linux/drivers/s390/block/dasd_eer.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  Character device driver for extended error reporting.
   4 *
   5 *  Copyright IBM Corp. 2005
   6 *  extended error reporting for DASD ECKD devices
   7 *  Author(s): Stefan Weinhuber <wein@de.ibm.com>
   8 */
   9
  10#define KMSG_COMPONENT "dasd-eckd"
  11
  12#include <linux/init.h>
  13#include <linux/fs.h>
  14#include <linux/kernel.h>
  15#include <linux/miscdevice.h>
  16#include <linux/module.h>
  17#include <linux/moduleparam.h>
  18#include <linux/device.h>
  19#include <linux/poll.h>
  20#include <linux/mutex.h>
  21#include <linux/err.h>
  22#include <linux/slab.h>
  23
  24#include <linux/uaccess.h>
  25#include <linux/atomic.h>
  26#include <asm/ebcdic.h>
  27
  28#include "dasd_int.h"
  29#include "dasd_eckd.h"
  30
  31#ifdef PRINTK_HEADER
  32#undef PRINTK_HEADER
  33#endif                          /* PRINTK_HEADER */
  34#define PRINTK_HEADER "dasd(eer):"
  35
  36/*
  37 * SECTION: the internal buffer
  38 */
  39
  40/*
  41 * The internal buffer is meant to store obaque blobs of data, so it does
  42 * not know of higher level concepts like triggers.
  43 * It consists of a number of pages that are used as a ringbuffer. Each data
  44 * blob is stored in a simple record that consists of an integer, which
  45 * contains the size of the following data, and the data bytes themselfes.
  46 *
  47 * To allow for multiple independent readers we create one internal buffer
  48 * each time the device is opened and destroy the buffer when the file is
  49 * closed again. The number of pages used for this buffer is determined by
  50 * the module parmeter eer_pages.
  51 *
  52 * One record can be written to a buffer by using the functions
  53 * - dasd_eer_start_record (one time per record to write the size to the
  54 *                          buffer and reserve the space for the data)
  55 * - dasd_eer_write_buffer (one or more times per record to write the data)
  56 * The data can be written in several steps but you will have to compute
  57 * the total size up front for the invocation of dasd_eer_start_record.
  58 * If the ringbuffer is full, dasd_eer_start_record will remove the required
  59 * number of old records.
  60 *
  61 * A record is typically read in two steps, first read the integer that
  62 * specifies the size of the following data, then read the data.
  63 * Both can be done by
  64 * - dasd_eer_read_buffer
  65 *
  66 * For all mentioned functions you need to get the bufferlock first and keep
  67 * it until a complete record is written or read.
  68 *
  69 * All information necessary to keep track of an internal buffer is kept in
  70 * a struct eerbuffer. The buffer specific to a file pointer is strored in
  71 * the private_data field of that file. To be able to write data to all
  72 * existing buffers, each buffer is also added to the bufferlist.
  73 * If the user does not want to read a complete record in one go, we have to
  74 * keep track of the rest of the record. residual stores the number of bytes
  75 * that are still to deliver. If the rest of the record is invalidated between
  76 * two reads then residual will be set to -1 so that the next read will fail.
  77 * All entries in the eerbuffer structure are protected with the bufferlock.
  78 * To avoid races between writing to a buffer on the one side and creating
  79 * and destroying buffers on the other side, the bufferlock must also be used
  80 * to protect the bufferlist.
  81 */
  82
  83static int eer_pages = 5;
  84module_param(eer_pages, int, S_IRUGO|S_IWUSR);
  85
  86struct eerbuffer {
  87        struct list_head list;
  88        char **buffer;
  89        int buffersize;
  90        int buffer_page_count;
  91        int head;
  92        int tail;
  93        int residual;
  94};
  95
  96static LIST_HEAD(bufferlist);
  97static DEFINE_SPINLOCK(bufferlock);
  98static DECLARE_WAIT_QUEUE_HEAD(dasd_eer_read_wait_queue);
  99
 100/*
 101 * How many free bytes are available on the buffer.
 102 * Needs to be called with bufferlock held.
 103 */
 104static int dasd_eer_get_free_bytes(struct eerbuffer *eerb)
 105{
 106        if (eerb->head < eerb->tail)
 107                return eerb->tail - eerb->head - 1;
 108        return eerb->buffersize - eerb->head + eerb->tail -1;
 109}
 110
 111/*
 112 * How many bytes of buffer space are used.
 113 * Needs to be called with bufferlock held.
 114 */
 115static int dasd_eer_get_filled_bytes(struct eerbuffer *eerb)
 116{
 117
 118        if (eerb->head >= eerb->tail)
 119                return eerb->head - eerb->tail;
 120        return eerb->buffersize - eerb->tail + eerb->head;
 121}
 122
 123/*
 124 * The dasd_eer_write_buffer function just copies count bytes of data
 125 * to the buffer. Make sure to call dasd_eer_start_record first, to
 126 * make sure that enough free space is available.
 127 * Needs to be called with bufferlock held.
 128 */
 129static void dasd_eer_write_buffer(struct eerbuffer *eerb,
 130                                  char *data, int count)
 131{
 132
 133        unsigned long headindex,localhead;
 134        unsigned long rest, len;
 135        char *nextdata;
 136
 137        nextdata = data;
 138        rest = count;
 139        while (rest > 0) {
 140                headindex = eerb->head / PAGE_SIZE;
 141                localhead = eerb->head % PAGE_SIZE;
 142                len = min(rest, PAGE_SIZE - localhead);
 143                memcpy(eerb->buffer[headindex]+localhead, nextdata, len);
 144                nextdata += len;
 145                rest -= len;
 146                eerb->head += len;
 147                if (eerb->head == eerb->buffersize)
 148                        eerb->head = 0; /* wrap around */
 149                BUG_ON(eerb->head > eerb->buffersize);
 150        }
 151}
 152
 153/*
 154 * Needs to be called with bufferlock held.
 155 */
 156static int dasd_eer_read_buffer(struct eerbuffer *eerb, char *data, int count)
 157{
 158
 159        unsigned long tailindex,localtail;
 160        unsigned long rest, len, finalcount;
 161        char *nextdata;
 162
 163        finalcount = min(count, dasd_eer_get_filled_bytes(eerb));
 164        nextdata = data;
 165        rest = finalcount;
 166        while (rest > 0) {
 167                tailindex = eerb->tail / PAGE_SIZE;
 168                localtail = eerb->tail % PAGE_SIZE;
 169                len = min(rest, PAGE_SIZE - localtail);
 170                memcpy(nextdata, eerb->buffer[tailindex] + localtail, len);
 171                nextdata += len;
 172                rest -= len;
 173                eerb->tail += len;
 174                if (eerb->tail == eerb->buffersize)
 175                        eerb->tail = 0; /* wrap around */
 176                BUG_ON(eerb->tail > eerb->buffersize);
 177        }
 178        return finalcount;
 179}
 180
 181/*
 182 * Whenever you want to write a blob of data to the internal buffer you
 183 * have to start by using this function first. It will write the number
 184 * of bytes that will be written to the buffer. If necessary it will remove
 185 * old records to make room for the new one.
 186 * Needs to be called with bufferlock held.
 187 */
 188static int dasd_eer_start_record(struct eerbuffer *eerb, int count)
 189{
 190        int tailcount;
 191
 192        if (count + sizeof(count) > eerb->buffersize)
 193                return -ENOMEM;
 194        while (dasd_eer_get_free_bytes(eerb) < count + sizeof(count)) {
 195                if (eerb->residual > 0) {
 196                        eerb->tail += eerb->residual;
 197                        if (eerb->tail >= eerb->buffersize)
 198                                eerb->tail -= eerb->buffersize;
 199                        eerb->residual = -1;
 200                }
 201                dasd_eer_read_buffer(eerb, (char *) &tailcount,
 202                                     sizeof(tailcount));
 203                eerb->tail += tailcount;
 204                if (eerb->tail >= eerb->buffersize)
 205                        eerb->tail -= eerb->buffersize;
 206        }
 207        dasd_eer_write_buffer(eerb, (char*) &count, sizeof(count));
 208
 209        return 0;
 210};
 211
 212/*
 213 * Release pages that are not used anymore.
 214 */
 215static void dasd_eer_free_buffer_pages(char **buf, int no_pages)
 216{
 217        int i;
 218
 219        for (i = 0; i < no_pages; i++)
 220                free_page((unsigned long) buf[i]);
 221}
 222
 223/*
 224 * Allocate a new set of memory pages.
 225 */
 226static int dasd_eer_allocate_buffer_pages(char **buf, int no_pages)
 227{
 228        int i;
 229
 230        for (i = 0; i < no_pages; i++) {
 231                buf[i] = (char *) get_zeroed_page(GFP_KERNEL);
 232                if (!buf[i]) {
 233                        dasd_eer_free_buffer_pages(buf, i);
 234                        return -ENOMEM;
 235                }
 236        }
 237        return 0;
 238}
 239
 240/*
 241 * SECTION: The extended error reporting functionality
 242 */
 243
 244/*
 245 * When a DASD device driver wants to report an error, it calls the
 246 * function dasd_eer_write and gives the respective trigger ID as
 247 * parameter. Currently there are four kinds of triggers:
 248 *
 249 * DASD_EER_FATALERROR:  all kinds of unrecoverable I/O problems
 250 * DASD_EER_PPRCSUSPEND: PPRC was suspended
 251 * DASD_EER_NOPATH:      There is no path to the device left.
 252 * DASD_EER_STATECHANGE: The state of the device has changed.
 253 *
 254 * For the first three triggers all required information can be supplied by
 255 * the caller. For these triggers a record is written by the function
 256 * dasd_eer_write_standard_trigger.
 257 *
 258 * The DASD_EER_STATECHANGE trigger is special since a sense subsystem
 259 * status ccw need to be executed to gather the necessary sense data first.
 260 * The dasd_eer_snss function will queue the SNSS request and the request
 261 * callback will then call dasd_eer_write with the DASD_EER_STATCHANGE
 262 * trigger.
 263 *
 264 * To avoid memory allocations at runtime, the necessary memory is allocated
 265 * when the extended error reporting is enabled for a device (by
 266 * dasd_eer_probe). There is one sense subsystem status request for each
 267 * eer enabled DASD device. The presence of the cqr in device->eer_cqr
 268 * indicates that eer is enable for the device. The use of the snss request
 269 * is protected by the DASD_FLAG_EER_IN_USE bit. When this flag indicates
 270 * that the cqr is currently in use, dasd_eer_snss cannot start a second
 271 * request but sets the DASD_FLAG_EER_SNSS flag instead. The callback of
 272 * the SNSS request will check the bit and call dasd_eer_snss again.
 273 */
 274
 275#define SNSS_DATA_SIZE 44
 276
 277#define DASD_EER_BUSID_SIZE 10
 278struct dasd_eer_header {
 279        __u32 total_size;
 280        __u32 trigger;
 281        __u64 tv_sec;
 282        __u64 tv_usec;
 283        char busid[DASD_EER_BUSID_SIZE];
 284} __attribute__ ((packed));
 285
 286/*
 287 * The following function can be used for those triggers that have
 288 * all necessary data available when the function is called.
 289 * If the parameter cqr is not NULL, the chain of requests will be searched
 290 * for valid sense data, and all valid sense data sets will be added to
 291 * the triggers data.
 292 */
 293static void dasd_eer_write_standard_trigger(struct dasd_device *device,
 294                                            struct dasd_ccw_req *cqr,
 295                                            int trigger)
 296{
 297        struct dasd_ccw_req *temp_cqr;
 298        int data_size;
 299        struct timespec64 ts;
 300        struct dasd_eer_header header;
 301        unsigned long flags;
 302        struct eerbuffer *eerb;
 303        char *sense;
 304
 305        /* go through cqr chain and count the valid sense data sets */
 306        data_size = 0;
 307        for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers)
 308                if (dasd_get_sense(&temp_cqr->irb))
 309                        data_size += 32;
 310
 311        header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
 312        header.trigger = trigger;
 313        ktime_get_real_ts64(&ts);
 314        header.tv_sec = ts.tv_sec;
 315        header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
 316        strlcpy(header.busid, dev_name(&device->cdev->dev),
 317                DASD_EER_BUSID_SIZE);
 318
 319        spin_lock_irqsave(&bufferlock, flags);
 320        list_for_each_entry(eerb, &bufferlist, list) {
 321                dasd_eer_start_record(eerb, header.total_size);
 322                dasd_eer_write_buffer(eerb, (char *) &header, sizeof(header));
 323                for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers) {
 324                        sense = dasd_get_sense(&temp_cqr->irb);
 325                        if (sense)
 326                                dasd_eer_write_buffer(eerb, sense, 32);
 327                }
 328                dasd_eer_write_buffer(eerb, "EOR", 4);
 329        }
 330        spin_unlock_irqrestore(&bufferlock, flags);
 331        wake_up_interruptible(&dasd_eer_read_wait_queue);
 332}
 333
 334/*
 335 * This function writes a DASD_EER_STATECHANGE trigger.
 336 */
 337static void dasd_eer_write_snss_trigger(struct dasd_device *device,
 338                                        struct dasd_ccw_req *cqr,
 339                                        int trigger)
 340{
 341        int data_size;
 342        int snss_rc;
 343        struct timespec64 ts;
 344        struct dasd_eer_header header;
 345        unsigned long flags;
 346        struct eerbuffer *eerb;
 347
 348        snss_rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
 349        if (snss_rc)
 350                data_size = 0;
 351        else
 352                data_size = SNSS_DATA_SIZE;
 353
 354        header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
 355        header.trigger = DASD_EER_STATECHANGE;
 356        ktime_get_real_ts64(&ts);
 357        header.tv_sec = ts.tv_sec;
 358        header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
 359        strlcpy(header.busid, dev_name(&device->cdev->dev),
 360                DASD_EER_BUSID_SIZE);
 361
 362        spin_lock_irqsave(&bufferlock, flags);
 363        list_for_each_entry(eerb, &bufferlist, list) {
 364                dasd_eer_start_record(eerb, header.total_size);
 365                dasd_eer_write_buffer(eerb, (char *) &header , sizeof(header));
 366                if (!snss_rc)
 367                        dasd_eer_write_buffer(eerb, cqr->data, SNSS_DATA_SIZE);
 368                dasd_eer_write_buffer(eerb, "EOR", 4);
 369        }
 370        spin_unlock_irqrestore(&bufferlock, flags);
 371        wake_up_interruptible(&dasd_eer_read_wait_queue);
 372}
 373
 374/*
 375 * This function is called for all triggers. It calls the appropriate
 376 * function that writes the actual trigger records.
 377 */
 378void dasd_eer_write(struct dasd_device *device, struct dasd_ccw_req *cqr,
 379                    unsigned int id)
 380{
 381        if (!device->eer_cqr)
 382                return;
 383        switch (id) {
 384        case DASD_EER_FATALERROR:
 385        case DASD_EER_PPRCSUSPEND:
 386                dasd_eer_write_standard_trigger(device, cqr, id);
 387                break;
 388        case DASD_EER_NOPATH:
 389                dasd_eer_write_standard_trigger(device, NULL, id);
 390                break;
 391        case DASD_EER_STATECHANGE:
 392                dasd_eer_write_snss_trigger(device, cqr, id);
 393                break;
 394        default: /* unknown trigger, so we write it without any sense data */
 395                dasd_eer_write_standard_trigger(device, NULL, id);
 396                break;
 397        }
 398}
 399EXPORT_SYMBOL(dasd_eer_write);
 400
 401/*
 402 * Start a sense subsystem status request.
 403 * Needs to be called with the device held.
 404 */
 405void dasd_eer_snss(struct dasd_device *device)
 406{
 407        struct dasd_ccw_req *cqr;
 408
 409        cqr = device->eer_cqr;
 410        if (!cqr)       /* Device not eer enabled. */
 411                return;
 412        if (test_and_set_bit(DASD_FLAG_EER_IN_USE, &device->flags)) {
 413                /* Sense subsystem status request in use. */
 414                set_bit(DASD_FLAG_EER_SNSS, &device->flags);
 415                return;
 416        }
 417        /* cdev is already locked, can't use dasd_add_request_head */
 418        clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
 419        cqr->status = DASD_CQR_QUEUED;
 420        list_add(&cqr->devlist, &device->ccw_queue);
 421        dasd_schedule_device_bh(device);
 422}
 423
 424/*
 425 * Callback function for use with sense subsystem status request.
 426 */
 427static void dasd_eer_snss_cb(struct dasd_ccw_req *cqr, void *data)
 428{
 429        struct dasd_device *device = cqr->startdev;
 430        unsigned long flags;
 431
 432        dasd_eer_write(device, cqr, DASD_EER_STATECHANGE);
 433        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 434        if (device->eer_cqr == cqr) {
 435                clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
 436                if (test_bit(DASD_FLAG_EER_SNSS, &device->flags))
 437                        /* Another SNSS has been requested in the meantime. */
 438                        dasd_eer_snss(device);
 439                cqr = NULL;
 440        }
 441        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 442        if (cqr)
 443                /*
 444                 * Extended error recovery has been switched off while
 445                 * the SNSS request was running. It could even have
 446                 * been switched off and on again in which case there
 447                 * is a new ccw in device->eer_cqr. Free the "old"
 448                 * snss request now.
 449                 */
 450                dasd_sfree_request(cqr, device);
 451}
 452
 453/*
 454 * Enable error reporting on a given device.
 455 */
 456int dasd_eer_enable(struct dasd_device *device)
 457{
 458        struct dasd_ccw_req *cqr = NULL;
 459        unsigned long flags;
 460        struct ccw1 *ccw;
 461        int rc = 0;
 462
 463        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 464        if (device->eer_cqr)
 465                goto out;
 466        else if (!device->discipline ||
 467                 strcmp(device->discipline->name, "ECKD"))
 468                rc = -EMEDIUMTYPE;
 469        else if (test_bit(DASD_FLAG_OFFLINE, &device->flags))
 470                rc = -EBUSY;
 471
 472        if (rc)
 473                goto out;
 474
 475        cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1 /* SNSS */,
 476                                   SNSS_DATA_SIZE, device, NULL);
 477        if (IS_ERR(cqr)) {
 478                rc = -ENOMEM;
 479                cqr = NULL;
 480                goto out;
 481        }
 482
 483        cqr->startdev = device;
 484        cqr->retries = 255;
 485        cqr->expires = 10 * HZ;
 486        clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
 487        set_bit(DASD_CQR_ALLOW_SLOCK, &cqr->flags);
 488
 489        ccw = cqr->cpaddr;
 490        ccw->cmd_code = DASD_ECKD_CCW_SNSS;
 491        ccw->count = SNSS_DATA_SIZE;
 492        ccw->flags = 0;
 493        ccw->cda = (__u32)(addr_t) cqr->data;
 494
 495        cqr->buildclk = get_tod_clock();
 496        cqr->status = DASD_CQR_FILLED;
 497        cqr->callback = dasd_eer_snss_cb;
 498
 499        if (!device->eer_cqr) {
 500                device->eer_cqr = cqr;
 501                cqr = NULL;
 502        }
 503
 504out:
 505        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 506
 507        if (cqr)
 508                dasd_sfree_request(cqr, device);
 509
 510        return rc;
 511}
 512
 513/*
 514 * Disable error reporting on a given device.
