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Commit 7c81878b authored by Carsten Otte's avatar Carsten Otte Committed by Martin Schwidefsky
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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: default avatarCarsten Otte <cotte@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent d9ae6772

arch/s390/include/asm/pgtable.h

+4 −4
Original line number Diff line number Diff line
@@ -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 */