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permissions: 0.993
debug: 0.991
semantic: 0.990
device: 0.989
other: 0.987
performance: 0.985
graphic: 0.982
PID: 0.981
files: 0.974
socket: 0.971
boot: 0.969
network: 0.968
vnc: 0.964
KVM: 0.943
An IO error happen when qemu snapshot-create
My qemu version is 1.7.1,but when I try to make live snapshot by libvirt,the libvirt sometimes report an error :qemuMonitorJSONCheckError:377 : internal error: unable to execute QEMU command 'transaction': An IO error has occurred.
Here is the command being snpshot create by virsh:
virsh snapshot-create snapshot-test.vm snapshot.xml --no-metadata --disk-only --reuse-external
the snapshot.xml:
<domainsnapshot>
<description>test</description>
<disks>
<disk name='vda' snapshot="external">
<source dev='/home/disk/sbd8' file='/home/disk/sdb8' type="block"/>
</disk>
</disks>
</domainsnapshot>
I have read the qemu code about the snapshot create, and I find the qemu when call the function handle_aiocb_rw_linear():
static ssize_t handle_aiocb_rw_linear(RawPosixAIOData *aiocb, char *buf)
{
ssize_t offset = 0;
ssize_t len;
while (offset < aiocb->aio_nbytes) {
if (aiocb->aio_type & QEMU_AIO_WRITE) {
len = pwrite(aiocb->aio_fildes,
(const char *)buf + offset,
aiocb->aio_nbytes - offset,
aiocb->aio_offset + offset);
} else {
len = pread(aiocb->aio_fildes,
buf + offset,
aiocb->aio_nbytes - offset,
aiocb->aio_offset + offset);
}
if (len == -1 && errno == EINTR) {
continue;
} else if (len == -1) {
offset = -errno;
break;
} else if (len == 0) {
break;
}
offset += len;
}
return offset;
}
The function pwrite happen error,the errono is 1,and the error describe:"pwrite failed, Operation not permitted (1, EPERM) because the process does not have the appropriate privileges to use the pwrite system call".
The qemu call stack about is:
external_snapshot_prepare()->bdrv_flush()->...->paio_submit->...->handle_aiocb_rw_linear.
Please ask the libvirt community for help. This issue is probably related to your libvirt storage setup.
On Tue, Oct 13, 2015 at 11:52:26AM -0000, jiangchi68 wrote:
> My qemu version is 1.7.1,but when I try to make live snapshot by
> libvirt,the libvirt sometimes report an error
> :qemuMonitorJSONCheckError:377 : internal error: unable to execute QEMU
> command 'transaction': An IO error has occurred.
>
> Here is the command being snpshot create by virsh:
> virsh snapshot-create snapshot-test.vm snapshot.xml --no-metadata --disk-only --reuse-external
> the snapshot.xml:
> <domainsnapshot>
> <description>test</description>
> <disks>
> <disk name='vda' snapshot="external">
> <source dev='/home/disk/sbd8' file='/home/disk/sdb8' type="block"/>
> </disk>
> </disks>
> </domainsnapshot>
Please send your question to <email address hidden>.
It could be related to /home/disk file permissions.
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