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         /*
 250          * Increase usage count temporarily here so that calling
 251          * scsi_autopm_put_host() will trigger runtime idle if there is
 252          * nothing else preventing suspending the device.
 253          */
 254         pm_runtime_get_noresume(&shost->shost_gendev);
 255         pm_runtime_set_active(&shost->shost_gendev);
 256         pm_runtime_enable(&shost->shost_gendev);
 257         device_enable_async_suspend(&shost->shost_gendev);
 258
 259         error = device_add(&shost->shost_gendev);
 260         if (error)
 261                 goto out_destroy_freelist;
 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         get_device(&shost->shost_gendev);
 269         error = device_add(&shost->shost_dev);
 270         if (error)
 271                 goto out_del_gendev;
 272
 273         if (shost->transportt->host_size) {
 274                 shost->shost_data = kzalloc(shost->transportt->host_size,
 275                                          GFP_KERNEL);
 276                 if (shost->shost_data == NULL) {
 277                         error = -ENOMEM;
 278                         goto out_del_dev;
 279                 }
 280         }
 281
 282         if (shost->transportt->create_work_queue) {
 283                 snprintf(shost->work_q_name, sizeof(shost->work_q_name),
 284                          "scsi_wq_%d", shost->host_no);
 285                 shost->work_q = create_singlethread_workqueue(
 286                                         shost->work_q_name);
 287                 if (!shost->work_q) {
 288                         error = -EINVAL;
 289                         goto out_free_shost_data;
 290                 }
 291         }
 292
 293         error = scsi_sysfs_add_host(shost);
 294         if (error)
 295                 goto out_destroy_host;
 296
 297         scsi_proc_host_add(shost);
 298         scsi_autopm_put_host(shost);
 299         return error;
 300
 301  out_destroy_host:
 302         if (shost->work_q)
 303                 destroy_workqueue(shost->work_q);
 304  out_free_shost_data:
 305         kfree(shost->shost_data);
 306  out_del_dev:
 307         device_del(&shost->shost_dev);
 308  out_del_gendev:
 309         /*
 310          * Host state is SHOST_RUNNING so we have to explicitly release
 311          * ->shost_dev.
 312          */
 313         put_device(&shost->shost_dev);
 314         device_del(&shost->shost_gendev);
 315  out_destroy_freelist:
 316         device_disable_async_suspend(&shost->shost_gendev);
 317         pm_runtime_disable(&shost->shost_gendev);
 318         pm_runtime_set_suspended(&shost->shost_gendev);
 319         pm_runtime_put_noidle(&shost->shost_gendev);
 320         scsi_destroy_command_freelist(shost);
 321  out_destroy_tags:
 322         if (shost_use_blk_mq(shost))
 323                 scsi_mq_destroy_tags(shost);
 324  fail:
 325         return error;
 326 }
 327 EXPORT_SYMBOL(scsi_add_host_with_dma);
 328
 329 static void scsi_host_dev_release(struct device *dev)
 330 {
 331         struct Scsi_Host *shost = dev_to_shost(dev);
 332         struct device *parent = dev->parent;
 333         struct request_queue *q;
 334         void *queuedata;
 335
 336         scsi_proc_hostdir_rm(shost->hostt);
 337
 338         if (shost->tmf_work_q)
 339                 destroy_workqueue(shost->tmf_work_q);
 340         if (shost->ehandler)
 341                 kthread_stop(shost->ehandler);
 342         if (shost->work_q)
 343                 destroy_workqueue(shost->work_q);
 344         q = shost->uspace_req_q;
 345         if (q) {
 346                 queuedata = q->queuedata;
 347                 blk_cleanup_queue(q);
 348                 kfree(queuedata);
 349         }
 350
 351         if (shost->shost_state == SHOST_CREATED) {
 352                 /*
 353                  * Free the shost_dev device name here if scsi_host_alloc()
 354                  * and scsi_host_put() have been called but neither
 355                  * scsi_host_add() nor scsi_host_remove() has been called.
 356                  * This avoids that the memory allocated for the shost_dev
 357                  * name is leaked.
