linux/drivers/scsi/scsi_lib.c
<<
>>
Prefs
   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/bitops.h>
  12#include <linux/blkdev.h>
  13#include <linux/completion.h>
  14#include <linux/kernel.h>
  15#include <linux/mempool.h>
  16#include <linux/slab.h>
  17#include <linux/init.h>
  18#include <linux/pci.h>
  19#include <linux/delay.h>
  20#include <linux/hardirq.h>
  21#include <linux/scatterlist.h>
  22
  23#include <scsi/scsi.h>
  24#include <scsi/scsi_cmnd.h>
  25#include <scsi/scsi_dbg.h>
  26#include <scsi/scsi_device.h>
  27#include <scsi/scsi_driver.h>
  28#include <scsi/scsi_eh.h>
  29#include <scsi/scsi_host.h>
  30
  31#include "scsi_priv.h"
  32#include "scsi_logging.h"
  33
  34
  35#define SG_MEMPOOL_NR           ARRAY_SIZE(scsi_sg_pools)
  36#define SG_MEMPOOL_SIZE         2
  37
  38struct scsi_host_sg_pool {
  39        size_t          size;
  40        char            *name;
  41        struct kmem_cache       *slab;
  42        mempool_t       *pool;
  43};
  44
  45#define SP(x) { x, "sgpool-" __stringify(x) }
  46#if (SCSI_MAX_SG_SEGMENTS < 32)
  47#error SCSI_MAX_SG_SEGMENTS is too small (must be 32 or greater)
  48#endif
  49static struct scsi_host_sg_pool scsi_sg_pools[] = {
  50        SP(8),
  51        SP(16),
  52#if (SCSI_MAX_SG_SEGMENTS > 32)
  53        SP(32),
  54#if (SCSI_MAX_SG_SEGMENTS > 64)
  55        SP(64),
  56#if (SCSI_MAX_SG_SEGMENTS > 128)
  57        SP(128),
  58#if (SCSI_MAX_SG_SEGMENTS > 256)
  59#error SCSI_MAX_SG_SEGMENTS is too large (256 MAX)
  60#endif
  61#endif
  62#endif
  63#endif
  64        SP(SCSI_MAX_SG_SEGMENTS)
  65};
  66#undef SP
  67
  68struct kmem_cache *scsi_sdb_cache;
  69
  70static void scsi_run_queue(struct request_queue *q);
  71
  72/*
  73 * Function:    scsi_unprep_request()
  74 *
  75 * Purpose:     Remove all preparation done for a request, including its
  76 *              associated scsi_cmnd, so that it can be requeued.
  77 *
  78 * Arguments:   req     - request to unprepare
  79 *
  80 * Lock status: Assumed that no locks are held upon entry.
  81 *
  82 * Returns:     Nothing.
  83 */
  84static void scsi_unprep_request(struct request *req)
  85{
  86        struct scsi_cmnd *cmd = req->special;
  87
  88        req->cmd_flags &= ~REQ_DONTPREP;
  89        req->special = NULL;
  90
  91        scsi_put_command(cmd);
  92}
  93
  94/**
  95 * __scsi_queue_insert - private queue insertion
  96 * @cmd: The SCSI command being requeued
  97 * @reason:  The reason for the requeue
  98 * @unbusy: Whether the queue should be unbusied
  99 *
 100 * This is a private queue insertion.  The public interface
 101 * scsi_queue_insert() always assumes the queue should be unbusied
 102 * because it's always called before the completion.  This function is
 103 * for a requeue after completion, which should only occur in this
 104 * file.
 105 */
 106static int __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)
 107{
 108        struct Scsi_Host *host = cmd->device->host;
 109        struct scsi_device *device = cmd->device;
 110        struct scsi_target *starget = scsi_target(device);
 111        struct request_queue *q = device->request_queue;
 112        unsigned long flags;
 113
 114        SCSI_LOG_MLQUEUE(1,
 115                 printk("Inserting command %p into mlqueue\n", cmd));
 116
 117        /*
 118         * Set the appropriate busy bit for the device/host.
 119         *
 120         * If the host/device isn't busy, assume that something actually
 121         * completed, and that we should be able to queue a command now.
 122         *
 123         * Note that the prior mid-layer assumption that any host could
 124         * always queue at least one command is now broken.  The mid-layer
 125         * will implement a user specifiable stall (see
 126         * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
 127         * if a command is requeued with no other commands outstanding
 128         * either for the device or for the host.
 129         */
 130        switch (reason) {
 131        case SCSI_MLQUEUE_HOST_BUSY:
 132                host->host_blocked = host->max_host_blocked;
 133                break;
 134        case SCSI_MLQUEUE_DEVICE_BUSY:
 135                device->device_blocked = device->max_device_blocked;
 136                break;
 137        case SCSI_MLQUEUE_TARGET_BUSY:
 138                starget->target_blocked = starget->max_target_blocked;
 139                break;
 140        }
 141
 142        /*
 143         * Decrement the counters, since these commands are no longer
 144         * active on the host/device.
 145         */
 146        if (unbusy)
 147                scsi_device_unbusy(device);
 148
 149        /*
 150         * Requeue this command.  It will go before all other commands
 151         * that are already in the queue.
 152         *
 153         * NOTE: there is magic here about the way the queue is plugged if
 154         * we have no outstanding commands.
 155         * 
 156         * Although we *don't* plug the queue, we call the request
 157         * function.  The SCSI request function detects the blocked condition
 158         * and plugs the queue appropriately.
 159         */
 160        spin_lock_irqsave(q->queue_lock, flags);
 161        blk_requeue_request(q, cmd->request);
 162        spin_unlock_irqrestore(q->queue_lock, flags);
 163
 164        scsi_run_queue(q);
 165
 166        return 0;
 167}
 168
 169/*
 170 * Function:    scsi_queue_insert()
 171 *
 172 * Purpose:     Insert a command in the midlevel queue.
 173 *
 174 * Arguments:   cmd    - command that we are adding to queue.
 175 *              reason - why we are inserting command to queue.
 176 *
 177 * Lock status: Assumed that lock is not held upon entry.
 178 *
 179 * Returns:     Nothing.
 180 *
 181 * Notes:       We do this for one of two cases.  Either the host is busy
 182 *              and it cannot accept any more commands for the time being,
 183 *              or the device returned QUEUE_FULL and can accept no more
 184 *              commands.
 185 * Notes:       This could be called either from an interrupt context or a
 186 *              normal process context.
 187 */
 188int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
 189{
 190        return __scsi_queue_insert(cmd, reason, 1);
 191}
 192/**
 193 * scsi_execute - insert request and wait for the result
 194 * @sdev:       scsi device
 195 * @cmd:        scsi command
 196 * @data_direction: data direction
 197 * @buffer:     data buffer
 198 * @bufflen:    len of buffer
 199 * @sense:      optional sense buffer
 200 * @timeout:    request timeout in seconds
 201 * @retries:    number of times to retry request
 202 * @flags:      or into request flags;
 203 * @resid:      optional residual length
 204 *
 205 * returns the req->errors value which is the scsi_cmnd result
 206 * field.
 207 */
 208int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
 209                 int data_direction, void *buffer, unsigned bufflen,
 210                 unsigned char *sense, int timeout, int retries, int flags,
 211                 int *resid)
 212{
 213        struct request *req;
 214        int write = (data_direction == DMA_TO_DEVICE);
 215        int ret = DRIVER_ERROR << 24;
 216
 217        req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
 218
 219        if (bufflen &&  blk_rq_map_kern(sdev->request_queue, req,
 220                                        buffer, bufflen, __GFP_WAIT))
 221                goto out;
 222
 223        req->cmd_len = COMMAND_SIZE(cmd[0]);
 224        memcpy(req->cmd, cmd, req->cmd_len);
 225        req->sense = sense;
 226        req->sense_len = 0;
 227        req->retries = retries;
 228        req->timeout = timeout;
 229        req->cmd_type = REQ_TYPE_BLOCK_PC;
 230        req->cmd_flags |= flags | REQ_QUIET | REQ_PREEMPT;
 231
 232        /*
 233         * head injection *required* here otherwise quiesce won't work
 234         */
 235        blk_execute_rq(req->q, NULL, req, 1);
 236
 237        /*
 238         * Some devices (USB mass-storage in particular) may transfer
 239         * garbage data together with a residue indicating that the data
 240         * is invalid.  Prevent the garbage from being misinterpreted
 241         * and prevent security leaks by zeroing out the excess data.
