drivers/scsi/scsi_lib.c

   1 /*
   2  *  scsi_lib.c Copyright (C) 1999 Eric Youngdale
   3  *
   4  *  SCSI queueing library.
   5  *      Initial versions: Eric Youngdale (eric@andante.org).
   6  *                        Based upon conversations with large numbers
   7  *                        of people at Linux Expo.
   8  */
   9
  10 #include <linux/bio.h>
  11 #include <linux/blkdev.h>
  12 #include <linux/completion.h>
  13 #include <linux/kernel.h>
  14 #include <linux/mempool.h>
  15 #include <linux/slab.h>
  16 #include <linux/init.h>
  17 #include <linux/pci.h>
  18 #include <linux/delay.h>
  19 #include <linux/hardirq.h>
  20
  21 #include <scsi/scsi.h>
  22 #include <scsi/scsi_cmnd.h>
  23 #include <scsi/scsi_dbg.h>
  24 #include <scsi/scsi_device.h>
  25 #include <scsi/scsi_driver.h>
  26 #include <scsi/scsi_eh.h>
  27 #include <scsi/scsi_host.h>
  28
  29 #include "scsi_priv.h"
  30 #include "scsi_logging.h"
  31
  32
  33 #define SG_MEMPOOL_NR           ARRAY_SIZE(scsi_sg_pools)
  34 #define SG_MEMPOOL_SIZE         32
  35
  36 struct scsi_host_sg_pool {
  37         size_t          size;
  38         char            *name;
  39         struct kmem_cache       *slab;
  40         mempool_t       *pool;
  41 };
  42
  43 #if (SCSI_MAX_PHYS_SEGMENTS < 32)
  44 #error SCSI_MAX_PHYS_SEGMENTS is too small
  45 #endif
  46
  47 #define SP(x) { x, "sgpool-" #x }
  48 static struct scsi_host_sg_pool scsi_sg_pools[] = {
  49         SP(8),
  50         SP(16),
  51         SP(32),
  52 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
  53         SP(64),
  54 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
  55         SP(128),
  56 #if (SCSI_MAX_PHYS_SEGMENTS > 128)
  57         SP(256),
  58 #if (SCSI_MAX_PHYS_SEGMENTS > 256)
  59 #error SCSI_MAX_PHYS_SEGMENTS is too large
  60 #endif
  61 #endif
  62 #endif
  63 #endif
  64 };
  65 #undef SP
  66
  67 static void scsi_run_queue(struct request_queue *q);
  68
  69 /*
  70  * Function:    scsi_unprep_request()
  71  *
  72  * Purpose:     Remove all preparation done for a request, including its
  73  *              associated scsi_cmnd, so that it can be requeued.
  74  *
  75  * Arguments:   req     - request to unprepare
  76  *
  77  * Lock status: Assumed that no locks are held upon entry.
  78  *
  79  * Returns:     Nothing.
  80  */
  81 static void scsi_unprep_request(struct request *req)
  82 {
  83         struct scsi_cmnd *cmd = req->special;
  84
  85         req->cmd_flags &= ~REQ_DONTPREP;
  86         req->special = NULL;
  87
  88         scsi_put_command(cmd);
  89 }
  90
  91 /*
  92  * Function:    scsi_queue_insert()
  93  *
  94  * Purpose:     Insert a command in the midlevel queue.
  95  *
  96  * Arguments:   cmd    - command that we are adding to queue.
  97  *              reason - why we are inserting command to queue.
  98  *
  99  * Lock status: Assumed that lock is not held upon entry.
 100  *
 101  * Returns:     Nothing.
 102  *
 103  * Notes:       We do this for one of two cases.  Either the host is busy
 104  *              and it cannot accept any more commands for the time being,
 105  *              or the device returned QUEUE_FULL and can accept no more
 106  *              commands.
 107  * Notes:       This could be called either from an interrupt context or a
 108  *              normal process context.
 109  */
 110 int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
 111 {
 112         struct Scsi_Host *host = cmd->device->host;
 113         struct scsi_device *device = cmd->device;
 114         struct request_queue *q = device->request_queue;
 115         unsigned long flags;
 116
 117         SCSI_LOG_MLQUEUE(1,
 118                  printk("Inserting command %p into mlqueue\n", cmd));
 119
 120         /*
 121          * Set the appropriate busy bit for the device/host.
 122          *
 123          * If the host/device isn't busy, assume that something actually
 124          * completed, and that we should be able to queue a command now.
 125          *
 126          * Note that the prior mid-layer assumption that any host could
 127          * always queue at least one command is now broken.  The mid-layer
 128          * will implement a user specifiable stall (see
 129          * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
 130          * if a command is requeued with no other commands outstanding
 131          * either for the device or for the host.
 132          */
 133         if (reason == SCSI_MLQUEUE_HOST_BUSY)
 134                 host->host_blocked = host->max_host_blocked;
 135         else if (reason == SCSI_MLQUEUE_DEVICE_BUSY)
 136                 device->device_blocked = device->max_device_blocked;
 137
 138         /*
 139          * Decrement the counters, since these commands are no longer
 140          * active on the host/device.
 141          */
 142         scsi_device_unbusy(device);
 143
 144         /*
 145          * Requeue this command.  It will go before all other commands
 146          * that are already in the queue.
 147          *
 148          * NOTE: there is magic here about the way the queue is plugged if
 149          * we have no outstanding commands.
 150          *
 151          * Although we *don't* plug the queue, we call the request
 152          * function.  The SCSI request function detects the blocked condition
 153          * and plugs the queue appropriately.
 154          */
 155         spin_lock_irqsave(q->queue_lock, flags);
 156         blk_requeue_request(q, cmd->request);
 157         spin_unlock_irqrestore(q->queue_lock, flags);
 158
 159         scsi_run_queue(q);
 160
 161         return 0;
 162 }
 163
 164 /**
 165  * scsi_execute - insert request and wait for the result
 166  * @sdev:       scsi device
 167  * @cmd:        scsi command
 168  * @data_direction: data direction
 169  * @buffer:     data buffer
 170  * @bufflen:    len of buffer
 171  * @sense:      optional sense buffer
 172  * @timeout:    request timeout in seconds
 173  * @retries:    number of times to retry request
 174  * @flags:      or into request flags;
 175  *
 176  * returns the req->errors value which is the the scsi_cmnd result
 177  * field.
 178  **/
 179 int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
 180                  int data_direction, void *buffer, unsigned bufflen,
 181                  unsigned char *sense, int timeout, int retries, int flags)
 182 {
 183         struct request *req;
 184         int write = (data_direction == DMA_TO_DEVICE);
 185         int ret = DRIVER_ERROR << 24;
 186
 187         req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
 188
 189         if (bufflen &&  blk_rq_map_kern(sdev->request_queue, req,
 190                                         buffer, bufflen, __GFP_WAIT))
 191                 goto out;
 192
 193         req->cmd_len = COMMAND_SIZE(cmd[0]);
 194         memcpy(req->cmd, cmd, req->cmd_len);
 195         req->sense = sense;
 196         req->sense_len = 0;
 197         req->retries = retries;
 198         req->timeout = timeout;
 199         req->cmd_type = REQ_TYPE_BLOCK_PC;
 200         req->cmd_flags |= flags | REQ_QUIET | REQ_PREEMPT;
 201
 202         /*
 203          * head injection *required* here otherwise quiesce won't work
 204          */
 205         blk_execute_rq(req->q, NULL, req, 1);
 206
 207         ret = req->errors;
 208  out:
 209         blk_put_request(req);
 210
 211         return ret;
 212 }
 213 EXPORT_SYMBOL(scsi_execute);
 214
 215
 216 int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
 217                      int data_direction, void *buffer, unsigned bufflen,
 218                      struct scsi_sense_hdr *sshdr, int timeout, int retries)
 219 {
 220         char *sense = NULL;
 221         int result;
 222
 223         if (sshdr) {
 224                 sense = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
 225                 if (!sense)
 226                         return DRIVER_ERROR << 24;
 227         }
 228         result = scsi_execute(sdev, cmd, data_direction, buffer, bufflen,
 229                               sense, timeout, retries, 0);
 230         if (sshdr)
 231                 scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, sshdr);
 232
 233         kfree(sense);
 234         return result;
 235 }
 236 EXPORT_SYMBOL(scsi_execute_req);
 237
 238 struct scsi_io_context {
 239         void *data;
 240         void (*done)(void *data, char *sense, int result, int resid);
 241         char sense[SCSI_SENSE_BUFFERSIZE];
 242 };
 243
 244 static struct kmem_cache *scsi_io_context_cache;
 245
 246 static void scsi_end_async(struct request *req, int uptodate)
 247 {
 248         struct scsi_io_context *sioc = req->end_io_data;
 249
 250         if (sioc->done)
 251                 sioc->done(sioc->data, sioc->sense, req->errors, req->data_len);
 252
 253         kmem_cache_free(scsi_io_context_cache, sioc);
 254         __blk_put_request(req->q, req);
 255 }
 256
 257 static int scsi_merge_bio(struct request *rq, struct bio *bio)
 258 {
 259         struct request_queue *q = rq->q;
 260
 261         bio->bi_flags &= ~(1 << BIO_SEG_VALID);
 262         if (rq_data_dir(rq) == WRITE)
 263                 bio->bi_rw |= (1 << BIO_RW);
 264         blk_queue_bounce(q, &bio);
 265
 266         if (!rq->bio)
 267                 blk_rq_bio_prep(q, rq, bio);
 268         else if (!ll_back_merge_fn(q, rq, bio))
 269                 return -EINVAL;
 270         else {
 271                 rq->biotail->bi_next = bio;
 272                 rq->biotail = bio;
 273         }
 274
 275         return 0;
 276 }
 277
 278 static int scsi_bi_endio(struct bio *bio, unsigned int bytes_done, int error)
 279 {
 280         if (bio->bi_size)
 281                 return 1;
 282
 283         bio_put(bio);
 284         return 0;
 285 }
 286
 287 /**
 288  * scsi_req_map_sg - map a scatterlist into a request
 289  * @rq:         request to fill
 290  * @sg:         scatterlist
 291  * @nsegs:      number of elements
 292  * @bufflen:    len of buffer
 293  * @gfp:        memory allocation flags
 294  *
 295  * scsi_req_map_sg maps a scatterlist into a request so that the
 296  * request can be sent to the block layer. We do not trust the scatterlist
 297  * sent to use, as some ULDs use that struct to only organize the pages.
