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To:     Matthew Wilcox <willy@infradead.org>
cc:     Nate Karstens <nate.karstens@garmin.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jeff Layton <jlayton@kernel.org>,
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        Matt Turner <mattst88@gmail.com>,
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        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
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        David Laight <David.Laight@aculab.com>,
        linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org,
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        linux-kernel@vger.kernel.org, Changli Gao <xiaosuo@gmail.com>
Subject: Re: [PATCH v2] Implement close-on-fork
From:   Ralph Corderoy <ralph@inputplus.co.uk>
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Date:   Sun, 19 Jun 2022 11:42:28 +0100
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Hi Matthew, thanks for replying.

> > The need for O_CLOFORK might be made more clear by looking at a
> > long-standing Go issue, i.e. unrelated to system(3), which was started
> > in 2017 by Russ Cox when he summed up the current race-condition
> > behaviour of trying to execve(2) a newly created file:
> > https://github.com/golang/go/issues/22315.
>
> The problem is that people advocating for O_CLOFORK understand its
> value, but not its cost.  Other google employees have a system which
> has literally millions of file descriptors in a single process.
> Having to maintain this extra state per-fd is a cost they don't want
> to pay (and have been quite vocal about earlier in this thread).

So do you agree the userspace issue is best solved by *_CLOFORK and the
problem is how to implement *_CLOFORK at an acceptable cost?

OTOH David Laight was making suggestions on moving the load to the
fork/exec path earlier in the thread, but OTOH Al Viro mentioned a
‘portable solution’, though that could have been to a specific issue
rather than the more general case.

How would you recommend approaching an acceptable cost is progressed?
Iterate on patch versions?  Open a bugzilla.kernel.org for central
tracking and linking from the other projects?  ..?

-- 
Cheers, Ralph.