OSCL-LXR linux-6.0.1/​drivers/​s390/​block/​dasd_eer.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  *  Character device driver for extended error reporting.
  *
  *  Copyright IBM Corp. 2005
  *  extended error reporting for DASD ECKD devices
  *  Author(s): Stefan Weinhuber <wein@de.ibm.com>
  */
 
 #define KMSG_COMPONENT "dasd-eckd"
 
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/kernel.h>
 #include <linux/miscdevice.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/device.h>
 #include <linux/poll.h>
 #include <linux/mutex.h>
 #include <linux/err.h>
 #include <linux/slab.h>
 
 #include <linux/uaccess.h>
 #include <linux/atomic.h>
 #include <asm/ebcdic.h>
 
 #include "dasd_int.h"
 #include "dasd_eckd.h"
 
 #ifdef PRINTK_HEADER
 #undef PRINTK_HEADER
 #endif              /* PRINTK_HEADER */
 #define PRINTK_HEADER "dasd(eer):"
 
 /*
  * SECTION: the internal buffer
  */
 
 /*
  * The internal buffer is meant to store obaque blobs of data, so it does
  * not know of higher level concepts like triggers.
  * It consists of a number of pages that are used as a ringbuffer. Each data
  * blob is stored in a simple record that consists of an integer, which
  * contains the size of the following data, and the data bytes themselfes.
  *
  * To allow for multiple independent readers we create one internal buffer
  * each time the device is opened and destroy the buffer when the file is
  * closed again. The number of pages used for this buffer is determined by
  * the module parmeter eer_pages.
  *
  * One record can be written to a buffer by using the functions
  * - dasd_eer_start_record (one time per record to write the size to the
  *                          buffer and reserve the space for the data)
  * - dasd_eer_write_buffer (one or more times per record to write the data)
  * The data can be written in several steps but you will have to compute
  * the total size up front for the invocation of dasd_eer_start_record.
  * If the ringbuffer is full, dasd_eer_start_record will remove the required
  * number of old records.
  *
  * A record is typically read in two steps, first read the integer that
  * specifies the size of the following data, then read the data.
  * Both can be done by
  * - dasd_eer_read_buffer
  *
  * For all mentioned functions you need to get the bufferlock first and keep
  * it until a complete record is written or read.
  *
  * All information necessary to keep track of an internal buffer is kept in
  * a struct eerbuffer. The buffer specific to a file pointer is strored in
  * the private_data field of that file. To be able to write data to all
  * existing buffers, each buffer is also added to the bufferlist.
  * If the user does not want to read a complete record in one go, we have to
  * keep track of the rest of the record. residual stores the number of bytes
  * that are still to deliver. If the rest of the record is invalidated between
  * two reads then residual will be set to -1 so that the next read will fail.
  * All entries in the eerbuffer structure are protected with the bufferlock.
  * To avoid races between writing to a buffer on the one side and creating
  * and destroying buffers on the other side, the bufferlock must also be used
  * to protect the bufferlist.
  */
 
 static int eer_pages = 5;
 module_param(eer_pages, int, S_IRUGO|S_IWUSR);
 
 struct eerbuffer {
     struct list_head list;
     char **buffer;
     int buffersize;
     int buffer_page_count;
     int head;
         int tail;
     int residual;
 };
 
 static LIST_HEAD(bufferlist);
 static DEFINE_SPINLOCK(bufferlock);
 static DECLARE_WAIT_QUEUE_HEAD(dasd_eer_read_wait_queue);
 
 /*
  * How many free bytes are available on the buffer.
  * Needs to be called with bufferlock held.
  */
 static int dasd_eer_get_free_bytes(struct eerbuffer *eerb)
 {
     if (eerb->head < eerb->tail)
         return eerb->tail - eerb->head - 1;
     return eerb->buffersize - eerb->head + eerb->tail -1;
 }
 
 /*
  * How many bytes of buffer space are used.
  * Needs to be called with bufferlock held.
  */
 static int dasd_eer_get_filled_bytes(struct eerbuffer *eerb)
 {
 
     if (eerb->head >= eerb->tail)
         return eerb->head - eerb->tail;
     return eerb->buffersize - eerb->tail + eerb->head;
 }
 