 298  */
 299 static int scsi_req_map_sg(struct request *rq, struct scatterlist *sgl,
 300                            int nsegs, unsigned bufflen, gfp_t gfp)
 301 {
 302         struct request_queue *q = rq->q;
 303         int nr_pages = (bufflen + sgl[0].offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
 304         unsigned int data_len = 0, len, bytes, off;
 305         struct page *page;
 306         struct bio *bio = NULL;
 307         int i, err, nr_vecs = 0;
 308
 309         for (i = 0; i < nsegs; i++) {
 310                 page = sgl[i].page;
 311                 off = sgl[i].offset;
 312                 len = sgl[i].length;
 313                 data_len += len;
 314
 315                 while (len > 0) {
 316                         bytes = min_t(unsigned int, len, PAGE_SIZE - off);
 317
 318                         if (!bio) {
 319                                 nr_vecs = min_t(int, BIO_MAX_PAGES, nr_pages);
 320                                 nr_pages -= nr_vecs;
 321
 322                                 bio = bio_alloc(gfp, nr_vecs);
 323                                 if (!bio) {
 324                                         err = -ENOMEM;
 325                                         goto free_bios;
 326                                 }
 327                                 bio->bi_end_io = scsi_bi_endio;
 328                         }
 329
 330                         if (bio_add_pc_page(q, bio, page, bytes, off) !=
 331                             bytes) {
 332                                 bio_put(bio);
 333                                 err = -EINVAL;
 334                                 goto free_bios;
 335                         }
 336
 337                         if (bio->bi_vcnt >= nr_vecs) {
 338                                 err = scsi_merge_bio(rq, bio);
 339                                 if (err) {
 340                                         bio_endio(bio, bio->bi_size, 0);
 341                                         goto free_bios;
 342                                 }
 343                                 bio = NULL;
 344                         }
 345
 346                         page++;
 347                         len -= bytes;
 348                         off = 0;
 349                 }
 350         }
 351
 352         rq->buffer = rq->data = NULL;
 353         rq->data_len = data_len;
 354         return 0;
 355
 356 free_bios:
 357         while ((bio = rq->bio) != NULL) {
 358                 rq->bio = bio->bi_next;
 359                 /*
 360                  * call endio instead of bio_put incase it was bounced
 361                  */
 362                 bio_endio(bio, bio->bi_size, 0);
 363         }
 364
 365         return err;
 366 }
 367
 368 /**
 369  * scsi_execute_async - insert request
 370  * @sdev:       scsi device
 371  * @cmd:        scsi command
 372  * @cmd_len:    length of scsi cdb
 373  * @data_direction: data direction
 374  * @buffer:     data buffer (this can be a kernel buffer or scatterlist)
 375  * @bufflen:    len of buffer
 376  * @use_sg:     if buffer is a scatterlist this is the number of elements
 377  * @timeout:    request timeout in seconds
 378  * @retries:    number of times to retry request
 379  * @flags:      or into request flags
 380  **/
 381 int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
 382                        int cmd_len, int data_direction, void *buffer, unsigned bufflen,
 383                        int use_sg, int timeout, int retries, void *privdata,
 384                        void (*done)(void *, char *, int, int), gfp_t gfp)
 385 {
 386         struct request *req;
 387         struct scsi_io_context *sioc;
 388         int err = 0;
 389         int write = (data_direction == DMA_TO_DEVICE);
 390
 391         sioc = kmem_cache_zalloc(scsi_io_context_cache, gfp);
 392         if (!sioc)
 393                 return DRIVER_ERROR << 24;
 394
 395         req = blk_get_request(sdev->request_queue, write, gfp);
 396         if (!req)
 397                 goto free_sense;
 398         req->cmd_type = REQ_TYPE_BLOCK_PC;
 399         req->cmd_flags |= REQ_QUIET;
 400
 401         if (use_sg)
 402                 err = scsi_req_map_sg(req, buffer, use_sg, bufflen, gfp);
 403         else if (bufflen)
 404                 err = blk_rq_map_kern(req->q, req, buffer, bufflen, gfp);
 405
 406         if (err)
 407                 goto free_req;
 408
 409         req->cmd_len = cmd_len;
 410         memset(req->cmd, 0, BLK_MAX_CDB); /* ATAPI hates garbage after CDB */
 411         memcpy(req->cmd, cmd, req->cmd_len);
 412         req->sense = sioc->sense;
 413         req->sense_len = 0;
 414         req->timeout = timeout;
 415         req->retries = retries;
 416         req->end_io_data = sioc;
 417
 418         sioc->data = privdata;
 419         sioc->done = done;
 420
 421         blk_execute_rq_nowait(req->q, NULL, req, 1, scsi_end_async);
 422         return 0;
 423
 424 free_req:
 425         blk_put_request(req);
 426 free_sense:
 427         kmem_cache_free(scsi_io_context_cache, sioc);
 428         return DRIVER_ERROR << 24;
 429 }
 430 EXPORT_SYMBOL_GPL(scsi_execute_async);
 431
 432 /*
 433  * Function:    scsi_init_cmd_errh()
 434  *
 435  * Purpose:     Initialize cmd fields related to error handling.
 436  *
 437  * Arguments:   cmd     - command that is ready to be queued.
 438  *
 439  * Notes:       This function has the job of initializing a number of
 440  *              fields related to error handling.   Typically this will
 441  *              be called once for each command, as required.
 442  */
 443 static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
 444 {
 445         cmd->serial_number = 0;
 446         memset(cmd->sense_buffer, 0, sizeof cmd->sense_buffer);
 447         if (cmd->cmd_len == 0)
 448                 cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);
 449 }
 450
 451 void scsi_device_unbusy(struct scsi_device *sdev)
 452 {
 453         struct Scsi_Host *shost = sdev->host;
 454         unsigned long flags;
 455
 456         spin_lock_irqsave(shost->host_lock, flags);
 457         shost->host_busy--;
 458         if (unlikely(scsi_host_in_recovery(shost) &&
 459                      (shost->host_failed || shost->host_eh_scheduled)))
 460                 scsi_eh_wakeup(shost);
 461         spin_unlock(shost->host_lock);
 462         spin_lock(sdev->request_queue->queue_lock);
 463         sdev->device_busy--;
 464         spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
 465 }
 466
 467 /*
 468  * Called for single_lun devices on IO completion. Clear starget_sdev_user,
 469  * and call blk_run_queue for all the scsi_devices on the target -
 470  * including current_sdev first.
 471  *
 472  * Called with *no* scsi locks held.
 473  */
 474 static void scsi_single_lun_run(struct scsi_device *current_sdev)
 475 {
 476         struct Scsi_Host *shost = current_sdev->host;
 477         struct scsi_device *sdev, *tmp;
 478         struct scsi_target *starget = scsi_target(current_sdev);
 479         unsigned long flags;
 480
 481         spin_lock_irqsave(shost->host_lock, flags);
 482         starget->starget_sdev_user = NULL;
 483         spin_unlock_irqrestore(shost->host_lock, flags);
 484
 485         /*
 486          * Call blk_run_queue for all LUNs on the target, starting with
 487          * current_sdev. We race with others (to set starget_sdev_user),
 488          * but in most cases, we will be first. Ideally, each LU on the
 489          * target would get some limited time or requests on the target.
 490          */
 491         blk_run_queue(current_sdev->request_queue);
 492
 493         spin_lock_irqsave(shost->host_lock, flags);
 494         if (starget->starget_sdev_user)
 495                 goto out;
 496         list_for_each_entry_safe(sdev, tmp, &starget->devices,
 497                         same_target_siblings) {
 498                 if (sdev == current_sdev)
 499                         continue;
 500                 if (scsi_device_get(sdev))
 501                         continue;
 502
 503                 spin_unlock_irqrestore(shost->host_lock, flags);
 504                 blk_run_queue(sdev->request_queue);
 505                 spin_lock_irqsave(shost->host_lock, flags);
 506
 507                 scsi_device_put(sdev);
 508         }
 509  out:
 510         spin_unlock_irqrestore(shost->host_lock, flags);
 511 }
 512
 513 /*
 514  * Function:    scsi_run_queue()
 515  *
 516  * Purpose:     Select a proper request queue to serve next
 517  *
 518  * Arguments:   q       - last request's queue
 519  *
 520  * Returns:     Nothing
 521  *
 522  * Notes:       The previous command was completely finished, start
 523  *              a new one if possible.
 524  */
 525 static void scsi_run_queue(struct request_queue *q)
 526 {
 527         struct scsi_device *sdev = q->queuedata;
 528         struct Scsi_Host *shost = sdev->host;
 529         unsigned long flags;
 530
 531         if (sdev->single_lun)
 532                 scsi_single_lun_run(sdev);
 533
 534         spin_lock_irqsave(shost->host_lock, flags);
 535         while (!list_empty(&shost->starved_list) &&
 536                !shost->host_blocked && !shost->host_self_blocked &&
 537                 !((shost->can_queue > 0) &&
 538                   (shost->host_busy >= shost->can_queue))) {
 539                 /*
 540                  * As long as shost is accepting commands and we have
 541                  * starved queues, call blk_run_queue. scsi_request_fn
 542                  * drops the queue_lock and can add us back to the
 543                  * starved_list.
 544                  *
 545                  * host_lock protects the starved_list and starved_entry.
 546                  * scsi_request_fn must get the host_lock before checking
 547                  * or modifying starved_list or starved_entry.
