linux-kernel - Re: [rfc][patches] fix for munmap/truncate races

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Message-ID: <CA+55aFwBEoD167oD=X9d6jR+wn6Tb-QFgZR+wGwdej4qakCMgg@mail.gmail.com>
Date:	Sun, 18 Mar 2012 15:01:08 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [rfc][patches] fix for munmap/truncate races

On Sun, Mar 18, 2012 at 12:07 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> -       tlb_finish_mmu(&tlb, 0, end);
> +       tlb_finish_mmu(&tlb, 0, -1);

Hmm. The fact that you drop the end pointer means that some
architectures that optimize the TLB flushing for ranges now
effectively can't do it any more.

Now, I think it's only ia64 that really is affected, but it *might* matter.

In particular, ia64 has some logic for "if you only flush one single
region, you can optimize it", and the region sizes are in the
terabytes. And I'm pretty sure you broke that - I'm just not entirely
sure how much we care.

                 Linus
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