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Message-ID: <Y0/fbSL0QDlTU6Yv@bfoster>
Date: Wed, 19 Oct 2022 07:28:45 -0400
From: Brian Foster <bfoster@...hat.com>
To: Ivan Babrou <ivan@...udflare.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
kernel-team@...udflare.com, Alexey Dobriyan <adobriyan@...il.com>,
Al Viro <viro@...iv.linux.org.uk>,
Theodore Ts'o <tytso@....edu>,
David Laight <David.Laight@...lab.com>,
Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>,
David Hildenbrand <david@...hat.com>,
Johannes Weiner <hannes@...xchg.org>,
Christoph Anton Mitterer <mail@...istoph.anton.mitterer.name>,
Mike Rapoport <rppt@...nel.org>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Kalesh Singh <kaleshsingh@...gle.com>
Subject: Re: [PATCH v3] proc: report open files as size in stat() for
/proc/pid/fd
On Tue, Oct 18, 2022 at 11:51:02AM -0700, Ivan Babrou wrote:
> On Tue, Oct 18, 2022 at 11:16 AM Brian Foster <bfoster@...hat.com> wrote:
> > > +static int proc_readfd_count(struct inode *inode)
> > > +{
> > > + struct task_struct *p = get_proc_task(inode);
> > > + struct fdtable *fdt;
> > > + unsigned int open_fds = 0;
> > > +
> > > + if (!p)
> > > + return -ENOENT;
> >
> > Maybe this shouldn't happen, but do you mean to assign the error code to
> > stat->size in the caller? Otherwise this seems reasonable to me.
>
> You are right. As unlikely as it is to happen, we shouldn't return
> negative size.
>
> What's the idiomatic way to make this work? My two options are:
>
> 1. Pass &stat->size into proc_readfd_count:
>
> if (S_ISDIR(inode->i_mode)) {
> rv = proc_readfd_count(inode, &stat->size);
> if (rv < 0)
> goto out;
> }
>
> out:
> return rv;
>
> OR without a goto:
>
> if (S_ISDIR(inode->i_mode)) {
> rv = proc_readfd_count(inode, &stat->size));
> if (rv < 0)
> return rv;
> }
>
> return rv;
>
> 2. Return negative count as error (as we don't expect negative amount
> of files open):
>
> if (S_ISDIR(inode->i_mode)) {
> size = proc_readfd_count(inode);
> if (size < 0)
> return size;
> stat->size = size;
> }
>
I suppose the latter is less of a change to the original patch..? Either
way seems reasonable to me. I have no strong preference FWIW.
Brian
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