scsi_scan.c

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/*
 * scsi_scan.c
 *
 * Copyright (C) 2000 Eric Youngdale,
 * Copyright (C) 2002 Patrick Mansfield
 *
 * The general scanning/probing algorithm is as follows, exceptions are
 * made to it depending on device specific flags, compilation options, and
 * global variable (boot or module load time) settings.
 *
 * A specific LUN is scanned via an INQUIRY command; if the LUN has a
 * device attached, a scsi_device is allocated and setup for it.
 *
 * For every id of every channel on the given host:
 *
 * 	Scan LUN 0; if the target responds to LUN 0 (even if there is no
 * 	device or storage attached to LUN 0):
 *
 * 		If LUN 0 has a device attached, allocate and setup a
 * 		scsi_device for it.
 *
 * 		If target is SCSI-3 or up, issue a REPORT LUN, and scan
 * 		all of the LUNs returned by the REPORT LUN; else,
 * 		sequentially scan LUNs up until some maximum is reached,
 * 		or a LUN is seen that cannot have a device attached to it.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/spinlock.h>

#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_driver.h>
#include <scsi/scsi_devinfo.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_transport.h>
#include <scsi/scsi_eh.h>

#include "scsi_priv.h"
#include "scsi_logging.h"

#define ALLOC_FAILURE_MSG	KERN_ERR "%s: Allocation failure during" \
	" SCSI scanning, some SCSI devices might not be configured\n"

/*
 * Default timeout
 */
#define SCSI_TIMEOUT (2*HZ)

/*
 * Prefix values for the SCSI id's (stored in sysfs name field)
 */
#define SCSI_UID_SER_NUM 'S'
#define SCSI_UID_UNKNOWN 'Z'

/*
 * Return values of some of the scanning functions.
 *
 * SCSI_SCAN_NO_RESPONSE: no valid response received from the target, this
 * includes allocation or general failures preventing IO from being sent.
 *
 * SCSI_SCAN_TARGET_PRESENT: target responded, but no device is available
 * on the given LUN.
 *
 * SCSI_SCAN_LUN_PRESENT: target responded, and a device is available on a
 * given LUN.
 */
#define SCSI_SCAN_NO_RESPONSE		0
#define SCSI_SCAN_TARGET_PRESENT	1
#define SCSI_SCAN_LUN_PRESENT		2

static const char *scsi_null_device_strs = "nullnullnullnull";

#define MAX_SCSI_LUNS	512

#ifdef CONFIG_SCSI_MULTI_LUN
static unsigned int max_scsi_luns = MAX_SCSI_LUNS;
#else
static unsigned int max_scsi_luns = 1;
#endif

module_param_named(max_luns, max_scsi_luns, uint, S_IRUGO|S_IWUSR);
MODULE_PARM_DESC(max_luns,
		 "last scsi LUN (should be between 1 and 2^32-1)");

#ifdef CONFIG_SCSI_SCAN_ASYNC
#define SCSI_SCAN_TYPE_DEFAULT "async"
#else
#define SCSI_SCAN_TYPE_DEFAULT "sync"
#endif

static char scsi_scan_type[6] = SCSI_SCAN_TYPE_DEFAULT;

module_param_string(scan, scsi_scan_type, sizeof(scsi_scan_type), S_IRUGO);
MODULE_PARM_DESC(scan, "sync, async or none");

/*
 * max_scsi_report_luns: the maximum number of LUNS that will be
 * returned from the REPORT LUNS command. 8 times this value must
 * be allocated. In theory this could be up to an 8 byte value, but
 * in practice, the maximum number of LUNs suppored by any device
 * is about 16k.
 */
static unsigned int max_scsi_report_luns = 511;

module_param_named(max_report_luns, max_scsi_report_luns, uint, S_IRUGO|S_IWUSR);
MODULE_PARM_DESC(max_report_luns,
		 "REPORT LUNS maximum number of LUNS received (should be"
		 " between 1 and 16384)");

static unsigned int scsi_inq_timeout = SCSI_TIMEOUT/HZ+3;

module_param_named(inq_timeout, scsi_inq_timeout, uint, S_IRUGO|S_IWUSR);
MODULE_PARM_DESC(inq_timeout, 
		 "Timeout (in seconds) waiting for devices to answer INQUIRY."
		 " Default is 5. Some non-compliant devices need more.");

