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drbd: only wakeup if something changed in update_peer_seq 

This commit got it wrong:
    drbd: Make the peer_seq updating code more obvious

    Make it more clear that update_peer_seq() is supposed to wake up the
    seq_wait queue whenever the sequence number changes.

We don't need to wake up everytime we receive a sequence number
that is _different_ from our currently stored "newest" sequence number,
but only if we receive a sequence number _newer_ than what we already
have, when we actually change mdev->peer_seq.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2011-02-23 16:10:01 +01:00 committed by Philipp Reisner
parent a5df0e199c
commit 3c13b680ce
1 changed files with 5 additions and 4 deletions
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9
drivers/block/drbd/drbd_receiver.c
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@ -1734,14 +1734,15 @@ static bool need_peer_seq(struct drbd_conf *mdev)
static void update_peer_seq(struct drbd_conf *mdev, unsigned int peer_seq)
{
unsigned int old_peer_seq;
unsigned int newest_peer_seq;
if (need_peer_seq(mdev)) {
spin_lock(&mdev->peer_seq_lock);
old_peer_seq = mdev->peer_seq;
mdev->peer_seq = seq_max(mdev->peer_seq, peer_seq);
newest_peer_seq = seq_max(mdev->peer_seq, peer_seq);
mdev->peer_seq = newest_peer_seq;
spin_unlock(&mdev->peer_seq_lock);
if (old_peer_seq != peer_seq)
/* wake up only if we actually changed mdev->peer_seq */
if (peer_seq == newest_peer_seq)
wake_up(&mdev->seq_wait);
}
}