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qemu/block/quorum.c
Kevin Wolf 4026f1c4f3 block: Mark bdrv_get_parent_name() and callers GRAPH_RDLOCK 
This adds GRAPH_RDLOCK annotations to declare that callers of
bdrv_get_parent_name() need to hold a reader lock for the graph
because it accesses the parents list of a node.

For some places, we know that they will hold the lock, but we don't have
the GRAPH_RDLOCK annotations yet. In this case, add assume_graph_lock()
with a FIXME comment. These places will be removed once everything is
properly annotated.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20230929145157.45443-13-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-10-12 16:31:33 +02:00

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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 "qemu/osdep.h"
#include "qemu/cutils.h"
#include "qemu/module.h"
#include "qemu/option.h"
#include "qemu/memalign.h"
#include "block/block_int.h"
#include "block/coroutines.h"
#include "block/qdict.h"
#include "qapi/error.h"
#include "qapi/qapi-events-block.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qerror.h"
#include "qapi/qmp/qlist.h"
#include "qapi/qmp/qstring.h"
#include "crypto/hash.h"
#define HASH_LENGTH 32
#define INDEXSTR_LEN 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 */
unsigned next_child_index; /* the index of the next child that should
* be added
*/
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 {
BlockDriverState *bs;
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 {
BlockDriverState *bs;
Coroutine *co;
/* Request metadata */
uint64_t offset;
uint64_t bytes;
int flags;
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 children_read; /* how many children have been read from */
};
typedef struct QuorumCo {
QuorumAIOCB *acb;
int idx;
} QuorumCo;
static void quorum_aio_finalize(QuorumAIOCB *acb)
{
g_free(acb->qcrs);
g_free(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 *coroutine_fn quorum_aio_get(BlockDriverState *bs,
QEMUIOVector *qiov,
uint64_t offset, uint64_t bytes,
int flags)
{
BDRVQuorumState *s = bs->opaque;
QuorumAIOCB *acb = g_new(QuorumAIOCB, 1);
int i;
*acb = (QuorumAIOCB) {
.co = qemu_coroutine_self(),
.bs = bs,
.offset = offset,
.bytes = bytes,
.flags = flags,
.qiov = qiov,
.votes.compare = quorum_sha256_compare,
.votes.vote_list = QLIST_HEAD_INITIALIZER(acb.votes.vote_list),
};
acb->qcrs = g_new0(QuorumChildRequest, s->num_children);
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(QuorumOpType type, uint64_t offset,
uint64_t bytes, char *node_name, int ret)
{
const char *msg = NULL;
int64_t start_sector = offset / BDRV_SECTOR_SIZE;
int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
if (ret < 0) {
msg = strerror(-ret);
}
qapi_event_send_quorum_report_bad(type, msg, node_name, start_sector,
end_sector - start_sector);
}
static void GRAPH_RDLOCK quorum_report_failure(QuorumAIOCB *acb)
{
const char *reference = bdrv_get_device_or_node_name(acb->bs);
int64_t start_sector = acb->offset / BDRV_SECTOR_SIZE;
int64_t end_sector = DIV_ROUND_UP(acb->offset + acb->bytes,
BDRV_SECTOR_SIZE);
qapi_event_send_quorum_failure(reference, start_sector,
end_sector - start_sector);
}
static int quorum_vote_error(QuorumAIOCB *acb);
static bool GRAPH_RDLOCK quorum_has_too_much_io_failed(QuorumAIOCB *acb)
{
BDRVQuorumState *s = acb->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_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_report_bad_acb(QuorumChildRequest *sacb, int ret)
{
QuorumAIOCB *acb = sacb->parent;
QuorumOpType type = acb->is_read ? QUORUM_OP_TYPE_READ : QUORUM_OP_TYPE_WRITE;
quorum_report_bad(type, acb->offset, acb->bytes, sacb->bs->node_name, ret);
}
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(QUORUM_OP_TYPE_READ, acb->offset, acb->bytes,
s->children[item->index]->bs->node_name, 0);
}
}
}
/*
* This function can count as GRAPH_RDLOCK because read_quorum_children() holds
* the graph lock and keeps it until this coroutine has terminated.
