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qemu/block/replication.c
Emanuele Giuseppe Esposito c86422c554 block: Convert bdrv_refresh_total_sectors() to co_wrapper_mixed 
BlockDriver->bdrv_getlength is categorized as IO callback, and it
currently doesn't run in a coroutine. We should let it take a graph
rdlock since the callback traverses the block nodes graph, which however
is only possible in a coroutine.

Therefore turn it into a co_wrapper to move the actual function into a
coroutine where the lock can be taken.

Because now this function creates a new coroutine and polls, we need to
take the AioContext lock where it is missing, for the only reason that
internally co_wrapper calls AIO_WAIT_WHILE and it expects to release the
AioContext lock.

This is especially messy when a co_wrapper creates a coroutine and polls
in bdrv_open_driver, because this function has so many callers in so
many context that it can easily lead to deadlocks. Therefore the new
rule for bdrv_open_driver is that the caller must always hold the
AioContext lock of the given bs (except if it is a coroutine), because
the function calls bdrv_refresh_total_sectors() which is now a
co_wrapper.

Once the rwlock is ultimated and placed in every place it needs to be,
we will poll using AIO_WAIT_WHILE_UNLOCKED and remove the AioContext
lock.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230113204212.359076-7-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-02-01 16:52:32 +01:00

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/*
* Replication Block filter
*
* Copyright (c) 2016 HUAWEI TECHNOLOGIES CO., LTD.
* Copyright (c) 2016 Intel Corporation
* Copyright (c) 2016 FUJITSU LIMITED
*
* Author:
* Wen Congyang <wency@cn.fujitsu.com>
*
* 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/module.h"
#include "qemu/option.h"
#include "block/nbd.h"
#include "block/blockjob.h"
#include "block/block_int.h"
#include "block/block_backup.h"
#include "sysemu/block-backend.h"
#include "qapi/error.h"
#include "qapi/qmp/qdict.h"
#include "block/replication.h"
typedef enum {
BLOCK_REPLICATION_NONE, /* block replication is not started */
BLOCK_REPLICATION_RUNNING, /* block replication is running */
BLOCK_REPLICATION_FAILOVER, /* failover is running in background */
BLOCK_REPLICATION_FAILOVER_FAILED, /* failover failed */
BLOCK_REPLICATION_DONE, /* block replication is done */
} ReplicationStage;
typedef struct BDRVReplicationState {
ReplicationMode mode;
ReplicationStage stage;
BlockJob *commit_job;
BdrvChild *hidden_disk;
BdrvChild *secondary_disk;
BlockJob *backup_job;
char *top_id;
ReplicationState *rs;
Error *blocker;
bool orig_hidden_read_only;
bool orig_secondary_read_only;
int error;
} BDRVReplicationState;
static void replication_start(ReplicationState *rs, ReplicationMode mode,
Error **errp);
static void replication_do_checkpoint(ReplicationState *rs, Error **errp);
static void replication_get_error(ReplicationState *rs, Error **errp);
static void replication_stop(ReplicationState *rs, bool failover,
Error **errp);
#define REPLICATION_MODE "mode"
#define REPLICATION_TOP_ID "top-id"
static QemuOptsList replication_runtime_opts = {
.name = "replication",
.head = QTAILQ_HEAD_INITIALIZER(replication_runtime_opts.head),
.desc = {
