[SCSI] scsi_dh: Make rdac hardware handler's activate() async

Batch up MODE_SELECT in rdac device handler.

LSI RDAC storage has the capability of handling mode selects for
multiple luns in a same command. Make use of that ability to send
as few MODE SELECTs as possible to the storage controller as possible.

This patch creates a work queue and queues up activate requests
when a MODE SELECT is sent down the wire. When that MODE SELECT
completes, it compiles queued up activate requests for multiple
luns into a single MODE SELECT.

This reduces the time to do failover/failback of large number of LUNS.

Signed-off-by: Babu Moger <babu.moger@lsi.com>
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 100 insertions, 8 deletions

diff --git a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c
index be362adbd8e7..47cfe1c49c3e 100644
--- a/drivers/scsi/device_handler/scsi_dh_rdac.c
+++ b/drivers/scsi/device_handler/scsi_dh_rdac.c
@@ -22,6 +22,7 @@
 #include <scsi/scsi.h>
 #include <scsi/scsi_eh.h>
 #include <scsi/scsi_dh.h>
+#include <linux/workqueue.h>
 
 #define RDAC_NAME "rdac"
 #define RDAC_RETRY_COUNT 5
@@ -138,7 +139,13 @@ struct rdac_controller {
         } mode_select;
         u8      index;
         u8      array_name[ARRAY_LABEL_LEN];
+        spinlock_t              ms_lock;
+        int                     ms_queued;
+        struct work_struct      ms_work;
+        struct scsi_device      *ms_sdev;
+        struct list_head        ms_head;
 };
+
 struct c8_inquiry {
         u8      peripheral_info;
         u8      page_code; /* 0xC8 */
@@ -198,8 +205,17 @@ static const char *lun_state[] =
         "owned (AVT mode)",
 };
 
+struct rdac_queue_data {
+        struct list_head        entry;
+        struct rdac_dh_data     *h;
+        activate_complete       callback_fn;
+        void                    *callback_data;
+};
+
 static LIST_HEAD(ctlr_list);
 static DEFINE_SPINLOCK(list_lock);
+static struct workqueue_struct *kmpath_rdacd;
+static void send_mode_select(struct work_struct *work);
 
 /*
  * module parameter to enable rdac debug logging.
@@ -281,7 +297,6 @@ static struct request *rdac_failover_get(struct scsi_device *sdev,
                 rdac_pg->subpage_code = 0x1;
                 rdac_pg->page_len[0] = 0x01;
                 rdac_pg->page_len[1] = 0x28;
-                rdac_pg->lun_table[h->lun] = 0x81;
         } else {
                 struct rdac_pg_legacy *rdac_pg;
 
@@ -291,7 +306,6 @@ static struct request *rdac_failover_get(struct scsi_device *sdev,
                 common = &rdac_pg->common;
                 rdac_pg->page_code = RDAC_PAGE_CODE_REDUNDANT_CONTROLLER;
                 rdac_pg->page_len = 0x68;
-                rdac_pg->lun_table[h->lun] = 0x81;
         }
         common->rdac_mode[1] = RDAC_MODE_TRANSFER_SPECIFIED_LUNS;
         common->quiescence_timeout = RDAC_QUIESCENCE_TIME;
@@ -325,6 +339,7 @@ static void release_controller(struct kref *kref)
         struct rdac_controller *ctlr;
         ctlr = container_of(kref, struct rdac_controller, kref);
 
+        flush_workqueue(kmpath_rdacd);
         spin_lock(&list_lock);
         list_del(&ctlr->node);
         spin_unlock(&list_lock);
@@ -363,6 +378,11 @@ static struct rdac_controller *get_controller(u8 *subsys_id, u8 *slot_id,
 
         kref_init(&ctlr->kref);
         ctlr->use_ms10 = -1;
+        ctlr->ms_queued = 0;
+        ctlr->ms_sdev = NULL;
+        spin_lock_init(&ctlr->ms_lock);
+        INIT_WORK(&ctlr->ms_work, send_mode_select);
+        INIT_LIST_HEAD(&ctlr->ms_head);
         list_add(&ctlr->node, &ctlr_list);
 done:
         spin_unlock(&list_lock);
@@ -490,7 +510,7 @@ static int set_mode_select(struct scsi_device *sdev, struct rdac_dh_data *h)
 }
 
 static int mode_select_handle_sense(struct scsi_device *sdev,
-                                    unsigned char *sensebuf)
+                                        unsigned char *sensebuf)
 {
         struct scsi_sense_hdr sense_hdr;
         int err = SCSI_DH_IO, ret;
@@ -533,11 +553,29 @@ done:
         return err;
 }
 