*/
static void coroutine_fn GRAPH_RDLOCK quorum_rewrite_entry(void *opaque)
{
QuorumCo *co = opaque;
QuorumAIOCB *acb = co->acb;
BDRVQuorumState *s = acb->bs->opaque;
/* Ignore any errors, it's just a correction attempt for already
* corrupted data.
* Mask out BDRV_REQ_WRITE_UNCHANGED because this overwrites the
* area with different data from the other children. */
bdrv_co_pwritev(s->children[co->idx], acb->offset, acb->bytes,
acb->qiov, acb->flags & ~BDRV_REQ_WRITE_UNCHANGED);
/* Wake up the caller after the last rewrite */
acb->rewrite_count--;
if (!acb->rewrite_count) {
qemu_coroutine_enter_if_inactive(acb->co);
}
}
static bool coroutine_fn GRAPH_RDLOCK
quorum_rewrite_bad_versions(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_entry 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) {
Coroutine *co;
QuorumCo data = {
.acb = acb,
.idx = item->index,
};
co = qemu_coroutine_create(quorum_rewrite_entry, &data);
qemu_coroutine_enter(co);
}
}
/* 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 bool quorum_compare(QuorumAIOCB *acb, QEMUIOVector *a, QEMUIOVector *b)
{
BDRVQuorumState *s = acb->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) {
fprintf(stderr, "quorum: offset=%" PRIu64 " bytes=%" PRIu64
" contents mismatch at offset %" PRIu64 "\n",
acb->offset, acb->bytes, acb->offset + offset);
exit(1);
}
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->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 coroutine_fn GRAPH_RDLOCK quorum_vote(QuorumAIOCB *acb)
{
bool quorum = true;
int i, j, ret;
QuorumVoteValue hash;
BDRVQuorumState *s = acb->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);
/* corruption correction is enabled */
if (s->rewrite_corrupted) {
quorum_rewrite_bad_versions(acb, &winner->value);
}
free_exit:
/* free lists */
quorum_free_vote_list(&acb->votes);
}
/*
* This function can count as GRAPH_RDLOCK because read_quorum_children() holds
* the graph lock and keeps it until this coroutine has terminated.
*/
static void coroutine_fn GRAPH_RDLOCK read_quorum_children_entry(void *opaque)
{
QuorumCo *co = opaque;
QuorumAIOCB *acb = co->acb;
BDRVQuorumState *s = acb->bs->opaque;
int i = co->idx;
QuorumChildRequest *sacb = &acb->qcrs[i];
sacb->bs = s->children[i]->bs;
sacb->ret = bdrv_co_preadv(s->children[i], acb->offset, acb->bytes,
&acb->qcrs[i].qiov, 0);
if (sacb->ret == 0) {
acb->success_count++;
} else {
quorum_report_bad_acb(sacb, sacb->ret);
}
acb->count++;
assert(acb->count <= s->num_children);
assert(acb->success_count <= s->num_children);
/* Wake up the caller after the last read */
if (acb->count == s->num_children) {
qemu_coroutine_enter_if_inactive(acb->co);
}
}
static int coroutine_fn GRAPH_RDLOCK read_quorum_children(QuorumAIOCB *acb)
{
BDRVQuorumState *s = acb->bs->opaque;
int i;
acb->children_read = s->num_children;
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++) {
Coroutine *co;
QuorumCo data = {
.acb = acb,
.idx = i,
};
co = qemu_coroutine_create(read_quorum_children_entry, &data);
qemu_coroutine_enter(co);
}
while (acb->count < s->num_children) {
qemu_coroutine_yield();
}
/* Do the vote on read */
quorum_vote(acb);
for (i = 0; i < s->num_children; i++) {
qemu_vfree(acb->qcrs[i].buf);
qemu_iovec_destroy(&acb->qcrs[i].qiov);
}
while (acb->rewrite_count) {
qemu_coroutine_yield();
}
return acb->vote_ret;
}
static int coroutine_fn GRAPH_RDLOCK read_fifo_child(QuorumAIOCB *acb)
{
BDRVQuorumState *s = acb->bs->opaque;
int n, ret;
/* We try to read the next child in FIFO order if we failed to read */
do {
n = acb->children_read++;
acb->qcrs[n].bs = s->children[n]->bs;
ret = bdrv_co_preadv(s->children[n], acb->offset, acb->bytes,
acb->qiov, 0);
if (ret < 0) {
quorum_report_bad_acb(&acb->qcrs[n], ret);
}
} while (ret < 0 && acb->children_read < s->num_children);
/* FIXME: rewrite failed children if acb->children_read > 1? */
return ret;
}
static int coroutine_fn GRAPH_RDLOCK
quorum_co_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, BdrvRequestFlags flags)
{
BDRVQuorumState *s = bs->opaque;
QuorumAIOCB *acb = quorum_aio_get(bs, qiov, offset, bytes, flags);
int ret;
acb->is_read = true;
acb->children_read = 0;
if (s->read_pattern == QUORUM_READ_PATTERN_QUORUM) {
ret = read_quorum_children(acb);
} else {
ret = read_fifo_child(acb);
}
quorum_aio_finalize(acb);
return ret;
}
/*
* This function can count as GRAPH_RDLOCK because quorum_co_pwritev() holds the
* graph lock and keeps it until this coroutine has terminated.