/* This lock protects only this list */
static DEFINE_SPINLOCK(async_scan_lock);
static LIST_HEAD(scanning_hosts);

struct async_scan_data {
	struct list_head list;
	struct Scsi_Host *shost;
	struct completion prev_finished;
};

/**
 * scsi_complete_async_scans - Wait for asynchronous scans to complete
 *
 * When this function returns, any host which started scanning before
 * this function was called will have finished its scan.  Hosts which
 * started scanning after this function was called may or may not have
 * finished.
 */
int scsi_complete_async_scans(void)
{
	struct async_scan_data *data;

	do {
		if (list_empty(&scanning_hosts))
			return 0;
		/* If we can't get memory immediately, that's OK.  Just
		 * sleep a little.  Even if we never get memory, the async
		 * scans will finish eventually.
		 */
		data = kmalloc(sizeof(*data), GFP_KERNEL);
		if (!data)
			msleep(1);
	} while (!data);

	data->shost = NULL;
	init_completion(&data->prev_finished);

	spin_lock(&async_scan_lock);
	/* Check that there's still somebody else on the list */
	if (list_empty(&scanning_hosts))
		goto done;
	list_add_tail(&data->list, &scanning_hosts);
	spin_unlock(&async_scan_lock);

	printk(KERN_INFO "scsi: waiting for bus probes to complete ...\n");
	wait_for_completion(&data->prev_finished);

	spin_lock(&async_scan_lock);
	list_del(&data->list);
	if (!list_empty(&scanning_hosts)) {
		struct async_scan_data *next = list_entry(scanning_hosts.next,
				struct async_scan_data, list);
		complete(&next->prev_finished);
	}
 done:
	spin_unlock(&async_scan_lock);

	kfree(data);
	return 0;
}

/* Only exported for the benefit of scsi_wait_scan */
EXPORT_SYMBOL_GPL(scsi_complete_async_scans);

#ifndef MODULE
/*
 * For async scanning we need to wait for all the scans to complete before
 * trying to mount the root fs.  Otherwise non-modular drivers may not be ready
 * yet.
 */
late_initcall(scsi_complete_async_scans);
#endif

/**
 * scsi_unlock_floptical - unlock device via a special MODE SENSE command
 * @sdev:	scsi device to send command to
 * @result:	area to store the result of the MODE SENSE
 *
 * Description:
 *     Send a vendor specific MODE SENSE (not a MODE SELECT) command.
 *     Called for BLIST_KEY devices.
 **/
static void scsi_unlock_floptical(struct scsi_device *sdev,
				  unsigned char *result)
{
	unsigned char scsi_cmd[MAX_COMMAND_SIZE];

	printk(KERN_NOTICE "scsi: unlocking floptical drive\n");
	scsi_cmd[0] = MODE_SENSE;
	scsi_cmd[1] = 0;
	scsi_cmd[2] = 0x2e;
	scsi_cmd[3] = 0;
	scsi_cmd[4] = 0x2a;     /* size */
	scsi_cmd[5] = 0;
	scsi_execute_req(sdev, scsi_cmd, DMA_FROM_DEVICE, result, 0x2a, NULL,
			 SCSI_TIMEOUT, 3);
}

