mm: introduce fault_env

The idea borrowed from Peter's patch from patchset on speculative page
faults[1]:

Instead of passing around the endless list of function arguments,
replace the lot with a single structure so we can change context without
endless function signature changes.

The changes are mostly mechanical with exception of faultaround code:
filemap_map_pages() got reworked a bit.

This patch is preparation for the next one.

[1] http://lkml.kernel.org/r/20141020222841.302891540@infradead.org

Link: http://lkml.kernel.org/r/1466021202-61880-9-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/internal.h b/mm/internal.h
index e153175..9b6a6c4 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -36,9 +36,7 @@
 /* Do not use these with a slab allocator */
 #define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
 
-extern int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
-			unsigned long address, pte_t *page_table, pmd_t *pmd,
-			unsigned int flags, pte_t orig_pte);
+int do_swap_page(struct fault_env *fe, pte_t orig_pte);
 
 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 		unsigned long floor, unsigned long ceiling);