Re: [PATCH RFC 03/10] pidfs: move setting flags into pidfs_alloc_file()

[Christian Brauner <brauner@kernel.org>]

On Sun, Mar 02, 2025 at 02:09:36PM +0100, Oleg Nesterov wrote:
> On 02/28, Christian Brauner wrote:
> >
> > @@ -696,6 +696,10 @@ struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags)
> >  		return ERR_PTR(ret);
> >
> >  	pidfd_file = dentry_open(&path, flags, current_cred());
> > +	/* Raise PIDFD_THREAD explicitly as dentry_open() strips it. */
>                                             ^^^^^^^^^^^^^^^^^^^^^^^
> Hmm, does it?
> 
> dentry_open(flags) just passes "flags" to alloc_empty_file()->init_file(),
> and init_file(flags) does
> 
> 	f->f_flags      = flags;
> 
> so it seems that

dentry_open()
-> do_dentry_open()
   {
           f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
	           f->f_iocb_flags = iocb_flags(f);
   }

> 
> > @@ -2042,11 +2042,6 @@ static int __pidfd_prepare(struct pid *pid, unsigned int flags, struct file **re
> >  	if (IS_ERR(pidfd_file))
> >  		return PTR_ERR(pidfd_file);
> >
> > -	/*
> > -	 * anon_inode_getfile() ignores everything outside of the
> > -	 * O_ACCMODE | O_NONBLOCK mask, set PIDFD_THREAD manually.
> > -	 */
> > -	pidfd_file->f_flags |= (flags & PIDFD_THREAD);
> 
> we can just kill this outdated code?

Unfortunately not.