 358                  */
 359                 kfree(dev_name(&shost->shost_dev));
 360         }
 361
 362         scsi_destroy_command_freelist(shost);
 363         if (shost_use_blk_mq(shost)) {
 364                 if (shost->tag_set.tags)
 365                         scsi_mq_destroy_tags(shost);
 366         } else {
 367                 if (shost->bqt)
 368                         blk_free_tags(shost->bqt);
 369         }
 370
 371         kfree(shost->shost_data);
 372
 373         ida_simple_remove(&host_index_ida, shost->host_no);
 374
 375         if (shost->shost_state != SHOST_CREATED)
 376                 put_device(parent);
 377         kfree(shost);
 378 }
 379
 380 static int shost_eh_deadline = -1;
 381
 382 module_param_named(eh_deadline, shost_eh_deadline, int, S_IRUGO|S_IWUSR);
 383 MODULE_PARM_DESC(eh_deadline,
 384                  "SCSI EH timeout in seconds (should be between 0 and 2^31-1)");
 385
 386 static struct device_type scsi_host_type = {
 387         .name =         "scsi_host",
 388         .release =      scsi_host_dev_release,
 389 };
 390
 391 /**
 392  * scsi_host_alloc - register a scsi host adapter instance.
 393  * @sht:        pointer to scsi host template
 394  * @privsize:   extra bytes to allocate for driver
 395  *
 396  * Note:
 397  *      Allocate a new Scsi_Host and perform basic initialization.
 398  *      The host is not published to the scsi midlayer until scsi_add_host
 399  *      is called.
 400  *
 401  * Return value:
 402  *      Pointer to a new Scsi_Host
 403  **/
 404 struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 405 {
 406         struct Scsi_Host *shost;
 407         gfp_t gfp_mask = GFP_KERNEL;
 408         int index;
 409
 410         if (sht->unchecked_isa_dma && privsize)
 411                 gfp_mask |= __GFP_DMA;
 412
 413         shost = kzalloc(sizeof(struct Scsi_Host) + privsize, gfp_mask);
 414         if (!shost)
 415                 return NULL;
 416
 417         shost->host_lock = &shost->default_lock;
 418         spin_lock_init(shost->host_lock);
 419         shost->shost_state = SHOST_CREATED;
 420         INIT_LIST_HEAD(&shost->__devices);
 421         INIT_LIST_HEAD(&shost->__targets);
 422         INIT_LIST_HEAD(&shost->eh_cmd_q);
 423         INIT_LIST_HEAD(&shost->starved_list);
 424         init_waitqueue_head(&shost->host_wait);
 425         mutex_init(&shost->scan_mutex);
 426
 427         index = ida_simple_get(&host_index_ida, 0, 0, GFP_KERNEL);
 428         if (index < 0) {
 429                 kfree(shost);
 430                 return NULL;
 431         }
 432         shost->host_no = index;
 433
 434         shost->dma_channel = 0xff;
 435
 436         /* These three are default values which can be overridden */
 437         shost->max_channel = 0;
 438         shost->max_id = 8;
 439         shost->max_lun = 8;
 440
 441         /* Give each shost a default transportt */
 442         shost->transportt = &blank_transport_template;
 443
 444         /*
 445          * All drivers right now should be able to handle 12 byte
 446          * commands.  Every so often there are requests for 16 byte
 447          * commands, but individual low-level drivers need to certify that
 448          * they actually do something sensible with such commands.
 449          */
 450         shost->max_cmd_len = 12;
 451         shost->hostt = sht;
 452         shost->this_id = sht->this_id;
 453         shost->can_queue = sht->can_queue;
 454         shost->sg_tablesize = sht->sg_tablesize;
 455         shost->sg_prot_tablesize = sht->sg_prot_tablesize;
 456         shost->cmd_per_lun = sht->cmd_per_lun;
 457         shost->unchecked_isa_dma = sht->unchecked_isa_dma;
 458         shost->use_clustering = sht->use_clustering;
 459         shost->no_write_same = sht->no_write_same;
 460
 461         if (shost_eh_deadline == -1 || !sht->eh_host_reset_handler)
 462                 shost->eh_deadline = -1;
 463         else if ((ulong) shost_eh_deadline * HZ > INT_MAX) {
 464                 shost_printk(KERN_WARNING, shost,
 465                              "eh_deadline %u too large, setting to %u\n",
 466                              shost_eh_deadline, INT_MAX / HZ);
 467                 shost->eh_deadline = INT_MAX;
 468         } else
 469                 shost->eh_deadline = shost_eh_deadline * HZ;
 470
 471         if (sht->supported_mode == MODE_UNKNOWN)
 472                 /* means we didn't set it ... default to INITIATOR */
 473                 shost->active_mode = MODE_INITIATOR;
 474         else
 475                 shost->active_mode = sht->supported_mode;
 476
 477         if (sht->max_host_blocked)
 478                 shost->max_host_blocked = sht->max_host_blocked;
 479         else
 480                 shost->max_host_blocked = SCSI_DEFAULT_HOST_BLOCKED;
 481
 482         /*
 483          * If the driver imposes no hard sector transfer limit, start at
 484          * machine infinity initially.