 548                  */
 549                 sdev = list_entry(shost->starved_list.next,
 550                                           struct scsi_device, starved_entry);
 551                 list_del_init(&sdev->starved_entry);
 552                 spin_unlock_irqrestore(shost->host_lock, flags);
 553
 554
 555                 if (test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) &&
 556                     !test_and_set_bit(QUEUE_FLAG_REENTER,
 557                                       &sdev->request_queue->queue_flags)) {
 558                         blk_run_queue(sdev->request_queue);
 559                         clear_bit(QUEUE_FLAG_REENTER,
 560                                   &sdev->request_queue->queue_flags);
 561                 } else
 562                         blk_run_queue(sdev->request_queue);
 563
 564                 spin_lock_irqsave(shost->host_lock, flags);
 565                 if (unlikely(!list_empty(&sdev->starved_entry)))
 566                         /*
 567                          * sdev lost a race, and was put back on the
 568                          * starved list. This is unlikely but without this
 569                          * in theory we could loop forever.
 570                          */
 571                         break;
 572         }
 573         spin_unlock_irqrestore(shost->host_lock, flags);
 574
 575         blk_run_queue(q);
 576 }
 577
 578 /*
 579  * Function:    scsi_requeue_command()
 580  *
 581  * Purpose:     Handle post-processing of completed commands.
 582  *
 583  * Arguments:   q       - queue to operate on
 584  *              cmd     - command that may need to be requeued.
 585  *
 586  * Returns:     Nothing
 587  *
 588  * Notes:       After command completion, there may be blocks left
 589  *              over which weren't finished by the previous command
 590  *              this can be for a number of reasons - the main one is
 591  *              I/O errors in the middle of the request, in which case
 592  *              we need to request the blocks that come after the bad
 593  *              sector.
 594  * Notes:       Upon return, cmd is a stale pointer.
 595  */
 596 static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
 597 {
 598         struct request *req = cmd->request;
 599         unsigned long flags;
 600
 601         scsi_unprep_request(req);
 602         spin_lock_irqsave(q->queue_lock, flags);
 603         blk_requeue_request(q, req);
 604         spin_unlock_irqrestore(q->queue_lock, flags);
 605
 606         scsi_run_queue(q);
 607 }
 608
 609 void scsi_next_command(struct scsi_cmnd *cmd)
 610 {
 611         struct scsi_device *sdev = cmd->device;
 612         struct request_queue *q = sdev->request_queue;
 613
 614         /* need to hold a reference on the device before we let go of the cmd */
 615         get_device(&sdev->sdev_gendev);
 616
 617         scsi_put_command(cmd);
 618         scsi_run_queue(q);
 619
 620         /* ok to remove device now */
 621         put_device(&sdev->sdev_gendev);
 622 }
 623
 624 void scsi_run_host_queues(struct Scsi_Host *shost)
 625 {
 626         struct scsi_device *sdev;
 627
 628         shost_for_each_device(sdev, shost)
 629                 scsi_run_queue(sdev->request_queue);
 630 }
 631
 632 /*
 633  * Function:    scsi_end_request()
 634  *
 635  * Purpose:     Post-processing of completed commands (usually invoked at end
 636  *              of upper level post-processing and scsi_io_completion).
 637  *
 638  * Arguments:   cmd      - command that is complete.
 639  *              uptodate - 1 if I/O indicates success, <= 0 for I/O error.
 640  *              bytes    - number of bytes of completed I/O
 641  *              requeue  - indicates whether we should requeue leftovers.
 642  *
 643  * Lock status: Assumed that lock is not held upon entry.
 644  *
 645  * Returns:     cmd if requeue required, NULL otherwise.
 646  *
 647  * Notes:       This is called for block device requests in order to
 648  *              mark some number of sectors as complete.
 649  *
 650  *              We are guaranteeing that the request queue will be goosed
 651  *              at some point during this call.
 652  * Notes:       If cmd was requeued, upon return it will be a stale pointer.
 653  */
 654 static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int uptodate,
 655                                           int bytes, int requeue)
 656 {
 657         request_queue_t *q = cmd->device->request_queue;
 658         struct request *req = cmd->request;
 659         unsigned long flags;
 660
 661         /*
 662          * If there are blocks left over at the end, set up the command
 663          * to queue the remainder of them.
 664          */
 665         if (end_that_request_chunk(req, uptodate, bytes)) {
 666                 int leftover = (req->hard_nr_sectors << 9);
 667
 668                 if (blk_pc_request(req))
 669                         leftover = req->data_len;
 670
 671                 /* kill remainder if no retrys */
 672                 if (!uptodate && blk_noretry_request(req))
 673                         end_that_request_chunk(req, 0, leftover);
 674                 else {
 675                         if (requeue) {
 676                                 /*
 677                                  * Bleah.  Leftovers again.  Stick the
 678                                  * leftovers in the front of the
 679                                  * queue, and goose the queue again.
 680                                  */
 681                                 scsi_requeue_command(q, cmd);
 682                                 cmd = NULL;
 683                         }
 684                         return cmd;
 685                 }
 686         }
 687
 688         add_disk_randomness(req->rq_disk);
 689
 690         spin_lock_irqsave(q->queue_lock, flags);
 691         if (blk_rq_tagged(req))
 692                 blk_queue_end_tag(q, req);
 693         end_that_request_last(req, uptodate);
 694         spin_unlock_irqrestore(q->queue_lock, flags);
 695
 696         /*
 697          * This will goose the queue request function at the end, so we don't
 698          * need to worry about launching another command.
 699          */
 700         scsi_next_command(cmd);
 701         return NULL;
 702 }
 703
 704 struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
 705 {
 706         struct scsi_host_sg_pool *sgp;
 707         struct scatterlist *sgl;
 708
 709         BUG_ON(!cmd->use_sg);
 710
 711         switch (cmd->use_sg) {
 712         case 1 ... 8:
 713                 cmd->sglist_len = 0;
 714                 break;
 715         case 9 ... 16:
 716                 cmd->sglist_len = 1;
 717                 break;
 718         case 17 ... 32:
 719                 cmd->sglist_len = 2;
 720                 break;
 721 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
 722         case 33 ... 64:
 723                 cmd->sglist_len = 3;
 724                 break;
 725 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
 726         case 65 ... 128:
 727                 cmd->sglist_len = 4;
 728                 break;
 729 #if (SCSI_MAX_PHYS_SEGMENTS  > 128)
 730         case 129 ... 256:
 731                 cmd->sglist_len = 5;
 732                 break;
 733 #endif
 734 #endif
 735 #endif
 736         default:
 737                 return NULL;
 738         }
 739
 740         sgp = scsi_sg_pools + cmd->sglist_len;
 741         sgl = mempool_alloc(sgp->pool, gfp_mask);
 742         return sgl;
 743 }
 744
 745 EXPORT_SYMBOL(scsi_alloc_sgtable);
 746
 747 void scsi_free_sgtable(struct scatterlist *sgl, int index)
 748 {
 749         struct scsi_host_sg_pool *sgp;
 750
 751         BUG_ON(index >= SG_MEMPOOL_NR);
 752
 753         sgp = scsi_sg_pools + index;
 754         mempool_free(sgl, sgp->pool);
 755 }
 756
 757 EXPORT_SYMBOL(scsi_free_sgtable);
 758
 759 /*
 760  * Function:    scsi_release_buffers()
 761  *
 762  * Purpose:     Completion processing for block device I/O requests.
 763  *
 764  * Arguments:   cmd     - command that we are bailing.
 765  *
 766  * Lock status: Assumed that no lock is held upon entry.
 767  *
 768  * Returns:     Nothing
 769  *
 770  * Notes:       In the event that an upper level driver rejects a
 771  *              command, we must release resources allocated during
 772  *              the __init_io() function.  Primarily this would involve
 773  *              the scatter-gather table, and potentially any bounce
 774  *              buffers.
 775  */
 776 static void scsi_release_buffers(struct scsi_cmnd *cmd)
 777 {
 778         if (cmd->use_sg)
 779                 scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
 780
 781         /*
 782          * Zero these out.  They now point to freed memory, and it is
 783          * dangerous to hang onto the pointers.
 784          */
 785         cmd->request_buffer = NULL;
 786         cmd->request_bufflen = 0;
 787 }
 788
 789 /*
 790  * Function:    scsi_io_completion()
 791  *
 792  * Purpose:     Completion processing for block device I/O requests.
 793  *
 794  * Arguments:   cmd   - command that is finished.
 795  *
 796  * Lock status: Assumed that no lock is held upon entry.
 797  *
 798  * Returns:     Nothing
 799  *
 800  * Notes:       This function is matched in terms of capabilities to
 801  *              the function that created the scatter-gather list.
 802  *              In other words, if there are no bounce buffers
 803  *              (the normal case for most drivers), we don't need
 804  *              the logic to deal with cleaning up afterwards.
 805  *
 806  *              We must do one of several things here:
 807  *
 808  *              a) Call scsi_end_request.  This will finish off the
 809  *                 specified number of sectors.  If we are done, the
 810  *                 command block will be released, and the queue
 811  *                 function will be goosed.  If we are not done, then
 812  *                 scsi_end_request will directly goose the queue.
 813  *
 814  *              b) We can just use scsi_requeue_command() here.  This would
 815  *                 be used if we just wanted to retry, for example.
 816  */
 817 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 818 {
 819         int result = cmd->result;
 820         int this_count = cmd->request_bufflen;
 821         request_queue_t *q = cmd->device->request_queue;
 822         struct request *req = cmd->request;
 823         int clear_errors = 1;
 824         struct scsi_sense_hdr sshdr;
 825         int sense_valid = 0;
 826         int sense_deferred = 0;
 827
 828         scsi_release_buffers(cmd);
 829
 830         if (result) {
 831                 sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
 832                 if (sense_valid)
 833                         sense_deferred = scsi_sense_is_deferred(&sshdr);
 834         }
 835
 836         if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
 837                 req->errors = result;
 838                 if (result) {
 839                         clear_errors = 0;
 840                         if (sense_valid && req->sense) {
 841                                 /*
 842                                  * SG_IO wants current and deferred errors
 843                                  */
 844                                 int len = 8 + cmd->sense_buffer[7];
 845
 846                                 if (len > SCSI_SENSE_BUFFERSIZE)
 847                                         len = SCSI_SENSE_BUFFERSIZE;
 848                                 memcpy(req->sense, cmd->sense_buffer,  len);
 849                                 req->sense_len = len;
 850                         }
 851                 } else
 852                         req->data_len = cmd->resid;
 853         }
 854
 855         /*
 856          * Next deal with any sectors which we were able to correctly
 857          * handle.
