On Sun, May 28, 2023 at 11:16:16PM -0700, Hugh Dickins wrote: > +#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. > + */ > +#define config_might_irq_save(flags) local_irq_save(flags) > +#define config_might_irq_restore(flags) local_irq_restore(flags) > +#else > +#define config_might_irq_save(flags) > +#define config_might_irq_restore(flags) I don't like the name. It should indicate that it's PMD-related, so pmd_read_start(flags) / pmd_read_end(flags)?