 242         */
 243        if (unlikely(req->resid_len > 0 && req->resid_len <= bufflen))
 244                memset(buffer + (bufflen - req->resid_len), 0, req->resid_len);
 245
 246        if (resid)
 247                *resid = req->resid_len;
 248        ret = req->errors;
 249 out:
 250        blk_put_request(req);
 251
 252        return ret;
 253}
 254EXPORT_SYMBOL(scsi_execute);
 255
 256
 257int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
 258                     int data_direction, void *buffer, unsigned bufflen,
 259                     struct scsi_sense_hdr *sshdr, int timeout, int retries,
 260                     int *resid)
 261{
 262        char *sense = NULL;
 263        int result;
 264        
 265        if (sshdr) {
 266                sense = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
 267                if (!sense)
 268                        return DRIVER_ERROR << 24;
 269        }
 270        result = scsi_execute(sdev, cmd, data_direction, buffer, bufflen,
 271                              sense, timeout, retries, 0, resid);
 272        if (sshdr)
 273                scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, sshdr);
 274
 275        kfree(sense);
 276        return result;
 277}
 278EXPORT_SYMBOL(scsi_execute_req);
 279
 280/*
 281 * Function:    scsi_init_cmd_errh()
 282 *
 283 * Purpose:     Initialize cmd fields related to error handling.
 284 *
 285 * Arguments:   cmd     - command that is ready to be queued.
 286 *
 287 * Notes:       This function has the job of initializing a number of
 288 *              fields related to error handling.   Typically this will
 289 *              be called once for each command, as required.
 290 */
 291static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
 292{
 293        cmd->serial_number = 0;
 294        scsi_set_resid(cmd, 0);
 295        memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
 296        if (cmd->cmd_len == 0)
 297                cmd->cmd_len = scsi_command_size(cmd->cmnd);
 298}
 299
 300void scsi_device_unbusy(struct scsi_device *sdev)
 301{
 302        struct Scsi_Host *shost = sdev->host;
 303        struct scsi_target *starget = scsi_target(sdev);
 304        unsigned long flags;
 305
 306        spin_lock_irqsave(shost->host_lock, flags);
 307        shost->host_busy--;
 308        starget->target_busy--;
 309        if (unlikely(scsi_host_in_recovery(shost) &&
 310                     (shost->host_failed || shost->host_eh_scheduled)))
 311                scsi_eh_wakeup(shost);
 312        spin_unlock(shost->host_lock);
 313        spin_lock(sdev->request_queue->queue_lock);
 314        sdev->device_busy--;
 315        spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
 316}
 317
 318/*
 319 * Called for single_lun devices on IO completion. Clear starget_sdev_user,
 320 * and call blk_run_queue for all the scsi_devices on the target -
 321 * including current_sdev first.
 322 *
 323 * Called with *no* scsi locks held.
 324 */
 325static void scsi_single_lun_run(struct scsi_device *current_sdev)
 326{
 327        struct Scsi_Host *shost = current_sdev->host;
 328        struct scsi_device *sdev, *tmp;
 329        struct scsi_target *starget = scsi_target(current_sdev);
 330        unsigned long flags;
 331
 332        spin_lock_irqsave(shost->host_lock, flags);
 333        starget->starget_sdev_user = NULL;
 334        spin_unlock_irqrestore(shost->host_lock, flags);
 335
 336        /*
 337         * Call blk_run_queue for all LUNs on the target, starting with
 338         * current_sdev. We race with others (to set starget_sdev_user),
 339         * but in most cases, we will be first. Ideally, each LU on the
 340         * target would get some limited time or requests on the target.
 341         */
 342        blk_run_queue(current_sdev->request_queue);
 343
 344        spin_lock_irqsave(shost->host_lock, flags);
 345        if (starget->starget_sdev_user)
 346                goto out;
 347        list_for_each_entry_safe(sdev, tmp, &starget->devices,
 348                        same_target_siblings) {
 349                if (sdev == current_sdev)
 350                        continue;
 351                if (scsi_device_get(sdev))
 352                        continue;
 353
 354                spin_unlock_irqrestore(shost->host_lock, flags);
 355                blk_run_queue(sdev->request_queue);
 356                spin_lock_irqsave(shost->host_lock, flags);
 357        
 358                scsi_device_put(sdev);
 359        }
 360 out:
 361        spin_unlock_irqrestore(shost->host_lock, flags);
 362}
 363
 364static inline int scsi_device_is_busy(struct scsi_device *sdev)
 365{
 366        if (sdev->device_busy >= sdev->queue_depth || sdev->device_blocked)
 367                return 1;
 368
 369        return 0;
 370}
 371
 372static inline int scsi_target_is_busy(struct scsi_target *starget)
 373{
 374        return ((starget->can_queue > 0 &&
 375                 starget->target_busy >= starget->can_queue) ||
 376                 starget->target_blocked);
 377}
 378
 379static inline int scsi_host_is_busy(struct Scsi_Host *shost)
 380{
 381        if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
 382            shost->host_blocked || shost->host_self_blocked)
 383                return 1;
 384
 385        return 0;
 386}
 387
 388/*
 389 * Function:    scsi_run_queue()
 390 *
 391 * Purpose:     Select a proper request queue to serve next
 392 *
 393 * Arguments:   q       - last request's queue
 394 *
 395 * Returns:     Nothing
 396 *
 397 * Notes:       The previous command was completely finished, start
 398 *              a new one if possible.
 399 */
 400static void scsi_run_queue(struct request_queue *q)
 401{
 402        struct scsi_device *sdev = q->queuedata;
 403        struct Scsi_Host *shost = sdev->host;
 404        LIST_HEAD(starved_list);
 405        unsigned long flags;
 406
 407        if (scsi_target(sdev)->single_lun)
 408                scsi_single_lun_run(sdev);
 409
 410        spin_lock_irqsave(shost->host_lock, flags);
 411        list_splice_init(&shost->starved_list, &starved_list);
 412
 413        while (!list_empty(&starved_list)) {
 414                int flagset;
 415
 416                /*
 417                 * As long as shost is accepting commands and we have
 418                 * starved queues, call blk_run_queue. scsi_request_fn
 419                 * drops the queue_lock and can add us back to the
 420                 * starved_list.
 421                 *
 422                 * host_lock protects the starved_list and starved_entry.
 423                 * scsi_request_fn must get the host_lock before checking
 424                 * or modifying starved_list or starved_entry.
 425                 */
 426                if (scsi_host_is_busy(shost))
 427                        break;
 428
 429                sdev = list_entry(starved_list.next,
 430                                  struct scsi_device, starved_entry);
 431                list_del_init(&sdev->starved_entry);
 432                if (scsi_target_is_busy(scsi_target(sdev))) {
 433                        list_move_tail(&sdev->starved_entry,
 434                                       &shost->starved_list);
 435                        continue;
 436                }
 437
 438                spin_unlock(shost->host_lock);
 439
 440                spin_lock(sdev->request_queue->queue_lock);
 441                flagset = test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) &&
 442                                !test_bit(QUEUE_FLAG_REENTER,
 443                                        &sdev->request_queue->queue_flags);
 444                if (flagset)
 445                        queue_flag_set(QUEUE_FLAG_REENTER, sdev->request_queue);
 446                __blk_run_queue(sdev->request_queue);
 447                if (flagset)
 448                        queue_flag_clear(QUEUE_FLAG_REENTER, sdev->request_queue);
 449                spin_unlock(sdev->request_queue->queue_lock);
 450
 451                spin_lock(shost->host_lock);
 452        }
 453        /* put any unprocessed entries back */
 454        list_splice(&starved_list, &shost->starved_list);
 455        spin_unlock_irqrestore(shost->host_lock, flags);
 456
 457        blk_run_queue(q);
 458}
 459
 460/*
 461 * Function:    scsi_requeue_command()
 462 *
 463 * Purpose:     Handle post-processing of completed commands.
 464 *
 465 * Arguments:   q       - queue to operate on
 466 *              cmd     - command that may need to be requeued.
 467 *
 468 * Returns:     Nothing
 469 *
 470 * Notes:       After command completion, there may be blocks left
 471 *              over which weren't finished by the previous command
 472 *              this can be for a number of reasons - the main one is
 473 *              I/O errors in the middle of the request, in which case
 474 *              we need to request the blocks that come after the bad
 475 *              sector.
 476 * Notes:       Upon return, cmd is a stale pointer.