{
.name = REPLICATION_MODE,
.type = QEMU_OPT_STRING,
},
{
.name = REPLICATION_TOP_ID,
.type = QEMU_OPT_STRING,
},
{ /* end of list */ }
},
};
static ReplicationOps replication_ops = {
.start = replication_start,
.checkpoint = replication_do_checkpoint,
.get_error = replication_get_error,
.stop = replication_stop,
};
static int replication_open(BlockDriverState *bs, QDict *options,
int flags, Error **errp)
{
int ret;
BDRVReplicationState *s = bs->opaque;
QemuOpts *opts = NULL;
const char *mode;
const char *top_id;
ret = bdrv_open_file_child(NULL, options, "file", bs, errp);
if (ret < 0) {
return ret;
}
ret = -EINVAL;
opts = qemu_opts_create(&replication_runtime_opts, NULL, 0, &error_abort);
if (!qemu_opts_absorb_qdict(opts, options, errp)) {
goto fail;
}
mode = qemu_opt_get(opts, REPLICATION_MODE);
if (!mode) {
error_setg(errp, "Missing the option mode");
goto fail;
}
if (!strcmp(mode, "primary")) {
s->mode = REPLICATION_MODE_PRIMARY;
top_id = qemu_opt_get(opts, REPLICATION_TOP_ID);
if (top_id) {
error_setg(errp,
"The primary side does not support option top-id");
goto fail;
}
} else if (!strcmp(mode, "secondary")) {
s->mode = REPLICATION_MODE_SECONDARY;
top_id = qemu_opt_get(opts, REPLICATION_TOP_ID);
s->top_id = g_strdup(top_id);
if (!s->top_id) {
error_setg(errp, "Missing the option top-id");
goto fail;
}
} else {
error_setg(errp,
"The option mode's value should be primary or secondary");
goto fail;
}
s->rs = replication_new(bs, &replication_ops);
ret = 0;
fail:
qemu_opts_del(opts);
return ret;
}
static void replication_close(BlockDriverState *bs)
{
BDRVReplicationState *s = bs->opaque;
Job *commit_job;
GLOBAL_STATE_CODE();
if (s->stage == BLOCK_REPLICATION_RUNNING) {
replication_stop(s->rs, false, NULL);
}
if (s->stage == BLOCK_REPLICATION_FAILOVER) {
commit_job = &s->commit_job->job;
assert(commit_job->aio_context == qemu_get_current_aio_context());
job_cancel_sync(commit_job, false);
}
if (s->mode == REPLICATION_MODE_SECONDARY) {
g_free(s->top_id);
}
replication_remove(s->rs);
}
static void replication_child_perm(BlockDriverState *bs, BdrvChild *c,
BdrvChildRole role,
BlockReopenQueue *reopen_queue,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
if (role & BDRV_CHILD_PRIMARY) {
*nperm = BLK_PERM_CONSISTENT_READ;
} else {
*nperm = 0;
}
if ((bs->open_flags & (BDRV_O_INACTIVE | BDRV_O_RDWR)) == BDRV_O_RDWR) {
*nperm |= BLK_PERM_WRITE;
}
*nshared = BLK_PERM_CONSISTENT_READ
| BLK_PERM_WRITE
| BLK_PERM_WRITE_UNCHANGED;
return;
}
static int64_t coroutine_fn replication_co_getlength(BlockDriverState *bs)
{
return bdrv_co_getlength(bs->file->bs);
}
static int replication_get_io_status(BDRVReplicationState *s)
{
switch (s->stage) {
case BLOCK_REPLICATION_NONE:
return -EIO;
case BLOCK_REPLICATION_RUNNING:
return 0;
case BLOCK_REPLICATION_FAILOVER:
return s->mode == REPLICATION_MODE_PRIMARY ? -EIO : 0;
case BLOCK_REPLICATION_FAILOVER_FAILED:
return s->mode == REPLICATION_MODE_PRIMARY ? -EIO : 1;
case BLOCK_REPLICATION_DONE:
/*
* active commit job completes, and active disk and secondary_disk
* is swapped, so we can operate bs->file directly
*/
return s->mode == REPLICATION_MODE_PRIMARY ? -EIO : 0;
default:
abort();
}
}
static int replication_return_value(BDRVReplicationState *s, int ret)
{
