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/*
* 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 <gnutls/gnutls.h>
#include <gnutls/crypto.h>
#include "block/block_int.h"
#include "qapi/qmp/qjson.h"
#define HASH_LENGTH 32
#define QUORUM_OPT_VOTE_THRESHOLD "vote-threshold"
#define QUORUM_OPT_BLKVERIFY "blkverify"
/* This union holds a vote hash value */
typedef union QuorumVoteValue {
char 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 {
BlockDriverState **bs; /* 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.
*/
} 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 {
BlockDriverAIOCB *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 {
BlockDriverAIOCB 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 */
QuorumVotes votes;
bool is_read;
int vote_ret;
};
static void quorum_vote(QuorumAIOCB *acb);
static void quorum_aio_cancel(BlockDriverAIOCB *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++) {
bdrv_aio_cancel(acb->qcrs[i].aiocb);
}
g_free(acb->qcrs);
qemu_aio_release(acb);
}
static AIOCBInfo quorum_aiocb_info = {
.aiocb_size = sizeof(QuorumAIOCB),
.cancel = quorum_aio_cancel,
};
static void quorum_aio_finalize(QuorumAIOCB *acb)
{
BDRVQuorumState *s = acb->common.bs->opaque;
int i, ret = 0;
if (acb->vote_ret) {
ret = acb->vote_ret;
}
acb->common.cb(acb->common.opaque, ret);
if (acb->is_read) {
for (i = 0; i < s->num_children; i++) {
qemu_vfree(acb->qcrs[i].buf);
qemu_iovec_destroy(&acb->qcrs[i].qiov);
}
}
g_free(acb->qcrs);
qemu_aio_release(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,
BlockDriverCompletionFunc *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->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)
{
QObject *data;
assert(node_name);
data = qobject_from_jsonf("{ 'node-name': %s"
", 'sector-num': %" PRId64
", 'sectors-count': %d }",
node_name, acb->sector_num, acb->nb_sectors);
if (ret < 0) {
QDict *dict = qobject_to_qdict(data);
qdict_put(dict, "error", qstring_from_str(strerror(-ret)));
}
monitor_protocol_event(QEVENT_QUORUM_REPORT_BAD, data);
qobject_decref(data);
}
static void quorum_report_failure(QuorumAIOCB *acb)
{
QObject *data;
const char *reference = acb->common.bs->device_name[0] ?
acb->common.bs->device_name :
acb->common.bs->node_name;
data = qobject_from_jsonf("{ 'reference': %s"
", 'sector-num': %" PRId64
", 'sectors-count': %d }",
reference, acb->sector_num, acb->nb_sectors);
monitor_protocol_event(QEVENT_QUORUM_FAILURE, data);
qobject_decref(data);
}
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_aio_cb(void *opaque, int ret)
{
QuorumChildRequest *sacb = opaque;
QuorumAIOCB *acb = sacb->parent;
BDRVQuorumState *s = acb->common.bs->opaque;
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) {
quorum_vote(acb);
} else {
quorum_has_too_much_io_failed(acb);
}
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->bs[item->index]->node_name, 0);
}
}
}
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_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)
{
int j, ret;
gnutls_hash_hd_t dig;
QEMUIOVector *qiov = &acb->qcrs[i].qiov;
ret = gnutls_hash_init(&dig, GNUTLS_DIG_SHA256);
if (ret < 0) {
return ret;
}
for (j = 0; j < qiov->niov; j++) {
ret = gnutls_hash(dig, qiov->iov[j].iov_base, qiov->iov[j].iov_len);
if (ret < 0) {
break;
}
}
gnutls_hash_deinit(dig, (void *) hash);
return ret;
}
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 void quorum_vote(QuorumAIOCB *acb)
{
bool quorum = true;
int i, j, ret;
QuorumVoteValue hash;
BDRVQuorumState *s = acb->common.bs->opaque;
QuorumVoteVersion *winner;
if (quorum_has_too_much_io_failed(acb)) {
return;
}
/* 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;
}
/* 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);
free_exit:
/* free lists */
quorum_free_vote_list(&acb->votes);
}