 477 */
 478static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
 479{
 480        struct request *req = cmd->request;
 481        unsigned long flags;
 482
 483        spin_lock_irqsave(q->queue_lock, flags);
 484        scsi_unprep_request(req);
 485        blk_requeue_request(q, req);
 486        spin_unlock_irqrestore(q->queue_lock, flags);
 487
 488        scsi_run_queue(q);
 489}
 490
 491void scsi_next_command(struct scsi_cmnd *cmd)
 492{
 493        struct scsi_device *sdev = cmd->device;
 494        struct request_queue *q = sdev->request_queue;
 495
 496        /* need to hold a reference on the device before we let go of the cmd */
 497        get_device(&sdev->sdev_gendev);
 498
 499        scsi_put_command(cmd);
 500        scsi_run_queue(q);
 501
 502        /* ok to remove device now */
 503        put_device(&sdev->sdev_gendev);
 504}
 505
 506void scsi_run_host_queues(struct Scsi_Host *shost)
 507{
 508        struct scsi_device *sdev;
 509
 510        shost_for_each_device(sdev, shost)
 511                scsi_run_queue(sdev->request_queue);
 512}
 513
 514static void __scsi_release_buffers(struct scsi_cmnd *, int);
 515
 516/*
 517 * Function:    scsi_end_request()
 518 *
 519 * Purpose:     Post-processing of completed commands (usually invoked at end
 520 *              of upper level post-processing and scsi_io_completion).
 521 *
 522 * Arguments:   cmd      - command that is complete.
 523 *              error    - 0 if I/O indicates success, < 0 for I/O error.
 524 *              bytes    - number of bytes of completed I/O
 525 *              requeue  - indicates whether we should requeue leftovers.
 526 *
 527 * Lock status: Assumed that lock is not held upon entry.
 528 *
 529 * Returns:     cmd if requeue required, NULL otherwise.
 530 *
 531 * Notes:       This is called for block device requests in order to
 532 *              mark some number of sectors as complete.
 533 * 
 534 *              We are guaranteeing that the request queue will be goosed
 535 *              at some point during this call.
 536 * Notes:       If cmd was requeued, upon return it will be a stale pointer.
 537 */
 538static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
 539                                          int bytes, int requeue)
 540{
 541        struct request_queue *q = cmd->device->request_queue;
 542        struct request *req = cmd->request;
 543
 544        /*
 545         * If there are blocks left over at the end, set up the command
 546         * to queue the remainder of them.
 547         */
 548        if (blk_end_request(req, error, bytes)) {
 549                /* kill remainder if no retrys */
 550                if (error && scsi_noretry_cmd(cmd))
 551                        blk_end_request_all(req, error);
 552                else {
 553                        if (requeue) {
 554                                /*
 555                                 * Bleah.  Leftovers again.  Stick the
 556                                 * leftovers in the front of the
 557                                 * queue, and goose the queue again.
 558                                 */
 559                                scsi_release_buffers(cmd);
 560                                scsi_requeue_command(q, cmd);
 561                                cmd = NULL;
 562                        }
 563                        return cmd;
 564                }
 565        }
 566
 567        /*
 568         * This will goose the queue request function at the end, so we don't
 569         * need to worry about launching another command.
 570         */
 571        __scsi_release_buffers(cmd, 0);
 572        scsi_next_command(cmd);
 573        return NULL;
 574}
 575
 576static inline unsigned int scsi_sgtable_index(unsigned short nents)
 577{
 578        unsigned int index;
 579
 580        BUG_ON(nents > SCSI_MAX_SG_SEGMENTS);
 581
 582        if (nents <= 8)
 583                index = 0;
 584        else
 585                index = get_count_order(nents) - 3;
 586
 587        return index;
 588}
 589
 590static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)
 591{
 592        struct scsi_host_sg_pool *sgp;
 593
 594        sgp = scsi_sg_pools + scsi_sgtable_index(nents);
 595        mempool_free(sgl, sgp->pool);
 596}
 597
 598static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
 599{
 600        struct scsi_host_sg_pool *sgp;
 601
 602        sgp = scsi_sg_pools + scsi_sgtable_index(nents);
 603        return mempool_alloc(sgp->pool, gfp_mask);
 604}
 605
 606static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents,
 607                              gfp_t gfp_mask)
 608{
 609        int ret;
 610
 611        BUG_ON(!nents);
 612
 613        ret = __sg_alloc_table(&sdb->table, nents, SCSI_MAX_SG_SEGMENTS,
 614                               gfp_mask, scsi_sg_alloc);
 615        if (unlikely(ret))
 616                __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS,
 617                                scsi_sg_free);
 618
 619        return ret;
 620}
 621
 622static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
 623{
 624        __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
 625}
 626
 627static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
 628{
 629
 630        if (cmd->sdb.table.nents)
 631                scsi_free_sgtable(&cmd->sdb);
 632
 633        memset(&cmd->sdb, 0, sizeof(cmd->sdb));
 634
 635        if (do_bidi_check && scsi_bidi_cmnd(cmd)) {
 636                struct scsi_data_buffer *bidi_sdb =
 637                        cmd->request->next_rq->special;
 638                scsi_free_sgtable(bidi_sdb);
 639                kmem_cache_free(scsi_sdb_cache, bidi_sdb);
 640                cmd->request->next_rq->special = NULL;
 641        }
 642
 643        if (scsi_prot_sg_count(cmd))
 644                scsi_free_sgtable(cmd->prot_sdb);
 645}
 646
 647/*
 648 * Function:    scsi_release_buffers()
 649 *
 650 * Purpose:     Completion processing for block device I/O requests.
 651 *
 652 * Arguments:   cmd     - command that we are bailing.
 653 *
 654 * Lock status: Assumed that no lock is held upon entry.
 655 *
 656 * Returns:     Nothing
 657 *
 658 * Notes:       In the event that an upper level driver rejects a
 659 *              command, we must release resources allocated during
 660 *              the __init_io() function.  Primarily this would involve
 661 *              the scatter-gather table, and potentially any bounce
 662 *              buffers.
 663 */
 664void scsi_release_buffers(struct scsi_cmnd *cmd)
 665{
 666        __scsi_release_buffers(cmd, 1);
 667}
 668EXPORT_SYMBOL(scsi_release_buffers);
 669
 670/*
 671 * Function:    scsi_io_completion()
 672 *
 673 * Purpose:     Completion processing for block device I/O requests.
 674 *
 675 * Arguments:   cmd   - command that is finished.
 676 *
 677 * Lock status: Assumed that no lock is held upon entry.
 678 *
 679 * Returns:     Nothing
 680 *
 681 * Notes:       This function is matched in terms of capabilities to
 682 *              the function that created the scatter-gather list.
 683 *              In other words, if there are no bounce buffers
 684 *              (the normal case for most drivers), we don't need
 685 *              the logic to deal with cleaning up afterwards.
 686 *
 687 *              We must call scsi_end_request().  This will finish off
 688 *              the specified number of sectors.  If we are done, the
 689 *              command block will be released and the queue function
 690 *              will be goosed.  If we are not done then we have to
 691 *              figure out what to do next:
 692 *
 693 *              a) We can call scsi_requeue_command().  The request
 694 *                 will be unprepared and put back on the queue.  Then
 695 *                 a new command will be created for it.  This should
 696 *                 be used if we made forward progress, or if we want
 697 *                 to switch from READ(10) to READ(6) for example.
 698 *
 699 *              b) We can call scsi_queue_insert().  The request will
 700 *                 be put back on the queue and retried using the same
 701 *                 command as before, possibly after a delay.
 702 *
 703 *              c) We can call blk_end_request() with -EIO to fail
 704 *                 the remainder of the request.
 705 */
 706void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 707{
 708        int result = cmd->result;
 709        struct request_queue *q = cmd->device->request_queue;
 710        struct request *req = cmd->request;
 711        int error = 0;
 712        struct scsi_sense_hdr sshdr;
 713        int sense_valid = 0;
 714        int sense_deferred = 0;
 715        enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
 716              ACTION_DELAYED_RETRY} action;
 717        char *description = NULL;
 718
 719        if (result) {
 720                sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
 721                if (sense_valid)
 722                        sense_deferred = scsi_sense_is_deferred(&sshdr);
 723        }
 724
 725        if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
 726                req->errors = result;
 727                if (result) {
 728                        if (sense_valid && req->sense) {
 729                                /*
 730                                 * SG_IO wants current and deferred errors
 731                                 */
 732                                int len = 8 + cmd->sense_buffer[7];
 733
 734                                if (len > SCSI_SENSE_BUFFERSIZE)
 735                                        len = SCSI_SENSE_BUFFERSIZE;
 736                                memcpy(req->sense, cmd->sense_buffer,  len);
 737                                req->sense_len = len;
 738                        }
 739                        if (!sense_deferred)
 740                                error = -EIO;
 741                }
 742
 743                req->resid_len = scsi_get_resid(cmd);
 744
 745                if (scsi_bidi_cmnd(cmd)) {
 746                        /*
 747                         * Bidi commands Must be complete as a whole,
 748                         * both sides at once.
