Revert "UBUNTU: SAUCE: mm: Respect FOLL_FORCE/FOLL_COW for thp"

This reverts commit 9c49adf9 so
the upstream stable version can be applied.

BugLink: http://bugs.launchpad.net/bugs/1694621Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

mm/huge_memory.c

@@ -1272,16 +1272,6 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	return ret;
 }
 
-/*
- * FOLL_FORCE can write to even unwritable pmd's, but only
- * after we've gone through a COW cycle and they are dirty.
- */
-static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
-{
-	return pmd_write(pmd) ||
-		((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
-}
-
 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
 				   unsigned long addr,
 				   pmd_t *pmd,
@@ -1292,7 +1282,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
 
 	assert_spin_locked(pmd_lockptr(mm, pmd));
 
-	if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
+	if (flags & FOLL_WRITE && !pmd_write(*pmd))
 		goto out;
 
 	/* Avoid dumping huge zero page */