Re: [kvm-devel] [PATCH/RFC 1/2] anon-inodes: Remove fd_install() from anon_inode_getfd()

Avi Kivity
2008-03-05T09:36:37Z

Davide Libenzi wrote:
>> I think that may be a bit cleaner than Al's approach, but it still
>> leaves the same trap that create_vcpu_fd() falls into. The current
>> code is:
>>
>> static int create_vcpu_fd(struct kvm_vcpu *vcpu)
>> {
>> int fd, r;
>> struct inode *inode;
>> struct file *file;
>>
>> r = anon_inode_getfd(&fd, &inode, &file,
>> "kvm-vcpu", &kvm_vcpu_fops, vcpu);
>> if (r)
>> return r;
>> atomic_inc(&vcpu->kvm->filp->f_count);
>> return fd;
>> }
>>
>> and with your proposal, the natural way to write that becomes:
>>
>> static int create_vcpu_fd(struct kvm_vcpu *vcpu)
>> {
>> int fd, r;
>>
>> r = anon_inode_getfd(&fd, NULL,
>> "kvm-vcpu", &kvm_vcpu_fops, vcpu);
>> if (r)
>> return r;
>> atomic_inc(&vcpu->kvm->filp->f_count);
>> return fd;
>> }
>>
>
> I don't know KVM code, but can't the "private_data" setup be completed
> before calling anon_inode_getfd()?
>

Creating the fd is the last thing done when creating a vcpu.

> Or ...
>
> static int create_vcpu_fd(struct kvm_vcpu *vcpu)
> {
> int fd, r;
>
> get_file(vcpu->kvm->filp);
> r = anon_inode_getfd(&fd, NULL,
> "kvm-vcpu", &kvm_vcpu_fops, vcpu);
> if (r) {
> fput(vcpu->kvm->filp);
> return r;
> }
> return fd;
> }
>

This seems reasonable.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.