Reviewed-by: Sage Weil <sage@xxxxxxxxxxx>
On Tue, 9 Oct 2012, Alex Elder wrote:
> If ceph_fault() is unable to queue work after a delay, it sets the
> BACKOFF connection flag so con_work() will attempt to do so.
>
> In con_work(), when BACKOFF is set, if queue_delayed_work() doesn't
> result in newly-queued work, it simply ignores this condition and
> proceeds as if no backoff delay were desired. There are two
> problems with this--one of which is a bug.
>
> The first problem is simply that the intended behavior is to back
> off, and if we aren't able queue the work item to run after a delay
> we're not doing that.
>
> The only reason queue_delayed_work() won't queue work is if the
> provided work item is already queued. In the messenger, this
> means that con_work() is already scheduled to be run again. So
> if we simply set the BACKOFF flag again when this occurs, we know
> the next con_work() call will again attempt to hold off activity
> on the connection until after the delay.
>
> The second problem--the bug--is a leak of a reference count. If
> queue_delayed_work() returns 0 in con_work(), con->ops->put() drops
> the connection reference held on entry to con_work(). However,
> processing is (was) allowed to continue, and at the end of the
> function a second con->ops->put() is called.
>
> This patch fixes both problems.
>
> Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
> ---
> net/ceph/messenger.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index f9f65fe..ece06bc 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -2300,10 +2300,11 @@ restart:
> mutex_unlock(&con->mutex);
> return;
> } else {
> - con->ops->put(con);
> dout("con_work %p FAILED to back off %lu\n", con,
> con->delay);
> + set_bit(CON_FLAG_BACKOFF, &con->flags);
> }
> + goto done;
> }
>
> if (con->state == CON_STATE_STANDBY) {
> --
> 1.7.9.5
>
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