Reviewed-by: Sage Weil <sage@xxxxxxxxxxx>
On Tue, 9 Oct 2012, Alex Elder wrote:
> This patch defines a single function, queue_con_delay() to call
> queue_delayed_work() for a connection. It basically generalizes
> what was previously queue_con() by adding the delay argument.
> queue_con() is now a simple helper that passes 0 for its delay.
> queue_con_delay() returns 0 if it queued work or an errno if it
> did not for some reason.
>
> If con_work() finds the BACKOFF flag set for a connection, it now
> calls queue_con_delay() to handle arranging to start again after a
> delay.
>
>
> Note about connection reference counts: con_work() only ever gets
> called as a work item function. At the time that work is scheduled,
> a reference to the connection is acquired, and the corresponding
> con_work() call is then responsible for dropping that reference
> before it returns.
>
> Previously, the backoff handling inside con_work() silently handed
> off its reference to delayed work it scheduled. Now that
> queue_con_delay() is used, a new reference is acquired for the
> newly-scheduled work, and the original reference is dropped by the
> con->ops->put() call at the end of the function.
>
> Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
> ---
> net/ceph/messenger.c | 38 +++++++++++++++++++++++---------------
> 1 file changed, 23 insertions(+), 15 deletions(-)
>
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 9170c20..77cc8b1 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -2244,22 +2244,33 @@ bad_tag:
>
>
> /*
> - * Atomically queue work on a connection. Bump @con reference to
> - * avoid races with connection teardown.
> + * Atomically queue work on a connection after the specified delay.
> + * Bump @con reference to avoid races with connection teardown.
> + * Returns 0 if work was queued, or an error code otherwise.
> */
> -static void queue_con(struct ceph_connection *con)
> +static int queue_con_delay(struct ceph_connection *con, unsigned long delay)
> {
> if (!con->ops->get(con)) {
> - dout("queue_con %p ref count 0\n", con);
> - return;
> + dout("%s %p ref count 0\n", __func__, con);
> +
> + return -ENOENT;
> }
>
> - if (!queue_delayed_work(ceph_msgr_wq, &con->work, 0)) {
> - dout("queue_con %p - already queued\n", con);
> + if (!queue_delayed_work(ceph_msgr_wq, &con->work, delay)) {
> + dout("%s %p - already queued\n", __func__, con);
> con->ops->put(con);
> - } else {
> - dout("queue_con %p\n", con);
> +
> + return -EBUSY;
> }
> +
> + dout("%s %p %lu\n", __func__, con, delay);
> +
> + return 0;
> +}
> +
> +static void queue_con(struct ceph_connection *con)
> +{
> + (void) queue_con_delay(con, 0);
> }
>
> /*
> @@ -2294,14 +2305,11 @@ restart:
>
> if (test_and_clear_bit(CON_FLAG_BACKOFF, &con->flags)) {
> dout("con_work %p backing off\n", con);
> - if (queue_delayed_work(ceph_msgr_wq, &con->work,
> - round_jiffies_relative(con->delay))) {
> - dout("con_work %p backoff %lu\n", con, con->delay);
> - mutex_unlock(&con->mutex);
> - return;
> - } else {
> + ret = queue_con_delay(con,
> round_jiffies_relative(con->delay));
> + if (ret) {
> dout("con_work %p FAILED to back off %lu\n", con,
> con->delay);
> + BUG_ON(ret == -ENOENT);
> set_bit(CON_FLAG_BACKOFF, &con->flags);
> }
> goto done;
> --
> 1.7.9.5
>
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