badpage: simplify page_alloc flag check+clear

Simplify the PAGE_FLAGS checking and clearing when freeing and allocating
a page: check the same flags as before when freeing, clear ALL the flags
(unless PageReserved) when freeing, check ALL flags off when allocating.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 14 insertions, 30 deletions

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 628ec0802492..219a523ecdb0 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -373,31 +373,22 @@ static inline void __ClearPageTail(struct page *page)
 #define __PG_MLOCKED            0
 #endif
 
-#define PAGE_FLAGS      (1 << PG_lru   | 1 << PG_private   | 1 << PG_locked | \
-                         1 << PG_buddy | 1 << PG_writeback | \
-                         1 << PG_slab  | 1 << PG_swapcache | 1 << PG_active | \
-                         __PG_UNEVICTABLE | __PG_MLOCKED)
-
-/*
- * Flags checked in bad_page().  Pages on the free list should not have
- * these flags set.  It they are, there is a problem.
- */
-#define PAGE_FLAGS_CLEAR_WHEN_BAD (PAGE_FLAGS | \
-                1 << PG_reclaim | 1 << PG_dirty | 1 << PG_swapbacked)
-
 /*
  * Flags checked when a page is freed.  Pages being freed should not have
  * these flags set.  It they are, there is a problem.
  */
-#define PAGE_FLAGS_CHECK_AT_FREE (PAGE_FLAGS | 1 << PG_reserved)
+#define PAGE_FLAGS_CHECK_AT_FREE \
+        (1 << PG_lru   | 1 << PG_private   | 1 << PG_locked | \
+         1 << PG_buddy | 1 << PG_writeback | 1 << PG_reserved | \
+         1 << PG_slab  | 1 << PG_swapcache | 1 << PG_active | \
+         __PG_UNEVICTABLE | __PG_MLOCKED)
 
 /*
  * Flags checked when a page is prepped for return by the page allocator.
- * Pages being prepped should not have these flags set.  It they are, there
- * is a problem.
+ * Pages being prepped should not have any flags set.  It they are set,
+ * there has been a kernel bug or struct page corruption.
  */
-#define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | \
-                1 << PG_reserved | 1 << PG_dirty | 1 << PG_swapbacked)
+#define PAGE_FLAGS_CHECK_AT_PREP        ((1 << NR_PAGEFLAGS) - 1)
 
 #endif /* !__GENERATING_BOUNDS_H */
 #endif  /* PAGE_FLAGS_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 31c512410a99..b90a74d28485 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -231,7 +231,6 @@ static void bad_page(struct page *page)
         printk(KERN_EMERG "Trying to fix it up, but a reboot is needed\n"
                 KERN_EMERG "Backtrace:\n");
         dump_stack();
-        page->flags &= ~PAGE_FLAGS_CLEAR_WHEN_BAD;
         set_page_count(page, 0);
         reset_page_mapcount(page);
         page->mapping = NULL;
@@ -468,16 +467,16 @@ static inline int free_pages_check(struct page *page)
                 (page_count(page) != 0)  |
                 (page->flags & PAGE_FLAGS_CHECK_AT_FREE)))
                 bad_page(page);
-        if (PageDirty(page))
-                __ClearPageDirty(page);
-        if (PageSwapBacked(page))
-                __ClearPageSwapBacked(page);
         /*
          * For now, we report if PG_reserved was found set, but do not
          * clear it, and do not free the page.  But we shall soon need
          * to do more, for when the ZERO_PAGE count wraps negative.
          */
-        return PageReserved(page);
+        if (PageReserved(page))
+                return 1;
+        if (page->flags & PAGE_FLAGS_CHECK_AT_PREP)
+                page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
+        return 0;
 }
 
 /*
@@ -621,13 +620,7 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
         if (PageReserved(page))
                 return 1;
 
-        page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_reclaim |
-                        1 << PG_referenced | 1 << PG_arch_1 |
-                        1 << PG_owner_priv_1 | 1 << PG_mappedtodisk
-#ifdef CONFIG_UNEVICTABLE_LRU
-                        | 1 << PG_mlocked
-#endif
-                        );
+        page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
         set_page_private(page, 0);
         set_page_refcounted(page);