• Naoya Horiguchi's avatar
    pagemap: fix pfn calculation for hugepage · 116354d1
    Naoya Horiguchi authored
    When we look into pagemap using page-types with option -p, the value of
    pfn for hugepages looks wrong (see below.) This is because pte was
    evaluated only once for one vma although it should be updated for each
    hugepage.  This patch fixes it.
    
      $ page-types -p 3277 -Nl -b huge
      voffset   offset  len     flags
      7f21e8a00 11e400  1       ___U___________H_G________________
      7f21e8a01 11e401  1ff     ________________TG________________
                   ^^^
      7f21e8c00 11e400  1       ___U___________H_G________________
      7f21e8c01 11e401  1ff     ________________TG________________
                   ^^^
    
    One hugepage contains 1 head page and 511 tail pages in x86_64 and each
    two lines represent each hugepage.  Voffset and offset mean virtual
    address and physical address in the page unit, respectively.  The
    different hugepages should not have the same offset value.
    
    With this patch applied:
    
      $ page-types -p 3386 -Nl -b huge
      voffset   offset   len    flags
      7fec7a600 112c00   1      ___UD__________H_G________________
      7fec7a601 112c01   1ff    ________________TG________________
                   ^^^
      7fec7a800 113200   1      ___UD__________H_G________________
      7fec7a801 113201   1ff    ________________TG________________
                   ^^^
                   OK
    
    More info:
    
    - This patch modifies walk_page_range()'s hugepage walker.  But the
      change only affects pagemap_read(), which is the only caller of hugepage
      callback.
    
    - Without this patch, hugetlb_entry() callback is called per vma, that
      doesn't match the natural expectation from its name.
    
    - With this patch, hugetlb_entry() is called per hugepte entry and the
      callback can become much simpler.
    Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Acked-by: default avatarMatt Mackall <mpm@selenic.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    116354d1
pagewalk.c 4.66 KB