 858          */
 859         SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, "
 860                                       "%d bytes done.\n",
 861                                       req->nr_sectors, good_bytes));
 862         SCSI_LOG_HLCOMPLETE(1, printk("use_sg is %d\n", cmd->use_sg));
 863
 864         if (clear_errors)
 865                 req->errors = 0;
 866
 867         /* A number of bytes were successfully read.  If there
 868          * are leftovers and there is some kind of error
 869          * (result != 0), retry the rest.
 870          */
 871         if (scsi_end_request(cmd, 1, good_bytes, result == 0) == NULL)
 872                 return;
 873
 874         /* good_bytes = 0, or (inclusive) there were leftovers and
 875          * result = 0, so scsi_end_request couldn't retry.
 876          */
 877         if (sense_valid && !sense_deferred) {
 878                 switch (sshdr.sense_key) {
 879                 case UNIT_ATTENTION:
 880                         if (cmd->device->removable) {
 881                                 /* Detected disc change.  Set a bit
 882                                  * and quietly refuse further access.
 883                                  */
 884                                 cmd->device->changed = 1;
 885                                 scsi_end_request(cmd, 0, this_count, 1);
 886                                 return;
 887                         } else {
 888                                 /* Must have been a power glitch, or a
 889                                  * bus reset.  Could not have been a
 890                                  * media change, so we just retry the
 891                                  * request and see what happens.
 892                                  */
 893                                 scsi_requeue_command(q, cmd);
 894                                 return;
 895                         }
 896                         break;
 897                 case ILLEGAL_REQUEST:
 898                         /* If we had an ILLEGAL REQUEST returned, then
 899                          * we may have performed an unsupported
 900                          * command.  The only thing this should be
 901                          * would be a ten byte read where only a six
 902                          * byte read was supported.  Also, on a system
 903                          * where READ CAPACITY failed, we may have
 904                          * read past the end of the disk.
 905                          */
 906                         if ((cmd->device->use_10_for_rw &&
 907                             sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
 908                             (cmd->cmnd[0] == READ_10 ||
 909                              cmd->cmnd[0] == WRITE_10)) {
 910                                 cmd->device->use_10_for_rw = 0;
 911                                 /* This will cause a retry with a
 912                                  * 6-byte command.
 913                                  */
 914                                 scsi_requeue_command(q, cmd);
 915                                 return;
 916                         } else {
 917                                 scsi_end_request(cmd, 0, this_count, 1);
 918                                 return;
 919                         }
 920                         break;
 921                 case NOT_READY:
 922                         /* If the device is in the process of becoming
 923                          * ready, or has a temporary blockage, retry.
 924                          */
 925                         if (sshdr.asc == 0x04) {
 926                                 switch (sshdr.ascq) {
 927                                 case 0x01: /* becoming ready */
 928                                 case 0x04: /* format in progress */
 929                                 case 0x05: /* rebuild in progress */
 930                                 case 0x06: /* recalculation in progress */
 931                                 case 0x07: /* operation in progress */
 932                                 case 0x08: /* Long write in progress */
 933                                 case 0x09: /* self test in progress */
 934                                         scsi_requeue_command(q, cmd);
 935                                         return;
 936                                 default:
 937                                         break;
 938                                 }
 939                         }
 940                         if (!(req->cmd_flags & REQ_QUIET)) {
 941                                 scmd_printk(KERN_INFO, cmd,
 942                                             "Device not ready: ");
 943                                 scsi_print_sense_hdr("", &sshdr);
 944                         }
 945                         scsi_end_request(cmd, 0, this_count, 1);
 946                         return;
 947                 case VOLUME_OVERFLOW:
 948                         if (!(req->cmd_flags & REQ_QUIET)) {
 949                                 scmd_printk(KERN_INFO, cmd,
 950                                             "Volume overflow, CDB: ");
 951                                 __scsi_print_command(cmd->cmnd);
 952                                 scsi_print_sense("", cmd);
 953                         }
 954                         /* See SSC3rXX or current. */
 955                         scsi_end_request(cmd, 0, this_count, 1);
 956                         return;
 957                 default:
 958                         break;
 959                 }
 960         }
 961         if (host_byte(result) == DID_RESET) {
 962                 /* Third party bus reset or reset for error recovery
 963                  * reasons.  Just retry the request and see what
 964                  * happens.
 965                  */
 966                 scsi_requeue_command(q, cmd);
 967                 return;
 968         }
 969         if (result) {
 970                 if (!(req->cmd_flags & REQ_QUIET)) {
 971                         scmd_printk(KERN_INFO, cmd,
 972                                     "SCSI error: return code = 0x%08x\n",
 973                                     result);
 974                         if (driver_byte(result) & DRIVER_SENSE)
 975                                 scsi_print_sense("", cmd);
 976                 }
 977         }
 978         scsi_end_request(cmd, 0, this_count, !result);
 979 }
 980 EXPORT_SYMBOL(scsi_io_completion);
 981
 982 /*
 983  * Function:    scsi_init_io()
 984  *
 985  * Purpose:     SCSI I/O initialize function.
 986  *
 987  * Arguments:   cmd   - Command descriptor we wish to initialize
 988  *
 989  * Returns:     0 on success
 990  *              BLKPREP_DEFER if the failure is retryable
 991  *              BLKPREP_KILL if the failure is fatal
 992  */
 993 static int scsi_init_io(struct scsi_cmnd *cmd)
 994 {
 995         struct request     *req = cmd->request;
 996         struct scatterlist *sgpnt;
 997         int                count;
 998
 999         /*
1000          * We used to not use scatter-gather for single segment request,
1001          * but now we do (it makes highmem I/O easier to support without
1002          * kmapping pages)
1003          */
1004         cmd->use_sg = req->nr_phys_segments;
1005
1006         /*
1007          * If sg table allocation fails, requeue request later.
1008          */
1009         sgpnt = scsi_alloc_sgtable(cmd, GFP_ATOMIC);
1010         if (unlikely(!sgpnt)) {
1011                 scsi_unprep_request(req);
1012                 return BLKPREP_DEFER;
1013         }
1014
1015         req->buffer = NULL;
1016         cmd->request_buffer = (char *) sgpnt;
1017         if (blk_pc_request(req))
1018                 cmd->request_bufflen = req->data_len;
1019         else
1020                 cmd->request_bufflen = req->nr_sectors << 9;
1021
1022         /*
1023          * Next, walk the list, and fill in the addresses and sizes of
1024          * each segment.
1025          */
1026         count = blk_rq_map_sg(req->q, req, cmd->request_buffer);
1027         if (likely(count <= cmd->use_sg)) {
1028                 cmd->use_sg = count;
1029                 return BLKPREP_OK;
1030         }
1031
1032         printk(KERN_ERR "Incorrect number of segments after building list\n");
1033         printk(KERN_ERR "counted %d, received %d\n", count, cmd->use_sg);
1034         printk(KERN_ERR "req nr_sec %lu, cur_nr_sec %u\n", req->nr_sectors,
1035                         req->current_nr_sectors);
1036
1037         /* release the command and kill it */
1038         scsi_release_buffers(cmd);
1039         scsi_put_command(cmd);
1040         return BLKPREP_KILL;
1041 }
1042
1043 static int scsi_issue_flush_fn(request_queue_t *q, struct gendisk *disk,
1044                                sector_t *error_sector)
1045 {
1046         struct scsi_device *sdev = q->queuedata;
1047         struct scsi_driver *drv;
1048
1049         if (sdev->sdev_state != SDEV_RUNNING)
1050                 return -ENXIO;
1051
1052         drv = *(struct scsi_driver **) disk->private_data;
1053         if (drv->issue_flush)
1054                 return drv->issue_flush(&sdev->sdev_gendev, error_sector);
1055
1056         return -EOPNOTSUPP;
1057 }
1058
1059 static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
1060                 struct request *req)
1061 {
1062         struct scsi_cmnd *cmd;
1063
1064         if (!req->special) {
1065                 cmd = scsi_get_command(sdev, GFP_ATOMIC);
1066                 if (unlikely(!cmd))
1067                         return NULL;
1068                 req->special = cmd;
1069         } else {
1070                 cmd = req->special;
1071         }
1072
1073         /* pull a tag out of the request if we have one */
1074         cmd->tag = req->tag;
1075         cmd->request = req;
1076
1077         return cmd;
1078 }
1079
1080 static void scsi_blk_pc_done(struct scsi_cmnd *cmd)
1081 {
1082         BUG_ON(!blk_pc_request(cmd->request));
1083         /*
1084          * This will complete the whole command with uptodate=1 so
1085          * as far as the block layer is concerned the command completed
1086          * successfully. Since this is a REQ_BLOCK_PC command the
1087          * caller should check the request's errors value
1088          */
1089         scsi_io_completion(cmd, cmd->request_bufflen);
1090 }
1091
1092 static int scsi_setup_blk_pc_cmnd(struct scsi_device *sdev, struct request *req)
1093 {
1094         struct scsi_cmnd *cmd;
1095
1096         cmd = scsi_get_cmd_from_req(sdev, req);
1097         if (unlikely(!cmd))
1098                 return BLKPREP_DEFER;
1099
1100         /*
1101          * BLOCK_PC requests may transfer data, in which case they must
1102          * a bio attached to them.  Or they might contain a SCSI command
1103          * that does not transfer data, in which case they may optionally
1104          * submit a request without an attached bio.
