scsi_dh_alua: Recheck state on unit attention

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. This allows us to return NEEDS_RETRY
instead of ADD_TO_MLQUEUE, allowing to terminate the retries
after a certain time.
At the same time a workqueue item might already be queued, which
should be started immediately to avoid any delays.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index fbbe85e..ef5d6c3 100644 (file)
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -120,7 +120,8 @@ struct alua_queue_data {
 static void alua_rtpg_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);
+static void alua_check(struct scsi_device *sdev, bool force);
 
 static void release_port_group(struct kref *kref)
 {
@@ -368,7 +369,7 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
        }
        if (sdev->synchronous_alua)
                pg->flags |= ALUA_SYNC_STPG;
-       alua_rtpg_queue(h->pg, sdev, NULL);
+       alua_rtpg_queue(h->pg, sdev, NULL, true);
        spin_unlock(&h->pg_lock);
 
        if (old_pg)
@@ -404,18 +405,24 @@ static int alua_check_sense(struct scsi_device *sdev,
 {
        switch (sense_hdr->sense_key) {
        case NOT_READY:
-               if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a)
+               if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
                        /*
                         * LUN Not Accessible - ALUA state transition
                         */
-                       return ADD_TO_MLQUEUE;
+                       alua_check(sdev, false);
+                       return NEEDS_RETRY;
+               }
                break;
        case UNIT_ATTENTION:
-               if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00)
+               if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
                        /*
-                        * Power On, Reset, or Bus Device Reset, just retry.
+                        * 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 == 0x29 && sense_hdr->ascq == 0x04)
                        /*
                         * Device internal reset
@@ -426,16 +433,20 @@ static int alua_check_sense(struct scsi_device *sdev,
                         * Mode Parameters Changed
                         */
                        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;
+               }
                if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
                        /*
                         * Inquiry data has changed
@@ -708,7 +719,7 @@ static void alua_rtpg_work(struct work_struct *work)
                spin_unlock_irqrestore(&pg->lock, flags);
                err = alua_rtpg(sdev, pg);
                spin_lock_irqsave(&pg->lock, flags);
-               if (err == SCSI_DH_RETRY) {
+               if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
                        pg->flags &= ~ALUA_PG_RUNNING;
                        pg->flags |= ALUA_PG_RUN_RTPG;
                        spin_unlock_irqrestore(&pg->lock, flags);
@@ -724,7 +735,7 @@ static void alua_rtpg_work(struct work_struct *work)
                spin_unlock_irqrestore(&pg->lock, flags);
                err = alua_stpg(sdev, pg);
                spin_lock_irqsave(&pg->lock, flags);
-               if (err == SCSI_DH_RETRY) {
+               if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
                        pg->flags |= ALUA_PG_RUN_RTPG;
                        pg->interval = 0;
                        pg->flags &= ~ALUA_PG_RUNNING;
@@ -754,7 +765,7 @@ static void alua_rtpg_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;
@@ -767,6 +778,7 @@ static void alua_rtpg_queue(struct alua_port_group *pg,
        if (qdata) {
                list_add_tail(&qdata->entry, &pg->rtpg_list);
                pg->flags |= ALUA_PG_RUN_STPG;
+               force = true;
        }
        if (pg->rtpg_sdev == NULL) {
                pg->interval = 0;
@@ -775,7 +787,15 @@ 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) {
+               pg->flags |= ALUA_PG_RUN_RTPG;
+               /* Do not queue if the worker is already running */
+               if (!(pg->flags & ALUA_PG_RUNNING)) {
+                       kref_get(&pg->kref);
+                       start_queue = 1;
+               }
        }
+
        if (pg->flags & ALUA_SYNC_STPG)
                alua_wq = kaluad_sync_wq;
        spin_unlock_irqrestore(&pg->lock, flags);
@@ -890,7 +910,7 @@ static int alua_activate(struct scsi_device *sdev,
        rcu_read_unlock();
        mutex_unlock(&h->init_mutex);
 
-       alua_rtpg_queue(pg, sdev, qdata);
+       alua_rtpg_queue(pg, sdev, qdata, true);
        kref_put(&pg->kref, release_port_group);
 out:
        if (fn)
@@ -898,6 +918,29 @@ out:
        return 0;
 }
 
+/*
+ * alua_check - check path status
+ * @sdev: device on the path to be checked
+ *
+ * Check the device status
+ */
+static void alua_check(struct scsi_device *sdev, bool force)
+{
+       struct alua_dh_data *h = sdev->handler_data;
+       struct alua_port_group *pg;
+
+       rcu_read_lock();
+       pg = rcu_dereference(h->pg);
+       if (!pg || !kref_get_unless_zero(&pg->kref)) {
+               rcu_read_unlock();
+               return;
+       }
+       rcu_read_unlock();
+
+       alua_rtpg_queue(pg, sdev, NULL, force);
+       kref_put(&pg->kref, release_port_group);
+}
+
 /*
  * alua_prep_fn - request callback
  *