On Sun, Aug 07, 2022 at 07:37:22AM -0400, Mikulas Patocka wrote:
> @@ -135,6 +133,49 @@ BUFFER_FNS(Meta, meta)
> BUFFER_FNS(Prio, prio)
> BUFFER_FNS(Defer_Completion, defer_completion)
>
> +static __always_inline void set_buffer_uptodate(struct buffer_head *bh)
> +{
> + /*
> + * make it consistent with folio_mark_uptodate
> + * pairs with smp_acquire__after_ctrl_dep in buffer_uptodate
> + */
> + smp_wmb();
> + set_bit(BH_Uptodate, &bh->b_state);
> +}
> +
> +static __always_inline void clear_buffer_uptodate(struct buffer_head *bh)
> +{
> + clear_bit(BH_Uptodate, &bh->b_state);
> +}
> +
> +static __always_inline int buffer_uptodate(const struct buffer_head *bh)
> +{
> + bool ret = test_bit(BH_Uptodate, &bh->b_state);
> + /*
> + * make it consistent with folio_test_uptodate
> + * pairs with smp_wmb in set_buffer_uptodate
> + */
> + if (ret)
> + smp_acquire__after_ctrl_dep();
> + return ret;
> +}
This all works for me. While we have the experts paying attention,
would it be better to do
return smp_load_acquire(&bh->b_state) & (1L << BH_Uptodate) > 0;
> +static __always_inline void set_buffer_locked(struct buffer_head *bh)
> +{
> + set_bit(BH_Lock, &bh->b_state);
> +}
> +
> +static __always_inline int buffer_locked(const struct buffer_head *bh)
> +{
> + bool ret = test_bit(BH_Lock, &bh->b_state);
> + /*
> + * pairs with smp_mb__after_atomic in unlock_buffer
> + */
> + if (!ret)
> + smp_acquire__after_ctrl_dep();
> + return ret;
> +}
Are there places that think that lock/unlock buffer implies a memory
barrier?
