powerpc/thp: Use ACCESS_ONCE when loading pmdp
commit 7e467245bf
upstream.
We would get wrong results in compiler recomputed old_pmd. Avoid
that by using ACCESS_ONCE
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -84,7 +84,9 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
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* atomically mark the linux large page PMD busy and dirty
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*/
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do {
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old_pmd = pmd_val(*pmdp);
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pmd_t pmd = ACCESS_ONCE(*pmdp);
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old_pmd = pmd_val(pmd);
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/* If PMD busy, retry the access */
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if (unlikely(old_pmd & _PAGE_BUSY))
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return 0;
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