On 17:48, NeilBrown wrote:
> When a barrier arrives, we send a zero-length barrier to every active
> device. When that completes - and if the original request was not
> empty - we submit the barrier request itself (with the barrier flag
> cleared) and the submit a fresh load of zero length barriers.
s/the/then
> +/*
> + * Generic barrier handling for md
> + */
> +
> +static void md_end_barrier(struct bio *bio, int err)
> +{
> + mdk_rdev_t *rdev = bio->bi_private;
> + mddev_t *mddev = rdev->mddev;
> + if (err == -EOPNOTSUPP && mddev->barrier != (void*)1)
How about
#define POST_REQUEST_BARRIER ((void*)1)
?
> + rcu_read_lock();
> + list_for_each_entry_rcu(rdev, &mddev->disks, same_set)
> + if (rdev->raid_disk >= 0 &&
> + !test_bit(Faulty, &rdev->flags)) {
> + /* Take two references, one is dropped
> + * when request finishes, one after
> + * we reclaim rcu_read_lock
> + */
> + struct bio *bi;
> + atomic_inc(&rdev->nr_pending);
> + atomic_inc(&rdev->nr_pending);
> + rcu_read_unlock();
> + bi = bio_alloc(GFP_KERNEL, 0);
> + bi->bi_end_io = md_end_barrier;
> + bi->bi_private = rdev;
> + bi->bi_bdev = rdev->bdev;
> + atomic_inc(&mddev->flush_pending);
> + submit_bio(WRITE_BARRIER, bi);
> + rcu_read_lock();
> + rdev_dec_pending(rdev, mddev);
> + }
> + rcu_read_unlock();
Calling atomic_inc() twice isn't an atomic operation any more. If
this doesn't matter (because all modifications of rdev->nr_pending
are supposed to happen within RCU read-side critical sections) then
why is rdev->nr_pending an atomic_t at all?
> +void md_barrier_request(mddev_t *mddev, struct bio *bio)
> +{
> + mdk_rdev_t *rdev;
> +
> + spin_lock_irq(&mddev->write_lock);
> + wait_event_lock_irq(mddev->sb_wait,
> + !mddev->barrier,
> + mddev->write_lock, /*nothing*/);
> + mddev->barrier = bio;
> + spin_unlock_irq(&mddev->write_lock);
> +
> + atomic_set(&mddev->flush_pending, 1);
> + INIT_WORK(&mddev->barrier_work, md_submit_barrier);
> +
> + rcu_read_lock();
> + list_for_each_entry_rcu(rdev, &mddev->disks, same_set)
> + if (rdev->raid_disk >= 0 &&
> + !test_bit(Faulty, &rdev->flags)) {
> + struct bio *bi;
> +
> + atomic_inc(&rdev->nr_pending);
> + atomic_inc(&rdev->nr_pending);
> + rcu_read_unlock();
> + bi = bio_alloc(GFP_KERNEL, 0);
> + bi->bi_end_io = md_end_barrier;
> + bi->bi_private = rdev;
> + bi->bi_bdev = rdev->bdev;
> + atomic_inc(&mddev->flush_pending);
> + submit_bio(WRITE_BARRIER, bi);
> + rcu_read_lock();
> + rdev_dec_pending(rdev, mddev);
> + }
> + rcu_read_unlock();
This loop is identical to the one above, so it might make sense
to put it into a separate function.
Regards
Andre
--
The only person who always got his work done by Friday was Robinson Crusoe
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