diff options
Diffstat (limited to 'mm/pgtable-generic.c')
| -rw-r--r-- | mm/pgtable-generic.c | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c index 400e5a045848..b9a0c2137cc1 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c @@ -232,12 +232,41 @@ pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address, #endif #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ +#if defined(CONFIG_GUP_GET_PXX_LOW_HIGH) && \ + (defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RCU)) +/* + * See the comment above ptep_get_lockless() in include/linux/pgtable.h: + * the barriers in pmdp_get_lockless() cannot guarantee that the value in + * pmd_high actually belongs with the value in pmd_low; but holding interrupts + * off blocks the TLB flush between present updates, which guarantees that a + * successful __pte_offset_map() points to a page from matched halves. + */ +static unsigned long pmdp_get_lockless_start(void) +{ + unsigned long irqflags; + + local_irq_save(irqflags); + return irqflags; +} +static void pmdp_get_lockless_end(unsigned long irqflags) +{ + local_irq_restore(irqflags); +} +#else +static unsigned long pmdp_get_lockless_start(void) { return 0; } +static void pmdp_get_lockless_end(unsigned long irqflags) { } +#endif + pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp) { + unsigned long irqflags; pmd_t pmdval; rcu_read_lock(); + irqflags = pmdp_get_lockless_start(); pmdval = pmdp_get_lockless(pmd); + pmdp_get_lockless_end(irqflags); + if (pmdvalp) *pmdvalp = pmdval; if (unlikely(pmd_none(pmdval) || is_pmd_migration_entry(pmdval))) |