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SubjectRe: [PATCH] x86: fix PAE pmd_bad bootup warning
From
Date
On Thu, 2008-05-08 at 17:11 +0200, Hans Rosenfeld wrote:
>
> On Thu, May 08, 2008 at 07:52:30AM -0700, Dave Hansen wrote:
> > On Thu, 2008-05-08 at 16:34 +0200, Hans Rosenfeld wrote:
> > > The huge page is leaked only when the
> > > /proc/self/pagemap entry for the huge page is read.
> >
> > Well, that's an interesting data point! :)
> >
> > Are you running any of your /proc/<pid>/pagemap patches?
>
> No additional patches. The problem already existed before we agreed on
> the change to the pagemap code to just include the page size in the
> values returned, and not doing any special huge page handling. I suspect
> the page walking code used by /proc/pid/pagemap is doing something nasty
> when it sees a huge page as it doesn't know how to handle it.

Is there anything in your dmesg?

static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
const struct mm_walk *walk, void *private)
{
pmd_t *pmd;
unsigned long next;
int err = 0;

pmd = pmd_offset(pud, addr);
do {
next = pmd_addr_end(addr, end);
if (pmd_none_or_clear_bad(pmd)) {
if (walk->pte_hole)
err = walk->pte_hole(addr, next, private);
if (err)
break;
continue;


There was a discussion on LKML in the last couple of days about
pmd_bad() triggering on huge pages. Perhaps we're clearing the mapping
with the pmd_none_or_clear_bad(), and *THAT* is leaking the page.

-- Dave



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