if (s->mode == REPLICATION_MODE_SECONDARY) {
return ret;
}
if (ret < 0) {
s->error = ret;
ret = 0;
}
return ret;
}
static coroutine_fn int replication_co_readv(BlockDriverState *bs,
int64_t sector_num,
int remaining_sectors,
QEMUIOVector *qiov)
{
BDRVReplicationState *s = bs->opaque;
int ret;
if (s->mode == REPLICATION_MODE_PRIMARY) {
/* We only use it to forward primary write requests */
return -EIO;
}
ret = replication_get_io_status(s);
if (ret < 0) {
return ret;
}
ret = bdrv_co_preadv(bs->file, sector_num * BDRV_SECTOR_SIZE,
remaining_sectors * BDRV_SECTOR_SIZE, qiov, 0);
return replication_return_value(s, ret);
}
static coroutine_fn int replication_co_writev(BlockDriverState *bs,
int64_t sector_num,
int remaining_sectors,
QEMUIOVector *qiov,
int flags)
{
BDRVReplicationState *s = bs->opaque;
QEMUIOVector hd_qiov;
uint64_t bytes_done = 0;
BdrvChild *top = bs->file;
BdrvChild *base = s->secondary_disk;
BdrvChild *target;
int ret;
int64_t n;
ret = replication_get_io_status(s);
if (ret < 0) {
goto out;
}
if (ret == 0) {
ret = bdrv_co_pwritev(top, sector_num * BDRV_SECTOR_SIZE,
remaining_sectors * BDRV_SECTOR_SIZE, qiov, 0);
return replication_return_value(s, ret);
}
/*
* Failover failed, only write to active disk if the sectors
* have already been allocated in active disk/hidden disk.
*/
qemu_iovec_init(&hd_qiov, qiov->niov);
while (remaining_sectors > 0) {
int64_t count;
ret = bdrv_is_allocated_above(top->bs, base->bs, false,
sector_num * BDRV_SECTOR_SIZE,
remaining_sectors * BDRV_SECTOR_SIZE,
&count);
if (ret < 0) {
goto out1;
}
assert(QEMU_IS_ALIGNED(count, BDRV_SECTOR_SIZE));
n = count >> BDRV_SECTOR_BITS;
qemu_iovec_reset(&hd_qiov);
qemu_iovec_concat(&hd_qiov, qiov, bytes_done, count);
target = ret ? top : base;
ret = bdrv_co_pwritev(target, sector_num * BDRV_SECTOR_SIZE,
n * BDRV_SECTOR_SIZE, &hd_qiov, 0);
if (ret < 0) {
goto out1;
}
remaining_sectors -= n;
sector_num += n;
bytes_done += count;
}
out1:
qemu_iovec_destroy(&hd_qiov);
out:
return ret;
}
static void secondary_do_checkpoint(BlockDriverState *bs, Error **errp)
{
BDRVReplicationState *s = bs->opaque;
BdrvChild *active_disk = bs->file;
Error *local_err = NULL;
int ret;
if (!s->backup_job) {
error_setg(errp, "Backup job was cancelled unexpectedly");
return;
}
backup_do_checkpoint(s->backup_job, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
if (!active_disk->bs->drv) {
error_setg(errp, "Active disk %s is ejected",
active_disk->bs->node_name);
return;
}
ret = bdrv_make_empty(active_disk, errp);
if (ret < 0) {
return;
}
if (!s->hidden_disk->bs->drv) {
error_setg(errp, "Hidden disk %s is ejected",
s->hidden_disk->bs->node_name);
return;
}
ret = bdrv_make_empty(s->hidden_disk, errp);
if (ret < 0) {
return;
}
}
/* This function is supposed to be called twice:
* first with writable = true, then with writable = false.
* The first call puts s->hidden_disk and s->secondary_disk in
* r/w mode, and the second puts them back in their original state.
*/
static void reopen_backing_file(BlockDriverState *bs, bool writable,
Error **errp)
{
BDRVReplicationState *s = bs->opaque;
BdrvChild *hidden_disk, *secondary_disk;
BlockReopenQueue *reopen_queue = NULL;
/*
* s->hidden_disk and s->secondary_disk may not be set yet, as they will
* only be set after the children are writable.