 749                         */
 750                        req->next_rq->resid_len = scsi_in(cmd)->resid;
 751
 752                        blk_end_request_all(req, 0);
 753
 754                        scsi_release_buffers(cmd);
 755                        scsi_next_command(cmd);
 756                        return;
 757                }
 758        }
 759
 760        BUG_ON(blk_bidi_rq(req)); /* bidi not support for !blk_pc_request yet */
 761
 762        /*
 763         * Next deal with any sectors which we were able to correctly
 764         * handle.
 765         */
 766        SCSI_LOG_HLCOMPLETE(1, printk("%u sectors total, "
 767                                      "%d bytes done.\n",
 768                                      blk_rq_sectors(req), good_bytes));
 769
 770        /*
 771         * Recovered errors need reporting, but they're always treated
 772         * as success, so fiddle the result code here.  For BLOCK_PC
 773         * we already took a copy of the original into rq->errors which
 774         * is what gets returned to the user
 775         */
 776        if (sense_valid && sshdr.sense_key == RECOVERED_ERROR) {
 777                if (!(req->cmd_flags & REQ_QUIET))
 778                        scsi_print_sense("", cmd);
 779                result = 0;
 780                /* BLOCK_PC may have set error */
 781                error = 0;
 782        }
 783
 784        /*
 785         * A number of bytes were successfully read.  If there
 786         * are leftovers and there is some kind of error
 787         * (result != 0), retry the rest.
 788         */
 789        if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
 790                return;
 791
 792        error = -EIO;
 793
 794        if (host_byte(result) == DID_RESET) {
 795                /* Third party bus reset or reset for error recovery
 796                 * reasons.  Just retry the command and see what
 797                 * happens.
 798                 */
 799                action = ACTION_RETRY;
 800        } else if (sense_valid && !sense_deferred) {
 801                switch (sshdr.sense_key) {
 802                case UNIT_ATTENTION:
 803                        if (cmd->device->removable) {
 804                                /* Detected disc change.  Set a bit
 805                                 * and quietly refuse further access.
 806                                 */
 807                                cmd->device->changed = 1;
 808                                description = "Media Changed";
 809                                action = ACTION_FAIL;
 810                        } else {
 811                                /* Must have been a power glitch, or a
 812                                 * bus reset.  Could not have been a
 813                                 * media change, so we just retry the
 814                                 * command and see what happens.
 815                                 */
 816                                action = ACTION_RETRY;
 817                        }
 818                        break;
 819                case ILLEGAL_REQUEST:
 820                        /* If we had an ILLEGAL REQUEST returned, then
 821                         * we may have performed an unsupported
 822                         * command.  The only thing this should be
 823                         * would be a ten byte read where only a six
 824                         * byte read was supported.  Also, on a system
 825                         * where READ CAPACITY failed, we may have
 826                         * read past the end of the disk.
 827                         */
 828                        if ((cmd->device->use_10_for_rw &&
 829                            sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
 830                            (cmd->cmnd[0] == READ_10 ||
 831                             cmd->cmnd[0] == WRITE_10)) {
 832                                /* This will issue a new 6-byte command. */
 833                                cmd->device->use_10_for_rw = 0;
 834                                action = ACTION_REPREP;
 835                        } else if (sshdr.asc == 0x10) /* DIX */ {
 836                                description = "Host Data Integrity Failure";
 837                                action = ACTION_FAIL;
 838                                error = -EILSEQ;
 839                        } else
 840                                action = ACTION_FAIL;
 841                        break;
 842                case ABORTED_COMMAND:
 843                        action = ACTION_FAIL;
 844                        if (sshdr.asc == 0x10) { /* DIF */
 845                                description = "Target Data Integrity Failure";
 846                                error = -EILSEQ;
 847                        }
 848                        break;
 849                case NOT_READY:
 850                        /* If the device is in the process of becoming
 851                         * ready, or has a temporary blockage, retry.
 852                         */
 853                        if (sshdr.asc == 0x04) {
 854                                switch (sshdr.ascq) {
 855                                case 0x01: /* becoming ready */
 856                                case 0x04: /* format in progress */
 857                                case 0x05: /* rebuild in progress */
 858                                case 0x06: /* recalculation in progress */
 859                                case 0x07: /* operation in progress */
 860                                case 0x08: /* Long write in progress */
 861                                case 0x09: /* self test in progress */
 862                                        action = ACTION_DELAYED_RETRY;
 863                                        break;
 864                                default:
 865                                        description = "Device not ready";
 866                                        action = ACTION_FAIL;
 867                                        break;
 868                                }
 869                        } else {
 870                                description = "Device not ready";
 871                                action = ACTION_FAIL;
 872                        }
 873                        break;
 874                case VOLUME_OVERFLOW:
 875                        /* See SSC3rXX or current. */
 876                        action = ACTION_FAIL;
 877                        break;
 878                default:
 879                        description = "Unhandled sense code";
 880                        action = ACTION_FAIL;
 881                        break;
 882                }
 883        } else {
 884                description = "Unhandled error code";
 885                action = ACTION_FAIL;
 886        }
 887
 888        switch (action) {
 889        case ACTION_FAIL:
 890                /* Give up and fail the remainder of the request */
 891                scsi_release_buffers(cmd);
 892                if (!(req->cmd_flags & REQ_QUIET)) {
 893                        if (description)
 894                                scmd_printk(KERN_INFO, cmd, "%s\n",
 895                                            description);
 896                        scsi_print_result(cmd);
 897                        if (driver_byte(result) & DRIVER_SENSE)
 898                                scsi_print_sense("", cmd);
 899                        scsi_print_command(cmd);
 900                }
 901                if (blk_end_request_err(req, -EIO))
 902                        scsi_requeue_command(q, cmd);
 903                else
 904                        scsi_next_command(cmd);
 905                break;
 906        case ACTION_REPREP:
 907                /* Unprep the request and put it back at the head of the queue.
 908                 * A new command will be prepared and issued.
 909                 */
 910                scsi_release_buffers(cmd);
 911                scsi_requeue_command(q, cmd);
 912                break;
 913        case ACTION_RETRY:
 914                /* Retry the same command immediately */
 915                __scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, 0);
 916                break;
 917        case ACTION_DELAYED_RETRY:
 918                /* Retry the same command after a delay */
 919                __scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, 0);
 920                break;
 921        }
 922}
 923
 924static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
 925                             gfp_t gfp_mask)
 926{
 927        int count;
 928
 929        /*
 930         * If sg table allocation fails, requeue request later.
 931         */
 932        if (unlikely(scsi_alloc_sgtable(sdb, req->nr_phys_segments,
 933                                        gfp_mask))) {
 934                return BLKPREP_DEFER;
 935        }
 936
 937        req->buffer = NULL;
 938
 939        /* 
 940         * Next, walk the list, and fill in the addresses and sizes of
 941         * each segment.
 942         */
 943        count = blk_rq_map_sg(req->q, req, sdb->table.sgl);
 944        BUG_ON(count > sdb->table.nents);
 945        sdb->table.nents = count;
 946        sdb->length = blk_rq_bytes(req);
 947        return BLKPREP_OK;
 948}
 949
 950/*
 951 * Function:    scsi_init_io()
 952 *
 953 * Purpose:     SCSI I/O initialize function.
