From dfa7e20cc0d1a7a620def4dce97de1ae5375f99b Mon Sep 17 00:00:00 2001
From: Russ Anderson <rja@sgi.com>
Date: Mon, 9 Jun 2008 11:18:45 -0500
Subject: [PATCH] mm: Minor clean-up of page flags in mm/page_alloc.c

Minor source code cleanup of page flags in mm/page_alloc.c.
Move the definition of the groups of bits to page-flags.h.

The purpose of this clean up is that the next patch will
conditionally add a page flag to the groups.  Doing that
in a header file is cleaner than adding #ifdefs to the
C code.

Signed-off-by: Russ Anderson <rja@sgi.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 include/linux/page-flags.h | 24 ++++++++++++++++++++++++
 mm/page_alloc.c            | 34 +++-------------------------------
 2 files changed, 27 insertions(+), 31 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 590cff32415d..f31debfac926 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -306,5 +306,29 @@ static inline void __ClearPageTail(struct page *page)
 }
 
 #endif /* !PAGEFLAGS_EXTENDED */
+
+#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)
+
+/*
+ * 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)
+
+/*
+ * 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)
+
+/*
+ * 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.
+ */
+#define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | 1 << PG_reserved | 1 << PG_dirty)
+
 #endif /* !__GENERATING_BOUNDS_H */
 #endif	/* PAGE_FLAGS_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8e83f02cd2d3..2f552955a02f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -237,16 +237,7 @@ 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 &= ~(1 << PG_lru	|
-			1 << PG_private |
-			1 << PG_locked	|
-			1 << PG_active	|
-			1 << PG_dirty	|
-			1 << PG_reclaim |
-			1 << PG_slab    |
-			1 << PG_swapcache |
-			1 << PG_writeback |
-			1 << PG_buddy );
+	page->flags &= ~PAGE_FLAGS_CLEAR_WHEN_BAD;
 	set_page_count(page, 0);
 	reset_page_mapcount(page);
 	page->mapping = NULL;
@@ -463,16 +454,7 @@ static inline int free_pages_check(struct page *page)
 		(page->mapping != NULL)  |
 		(page_get_page_cgroup(page) != NULL) |
 		(page_count(page) != 0)  |
-		(page->flags & (
-			1 << PG_lru	|
-			1 << PG_private |
-			1 << PG_locked	|
-			1 << PG_active	|
-			1 << PG_slab	|
-			1 << PG_swapcache |
-			1 << PG_writeback |
-			1 << PG_reserved |
-			1 << PG_buddy ))))
+		(page->flags & PAGE_FLAGS_CHECK_AT_FREE)))
 		bad_page(page);
 	if (PageDirty(page))
 		__ClearPageDirty(page);
@@ -616,17 +598,7 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
 		(page->mapping != NULL)  |
 		(page_get_page_cgroup(page) != NULL) |
 		(page_count(page) != 0)  |
-		(page->flags & (
-			1 << PG_lru	|
-			1 << PG_private	|
-			1 << PG_locked	|
-			1 << PG_active	|
-			1 << PG_dirty	|
-			1 << PG_slab    |
-			1 << PG_swapcache |
-			1 << PG_writeback |
-			1 << PG_reserved |
-			1 << PG_buddy ))))
+		(page->flags & PAGE_FLAGS_CHECK_AT_PREP)))
 		bad_page(page);
 
 	/*
-- 
2.20.1