Re: [PATCH] hugetlb: avoid gratuitous BUG_ON in hugetlb_fault() -> hugetlb_cow()

[Hillf Danton]

On Mon, Apr 30, 2012 at 3:04 AM, Chris Metcalf <cmetcalf@xxxxxxxxxx> wrote:
> Commit 66aebce747eaf added code to avoid a race condition by
> elevating the page refcount in hugetlb_fault() while calling
> hugetlb_cow(). ÂHowever, one code path in hugetlb_cow() includes
> an assertion that the page count is 1, whereas it may now also
> have the value 2 in this path. ÂConsensus is that this BUG_ON
> has served its purpose, so rather than extending it to cover both
> cases, we just remove it.
>
> Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
> ---

Acked-by: Hillf Danton <dhillf@xxxxxxxxx>

> Âmm/hugetlb.c | Â Â1 -
> Â1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index cd65cb1..baaad5d 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2498,7 +2498,6 @@ retry_avoidcopy:
> Â Â Â Â Â Â Â Âif (outside_reserve) {
> Â Â Â Â Â Â Â Â Â Â Â ÂBUG_ON(huge_pte_none(pte));
> Â Â Â Â Â Â Â Â Â Â Â Âif (unmap_ref_private(mm, vma, old_page, address)) {
> - Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â BUG_ON(page_count(old_page) != 1);
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ÂBUG_ON(huge_pte_none(pte));
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Âspin_lock(&mm->page_table_lock);
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Âptep = huge_pte_offset(mm, address & huge_page_mask(h));
> --
> 1.6.5.2
>
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