[Qemu-devel] Re: [PATCH 1/2] Add virtagent file system freeze/thaw

[Adam Litke <agl@us.ibm.com>]

On Tue, 2011-02-01 at 11:58 +0100, Jes.Sorensen@redhat.com wrote:
> +/*
> + * va_fsfreeze(): Walk list of mounted file systems in the guest, and
> + *   freeze the ones which are real local file systems.
> + * rpc return values: Number of file systems frozen, -1 on error.
> + */
> +static xmlrpc_value *va_fsfreeze(xmlrpc_env *env,
> +                                 xmlrpc_value *params,
> +                                 void *user_data)
> +{
> +    xmlrpc_int32 ret = 0, i = 0;
> +    xmlrpc_value *result;
> +    struct direntry *entry;
> +    int fd;
> +    SLOG("va_fsfreeze()");
> +
> +    if (fsfreeze_status == FREEZE_FROZEN) {
> +        ret = 0;
> +        goto out;
> +    }
> +
> +    ret = build_mount_list();
> +    if (ret < 0) {
> +        goto out;
> +    }
> +
> +    fsfreeze_status = FREEZE_INPROGRESS;
> +
> +    entry = mount_list;
> +    while(entry) {
> +        fd = qemu_open(entry->dirname, O_RDONLY);
> +        if (fd == -1) {
> +            ret = errno;
> +            goto error;
> +        }
> +        ret = ioctl(fd, FIFREEZE);
> +        if (ret < 0 && ret != EOPNOTSUPP) {
> +            goto error;
> +        }

Here we silently ignore filesystems that do not support the FIFREEZE
ioctl.  Do we need to have a more complex return value so that we can
communicate which mount points could not be frozen?  Otherwise, an
unsuspecting host could retrieve a corrupted snapshot of that
filesystem, right?

> +
> +        close(fd);
> +        entry = entry->next;
> +        i++;
> +    }
> +
> +    fsfreeze_status = FREEZE_FROZEN;
> +    ret = i;
> +out:
> +    result = xmlrpc_build_value(env, "i", ret);
> +    return result;
> +error:
> +    if (i > 0) {
> +        fsfreeze_status = FREEZE_ERROR;
> +    }
> +    goto out;
> +}

-- 
Thanks,
Adam