linux-kernel - Re: [PATCH 6/9] swap_info: swap

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Date:	Thu, 15 Oct 2009 23:17:20 +0100 (BST)
From:	Hugh Dickins <hugh.dickins@...cali.co.uk>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 6/9] swap_info: swap_map of chars not shorts

On Thu, 15 Oct 2009, KAMEZAWA Hiroyuki wrote:
> On Thu, 15 Oct 2009 01:53:52 +0100 (BST)
> Hugh Dickins <hugh.dickins@...cali.co.uk> wrote:
> > @@ -1175,6 +1175,12 @@ static int try_to_unuse(unsigned int typ
> >  		 * If that's wrong, then we should worry more about
> >  		 * exit_mmap() and do_munmap() cases described above:
> >  		 * we might be resetting SWAP_MAP_MAX too early here.
> > +		 *
> > +		 * Yes, that's wrong: though very unlikely, swap count 0x7ffe
> > +		 * could surely occur if pid_max raised from PID_MAX_DEFAULT;
> 
> Just a nitpick.
> 
> Hmm, logically, our MAX COUNT is 0x7e after this patch. Then, how about not
> mentioning to 0x7ffe and PID_MAX ? as..
> 
> Yes, that's wrong: we now use SWAP_MAP_MAX as 0x7e, very easy to overflow.
> next patch will...

Perhaps we're reading it differently: I was there inserting a comment
on what was already said above (with no wish to change that existing
comment), then going on (immediately below) to mention how this patch
is now lowering SWAP_MAP_MAX to 0x7e, making the situation even worse,
but no worries because the next patch fixes it.

If you are seeing a nit there, I'm afraid it's one too small for my
eye!  And the lifetime of this comment, in Linus's git history, will
be (I'm guessing) a fraction of a second - becoming a non-issue, it
rightly gets deleted in the next patch.

Hugh

> 
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> > +		 * and we are now lowering SWAP_MAP_MAX to 0x7e, making it
> > +		 * much easier to reach.  But the next patch will fix that.
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