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mm: Fix pmd_read_atomic()

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AFAICT there's no reason to do anything different than what we do for
PTEs. Make it so (also affects SH).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20221022114424.711181252%40infradead.org
This commit is contained in:
Peter Zijlstra 2020-11-26 17:16:22 +01:00 • committed by Dave Hansen
parent 0862ff059c
commit 024d232ae4
2 changed files with 37 additions and 66 deletions
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47
include/linux/pgtable.h
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@ -298,6 +298,13 @@ static inline pte_t ptep_get(pte_t *ptep)
}
#endif
#ifndef __HAVE_ARCH_PMDP_GET
static inline pmd_t pmdp_get(pmd_t *pmdp)
{
return READ_ONCE(*pmdp);
}
#endif
#ifdef CONFIG_GUP_GET_PTE_LOW_HIGH
/*
* For walking the pagetables without holding any locks. Some architectures
@ -340,15 +347,42 @@ static inline pte_t ptep_get_lockless(pte_t *ptep)
return pte;
}
#else /* CONFIG_GUP_GET_PTE_LOW_HIGH */
#define ptep_get_lockless ptep_get_lockless
#if CONFIG_PGTABLE_LEVELS > 2
static inline pmd_t pmdp_get_lockless(pmd_t *pmdp)
{
pmd_t pmd;
do {
pmd.pmd_low = pmdp->pmd_low;
smp_rmb();
pmd.pmd_high = pmdp->pmd_high;
smp_rmb();
} while (unlikely(pmd.pmd_low != pmdp->pmd_low));
return pmd;
}
#define pmdp_get_lockless pmdp_get_lockless
#endif /* CONFIG_PGTABLE_LEVELS > 2 */
#endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
/*
* We require that the PTE can be read atomically.
*/
#ifndef ptep_get_lockless
static inline pte_t ptep_get_lockless(pte_t *ptep)
{
return ptep_get(ptep);
}
#endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
#endif
#ifndef pmdp_get_lockless
static inline pmd_t pmdp_get_lockless(pmd_t *pmdp)
{
return pmdp_get(pmdp);
}
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
@ -1318,17 +1352,10 @@ static inline int pud_trans_unstable(pud_t *pud)
#endif
}
#ifndef pmd_read_atomic
static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
{
/*
* Depend on compiler for an atomic pmd read. NOTE: this is
* only going to work, if the pmdval_t isn't larger than
* an unsigned long.
*/
return *pmdp;
return pmdp_get_lockless(pmdp);
}
#endif
#ifndef arch_needs_pgtable_deposit
#define arch_needs_pgtable_deposit() (false)