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Date:   Fri, 26 Jun 2020 15:36:33 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     Christoph Hellwig <hch@lst.de>, Al Viro <viro@zeniv.linux.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>,
        Kees Cook <keescook@chromium.org>,
        Iurii Zaikin <yzaikin@google.com>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 2/9] proc: add a read_iter method to proc proc_ops
Message-ID: <20200626133633.GA12646@lst.de>
References: <20200626075836.1998185-1-hch@lst.de> <20200626075836.1998185-3-hch@lst.de> <20200626120624.GL4332@42.do-not-panic.com>
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On Fri, Jun 26, 2020 at 12:06:24PM +0000, Luis Chamberlain wrote:
> On Fri, Jun 26, 2020 at 09:58:29AM +0200, Christoph Hellwig wrote:
> > diff --git a/fs/proc/inode.c b/fs/proc/inode.c
> > index 28d6105e908e4c..fa86619cebc2be 100644
> > --- a/fs/proc/inode.c
> > +++ b/fs/proc/inode.c
> > @@ -297,6 +297,29 @@ static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
> >  	return rv;
> >  }
> >  
> > +static ssize_t pde_read_iter(struct proc_dir_entry *pde, struct kiocb *iocb,
> > +		struct iov_iter *iter)
> > +{
> > +	if (!pde->proc_ops->proc_read_iter)
> > +		return -EINVAL;
> 
> When is this true?

Whenever a user sets up the method..