Messages in this thread | | | Date | Thu, 4 Oct 2007 17:53:46 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [BUG] kernel BUG at arch/i386/mm/highmem.c:15! on 2.6.23-rc8/rc9 |
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On Thu, 4 Oct 2007, Linus Torvalds wrote: > > Ouch.
Very much so.
> > The patch looks obviously correct, to the point that I don't understand > how this bug happened in the first place. It seems to have been > introduced by Nick in d0217ac04ca6591841e5665f518e38064f4e65bd ("mm: fault > feedback #1") if I read it right.
Yes, I think you are reading that right.
> > So "do_nonlinear_fault()" would effectively end up unmapping the PTE > twice, right? And if I understand the problem right, this wasn't noticed > immediately, because it probably only matters on: > > - CONFIG_HIGHPTE > *and* > - a filesystem that allows VM_NONLINEAR, which became very rare with > dirty accounting. > > Correct?
Correct. And though I eventually realized the nonlinear dirty accounting issue (which I did highlight in the patch comment), I'd forgotten all about needing CONFIG_HIGHPTE in addition to CONFIG_HIGHMEM - yes, that increased the probability of overlooking it too.
No excuses that we did miss it in all these months those patches have been around; but it's an object lesson in the trouble rare paths give.
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