-static int send_mode_select(struct scsi_device *sdev, struct rdac_dh_data *h)
+static void send_mode_select(struct work_struct *work)
 {
+        struct rdac_controller *ctlr =
+                container_of(work, struct rdac_controller, ms_work);
         struct request *rq;
+        struct scsi_device *sdev = ctlr->ms_sdev;
+        struct rdac_dh_data *h = get_rdac_data(sdev);
         struct request_queue *q = sdev->request_queue;
         int err, retry_cnt = RDAC_RETRY_COUNT;
+        struct rdac_queue_data *tmp, *qdata;
+        LIST_HEAD(list);
+        u8 *lun_table;
+
+        spin_lock(&ctlr->ms_lock);
+        list_splice_init(&ctlr->ms_head, &list);
+        ctlr->ms_queued = 0;
+        ctlr->ms_sdev = NULL;
+        spin_unlock(&ctlr->ms_lock);
+
+        if (ctlr->use_ms10)
+                lun_table = ctlr->mode_select.expanded.lun_table;
+        else
+                lun_table = ctlr->mode_select.legacy.lun_table;
 
 retry:
         err = SCSI_DH_RES_TEMP_UNAVAIL;
@@ -545,6 +583,10 @@ retry:
         if (!rq)
                 goto done;
 
+        list_for_each_entry(qdata, &list, entry) {
+                lun_table[qdata->h->lun] = 0x81;
+        }
+
         RDAC_LOG(RDAC_LOG_FAILOVER, sdev, "array %s, ctlr %d, "
                 "%s MODE_SELECT command",
                 (char *) h->ctlr->array_name, h->ctlr->index,
@@ -565,7 +607,41 @@ retry:
         }
 
 done:
-        return err;
+        list_for_each_entry_safe(qdata, tmp, &list, entry) {
+                list_del(&qdata->entry);
+                if (err == SCSI_DH_OK)
+                        qdata->h->state = RDAC_STATE_ACTIVE;
+                if (qdata->callback_fn)
+                        qdata->callback_fn(qdata->callback_data, err);
+                kfree(qdata);
+        }
+        return;
+}
+
+static int queue_mode_select(struct scsi_device *sdev,
+                                activate_complete fn, void *data)
+{
+        struct rdac_queue_data *qdata;
+        struct rdac_controller *ctlr;
+
+        qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
+        if (!qdata)
+                return SCSI_DH_RETRY;
+
+        qdata->h = get_rdac_data(sdev);
+        qdata->callback_fn = fn;
+        qdata->callback_data = data;
+
+        ctlr = qdata->h->ctlr;
+        spin_lock(&ctlr->ms_lock);
+        list_add_tail(&qdata->entry, &ctlr->ms_head);
+        if (!ctlr->ms_queued) {
+                ctlr->ms_queued = 1;
+                ctlr->ms_sdev = sdev;
+                queue_work(kmpath_rdacd, &ctlr->ms_work);
+        }
+        spin_unlock(&ctlr->ms_lock);
+        return SCSI_DH_OK;
 }
 
 static int rdac_activate(struct scsi_device *sdev,
@@ -578,8 +654,11 @@ static int rdac_activate(struct scsi_device *sdev,
         if (err != SCSI_DH_OK)
                 goto done;
 
-        if (h->lun_state == RDAC_LUN_UNOWNED)
-                err = send_mode_select(sdev, h);
+        if (h->lun_state == RDAC_LUN_UNOWNED) {
+                err = queue_mode_select(sdev, fn, data);
+                if (err == SCSI_DH_OK)
+                        return 0;
+        }
 done:
         if (fn)
                 fn(data, err);
@@ -793,13 +872,26 @@ static int __init rdac_init(void)
         int r;
 
         r = scsi_register_device_handler(&rdac_dh);
-        if (r != 0)
+        if (r != 0) {
                 printk(KERN_ERR "Failed to register scsi device handler.");
+                goto done;
+        }
+
+        /*
+         * Create workqueue to handle mode selects for rdac
+         */
+        kmpath_rdacd = create_singlethread_workqueue("kmpath_rdacd");
+        if (!kmpath_rdacd) {
+                scsi_unregister_device_handler(&rdac_dh);
+                printk(KERN_ERR "kmpath_rdacd creation failed.\n");
+        }
+done:
         return r;
 }
 
 static void __exit rdac_exit(void)
 {
+        destroy_workqueue(kmpath_rdacd);
         scsi_unregister_device_handler(&rdac_dh);
 }