[PATCH] mm: include/linux/mm.h page_mapping() bug of swapcache case

[PATCH] mm: include/linux/mm.h page_mapping() bug of swapcache case

[vik]

I run linux swap less and xwindows become not respond sometime. The bug is share swapper_space over all mappings of memory.
Also the dmesg show several lines which is hidden before. Test of 3.0.51 fail near the end of kernel compilation. I run 3.0.50
successly a hours.

*** linux-3.0.50.a/include/linux/mm.h	2012-10-31 20:51:59.000000000 +0400
--- linux-3.0.50.b/include/linux/mm.h	2012-11-17 19:44:56.864762720 +0400
***************
*** 787,793 ****
  	struct address_space *mapping = page->mapping;
  
  	VM_BUG_ON(PageSlab(page));
! 	if (unlikely(PageSwapCache(page)))
  		mapping = &swapper_space;
  	else if ((unsigned long)mapping & PAGE_MAPPING_ANON)
  		mapping = NULL;
--- 787,793 ----
  	struct address_space *mapping = page->mapping;
  
  	VM_BUG_ON(PageSlab(page));
! 	if (likely(PageSwapCache(page)))
  		mapping = &swapper_space;
  	else if ((unsigned long)mapping & PAGE_MAPPING_ANON)
  		mapping = NULL;

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