Re: [GIT PULL] vfs pidfd

From: Linus Torvalds <torvalds@linux-foundation.org>
To: Christian Brauner <brauner@kernel.org>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [GIT PULL] vfs pidfd
Date: Tue, 12 Mar 2024 09:23:55 -0700	[thread overview]
Message-ID: <CAHk-=wgsjaakq1FFOXEKAdZKrkTgGafW9BedmWMP2NNka4bU-w@mail.gmail.com> (raw)
In-Reply-To: <20240312-dingo-sehnlich-b3ecc35c6de7@brauner>

On Tue, 12 Mar 2024 at 07:16, Christian Brauner <brauner@kernel.org> wrote:
>
> No, the size of struct pid was the main reason but I don't think it
> matters. A side-effect was that we could easily enforce 64bit inode
> numbers. But realistically it's trivial enough to workaround. Here's a
> patch for what I think is pretty simple appended. Does that work?

This looks eminently sane to me. Not that I actually _tested_it, but
since my testing would have compared it to my current setup (64-bit
and CONFIG_FS_PID=y) any testing would have been pointless because
that case didn't change.

Looking at the patch, I do wonder how much we even care about 64-bit
inodes. I'd like to point out how 'path_from_stashed()' only takes a
'unsigned long ino' anyway, and I don't think anything really cares
about either the high bits *or* the uniqueness of that inode number..

And similarly, i_ino isn't actually *used* for anything but naming to
user space.

So I'm not at all sure the whole 64-bit checks are worth it. Am I
missing something else?

                Linus