Re: [PATCH 3/3] hugetlb: fix absurd HugePages_Rsvd

["Mika Penttilä" <mika.penttila@kolumbus.fi>]

Hugh Dickins wrote:
> If you truncated an mmap'ed hugetlbfs file, then faulted on the truncated
> area, /proc/meminfo's HugePages_Rsvd wrapped hugely "negative".  Reinstate
> my preliminary i_size check before attempting to allocate the page (though
> this only fixes the most obvious case: more work will be needed here).
>
> Signed-off-by: Hugh Dickins <hugh@veritas.com>
> ___
>
> This is not a complete solution (what if hugetlb_no_page is actually
> racing with truncate_hugepages?), and there are several other accounting
> anomalies in here (private versus shared pages, hugetlbfs quota handling);
> but those all need more thought.  It'll probably make sense to use i_mutex
> instead of hugetlb_instantiation_mutex, so locking out truncation and mmap.
>
>  mm/hugetlb.c |    3 +++
>  1 file changed, 3 insertions(+)
>
> --- 2.6.19-rc3/mm/hugetlb.c	2006-10-24 04:34:37.000000000 +0100
> +++ linux/mm/hugetlb.c	2006-10-24 16:23:17.000000000 +0100
> @@ -478,6 +478,9 @@ int hugetlb_no_page(struct mm_struct *mm
>  retry:
>  	page = find_lock_page(mapping, idx);
>  	if (!page) {
> +		size = i_size_read(mapping->host) >> HPAGE_SHIFT;
> +		if (idx >= size)
> +			goto out;
>  		if (hugetlb_get_quota(mapping))
>  			goto out;
>  		page = alloc_huge_page(vma, address);
>
> --
>   
Shouldn't it be something like following ?

size = (i_size_read(mapping->host) + HPAGE_SIZE - 1) >> HPAGE_SHIFT;



If so this was wrong in the original code also.

--Mika

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>