rmap: extend try_to_unmap() to be usable by split_huge_page()

Add support for two ttu_flags:

  - TTU_SPLIT_HUGE_PMD would split PMD if it's there, before trying to
    unmap page;

  - TTU_RMAP_LOCKED indicates that caller holds relevant rmap lock;

Also, change rwc->done to !page_mapcount() instead of !page_mapped().
try_to_unmap() works on pte level, so we are really interested in the
mappedness of this small page rather than of the compound page it's a
part of.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 4 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e1a177c..11d1567 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3006,15 +3006,12 @@ out:
 	}
 }
 
-static void split_huge_pmd_address(struct vm_area_struct *vma,
-				    unsigned long address)
+void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
 
-	VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
-
 	pgd = pgd_offset(vma->vm_mm, address);
 	if (!pgd_present(*pgd))
 		return;