dcssblk.c

linux-2.6.15.6

/*
 * dcssblk.c -- the S/390 block driver for dcss memory
 *
 * Authors: Carsten Otte, Stefan Weinhuber, Gerald Schaefer
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <asm/extmem.h>
#include <asm/io.h>
#include <linux/completion.h>
#include <linux/interrupt.h>
#include <asm/ccwdev.h> 	// for s390_root_dev_(un)register()

//#define DCSSBLK_DEBUG		/* Debug messages on/off */
#define DCSSBLK_NAME "dcssblk"
#define DCSSBLK_MINORS_PER_DISK 1
#define DCSSBLK_PARM_LEN 400

#ifdef DCSSBLK_DEBUG
#define PRINT_DEBUG(x...) printk(KERN_DEBUG DCSSBLK_NAME " debug: " x)
#else
#define PRINT_DEBUG(x...) do {} while (0)
#endif
#define PRINT_INFO(x...)  printk(KERN_INFO DCSSBLK_NAME " info: " x)
#define PRINT_WARN(x...)  printk(KERN_WARNING DCSSBLK_NAME " warning: " x)
#define PRINT_ERR(x...)	  printk(KERN_ERR DCSSBLK_NAME " error: " x)


static int dcssblk_open(struct inode *inode, struct file *filp);
static int dcssblk_release(struct inode *inode, struct file *filp);
static int dcssblk_make_request(struct request_queue *q, struct bio *bio);
static int dcssblk_direct_access(struct block_device *bdev, sector_t secnum,
				 unsigned long *data);

static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";

static int dcssblk_major;
static struct block_device_operations dcssblk_devops = {
	.owner   	= THIS_MODULE,
	.open    	= dcssblk_open,
	.release 	= dcssblk_release,
	.direct_access 	= dcssblk_direct_access,
};

static ssize_t dcssblk_add_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);
static ssize_t dcssblk_remove_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);
static ssize_t dcssblk_save_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);
static ssize_t dcssblk_save_show(struct device *dev, struct device_attribute *attr, char *buf);
static ssize_t dcssblk_shared_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);
static ssize_t dcssblk_shared_show(struct device *dev, struct device_attribute *attr, char *buf);

static DEVICE_ATTR(add, S_IWUSR, NULL, dcssblk_add_store);
static DEVICE_ATTR(remove, S_IWUSR, NULL, dcssblk_remove_store);
static DEVICE_ATTR(save, S_IWUSR | S_IRUGO, dcssblk_save_show,
		   dcssblk_save_store);
static DEVICE_ATTR(shared, S_IWUSR | S_IRUGO, dcssblk_shared_show,
		   dcssblk_shared_store);

static struct device *dcssblk_root_dev;

struct dcssblk_dev_info {
	struct list_head lh;
	struct device dev;
	char segment_name[BUS_ID_SIZE];
	atomic_t use_count;
	struct gendisk *gd;
	unsigned long start;
	unsigned long end;
	int segment_type;
	unsigned char save_pending;
	unsigned char is_shared;
	struct request_queue *dcssblk_queue;
};

static struct list_head dcssblk_devices = LIST_HEAD_INIT(dcssblk_devices);
static struct rw_semaphore dcssblk_devices_sem;

/*
 * release function for segment device.
 */
static void
dcssblk_release_segment(struct device *dev)
{
	PRINT_DEBUG("segment release fn called for %s\n", dev->bus_id);
	kfree(container_of(dev, struct dcssblk_dev_info, dev));
	module_put(THIS_MODULE);
}

/*
 * get a minor number. needs to be called with
 * down_write(&dcssblk_devices_sem) and the
 * device needs to be enqueued before the semaphore is
 * freed.
 */
static inline int
dcssblk_assign_free_minor(struct dcssblk_dev_info *dev_info)
{
	int minor, found;
	struct dcssblk_dev_info *entry;

	if (dev_info == NULL)
		return -EINVAL;
	for (minor = 0; minor < (1<<MINORBITS); minor++) {
		found = 0;
		// test if minor available
		list_for_each_entry(entry, &dcssblk_devices, lh)
			if (minor == entry->gd->first_minor)
				found++;
		if (!found) break; // got unused minor
	}
	if (found)
		return -EBUSY;
	dev_info->gd->first_minor = minor;
	return 0;
}

