On Thu, May 8, 2008 at 7:15 PM, Neil Brown <neilb@xxxxxxx> wrote: > On Thursday May 8, dan.j.williams@xxxxxxxxx wrote: > > @@ -133,8 +137,10 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks) > > > > disk->rdev = rdev; > > > > + spin_lock(&conf->device_lock); > > blk_queue_stack_limits(mddev->queue, > > rdev->bdev->bd_disk->queue); > > + spin_unlock(&conf->device_lock); > > /* as we don't honour merge_bvec_fn, we must never risk > > * violating it, so limit ->max_sector to one PAGE, as > > * a one page request is never in violation. > > This shouldn't be necessary. > There is no actual race here -- mddev->queue->queue_flags is not going to be > accessed by anyone else until do_md_run does > mddev->queue->make_request_fn = mddev->pers->make_request; > which is much later. > So we only need to be sure that "queue_is_locked" doesn't complain. > And as q->queue_lock is still NULL at this point, it won't complain. > > I think that the *only* change that is needs is to put > > > > + /* blk-core uses queue_lock to verify protection of the queue flags */ > > + mddev->queue->queue_lock = &conf->device_lock; > > after each > > > + spin_lock_init(&conf->device_lock); > > i.e. in raid1.c, raid10.c and raid5.c > > ?? Yes, locking shouldn't be needed at those points; however, the warning still fires because blk_queue_stack_limits() is using queue_flag_clear() instead of queue_flag_unlocked(). Taking a look at converting it to queue_flag_clear_unlocked() uncovered a couple more overlooked sites (multipath.c:multipath_add_disk and raid1.c:raid1_add_disk) where ->run has already been called... The options I am thinking of all seem ugly: 1/ keep the unnecessary locking in MD 2/ make blk_queue_stack_limits() use queue_flag_clear_unlocked() even though it needs to be locked sometimes 3/ conditionally use queue_flag_clear_unlocked if !t->queue_lock -- Dan I'm having a h -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