1105          */
1106         if (req->bio) {
1107                 int ret;
1108
1109                 BUG_ON(!req->nr_phys_segments);
1110
1111                 ret = scsi_init_io(cmd);
1112                 if (unlikely(ret))
1113                         return ret;
1114         } else {
1115                 BUG_ON(req->data_len);
1116                 BUG_ON(req->data);
1117
1118                 cmd->request_bufflen = 0;
1119                 cmd->request_buffer = NULL;
1120                 cmd->use_sg = 0;
1121                 req->buffer = NULL;
1122         }
1123
1124         BUILD_BUG_ON(sizeof(req->cmd) > sizeof(cmd->cmnd));
1125         memcpy(cmd->cmnd, req->cmd, sizeof(cmd->cmnd));
1126         cmd->cmd_len = req->cmd_len;
1127         if (!req->data_len)
1128                 cmd->sc_data_direction = DMA_NONE;
1129         else if (rq_data_dir(req) == WRITE)
1130                 cmd->sc_data_direction = DMA_TO_DEVICE;
1131         else
1132                 cmd->sc_data_direction = DMA_FROM_DEVICE;
1133
1134         cmd->transfersize = req->data_len;
1135         cmd->allowed = req->retries;
1136         cmd->timeout_per_command = req->timeout;
1137         cmd->done = scsi_blk_pc_done;
1138         return BLKPREP_OK;
1139 }
1140
1141 /*
1142  * Setup a REQ_TYPE_FS command.  These are simple read/write request
1143  * from filesystems that still need to be translated to SCSI CDBs from
1144  * the ULD.
1145  */
1146 static int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
1147 {
1148         struct scsi_cmnd *cmd;
1149         struct scsi_driver *drv;
1150         int ret;
1151
1152         /*
1153          * Filesystem requests must transfer data.
1154          */
1155         BUG_ON(!req->nr_phys_segments);
1156
1157         cmd = scsi_get_cmd_from_req(sdev, req);
1158         if (unlikely(!cmd))
1159                 return BLKPREP_DEFER;
1160
1161         ret = scsi_init_io(cmd);
1162         if (unlikely(ret))
1163                 return ret;
1164
1165         /*
1166          * Initialize the actual SCSI command for this request.
1167          */
1168         drv = *(struct scsi_driver **)req->rq_disk->private_data;
1169         if (unlikely(!drv->init_command(cmd))) {
1170                 scsi_release_buffers(cmd);
1171                 scsi_put_command(cmd);
1172                 return BLKPREP_KILL;
1173         }
1174
1175         return BLKPREP_OK;
1176 }
1177
1178 static int scsi_prep_fn(struct request_queue *q, struct request *req)
1179 {
1180         struct scsi_device *sdev = q->queuedata;
1181         int ret = BLKPREP_OK;
1182
1183         /*
1184          * If the device is not in running state we will reject some
1185          * or all commands.
1186          */
1187         if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
1188                 switch (sdev->sdev_state) {
1189                 case SDEV_OFFLINE:
1190                         /*
1191                          * If the device is offline we refuse to process any
1192                          * commands.  The device must be brought online
1193                          * before trying any recovery commands.
1194                          */
1195                         sdev_printk(KERN_ERR, sdev,
1196                                     "rejecting I/O to offline device\n");
1197                         ret = BLKPREP_KILL;
1198                         break;
1199                 case SDEV_DEL:
1200                         /*
1201                          * If the device is fully deleted, we refuse to
1202                          * process any commands as well.
1203                          */
1204                         sdev_printk(KERN_ERR, sdev,
1205                                     "rejecting I/O to dead device\n");
1206                         ret = BLKPREP_KILL;
1207                         break;
1208                 case SDEV_QUIESCE:
1209                 case SDEV_BLOCK:
1210                         /*
1211                          * If the devices is blocked we defer normal commands.
1212                          */
1213                         if (!(req->cmd_flags & REQ_PREEMPT))
1214                                 ret = BLKPREP_DEFER;
1215                         break;
1216                 default:
1217                         /*
1218                          * For any other not fully online state we only allow
1219                          * special commands.  In particular any user initiated
1220                          * command is not allowed.
1221                          */
1222                         if (!(req->cmd_flags & REQ_PREEMPT))
1223                                 ret = BLKPREP_KILL;
1224                         break;
1225                 }
1226
1227                 if (ret != BLKPREP_OK)
1228                         goto out;
1229         }
1230
1231         switch (req->cmd_type) {
1232         case REQ_TYPE_BLOCK_PC:
1233                 ret = scsi_setup_blk_pc_cmnd(sdev, req);
1234                 break;
1235         case REQ_TYPE_FS:
1236                 ret = scsi_setup_fs_cmnd(sdev, req);
1237                 break;
1238         default:
1239                 /*
1240                  * All other command types are not supported.
1241                  *
1242                  * Note that these days the SCSI subsystem does not use
1243                  * REQ_TYPE_SPECIAL requests anymore.  These are only used
1244                  * (directly or via blk_insert_request) by non-SCSI drivers.
1245                  */
1246                 blk_dump_rq_flags(req, "SCSI bad req");
1247                 ret = BLKPREP_KILL;
1248                 break;
1249         }
1250
1251  out:
1252         switch (ret) {
1253         case BLKPREP_KILL:
1254                 req->errors = DID_NO_CONNECT << 16;
1255                 break;
1256         case BLKPREP_DEFER:
1257                 /*
1258                  * If we defer, the elv_next_request() returns NULL, but the
1259                  * queue must be restarted, so we plug here if no returning
1260                  * command will automatically do that.
1261                  */
1262                 if (sdev->device_busy == 0)
1263                         blk_plug_device(q);
1264                 break;
1265         default:
1266                 req->cmd_flags |= REQ_DONTPREP;
1267         }
1268
1269         return ret;
1270 }
1271
1272 /*
1273  * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1274  * return 0.
1275  *
1276  * Called with the queue_lock held.
1277  */
1278 static inline int scsi_dev_queue_ready(struct request_queue *q,
1279                                   struct scsi_device *sdev)
1280 {
1281         if (sdev->device_busy >= sdev->queue_depth)
1282                 return 0;
1283         if (sdev->device_busy == 0 && sdev->device_blocked) {
1284                 /*
1285                  * unblock after device_blocked iterates to zero
1286                  */
1287                 if (--sdev->device_blocked == 0) {
1288                         SCSI_LOG_MLQUEUE(3,
1289                                    sdev_printk(KERN_INFO, sdev,
1290                                    "unblocking device at zero depth\n"));
1291                 } else {
1292                         blk_plug_device(q);
1293                         return 0;
1294                 }
1295         }
1296         if (sdev->device_blocked)
1297                 return 0;
1298
1299         return 1;
1300 }
1301
1302 /*
1303  * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1304  * return 0. We must end up running the queue again whenever 0 is
1305  * returned, else IO can hang.
1306  *
1307  * Called with host_lock held.
1308  */
1309 static inline int scsi_host_queue_ready(struct request_queue *q,
1310                                    struct Scsi_Host *shost,
1311                                    struct scsi_device *sdev)
1312 {
1313         if (scsi_host_in_recovery(shost))
1314                 return 0;
1315         if (shost->host_busy == 0 && shost->host_blocked) {
1316                 /*
1317                  * unblock after host_blocked iterates to zero
1318                  */
1319                 if (--shost->host_blocked == 0) {
1320                         SCSI_LOG_MLQUEUE(3,
1321                                 printk("scsi%d unblocking host at zero depth\n",
1322                                         shost->host_no));
1323                 } else {
1324                         blk_plug_device(q);
1325                         return 0;
1326                 }
1327         }
1328         if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
1329             shost->host_blocked || shost->host_self_blocked) {
1330                 if (list_empty(&sdev->starved_entry))
1331                         list_add_tail(&sdev->starved_entry, &shost->starved_list);
1332                 return 0;
1333         }
1334
1335         /* We're OK to process the command, so we can't be starved */
1336         if (!list_empty(&sdev->starved_entry))
1337                 list_del_init(&sdev->starved_entry);
1338
1339         return 1;
1340 }
1341
1342 /*
1343  * Kill a request for a dead device
1344  */
1345 static void scsi_kill_request(struct request *req, request_queue_t *q)
1346 {
1347         struct scsi_cmnd *cmd = req->special;
1348         struct scsi_device *sdev = cmd->device;
1349         struct Scsi_Host *shost = sdev->host;
1350
1351         blkdev_dequeue_request(req);
1352
1353         if (unlikely(cmd == NULL)) {
1354                 printk(KERN_CRIT "impossible request in %s.\n",
1355                                  __FUNCTION__);
1356                 BUG();
1357         }
1358
1359         scsi_init_cmd_errh(cmd);
1360         cmd->result = DID_NO_CONNECT << 16;
1361         atomic_inc(&cmd->device->iorequest_cnt);
1362
1363         /*
1364          * SCSI request completion path will do scsi_device_unbusy(),
1365          * bump busy counts.  To bump the counters, we need to dance
1366          * with the locks as normal issue path does.
1367          */
1368         sdev->device_busy++;
1369         spin_unlock(sdev->request_queue->queue_lock);
1370         spin_lock(shost->host_lock);
1371         shost->host_busy++;
1372         spin_unlock(shost->host_lock);
1373         spin_lock(sdev->request_queue->queue_lock);
1374
1375         __scsi_done(cmd);
1376 }
1377
1378 static void scsi_softirq_done(struct request *rq)
1379 {
1380         struct scsi_cmnd *cmd = rq->completion_data;
1381         unsigned long wait_for = (cmd->allowed + 1) * cmd->timeout_per_command;
1382         int disposition;
1383
1384         INIT_LIST_HEAD(&cmd->eh_entry);
1385
1386         disposition = scsi_decide_disposition(cmd);
1387         if (disposition != SUCCESS &&
1388             time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
1389                 sdev_printk(KERN_ERR, cmd->device,
1390                             "timing out command, waited %lus\n",
1391                             wait_for/HZ);
1392                 disposition = SUCCESS;
1393         }
1394
1395         scsi_log_completion(cmd, disposition);
1396
1397         switch (disposition) {
1398                 case SUCCESS:
1399                         scsi_finish_command(cmd);
1400                         break;
1401                 case NEEDS_RETRY:
1402                         scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY);
1403                         break;
1404                 case ADD_TO_MLQUEUE:
1405                         scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
1406                         break;
1407                 default:
1408                         if (!scsi_eh_scmd_add(cmd, 0))
1409                                 scsi_finish_command(cmd);
1410         }
1411 }
1412
1413 /*
1414  * Function:    scsi_request_fn()
1415  *
1416  * Purpose:     Main strategy routine for SCSI.