 954 *
 955 * Arguments:   cmd   - Command descriptor we wish to initialize
 956 *
 957 * Returns:     0 on success
 958 *              BLKPREP_DEFER if the failure is retryable
 959 *              BLKPREP_KILL if the failure is fatal
 960 */
 961int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
 962{
 963        int error = scsi_init_sgtable(cmd->request, &cmd->sdb, gfp_mask);
 964        if (error)
 965                goto err_exit;
 966
 967        if (blk_bidi_rq(cmd->request)) {
 968                struct scsi_data_buffer *bidi_sdb = kmem_cache_zalloc(
 969                        scsi_sdb_cache, GFP_ATOMIC);
 970                if (!bidi_sdb) {
 971                        error = BLKPREP_DEFER;
 972                        goto err_exit;
 973                }
 974
 975                cmd->request->next_rq->special = bidi_sdb;
 976                error = scsi_init_sgtable(cmd->request->next_rq, bidi_sdb,
 977                                                                    GFP_ATOMIC);
 978                if (error)
 979                        goto err_exit;
 980        }
 981
 982        if (blk_integrity_rq(cmd->request)) {
 983                struct scsi_data_buffer *prot_sdb = cmd->prot_sdb;
 984                int ivecs, count;
 985
 986                BUG_ON(prot_sdb == NULL);
 987                ivecs = blk_rq_count_integrity_sg(cmd->request);
 988
 989                if (scsi_alloc_sgtable(prot_sdb, ivecs, gfp_mask)) {
 990                        error = BLKPREP_DEFER;
 991                        goto err_exit;
 992                }
 993
 994                count = blk_rq_map_integrity_sg(cmd->request,
 995                                                prot_sdb->table.sgl);
 996                BUG_ON(unlikely(count > ivecs));
 997
 998                cmd->prot_sdb = prot_sdb;
 999                cmd->prot_sdb->table.nents = count;
1000        }
1001
1002        return BLKPREP_OK ;
1003
1004err_exit:
1005        scsi_release_buffers(cmd);
1006        if (error == BLKPREP_KILL)
1007                scsi_put_command(cmd);
1008        else /* BLKPREP_DEFER */
1009                scsi_unprep_request(cmd->request);
1010
1011        return error;
1012}
1013EXPORT_SYMBOL(scsi_init_io);
1014
1015static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
1016                struct request *req)
1017{
1018        struct scsi_cmnd *cmd;
1019
1020        if (!req->special) {
1021                cmd = scsi_get_command(sdev, GFP_ATOMIC);
1022                if (unlikely(!cmd))
1023                        return NULL;
1024                req->special = cmd;
1025        } else {
1026                cmd = req->special;
1027        }
1028
1029        /* pull a tag out of the request if we have one */
1030        cmd->tag = req->tag;
1031        cmd->request = req;
1032
1033        cmd->cmnd = req->cmd;
1034
1035        return cmd;
1036}
1037
1038int scsi_setup_blk_pc_cmnd(struct scsi_device *sdev, struct request *req)
1039{
1040        struct scsi_cmnd *cmd;
1041        int ret = scsi_prep_state_check(sdev, req);
1042
1043        if (ret != BLKPREP_OK)
1044                return ret;
1045
1046        cmd = scsi_get_cmd_from_req(sdev, req);
1047        if (unlikely(!cmd))
1048                return BLKPREP_DEFER;
1049
1050        /*
1051         * BLOCK_PC requests may transfer data, in which case they must
1052         * a bio attached to them.  Or they might contain a SCSI command
1053         * that does not transfer data, in which case they may optionally
1054         * submit a request without an attached bio.
1055         */
1056        if (req->bio) {
1057                int ret;
1058
1059                BUG_ON(!req->nr_phys_segments);
1060
1061                ret = scsi_init_io(cmd, GFP_ATOMIC);
1062                if (unlikely(ret))
1063                        return ret;
1064        } else {
1065                BUG_ON(blk_rq_bytes(req));
1066
1067                memset(&cmd->sdb, 0, sizeof(cmd->sdb));
1068                req->buffer = NULL;
1069        }
1070
1071        cmd->cmd_len = req->cmd_len;
1072        if (!blk_rq_bytes(req))
1073                cmd->sc_data_direction = DMA_NONE;
1074        else if (rq_data_dir(req) == WRITE)
1075                cmd->sc_data_direction = DMA_TO_DEVICE;
1076        else
1077                cmd->sc_data_direction = DMA_FROM_DEVICE;
1078        
1079        cmd->transfersize = blk_rq_bytes(req);
1080        cmd->allowed = req->retries;
1081        return BLKPREP_OK;
1082}
1083EXPORT_SYMBOL(scsi_setup_blk_pc_cmnd);
1084
1085/*
1086 * Setup a REQ_TYPE_FS command.  These are simple read/write request
1087 * from filesystems that still need to be translated to SCSI CDBs from
1088 * the ULD.
1089 */
1090int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
1091{
1092        struct scsi_cmnd *cmd;
1093        int ret = scsi_prep_state_check(sdev, req);
1094
1095        if (ret != BLKPREP_OK)
1096                return ret;
1097
1098        if (unlikely(sdev->scsi_dh_data && sdev->scsi_dh_data->scsi_dh
1099                         && sdev->scsi_dh_data->scsi_dh->prep_fn)) {
1100                ret = sdev->scsi_dh_data->scsi_dh->prep_fn(sdev, req);
1101                if (ret != BLKPREP_OK)
1102                        return ret;
1103        }
1104
1105        /*
1106         * Filesystem requests must transfer data.
1107         */
1108        BUG_ON(!req->nr_phys_segments);
1109
1110        cmd = scsi_get_cmd_from_req(sdev, req);
1111        if (unlikely(!cmd))
1112                return BLKPREP_DEFER;
1113
1114        memset(cmd->cmnd, 0, BLK_MAX_CDB);
1115        return scsi_init_io(cmd, GFP_ATOMIC);
1116}
1117EXPORT_SYMBOL(scsi_setup_fs_cmnd);
1118
1119int scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
1120{
1121        int ret = BLKPREP_OK;
1122
1123        /*
1124         * If the device is not in running state we will reject some
1125         * or all commands.
1126         */
1127        if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
1128                switch (sdev->sdev_state) {
1129                case SDEV_OFFLINE:
1130                        /*
1131                         * If the device is offline we refuse to process any
1132                         * commands.  The device must be brought online
1133                         * before trying any recovery commands.
1134                         */
1135                        sdev_printk(KERN_ERR, sdev,
1136                                    "rejecting I/O to offline device\n");
1137                        ret = BLKPREP_KILL;
1138                        break;
1139                case SDEV_DEL:
1140                        /*
1141                         * If the device is fully deleted, we refuse to
1142                         * process any commands as well.
1143                         */
1144                        sdev_printk(KERN_ERR, sdev,
1145                                    "rejecting I/O to dead device\n");
1146                        ret = BLKPREP_KILL;
1147                        break;
1148                case SDEV_QUIESCE:
1149                case SDEV_BLOCK:
1150                case SDEV_CREATED_BLOCK:
1151                        /*
1152                         * If the devices is blocked we defer normal commands.
1153                         */
1154                        if (!(req->cmd_flags & REQ_PREEMPT))
1155                                ret = BLKPREP_DEFER;
1156                        break;
1157                default:
1158                        /*
1159                         * For any other not fully online state we only allow
1160                         * special commands.  In particular any user initiated
1161                         * command is not allowed.
1162                         */
1163                        if (!(req->cmd_flags & REQ_PREEMPT))
1164                                ret = BLKPREP_KILL;
1165                        break;
1166                }
1167        }
1168        return ret;
1169}
1170EXPORT_SYMBOL(scsi_prep_state_check);
1171
1172int scsi_prep_return(struct request_queue *q, struct request *req, int ret)
1173{
1174        struct scsi_device *sdev = q->queuedata;
1175
1176        switch (ret) {
1177        case BLKPREP_KILL:
1178                req->errors = DID_NO_CONNECT << 16;
1179                /* release the command and kill it */
1180                if (req->special) {
1181                        struct scsi_cmnd *cmd = req->special;
1182                        scsi_release_buffers(cmd);
1183                        scsi_put_command(cmd);
1184                        req->special = NULL;
1185                }
1186                break;
1187        case BLKPREP_DEFER:
1188                /*
1189                 * If we defer, the blk_peek_request() returns NULL, but the
1190                 * queue must be restarted, so we plug here if no returning
1191                 * command will automatically do that.
1192                 */
1193                if (sdev->device_busy == 0)
1194                        blk_plug_device(q);
1195                break;
1196        default:
1197                req->cmd_flags |= REQ_DONTPREP;
1198        }
1199
1200        return ret;
1201}
1202EXPORT_SYMBOL(scsi_prep_return);
1203
1204int scsi_prep_fn(struct request_queue *q, struct request *req)
1205{
1206        struct scsi_device *sdev = q->queuedata;
1207        int ret = BLKPREP_KILL;
1208
1209        if (req->cmd_type == REQ_TYPE_BLOCK_PC)
1210                ret = scsi_setup_blk_pc_cmnd(sdev, req);
1211        return scsi_prep_return(q, req, ret);
1212}
1213EXPORT_SYMBOL(scsi_prep_fn);
1214
1215/*
1216 * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1217 * return 0.
1218 *
1219 * Called with the queue_lock held.
1220 */
1221static inline int scsi_dev_queue_ready(struct request_queue *q,
1222                                  struct scsi_device *sdev)
1223{
1224        if (sdev->device_busy == 0 && sdev->device_blocked) {
1225                /*
1226                 * unblock after device_blocked iterates to zero
1227                 */
1228                if (--sdev->device_blocked == 0) {
1229                        SCSI_LOG_MLQUEUE(3,
1230                                   sdev_printk(KERN_INFO, sdev,
1231                                   "unblocking device at zero depth\n"));
1232                } else {
1233                        blk_plug_device(q);
1234                        return 0;
1235                }
1236        }
1237        if (scsi_device_is_busy(sdev))
1238                return 0;
1239
1240        return 1;
1241}
1242
1243
1244/*
1245 * scsi_target_queue_ready: checks if there we can send commands to target
1246 * @sdev: scsi device on starget to check.
1247 *
1248 * Called with the host lock held.
