Make do_swap_page redo the fault

It is better to redo the complete fault if do_swap_page() finds
that the page is not in PageSwapCache() because the page migration
code may have replaced the swap pte already with a pte pointing
to valid memory.

do_swap_page may interpret an invalid swap pte entry without this
patch because we do not reload the pte if we are looping back.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.17-rc1/mm/memory.c
===================================================================
--- linux-2.6.17-rc1.orig/mm/memory.c	2006-04-02 20:22:10.000000000 -0700
+++ linux-2.6.17-rc1/mm/memory.c	2006-04-03 22:22:56.000000000 -0700
@@ -1879,7 +1879,6 @@ static int do_swap_page(struct mm_struct
 		goto out;
 
 	entry = pte_to_swp_entry(orig_pte);
-again:
 	page = lookup_swap_cache(entry);
 	if (!page) {
  		swapin_readahead(entry, address, vma);
@@ -1907,7 +1906,7 @@ again:
 		/* Page migration has occured */
 		unlock_page(page);
 		page_cache_release(page);
-		goto again;
+		goto out;
 	}
 
 	/*