[PATCH] hugetlb: release pages in the error path of hugetlb_cow()(was: Re: 3.2-rc2+: Reported regressions from 3.0 and 3.1)

[Michal Hocko]

On Mon 21-11-11 14:18:29, Linus Torvalds wrote:
> On Mon, Nov 21, 2011 at 1:49 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> >
> > Subject    : hugetlb oops on 3.1.0-rc8-devel
> > Submitter  : Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> > Date       : 2011-11-01 22:20
> > Message-ID : CALCETrW1mpVCz2tO5roaz1r6vnno+srHR-dHA6_pkRi2qiCfdw@xxxxxxxxxxxxxx
> > References : http://marc.info/?l=linux-kernel&m=132018604426692&w=2
> 
> Despite the subject line, that's not an oops, it's a BUG_ON().
> 
> And it *should* be fixed by commit ea4039a34c4c ("hugetlb: release
> pages in the error path of hugetlb_cow()") although I don't think Andy
> ever confirmed that (since it was hard to trigger).

AFAICS the issue has been introduced by 0fe6e20b (hugetlb, rmap:
add reverse mapping for hugepage) in 2.6.36-rc1 so this is a stable
material. I do not see the patch in any stable branch so here we go.
The patch is on top of 3.0.y branch and it applies as is to 3.1.y
as well.
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