mm: rename __do_fault() -> do_fault()

Current __do_fault() is awful and unmaintainable.  These patches try to
sort it out by split __do_fault() into three destinct codepaths:

 - to handle read page fault;
 - to handle write page fault to private mappings;
 - to handle write page fault to shared mappings;

I also found page refcount leak in PageHWPoison() path of __do_fault().

This patch (of 7):

do_fault() is unused: no reason for underscores.
Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memory.c

@@ -2748,7 +2748,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		 * bit after it clear all dirty ptes, but before a racing
 		 * do_wp_page installs a dirty pte.
 		 *
-		 * __do_fault is protected similarly.
+		 * do_fault is protected similarly.
 		 */
 		if (!page_mkwrite) {
 			wait_on_page_locked(dirty_page);
@@ -3287,7 +3287,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 }
 
 /*
- * __do_fault() tries to create a new page mapping. It aggressively
+ * do_fault() tries to create a new page mapping. It aggressively
  * tries to share with existing pages, but makes a separate copy if
  * the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
  * the next page fault.
@@ -3299,7 +3299,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
  * but allow concurrent faults), and pte neither mapped nor locked.
  * We return with mmap_sem still held, but pte unmapped and unlocked.
  */
-static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		unsigned long address, pmd_t *pmd,
 		pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
 {
@@ -3496,7 +3496,7 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 			- vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 
 	pte_unmap(page_table);
-	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
+	return do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
 }
 
 /*
@@ -3528,7 +3528,7 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	}
 
 	pgoff = pte_to_pgoff(orig_pte);
-	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
+	return do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
 }
 
 static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,