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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Linus Torvalds <torvalds@osdl.org>, Andrew Morton <akpm@osdl.org>
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Date: Mon, 21 Feb 2005 16:09:33 +1100
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Cc: linuxppc-dev list <linuxppc-dev@ozlabs.org>
Subject: [PATCH] ppc32: fix ptep_test_and_clear_young
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Hi !

ppc32's implementation of ptep_test_and_clear_young() has a logic error
which makes it fail to flush the hash table. Thus PAGE_ACCESSED is
almost never set again after beeing cleared (unless something else cause
that hash entry to be flushed).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Index: linux-work/include/asm-ppc/pgtable.h
===================================================================
--- linux-work.orig/include/asm-ppc/pgtable.h	2005-01-24 17:09:50.000000000 +1100
+++ linux-work/include/asm-ppc/pgtable.h	2005-02-21 16:00:26.000000000 +1100
@@ -560,12 +560,12 @@
 static inline int ptep_test_and_clear_young(pte_t *ptep)
 {
 	unsigned long old;
-	old = (pte_update(ptep, _PAGE_ACCESSED, 0) & _PAGE_ACCESSED);
+	old = pte_update(ptep, _PAGE_ACCESSED, 0);
 #if _PAGE_HASHPTE != 0
 	if (old & _PAGE_HASHPTE)
 		flush_hash_one_pte(ptep);
 #endif
-	return old != 0;
+	return (old & _PAGE_ACCESSED) != 0;
 }
 
 static inline int ptep_test_and_clear_dirty(pte_t *ptep)