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migration: introduce a QIOChannel impl for BlockDriverState VMState
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Introduce a QIOChannelBlock class that exposes the BlockDriverState
VMState region for I/O.

This is kept in the migration/ directory rather than io/, to avoid
a mutual dependancy between block/ <-> io/ directories. Also the
VMState should only be used by the migration code.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
  dgilbert: Fixed coding style in qio_channel_block_close
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berrange authored and dagrh committed Jun 22, 2022
1 parent bc698c3 commit 65cf200
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195 changes: 195 additions & 0 deletions migration/channel-block.c
@@ -0,0 +1,195 @@
/*
* QEMU I/O channels block driver
*
* Copyright (c) 2022 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
*/

#include "qemu/osdep.h"
#include "migration/channel-block.h"
#include "qapi/error.h"
#include "block/block.h"
#include "trace.h"

QIOChannelBlock *
qio_channel_block_new(BlockDriverState *bs)
{
QIOChannelBlock *ioc;

ioc = QIO_CHANNEL_BLOCK(object_new(TYPE_QIO_CHANNEL_BLOCK));

bdrv_ref(bs);
ioc->bs = bs;

return ioc;
}


static void
qio_channel_block_finalize(Object *obj)
{
QIOChannelBlock *ioc = QIO_CHANNEL_BLOCK(obj);

g_clear_pointer(&ioc->bs, bdrv_unref);
}


static ssize_t
qio_channel_block_readv(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
int **fds,
size_t *nfds,
Error **errp)
{
QIOChannelBlock *bioc = QIO_CHANNEL_BLOCK(ioc);
QEMUIOVector qiov;
int ret;

qemu_iovec_init_external(&qiov, (struct iovec *)iov, niov);
ret = bdrv_readv_vmstate(bioc->bs, &qiov, bioc->offset);
if (ret < 0) {
return ret;
}

bioc->offset += qiov.size;
return qiov.size;
}


static ssize_t
qio_channel_block_writev(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
int *fds,
size_t nfds,
int flags,
Error **errp)
{
QIOChannelBlock *bioc = QIO_CHANNEL_BLOCK(ioc);
QEMUIOVector qiov;
int ret;

qemu_iovec_init_external(&qiov, (struct iovec *)iov, niov);
ret = bdrv_writev_vmstate(bioc->bs, &qiov, bioc->offset);
if (ret < 0) {
return ret;
}

bioc->offset += qiov.size;
return qiov.size;
}


static int
qio_channel_block_set_blocking(QIOChannel *ioc,
bool enabled,
Error **errp)
{
if (!enabled) {
error_setg(errp, "Non-blocking mode not supported for block devices");
return -1;
}
return 0;
}


static off_t
qio_channel_block_seek(QIOChannel *ioc,
off_t offset,
int whence,
Error **errp)
{
QIOChannelBlock *bioc = QIO_CHANNEL_BLOCK(ioc);

switch (whence) {
case SEEK_SET:
bioc->offset = offset;
break;
case SEEK_CUR:
bioc->offset += whence;
break;
case SEEK_END:
error_setg(errp, "Size of VMstate region is unknown");
return (off_t)-1;
default:
g_assert_not_reached();
}

return bioc->offset;
}


static int
qio_channel_block_close(QIOChannel *ioc,
Error **errp)
{
QIOChannelBlock *bioc = QIO_CHANNEL_BLOCK(ioc);
int rv = bdrv_flush(bioc->bs);

if (rv < 0) {
error_setg_errno(errp, -rv,
"Unable to flush VMState");
return -1;
}

g_clear_pointer(&bioc->bs, bdrv_unref);
bioc->offset = 0;

return 0;
}


static void
qio_channel_block_set_aio_fd_handler(QIOChannel *ioc,
AioContext *ctx,
IOHandler *io_read,
IOHandler *io_write,
void *opaque)
{
/* XXX anything we can do here ? */
}


static void
qio_channel_block_class_init(ObjectClass *klass,
void *class_data G_GNUC_UNUSED)
{
QIOChannelClass *ioc_klass = QIO_CHANNEL_CLASS(klass);

ioc_klass->io_writev = qio_channel_block_writev;
ioc_klass->io_readv = qio_channel_block_readv;
ioc_klass->io_set_blocking = qio_channel_block_set_blocking;
ioc_klass->io_seek = qio_channel_block_seek;
ioc_klass->io_close = qio_channel_block_close;
ioc_klass->io_set_aio_fd_handler = qio_channel_block_set_aio_fd_handler;
}

static const TypeInfo qio_channel_block_info = {
.parent = TYPE_QIO_CHANNEL,
.name = TYPE_QIO_CHANNEL_BLOCK,
.instance_size = sizeof(QIOChannelBlock),
.instance_finalize = qio_channel_block_finalize,
.class_init = qio_channel_block_class_init,
};

static void
qio_channel_block_register_types(void)
{
type_register_static(&qio_channel_block_info);
}

type_init(qio_channel_block_register_types);
59 changes: 59 additions & 0 deletions migration/channel-block.h
@@ -0,0 +1,59 @@
/*
* QEMU I/O channels block driver
*
* Copyright (c) 2022 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
*/

#ifndef QIO_CHANNEL_BLOCK_H
#define QIO_CHANNEL_BLOCK_H

#include "io/channel.h"
#include "qom/object.h"

#define TYPE_QIO_CHANNEL_BLOCK "qio-channel-block"
OBJECT_DECLARE_SIMPLE_TYPE(QIOChannelBlock, QIO_CHANNEL_BLOCK)


/**
* QIOChannelBlock:
*
* The QIOChannelBlock object provides a channel implementation
* that is able to perform I/O on the BlockDriverState objects
* to the VMState region.
*/

struct QIOChannelBlock {
QIOChannel parent;
BlockDriverState *bs;
off_t offset;
};


/**
* qio_channel_block_new:
* @bs: the block driver state
*
* Create a new IO channel object that can perform
* I/O on a BlockDriverState object to the VMState
* region
*
* Returns: the new channel object
*/
QIOChannelBlock *
qio_channel_block_new(BlockDriverState *bs);

#endif /* QIO_CHANNEL_BLOCK_H */
1 change: 1 addition & 0 deletions migration/meson.build
Expand Up @@ -13,6 +13,7 @@ softmmu_ss.add(migration_files)
softmmu_ss.add(files(
'block-dirty-bitmap.c',
'channel.c',
'channel-block.c',
'colo-failover.c',
'colo.c',
'exec.c',
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