*/
static void coroutine_fn GRAPH_RDLOCK write_quorum_entry(void *opaque)
{
QuorumCo *co = opaque;
QuorumAIOCB *acb = co->acb;
BDRVQuorumState *s = acb->bs->opaque;
int i = co->idx;
QuorumChildRequest *sacb = &acb->qcrs[i];
sacb->bs = s->children[i]->bs;
if (acb->flags & BDRV_REQ_ZERO_WRITE) {
sacb->ret = bdrv_co_pwrite_zeroes(s->children[i], acb->offset,
acb->bytes, acb->flags);
} else {
sacb->ret = bdrv_co_pwritev(s->children[i], acb->offset, acb->bytes,
acb->qiov, acb->flags);
}
if (sacb->ret == 0) {
acb->success_count++;
} else {
quorum_report_bad_acb(sacb, sacb->ret);
}
acb->count++;
assert(acb->count <= s->num_children);
assert(acb->success_count <= s->num_children);
/* Wake up the caller after the last write */
if (acb->count == s->num_children) {
qemu_coroutine_enter_if_inactive(acb->co);
}
}
static int coroutine_fn GRAPH_RDLOCK
quorum_co_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, BdrvRequestFlags flags)
{
BDRVQuorumState *s = bs->opaque;
QuorumAIOCB *acb = quorum_aio_get(bs, qiov, offset, bytes, flags);
int i, ret;
for (i = 0; i < s->num_children; i++) {
Coroutine *co;
QuorumCo data = {
.acb = acb,
.idx = i,
};
co = qemu_coroutine_create(write_quorum_entry, &data);
qemu_coroutine_enter(co);
}
while (acb->count < s->num_children) {
qemu_coroutine_yield();
}
quorum_has_too_much_io_failed(acb);
ret = acb->vote_ret;
quorum_aio_finalize(acb);
return ret;
}
static int coroutine_fn GRAPH_RDLOCK
quorum_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int64_t bytes,
BdrvRequestFlags flags)
{
return quorum_co_pwritev(bs, offset, bytes, NULL,
flags | BDRV_REQ_ZERO_WRITE);
}
static int64_t coroutine_fn GRAPH_RDLOCK
quorum_co_getlength(BlockDriverState *bs)
{
BDRVQuorumState *s = bs->opaque;
int64_t result;
int i;
/* check that all file have the same length */
result = bdrv_co_getlength(s->children[0]->bs);
if (result < 0) {
return result;
}
for (i = 1; i < s->num_children; i++) {
int64_t value = bdrv_co_getlength(s->children[i]->bs);
if (value < 0) {
return value;
}
if (value != result) {
return -EIO;
}
}
return result;
}
static coroutine_fn GRAPH_RDLOCK int quorum_co_flush(BlockDriverState *bs)
{
BDRVQuorumState *s = bs->opaque;
QuorumVoteVersion *winner = NULL;
QuorumVotes error_votes;
QuorumVoteValue result_value;
int i;
int result = 0;
int success_count = 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);
if (result) {
quorum_report_bad(QUORUM_OP_TYPE_FLUSH, 0, 0,
s->children[i]->bs->node_name, result);
result_value.l = result;
quorum_count_vote(&error_votes, &result_value, i);
} else {
success_count++;
}
}
if (success_count >= s->threshold) {
result = 0;
} else {
winner = quorum_get_vote_winner(&error_votes);
result = winner->value.l;
}
quorum_free_vote_list(&error_votes);
return result;
}
static bool GRAPH_RDLOCK
quorum_recurse_can_replace(BlockDriverState *bs, BlockDriverState *to_replace)
{
BDRVQuorumState *s = bs->opaque;
int i;
for (i = 0; i < s->num_children; i++) {
/*
* We have no idea whether our children show the same data as
* this node (@bs). It is actually highly likely that
* @to_replace does not, because replacing a broken child is
* one of the main use cases here.