 485          */
 486         if (sht->max_sectors)
 487                 shost->max_sectors = sht->max_sectors;
 488         else
 489                 shost->max_sectors = SCSI_DEFAULT_MAX_SECTORS;
 490
 491         /*
 492          * assume a 4GB boundary, if not set
 493          */
 494         if (sht->dma_boundary)
 495                 shost->dma_boundary = sht->dma_boundary;
 496         else
 497                 shost->dma_boundary = 0xffffffff;
 498
 499         shost->use_blk_mq = scsi_use_blk_mq;
 500
 501         device_initialize(&shost->shost_gendev);
 502         dev_set_name(&shost->shost_gendev, "host%d", shost->host_no);
 503         shost->shost_gendev.bus = &scsi_bus_type;
 504         shost->shost_gendev.type = &scsi_host_type;
 505
 506         device_initialize(&shost->shost_dev);
 507         shost->shost_dev.parent = &shost->shost_gendev;
 508         shost->shost_dev.class = &shost_class;
 509         dev_set_name(&shost->shost_dev, "host%d", shost->host_no);
 510         shost->shost_dev.groups = scsi_sysfs_shost_attr_groups;
 511
 512         shost->ehandler = kthread_run(scsi_error_handler, shost,
 513                         "scsi_eh_%d", shost->host_no);
 514         if (IS_ERR(shost->ehandler)) {
 515                 shost_printk(KERN_WARNING, shost,
 516                         "error handler thread failed to spawn, error = %ld\n",
 517                         PTR_ERR(shost->ehandler));
 518                 shost->ehandler = NULL;
 519                 goto fail;
 520         }
 521
 522         shost->tmf_work_q = alloc_workqueue("scsi_tmf_%d",
 523                                             WQ_UNBOUND | WQ_MEM_RECLAIM,
 524                                            1, shost->host_no);
 525         if (!shost->tmf_work_q) {
 526                 shost_printk(KERN_WARNING, shost,
 527                              "failed to create tmf workq\n");
 528                 goto fail;
 529         }
 530         scsi_proc_hostdir_add(shost->hostt);
 531         return shost;
 532  fail:
 533         /*
 534          * Host state is still SHOST_CREATED and that is enough to release
 535          * ->shost_gendev. scsi_host_dev_release() will free
 536          * dev_name(&shost->shost_dev).
 537          */
 538         put_device(&shost->shost_gendev);
 539
 540         return NULL;
 541 }
 542 EXPORT_SYMBOL(scsi_host_alloc);
 543
 544 struct Scsi_Host *scsi_register(struct scsi_host_template *sht, int privsize)
 545 {
 546         struct Scsi_Host *shost = scsi_host_alloc(sht, privsize);
 547
 548         if (!sht->detect) {
 549                 printk(KERN_WARNING "scsi_register() called on new-style "
 550                                     "template for driver %s\n", sht->name);
 551                 dump_stack();
 552         }
 553
 554         if (shost)
 555                 list_add_tail(&shost->sht_legacy_list, &sht->legacy_hosts);
 556         return shost;
 557 }
 558 EXPORT_SYMBOL(scsi_register);
 559
 560 void scsi_unregister(struct Scsi_Host *shost)
 561 {
 562         list_del(&shost->sht_legacy_list);
 563         scsi_host_put(shost);
 564 }
 565 EXPORT_SYMBOL(scsi_unregister);
 566
 567 static int __scsi_host_match(struct device *dev, const void *data)
 568 {
 569         struct Scsi_Host *p;
 570         const unsigned short *hostnum = data;
 571
 572         p = class_to_shost(dev);
 573         return p->host_no == *hostnum;
 574 }
 575
 576 /**
 577  * scsi_host_lookup - get a reference to a Scsi_Host by host no
 578  * @hostnum:    host number to locate
 579  *
 580  * Return value:
 581  *      A pointer to located Scsi_Host or NULL.
