badpage: zap print_bad_pte on swap and file

Complete zap_pte_range()'s coverage of bad pagetable entries by calling
print_bad_pte() on a pte_file in a linear vma and on a bad swap entry.
That needs free_swap_and_cache() to tell it, which will also have shown
one of those "swap_free" errors (but with much less information).

Similar checks in fork's copy_one_pte()?  No, that would be more noisy
than helpful: we'll see them when parent and child exec or exit.

Where do_nonlinear_fault() calls print_bad_pte(): omit !VM_CAN_NONLINEAR
case, that could only be a bug in sys_remap_file_pages(), not a bad pte.
VM_FAULT_OOM rather than VM_FAULT_SIGBUS?  Well, okay, that is consistent
with what happens if do_swap_page() operates a bad swap entry; but don't
we have patches to be more careful about killing when VM_FAULT_OOM?

Signed-off-by: Hugh Dickins <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/swap.h

@@ -302,7 +302,7 @@ extern swp_entry_t get_swap_page_of_type(int);
 extern int swap_duplicate(swp_entry_t);
 extern int valid_swaphandles(swp_entry_t, unsigned long *);
 extern void swap_free(swp_entry_t);
-extern void free_swap_and_cache(swp_entry_t);
+extern int free_swap_and_cache(swp_entry_t);
 extern int swap_type_of(dev_t, sector_t, struct block_device **);
 extern unsigned int count_swap_pages(int, int);
 extern sector_t map_swap_page(struct swap_info_struct *, pgoff_t);
@@ -352,14 +352,8 @@ static inline void show_swap_cache_info(void)
 {
 }
 
-static inline void free_swap_and_cache(swp_entry_t swp)
-{
-}
-
-static inline int swap_duplicate(swp_entry_t swp)
-{
-	return 0;
-}
+#define free_swap_and_cache(swp)	is_migration_entry(swp)
+#define swap_duplicate(swp)		is_migration_entry(swp)
 
 static inline void swap_free(swp_entry_t swp)
 {

mm/memory.c

@@ -810,8 +810,12 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 		 */
 		if (unlikely(details))
 			continue;
-		if (!pte_file(ptent))
-			free_swap_and_cache(pte_to_swp_entry(ptent));
+		if (pte_file(ptent)) {
+			if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
+				print_bad_pte(vma, addr, ptent, NULL);
+		} else if
+		  (unlikely(!free_swap_and_cache(pte_to_swp_entry(ptent))))
+			print_bad_pte(vma, addr, ptent, NULL);
 		pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 	} while (pte++, addr += PAGE_SIZE, (addr != end && *zap_work > 0));
 
@@ -2707,8 +2711,7 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
 		return 0;
 
-	if (unlikely(!(vma->vm_flags & VM_NONLINEAR) ||
-			!(vma->vm_flags & VM_CAN_NONLINEAR))) {
+	if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
 		/*
 		 * Page table corrupted: show pte and kill process.
 		 */

mm/swapfile.c

@@ -571,13 +571,13 @@ int try_to_free_swap(struct page *page)
  * Free the swap entry like above, but also try to
  * free the page cache entry if it is the last user.
  */
-void free_swap_and_cache(swp_entry_t entry)
+int free_swap_and_cache(swp_entry_t entry)
 {
-	struct swap_info_struct * p;
+	struct swap_info_struct *p;
 	struct page *page = NULL;
 
 	if (is_migration_entry(entry))
-		return;
+		return 1;
 
 	p = swap_info_get(entry);
 	if (p) {
@@ -603,6 +603,7 @@ void free_swap_and_cache(swp_entry_t entry)
 		unlock_page(page);
 		page_cache_release(page);
 	}
+	return p != NULL;
 }
 
 #ifdef CONFIG_HIBERNATION