On Fri, 15 Nov 2013 10:29:56 +0800 majianpeng [off-list ref] wrote:

quoted

quoted

Yes.How about those code:
spin_lock_irq(&conf->resync_lock);
retry_check:
        if (need_to_wait_for_sync(conf, bio)) {
                conf->nr_waiting++;
                /* Wait for the barrier to drop.
                 * However if there are already pending
                 * requests (preventing the barrier from
                 * rising completely), and the
                 * pre-process bio queue isn't empty,
                 * then don't wait, as we need to empty
                 * that queue to get the nr_pending
                 * count down.
                 */
                wait_event_lock_irq(conf->wait_barrier,
                                    !conf->array_frozen &&
                                    (!conf->barrier ||
                                    (conf->nr_pending &&
                                     current->bio_list &&
                                     !bio_list_empty(current->bio_list))),
                                    conf->resync_lock);
                conf->nr_waiting--;
				goto retry_check;

quoted

It would look a lot better if you made it a while loop:

while (need_to_wait....) {
    nr_waiting++
    wait_event.....
    nr_waiting--
if (bio_data_dir.....

For this, i think it don;t need while() or recheck.
The code should:

if (nedd_to_wait...) {
	nr_waiting++
	wait_event.....
	nr_waiting--
}
if (bio && bio_data_dir(bio) == WRITE) {
	 do;
}

I think again need_to_wait...(),it must return false. So we don't recheck this.
Or am I missing something?

An 'if' is fine.  I just didn't like the goto.
If you can send me the updated patch in a day or 2 I should be able to get it
into the current merge window.

thanks,
NeilBrown