 /*
  * The dasd_eer_write_buffer function just copies count bytes of data
  * to the buffer. Make sure to call dasd_eer_start_record first, to
  * make sure that enough free space is available.
  * Needs to be called with bufferlock held.
  */
 static void dasd_eer_write_buffer(struct eerbuffer *eerb,
                   char *data, int count)
 {
 
     unsigned long headindex,localhead;
     unsigned long rest, len;
     char *nextdata;
 
     nextdata = data;
     rest = count;
     while (rest > 0) {
         headindex = eerb->head / PAGE_SIZE;
         localhead = eerb->head % PAGE_SIZE;
         len = min(rest, PAGE_SIZE - localhead);
         memcpy(eerb->buffer[headindex]+localhead, nextdata, len);
         nextdata += len;
         rest -= len;
         eerb->head += len;
         if (eerb->head == eerb->buffersize)
             eerb->head = 0; /* wrap around */
         BUG_ON(eerb->head > eerb->buffersize);
     }
 }
 
 /*
  * Needs to be called with bufferlock held.
  */
 static int dasd_eer_read_buffer(struct eerbuffer *eerb, char *data, int count)
 {
 
     unsigned long tailindex,localtail;
     unsigned long rest, len, finalcount;
     char *nextdata;
 
     finalcount = min(count, dasd_eer_get_filled_bytes(eerb));
     nextdata = data;
     rest = finalcount;
     while (rest > 0) {
         tailindex = eerb->tail / PAGE_SIZE;
         localtail = eerb->tail % PAGE_SIZE;
         len = min(rest, PAGE_SIZE - localtail);
         memcpy(nextdata, eerb->buffer[tailindex] + localtail, len);
         nextdata += len;
         rest -= len;
         eerb->tail += len;
         if (eerb->tail == eerb->buffersize)
             eerb->tail = 0; /* wrap around */
         BUG_ON(eerb->tail > eerb->buffersize);
     }
     return finalcount;
 }
 
 /*
  * Whenever you want to write a blob of data to the internal buffer you
  * have to start by using this function first. It will write the number
  * of bytes that will be written to the buffer. If necessary it will remove
  * old records to make room for the new one.
  * Needs to be called with bufferlock held.
  */
 static int dasd_eer_start_record(struct eerbuffer *eerb, int count)
 {
     int tailcount;
 
     if (count + sizeof(count) > eerb->buffersize)
         return -ENOMEM;
     while (dasd_eer_get_free_bytes(eerb) < count + sizeof(count)) {
         if (eerb->residual > 0) {
             eerb->tail += eerb->residual;
             if (eerb->tail >= eerb->buffersize)
                 eerb->tail -= eerb->buffersize;
             eerb->residual = -1;
         }
         dasd_eer_read_buffer(eerb, (char *) &tailcount,
                      sizeof(tailcount));
         eerb->tail += tailcount;
         if (eerb->tail >= eerb->buffersize)
             eerb->tail -= eerb->buffersize;
     }
     dasd_eer_write_buffer(eerb, (char*) &count, sizeof(count));
 
     return 0;
 };
 
 /*
  * Release pages that are not used anymore.
  */
 static void dasd_eer_free_buffer_pages(char **buf, int no_pages)
 {
     int i;
 
     for (i = 0; i < no_pages; i++)
         free_page((unsigned long) buf[i]);
 }
 
 /*
  * Allocate a new set of memory pages.
  */
 static int dasd_eer_allocate_buffer_pages(char **buf, int no_pages)
 {
     int i;
 
     for (i = 0; i < no_pages; i++) {
         buf[i] = (char *) get_zeroed_page(GFP_KERNEL);
         if (!buf[i]) {
             dasd_eer_free_buffer_pages(buf, i);
             return -ENOMEM;
         }
     }
     return 0;
 }
 
