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[dm-devel] RE: [PATCH 3/3] scsi_dh: rdac handler: Batch up MODE SELECTs and send few of them



Tested by: Babu Moger <babu moger lsi com>

> -----Original Message-----
> From: linux-scsi-owner vger kernel org [mailto:linux-scsi-
> owner vger kernel org] On Behalf Of Chandra Seetharaman
> Sent: Monday, April 27, 2009 9:53 PM
> To: linux-scsi vger kernel org
> Cc: dm-devel redhat com; Moger, Babu; michaelc cs wisc edu; Chandra
> Seetharaman
> Subject: [PATCH 3/3] scsi_dh: rdac handler: Batch up MODE SELECTs and send
> few of them
> 
> 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>
> 
> ---
>  drivers/scsi/device_handler/scsi_dh_rdac.c |  117
> ++++++++++++++++++++++++++---
>  1 file changed, 104 insertions(+), 13 deletions(-)
> 
> Index: linux-2.6.29/drivers/scsi/device_handler/scsi_dh_rdac.c
> ===================================================================
> --- linux-2.6.29.orig/drivers/scsi/device_handler/scsi_dh_rdac.c
> +++ linux-2.6.29/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
> @@ -135,6 +136,11 @@ struct rdac_controller {
>  		struct rdac_pg_legacy legacy;
>  		struct rdac_pg_expanded expanded;
>  	} mode_select;
> +	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;
> @@ -195,8 +201,17 @@ 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);
> 
>  static inline struct rdac_dh_data *get_rdac_data(struct scsi_device
> *sdev)
>  {
> @@ -253,7 +268,6 @@ static struct request *rdac_failover_get
>  		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;
> 
> @@ -263,7 +277,6 @@ static struct request *rdac_failover_get
>  		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;
> @@ -297,6 +310,7 @@ static void release_controller(struct kr
>  	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);
> @@ -326,6 +340,11 @@ static struct rdac_controller *get_contr
>  	memcpy(ctlr->slot_id, slot_id, SLOT_ID_LEN);
>  	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);
> @@ -445,8 +464,7 @@ static int set_mode_select(struct scsi_d
>  	return err;
>  }
> 
> -static int mode_select_handle_sense(struct scsi_device *sdev,
> -				    unsigned char *sensebuf)
> +static int mode_select_handle_sense(unsigned char *sensebuf)
>  {
>  	struct scsi_sense_hdr sense_hdr;
>  	int err = SCSI_DH_IO, ret;
> @@ -478,7 +496,7 @@ static int mode_select_handle_sense(stru
>  			err = SCSI_DH_RETRY;
>  		break;
>  	default:
> -		sdev_printk(KERN_INFO, sdev,
> +		printk(KERN_INFO
>  			    "MODE_SELECT failed with sense %02x/%02x/%02x.\n",
>  			    sense_hdr.sense_key, sense_hdr.asc, sense_hdr.ascq);
>  	}
> @@ -487,11 +505,29 @@ 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;
> @@ -499,13 +535,17 @@ retry:
>  	if (!rq)
>  		goto done;
> 
> -	sdev_printk(KERN_INFO, sdev, "%s MODE_SELECT command.\n",
> + 	list_for_each_entry(qdata, &list, entry) {
> +		lun_table[qdata->h->lun] = 0x81;
> +	}
> +
> +	printk(KERN_INFO "%s MODE_SELECT command.\n",
>  		(retry_cnt == RDAC_RETRY_COUNT) ? "queueing" : "retrying");
> 
>  	err = blk_execute_rq(q, NULL, rq, 1);
>  	blk_put_request(rq);
>  	if (err != SCSI_DH_OK) {
> -		err = mode_select_handle_sense(sdev, h->sense);
> +		err = mode_select_handle_sense(h->sense);
>  		if (err == SCSI_DH_RETRY && retry_cnt--)
>  			goto retry;
>  	}
> @@ -513,10 +553,45 @@ retry:
>  		h->state = RDAC_STATE_ACTIVE;
> 
>  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 rdac_activate(struct scsi_device *sdev, activate_complete fn,
> void *data)
> +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,
> +				activate_complete fn, void *data)
>  {
>  	struct rdac_dh_data *h = get_rdac_data(sdev);
>  	int err = SCSI_DH_OK;
> @@ -536,8 +611,11 @@ static int rdac_activate(struct scsi_dev
>  		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);
> @@ -720,13 +798,26 @@ 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);
>  }
> 
> --
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