 582  *
 583  *      The caller must do a scsi_host_put() to drop the reference
 584  *      that scsi_host_get() took. The put_device() below dropped
 585  *      the reference from class_find_device().
 586  **/
 587 struct Scsi_Host *scsi_host_lookup(unsigned short hostnum)
 588 {
 589         struct device *cdev;
 590         struct Scsi_Host *shost = NULL;
 591
 592         cdev = class_find_device(&shost_class, NULL, &hostnum,
 593                                  __scsi_host_match);
 594         if (cdev) {
 595                 shost = scsi_host_get(class_to_shost(cdev));
 596                 put_device(cdev);
 597         }
 598         return shost;
 599 }
 600 EXPORT_SYMBOL(scsi_host_lookup);
 601
 602 /**
 603  * scsi_host_get - inc a Scsi_Host ref count
 604  * @shost:      Pointer to Scsi_Host to inc.
 605  **/
 606 struct Scsi_Host *scsi_host_get(struct Scsi_Host *shost)
 607 {
 608         if ((shost->shost_state == SHOST_DEL) ||
 609                 !get_device(&shost->shost_gendev))
 610                 return NULL;
 611         return shost;
 612 }
 613 EXPORT_SYMBOL(scsi_host_get);
 614
 615 /**
 616  * scsi_host_put - dec a Scsi_Host ref count
 617  * @shost:      Pointer to Scsi_Host to dec.
 618  **/
 619 void scsi_host_put(struct Scsi_Host *shost)
 620 {
 621         put_device(&shost->shost_gendev);
 622 }
 623 EXPORT_SYMBOL(scsi_host_put);
 624
 625 int scsi_init_hosts(void)
 626 {
 627         return class_register(&shost_class);
 628 }
 629
 630 void scsi_exit_hosts(void)
 631 {
 632         class_unregister(&shost_class);
 633         ida_destroy(&host_index_ida);
 634 }
 635
 636 int scsi_is_host_device(const struct device *dev)
 637 {
 638         return dev->type == &scsi_host_type;
 639 }
 640 EXPORT_SYMBOL(scsi_is_host_device);
 641
 642 /**
 643  * scsi_queue_work - Queue work to the Scsi_Host workqueue.
 644  * @shost:      Pointer to Scsi_Host.
 645  * @work:       Work to queue for execution.
 646  *
 647  * Return value:
 648  *      1 - work queued for execution
 649  *      0 - work is already queued
 650  *      -EINVAL - work queue doesn't exist
 651  **/
 652 int scsi_queue_work(struct Scsi_Host *shost, struct work_struct *work)
 653 {
 654         if (unlikely(!shost->work_q)) {
 655                 shost_printk(KERN_ERR, shost,
 656                         "ERROR: Scsi host '%s' attempted to queue scsi-work, "
 657                         "when no workqueue created.\n", shost->hostt->name);
 658                 dump_stack();
 659
 660                 return -EINVAL;
 661         }
 662
 663         return queue_work(shost->work_q, work);
 664 }
 665 EXPORT_SYMBOL_GPL(scsi_queue_work);
 666
 667 /**
 668  * scsi_flush_work - Flush a Scsi_Host's workqueue.
 669  * @shost:      Pointer to Scsi_Host.
 670  **/
 671 void scsi_flush_work(struct Scsi_Host *shost)
 672 {
 673         if (!shost->work_q) {
 674                 shost_printk(KERN_ERR, shost,
 675                         "ERROR: Scsi host '%s' attempted to flush scsi-work, "
 676                         "when no workqueue created.\n", shost->hostt->name);
 677                 dump_stack();
 678                 return;
 679         }
 680
 681         flush_workqueue(shost->work_q);
 682 }
 683 EXPORT_SYMBOL_GPL(scsi_flush_work);