Re: [PATCH] general split_vma hugetlb fix

[William Lee Irwin III <wli@holomorphy.com>]

On Fri, Feb 11, 2005 at 08:06:08PM +0000, Hugh Dickins wrote:
> My recent do_munmap hugetlb fix has proved inadequate.  There are
> other places (madvise, mbind, mlock, mprotect) where split_vma is
> called.  Only mprotect excludes a hugetlb vma: the others are in
> danger of splitting at a misaligned address, causing later BUGs.
> So move the ~HPAGE_MASK check from do_munmap to split_vma itself;
> and fix up those places (madvise and mlock) which expect split_vma
> can fail only with -ENOMEM, and wish to convert that to -EAGAIN.
> (It appears genuine that some of these syscalls should be failing
> with -ENOMEM and some with -EAGAIN, so respect those behaviours.)
> madvise_dontneed doesn't use split_vma, but is equally in danger
> of causing a hugetlb BUG via zap_page_range.  Whereas elsewhere the
> patch is permissive (allowing the operation on a hugetlb vma even when
> pointless, so long as it doesn't missplit it), here we must use -EINVAL
> on any hugetlb vma, since a page fault would hit the BUG in its nopage.
> Signed-off-by: Hugh Dickins <hugh@veritas.com>

As usual, excellent work, Hugh. akpm, Linus, please apply.

Acked-by: William Irwin <wli@holomorphy.com>


-- wli