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[S390] fix page change underindication in pgste_update_all 

This patch makes sure we don't underindicate _PAGE_CHANGED in case
we have a race between an operation that changes the page and this
code path that hits us between page_get_storage_key and
page_set_storage_key. Note that we still have a potential
underindication on _PAGE_REFERENCED in the unlikely event that
the page was changed but not referenced _and_ someone references
the page in the race window. That's not considered to be a problem.

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Carsten Otte 2011-12-01 13:32:16 +01:00 committed by Martin Schwidefsky
parent d9ae6772d3
commit 7c81878b34
1 changed files with 4 additions and 4 deletions
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8
arch/s390/include/asm/pgtable.h
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@ -599,10 +599,10 @@ static inline pgste_t pgste_update_all(pte_t *ptep, pgste_t pgste)
skey = page_get_storage_key(address);
bits = skey & (_PAGE_CHANGED | _PAGE_REFERENCED);
/* Clear page changed & referenced bit in the storage key */
if (bits) {
skey ^= bits;
page_set_storage_key(address, skey, 1);
}
if (bits & _PAGE_CHANGED)
page_set_storage_key(address, skey ^ bits, 1);
else if (bits)
page_reset_referenced(address);
/* Transfer page changed & referenced bit to guest bits in pgste */
pgste_val(pgste) |= bits << 48; /* RCP_GR_BIT & RCP_GC_BIT */
/* Get host changed & referenced bits from pgste */