/**
 * scsi_alloc_sdev - allocate and setup a scsi_Device
 *
 * Description:
 *     Allocate, initialize for io, and return a pointer to a scsi_Device.
 *     Stores the @shost, @channel, @id, and @lun in the scsi_Device, and
 *     adds scsi_Device to the appropriate list.
 *
 * Return value:
 *     scsi_Device pointer, or NULL on failure.
 **/
static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
					   unsigned int lun, void *hostdata)
{
	struct scsi_device *sdev;
	int display_failure_msg = 1, ret;
	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
	extern void scsi_evt_thread(struct work_struct *work);

	sdev = kzalloc(sizeof(*sdev) + shost->transportt->device_size,
		       GFP_ATOMIC);
	if (!sdev)
		goto out;

	sdev->vendor = scsi_null_device_strs;
	sdev->model = scsi_null_device_strs;
	sdev->rev = scsi_null_device_strs;
	sdev->host = shost;
	sdev->id = starget->id;
	sdev->lun = lun;
	sdev->channel = starget->channel;
	sdev->sdev_state = SDEV_CREATED;
	INIT_LIST_HEAD(&sdev->siblings);
	INIT_LIST_HEAD(&sdev->same_target_siblings);
	INIT_LIST_HEAD(&sdev->cmd_list);
	INIT_LIST_HEAD(&sdev->starved_entry);
	INIT_LIST_HEAD(&sdev->event_list);
	spin_lock_init(&sdev->list_lock);
	INIT_WORK(&sdev->event_work, scsi_evt_thread);

	sdev->sdev_gendev.parent = get_device(&starget->dev);
	sdev->sdev_target = starget;

	/* usually NULL and set by ->slave_alloc instead */
	sdev->hostdata = hostdata;

	/* if the device needs this changing, it may do so in the
	 * slave_configure function */
	sdev->max_device_blocked = SCSI_DEFAULT_DEVICE_BLOCKED;

	/*
	 * Some low level driver could use device->type
	 */
	sdev->type = -1;

	/*
	 * Assume that the device will have handshaking problems,
	 * and then fix this field later if it turns out it
	 * doesn't
	 */
	sdev->borken = 1;

	sdev->request_queue = scsi_alloc_queue(sdev);
	if (!sdev->request_queue) {
		/* release fn is set up in scsi_sysfs_device_initialise, so
		 * have to free and put manually here */
		put_device(&starget->dev);
		kfree(sdev);
		goto out;
	}

	sdev->request_queue->queuedata = sdev;
	scsi_adjust_queue_depth(sdev, 0, sdev->host->cmd_per_lun);

	scsi_sysfs_device_initialize(sdev);

	if (shost->hostt->slave_alloc) {
		ret = shost->hostt->slave_alloc(sdev);
		if (ret) {
			/*
			 * if LLDD reports slave not present, don't clutter
			 * console with alloc failure messages
			 */
			if (ret == -ENXIO)
				display_failure_msg = 0;
			goto out_device_destroy;
		}
	}

	return sdev;

out_device_destroy:
	transport_destroy_device(&sdev->sdev_gendev);
	put_device(&sdev->sdev_gendev);
out:
	if (display_failure_msg)
		printk(ALLOC_FAILURE_MSG, __FUNCTION__);
	return NULL;
}

static void scsi_target_dev_release(struct device *dev)
{
	struct device *parent = dev->parent;
	struct scsi_target *starget = to_scsi_target(dev);

	kfree(starget);
	put_device(parent);
}

int scsi_is_target_device(const struct device *dev)
{
	return dev->release == scsi_target_dev_release;
}
EXPORT_SYMBOL(scsi_is_target_device);

static struct scsi_target *__scsi_find_target(struct device *parent,
					      int channel, uint id)
{
	struct scsi_target *starget, *found_starget = NULL;
	struct Scsi_Host *shost = dev_to_shost(parent);
	/*
	 * Search for an existing target for this sdev.
	 */
	list_for_each_entry(starget, &shost->__targets, siblings) {
		if (starget->id == id &&
		    starget->channel == channel) {
			found_starget = starget;
			break;
		}
	}
	if (found_starget)
		get_device(&found_starget->dev);