1417  *
1418  * Arguments:   q       - Pointer to actual queue.
1419  *
1420  * Returns:     Nothing
1421  *
1422  * Lock status: IO request lock assumed to be held when called.
1423  */
1424 static void scsi_request_fn(struct request_queue *q)
1425 {
1426         struct scsi_device *sdev = q->queuedata;
1427         struct Scsi_Host *shost;
1428         struct scsi_cmnd *cmd;
1429         struct request *req;
1430
1431         if (!sdev) {
1432                 printk("scsi: killing requests for dead queue\n");
1433                 while ((req = elv_next_request(q)) != NULL)
1434                         scsi_kill_request(req, q);
1435                 return;
1436         }
1437
1438         if(!get_device(&sdev->sdev_gendev))
1439                 /* We must be tearing the block queue down already */
1440                 return;
1441
1442         /*
1443          * To start with, we keep looping until the queue is empty, or until
1444          * the host is no longer able to accept any more requests.
1445          */
1446         shost = sdev->host;
1447         while (!blk_queue_plugged(q)) {
1448                 int rtn;
1449                 /*
1450                  * get next queueable request.  We do this early to make sure
1451                  * that the request is fully prepared even if we cannot
1452                  * accept it.
1453                  */
1454                 req = elv_next_request(q);
1455                 if (!req || !scsi_dev_queue_ready(q, sdev))
1456                         break;
1457
1458                 if (unlikely(!scsi_device_online(sdev))) {
1459                         sdev_printk(KERN_ERR, sdev,
1460                                     "rejecting I/O to offline device\n");
1461                         scsi_kill_request(req, q);
1462                         continue;
1463                 }
1464
1465
1466                 /*
1467                  * Remove the request from the request list.
1468                  */
1469                 if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1470                         blkdev_dequeue_request(req);
1471                 sdev->device_busy++;
1472
1473                 spin_unlock(q->queue_lock);
1474                 cmd = req->special;
1475                 if (unlikely(cmd == NULL)) {
1476                         printk(KERN_CRIT "impossible request in %s.\n"
1477                                          "please mail a stack trace to "
1478                                          "linux-scsi@vger.kernel.org\n",
1479                                          __FUNCTION__);
1480                         blk_dump_rq_flags(req, "foo");
1481                         BUG();
1482                 }
1483                 spin_lock(shost->host_lock);
1484
1485                 if (!scsi_host_queue_ready(q, shost, sdev))
1486                         goto not_ready;
1487                 if (sdev->single_lun) {
1488                         if (scsi_target(sdev)->starget_sdev_user &&
1489                             scsi_target(sdev)->starget_sdev_user != sdev)
1490                                 goto not_ready;
1491                         scsi_target(sdev)->starget_sdev_user = sdev;
1492                 }
1493                 shost->host_busy++;
1494
1495                 /*
1496                  * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1497                  *              take the lock again.
1498                  */
1499                 spin_unlock_irq(shost->host_lock);
1500
1501                 /*
1502                  * Finally, initialize any error handling parameters, and set up
1503                  * the timers for timeouts.
1504                  */
1505                 scsi_init_cmd_errh(cmd);
1506
1507                 /*
1508                  * Dispatch the command to the low-level driver.
1509                  */
1510                 rtn = scsi_dispatch_cmd(cmd);
1511                 spin_lock_irq(q->queue_lock);
1512                 if(rtn) {
1513                         /* we're refusing the command; because of
1514                          * the way locks get dropped, we need to
1515                          * check here if plugging is required */
1516                         if(sdev->device_busy == 0)
1517                                 blk_plug_device(q);
1518
1519                         break;
1520                 }
1521         }
1522
1523         goto out;
1524
1525  not_ready:
1526         spin_unlock_irq(shost->host_lock);
1527
1528         /*
1529          * lock q, handle tag, requeue req, and decrement device_busy. We
1530          * must return with queue_lock held.
1531          *
1532          * Decrementing device_busy without checking it is OK, as all such
1533          * cases (host limits or settings) should run the queue at some
1534          * later time.
1535          */
1536         spin_lock_irq(q->queue_lock);
1537         blk_requeue_request(q, req);
1538         sdev->device_busy--;
1539         if(sdev->device_busy == 0)
1540                 blk_plug_device(q);
1541  out:
1542         /* must be careful here...if we trigger the ->remove() function
1543          * we cannot be holding the q lock */
1544         spin_unlock_irq(q->queue_lock);
1545         put_device(&sdev->sdev_gendev);
1546         spin_lock_irq(q->queue_lock);
1547 }
1548
1549 u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1550 {
1551         struct device *host_dev;
1552         u64 bounce_limit = 0xffffffff;
1553
1554         if (shost->unchecked_isa_dma)
1555                 return BLK_BOUNCE_ISA;
1556         /*
1557          * Platforms with virtual-DMA translation
1558          * hardware have no practical limit.
1559          */
1560         if (!PCI_DMA_BUS_IS_PHYS)
1561                 return BLK_BOUNCE_ANY;
1562
1563         host_dev = scsi_get_device(shost);
1564         if (host_dev && host_dev->dma_mask)
1565                 bounce_limit = *host_dev->dma_mask;
1566
1567         return bounce_limit;
1568 }
1569 EXPORT_SYMBOL(scsi_calculate_bounce_limit);
1570
1571 struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
1572                                          request_fn_proc *request_fn)
1573 {
1574         struct request_queue *q;
1575
1576         q = blk_init_queue(request_fn, NULL);
1577         if (!q)
1578                 return NULL;
1579
1580         blk_queue_max_hw_segments(q, shost->sg_tablesize);
1581         blk_queue_max_phys_segments(q, SCSI_MAX_PHYS_SEGMENTS);
1582         blk_queue_max_sectors(q, shost->max_sectors);
1583         blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1584         blk_queue_segment_boundary(q, shost->dma_boundary);
1585
1586         if (!shost->use_clustering)
1587                 clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
1588         return q;
1589 }
1590 EXPORT_SYMBOL(__scsi_alloc_queue);
1591
1592 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1593 {
1594         struct request_queue *q;
1595
1596         q = __scsi_alloc_queue(sdev->host, scsi_request_fn);
1597         if (!q)
1598                 return NULL;
1599
1600         blk_queue_prep_rq(q, scsi_prep_fn);
1601         blk_queue_issue_flush_fn(q, scsi_issue_flush_fn);
1602         blk_queue_softirq_done(q, scsi_softirq_done);
1603         return q;
1604 }
1605
1606 void scsi_free_queue(struct request_queue *q)
1607 {
1608         blk_cleanup_queue(q);
1609 }
1610
1611 /*
1612  * Function:    scsi_block_requests()
1613  *
1614  * Purpose:     Utility function used by low-level drivers to prevent further
1615  *              commands from being queued to the device.
1616  *
1617  * Arguments:   shost       - Host in question
1618  *
1619  * Returns:     Nothing
1620  *
1621  * Lock status: No locks are assumed held.
1622  *
1623  * Notes:       There is no timer nor any other means by which the requests
1624  *              get unblocked other than the low-level driver calling
1625  *              scsi_unblock_requests().
1626  */
1627 void scsi_block_requests(struct Scsi_Host *shost)
1628 {
1629         shost->host_self_blocked = 1;
1630 }
1631 EXPORT_SYMBOL(scsi_block_requests);
1632
1633 /*
1634  * Function:    scsi_unblock_requests()
1635  *
1636  * Purpose:     Utility function used by low-level drivers to allow further
1637  *              commands from being queued to the device.
1638  *
1639  * Arguments:   shost       - Host in question
1640  *
1641  * Returns:     Nothing
1642  *
1643  * Lock status: No locks are assumed held.
1644  *
1645  * Notes:       There is no timer nor any other means by which the requests
1646  *              get unblocked other than the low-level driver calling
1647  *              scsi_unblock_requests().
1648  *
1649  *              This is done as an API function so that changes to the
1650  *              internals of the scsi mid-layer won't require wholesale
1651  *              changes to drivers that use this feature.
1652  */
1653 void scsi_unblock_requests(struct Scsi_Host *shost)
1654 {
1655         shost->host_self_blocked = 0;
1656         scsi_run_host_queues(shost);
1657 }
1658 EXPORT_SYMBOL(scsi_unblock_requests);
1659
1660 int __init scsi_init_queue(void)
1661 {
1662         int i;
1663
1664         scsi_io_context_cache = kmem_cache_create("scsi_io_context",
1665                                         sizeof(struct scsi_io_context),
1666                                         0, 0, NULL, NULL);
1667         if (!scsi_io_context_cache) {
1668                 printk(KERN_ERR "SCSI: can't init scsi io context cache\n");
1669                 return -ENOMEM;
1670         }
1671
1672         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1673                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1674                 int size = sgp->size * sizeof(struct scatterlist);
1675
1676                 sgp->slab = kmem_cache_create(sgp->name, size, 0,
1677                                 SLAB_HWCACHE_ALIGN, NULL, NULL);
1678                 if (!sgp->slab) {
1679                         printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1680                                         sgp->name);
1681                 }
1682
1683                 sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
1684                                                      sgp->slab);
1685                 if (!sgp->pool) {
1686                         printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1687                                         sgp->name);
1688                 }
1689         }
1690
1691         return 0;
1692 }
1693
1694 void scsi_exit_queue(void)
1695 {
1696         int i;
1697
1698         kmem_cache_destroy(scsi_io_context_cache);
1699
1700         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1701                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1702                 mempool_destroy(sgp->pool);
1703                 kmem_cache_destroy(sgp->slab);
1704         }
1705 }
1706
1707 /**
1708  *      scsi_mode_select - issue a mode select
1709  *      @sdev:  SCSI device to be queried
1710  *      @pf:    Page format bit (1 == standard, 0 == vendor specific)
1711  *      @sp:    Save page bit (0 == don't save, 1 == save)
1712  *      @modepage: mode page being requested
1713  *      @buffer: request buffer (may not be smaller than eight bytes)
1714  *      @len:   length of request buffer.