*
* We do know that the new BDS will match @bs, so replacing
* any of our children by it will be safe. It cannot change
* the data this quorum node presents to its parents.
*
* However, replacing @to_replace by @bs in any of our
* children's chains may change visible data somewhere in
* there. We therefore cannot recurse down those chains with
* bdrv_recurse_can_replace().
* (More formally, bdrv_recurse_can_replace() requires that
* @to_replace will be replaced by something matching the @bs
* passed to it. We cannot guarantee that.)
*
* Thus, we can only check whether any of our immediate
* children matches @to_replace.
*
* (In the future, we might add a function to recurse down a
* chain that checks that nothing there cares about a change
* in data from the respective child in question. For
* example, most filters do not care when their child's data
* suddenly changes, as long as their parents do not care.)
*/
if (s->children[i]->bs == to_replace) {
/*
* We now have to ensure that there is no other parent
* that cares about replacing this child by a node with
* potentially different data.
* We do so by checking whether there are any other parents
* at all, which is stricter than necessary, but also very
* simple. (We may decide to implement something more
* complex and permissive when there is an actual need for
* it.)
*/
return QLIST_FIRST(&to_replace->parents) == s->children[i] &&
QLIST_NEXT(s->children[i], next_parent) == NULL;
}
}
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", "a 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 void quorum_refresh_flags(BlockDriverState *bs)
{
BDRVQuorumState *s = bs->opaque;
int i;
bs->supported_zero_flags =
BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK;
for (i = 0; i < s->num_children; i++) {
bs->supported_zero_flags &= s->children[i]->bs->supported_zero_flags;
}
bs->supported_zero_flags |= BDRV_REQ_WRITE_UNCHANGED;
}
static int quorum_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
BDRVQuorumState *s = bs->opaque;
QemuOpts *opts = NULL;
const char *pattern_str;
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(errp, "Option children is not a valid array");
ret = -EINVAL;
goto exit;
}
if (s->num_children < 1) {
error_setg(errp, "Number of provided children must be 1 or more");
ret = -EINVAL;
goto exit;
}
opts = qemu_opts_create(&quorum_runtime_opts, NULL, 0, &error_abort);
if (!qemu_opts_absorb_qdict(opts, options, errp)) {
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, errp);
if (ret < 0) {
goto exit;
}
pattern_str = qemu_opt_get(opts, QUORUM_OPT_READ_PATTERN);
if (!pattern_str) {
ret = QUORUM_READ_PATTERN_QUORUM;
} else {
ret = qapi_enum_parse(&QuorumReadPattern_lookup, pattern_str,
-EINVAL, NULL);
}
if (ret < 0) {
error_setg(errp, "Please set read-pattern as fifo or quorum");
goto exit;
}
s->read_pattern = ret;
if (s->read_pattern == QUORUM_READ_PATTERN_QUORUM) {
s->is_blkverify = qemu_opt_get_bool(opts, QUORUM_OPT_BLKVERIFY, false);
if (s->is_blkverify && (s->num_children != 2 || s->threshold != 2)) {
error_setg(errp, "blkverify=on can only be set if there are "
"exactly two files and vote-threshold is 2");
ret = -EINVAL;
goto exit;
}
s->rewrite_corrupted = qemu_opt_get_bool(opts, QUORUM_OPT_REWRITE,
false);
if (s->rewrite_corrupted && s->is_blkverify) {
error_setg(errp,
"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[INDEXSTR_LEN];
ret = snprintf(indexstr, INDEXSTR_LEN, "children.%d", i);
assert(ret < INDEXSTR_LEN);
s->children[i] = bdrv_open_child(NULL, options, indexstr, bs,
&child_of_bds, BDRV_CHILD_DATA, false,
errp);
if (!s->children[i]) {
ret = -EINVAL;