1249 */
1250static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
1251                                           struct scsi_device *sdev)
1252{
1253        struct scsi_target *starget = scsi_target(sdev);
1254
1255        if (starget->single_lun) {
1256                if (starget->starget_sdev_user &&
1257                    starget->starget_sdev_user != sdev)
1258                        return 0;
1259                starget->starget_sdev_user = sdev;
1260        }
1261
1262        if (starget->target_busy == 0 && starget->target_blocked) {
1263                /*
1264                 * unblock after target_blocked iterates to zero
1265                 */
1266                if (--starget->target_blocked == 0) {
1267                        SCSI_LOG_MLQUEUE(3, starget_printk(KERN_INFO, starget,
1268                                         "unblocking target at zero depth\n"));
1269                } else
1270                        return 0;
1271        }
1272
1273        if (scsi_target_is_busy(starget)) {
1274                if (list_empty(&sdev->starved_entry)) {
1275                        list_add_tail(&sdev->starved_entry,
1276                                      &shost->starved_list);
1277                        return 0;
1278                }
1279        }
1280
1281        /* We're OK to process the command, so we can't be starved */
1282        if (!list_empty(&sdev->starved_entry))
1283                list_del_init(&sdev->starved_entry);
1284        return 1;
1285}
1286
1287/*
1288 * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1289 * return 0. We must end up running the queue again whenever 0 is
1290 * returned, else IO can hang.
1291 *
1292 * Called with host_lock held.
1293 */
1294static inline int scsi_host_queue_ready(struct request_queue *q,
1295                                   struct Scsi_Host *shost,
1296                                   struct scsi_device *sdev)
1297{
1298        if (scsi_host_in_recovery(shost))
1299                return 0;
1300        if (shost->host_busy == 0 && shost->host_blocked) {
1301                /*
1302                 * unblock after host_blocked iterates to zero
1303                 */
1304                if (--shost->host_blocked == 0) {
1305                        SCSI_LOG_MLQUEUE(3,
1306                                printk("scsi%d unblocking host at zero depth\n",
1307                                        shost->host_no));
1308                } else {
1309                        return 0;
1310                }
1311        }
1312        if (scsi_host_is_busy(shost)) {
1313                if (list_empty(&sdev->starved_entry))
1314                        list_add_tail(&sdev->starved_entry, &shost->starved_list);
1315                return 0;
1316        }
1317
1318        /* We're OK to process the command, so we can't be starved */
1319        if (!list_empty(&sdev->starved_entry))
1320                list_del_init(&sdev->starved_entry);
1321
1322        return 1;
1323}
1324
1325/*
1326 * Busy state exporting function for request stacking drivers.
1327 *
1328 * For efficiency, no lock is taken to check the busy state of
1329 * shost/starget/sdev, since the returned value is not guaranteed and
1330 * may be changed after request stacking drivers call the function,
1331 * regardless of taking lock or not.
1332 *
1333 * When scsi can't dispatch I/Os anymore and needs to kill I/Os
1334 * (e.g. !sdev), scsi needs to return 'not busy'.
1335 * Otherwise, request stacking drivers may hold requests forever.
1336 */
1337static int scsi_lld_busy(struct request_queue *q)
1338{
1339        struct scsi_device *sdev = q->queuedata;
1340        struct Scsi_Host *shost;
1341        struct scsi_target *starget;
1342
1343        if (!sdev)
1344                return 0;
1345
1346        shost = sdev->host;
1347        starget = scsi_target(sdev);
1348
1349        if (scsi_host_in_recovery(shost) || scsi_host_is_busy(shost) ||
1350            scsi_target_is_busy(starget) || scsi_device_is_busy(sdev))
1351                return 1;
1352
1353        return 0;
1354}
1355
1356/*
1357 * Kill a request for a dead device
1358 */
1359static void scsi_kill_request(struct request *req, struct request_queue *q)
1360{
1361        struct scsi_cmnd *cmd = req->special;
1362        struct scsi_device *sdev = cmd->device;
1363        struct scsi_target *starget = scsi_target(sdev);
1364        struct Scsi_Host *shost = sdev->host;
1365
1366        blk_start_request(req);
1367
1368        if (unlikely(cmd == NULL)) {
1369                printk(KERN_CRIT "impossible request in %s.\n",
1370                                 __func__);
1371                BUG();
1372        }
1373
1374        scsi_init_cmd_errh(cmd);
1375        cmd->result = DID_NO_CONNECT << 16;
1376        atomic_inc(&cmd->device->iorequest_cnt);
1377
1378        /*
1379         * SCSI request completion path will do scsi_device_unbusy(),
1380         * bump busy counts.  To bump the counters, we need to dance
1381         * with the locks as normal issue path does.
1382         */
1383        sdev->device_busy++;
1384        spin_unlock(sdev->request_queue->queue_lock);
1385        spin_lock(shost->host_lock);
1386        shost->host_busy++;
1387        starget->target_busy++;
1388        spin_unlock(shost->host_lock);
1389        spin_lock(sdev->request_queue->queue_lock);
1390
1391        blk_complete_request(req);
1392}
1393
1394static void scsi_softirq_done(struct request *rq)
1395{
1396        struct scsi_cmnd *cmd = rq->special;
1397        unsigned long wait_for = (cmd->allowed + 1) * rq->timeout;
1398        int disposition;
1399
1400        INIT_LIST_HEAD(&cmd->eh_entry);
1401
1402        /*
1403         * Set the serial numbers back to zero
1404         */
1405        cmd->serial_number = 0;
1406
1407        atomic_inc(&cmd->device->iodone_cnt);
1408        if (cmd->result)
1409                atomic_inc(&cmd->device->ioerr_cnt);
1410
1411        disposition = scsi_decide_disposition(cmd);
1412        if (disposition != SUCCESS &&
1413            time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
1414                sdev_printk(KERN_ERR, cmd->device,
1415                            "timing out command, waited %lus\n",
1416                            wait_for/HZ);
1417                disposition = SUCCESS;
1418        }
1419                        
1420        scsi_log_completion(cmd, disposition);
1421
1422        switch (disposition) {
1423                case SUCCESS:
1424                        scsi_finish_command(cmd);
1425                        break;
1426                case NEEDS_RETRY:
1427                        scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY);
1428                        break;
1429                case ADD_TO_MLQUEUE:
1430                        scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
1431                        break;
1432                default:
1433                        if (!scsi_eh_scmd_add(cmd, 0))
1434                                scsi_finish_command(cmd);
1435        }
1436}
1437
1438/*
1439 * Function:    scsi_request_fn()
1440 *
1441 * Purpose:     Main strategy routine for SCSI.
1442 *
1443 * Arguments:   q       - Pointer to actual queue.
1444 *
1445 * Returns:     Nothing
1446 *
1447 * Lock status: IO request lock assumed to be held when called.
1448 */
1449static void scsi_request_fn(struct request_queue *q)
1450{
1451        struct scsi_device *sdev = q->queuedata;
1452        struct Scsi_Host *shost;
1453        struct scsi_cmnd *cmd;
1454        struct request *req;
1455
1456        if (!sdev) {
1457                printk("scsi: killing requests for dead queue\n");
1458                while ((req = blk_peek_request(q)) != NULL)
1459                        scsi_kill_request(req, q);
1460                return;
1461        }
1462
1463        if(!get_device(&sdev->sdev_gendev))
1464                /* We must be tearing the block queue down already */
1465                return;
1466
1467        /*
1468         * To start with, we keep looping until the queue is empty, or until
1469         * the host is no longer able to accept any more requests.
1470         */
1471        shost = sdev->host;
1472        while (!blk_queue_plugged(q)) {
1473                int rtn;
1474                /*
1475                 * get next queueable request.  We do this early to make sure
1476                 * that the request is fully prepared even if we cannot 
1477                 * accept it.
1478                 */
1479                req = blk_peek_request(q);
1480                if (!req || !scsi_dev_queue_ready(q, sdev))
1481                        break;
1482
1483                if (unlikely(!scsi_device_online(sdev))) {
1484                        sdev_printk(KERN_ERR, sdev,
1485                                    "rejecting I/O to offline device\n");
1486                        scsi_kill_request(req, q);
1487                        continue;
1488                }
1489
1490
1491                /*
1492                 * Remove the request from the request list.
1493                 */
1494                if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1495                        blk_start_request(req);
1496                sdev->device_busy++;
1497
1498                spin_unlock(q->queue_lock);
1499                cmd = req->special;
1500                if (unlikely(cmd == NULL)) {
1501                        printk(KERN_CRIT "impossible request in %s.\n"
1502                                         "please mail a stack trace to "
1503                                         "linux-scsi@vger.kernel.org\n",
1504                                         __func__);
1505                        blk_dump_rq_flags(req, "foo");
1506                        BUG();
1507                }
1508                spin_lock(shost->host_lock);
1509
1510                /*
1511                 * We hit this when the driver is using a host wide
1512                 * tag map. For device level tag maps the queue_depth check
1513                 * in the device ready fn would prevent us from trying
1514                 * to allocate a tag. Since the map is a shared host resource
1515                 * we add the dev to the starved list so it eventually gets
1516                 * a run when a tag is freed.