*/
hidden_disk = bs->file->bs->backing;
secondary_disk = hidden_disk->bs->backing;
if (writable) {
s->orig_hidden_read_only = bdrv_is_read_only(hidden_disk->bs);
s->orig_secondary_read_only = bdrv_is_read_only(secondary_disk->bs);
}
if (s->orig_hidden_read_only) {
QDict *opts = qdict_new();
qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !writable);
reopen_queue = bdrv_reopen_queue(reopen_queue, hidden_disk->bs,
opts, true);
}
if (s->orig_secondary_read_only) {
QDict *opts = qdict_new();
qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !writable);
reopen_queue = bdrv_reopen_queue(reopen_queue, secondary_disk->bs,
opts, true);
}
if (reopen_queue) {
AioContext *ctx = bdrv_get_aio_context(bs);
if (ctx != qemu_get_aio_context()) {
aio_context_release(ctx);
}
bdrv_reopen_multiple(reopen_queue, errp);
if (ctx != qemu_get_aio_context()) {
aio_context_acquire(ctx);
}
}
}
static void backup_job_cleanup(BlockDriverState *bs)
{
BDRVReplicationState *s = bs->opaque;
BlockDriverState *top_bs;
s->backup_job = NULL;
top_bs = bdrv_lookup_bs(s->top_id, s->top_id, NULL);
if (!top_bs) {
return;
}
bdrv_op_unblock_all(top_bs, s->blocker);
error_free(s->blocker);
reopen_backing_file(bs, false, NULL);
}
static void backup_job_completed(void *opaque, int ret)
{
BlockDriverState *bs = opaque;
BDRVReplicationState *s = bs->opaque;
if (s->stage != BLOCK_REPLICATION_FAILOVER) {
/* The backup job is cancelled unexpectedly */
s->error = -EIO;
}
backup_job_cleanup(bs);
}
static bool check_top_bs(BlockDriverState *top_bs, BlockDriverState *bs)
{
BdrvChild *child;
/* The bs itself is the top_bs */
if (top_bs == bs) {
return true;
}
/* Iterate over top_bs's children */
QLIST_FOREACH(child, &top_bs->children, next) {
if (child->bs == bs || check_top_bs(child->bs, bs)) {
return true;
}
}
return false;
}
static void replication_start(ReplicationState *rs, ReplicationMode mode,
Error **errp)
{
BlockDriverState *bs = rs->opaque;
BDRVReplicationState *s;
BlockDriverState *top_bs;
BdrvChild *active_disk, *hidden_disk, *secondary_disk;
int64_t active_length, hidden_length, disk_length;
AioContext *aio_context;
Error *local_err = NULL;
BackupPerf perf = { .use_copy_range = true, .max_workers = 1 };
aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
s = bs->opaque;
if (s->stage == BLOCK_REPLICATION_DONE ||
s->stage == BLOCK_REPLICATION_FAILOVER) {
/*
* This case happens when a secondary is promoted to primary.
* Ignore the request because the secondary side of replication
* doesn't have to do anything anymore.