/*
 * get the struct dcssblk_dev_info from dcssblk_devices
 * for the given name.
 * down_read(&dcssblk_devices_sem) must be held.
 */
static struct dcssblk_dev_info *
dcssblk_get_device_by_name(char *name)
{
	struct dcssblk_dev_info *entry;

	list_for_each_entry(entry, &dcssblk_devices, lh) {
		if (!strcmp(name, entry->segment_name)) {
			return entry;
		}
	}
	return NULL;
}

/*
 * print appropriate error message for segment_load()/segment_type()
 * return code
 */
static void
dcssblk_segment_warn(int rc, char* seg_name)
{
	switch (rc) {
	case -ENOENT:
		PRINT_WARN("cannot load/query segment %s, does not exist\n",
			   seg_name);
		break;
	case -ENOSYS:
		PRINT_WARN("cannot load/query segment %s, not running on VM\n",
			   seg_name);
		break;
	case -EIO:
		PRINT_WARN("cannot load/query segment %s, hardware error\n",
			   seg_name);
		break;
	case -ENOTSUPP:
		PRINT_WARN("cannot load/query segment %s, is a multi-part "
			   "segment\n", seg_name);
		break;
	case -ENOSPC:
		PRINT_WARN("cannot load/query segment %s, overlaps with "
			   "storage\n", seg_name);
		break;
	case -EBUSY:
		PRINT_WARN("cannot load/query segment %s, overlaps with "
			   "already loaded dcss\n", seg_name);
		break;
	case -EPERM:
		PRINT_WARN("cannot load/query segment %s, already loaded in "
			   "incompatible mode\n", seg_name);
		break;
	case -ENOMEM:
		PRINT_WARN("cannot load/query segment %s, out of memory\n",
			   seg_name);
		break;
	case -ERANGE:
		PRINT_WARN("cannot load/query segment %s, exceeds kernel "
			   "mapping range\n", seg_name);
		break;
	default:
		PRINT_WARN("cannot load/query segment %s, return value %i\n",
			   seg_name, rc);
		break;
	}
}

/*
 * device attribute for switching shared/nonshared (exclusive)
 * operation (show + store)
 */
static ssize_t
dcssblk_shared_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct dcssblk_dev_info *dev_info;

	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
	return sprintf(buf, dev_info->is_shared ? "1\n" : "0\n");
}

static ssize_t
dcssblk_shared_store(struct device *dev, struct device_attribute *attr, const char *inbuf, size_t count)
{
	struct dcssblk_dev_info *dev_info;
	int rc;

	if ((count > 1) && (inbuf[1] != '\n') && (inbuf[1] != '\0')) {
		PRINT_WARN("Invalid value, must be 0 or 1\n");
		return -EINVAL;
	}
	down_write(&dcssblk_devices_sem);
	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
	if (atomic_read(&dev_info->use_count)) {
		PRINT_ERR("share: segment %s is busy!\n",
			  dev_info->segment_name);
		rc = -EBUSY;
		goto out;
	}
	if (inbuf[0] == '1') {
		// reload segment in shared mode
		rc = segment_modify_shared(dev_info->segment_name,
					   SEGMENT_SHARED);
		if (rc < 0) {
			BUG_ON(rc == -EINVAL);
			if (rc == -EIO || rc == -ENOENT)
				goto removeseg;
		} else {
			dev_info->is_shared = 1;
			switch (dev_info->segment_type) {
				case SEG_TYPE_SR:
				case SEG_TYPE_ER:
				case SEG_TYPE_SC:
					set_disk_ro(dev_info->gd,1);
			}
		}
	} else if (inbuf[0] == '0') {
		// reload segment in exclusive mode
		if (dev_info->segment_type == SEG_TYPE_SC) {
			PRINT_ERR("Segment type SC (%s) cannot be loaded in "
				  "non-shared mode\n", dev_info->segment_name);
			rc = -EINVAL;
			goto out;
		}
		rc = segment_modify_shared(dev_info->segment_name,
					   SEGMENT_EXCLUSIVE);
		if (rc < 0) {
			BUG_ON(rc == -EINVAL);
			if (rc == -EIO || rc == -ENOENT)
				goto removeseg;
		} else {
			dev_info->is_shared = 0;
			set_disk_ro(dev_info->gd, 0);
		}
	} else {
		PRINT_WARN("Invalid value, must be 0 or 1\n");
		rc = -EINVAL;
		goto out;
	}
	rc = count;
	goto out;

removeseg:
	PRINT_ERR("Could not reload segment %s, removing it now!\n",
			dev_info->segment_name);
	list_del(&dev_info->lh);

	del_gendisk(dev_info->gd);
	blk_put_queue(dev_info->dcssblk_queue);
	dev_info->gd->queue = NULL;
	put_disk(dev_info->gd);
	device_unregister(dev);
	put_device(dev);
out:
	up_write(&dcssblk_devices_sem);
	return rc;
}