1517                 */
1518                if (blk_queue_tagged(q) && !blk_rq_tagged(req)) {
1519                        if (list_empty(&sdev->starved_entry))
1520                                list_add_tail(&sdev->starved_entry,
1521                                              &shost->starved_list);
1522                        goto not_ready;
1523                }
1524
1525                if (!scsi_target_queue_ready(shost, sdev))
1526                        goto not_ready;
1527
1528                if (!scsi_host_queue_ready(q, shost, sdev))
1529                        goto not_ready;
1530
1531                scsi_target(sdev)->target_busy++;
1532                shost->host_busy++;
1533
1534                /*
1535                 * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1536                 *              take the lock again.
1537                 */
1538                spin_unlock_irq(shost->host_lock);
1539
1540                /*
1541                 * Finally, initialize any error handling parameters, and set up
1542                 * the timers for timeouts.
1543                 */
1544                scsi_init_cmd_errh(cmd);
1545
1546                /*
1547                 * Dispatch the command to the low-level driver.
1548                 */
1549                rtn = scsi_dispatch_cmd(cmd);
1550                spin_lock_irq(q->queue_lock);
1551                if(rtn) {
1552                        /* we're refusing the command; because of
1553                         * the way locks get dropped, we need to 
1554                         * check here if plugging is required */
1555                        if(sdev->device_busy == 0)
1556                                blk_plug_device(q);
1557
1558                        break;
1559                }
1560        }
1561
1562        goto out;
1563
1564 not_ready:
1565        spin_unlock_irq(shost->host_lock);
1566
1567        /*
1568         * lock q, handle tag, requeue req, and decrement device_busy. We
1569         * must return with queue_lock held.
1570         *
1571         * Decrementing device_busy without checking it is OK, as all such
1572         * cases (host limits or settings) should run the queue at some
1573         * later time.
1574         */
1575        spin_lock_irq(q->queue_lock);
1576        blk_requeue_request(q, req);
1577        sdev->device_busy--;
1578        if(sdev->device_busy == 0)
1579                blk_plug_device(q);
1580 out:
1581        /* must be careful here...if we trigger the ->remove() function
1582         * we cannot be holding the q lock */
1583        spin_unlock_irq(q->queue_lock);
1584        put_device(&sdev->sdev_gendev);
1585        spin_lock_irq(q->queue_lock);
1586}
1587
1588u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1589{
1590        struct device *host_dev;
1591        u64 bounce_limit = 0xffffffff;
1592
1593        if (shost->unchecked_isa_dma)
1594                return BLK_BOUNCE_ISA;
1595        /*
1596         * Platforms with virtual-DMA translation
1597         * hardware have no practical limit.
1598         */
1599        if (!PCI_DMA_BUS_IS_PHYS)
1600                return BLK_BOUNCE_ANY;
1601
1602        host_dev = scsi_get_device(shost);
1603        if (host_dev && host_dev->dma_mask)
1604                bounce_limit = *host_dev->dma_mask;
1605
1606        return bounce_limit;
1607}
1608EXPORT_SYMBOL(scsi_calculate_bounce_limit);
1609
1610struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
1611                                         request_fn_proc *request_fn)
1612{
1613        struct request_queue *q;
1614        struct device *dev = shost->shost_gendev.parent;
1615
1616        q = blk_init_queue(request_fn, NULL);
1617        if (!q)
1618                return NULL;
1619
1620        /*
1621         * this limit is imposed by hardware restrictions
1622         */
1623        blk_queue_max_hw_segments(q, shost->sg_tablesize);
1624        blk_queue_max_phys_segments(q, SCSI_MAX_SG_CHAIN_SEGMENTS);
1625
1626        blk_queue_max_sectors(q, shost->max_sectors);
1627        blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1628        blk_queue_segment_boundary(q, shost->dma_boundary);
1629        dma_set_seg_boundary(dev, shost->dma_boundary);
1630
1631        blk_queue_max_segment_size(q, dma_get_max_seg_size(dev));
1632
1633        /* New queue, no concurrency on queue_flags */
1634        if (!shost->use_clustering)
1635                queue_flag_clear_unlocked(QUEUE_FLAG_CLUSTER, q);
1636
1637        /*
1638         * set a reasonable default alignment on word boundaries: the
1639         * host and device may alter it using
1640         * blk_queue_update_dma_alignment() later.
1641         */
1642        blk_queue_dma_alignment(q, 0x03);
1643
1644        return q;
1645}
1646EXPORT_SYMBOL(__scsi_alloc_queue);
1647
1648struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1649{
1650        struct request_queue *q;
1651
1652        q = __scsi_alloc_queue(sdev->host, scsi_request_fn);
1653        if (!q)
1654                return NULL;
1655
1656        blk_queue_prep_rq(q, scsi_prep_fn);
1657        blk_queue_softirq_done(q, scsi_softirq_done);
1658        blk_queue_rq_timed_out(q, scsi_times_out);
1659        blk_queue_lld_busy(q, scsi_lld_busy);
1660        return q;
1661}
1662
1663void scsi_free_queue(struct request_queue *q)
1664{
1665        blk_cleanup_queue(q);
1666}
1667
1668/*
1669 * Function:    scsi_block_requests()
1670 *
1671 * Purpose:     Utility function used by low-level drivers to prevent further
1672 *              commands from being queued to the device.
1673 *
1674 * Arguments:   shost       - Host in question
1675 *
1676 * Returns:     Nothing
1677 *
1678 * Lock status: No locks are assumed held.
1679 *
1680 * Notes:       There is no timer nor any other means by which the requests
1681 *              get unblocked other than the low-level driver calling
1682 *              scsi_unblock_requests().
1683 */
1684void scsi_block_requests(struct Scsi_Host *shost)
1685{
1686        shost->host_self_blocked = 1;
1687}
1688EXPORT_SYMBOL(scsi_block_requests);
1689
1690/*
1691 * Function:    scsi_unblock_requests()
1692 *
1693 * Purpose:     Utility function used by low-level drivers to allow further
1694 *              commands from being queued to the device.
1695 *
1696 * Arguments:   shost       - Host in question
1697 *
1698 * Returns:     Nothing
1699 *
1700 * Lock status: No locks are assumed held.
1701 *
1702 * Notes:       There is no timer nor any other means by which the requests
1703 *              get unblocked other than the low-level driver calling
1704 *              scsi_unblock_requests().
1705 *
1706 *              This is done as an API function so that changes to the
1707 *              internals of the scsi mid-layer won't require wholesale
1708 *              changes to drivers that use this feature.
1709 */
1710void scsi_unblock_requests(struct Scsi_Host *shost)
1711{
1712        shost->host_self_blocked = 0;
1713        scsi_run_host_queues(shost);
1714}
1715EXPORT_SYMBOL(scsi_unblock_requests);
1716
1717int __init scsi_init_queue(void)
1718{
1719        int i;
1720
1721        scsi_sdb_cache = kmem_cache_create("scsi_data_buffer",
1722                                           sizeof(struct scsi_data_buffer),
1723                                           0, 0, NULL);
1724        if (!scsi_sdb_cache) {
1725                printk(KERN_ERR "SCSI: can't init scsi sdb cache\n");
1726                return -ENOMEM;
1727        }
1728
1729        for (i = 0; i < SG_MEMPOOL_NR; i++) {
1730                struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1731                int size = sgp->size * sizeof(struct scatterlist);
1732
1733                sgp->slab = kmem_cache_create(sgp->name, size, 0,
1734                                SLAB_HWCACHE_ALIGN, NULL);
1735                if (!sgp->slab) {
1736                        printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1737                                        sgp->name);
1738                        goto cleanup_sdb;
1739                }
1740
1741                sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
1742                                                     sgp->slab);
1743                if (!sgp->pool) {
1744                        printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1745                                        sgp->name);
1746                        goto cleanup_sdb;
1747                }
1748        }
1749
1750        return 0;
1751
1752cleanup_sdb:
1753        for (i = 0; i < SG_MEMPOOL_NR; i++) {
1754                struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1755                if (sgp->pool)
1756                        mempool_destroy(sgp->pool);
1757                if (sgp->slab)
1758                        kmem_cache_destroy(sgp->slab);
1759        }
1760        kmem_cache_destroy(scsi_sdb_cache);
1761
1762        return -ENOMEM;
1763}
1764
1765void scsi_exit_queue(void)
1766{
1767        int i;
1768
1769        kmem_cache_destroy(scsi_sdb_cache);
1770
1771        for (i = 0; i < SG_MEMPOOL_NR; i++) {
1772                struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1773                mempool_destroy(sgp->pool);
1774                kmem_cache_destroy(sgp->slab);
1775        }
1776}
1777
1778/**
1779 *      scsi_mode_select - issue a mode select
1780 *      @sdev:  SCSI device to be queried
1781 *      @pf:    Page format bit (1 == standard, 0 == vendor specific)
1782 *      @sp:    Save page bit (0 == don't save, 1 == save)
1783 *      @modepage: mode page being requested
1784 *      @buffer: request buffer (may not be smaller than eight bytes)
1785 *      @len:   length of request buffer.