1715  *      @timeout: command timeout
1716  *      @retries: number of retries before failing
1717  *      @data: returns a structure abstracting the mode header data
1718  *      @sense: place to put sense data (or NULL if no sense to be collected).
1719  *              must be SCSI_SENSE_BUFFERSIZE big.
1720  *
1721  *      Returns zero if successful; negative error number or scsi
1722  *      status on error
1723  *
1724  */
1725 int
1726 scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
1727                  unsigned char *buffer, int len, int timeout, int retries,
1728                  struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1729 {
1730         unsigned char cmd[10];
1731         unsigned char *real_buffer;
1732         int ret;
1733
1734         memset(cmd, 0, sizeof(cmd));
1735         cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
1736
1737         if (sdev->use_10_for_ms) {
1738                 if (len > 65535)
1739                         return -EINVAL;
1740                 real_buffer = kmalloc(8 + len, GFP_KERNEL);
1741                 if (!real_buffer)
1742                         return -ENOMEM;
1743                 memcpy(real_buffer + 8, buffer, len);
1744                 len += 8;
1745                 real_buffer[0] = 0;
1746                 real_buffer[1] = 0;
1747                 real_buffer[2] = data->medium_type;
1748                 real_buffer[3] = data->device_specific;
1749                 real_buffer[4] = data->longlba ? 0x01 : 0;
1750                 real_buffer[5] = 0;
1751                 real_buffer[6] = data->block_descriptor_length >> 8;
1752                 real_buffer[7] = data->block_descriptor_length;
1753
1754                 cmd[0] = MODE_SELECT_10;
1755                 cmd[7] = len >> 8;
1756                 cmd[8] = len;
1757         } else {
1758                 if (len > 255 || data->block_descriptor_length > 255 ||
1759                     data->longlba)
1760                         return -EINVAL;
1761
1762                 real_buffer = kmalloc(4 + len, GFP_KERNEL);
1763                 if (!real_buffer)
1764                         return -ENOMEM;
1765                 memcpy(real_buffer + 4, buffer, len);
1766                 len += 4;
1767                 real_buffer[0] = 0;
1768                 real_buffer[1] = data->medium_type;
1769                 real_buffer[2] = data->device_specific;
1770                 real_buffer[3] = data->block_descriptor_length;
1771
1772
1773                 cmd[0] = MODE_SELECT;
1774                 cmd[4] = len;
1775         }
1776
1777         ret = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, real_buffer, len,
1778                                sshdr, timeout, retries);
1779         kfree(real_buffer);
1780         return ret;
1781 }
1782 EXPORT_SYMBOL_GPL(scsi_mode_select);
1783
1784 /**
1785  *      scsi_mode_sense - issue a mode sense, falling back from 10 to
1786  *              six bytes if necessary.
1787  *      @sdev:  SCSI device to be queried
1788  *      @dbd:   set if mode sense will allow block descriptors to be returned
1789  *      @modepage: mode page being requested
1790  *      @buffer: request buffer (may not be smaller than eight bytes)
1791  *      @len:   length of request buffer.
1792  *      @timeout: command timeout
1793  *      @retries: number of retries before failing
1794  *      @data: returns a structure abstracting the mode header data
1795  *      @sense: place to put sense data (or NULL if no sense to be collected).
1796  *              must be SCSI_SENSE_BUFFERSIZE big.
1797  *
1798  *      Returns zero if unsuccessful, or the header offset (either 4
1799  *      or 8 depending on whether a six or ten byte command was
1800  *      issued) if successful.
1801  **/
1802 int
1803 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
1804                   unsigned char *buffer, int len, int timeout, int retries,
1805                   struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1806 {
1807         unsigned char cmd[12];
1808         int use_10_for_ms;
1809         int header_length;
1810         int result;
1811         struct scsi_sense_hdr my_sshdr;
1812
1813         memset(data, 0, sizeof(*data));
1814         memset(&cmd[0], 0, 12);
1815         cmd[1] = dbd & 0x18;    /* allows DBD and LLBA bits */
1816         cmd[2] = modepage;
1817
1818         /* caller might not be interested in sense, but we need it */
1819         if (!sshdr)
1820                 sshdr = &my_sshdr;
1821
1822  retry:
1823         use_10_for_ms = sdev->use_10_for_ms;
1824
1825         if (use_10_for_ms) {
1826                 if (len < 8)
1827                         len = 8;
1828
1829                 cmd[0] = MODE_SENSE_10;
1830                 cmd[8] = len;
1831                 header_length = 8;
1832         } else {
1833                 if (len < 4)
1834                         len = 4;
1835
1836                 cmd[0] = MODE_SENSE;
1837                 cmd[4] = len;
1838                 header_length = 4;
1839         }
1840
1841         memset(buffer, 0, len);
1842
1843         result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
1844                                   sshdr, timeout, retries);
1845
1846         /* This code looks awful: what it's doing is making sure an
1847          * ILLEGAL REQUEST sense return identifies the actual command
1848          * byte as the problem.  MODE_SENSE commands can return
1849          * ILLEGAL REQUEST if the code page isn't supported */
1850
1851         if (use_10_for_ms && !scsi_status_is_good(result) &&
1852             (driver_byte(result) & DRIVER_SENSE)) {
1853                 if (scsi_sense_valid(sshdr)) {
1854                         if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
1855                             (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
1856                                 /*
1857                                  * Invalid command operation code
1858                                  */
1859                                 sdev->use_10_for_ms = 0;
1860                                 goto retry;
1861                         }
1862                 }
1863         }
1864
1865         if(scsi_status_is_good(result)) {
1866                 if (unlikely(buffer[0] == 0x86 && buffer[1] == 0x0b &&
1867                              (modepage == 6 || modepage == 8))) {
1868                         /* Initio breakage? */
1869                         header_length = 0;
1870                         data->length = 13;
1871                         data->medium_type = 0;
1872                         data->device_specific = 0;
1873                         data->longlba = 0;
1874                         data->block_descriptor_length = 0;
1875                 } else if(use_10_for_ms) {
1876                         data->length = buffer[0]*256 + buffer[1] + 2;
1877                         data->medium_type = buffer[2];
1878                         data->device_specific = buffer[3];
1879                         data->longlba = buffer[4] & 0x01;
1880                         data->block_descriptor_length = buffer[6]*256
1881                                 + buffer[7];
1882                 } else {
1883                         data->length = buffer[0] + 1;
1884                         data->medium_type = buffer[1];
1885                         data->device_specific = buffer[2];
1886                         data->block_descriptor_length = buffer[3];
1887                 }
1888                 data->header_length = header_length;
1889         }
1890
1891         return result;
1892 }
1893 EXPORT_SYMBOL(scsi_mode_sense);
1894
1895 int
1896 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries)
1897 {
1898         char cmd[] = {
1899                 TEST_UNIT_READY, 0, 0, 0, 0, 0,
1900         };
1901         struct scsi_sense_hdr sshdr;
1902         int result;
1903
1904         result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, &sshdr,
1905                                   timeout, retries);
1906
1907         if ((driver_byte(result) & DRIVER_SENSE) && sdev->removable) {
1908
1909                 if ((scsi_sense_valid(&sshdr)) &&
1910                     ((sshdr.sense_key == UNIT_ATTENTION) ||
1911                      (sshdr.sense_key == NOT_READY))) {
1912                         sdev->changed = 1;
1913                         result = 0;
1914                 }
1915         }
1916         return result;
1917 }
1918 EXPORT_SYMBOL(scsi_test_unit_ready);
1919
1920 /**
1921  *      scsi_device_set_state - Take the given device through the device
1922  *              state model.
1923  *      @sdev:  scsi device to change the state of.
1924  *      @state: state to change to.
1925  *
1926  *      Returns zero if unsuccessful or an error if the requested
1927  *      transition is illegal.
1928  **/
1929 int
1930 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
1931 {
1932         enum scsi_device_state oldstate = sdev->sdev_state;
1933
1934         if (state == oldstate)
1935                 return 0;
1936
1937         switch (state) {
1938         case SDEV_CREATED:
1939                 /* There are no legal states that come back to
1940                  * created.  This is the manually initialised start
1941                  * state */
1942                 goto illegal;
1943
1944         case SDEV_RUNNING:
1945                 switch (oldstate) {
1946                 case SDEV_CREATED:
1947                 case SDEV_OFFLINE:
1948                 case SDEV_QUIESCE:
1949                 case SDEV_BLOCK:
1950                         break;
1951                 default:
1952                         goto illegal;
1953                 }
1954                 break;
1955
1956         case SDEV_QUIESCE:
1957                 switch (oldstate) {
1958                 case SDEV_RUNNING:
1959                 case SDEV_OFFLINE:
1960                         break;
1961                 default:
1962                         goto illegal;
1963                 }
1964                 break;
1965
1966         case SDEV_OFFLINE:
1967                 switch (oldstate) {
1968                 case SDEV_CREATED:
1969                 case SDEV_RUNNING:
1970                 case SDEV_QUIESCE:
1971                 case SDEV_BLOCK:
1972                         break;
1973                 default:
1974                         goto illegal;
1975                 }
1976                 break;
1977
1978         case SDEV_BLOCK:
1979                 switch (oldstate) {
1980                 case SDEV_CREATED:
1981                 case SDEV_RUNNING:
1982                         break;
1983                 default:
1984                         goto illegal;
1985                 }
1986                 break;
1987
1988         case SDEV_CANCEL:
1989                 switch (oldstate) {
1990                 case SDEV_CREATED:
1991                 case SDEV_RUNNING:
1992                 case SDEV_QUIESCE:
1993                 case SDEV_OFFLINE:
1994                 case SDEV_BLOCK:
1995                         break;
1996                 default:
1997                         goto illegal;
1998                 }
1999                 break;
2000
2001         case SDEV_DEL:
2002                 switch (oldstate) {
2003                 case SDEV_CREATED:
2004                 case SDEV_RUNNING:
2005                 case SDEV_OFFLINE:
2006                 case SDEV_CANCEL:
2007                         break;
2008                 default:
2009                         goto illegal;
2010                 }
2011                 break;
2012
2013         }
2014         sdev->sdev_state = state;
2015         return 0;
2016
2017  illegal:
2018         SCSI_LOG_ERROR_RECOVERY(1,
2019                                 sdev_printk(KERN_ERR, sdev,
2020                                             "Illegal state transition %s->%s\n",
2021                                             scsi_device_state_name(oldstate),
2022                                             scsi_device_state_name(state))
2023                                 );
2024         return -EINVAL;
2025 }
2026 EXPORT_SYMBOL(scsi_device_set_state);
2027
2028 /**
2029  *      scsi_device_quiesce - Block user issued commands.