 /*
  * SECTION: The extended error reporting functionality
  */
 
 /*
  * When a DASD device driver wants to report an error, it calls the
  * function dasd_eer_write and gives the respective trigger ID as
  * parameter. Currently there are four kinds of triggers:
  *
  * DASD_EER_FATALERROR:  all kinds of unrecoverable I/O problems
  * DASD_EER_PPRCSUSPEND: PPRC was suspended
  * DASD_EER_NOPATH:      There is no path to the device left.
  * DASD_EER_STATECHANGE: The state of the device has changed.
  *
  * For the first three triggers all required information can be supplied by
  * the caller. For these triggers a record is written by the function
  * dasd_eer_write_standard_trigger.
  *
  * The DASD_EER_STATECHANGE trigger is special since a sense subsystem
  * status ccw need to be executed to gather the necessary sense data first.
  * The dasd_eer_snss function will queue the SNSS request and the request
  * callback will then call dasd_eer_write with the DASD_EER_STATCHANGE
  * trigger.
  *
  * To avoid memory allocations at runtime, the necessary memory is allocated
  * when the extended error reporting is enabled for a device (by
  * dasd_eer_probe). There is one sense subsystem status request for each
  * eer enabled DASD device. The presence of the cqr in device->eer_cqr
  * indicates that eer is enable for the device. The use of the snss request
  * is protected by the DASD_FLAG_EER_IN_USE bit. When this flag indicates
  * that the cqr is currently in use, dasd_eer_snss cannot start a second
  * request but sets the DASD_FLAG_EER_SNSS flag instead. The callback of
  * the SNSS request will check the bit and call dasd_eer_snss again.
  */
 
 #define SNSS_DATA_SIZE 44
 
 #define DASD_EER_BUSID_SIZE 10
 struct dasd_eer_header {
     __u32 total_size;
     __u32 trigger;
     __u64 tv_sec;
     __u64 tv_usec;
     char busid[DASD_EER_BUSID_SIZE];
 } __attribute__ ((packed));
 
 /*
  * The following function can be used for those triggers that have
  * all necessary data available when the function is called.
  * If the parameter cqr is not NULL, the chain of requests will be searched
  * for valid sense data, and all valid sense data sets will be added to
  * the triggers data.
  */
 static void dasd_eer_write_standard_trigger(struct dasd_device *device,
                         struct dasd_ccw_req *cqr,
                         int trigger)
 {
     struct dasd_ccw_req *temp_cqr;
     int data_size;
     struct timespec64 ts;
     struct dasd_eer_header header;
     unsigned long flags;
     struct eerbuffer *eerb;
     char *sense;
 
     /* go through cqr chain and count the valid sense data sets */
     data_size = 0;
     for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers)
         if (dasd_get_sense(&temp_cqr->irb))
             data_size += 32;
 
     header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
     header.trigger = trigger;
     ktime_get_real_ts64(&ts);
     header.tv_sec = ts.tv_sec;
     header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
     strlcpy(header.busid, dev_name(&device->cdev->dev),
         DASD_EER_BUSID_SIZE);
 
     spin_lock_irqsave(&bufferlock, flags);
     list_for_each_entry(eerb, &bufferlist, list) {
         dasd_eer_start_record(eerb, header.total_size);
         dasd_eer_write_buffer(eerb, (char *) &header, sizeof(header));
         for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers) {
             sense = dasd_get_sense(&temp_cqr->irb);
             if (sense)
                 dasd_eer_write_buffer(eerb, sense, 32);
         }
         dasd_eer_write_buffer(eerb, "EOR", 4);
     }
     spin_unlock_irqrestore(&bufferlock, flags);
     wake_up_interruptible(&dasd_eer_read_wait_queue);
 }
 
 /*
  * This function writes a DASD_EER_STATECHANGE trigger.
  */
 static void dasd_eer_write_snss_trigger(struct dasd_device *device,
                     struct dasd_ccw_req *cqr,
                     int trigger)
 {
     int data_size;
     int snss_rc;
     struct timespec64 ts;
     struct dasd_eer_header header;
     unsigned long flags;
     struct eerbuffer *eerb;
 
     snss_rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
     if (snss_rc)
         data_size = 0;
     else
         data_size = SNSS_DATA_SIZE;
 
