[PATCH] cleanup page_swap_cache

Removes some redundant BUG checks - trueness of PageSwapCache() implies
that page->mapping is non-NULL, and we've already checked that.

mm/page_alloc.c

@@ -103,8 +103,6 @@ static void __free_pages_ok (struct page *page, unsigned int order)
 		BUG();
 	if (!VALID_PAGE(page))
 		BUG();
-	if (PageSwapCache(page))
-		BUG();
 	if (PageLocked(page))
 		BUG();
 	if (PageLRU(page))
@@ -297,8 +295,6 @@ static struct page * balance_classzone(zone_t * classzone, unsigned int gfp_mask
 						BUG();
 					if (!VALID_PAGE(page))
 						BUG();
-					if (PageSwapCache(page))
-						BUG();
 					if (PageLocked(page))
 						BUG();
 					if (PageLRU(page))

mm/page_io.c

@@ -96,8 +96,6 @@ void rw_swap_page(int rw, struct page *page)
 		PAGE_BUG(page);
 	if (!PageSwapCache(page))
 		PAGE_BUG(page);
-	if (page->mapping != &swapper_space)
-		PAGE_BUG(page);
 	if (!rw_swap_page_base(rw, entry, page))
 		unlock_page(page);
 }
@@ -113,8 +111,6 @@ void rw_swap_page_nolock(int rw, swp_entry_t entry, char *buf)
 	
 	if (!PageLocked(page))
 		PAGE_BUG(page);
-	if (PageSwapCache(page))
-		PAGE_BUG(page);
 	if (page->mapping)
 		PAGE_BUG(page);
 	/* needs sync_page to wait I/O completation */