On 09/22/2015 09:57 PM, Ewan Milne wrote:
> On Thu, 2015-08-27 at 14:41 +0200, Hannes Reinecke wrote:
>> When we receive a unit attention code of 'ALUA state changed'
>> we should recheck the state, as it might be due to an implicit
>> ALUA state transition.
>> At the same time a workqueue item might already be queued, which
>> should be started immediately to avoid any delays.
>>
>> Signed-off-by: Hannes Reinecke <h...@suse.de>
>> ---
>> drivers/scsi/device_handler/scsi_dh_alua.c | 48
>> +++++++++++++++---------------
>> 1 file changed, 24 insertions(+), 24 deletions(-)
>>
>> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c
>> b/drivers/scsi/device_handler/scsi_dh_alua.c
>> index 85fd597..8717fd3 100644
>> --- a/drivers/scsi/device_handler/scsi_dh_alua.c
>> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
>> @@ -118,7 +118,7 @@ static char print_alua_state(int);
>> static void alua_rtpg_work(struct work_struct *work);
>> static void alua_stpg_work(struct work_struct *work);
>> static void alua_qdata_work(struct work_struct *work);
>> -static void alua_check(struct scsi_device *sdev);
>> +static void alua_check(struct scsi_device *sdev, bool force);
>>
>> static void release_port_group(struct kref *kref)
>> {
>> @@ -423,7 +423,7 @@ static char print_alua_state(int state)
>> }
>>
>> static int alua_check_sense(struct scsi_device *sdev,
>> - struct scsi_sense_hdr *sense_hdr)
>> + struct scsi_sense_hdr *sense_hdr)
>> {
>> switch (sense_hdr->sense_key) {
>> case NOT_READY:
>> @@ -432,36 +432,34 @@ static int alua_check_sense(struct scsi_device *sdev,
>> * LUN Not Accessible - ALUA state transition
>> * Kickoff worker to update internal state.
>> */
>> - alua_check(sdev);
>> - return ADD_TO_MLQUEUE;
>> + alua_check(sdev, false);
>> + return NEEDS_RETRY;
>> }
>> break;
>> case UNIT_ATTENTION:
>> - if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00)
>> - /*
>> - * Power On, Reset, or Bus Device Reset, just retry.
>> - */
>> - return ADD_TO_MLQUEUE;
>> - if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
>> - /*
>> - * Device internal reset
>> - */
>> - return ADD_TO_MLQUEUE;
>> - if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
>> + if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
>> /*
>> - * Mode Parameter Changed
>> + * Power On, Reset, or Bus Device Reset.
>> + * Might have obscured a state transition,
>> + * so schedule a recheck.
>> */
>> + alua_check(sdev, true);
>> return ADD_TO_MLQUEUE;
>> - if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06)
>> + }
>> + if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
>> /*
>> * ALUA state changed
>> */
>> + alua_check(sdev, true);
>> return ADD_TO_MLQUEUE;
>> - if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07)
>> + }
>> + if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
>> /*
>> * Implicit ALUA state transition failed
>> */
>> + alua_check(sdev, true);
>> return ADD_TO_MLQUEUE;
>> + }
>> break;
>> }
>>
>> @@ -811,7 +809,7 @@ static void alua_qdata_work(struct work_struct *work)
>>
>> static void alua_rtpg_queue(struct alua_port_group *pg,
>> struct scsi_device *sdev,
>> - struct alua_queue_data *qdata)
>> + struct alua_queue_data *qdata, bool force)
>> {
>> int start_queue = 0;
>> unsigned long flags;
>> @@ -832,7 +830,9 @@ static void alua_rtpg_queue(struct alua_port_group *pg,
>> pg->rtpg_sdev = sdev;
>> scsi_device_get(sdev);
>> start_queue = 1;
>> - }
>> + } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force)
>> + start_queue = 1;
>> +
>> spin_unlock_irqrestore(&pg->rtpg_lock, flags);
>>
>> if (start_queue)
>> @@ -873,7 +873,7 @@ static int alua_initialize(struct scsi_device *sdev,
>> struct alua_dh_data *h)
>> mutex_unlock(&h->init_mutex);
>> if (pg) {
>> pg->expiry = 0;
>> - alua_rtpg_queue(pg, sdev, NULL);
>> + alua_rtpg_queue(pg, sdev, NULL, true);
>> kref_put(&pg->kref, release_port_group);
>> }
>> return error;
>> @@ -982,7 +982,7 @@ static int alua_activate(struct scsi_device *sdev,
>> pg->flags |= ALUA_OPTIMIZE_STPG;
>> spin_unlock_irqrestore(&pg->rtpg_lock, flags);
>> }
>> - alua_rtpg_queue(pg, sdev, qdata);
>> + alua_rtpg_queue(pg, sdev, qdata, true);
>> kref_put(&pg->kref, release_port_group);
>> out:
>> if (fn)
>> @@ -996,7 +996,7 @@ out:
>> *
>> * Check the device status
>> */
>> -static void alua_check(struct scsi_device *sdev)
>> +static void alua_check(struct scsi_device *sdev, bool force)
>> {
>> struct alua_dh_data *h = sdev->handler_data;
>> struct alua_port_group *pg;
>> @@ -1009,7 +1009,7 @@ static void alua_check(struct scsi_device *sdev)
>> }
>> kref_get(&pg->kref);
>> rcu_read_unlock();
>> - alua_rtpg_queue(pg, sdev, NULL);
>> + alua_rtpg_queue(pg, sdev, NULL, force);
>> kref_put(&pg->kref, release_port_group);
>> rcu_read_unlock();
>> }
>
> I think this change goes along with the previous patch in terms of the
> design, so we'll have to see how that turns out. Fundamentally, though,
> this changes the handling for LUN Not Accessible - ALUA state transition
> to be NEEDS_RETRY instead of ADD_TO_MLQUEUE, so what is the effect of that?
>
ADD_TO_MLQUEUE will always be retried, NEEDS_RETRY is bounded by the
number of retries.
Originally we had to return ADD_TO_MLQUEUE so to be sure to retry until
the transition is done, causing quite some retries.
As now we're polling the device from a workqueue we can terminate
the number of retries by returning NEEDS_RETRY, knowing that the polling
(and/or sense code evaluation) will tell us when the transition is finished.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
h...@suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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