     header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
     header.trigger = DASD_EER_STATECHANGE;
     ktime_get_real_ts64(&ts);
     header.tv_sec = ts.tv_sec;
     header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
     strlcpy(header.busid, dev_name(&device->cdev->dev),
         DASD_EER_BUSID_SIZE);
 
     spin_lock_irqsave(&bufferlock, flags);
     list_for_each_entry(eerb, &bufferlist, list) {
         dasd_eer_start_record(eerb, header.total_size);
         dasd_eer_write_buffer(eerb, (char *) &header , sizeof(header));
         if (!snss_rc)
             dasd_eer_write_buffer(eerb, cqr->data, SNSS_DATA_SIZE);
         dasd_eer_write_buffer(eerb, "EOR", 4);
     }
     spin_unlock_irqrestore(&bufferlock, flags);
     wake_up_interruptible(&dasd_eer_read_wait_queue);
 }
 
 /*
  * This function is called for all triggers. It calls the appropriate
  * function that writes the actual trigger records.
  */
 void dasd_eer_write(struct dasd_device *device, struct dasd_ccw_req *cqr,
             unsigned int id)
 {
     if (!device->eer_cqr)
         return;
     switch (id) {
     case DASD_EER_FATALERROR:
     case DASD_EER_PPRCSUSPEND:
         dasd_eer_write_standard_trigger(device, cqr, id);
         break;
     case DASD_EER_NOPATH:
     case DASD_EER_NOSPC:
         dasd_eer_write_standard_trigger(device, NULL, id);
         break;
     case DASD_EER_STATECHANGE:
         dasd_eer_write_snss_trigger(device, cqr, id);
         break;
     default: /* unknown trigger, so we write it without any sense data */
         dasd_eer_write_standard_trigger(device, NULL, id);
         break;
     }
 }
 EXPORT_SYMBOL(dasd_eer_write);
 
 /*
  * Start a sense subsystem status request.
  * Needs to be called with the device held.
  */
 void dasd_eer_snss(struct dasd_device *device)
 {
     struct dasd_ccw_req *cqr;
 
     cqr = device->eer_cqr;
     if (!cqr)   /* Device not eer enabled. */
         return;
     if (test_and_set_bit(DASD_FLAG_EER_IN_USE, &device->flags)) {
         /* Sense subsystem status request in use. */
         set_bit(DASD_FLAG_EER_SNSS, &device->flags);
         return;
     }
     /* cdev is already locked, can't use dasd_add_request_head */
     clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
     cqr->status = DASD_CQR_QUEUED;
     list_add(&cqr->devlist, &device->ccw_queue);
     dasd_schedule_device_bh(device);
 }
 
 /*
  * Callback function for use with sense subsystem status request.
  */
 static void dasd_eer_snss_cb(struct dasd_ccw_req *cqr, void *data)
 {
     struct dasd_device *device = cqr->startdev;
     unsigned long flags;
 
     dasd_eer_write(device, cqr, DASD_EER_STATECHANGE);
     spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
     if (device->eer_cqr == cqr) {
         clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
         if (test_bit(DASD_FLAG_EER_SNSS, &device->flags))
             /* Another SNSS has been requested in the meantime. */
             dasd_eer_snss(device);
         cqr = NULL;
     }
     spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
     if (cqr)
         /*
          * Extended error recovery has been switched off while
          * the SNSS request was running. It could even have
          * been switched off and on again in which case there
          * is a new ccw in device->eer_cqr. Free the "old"
          * snss request now.
          */
         dasd_sfree_request(cqr, device);
 }
 
 /*
  * Enable error reporting on a given device.
  */
 int dasd_eer_enable(struct dasd_device *device)
 {
     struct dasd_ccw_req *cqr = NULL;
     unsigned long flags;
     struct ccw1 *ccw;
     int rc = 0;
 
     spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
     if (device->eer_cqr)
         goto out;
     else if (!device->discipline ||
          strcmp(device->discipline->name, "ECKD"))
         rc = -EMEDIUMTYPE;
     else if (test_bit(DASD_FLAG_OFFLINE, &device->flags))
         rc = -EBUSY;
 
     if (rc)
         goto out;
 
     cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1 /* SNSS */,
                    SNSS_DATA_SIZE, device, NULL);
     if (IS_ERR(cqr)) {
         rc = -ENOMEM;
         cqr = NULL;
         goto out;
     }
 
     cqr->startdev = device;
     cqr->retries = 255;
     cqr->expires = 10 * HZ;
     clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
     set_bit(DASD_CQR_ALLOW_SLOCK, &cqr->flags);
 
     ccw = cqr->cpaddr;
     ccw->cmd_code = DASD_ECKD_CCW_SNSS;
     ccw->count = SNSS_DATA_SIZE;
     ccw->flags = 0;
     ccw->cda = (__u32)(addr_t) cqr->data;
 
     cqr->buildclk = get_tod_clock();
     cqr->status = DASD_CQR_FILLED;
     cqr->callback = dasd_eer_snss_cb;
 
     if (!device->eer_cqr) {
         device->eer_cqr = cqr;
         cqr = NULL;
     }
 
 out:
     spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 
     if (cqr)
         dasd_sfree_request(cqr, device);
 
     return rc;
 }
 
 /*
  * Disable error reporting on a given device.
  */
 void dasd_eer_disable(struct dasd_device *device)
 {
     struct dasd_ccw_req *cqr;
     unsigned long flags;
     int in_use;
 
     if (!device->eer_cqr)
         return;
     spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
     cqr = device->eer_cqr;
     device->eer_cqr = NULL;
     clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
     in_use = test_and_clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
     spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
     if (cqr && !in_use)
         dasd_sfree_request(cqr, device);
 }
 
 /*
  * SECTION: the device operations
  */
 
 /*
  * On the one side we need a lock to access our internal buffer, on the
  * other side a copy_to_user can sleep. So we need to copy the data we have
  * to transfer in a readbuffer, which is protected by the readbuffer_mutex.
  */
 static char readbuffer[PAGE_SIZE];
 static DEFINE_MUTEX(readbuffer_mutex);
 
 static int dasd_eer_open(struct inode *inp, struct file *filp)
 {
     struct eerbuffer *eerb;
     unsigned long flags;
 
     eerb = kzalloc(sizeof(struct eerbuffer), GFP_KERNEL);
     if (!eerb)
         return -ENOMEM;
     eerb->buffer_page_count = eer_pages;
     if (eerb->buffer_page_count < 1 ||
         eerb->buffer_page_count > INT_MAX / PAGE_SIZE) {
         kfree(eerb);
         DBF_EVENT(DBF_WARNING, "can't open device since module "
             "parameter eer_pages is smaller than 1 or"
             " bigger than %d", (int)(INT_MAX / PAGE_SIZE));
         return -EINVAL;
     }
     eerb->buffersize = eerb->buffer_page_count * PAGE_SIZE;
     eerb->buffer = kmalloc_array(eerb->buffer_page_count, sizeof(char *),
                      GFP_KERNEL);
         if (!eerb->buffer) {
         kfree(eerb);
                 return -ENOMEM;
     }
     if (dasd_eer_allocate_buffer_pages(eerb->buffer,
                        eerb->buffer_page_count)) {
         kfree(eerb->buffer);
         kfree(eerb);
         return -ENOMEM;
     }
     filp->private_data = eerb;
     spin_lock_irqsave(&bufferlock, flags);
     list_add(&eerb->list, &bufferlist);
     spin_unlock_irqrestore(&bufferlock, flags);
 
     return nonseekable_open(inp,filp);
 }
 
 static int dasd_eer_close(struct inode *inp, struct file *filp)
 {
     struct eerbuffer *eerb;
     unsigned long flags;
 
     eerb = (struct eerbuffer *) filp->private_data;
     spin_lock_irqsave(&bufferlock, flags);
     list_del(&eerb->list);
     spin_unlock_irqrestore(&bufferlock, flags);
     dasd_eer_free_buffer_pages(eerb->buffer, eerb->buffer_page_count);
     kfree(eerb->buffer);
     kfree(eerb);
 
     return 0;
 }
 
 static ssize_t dasd_eer_read(struct file *filp, char __user *buf,
                  size_t count, loff_t *ppos)
 {
     int tc,rc;
     int tailcount,effective_count;
         unsigned long flags;
     struct eerbuffer *eerb;
 
