Re: [Qemu-devel] [PATCH 1/2] mirror: Rewrite mirror_iteration

[Paolo Bonzini]

On 17/11/2015 12:41, Fam Zheng wrote:
> +        /* Wait for I/O to this cluster (from a previous iteration) to be
> +         * done.*/
> +        while (test_bit(next_chunk, s->in_flight_bitmap)) {
> +            trace_mirror_yield_in_flight(s, next_sector, s->in_flight);
> +            s->waiting_for_io = true;
> +            qemu_coroutine_yield();
> +            s->waiting_for_io = false;
> +        }
> +

I think this could just "break" if nb_chunks > 0, like

        if (test_bit(next_chunk, s->in_flight_bitmap)) {
                if (nb_chunks > 0) {
                        break;
                }
                mirror_wait_for_io(s);
                /* Now retry.  */
        } else {
                hbitmap_next = hbitmap_iter_next(&s->hbi);
                assert(hbitmap_next == next_sector);
                nb_chunks++;
        }

but it can be done later (the usage of mirror_wait_for_io is a hint :)).

There's a typo though:

> +    /* Clear dirty bits before querying the block status, because
> +     * calling bdrv_reset_dirty_bitmap could yield - if some blocks are 
> marked

That's bdrv_get_block_status_above.

> +     * dirty in this window, we need to know.
> +     */

Thanks,

Paolo