*/
aio_context_release(aio_context);
return;
}
if (s->stage != BLOCK_REPLICATION_NONE) {
error_setg(errp, "Block replication is running or done");
aio_context_release(aio_context);
return;
}
if (s->mode != mode) {
error_setg(errp, "The parameter mode's value is invalid, needs %d,"
" but got %d", s->mode, mode);
aio_context_release(aio_context);
return;
}
switch (s->mode) {
case REPLICATION_MODE_PRIMARY:
break;
case REPLICATION_MODE_SECONDARY:
active_disk = bs->file;
if (!active_disk || !active_disk->bs || !active_disk->bs->backing) {
error_setg(errp, "Active disk doesn't have backing file");
aio_context_release(aio_context);
return;
}
hidden_disk = active_disk->bs->backing;
if (!hidden_disk->bs || !hidden_disk->bs->backing) {
error_setg(errp, "Hidden disk doesn't have backing file");
aio_context_release(aio_context);
return;
}
secondary_disk = hidden_disk->bs->backing;
if (!secondary_disk->bs || !bdrv_has_blk(secondary_disk->bs)) {
error_setg(errp, "The secondary disk doesn't have block backend");
aio_context_release(aio_context);
return;
}
/* verify the length */
active_length = bdrv_getlength(active_disk->bs);
hidden_length = bdrv_getlength(hidden_disk->bs);
disk_length = bdrv_getlength(secondary_disk->bs);
if (active_length < 0 || hidden_length < 0 || disk_length < 0 ||
active_length != hidden_length || hidden_length != disk_length) {
error_setg(errp, "Active disk, hidden disk, secondary disk's length"
" are not the same");
aio_context_release(aio_context);
return;
}
/* Must be true, or the bdrv_getlength() calls would have failed */
assert(active_disk->bs->drv && hidden_disk->bs->drv);
if (!active_disk->bs->drv->bdrv_make_empty ||
!hidden_disk->bs->drv->bdrv_make_empty) {
error_setg(errp,
"Active disk or hidden disk doesn't support make_empty");
aio_context_release(aio_context);
return;
}
/* reopen the backing file in r/w mode */
reopen_backing_file(bs, true, &local_err);
if (local_err) {
error_propagate(errp, local_err);
aio_context_release(aio_context);
return;
}
bdrv_ref(hidden_disk->bs);
s->hidden_disk = bdrv_attach_child(bs, hidden_disk->bs, "hidden disk",
&child_of_bds, BDRV_CHILD_DATA,
&local_err);
if (local_err) {
error_propagate(errp, local_err);
aio_context_release(aio_context);
return;
}
bdrv_ref(secondary_disk->bs);
s->secondary_disk = bdrv_attach_child(bs, secondary_disk->bs,
"secondary disk", &child_of_bds,
BDRV_CHILD_DATA, &local_err);
if (local_err) {
error_propagate(errp, local_err);
aio_context_release(aio_context);
return;
}
/* start backup job now */
error_setg(&s->blocker,
"Block device is in use by internal backup job");
top_bs = bdrv_lookup_bs(s->top_id, s->top_id, NULL);
if (!top_bs || !bdrv_is_root_node(top_bs) ||
!check_top_bs(top_bs, bs)) {
error_setg(errp, "No top_bs or it is invalid");
reopen_backing_file(bs, false, NULL);
aio_context_release(aio_context);
return;
}
bdrv_op_block_all(top_bs, s->blocker);
bdrv_op_unblock(top_bs, BLOCK_OP_TYPE_DATAPLANE, s->blocker);
s->backup_job = backup_job_create(
NULL, s->secondary_disk->bs, s->hidden_disk->bs,
0, MIRROR_SYNC_MODE_NONE, NULL, 0, false, NULL,
&perf,
BLOCKDEV_ON_ERROR_REPORT,
BLOCKDEV_ON_ERROR_REPORT, JOB_INTERNAL,
backup_job_completed, bs, NULL, &local_err);
if (local_err) {
error_propagate(errp, local_err);
backup_job_cleanup(bs);
aio_context_release(aio_context);
return;
}
job_start(&s->backup_job->job);
break;
default:
aio_context_release(aio_context);
abort();
}
s->stage = BLOCK_REPLICATION_RUNNING;
if (s->mode == REPLICATION_MODE_SECONDARY) {
secondary_do_checkpoint(bs, errp);
}
s->error = 0;
aio_context_release(aio_context);
}
static void replication_do_checkpoint(ReplicationState *rs, Error **errp)
{
BlockDriverState *bs = rs->opaque;
BDRVReplicationState *s;
AioContext *aio_context;
aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
s = bs->opaque;
if (s->stage == BLOCK_REPLICATION_DONE ||
s->stage == BLOCK_REPLICATION_FAILOVER) {
/*
* This case happens when a secondary was promoted to primary.
