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qemu/io/channel-file.c
Fabiano Rosas 61dec06082 migration/multifd: Don't fsync when closing QIOChannelFile 
Commit bc38feddeb ("io: fsync before closing a file channel") added a
fsync/fdatasync at the closing point of the QIOChannelFile to ensure
integrity of the migration stream in case of QEMU crash.

The decision to do the sync at qio_channel_close() was not the best
since that function runs in the main thread and the fsync can cause
QEMU to hang for several minutes, depending on the migration size and
disk speed.

To fix the hang, remove the fsync from qio_channel_file_close().

At this moment, the migration code is the only user of the fsync and
we're taking the tradeoff of not having a sync at all, leaving the
responsibility to the upper layers.

Fixes: bc38feddeb ("io: fsync before closing a file channel")
Reviewed-by: "Daniel P. Berrangé" <berrange@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240305195629.9922-1-farosas@suse.de
Link: https://lore.kernel.org/r/20240305174332.2553-1-farosas@suse.de
[peterx: add more comment to the qio_channel_close()]
Signed-off-by: Peter Xu <peterx@redhat.com>
2024-03-11 14:41:40 -04:00

311 lines
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/*
* QEMU I/O channels files driver
*
* Copyright (c) 2015 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 "io/channel-file.h"
#include "io/channel-util.h"
#include "io/channel-watch.h"
#include "qapi/error.h"
#include "qemu/module.h"
#include "qemu/sockets.h"
#include "trace.h"
QIOChannelFile *
qio_channel_file_new_fd(int fd)
{
QIOChannelFile *ioc;
ioc = QIO_CHANNEL_FILE(object_new(TYPE_QIO_CHANNEL_FILE));
ioc->fd = fd;
if (lseek(fd, 0, SEEK_CUR) != (off_t)-1) {
qio_channel_set_feature(QIO_CHANNEL(ioc), QIO_CHANNEL_FEATURE_SEEKABLE);
}
trace_qio_channel_file_new_fd(ioc, fd);
return ioc;
}
QIOChannelFile *
qio_channel_file_new_path(const char *path,
int flags,
mode_t mode,
Error **errp)
{
QIOChannelFile *ioc;
ioc = QIO_CHANNEL_FILE(object_new(TYPE_QIO_CHANNEL_FILE));
ioc->fd = qemu_open_old(path, flags, mode);
if (ioc->fd < 0) {
object_unref(OBJECT(ioc));
error_setg_errno(errp, errno,
"Unable to open %s", path);
return NULL;
}
if (lseek(ioc->fd, 0, SEEK_CUR) != (off_t)-1) {
qio_channel_set_feature(QIO_CHANNEL(ioc), QIO_CHANNEL_FEATURE_SEEKABLE);
}
trace_qio_channel_file_new_path(ioc, path, flags, mode, ioc->fd);
return ioc;
}
static void qio_channel_file_init(Object *obj)
{
QIOChannelFile *ioc = QIO_CHANNEL_FILE(obj);
ioc->fd = -1;
}
static void qio_channel_file_finalize(Object *obj)
{
QIOChannelFile *ioc = QIO_CHANNEL_FILE(obj);
if (ioc->fd != -1) {
qemu_close(ioc->fd);
ioc->fd = -1;
}
}
static ssize_t qio_channel_file_readv(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
int **fds,
size_t *nfds,
int flags,
Error **errp)
{
QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
ssize_t ret;
retry:
ret = readv(fioc->fd, iov, niov);
if (ret < 0) {
if (errno == EAGAIN) {
return QIO_CHANNEL_ERR_BLOCK;
}
if (errno == EINTR) {
goto retry;
}
error_setg_errno(errp, errno,
"Unable to read from file");
return -1;
}
return ret;
}
static ssize_t qio_channel_file_writev(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
int *fds,
size_t nfds,
int flags,
Error **errp)
{
QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
ssize_t ret;
retry:
ret = writev(fioc->fd, iov, niov);
if (ret <= 0) {
if (errno == EAGAIN) {
return QIO_CHANNEL_ERR_BLOCK;
}
if (errno == EINTR) {
goto retry;
}
error_setg_errno(errp, errno,
"Unable to write to file");
return -1;
}
return ret;
}
#ifdef CONFIG_PREADV
