Re: [PATCH 2/2] pidfd: add pidfdfs

[Oleg Nesterov <oleg@redhat.com>]

On 02/16, Christian Brauner wrote:
>
> +struct file *pidfdfs_alloc_file(struct pid *pid, unsigned int flags)
> +{
> +
> +	struct inode *inode;
> +	struct file *pidfd_file;
> +
> +	inode = iget_locked(pidfdfs_sb, pid->ino);
> +	if (!inode)
> +		return ERR_PTR(-ENOMEM);
> +
> +	if (inode->i_state & I_NEW) {
> +		inode->i_ino = pid->ino;

I guess this is unnecessary, iget_locked() should initialize i_ino if I_NEW ?

But I have a really stupid (I know nothing about vfs) question, why do we
need pidfdfs_ino and pid->ino ? Can you explain why pidfdfs_alloc_file()
can't simply use, say, iget_locked(pidfdfs_sb, (unsigned long)pid) ?

IIUC, if this pid is freed and then another "struct pid" has the same address
we can rely on __wait_on_freeing_inode() ?

Oleg.