• Andy Whitcroft's avatar
    hugetlbfs: handle pages higher order than MAX_ORDER · 69d177c2
    Andy Whitcroft authored
    
    
    When working with hugepages, hugetlbfs assumes that those hugepages are
    smaller than MAX_ORDER.  Specifically it assumes that the mem_map is
    contigious and uses that to optimise access to the elements of the mem_map
    that represent the hugepage.  Gigantic pages (such as 16GB pages on
    powerpc) by definition are of greater order than MAX_ORDER (larger than
    MAX_ORDER_NR_PAGES in size).  This means that we can no longer make use of
    the buddy alloctor guarentees for the contiguity of the mem_map, which
    ensures that the mem_map is at least contigious for maximmally aligned
    areas of MAX_ORDER_NR_PAGES pages.
    
    This patch adds new mem_map accessors and iterator helpers which handle
    any discontiguity at MAX_ORDER_NR_PAGES boundaries.  It then uses these to
    implement gigantic page versions of copy_huge_page and clear_huge_page,
    and to allow follow_hugetlb_page handle gigantic pages.
    Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
    Cc: Jon Tollefson <kniht@linux.vnet.ibm.com>
    Cc: Mel Gorman <mel@csn.ul.ie>
    Cc: Nick Piggin <nickpiggin@yahoo.com.au>
    Cc: Christoph Lameter <cl@linux-foundation.org>
    Cc: <stable@kernel.org>		[2.6.27.x]
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    69d177c2