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Date: Wed, 17 May 2006 18:42:32 +0100 (BST)
From: Hugh Dickins <hugh@veritas.com>
To: Eric Paris <eparis@redhat.com>
Subject: Re: [PATCH] Fix do_mlock so page alignment is to hugepage boundries
	when needed
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On Wed, 17 May 2006, Eric Paris wrote:
> sys_m{,un}lock and do_mlock all align memory references and the length
> of the mlock given by userspace to page boundaries.  If the page being
> mlocked is a hugepage instead of a normal page the start and finish of
> the mlock will still only be aligned to normal page boundaries.
> Ultimately upon the process exiting we will eventually call unmap_vmas
> which will call unmap_hugepage_range for all of the ranges.
> unmap_hugepage_range checks to make sure the beginning and the end of
> the range are actually hugepage aligned and if not will BUG().  Since we
> only aligned to a normal page boundary the end of the first range and
> the beginning of the second will likely (unless userspace passed of
> values already hugepage aligned) not be hugepage aligned and thus we
> bomb.

When did you test this?  It should have been fixed in 2.6.11 onwards
by split_vma()'s simple:

	if (is_vm_hugetlb_page(vma) && (addr & ~HPAGE_MASK))
		return -EINVAL;

Hugh