On Wed, 2013-10-16 at 09:20 +0200, Hannes Reinecke wrote:
> Use a workqueue for processing ALUA state transitions; this allows
> us to process implicit delay properly.
>
> Signed-off-by: Hannes Reinecke <h...@suse.de>
> ---
> drivers/target/target_core_alua.c | 174
> +++++++++++++++++++++++++++-----------
> include/target/target_core_base.h | 4 +
> 2 files changed, 128 insertions(+), 50 deletions(-)
>
<SNIP>
> +static int core_alua_do_transition_tg_pt(
> + struct t10_alua_tg_pt_gp *tg_pt_gp,
> + int new_state,
> + int explicit)
> +{
> + struct se_device *dev = tg_pt_gp->tg_pt_gp_dev;
> + DECLARE_COMPLETION_ONSTACK(wait);
> +
> + /* Nothing to be done here */
> + if (atomic_read(&tg_pt_gp->tg_pt_gp_alua_access_state) == new_state)
> + return 0;
> +
> + if (new_state == ALUA_ACCESS_STATE_TRANSITION)
> + return -EAGAIN;
> +
> + /*
> + * Flush any pending transitions
> + */
> + if (!explicit && tg_pt_gp->tg_pt_gp_implicit_trans_secs &&
> + atomic_read(&tg_pt_gp->tg_pt_gp_alua_access_state) ==
> + ALUA_ACCESS_STATE_TRANSITION) {
> + /* Just in case */
> + tg_pt_gp->tg_pt_gp_alua_pending_state = new_state;
> + tg_pt_gp->tg_pt_gp_transition_complete = &wait;
> + flush_delayed_work(&tg_pt_gp->tg_pt_gp_transition_work);
> + wait_for_completion(&wait);
> + tg_pt_gp->tg_pt_gp_transition_complete = NULL;
> + return 0;
> + }
> +
> + /*
> + * Save the old primary ALUA access state, and set the current state
> + * to ALUA_ACCESS_STATE_TRANSITION.
> + */
> + tg_pt_gp->tg_pt_gp_alua_previous_state =
> + atomic_read(&tg_pt_gp->tg_pt_gp_alua_access_state);
> + tg_pt_gp->tg_pt_gp_alua_pending_state = new_state;
> +
> + atomic_set(&tg_pt_gp->tg_pt_gp_alua_access_state,
> + ALUA_ACCESS_STATE_TRANSITION);
> + tg_pt_gp->tg_pt_gp_alua_access_status = (explicit) ?
> + ALUA_STATUS_ALTERED_BY_EXPLICIT_STPG :
> + ALUA_STATUS_ALTERED_BY_IMPLICIT_ALUA;
> +
> + /*
> + * Check for the optional ALUA primary state transition delay
> + */
> + if (tg_pt_gp->tg_pt_gp_trans_delay_msecs != 0)
> + msleep_interruptible(tg_pt_gp->tg_pt_gp_trans_delay_msecs);
> +
> + /*
> + * Take a reference for workqueue item
> + */
> + spin_lock(&dev->t10_alua.tg_pt_gps_lock);
> + atomic_inc(&tg_pt_gp->tg_pt_gp_ref_cnt);
> + smp_mb__after_atomic_inc();
> + spin_unlock(&dev->t10_alua.tg_pt_gps_lock);
> +
> + if (!explicit && tg_pt_gp->tg_pt_gp_implicit_trans_secs) {
> + unsigned long transition_tmo;
> +
> + transition_tmo = tg_pt_gp->tg_pt_gp_implicit_trans_secs * HZ;
> + queue_delayed_work(tg_pt_gp->tg_pt_gp_dev->tmr_wq,
> + &tg_pt_gp->tg_pt_gp_transition_work,
> + transition_tmo);
> + } else {
> + tg_pt_gp->tg_pt_gp_transition_complete = &wait;
> + queue_delayed_work(tg_pt_gp->tg_pt_gp_dev->tmr_wq,
> + &tg_pt_gp->tg_pt_gp_transition_work, 0);
> + wait_for_completion(&wait);
> + tg_pt_gp->tg_pt_gp_transition_complete = NULL;
> + }
Mmm, the trans_delay_msecs delay seems a bit out of place now..
How about dropping it's usage with msleep_interruptible() above, and
instead combining it with the delay passed into queue_delayed_work()..?
--nab
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