goto close_exit;
}
opened[i] = true;
}
s->next_child_index = s->num_children;
bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED;
quorum_refresh_flags(bs);
g_free(opened);
goto exit;
close_exit:
/* cleanup on error */
bdrv_graph_wrlock(NULL);
for (i = 0; i < s->num_children; i++) {
if (!opened[i]) {
continue;
}
bdrv_unref_child(bs, s->children[i]);
}
bdrv_graph_wrunlock();
g_free(s->children);
g_free(opened);
exit:
qemu_opts_del(opts);
return ret;
}
static void quorum_close(BlockDriverState *bs)
{
BDRVQuorumState *s = bs->opaque;
int i;
bdrv_graph_wrlock(NULL);
for (i = 0; i < s->num_children; i++) {
bdrv_unref_child(bs, s->children[i]);
}
bdrv_graph_wrunlock();
g_free(s->children);
}
static void GRAPH_WRLOCK
quorum_add_child(BlockDriverState *bs, BlockDriverState *child_bs, Error **errp)
{
BDRVQuorumState *s = bs->opaque;
BdrvChild *child;
char indexstr[INDEXSTR_LEN];
int ret;
if (s->is_blkverify) {
error_setg(errp, "Cannot add a child to a quorum in blkverify mode");
return;
}
assert(s->num_children <= INT_MAX / sizeof(BdrvChild *));
if (s->num_children == INT_MAX / sizeof(BdrvChild *) ||
s->next_child_index == UINT_MAX) {
error_setg(errp, "Too many children");
return;
}
ret = snprintf(indexstr, INDEXSTR_LEN, "children.%u", s->next_child_index);
if (ret < 0 || ret >= INDEXSTR_LEN) {
error_setg(errp, "cannot generate child name");
return;
}
s->next_child_index++;
/* We can safely add the child now */
bdrv_ref(child_bs);
child = bdrv_attach_child(bs, child_bs, indexstr, &child_of_bds,
BDRV_CHILD_DATA, errp);
if (child == NULL) {
s->next_child_index--;
return;
}
s->children = g_renew(BdrvChild *, s->children, s->num_children + 1);
s->children[s->num_children++] = child;
quorum_refresh_flags(bs);
}
static void GRAPH_WRLOCK
quorum_del_child(BlockDriverState *bs, BdrvChild *child, Error **errp)
{
BDRVQuorumState *s = bs->opaque;
char indexstr[INDEXSTR_LEN];
int i;
for (i = 0; i < s->num_children; i++) {
if (s->children[i] == child) {
break;
}
}
/* we have checked it in bdrv_del_child() */
assert(i < s->num_children);
if (s->num_children <= s->threshold) {
error_setg(errp,
"The number of children cannot be lower than the vote threshold %d",
s->threshold);
return;
}
/* We know now that num_children > threshold, so blkverify must be false */
assert(!s->is_blkverify);
snprintf(indexstr, INDEXSTR_LEN, "children.%u", s->next_child_index - 1);
if (!strncmp(child->name, indexstr, INDEXSTR_LEN)) {
s->next_child_index--;
}
/* We can safely remove this child now */
memmove(&s->children[i], &s->children[i + 1],
(s->num_children - i - 1) * sizeof(BdrvChild *));
s->children = g_renew(BdrvChild *, s->children, --s->num_children);
bdrv_unref_child(bs, child);
quorum_refresh_flags(bs);
}
static void quorum_gather_child_options(BlockDriverState *bs, QDict *target,
bool backing_overridden)
{
BDRVQuorumState *s = bs->opaque;
QList *children_list;
int i;
/*
* The generic implementation for gathering child options in
* bdrv_refresh_filename() would use the names of the children
* as specified for bdrv_open_child() or bdrv_attach_child(),
* which is "children.%u" with %u being a value
* (s->next_child_index) that is incremented each time a new child
* is added (and never decremented). Since children can be
* deleted at runtime, there may be gaps in that enumeration.
* When creating a new quorum BDS and specifying the children for
* it through runtime options, the enumeration used there may not
* have any gaps, though.
*
* Therefore, we have to create a new gap-less enumeration here
* (which we can achieve by simply putting all of the children's
* full_open_options into a QList).
