Re: oops in copy_page_rep()

From: Dave Jones
Date: Sun Jan 06 2013 - 19:37:18 EST

On Sat, Jan 05, 2013 at 07:57:39PM -0800, Linus Torvalds wrote:
> Adding more people in case somebody else has any idea. Anybody?
> On Sat, Jan 5, 2013 at 7:22 AM, Dave Jones <davej@xxxxxxxxxx> wrote:
> > I have no idea what happened here, but this is the first time I've seen this one.
> > This was running a tree pulled yesterday afternoon.
> >
> > BUG: unable to handle kernel paging request at ffff880100201000
> This is %rsi, which is the source for the page copy:
> copy_user_highpage()->
> copy_user_page()->
> copy_page()->
> copy_page_rep
> I don't know exactly which copy_user_highpage() case this is from, the
> call trace implies this *could* be a hugepage, and those functions do
> copy pages individually in a loop too.

investigating the huge page theory a little further I'm a bit confused.
The kernel on that machine has THP enabled, and the cpu supports it (an old amd64), but..

$ cat /sys/kernel/mm/hugepages/hugepages-2048kB/*

I was expecting at least one of those to be non-zero.

/sys/kernel/mm/transparent_hugepage/khugepaged/full_scans and pages_collapsed
are both non-zero, so it's been busy doing _something_.

Is this expected behaviour ?


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