static BlockDriverAIOCB *quorum_aio_readv(BlockDriverState *bs,
int64_t sector_num,
QEMUIOVector *qiov,
int nb_sectors,
BlockDriverCompletionFunc *cb,
void *opaque)
{
BDRVQuorumState *s = bs->opaque;
QuorumAIOCB *acb = quorum_aio_get(s, bs, qiov, sector_num,
nb_sectors, cb, opaque);
int i;
acb->is_read = true;
for (i = 0; i < s->num_children; i++) {
acb->qcrs[i].buf = qemu_blockalign(s->bs[i], qiov->size);
qemu_iovec_init(&acb->qcrs[i].qiov, qiov->niov);
qemu_iovec_clone(&acb->qcrs[i].qiov, qiov, acb->qcrs[i].buf);
}
for (i = 0; i < s->num_children; i++) {
bdrv_aio_readv(s->bs[i], sector_num, &acb->qcrs[i].qiov, nb_sectors,
quorum_aio_cb, &acb->qcrs[i]);
}
return &acb->common;
}
static BlockDriverAIOCB *quorum_aio_writev(BlockDriverState *bs,
int64_t sector_num,
QEMUIOVector *qiov,
int nb_sectors,
BlockDriverCompletionFunc *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->bs[i], 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->bs[0]);
if (result < 0) {
return result;
}
for (i = 1; i < s->num_children; i++) {
int64_t value = bdrv_getlength(s->bs[i]);
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->bs[i], &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->bs[i]);
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->bs[i],
candidate);
if (perm) {
return true;
}
}
return false;
}
static int quorum_valid_threshold(int threshold, int num_children, Error **errp)
{
if (threshold < 1) {
error_set(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",
},
{ /* end of list */ }
},
};
static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
BDRVQuorumState *s = bs->opaque;
Error *local_err = NULL;
QemuOpts *opts;
bool *opened;
QDict *sub = NULL;
QList *list = NULL;
const QListEntry *lentry;
int i;
int ret = 0;
qdict_flatten(options);
qdict_extract_subqdict(options, &sub, "children.");
qdict_array_split(sub, &list);
if (qdict_size(sub)) {
error_setg(&local_err, "Invalid option children.%s",
qdict_first(sub)->key);
ret = -EINVAL;
goto exit;
}
/* count how many different children are present */
s->num_children = qlist_size(list);
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;
}
/* 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");
}
/* allocate the children BlockDriverState array */
s->bs = g_new0(BlockDriverState *, s->num_children);
opened = g_new0(bool, s->num_children);
for (i = 0, lentry = qlist_first(list); lentry;
lentry = qlist_next(lentry), i++) {
QDict *d;
QString *string;
switch (qobject_type(lentry->value))
{
/* List of options */
case QTYPE_QDICT:
d = qobject_to_qdict(lentry->value);
QINCREF(d);
ret = bdrv_open(&s->bs[i], NULL, NULL, d, flags, NULL,
&local_err);
break;
/* QMP reference */
case QTYPE_QSTRING:
string = qobject_to_qstring(lentry->value);
ret = bdrv_open(&s->bs[i], NULL, qstring_get_str(string), NULL,
flags, NULL, &local_err);
break;
default:
error_setg(&local_err, "Specification of child block device %i "
"is invalid", i);
ret = -EINVAL;
}
if (ret < 0) {
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(s->bs[i]);
}
g_free(s->bs);
g_free(opened);
exit:
/* propagate error */
if (local_err) {
error_propagate(errp, local_err);
}
QDECREF(list);
QDECREF(sub);
return ret;
}
static void quorum_close(BlockDriverState *bs)
{
BDRVQuorumState *s = bs->opaque;
int i;
for (i = 0; i < s->num_children; i++) {
bdrv_unref(s->bs[i]);
}
g_free(s->bs);
}
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->bs[i]);
}
}
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->bs[i], new_context);
}
}
static BlockDriver bdrv_quorum = {
.format_name = "quorum",
.protocol_name = "quorum",
.instance_size = sizeof(BDRVQuorumState),
.bdrv_file_open = quorum_open,
.bdrv_close = quorum_close,
.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)
{
bdrv_register(&bdrv_quorum);
}
block_init(bdrv_quorum_init);
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