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Subject[PATCH] s390: lost dirty bits.
Hi Andrew,
we just tracked down a severe bug in the memory management
code of s390. There is a race window where s390 can loose
a dirty bit. I never expected that SetPageUptodate is called
on an already up to date page...

blue skies,
Martin.

---

[PATCH] s390: lost dirty bits.

The SetPageUptodate function is called for pages that are already
up to date. The arch_set_page_uptodate function of s390 may not
clear the dirty bit in that case otherwise a dirty bit which is set
between the start of an i/o for a writeback and a following call
to SetPageUptodate is lost.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diffstat:

--- linux-2.5/include/asm-s390/pgtable.h 24 Mar 2004 18:18:22 -0000 1.23
+++ linux-2.5/include/asm-s390/pgtable.h 15 Jun 2004 16:43:35 -0000 1.23.2.1
@@ -652,7 +652,8 @@

#define arch_set_page_uptodate(__page) \
do { \
- asm volatile ("sske %0,%1" : : "d" (0), \
+ if (!PageUptodate(__page)) \
+ asm volatile ("sske %0,%1" : : "d" (0), \
"a" (__pa((__page-mem_map) << PAGE_SHIFT)));\
} while (0)

-
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