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mm: Allow arches to provide ptep_get() 

Since commit 9e343b467c ("READ_ONCE: Enforce atomicity for
{READ,WRITE}_ONCE() memory accesses") it is not possible anymore to
use READ_ONCE() to access complex page table entries like the one
defined for powerpc 8xx with 16k size pages.

Define a ptep_get() helper that architectures can override instead
of performing a READ_ONCE() on the page table entry pointer.

Fixes: 9e343b467c ("READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/087fa12b6e920e32315136b998aa834f99242695.1592225558.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2020-06-15 12:57:58 +00:00 committed by Michael Ellerman
parent 55ca22633a
commit 481e980a7c
3 changed files with 9 additions and 2 deletions
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2
include/asm-generic/hugetlb.h
View File

@ -122,7 +122,7 @@ static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
#ifndef __HAVE_ARCH_HUGE_PTEP_GET
static inline pte_t huge_ptep_get(pte_t *ptep)
{
return READ_ONCE(*ptep);
return ptep_get(ptep);
}
#endif

7
include/linux/pgtable.h
View File

@ -249,6 +249,13 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
}
#endif
#ifndef __HAVE_ARCH_PTEP_GET
static inline pte_t ptep_get(pte_t *ptep)
{
return READ_ONCE(*ptep);
}
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,

2
mm/gup.c
View File

@ -2196,7 +2196,7 @@ static inline pte_t gup_get_pte(pte_t *ptep)
*/
static inline pte_t gup_get_pte(pte_t *ptep)
{
return READ_ONCE(*ptep);
return ptep_get(ptep);
}
#endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */