drivers/scsi/hosts.c

   1 /*
   2  *  hosts.c Copyright (C) 1992 Drew Eckhardt
   3  *          Copyright (C) 1993, 1994, 1995 Eric Youngdale
   4  *          Copyright (C) 2002-2003 Christoph Hellwig
   5  *
   6  *  mid to lowlevel SCSI driver interface
   7  *      Initial versions: Drew Eckhardt
   8  *      Subsequent revisions: Eric Youngdale
   9  *
  10  *  <drew@colorado.edu>
  11  *
  12  *  Jiffies wrap fixes (host->resetting), 3 Dec 1998 Andrea Arcangeli
  13  *  Added QLOGIC QLA1280 SCSI controller kernel host support.
  14  *     August 4, 1999 Fred Lewis, Intel DuPont
  15  *
  16  *  Updated to reflect the new initialization scheme for the higher
  17  *  level of scsi drivers (sd/sr/st)
  18  *  September 17, 2000 Torben Mathiasen <tmm@image.dk>
  19  *
  20  *  Restructured scsi_host lists and associated functions.
  21  *  September 04, 2002 Mike Anderson (andmike@us.ibm.com)
  22  */
  23
  24 #include <linux/module.h>
  25 #include <linux/blkdev.h>
  26 #include <linux/kernel.h>
  27 #include <linux/slab.h>
  28 #include <linux/kthread.h>
  29 #include <linux/string.h>
  30 #include <linux/mm.h>
  31 #include <linux/init.h>
  32 #include <linux/completion.h>
  33 #include <linux/transport_class.h>
  34 #include <linux/platform_device.h>
  35 #include <linux/pm_runtime.h>
  36 #include <linux/idr.h>
  37 #include <scsi/scsi_device.h>
  38 #include <scsi/scsi_host.h>
  39 #include <scsi/scsi_transport.h>
  40
  41 #include "scsi_priv.h"
  42 #include "scsi_logging.h"
  43
  44
  45 static DEFINE_IDA(host_index_ida);
  46
  47
  48 static void scsi_host_cls_release(struct device *dev)
  49 {
  50         put_device(&class_to_shost(dev)->shost_gendev);
  51 }
  52
  53 static struct class shost_class = {
  54         .name           = "scsi_host",
  55         .dev_release    = scsi_host_cls_release,
  56 };
  57
  58 /**
  59  *      scsi_host_set_state - Take the given host through the host state model.
  60  *      @shost: scsi host to change the state of.
  61  *      @state: state to change to.
  62  *
  63  *      Returns zero if unsuccessful or an error if the requested
  64  *      transition is illegal.
  65  **/
  66 int scsi_host_set_state(struct Scsi_Host *shost, enum scsi_host_state state)
  67 {
  68         enum scsi_host_state oldstate = shost->shost_state;
  69
  70         if (state == oldstate)
  71                 return 0;
  72
  73         switch (state) {
  74         case SHOST_CREATED:
  75                 /* There are no legal states that come back to
  76                  * created.  This is the manually initialised start
  77                  * state */
  78                 goto illegal;
  79
  80         case SHOST_RUNNING:
  81                 switch (oldstate) {
  82                 case SHOST_CREATED:
  83                 case SHOST_RECOVERY:
  84                         break;
  85                 default:
  86                         goto illegal;
  87                 }
  88                 break;
  89
  90         case SHOST_RECOVERY:
  91                 switch (oldstate) {
  92                 case SHOST_RUNNING:
  93                         break;
  94                 default:
  95                         goto illegal;
  96                 }
  97                 break;
  98
  99         case SHOST_CANCEL:
 100                 switch (oldstate) {
 101                 case SHOST_CREATED:
 102                 case SHOST_RUNNING:
 103                 case SHOST_CANCEL_RECOVERY:
 104                         break;
 105                 default:
 106                         goto illegal;
 107                 }
 108                 break;
 109
 110         case SHOST_DEL:
 111                 switch (oldstate) {
 112                 case SHOST_CANCEL:
 113                 case SHOST_DEL_RECOVERY:
 114                         break;
 115                 default:
 116                         goto illegal;
 117                 }
 118                 break;
 119
 120         case SHOST_CANCEL_RECOVERY:
 121                 switch (oldstate) {
 122                 case SHOST_CANCEL:
 123                 case SHOST_RECOVERY:
 124                         break;
 125                 default:
 126                         goto illegal;
 127                 }
 128                 break;
 129
 130         case SHOST_DEL_RECOVERY:
 131                 switch (oldstate) {
 132                 case SHOST_CANCEL_RECOVERY:
 133                         break;
 134                 default:
 135                         goto illegal;
 136                 }
 137                 break;
 138         }
 139         shost->shost_state = state;
 140         return 0;
 141
 142  illegal:
 143         SCSI_LOG_ERROR_RECOVERY(1,
 144                                 shost_printk(KERN_ERR, shost,
 145                                              "Illegal host state transition"
 146                                              "%s->%s\n",
 147                                              scsi_host_state_name(oldstate),
 148                                              scsi_host_state_name(state)));
 149         return -EINVAL;
 150 }
 151 EXPORT_SYMBOL(scsi_host_set_state);
 152
 153 /**
 154  * scsi_remove_host - remove a scsi host
 155  * @shost:      a pointer to a scsi host to remove
 156  **/
 157 void scsi_remove_host(struct Scsi_Host *shost)
 158 {
 159         unsigned long flags;
 160
 161         mutex_lock(&shost->scan_mutex);
 162         spin_lock_irqsave(shost->host_lock, flags);
 163         if (scsi_host_set_state(shost, SHOST_CANCEL))
 164                 if (scsi_host_set_state(shost, SHOST_CANCEL_RECOVERY)) {
 165                         spin_unlock_irqrestore(shost->host_lock, flags);
 166                         mutex_unlock(&shost->scan_mutex);
 167                         return;
 168                 }
 169         spin_unlock_irqrestore(shost->host_lock, flags);
 170
 171         scsi_autopm_get_host(shost);
 172         flush_workqueue(shost->tmf_work_q);
 173         scsi_forget_host(shost);
 174         mutex_unlock(&shost->scan_mutex);
 175         scsi_proc_host_rm(shost);
 176
 177         spin_lock_irqsave(shost->host_lock, flags);
 178         if (scsi_host_set_state(shost, SHOST_DEL))
 179                 BUG_ON(scsi_host_set_state(shost, SHOST_DEL_RECOVERY));
 180         spin_unlock_irqrestore(shost->host_lock, flags);
 181
 182         transport_unregister_device(&shost->shost_gendev);
 183         device_unregister(&shost->shost_dev);
 184         device_del(&shost->shost_gendev);
 185 }
 186 EXPORT_SYMBOL(scsi_remove_host);
 187
 188 /**
 189  * scsi_add_host_with_dma - add a scsi host with dma device
 190  * @shost:      scsi host pointer to add
 191  * @dev:        a struct device of type scsi class
 192  * @dma_dev:    dma device for the host
 193  *
 194  * Note: You rarely need to worry about this unless you're in a
 195  * virtualised host environments, so use the simpler scsi_add_host()
 196  * function instead.
 197  *
 198  * Return value:
 199  *      0 on success / != 0 for error
 200  **/
 201 int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 202                            struct device *dma_dev)
 203 {
 204         struct scsi_host_template *sht = shost->hostt;
 205         int error = -EINVAL;
 206
 207         shost_printk(KERN_INFO, shost, "%s\n",
 208                         sht->info ? sht->info(shost) : sht->name);
 209
 210         if (!shost->can_queue) {
 211                 shost_printk(KERN_ERR, shost,
 212                              "can_queue = 0 no longer supported\n");
 213                 goto fail;
 214         }
 215
 216         if (shost_use_blk_mq(shost)) {
 217                 error = scsi_mq_setup_tags(shost);
 218                 if (error)
 219                         goto fail;
 220         } else {
 221                 shost->bqt = blk_init_tags(shost->can_queue,
 222                                 shost->hostt->tag_alloc_policy);
 223                 if (!shost->bqt) {
 224                         error = -ENOMEM;
 225                         goto fail;
 226                 }
 227         }
 228
 229         /*
 230          * Note that we allocate the freelist even for the MQ case for now,
 231          * as we need a command set aside for scsi_reset_provider.  Having
 232          * the full host freelist and one command available for that is a
 233          * little heavy-handed, but avoids introducing a special allocator
 234          * just for this.  Eventually the structure of scsi_reset_provider
 235          * will need a major overhaul.
 236          */
 237         error = scsi_setup_command_freelist(shost);
 238         if (error)
 239                 goto out_destroy_tags;
 240
 241
 242         if (!shost->shost_gendev.parent)
 243                 shost->shost_gendev.parent = dev ? dev : &platform_bus;
 244         if (!dma_dev)
 245                 dma_dev = shost->shost_gendev.parent;
 246
 247         shost->dma_dev = dma_dev;
 248
 249         error = device_add(&shost->shost_gendev);
 250         if (error)
 251                 goto out_destroy_freelist;
 252
 253         /*
 254          * Increase usage count temporarily here so that calling
 255          * scsi_autopm_put_host() will trigger runtime idle if there is
 256          * nothing else preventing suspending the device.
 257          */
 258         pm_runtime_get_noresume(&shost->shost_gendev);
 259         pm_runtime_set_active(&shost->shost_gendev);
 260         pm_runtime_enable(&shost->shost_gendev);
 261         device_enable_async_suspend(&shost->shost_gendev);
 262
 263         scsi_host_set_state(shost, SHOST_RUNNING);
 264         get_device(shost->shost_gendev.parent);
 265
 266         device_enable_async_suspend(&shost->shost_dev);
 267
 268         error = device_add(&shost->shost_dev);
 269         if (error)
 270                 goto out_del_gendev;
 271
 272         get_device(&shost->shost_gendev);
 273
 274         if (shost->transportt->host_size) {
 275                 shost->shost_data = kzalloc(shost->transportt->host_size,
 276                                          GFP_KERNEL);
 277                 if (shost->shost_data == NULL) {
 278                         error = -ENOMEM;
 279                         goto out_del_dev;
 280                 }
 281         }
 282
 283         if (shost->transportt->create_work_queue) {
 284                 snprintf(shost->work_q_name, sizeof(shost->work_q_name),
 285                          "scsi_wq_%d", shost->host_no);
 286                 shost->work_q = create_singlethread_workqueue(
 287                                         shost->work_q_name);
 288                 if (!shost->work_q) {
 289                         error = -EINVAL;
 290                         goto out_free_shost_data;
 291                 }
 292         }
 293
 294         error = scsi_sysfs_add_host(shost);
 295         if (error)
 296                 goto out_destroy_host;
 297
 298         scsi_proc_host_add(shost);
 299         scsi_autopm_put_host(shost);
 300         return error;
 301
 302  out_destroy_host:
 303         if (shost->work_q)
 304                 destroy_workqueue(shost->work_q);
 305  out_free_shost_data:
 306         kfree(shost->shost_data);
 307  out_del_dev:
 308         device_del(&shost->shost_dev);
 309  out_del_gendev:
 310         device_del(&shost->shost_gendev);
 311  out_destroy_freelist:
 312         scsi_destroy_command_freelist(shost);
 313  out_destroy_tags:
 314         if (shost_use_blk_mq(shost))
 315                 scsi_mq_destroy_tags(shost);
 316  fail:
 317         return error;
 318 }
 319 EXPORT_SYMBOL(scsi_add_host_with_dma);
 320
 321 static void scsi_host_dev_release(struct device *dev)
 322 {
 323         struct Scsi_Host *shost = dev_to_shost(dev);
 324         struct device *parent = dev->parent;
 325         struct request_queue *q;
 326         void *queuedata;
 327
 328         scsi_proc_hostdir_rm(shost->hostt);
 329
 330         if (shost->tmf_work_q)
 331                 destroy_workqueue(shost->tmf_work_q);
 332         if (shost->ehandler)
 333                 kthread_stop(shost->ehandler);
 334         if (shost->work_q)
 335                 destroy_workqueue(shost->work_q);
 336         q = shost->uspace_req_q;
 337         if (q) {
 338                 queuedata = q->queuedata;
 339                 blk_cleanup_queue(q);
 340                 kfree(queuedata);
 341         }
 342
 343         if (shost->shost_state == SHOST_CREATED) {
 344                 /*
 345                  * Free the shost_dev device name here if scsi_host_alloc()
 346                  * and scsi_host_put() have been called but neither
 347                  * scsi_host_add() nor scsi_host_remove() has been called.
 348                  * This avoids that the memory allocated for the shost_dev
 349                  * name is leaked.
 350                  */
 351                 kfree(dev_name(&shost->shost_dev));
 352         }
 353
 354         scsi_destroy_command_freelist(shost);
 355         if (shost_use_blk_mq(shost)) {
 356                 if (shost->tag_set.tags)
 357                         scsi_mq_destroy_tags(shost);
 358         } else {
 359                 if (shost->bqt)
 360                         blk_free_tags(shost->bqt);
 361         }
 362
 363         kfree(shost->shost_data);
 364
 365         ida_simple_remove(&host_index_ida, shost->host_no);
 366
 367         if (parent)
 368                 put_device(parent);
 369         kfree(shost);
 370 }
 371
 372 static int shost_eh_deadline = -1;
 373
 374 module_param_named(eh_deadline, shost_eh_deadline, int, S_IRUGO|S_IWUSR);
 375 MODULE_PARM_DESC(eh_deadline,
 376                  "SCSI EH timeout in seconds (should be between 0 and 2^31-1)");
 377
 378 static struct device_type scsi_host_type = {
 379         .name =         "scsi_host",
 380         .release =      scsi_host_dev_release,
 381 };
 382
 383 /**
 384  * scsi_host_alloc - register a scsi host adapter instance.
 385  * @sht:        pointer to scsi host template
 386  * @privsize:   extra bytes to allocate for driver
 387  *
 388  * Note:
 389  *      Allocate a new Scsi_Host and perform basic initialization.
 390  *      The host is not published to the scsi midlayer until scsi_add_host
 391  *      is called.
 392  *
 393  * Return value:
 394  *      Pointer to a new Scsi_Host
 395  **/
 396 struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 397 {
 398         struct Scsi_Host *shost;
 399         gfp_t gfp_mask = GFP_KERNEL;
 400         int index;
 401
 402         if (sht->unchecked_isa_dma && privsize)
 403                 gfp_mask |= __GFP_DMA;
 404
 405         shost = kzalloc(sizeof(struct Scsi_Host) + privsize, gfp_mask);
 406         if (!shost)
 407                 return NULL;
 408
 409         shost->host_lock = &shost->default_lock;
 410         spin_lock_init(shost->host_lock);
 411         shost->shost_state = SHOST_CREATED;
 412         INIT_LIST_HEAD(&shost->__devices);
 413         INIT_LIST_HEAD(&shost->__targets);
 414         INIT_LIST_HEAD(&shost->eh_cmd_q);
 415         INIT_LIST_HEAD(&shost->starved_list);
 416         init_waitqueue_head(&shost->host_wait);
 417         mutex_init(&shost->scan_mutex);
 418
 419         index = ida_simple_get(&host_index_ida, 0, 0, GFP_KERNEL);
 420         if (index < 0)
 421                 goto fail_kfree;
 422         shost->host_no = index;
 423
 424         shost->dma_channel = 0xff;
 425
 426         /* These three are default values which can be overridden */
 427         shost->max_channel = 0;
 428         shost->max_id = 8;
 429         shost->max_lun = 8;
 430
 431         /* Give each shost a default transportt */
 432         shost->transportt = &blank_transport_template;
 433
 434         /*
 435          * All drivers right now should be able to handle 12 byte
 436          * commands.  Every so often there are requests for 16 byte
 437          * commands, but individual low-level drivers need to certify that
 438          * they actually do something sensible with such commands.
 439          */
 440         shost->max_cmd_len = 12;
 441         shost->hostt = sht;
 442         shost->this_id = sht->this_id;
 443         shost->can_queue = sht->can_queue;
 444         shost->sg_tablesize = sht->sg_tablesize;
 445         shost->sg_prot_tablesize = sht->sg_prot_tablesize;
 446         shost->cmd_per_lun = sht->cmd_per_lun;
 447         shost->unchecked_isa_dma = sht->unchecked_isa_dma;
 448         shost->use_clustering = sht->use_clustering;
 449         shost->no_write_same = sht->no_write_same;
 450
 451         if (shost_eh_deadline == -1 || !sht->eh_host_reset_handler)
 452                 shost->eh_deadline = -1;
 453         else if ((ulong) shost_eh_deadline * HZ > INT_MAX) {
 454                 shost_printk(KERN_WARNING, shost,
 455                              "eh_deadline %u too large, setting to %u\n",
 456                              shost_eh_deadline, INT_MAX / HZ);
 457                 shost->eh_deadline = INT_MAX;
 458         } else
 459                 shost->eh_deadline = shost_eh_deadline * HZ;
 460
 461         if (sht->supported_mode == MODE_UNKNOWN)
 462                 /* means we didn't set it ... default to INITIATOR */
 463                 shost->active_mode = MODE_INITIATOR;
 464         else
 465                 shost->active_mode = sht->supported_mode;
 466
 467         if (sht->max_host_blocked)
 468                 shost->max_host_blocked = sht->max_host_blocked;
 469         else
 470                 shost->max_host_blocked = SCSI_DEFAULT_HOST_BLOCKED;
 471
 472         /*
 473          * If the driver imposes no hard sector transfer limit, start at
 474          * machine infinity initially.
 475          */
 476         if (sht->max_sectors)
 477                 shost->max_sectors = sht->max_sectors;
 478         else
 479                 shost->max_sectors = SCSI_DEFAULT_MAX_SECTORS;
 480
 481         /*
 482          * assume a 4GB boundary, if not set
 483          */
 484         if (sht->dma_boundary)
 485                 shost->dma_boundary = sht->dma_boundary;
 486         else
 487                 shost->dma_boundary = 0xffffffff;
 488
 489         shost->use_blk_mq = scsi_use_blk_mq && !shost->hostt->disable_blk_mq;
 490
 491         device_initialize(&shost->shost_gendev);
 492         dev_set_name(&shost->shost_gendev, "host%d", shost->host_no);
 493         shost->shost_gendev.bus = &scsi_bus_type;
 494         shost->shost_gendev.type = &scsi_host_type;
 495
 496         device_initialize(&shost->shost_dev);
 497         shost->shost_dev.parent = &shost->shost_gendev;
 498         shost->shost_dev.class = &shost_class;
 499         dev_set_name(&shost->shost_dev, "host%d", shost->host_no);
 500         shost->shost_dev.groups = scsi_sysfs_shost_attr_groups;
 501
 502         shost->ehandler = kthread_run(scsi_error_handler, shost,
 503                         "scsi_eh_%d", shost->host_no);
 504         if (IS_ERR(shost->ehandler)) {
 505                 shost_printk(KERN_WARNING, shost,
 506                         "error handler thread failed to spawn, error = %ld\n",
 507                         PTR_ERR(shost->ehandler));
 508                 goto fail_index_remove;
 509         }
 510
 511         shost->tmf_work_q = alloc_workqueue("scsi_tmf_%d",
 512                                             WQ_UNBOUND | WQ_MEM_RECLAIM,
 513                                            1, shost->host_no);
 514         if (!shost->tmf_work_q) {
 515                 shost_printk(KERN_WARNING, shost,
 516                              "failed to create tmf workq\n");
 517                 goto fail_kthread;
 518         }
 519         scsi_proc_hostdir_add(shost->hostt);
 520         return shost;
 521
 522  fail_kthread:
 523         kthread_stop(shost->ehandler);
 524  fail_index_remove:
 525         ida_simple_remove(&host_index_ida, shost->host_no);
 526  fail_kfree:
 527         kfree(shost);
 528         return NULL;
 529 }
 530 EXPORT_SYMBOL(scsi_host_alloc);
 531
 532 struct Scsi_Host *scsi_register(struct scsi_host_template *sht, int privsize)
 533 {
 534         struct Scsi_Host *shost = scsi_host_alloc(sht, privsize);
 535
 536         if (!sht->detect) {
 537                 printk(KERN_WARNING "scsi_register() called on new-style "
 538                                     "template for driver %s\n", sht->name);
 539                 dump_stack();
 540         }
 541
 542         if (shost)
 543                 list_add_tail(&shost->sht_legacy_list, &sht->legacy_hosts);
 544         return shost;
 545 }
 546 EXPORT_SYMBOL(scsi_register);
 547
 548 void scsi_unregister(struct Scsi_Host *shost)
 549 {
 550         list_del(&shost->sht_legacy_list);
 551         scsi_host_put(shost);
 552 }
 553 EXPORT_SYMBOL(scsi_unregister);
 554
 555 static int __scsi_host_match(struct device *dev, const void *data)
 556 {
 557         struct Scsi_Host *p;
 558         const unsigned short *hostnum = data;
 559
 560         p = class_to_shost(dev);
 561         return p->host_no == *hostnum;
 562 }
 563
 564 /**
 565  * scsi_host_lookup - get a reference to a Scsi_Host by host no
 566  * @hostnum:    host number to locate
 567  *
 568  * Return value:
 569  *      A pointer to located Scsi_Host or NULL.
 570  *
 571  *      The caller must do a scsi_host_put() to drop the reference
 572  *      that scsi_host_get() took. The put_device() below dropped
 573  *      the reference from class_find_device().
 574  **/
 575 struct Scsi_Host *scsi_host_lookup(unsigned short hostnum)
 576 {
 577         struct device *cdev;
 578         struct Scsi_Host *shost = NULL;
 579
 580         cdev = class_find_device(&shost_class, NULL, &hostnum,
 581                                  __scsi_host_match);
 582         if (cdev) {
 583                 shost = scsi_host_get(class_to_shost(cdev));
 584                 put_device(cdev);
 585         }
 586         return shost;
 587 }
 588 EXPORT_SYMBOL(scsi_host_lookup);
 589
 590 /**
 591  * scsi_host_get - inc a Scsi_Host ref count
 592  * @shost:      Pointer to Scsi_Host to inc.
 593  **/
 594 struct Scsi_Host *scsi_host_get(struct Scsi_Host *shost)
 595 {
 596         if ((shost->shost_state == SHOST_DEL) ||
 597                 !get_device(&shost->shost_gendev))
 598                 return NULL;
 599         return shost;
 600 }
 601 EXPORT_SYMBOL(scsi_host_get);
 602
 603 /**
 604  * scsi_host_put - dec a Scsi_Host ref count
 605  * @shost:      Pointer to Scsi_Host to dec.
 606  **/
 607 void scsi_host_put(struct Scsi_Host *shost)
 608 {
 609         put_device(&shost->shost_gendev);
 610 }
 611 EXPORT_SYMBOL(scsi_host_put);
 612
 613 int scsi_init_hosts(void)
 614 {
 615         return class_register(&shost_class);
 616 }
 617
 618 void scsi_exit_hosts(void)
 619 {
 620         class_unregister(&shost_class);
 621         ida_destroy(&host_index_ida);
 622 }
 623
 624 int scsi_is_host_device(const struct device *dev)
 625 {
 626         return dev->type == &scsi_host_type;
 627 }
 628 EXPORT_SYMBOL(scsi_is_host_device);
 629
 630 /**
 631  * scsi_queue_work - Queue work to the Scsi_Host workqueue.
 632  * @shost:      Pointer to Scsi_Host.
 633  * @work:       Work to queue for execution.
 634  *
 635  * Return value:
 636  *      1 - work queued for execution
 637  *      0 - work is already queued
 638  *      -EINVAL - work queue doesn't exist
 639  **/
 640 int scsi_queue_work(struct Scsi_Host *shost, struct work_struct *work)
 641 {
 642         if (unlikely(!shost->work_q)) {
 643                 shost_printk(KERN_ERR, shost,
 644                         "ERROR: Scsi host '%s' attempted to queue scsi-work, "
 645                         "when no workqueue created.\n", shost->hostt->name);
 646                 dump_stack();
 647
 648                 return -EINVAL;
 649         }
 650
 651         return queue_work(shost->work_q, work);
 652 }
 653 EXPORT_SYMBOL_GPL(scsi_queue_work);
 654
 655 /**
 656  * scsi_flush_work - Flush a Scsi_Host's workqueue.
 657  * @shost:      Pointer to Scsi_Host.
 658  **/
 659 void scsi_flush_work(struct Scsi_Host *shost)
 660 {
 661         if (!shost->work_q) {
 662                 shost_printk(KERN_ERR, shost,
 663                         "ERROR: Scsi host '%s' attempted to flush scsi-work, "
 664                         "when no workqueue created.\n", shost->hostt->name);
 665                 dump_stack();
 666                 return;
 667         }
 668
 669         flush_workqueue(shost->work_q);
 670 }
 671 EXPORT_SYMBOL_GPL(scsi_flush_work);