2030  *      @sdev:  scsi device to quiesce.
2031  *
2032  *      This works by trying to transition to the SDEV_QUIESCE state
2033  *      (which must be a legal transition).  When the device is in this
2034  *      state, only special requests will be accepted, all others will
2035  *      be deferred.  Since special requests may also be requeued requests,
2036  *      a successful return doesn't guarantee the device will be
2037  *      totally quiescent.
2038  *
2039  *      Must be called with user context, may sleep.
2040  *
2041  *      Returns zero if unsuccessful or an error if not.
2042  **/
2043 int
2044 scsi_device_quiesce(struct scsi_device *sdev)
2045 {
2046         int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
2047         if (err)
2048                 return err;
2049
2050         scsi_run_queue(sdev->request_queue);
2051         while (sdev->device_busy) {
2052                 msleep_interruptible(200);
2053                 scsi_run_queue(sdev->request_queue);
2054         }
2055         return 0;
2056 }
2057 EXPORT_SYMBOL(scsi_device_quiesce);
2058
2059 /**
2060  *      scsi_device_resume - Restart user issued commands to a quiesced device.
2061  *      @sdev:  scsi device to resume.
2062  *
2063  *      Moves the device from quiesced back to running and restarts the
2064  *      queues.
2065  *
2066  *      Must be called with user context, may sleep.
2067  **/
2068 void
2069 scsi_device_resume(struct scsi_device *sdev)
2070 {
2071         if(scsi_device_set_state(sdev, SDEV_RUNNING))
2072                 return;
2073         scsi_run_queue(sdev->request_queue);
2074 }
2075 EXPORT_SYMBOL(scsi_device_resume);
2076
2077 static void
2078 device_quiesce_fn(struct scsi_device *sdev, void *data)
2079 {
2080         scsi_device_quiesce(sdev);
2081 }
2082
2083 void
2084 scsi_target_quiesce(struct scsi_target *starget)
2085 {
2086         starget_for_each_device(starget, NULL, device_quiesce_fn);
2087 }
2088 EXPORT_SYMBOL(scsi_target_quiesce);
2089
2090 static void
2091 device_resume_fn(struct scsi_device *sdev, void *data)
2092 {
2093         scsi_device_resume(sdev);
2094 }
2095
2096 void
2097 scsi_target_resume(struct scsi_target *starget)
2098 {
2099         starget_for_each_device(starget, NULL, device_resume_fn);
2100 }
2101 EXPORT_SYMBOL(scsi_target_resume);
2102
2103 /**
2104  * scsi_internal_device_block - internal function to put a device
2105  *                              temporarily into the SDEV_BLOCK state
2106  * @sdev:       device to block
2107  *
2108  * Block request made by scsi lld's to temporarily stop all
2109  * scsi commands on the specified device.  Called from interrupt
2110  * or normal process context.
2111  *
2112  * Returns zero if successful or error if not
2113  *
2114  * Notes:
2115  *      This routine transitions the device to the SDEV_BLOCK state
2116  *      (which must be a legal transition).  When the device is in this
2117  *      state, all commands are deferred until the scsi lld reenables
2118  *      the device with scsi_device_unblock or device_block_tmo fires.
2119  *      This routine assumes the host_lock is held on entry.
2120  **/
2121 int
2122 scsi_internal_device_block(struct scsi_device *sdev)
2123 {
2124         request_queue_t *q = sdev->request_queue;
2125         unsigned long flags;
2126         int err = 0;
2127
2128         err = scsi_device_set_state(sdev, SDEV_BLOCK);
2129         if (err)
2130                 return err;
2131
2132         /*
2133          * The device has transitioned to SDEV_BLOCK.  Stop the
2134          * block layer from calling the midlayer with this device's
2135          * request queue.
2136          */
2137         spin_lock_irqsave(q->queue_lock, flags);
2138         blk_stop_queue(q);
2139         spin_unlock_irqrestore(q->queue_lock, flags);
2140
2141         return 0;
2142 }
2143 EXPORT_SYMBOL_GPL(scsi_internal_device_block);
2144
2145 /**
2146  * scsi_internal_device_unblock - resume a device after a block request
2147  * @sdev:       device to resume
2148  *
2149  * Called by scsi lld's or the midlayer to restart the device queue
2150  * for the previously suspended scsi device.  Called from interrupt or
2151  * normal process context.
2152  *
2153  * Returns zero if successful or error if not.
2154  *
2155  * Notes:
2156  *      This routine transitions the device to the SDEV_RUNNING state
2157  *      (which must be a legal transition) allowing the midlayer to
2158  *      goose the queue for this device.  This routine assumes the
2159  *      host_lock is held upon entry.
2160  **/
2161 int
2162 scsi_internal_device_unblock(struct scsi_device *sdev)
2163 {
2164         request_queue_t *q = sdev->request_queue;
2165         int err;
2166         unsigned long flags;
2167
2168         /*
2169          * Try to transition the scsi device to SDEV_RUNNING
2170          * and goose the device queue if successful.
2171          */
2172         err = scsi_device_set_state(sdev, SDEV_RUNNING);
2173         if (err)
2174                 return err;
2175
2176         spin_lock_irqsave(q->queue_lock, flags);
2177         blk_start_queue(q);
2178         spin_unlock_irqrestore(q->queue_lock, flags);
2179
2180         return 0;
2181 }
2182 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
2183
2184 static void
2185 device_block(struct scsi_device *sdev, void *data)
2186 {
2187         scsi_internal_device_block(sdev);
2188 }
2189
2190 static int
2191 target_block(struct device *dev, void *data)
2192 {
2193         if (scsi_is_target_device(dev))
2194                 starget_for_each_device(to_scsi_target(dev), NULL,
2195                                         device_block);
2196         return 0;
2197 }
2198
2199 void
2200 scsi_target_block(struct device *dev)
2201 {
2202         if (scsi_is_target_device(dev))
2203                 starget_for_each_device(to_scsi_target(dev), NULL,
2204                                         device_block);
2205         else
2206                 device_for_each_child(dev, NULL, target_block);
2207 }
2208 EXPORT_SYMBOL_GPL(scsi_target_block);
2209
2210 static void
2211 device_unblock(struct scsi_device *sdev, void *data)
2212 {
2213         scsi_internal_device_unblock(sdev);
2214 }
2215
2216 static int
2217 target_unblock(struct device *dev, void *data)
2218 {
2219         if (scsi_is_target_device(dev))
2220                 starget_for_each_device(to_scsi_target(dev), NULL,
2221                                         device_unblock);
2222         return 0;
2223 }
2224
2225 void
2226 scsi_target_unblock(struct device *dev)
2227 {
2228         if (scsi_is_target_device(dev))
2229                 starget_for_each_device(to_scsi_target(dev), NULL,
2230                                         device_unblock);
2231         else
2232                 device_for_each_child(dev, NULL, target_unblock);
2233 }
2234 EXPORT_SYMBOL_GPL(scsi_target_unblock);
2235
2236 /**
2237  * scsi_kmap_atomic_sg - find and atomically map an sg-elemnt
2238  * @sg:         scatter-gather list
2239  * @sg_count:   number of segments in sg
2240  * @offset:     offset in bytes into sg, on return offset into the mapped area
2241  * @len:        bytes to map, on return number of bytes mapped
2242  *
2243  * Returns virtual address of the start of the mapped page
2244  */
2245 void *scsi_kmap_atomic_sg(struct scatterlist *sg, int sg_count,
2246                           size_t *offset, size_t *len)
2247 {
2248         int i;
2249         size_t sg_len = 0, len_complete = 0;
2250         struct page *page;
2251
2252         WARN_ON(!irqs_disabled());
2253
2254         for (i = 0; i < sg_count; i++) {
2255                 len_complete = sg_len; /* Complete sg-entries */
2256                 sg_len += sg[i].length;
2257                 if (sg_len > *offset)
2258                         break;
2259         }
2260
2261         if (unlikely(i == sg_count)) {
2262                 printk(KERN_ERR "%s: Bytes in sg: %zu, requested offset %zu, "
2263                         "elements %d\n",
2264                        __FUNCTION__, sg_len, *offset, sg_count);
2265                 WARN_ON(1);
2266                 return NULL;
2267         }
2268
2269         /* Offset starting from the beginning of first page in this sg-entry */
2270         *offset = *offset - len_complete + sg[i].offset;
2271
2272         /* Assumption: contiguous pages can be accessed as "page + i" */
2273         page = nth_page(sg[i].page, (*offset >> PAGE_SHIFT));
2274         *offset &= ~PAGE_MASK;
2275
2276         /* Bytes in this sg-entry from *offset to the end of the page */
2277         sg_len = PAGE_SIZE - *offset;
2278         if (*len > sg_len)
2279                 *len = sg_len;
2280
2281         return kmap_atomic(page, KM_BIO_SRC_IRQ);
2282 }
2283 EXPORT_SYMBOL(scsi_kmap_atomic_sg);
2284
2285 /**
2286  * scsi_kunmap_atomic_sg - atomically unmap a virtual address, previously
2287  *                         mapped with scsi_kmap_atomic_sg
2288  * @virt:       virtual address to be unmapped
2289  */
2290 void scsi_kunmap_atomic_sg(void *virt)
2291 {
2292         kunmap_atomic(virt, KM_BIO_SRC_IRQ);
2293 }
2294 EXPORT_SYMBOL(scsi_kunmap_atomic_sg);