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Commit a6a8d9f8 authored by Chandra Seetharaman's avatar Chandra Seetharaman Committed by James Bottomley
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[SCSI] scsi_dh: add infrastructure for SCSI Device Handlers 



Some of the storage devices (that can be accessed through multiple paths),
do need some special handling for
	1. Activating the passive path of the storage access.
	2. Decode and handle the special sense codes returned by the devices.
	3. Handle the I/Os being sent to the passive path, especially
           during the device probe time.
when accessed through multiple paths.

As of today this special device handling is done at the dm-multipath
layer using dm-handlers. That works well for (1); for (2) to be handled
at dm layer, scsi sense information need to be exported from SCSI to dm-layer,
which is not very attractive; (3) cannot be done at all at the dm layer.

Device handler has been moved to SCSI mainly to handle (2) and (3) properly.

Signed-off-by: default avatarChandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: default avatarMike Anderson <andmike@linux.vnet.ibm.com>
Signed-off-by: default avatarMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
parent 53c8ba95

drivers/scsi/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -1771,4 +1771,6 @@ endif # SCSI_LOWLEVEL 


source "drivers/scsi/pcmcia/Kconfig"



source "drivers/scsi/device_handler/Kconfig"



endmenu

drivers/scsi/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ obj-$(CONFIG_SCSI_ISCSI_ATTRS) += scsi_transport_iscsi.o 
obj-$(CONFIG_SCSI_SAS_ATTRS)	+= scsi_transport_sas.o

obj-$(CONFIG_SCSI_SAS_LIBSAS)	+= libsas/

obj-$(CONFIG_SCSI_SRP_ATTRS)	+= scsi_transport_srp.o

obj-$(CONFIG_SCSI_DH)		+= device_handler/



obj-$(CONFIG_ISCSI_TCP) 	+= libiscsi.o	iscsi_tcp.o

obj-$(CONFIG_INFINIBAND_ISER) 	+= libiscsi.o

drivers/scsi/device_handler/Kconfig

0 → 100644
+12 −0
Original line number Diff line number Diff line 
#

# SCSI Device Handler configuration

#



menuconfig SCSI_DH

	tristate "SCSI Device Handlers"

	depends on SCSI

	default n

	help

	  SCSI Device Handlers provide device specific support for

	  devices utilized in multipath configurations. Say Y here to

	  select support for specific hardware.

drivers/scsi/device_handler/Makefile

0 → 100644
+4 −0
Original line number Diff line number Diff line 
#

# SCSI Device Handler

#

obj-$(CONFIG_SCSI_DH)		+= scsi_dh.o

drivers/scsi/device_handler/scsi_dh.c

0 → 100644
+162 −0
Original line number Diff line number Diff line 
/*

 * SCSI device handler infrastruture.

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License as published by the

 * Free Software Foundation; either version 2 of the License, or (at your

 * option) any later version.

 *

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License along

 * with this program; if not, write to the Free Software Foundation, Inc.,

 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

 *

 * Copyright IBM Corporation, 2007

 *      Authors:

 *               Chandra Seetharaman <sekharan@us.ibm.com>

 *               Mike Anderson <andmike@linux.vnet.ibm.com>

 */



#include <scsi/scsi_dh.h>

#include "../scsi_priv.h"



static DEFINE_SPINLOCK(list_lock);

static LIST_HEAD(scsi_dh_list);



static struct scsi_device_handler *get_device_handler(const char *name)

{

	struct scsi_device_handler *tmp, *found = NULL;



	spin_lock(&list_lock);

	list_for_each_entry(tmp, &scsi_dh_list, list) {

		if (!strcmp(tmp->name, name)) {

			found = tmp;

			break;

		}

	}

	spin_unlock(&list_lock);

	return found;

}



static int scsi_dh_notifier_add(struct device *dev, void *data)

{

	struct scsi_device_handler *scsi_dh = data;



	scsi_dh->nb.notifier_call(&scsi_dh->nb, BUS_NOTIFY_ADD_DEVICE, dev);

	return 0;

}



/*

 * scsi_register_device_handler - register a device handler personality

 *      module.

 * @scsi_dh - device handler to be registered.

 *

 * Returns 0 on success, -EBUSY if handler already registered.

 */

int scsi_register_device_handler(struct scsi_device_handler *scsi_dh)

{

	int ret = -EBUSY;

	struct scsi_device_handler *tmp;



	tmp = get_device_handler(scsi_dh->name);

	if (tmp)

		goto done;



	ret = bus_register_notifier(&scsi_bus_type, &scsi_dh->nb);



	bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh, scsi_dh_notifier_add);

	spin_lock(&list_lock);

	list_add(&scsi_dh->list, &scsi_dh_list);

	spin_unlock(&list_lock);



done:

	return ret;

}

EXPORT_SYMBOL_GPL(scsi_register_device_handler);



static int scsi_dh_notifier_remove(struct device *dev, void *data)

{

	struct scsi_device_handler *scsi_dh = data;



	scsi_dh->nb.notifier_call(&scsi_dh->nb, BUS_NOTIFY_DEL_DEVICE, dev);

	return 0;

}



/*

 * scsi_unregister_device_handler - register a device handler personality

 *      module.

 * @scsi_dh - device handler to be unregistered.

 *

 * Returns 0 on success, -ENODEV if handler not registered.

 */

int scsi_unregister_device_handler(struct scsi_device_handler *scsi_dh)

{

	int ret = -ENODEV;

	struct scsi_device_handler *tmp;



	tmp = get_device_handler(scsi_dh->name);

	if (!tmp)

		goto done;



	ret = bus_unregister_notifier(&scsi_bus_type, &scsi_dh->nb);



	bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh,

					scsi_dh_notifier_remove);

	spin_lock(&list_lock);

	list_del(&scsi_dh->list);

	spin_unlock(&list_lock);



done:

	return ret;

}

EXPORT_SYMBOL_GPL(scsi_unregister_device_handler);



/*

 * scsi_dh_activate - activate the path associated with the scsi_device

 *      corresponding to the given request queue.

 * @q - Request queue that is associated with the scsi_device to be

 *      activated.

 */

int scsi_dh_activate(struct request_queue *q)

{

	int err = 0;

	unsigned long flags;

	struct scsi_device *sdev;

	struct scsi_device_handler *scsi_dh = NULL;



	spin_lock_irqsave(q->queue_lock, flags);

	sdev = q->queuedata;

	if (sdev && sdev->scsi_dh_data)

		scsi_dh = sdev->scsi_dh_data->scsi_dh;

	if (!scsi_dh || !get_device(&sdev->sdev_gendev))

		err = SCSI_DH_NOSYS;

	spin_unlock_irqrestore(q->queue_lock, flags);



	if (err)

		return err;



	if (scsi_dh->activate)

		err = scsi_dh->activate(sdev);

	put_device(&sdev->sdev_gendev);

	return err;

}

EXPORT_SYMBOL_GPL(scsi_dh_activate);



/*

 * scsi_dh_handler_exist - Return TRUE(1) if a device handler exists for

 *	the given name. FALSE(0) otherwise.

 * @name - name of the device handler.

 */

int scsi_dh_handler_exist(const char *name)

{

	return (get_device_handler(name) != NULL);

}

EXPORT_SYMBOL_GPL(scsi_dh_handler_exist);



MODULE_DESCRIPTION("SCSI device handler");

MODULE_AUTHOR("Chandra Seetharaman <sekharan@us.ibm.com>");

MODULE_LICENSE("GPL");