static ssize_t qio_channel_file_preadv(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
off_t offset,
Error **errp)
{
QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
ssize_t ret;
retry:
ret = preadv(fioc->fd, iov, niov, offset);
if (ret < 0) {
if (errno == EAGAIN) {
return QIO_CHANNEL_ERR_BLOCK;
}
if (errno == EINTR) {
goto retry;
}
error_setg_errno(errp, errno, "Unable to read from file");
return -1;
}
return ret;
}
static ssize_t qio_channel_file_pwritev(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
off_t offset,
Error **errp)
{
QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
ssize_t ret;
retry:
ret = pwritev(fioc->fd, iov, niov, offset);
if (ret <= 0) {
if (errno == EAGAIN) {
return QIO_CHANNEL_ERR_BLOCK;
}
if (errno == EINTR) {
goto retry;
}
error_setg_errno(errp, errno, "Unable to write to file");
return -1;
}
return ret;
}
#endif /* CONFIG_PREADV */
static int qio_channel_file_set_blocking(QIOChannel *ioc,
bool enabled,
Error **errp)
{
#ifdef WIN32
/* not implemented */
error_setg_errno(errp, errno, "Failed to set FD nonblocking");
return -1;
#else
QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
if (!g_unix_set_fd_nonblocking(fioc->fd, !enabled, NULL)) {
error_setg_errno(errp, errno, "Failed to set FD nonblocking");
return -1;
}
return 0;
#endif
}
static off_t qio_channel_file_seek(QIOChannel *ioc,
off_t offset,
int whence,
Error **errp)
{
QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
off_t ret;
ret = lseek(fioc->fd, offset, whence);
if (ret == (off_t)-1) {
error_setg_errno(errp, errno,
"Unable to seek to offset %lld whence %d in file",
(long long int)offset, whence);
return -1;
}
return ret;
}
static int qio_channel_file_close(QIOChannel *ioc,
Error **errp)
{
QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
if (qemu_close(fioc->fd) < 0) {
error_setg_errno(errp, errno,
"Unable to close file");
return -1;
}
fioc->fd = -1;
return 0;
}
static void qio_channel_file_set_aio_fd_handler(QIOChannel *ioc,
AioContext *read_ctx,
IOHandler *io_read,
AioContext *write_ctx,
IOHandler *io_write,
void *opaque)
{
QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
qio_channel_util_set_aio_fd_handler(fioc->fd, read_ctx, io_read,
fioc->fd, write_ctx, io_write,
opaque);
}
static GSource *qio_channel_file_create_watch(QIOChannel *ioc,
GIOCondition condition)
{
QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc);
return qio_channel_create_fd_watch(ioc,
fioc->fd,
condition);
}
static void qio_channel_file_class_init(ObjectClass *klass,
void *class_data G_GNUC_UNUSED)
{
QIOChannelClass *ioc_klass = QIO_CHANNEL_CLASS(klass);
ioc_klass->io_writev = qio_channel_file_writev;
ioc_klass->io_readv = qio_channel_file_readv;
ioc_klass->io_set_blocking = qio_channel_file_set_blocking;
#ifdef CONFIG_PREADV
ioc_klass->io_pwritev = qio_channel_file_pwritev;
ioc_klass->io_preadv = qio_channel_file_preadv;
#endif
ioc_klass->io_seek = qio_channel_file_seek;
ioc_klass->io_close = qio_channel_file_close;
ioc_klass->io_create_watch = qio_channel_file_create_watch;
ioc_klass->io_set_aio_fd_handler = qio_channel_file_set_aio_fd_handler;
}
static const TypeInfo qio_channel_file_info = {
.parent = TYPE_QIO_CHANNEL,
.name = TYPE_QIO_CHANNEL_FILE,
.instance_size = sizeof(QIOChannelFile),
.instance_init = qio_channel_file_init,
.instance_finalize = qio_channel_file_finalize,
.class_init = qio_channel_file_class_init,
};
static void qio_channel_file_register_types(void)
{
type_register_static(&qio_channel_file_info);
}
type_init(qio_channel_file_register_types);
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