 515 */
 516void dasd_eer_disable(struct dasd_device *device)
 517{
 518        struct dasd_ccw_req *cqr;
 519        unsigned long flags;
 520        int in_use;
 521
 522        if (!device->eer_cqr)
 523                return;
 524        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 525        cqr = device->eer_cqr;
 526        device->eer_cqr = NULL;
 527        clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
 528        in_use = test_and_clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
 529        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 530        if (cqr && !in_use)
 531                dasd_sfree_request(cqr, device);
 532}
 533
 534/*
 535 * SECTION: the device operations
 536 */
 537
 538/*
 539 * On the one side we need a lock to access our internal buffer, on the
 540 * other side a copy_to_user can sleep. So we need to copy the data we have
 541 * to transfer in a readbuffer, which is protected by the readbuffer_mutex.
 542 */
 543static char readbuffer[PAGE_SIZE];
 544static DEFINE_MUTEX(readbuffer_mutex);
 545
 546static int dasd_eer_open(struct inode *inp, struct file *filp)
 547{
 548        struct eerbuffer *eerb;
 549        unsigned long flags;
 550
 551        eerb = kzalloc(sizeof(struct eerbuffer), GFP_KERNEL);
 552        if (!eerb)
 553                return -ENOMEM;
 554        eerb->buffer_page_count = eer_pages;
 555        if (eerb->buffer_page_count < 1 ||
 556            eerb->buffer_page_count > INT_MAX / PAGE_SIZE) {
 557                kfree(eerb);
 558                DBF_EVENT(DBF_WARNING, "can't open device since module "
 559                        "parameter eer_pages is smaller than 1 or"
 560                        " bigger than %d", (int)(INT_MAX / PAGE_SIZE));
 561                return -EINVAL;
 562        }
 563        eerb->buffersize = eerb->buffer_page_count * PAGE_SIZE;
 564        eerb->buffer = kmalloc_array(eerb->buffer_page_count, sizeof(char *),
 565                                     GFP_KERNEL);
 566        if (!eerb->buffer) {
 567                kfree(eerb);
 568                return -ENOMEM;
 569        }
 570        if (dasd_eer_allocate_buffer_pages(eerb->buffer,
 571                                           eerb->buffer_page_count)) {
 572                kfree(eerb->buffer);
 573                kfree(eerb);
 574                return -ENOMEM;
 575        }
 576        filp->private_data = eerb;
 577        spin_lock_irqsave(&bufferlock, flags);
 578        list_add(&eerb->list, &bufferlist);
 579        spin_unlock_irqrestore(&bufferlock, flags);
 580
 581        return nonseekable_open(inp,filp);
 582}
 583
 584static int dasd_eer_close(struct inode *inp, struct file *filp)
 585{
 586        struct eerbuffer *eerb;
 587        unsigned long flags;
 588
 589        eerb = (struct eerbuffer *) filp->private_data;
 590        spin_lock_irqsave(&bufferlock, flags);
 591        list_del(&eerb->list);
 592        spin_unlock_irqrestore(&bufferlock, flags);
 593        dasd_eer_free_buffer_pages(eerb->buffer, eerb->buffer_page_count);
 594        kfree(eerb->buffer);
 595        kfree(eerb);
 596
 597        return 0;
 598}
 599
 600static ssize_t dasd_eer_read(struct file *filp, char __user *buf,
 601                             size_t count, loff_t *ppos)
 602{
 603        int tc,rc;
 604        int tailcount,effective_count;
 605        unsigned long flags;
 606        struct eerbuffer *eerb;
 607
 608        eerb = (struct eerbuffer *) filp->private_data;
 609        if (mutex_lock_interruptible(&readbuffer_mutex))
 610                return -ERESTARTSYS;
 611
 612        spin_lock_irqsave(&bufferlock, flags);
 613
 614        if (eerb->residual < 0) { /* the remainder of this record */
 615                                  /* has been deleted             */
 616                eerb->residual = 0;
 617                spin_unlock_irqrestore(&bufferlock, flags);
 618                mutex_unlock(&readbuffer_mutex);
 619                return -EIO;
 620        } else if (eerb->residual > 0) {
 621                /* OK we still have a second half of a record to deliver */
 622                effective_count = min(eerb->residual, (int) count);
 623                eerb->residual -= effective_count;
 624        } else {
 625                tc = 0;
 626                while (!tc) {
 627                        tc = dasd_eer_read_buffer(eerb, (char *) &tailcount,
 628                                                  sizeof(tailcount));
 629                        if (!tc) {
 630                                /* no data available */
 631                                spin_unlock_irqrestore(&bufferlock, flags);
 632                                mutex_unlock(&readbuffer_mutex);
 633                                if (filp->f_flags & O_NONBLOCK)
 634                                        return -EAGAIN;
 635                                rc = wait_event_interruptible(
 636                                        dasd_eer_read_wait_queue,
 637                                        eerb->head != eerb->tail);
 638                                if (rc)
 639                                        return rc;
 640                                if (mutex_lock_interruptible(&readbuffer_mutex))
 641                                        return -ERESTARTSYS;
 642                                spin_lock_irqsave(&bufferlock, flags);
 643                        }
 644                }
 645                WARN_ON(tc != sizeof(tailcount));
 646                effective_count = min(tailcount,(int)count);
 647                eerb->residual = tailcount - effective_count;
 648        }
 649
 650        tc = dasd_eer_read_buffer(eerb, readbuffer, effective_count);
 651        WARN_ON(tc != effective_count);
 652
 653        spin_unlock_irqrestore(&bufferlock, flags);
 654
 655        if (copy_to_user(buf, readbuffer, effective_count)) {
 656                mutex_unlock(&readbuffer_mutex);
 657                return -EFAULT;
 658        }
 659
 660        mutex_unlock(&readbuffer_mutex);
 661        return effective_count;
 662}
 663
 664static __poll_t dasd_eer_poll(struct file *filp, poll_table *ptable)
 665{
 666        __poll_t mask;
 667        unsigned long flags;
 668        struct eerbuffer *eerb;
 669
 670        eerb = (struct eerbuffer *) filp->private_data;
 671        poll_wait(filp, &dasd_eer_read_wait_queue, ptable);
 672        spin_lock_irqsave(&bufferlock, flags);
 673        if (eerb->head != eerb->tail)
 674                mask = EPOLLIN | EPOLLRDNORM ;
 675        else
 676                mask = 0;
 677        spin_unlock_irqrestore(&bufferlock, flags);
 678        return mask;
 679}
 680
 681static const struct file_operations dasd_eer_fops = {
 682        .open           = &dasd_eer_open,
 683        .release        = &dasd_eer_close,
 684        .read           = &dasd_eer_read,
 685        .poll           = &dasd_eer_poll,
 686        .owner          = THIS_MODULE,
 687        .llseek         = noop_llseek,
 688};
 689
 690static struct miscdevice *dasd_eer_dev = NULL;
 691
 692int __init dasd_eer_init(void)
 693{
 694        int rc;
 695
 696        dasd_eer_dev = kzalloc(sizeof(*dasd_eer_dev), GFP_KERNEL);
 697        if (!dasd_eer_dev)
 698                return -ENOMEM;
 699
 700        dasd_eer_dev->minor = MISC_DYNAMIC_MINOR;
 701        dasd_eer_dev->name  = "dasd_eer";
 702        dasd_eer_dev->fops  = &dasd_eer_fops;
 703
 704        rc = misc_register(dasd_eer_dev);
 705        if (rc) {
 706                kfree(dasd_eer_dev);
 707                dasd_eer_dev = NULL;
 708                DBF_EVENT(DBF_ERR, "%s", "dasd_eer_init could not "
 709                       "register misc device");
 710                return rc;
 711        }
 712
 713        return 0;
 714}
 715
 716void dasd_eer_exit(void)
 717{
 718        if (dasd_eer_dev) {
 719                misc_deregister(dasd_eer_dev);
 720                kfree(dasd_eer_dev);
 721                dasd_eer_dev = NULL;
 722        }
 723}
 724