     eerb = (struct eerbuffer *) filp->private_data;
     if (mutex_lock_interruptible(&readbuffer_mutex))
         return -ERESTARTSYS;
 
     spin_lock_irqsave(&bufferlock, flags);
 
     if (eerb->residual < 0) { /* the remainder of this record */
                           /* has been deleted             */
         eerb->residual = 0;
         spin_unlock_irqrestore(&bufferlock, flags);
         mutex_unlock(&readbuffer_mutex);
         return -EIO;
     } else if (eerb->residual > 0) {
         /* OK we still have a second half of a record to deliver */
         effective_count = min(eerb->residual, (int) count);
         eerb->residual -= effective_count;
     } else {
         tc = 0;
         while (!tc) {
             tc = dasd_eer_read_buffer(eerb, (char *) &tailcount,
                           sizeof(tailcount));
             if (!tc) {
                 /* no data available */
                 spin_unlock_irqrestore(&bufferlock, flags);
                 mutex_unlock(&readbuffer_mutex);
                 if (filp->f_flags & O_NONBLOCK)
                     return -EAGAIN;
                 rc = wait_event_interruptible(
                     dasd_eer_read_wait_queue,
                     eerb->head != eerb->tail);
                 if (rc)
                     return rc;
                 if (mutex_lock_interruptible(&readbuffer_mutex))
                     return -ERESTARTSYS;
                 spin_lock_irqsave(&bufferlock, flags);
             }
         }
         WARN_ON(tc != sizeof(tailcount));
         effective_count = min(tailcount,(int)count);
         eerb->residual = tailcount - effective_count;
     }
 
     tc = dasd_eer_read_buffer(eerb, readbuffer, effective_count);
     WARN_ON(tc != effective_count);
 
     spin_unlock_irqrestore(&bufferlock, flags);
 
     if (copy_to_user(buf, readbuffer, effective_count)) {
         mutex_unlock(&readbuffer_mutex);
         return -EFAULT;
     }
 
     mutex_unlock(&readbuffer_mutex);
     return effective_count;
 }
 
 static __poll_t dasd_eer_poll(struct file *filp, poll_table *ptable)
 {
     __poll_t mask;
     unsigned long flags;
     struct eerbuffer *eerb;
 
     eerb = (struct eerbuffer *) filp->private_data;
     poll_wait(filp, &dasd_eer_read_wait_queue, ptable);
     spin_lock_irqsave(&bufferlock, flags);
     if (eerb->head != eerb->tail)
         mask = EPOLLIN | EPOLLRDNORM ;
     else
         mask = 0;
     spin_unlock_irqrestore(&bufferlock, flags);
     return mask;
 }
 
 static const struct file_operations dasd_eer_fops = {
     .open       = &dasd_eer_open,
     .release    = &dasd_eer_close,
     .read       = &dasd_eer_read,
     .poll       = &dasd_eer_poll,
     .owner      = THIS_MODULE,
     .llseek     = noop_llseek,
 };
 
 static struct miscdevice *dasd_eer_dev = NULL;
 
 int __init dasd_eer_init(void)
 {
     int rc;
 
     dasd_eer_dev = kzalloc(sizeof(*dasd_eer_dev), GFP_KERNEL);
     if (!dasd_eer_dev)
         return -ENOMEM;
 
     dasd_eer_dev->minor = MISC_DYNAMIC_MINOR;
     dasd_eer_dev->name  = "dasd_eer";
     dasd_eer_dev->fops  = &dasd_eer_fops;
 
     rc = misc_register(dasd_eer_dev);
     if (rc) {
         kfree(dasd_eer_dev);
         dasd_eer_dev = NULL;
         DBF_EVENT(DBF_ERR, "%s", "dasd_eer_init could not "
                "register misc device");
         return rc;
     }
 
     return 0;
 }
 
 void dasd_eer_exit(void)
 {
     if (dasd_eer_dev) {
         misc_deregister(dasd_eer_dev);
         kfree(dasd_eer_dev);
         dasd_eer_dev = NULL;
     }
 }

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