	return found_starget;
}

/**
 * scsi_alloc_target - allocate a new or find an existing target
 * @parent:	parent of the target (need not be a scsi host)
 * @channel:	target channel number (zero if no channels)
 * @id:		target id number
 *
 * Return an existing target if one exists, provided it hasn't already
 * gone into STARGET_DEL state, otherwise allocate a new target.
 *
 * The target is returned with an incremented reference, so the caller
 * is responsible for both reaping and doing a last put
 */
static struct scsi_target *scsi_alloc_target(struct device *parent,
					     int channel, uint id)
{
	struct Scsi_Host *shost = dev_to_shost(parent);
	struct device *dev = NULL;
	unsigned long flags;
	const int size = sizeof(struct scsi_target)
		+ shost->transportt->target_size;
	struct scsi_target *starget;
	struct scsi_target *found_target;
	int error;

	starget = kzalloc(size, GFP_KERNEL);
	if (!starget) {
		printk(KERN_ERR "%s: allocation failure\n", __FUNCTION__);
		return NULL;
	}
	dev = &starget->dev;
	device_initialize(dev);
	starget->reap_ref = 1;
	dev->parent = get_device(parent);
	dev->release = scsi_target_dev_release;
	sprintf(dev->bus_id, "target%d:%d:%d",
		shost->host_no, channel, id);
	starget->id = id;
	starget->channel = channel;
	INIT_LIST_HEAD(&starget->siblings);
	INIT_LIST_HEAD(&starget->devices);
	starget->state = STARGET_RUNNING;
	starget->scsi_level = SCSI_2;
 retry:
	spin_lock_irqsave(shost->host_lock, flags);

	found_target = __scsi_find_target(parent, channel, id);
	if (found_target)
		goto found;

	list_add_tail(&starget->siblings, &shost->__targets);
	spin_unlock_irqrestore(shost->host_lock, flags);
	/* allocate and add */
	transport_setup_device(dev);
	error = device_add(dev);
	if (error) {
		dev_err(dev, "target device_add failed, error %d\n", error);
		spin_lock_irqsave(shost->host_lock, flags);
		list_del_init(&starget->siblings);
		spin_unlock_irqrestore(shost->host_lock, flags);
		transport_destroy_device(dev);
		put_device(parent);
		kfree(starget);
		return NULL;
	}
	transport_add_device(dev);
	if (shost->hostt->target_alloc) {
		error = shost->hostt->target_alloc(starget);

		if(error) {
			dev_printk(KERN_ERR, dev, "target allocation failed, error %d\n", error);
			/* don't want scsi_target_reap to do the final
			 * put because it will be under the host lock */
			get_device(dev);
			scsi_target_reap(starget);
			put_device(dev);
			return NULL;
		}
	}
	get_device(dev);

	return starget;

 found:
	found_target->reap_ref++;
	spin_unlock_irqrestore(shost->host_lock, flags);
	if (found_target->state != STARGET_DEL) {
		put_device(parent);
		kfree(starget);
		return found_target;
	}
	/* Unfortunately, we found a dying target; need to
	 * wait until it's dead before we can get a new one */
	put_device(&found_target->dev);
	flush_scheduled_work();
	goto retry;
}

static void scsi_target_reap_usercontext(struct work_struct *work)
{
	struct scsi_target *starget =
		container_of(work, struct scsi_target, ew.work);
	struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
	unsigned long flags;

	transport_remove_device(&starget->dev);
	device_del(&starget->dev);
	transport_destroy_device(&starget->dev);
	spin_lock_irqsave(shost->host_lock, flags);
	if (shost->hostt->target_destroy)
		shost->hostt->target_destroy(starget);
	list_del_init(&starget->siblings);
	spin_unlock_irqrestore(shost->host_lock, flags);
	put_device(&starget->dev);
}

/**
 * scsi_target_reap - check to see if target is in use and destroy if not
 *
 * @starget: target to be checked
 *