linux-kernel - Re: max_user_watches overflows on 16TB system.

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Date:	Sat, 2 Oct 2010 07:04:51 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
cc:	Robin Holt <holt@....com>, Pekka Enberg <penberg@...helsinki.fi>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: max_user_watches overflows on 16TB system.

On Fri, 1 Oct 2010, Eric W. Biederman wrote:

> Davide Libenzi <davidel@...ilserver.org> writes:
> 
> > On Fri, 1 Oct 2010, Robin Holt wrote:
> >
> >> 
> >> Following a boot of a 16TB system, we noticed that the max_user_watches
> >> sysctl was negative.  Is there any downside to converting that to a
> >> static long and handling the fallout from the change?  I believe that
> >> fallout includes changing the definition of epoll_watches over to an
> >> atomic_long_t as well.
> >> 
> >> Alternatively should we just limit max_user_watches to INT_MAX?
> >
> > 2B watches looks an acceptable limit to me, at least for now.
> > Nobody complained about not having enough of them so far.
> 
> Which suggests that we need to force the boot time calculation to not
> exceed 2B.
> 
> From the sysctl interface perspective now that all of it is exported as
> ascii strings I don't see a problem there.

Thinking with actual code at hands, you're right.  It just makes more 
sense the 'long' variable conversion, even though MAX_INT watches are a 
huge number today.
Robin, sorry for the confusion.  Can you post the 'long' conversion patch?


- Davide


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