/*
 * device attribute for save operation on current copy
 * of the segment. If the segment is busy, saving will
 * become pending until it gets released, which can be
 * undone by storing a non-true value to this entry.
 * (show + store)
 */
static ssize_t
dcssblk_save_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct dcssblk_dev_info *dev_info;

	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
	return sprintf(buf, dev_info->save_pending ? "1\n" : "0\n");
}

static ssize_t
dcssblk_save_store(struct device *dev, struct device_attribute *attr, const char *inbuf, size_t count)
{
	struct dcssblk_dev_info *dev_info;

	if ((count > 1) && (inbuf[1] != '\n') && (inbuf[1] != '\0')) {
		PRINT_WARN("Invalid value, must be 0 or 1\n");
		return -EINVAL;
	}
	dev_info = container_of(dev, struct dcssblk_dev_info, dev);

	down_write(&dcssblk_devices_sem);
	if (inbuf[0] == '1') {
		if (atomic_read(&dev_info->use_count) == 0) {
			// device is idle => we save immediately
			PRINT_INFO("Saving segment %s\n",
				   dev_info->segment_name);
			segment_save(dev_info->segment_name);
		}  else {
			// device is busy => we save it when it becomes
			// idle in dcssblk_release
			PRINT_INFO("Segment %s is currently busy, it will "
				   "be saved when it becomes idle...\n",
				   dev_info->segment_name);
			dev_info->save_pending = 1;
		}
	} else if (inbuf[0] == '0') {
		if (dev_info->save_pending) {
			// device is busy & the user wants to undo his save
			// request
			dev_info->save_pending = 0;
			PRINT_INFO("Pending save for segment %s deactivated\n",
					dev_info->segment_name);
		}
	} else {
		up_write(&dcssblk_devices_sem);
		PRINT_WARN("Invalid value, must be 0 or 1\n");
		return -EINVAL;
	}
	up_write(&dcssblk_devices_sem);
	return count;
}

/*
 * device attribute for adding devices
 */
static ssize_t
dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
	int rc, i;
	struct dcssblk_dev_info *dev_info;
	char *local_buf;
	unsigned long seg_byte_size;

	dev_info = NULL;
	if (dev != dcssblk_root_dev) {
		rc = -EINVAL;
		goto out_nobuf;
	}
	local_buf = kmalloc(count + 1, GFP_KERNEL);
	if (local_buf == NULL) {
		rc = -ENOMEM;
		goto out_nobuf;
	}
	/*
	 * parse input
	 */
	for (i = 0; ((buf[i] != '\0') && (buf[i] != '\n') && i < count); i++) {
		local_buf[i] = toupper(buf[i]);
	}
	local_buf[i] = '\0';
	if ((i == 0) || (i > 8)) {
		rc = -ENAMETOOLONG;
		goto out;
	}
	/*
	 * already loaded?
	 */
	down_read(&dcssblk_devices_sem);
	dev_info = dcssblk_get_device_by_name(local_buf);
	up_read(&dcssblk_devices_sem);
	if (dev_info != NULL) {
		PRINT_WARN("Segment %s already loaded!\n", local_buf);
		rc = -EEXIST;
		goto out;
	}
	/*
	 * get a struct dcssblk_dev_info
	 */
	dev_info = kmalloc(sizeof(struct dcssblk_dev_info), GFP_KERNEL);
	if (dev_info == NULL) {
		rc = -ENOMEM;
		goto out;
	}
	memset(dev_info, 0, sizeof(struct dcssblk_dev_info));

	strcpy(dev_info->segment_name, local_buf);
	strlcpy(dev_info->dev.bus_id, local_buf, BUS_ID_SIZE);
	dev_info->dev.release = dcssblk_release_segment;
	INIT_LIST_HEAD(&dev_info->lh);

	dev_info->gd = alloc_disk(DCSSBLK_MINORS_PER_DISK);
	if (dev_info->gd == NULL) {
		rc = -ENOMEM;
		goto free_dev_info;