* Ignore the request because the secondary side of replication
* doesn't have to do anything anymore.
*/
aio_context_release(aio_context);
return;
}
if (s->mode == REPLICATION_MODE_SECONDARY) {
secondary_do_checkpoint(bs, errp);
}
aio_context_release(aio_context);
}
static void replication_get_error(ReplicationState *rs, Error **errp)
{
BlockDriverState *bs = rs->opaque;
BDRVReplicationState *s;
AioContext *aio_context;
aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
s = bs->opaque;
if (s->stage == BLOCK_REPLICATION_NONE) {
error_setg(errp, "Block replication is not running");
aio_context_release(aio_context);
return;
}
if (s->error) {
error_setg(errp, "I/O error occurred");
aio_context_release(aio_context);
return;
}
aio_context_release(aio_context);
}
static void replication_done(void *opaque, int ret)
{
BlockDriverState *bs = opaque;
BDRVReplicationState *s = bs->opaque;
if (ret == 0) {
s->stage = BLOCK_REPLICATION_DONE;
bdrv_unref_child(bs, s->secondary_disk);
s->secondary_disk = NULL;
bdrv_unref_child(bs, s->hidden_disk);
s->hidden_disk = NULL;
s->error = 0;
} else {
s->stage = BLOCK_REPLICATION_FAILOVER_FAILED;
s->error = -EIO;
}
}
static void replication_stop(ReplicationState *rs, bool failover, Error **errp)
{
BlockDriverState *bs = rs->opaque;
BDRVReplicationState *s;
AioContext *aio_context;
aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
s = bs->opaque;
if (s->stage == BLOCK_REPLICATION_DONE ||
s->stage == BLOCK_REPLICATION_FAILOVER) {
/*
* This case happens when a secondary was promoted to primary.
* Ignore the request because the secondary side of replication
* doesn't have to do anything anymore.
*/
aio_context_release(aio_context);
return;
}
if (s->stage != BLOCK_REPLICATION_RUNNING) {
error_setg(errp, "Block replication is not running");
aio_context_release(aio_context);
return;
}
switch (s->mode) {
case REPLICATION_MODE_PRIMARY:
s->stage = BLOCK_REPLICATION_DONE;
s->error = 0;
break;
case REPLICATION_MODE_SECONDARY:
/*
* This BDS will be closed, and the job should be completed
* before the BDS is closed, because we will access hidden
* disk, secondary disk in backup_job_completed().
*/
if (s->backup_job) {
aio_context_release(aio_context);
job_cancel_sync(&s->backup_job->job, true);
aio_context_acquire(aio_context);
}
if (!failover) {
secondary_do_checkpoint(bs, errp);
s->stage = BLOCK_REPLICATION_DONE;
aio_context_release(aio_context);
return;
}
s->stage = BLOCK_REPLICATION_FAILOVER;
s->commit_job = commit_active_start(
NULL, bs->file->bs, s->secondary_disk->bs,
JOB_INTERNAL, 0, BLOCKDEV_ON_ERROR_REPORT,
NULL, replication_done, bs, true, errp);
break;
default:
aio_context_release(aio_context);
abort();
}
aio_context_release(aio_context);
}
static const char *const replication_strong_runtime_opts[] = {
REPLICATION_MODE,
REPLICATION_TOP_ID,
NULL
};
static BlockDriver bdrv_replication = {
.format_name = "replication",
.instance_size = sizeof(BDRVReplicationState),
.bdrv_open = replication_open,
.bdrv_close = replication_close,
.bdrv_child_perm = replication_child_perm,
.bdrv_co_getlength = replication_co_getlength,
.bdrv_co_readv = replication_co_readv,
.bdrv_co_writev = replication_co_writev,
.is_filter = true,
.has_variable_length = true,
.strong_runtime_opts = replication_strong_runtime_opts,
};
static void bdrv_replication_init(void)
{
bdrv_register(&bdrv_replication);
}
block_init(bdrv_replication_init);
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