*
* XXX: Note that there are issues with the current child option
* structure quorum uses (such as the fact that children do
* not really have unique permanent names). Therefore, this
* is going to have to change in the future and ideally we
* want quorum to be covered by the generic implementation.
*/
children_list = qlist_new();
qdict_put(target, "children", children_list);
for (i = 0; i < s->num_children; i++) {
qlist_append(children_list,
qobject_ref(s->children[i]->bs->full_open_options));
}
}
static char *quorum_dirname(BlockDriverState *bs, Error **errp)
{
/* In general, there are multiple BDSs with different dirnames below this
* one; so there is no unique dirname we could return (unless all are equal
* by chance, or there is only one). Therefore, to be consistent, just
* always return NULL. */
error_setg(errp, "Cannot generate a base directory for quorum nodes");
return NULL;
}
static void quorum_child_perm(BlockDriverState *bs, BdrvChild *c,
BdrvChildRole role,
BlockReopenQueue *reopen_queue,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
BDRVQuorumState *s = bs->opaque;
*nperm = perm & DEFAULT_PERM_PASSTHROUGH;
if (s->rewrite_corrupted) {
*nperm |= BLK_PERM_WRITE;
}
/*
* We cannot share RESIZE or WRITE, as this would make the
* children differ from each other.
*/
*nshared = (shared & (BLK_PERM_CONSISTENT_READ |
BLK_PERM_WRITE_UNCHANGED))
| DEFAULT_PERM_UNCHANGED;
}
/*
* Each one of the children can report different status flags even
* when they contain the same data, so what this function does is
* return BDRV_BLOCK_ZERO if *all* children agree that a certain
* region contains zeroes, and BDRV_BLOCK_DATA otherwise.
*/
static int coroutine_fn GRAPH_RDLOCK
quorum_co_block_status(BlockDriverState *bs, bool want_zero,
int64_t offset, int64_t count,
int64_t *pnum, int64_t *map, BlockDriverState **file)
{
BDRVQuorumState *s = bs->opaque;
int i, ret;
int64_t pnum_zero = count;
int64_t pnum_data = 0;
for (i = 0; i < s->num_children; i++) {
int64_t bytes;
ret = bdrv_co_common_block_status_above(s->children[i]->bs, NULL, false,
want_zero, offset, count,
&bytes, NULL, NULL, NULL);
if (ret < 0) {
quorum_report_bad(QUORUM_OP_TYPE_READ, offset, count,
s->children[i]->bs->node_name, ret);
pnum_data = count;
break;
}
/*
* Even if all children agree about whether there are zeroes
* or not at @offset they might disagree on the size, so use
* the smallest when reporting BDRV_BLOCK_ZERO and the largest
* when reporting BDRV_BLOCK_DATA.
*/
if (ret & BDRV_BLOCK_ZERO) {
pnum_zero = MIN(pnum_zero, bytes);
} else {
pnum_data = MAX(pnum_data, bytes);
}
}
if (pnum_data) {
*pnum = pnum_data;
return BDRV_BLOCK_DATA;
} else {
*pnum = pnum_zero;
return BDRV_BLOCK_ZERO;
}
}
static const char *const quorum_strong_runtime_opts[] = {
QUORUM_OPT_VOTE_THRESHOLD,
QUORUM_OPT_BLKVERIFY,
QUORUM_OPT_REWRITE,
QUORUM_OPT_READ_PATTERN,
NULL
};
static BlockDriver bdrv_quorum = {
.format_name = "quorum",
.instance_size = sizeof(BDRVQuorumState),
.bdrv_open = quorum_open,
.bdrv_close = quorum_close,
.bdrv_gather_child_options = quorum_gather_child_options,
.bdrv_dirname = quorum_dirname,
.bdrv_co_block_status = quorum_co_block_status,
.bdrv_co_flush = quorum_co_flush,
.bdrv_co_getlength = quorum_co_getlength,
.bdrv_co_preadv = quorum_co_preadv,
.bdrv_co_pwritev = quorum_co_pwritev,
.bdrv_co_pwrite_zeroes = quorum_co_pwrite_zeroes,
.bdrv_add_child = quorum_add_child,
.bdrv_del_child = quorum_del_child,
.bdrv_child_perm = quorum_child_perm,
.bdrv_recurse_can_replace = quorum_recurse_can_replace,
.strong_runtime_opts = quorum_strong_runtime_opts,
};
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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