1786 *      @timeout: command timeout
1787 *      @retries: number of retries before failing
1788 *      @data: returns a structure abstracting the mode header data
1789 *      @sshdr: place to put sense data (or NULL if no sense to be collected).
1790 *              must be SCSI_SENSE_BUFFERSIZE big.
1791 *
1792 *      Returns zero if successful; negative error number or scsi
1793 *      status on error
1794 *
1795 */
1796int
1797scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
1798                 unsigned char *buffer, int len, int timeout, int retries,
1799                 struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1800{
1801        unsigned char cmd[10];
1802        unsigned char *real_buffer;
1803        int ret;
1804
1805        memset(cmd, 0, sizeof(cmd));
1806        cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
1807
1808        if (sdev->use_10_for_ms) {
1809                if (len > 65535)
1810                        return -EINVAL;
1811                real_buffer = kmalloc(8 + len, GFP_KERNEL);
1812                if (!real_buffer)
1813                        return -ENOMEM;
1814                memcpy(real_buffer + 8, buffer, len);
1815                len += 8;
1816                real_buffer[0] = 0;
1817                real_buffer[1] = 0;
1818                real_buffer[2] = data->medium_type;
1819                real_buffer[3] = data->device_specific;
1820                real_buffer[4] = data->longlba ? 0x01 : 0;
1821                real_buffer[5] = 0;
1822                real_buffer[6] = data->block_descriptor_length >> 8;
1823                real_buffer[7] = data->block_descriptor_length;
1824
1825                cmd[0] = MODE_SELECT_10;
1826                cmd[7] = len >> 8;
1827                cmd[8] = len;
1828        } else {
1829                if (len > 255 || data->block_descriptor_length > 255 ||
1830                    data->longlba)
1831                        return -EINVAL;
1832
1833                real_buffer = kmalloc(4 + len, GFP_KERNEL);
1834                if (!real_buffer)
1835                        return -ENOMEM;
1836                memcpy(real_buffer + 4, buffer, len);
1837                len += 4;
1838                real_buffer[0] = 0;
1839                real_buffer[1] = data->medium_type;
1840                real_buffer[2] = data->device_specific;
1841                real_buffer[3] = data->block_descriptor_length;
1842                
1843
1844                cmd[0] = MODE_SELECT;
1845                cmd[4] = len;
1846        }
1847
1848        ret = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, real_buffer, len,
1849                               sshdr, timeout, retries, NULL);
1850        kfree(real_buffer);
1851        return ret;
1852}
1853EXPORT_SYMBOL_GPL(scsi_mode_select);
1854
1855/**
1856 *      scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
1857 *      @sdev:  SCSI device to be queried
1858 *      @dbd:   set if mode sense will allow block descriptors to be returned
1859 *      @modepage: mode page being requested
1860 *      @buffer: request buffer (may not be smaller than eight bytes)
1861 *      @len:   length of request buffer.
1862 *      @timeout: command timeout
1863 *      @retries: number of retries before failing
1864 *      @data: returns a structure abstracting the mode header data
1865 *      @sshdr: place to put sense data (or NULL if no sense to be collected).
1866 *              must be SCSI_SENSE_BUFFERSIZE big.
1867 *
1868 *      Returns zero if unsuccessful, or the header offset (either 4
1869 *      or 8 depending on whether a six or ten byte command was
1870 *      issued) if successful.
1871 */
1872int
1873scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
1874                  unsigned char *buffer, int len, int timeout, int retries,
1875                  struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1876{
1877        unsigned char cmd[12];
1878        int use_10_for_ms;
1879        int header_length;
1880        int result;
1881        struct scsi_sense_hdr my_sshdr;
1882
1883        memset(data, 0, sizeof(*data));
1884        memset(&cmd[0], 0, 12);
1885        cmd[1] = dbd & 0x18;    /* allows DBD and LLBA bits */
1886        cmd[2] = modepage;
1887
1888        /* caller might not be interested in sense, but we need it */
1889        if (!sshdr)
1890                sshdr = &my_sshdr;
1891
1892 retry:
1893        use_10_for_ms = sdev->use_10_for_ms;
1894
1895        if (use_10_for_ms) {
1896                if (len < 8)
1897                        len = 8;
1898
1899                cmd[0] = MODE_SENSE_10;
1900                cmd[8] = len;
1901                header_length = 8;
1902        } else {
1903                if (len < 4)
1904                        len = 4;
1905
1906                cmd[0] = MODE_SENSE;
1907                cmd[4] = len;
1908                header_length = 4;
1909        }
1910
1911        memset(buffer, 0, len);
1912
1913        result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
1914                                  sshdr, timeout, retries, NULL);
1915
1916        /* This code looks awful: what it's doing is making sure an
1917         * ILLEGAL REQUEST sense return identifies the actual command
1918         * byte as the problem.  MODE_SENSE commands can return
1919         * ILLEGAL REQUEST if the code page isn't supported */
1920
1921        if (use_10_for_ms && !scsi_status_is_good(result) &&
1922            (driver_byte(result) & DRIVER_SENSE)) {
1923                if (scsi_sense_valid(sshdr)) {
1924                        if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
1925                            (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
1926                                /* 
1927                                 * Invalid command operation code
1928                                 */
1929                                sdev->use_10_for_ms = 0;
1930                                goto retry;
1931                        }
1932                }
1933        }
1934
1935        if(scsi_status_is_good(result)) {
1936                if (unlikely(buffer[0] == 0x86 && buffer[1] == 0x0b &&
1937                             (modepage == 6 || modepage == 8))) {
1938                        /* Initio breakage? */
1939                        header_length = 0;
1940                        data->length = 13;
1941                        data->medium_type = 0;
1942                        data->device_specific = 0;
1943                        data->longlba = 0;
1944                        data->block_descriptor_length = 0;
1945                } else if(use_10_for_ms) {
1946                        data->length = buffer[0]*256 + buffer[1] + 2;
1947                        data->medium_type = buffer[2];
1948                        data->device_specific = buffer[3];
1949                        data->longlba = buffer[4] & 0x01;
1950                        data->block_descriptor_length = buffer[6]*256
1951                                + buffer[7];
1952                } else {
1953                        data->length = buffer[0] + 1;
1954                        data->medium_type = buffer[1];
1955                        data->device_specific = buffer[2];
1956                        data->block_descriptor_length = buffer[3];
1957                }
1958                data->header_length = header_length;
1959        }
1960
1961        return result;
1962}
1963EXPORT_SYMBOL(scsi_mode_sense);
1964
1965/**
1966 *      scsi_test_unit_ready - test if unit is ready
1967 *      @sdev:  scsi device to change the state of.
1968 *      @timeout: command timeout
1969 *      @retries: number of retries before failing
1970 *      @sshdr_external: Optional pointer to struct scsi_sense_hdr for
1971 *              returning sense. Make sure that this is cleared before passing
1972 *              in.
1973 *
1974 *      Returns zero if unsuccessful or an error if TUR failed.  For
1975 *      removable media, a return of NOT_READY or UNIT_ATTENTION is
1976 *      translated to success, with the ->changed flag updated.
1977 **/
1978int
1979scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries,
1980                     struct scsi_sense_hdr *sshdr_external)
1981{
1982        char cmd[] = {
1983                TEST_UNIT_READY, 0, 0, 0, 0, 0,
1984        };
1985        struct scsi_sense_hdr *sshdr;
1986        int result;
1987
1988        if (!sshdr_external)
1989                sshdr = kzalloc(sizeof(*sshdr), GFP_KERNEL);
1990        else
1991                sshdr = sshdr_external;
1992
1993        /* try to eat the UNIT_ATTENTION if there are enough retries */
1994        do {
1995                result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
1996                                          timeout, retries, NULL);
1997                if (sdev->removable && scsi_sense_valid(sshdr) &&
1998                    sshdr->sense_key == UNIT_ATTENTION)
1999                        sdev->changed = 1;
2000        } while (scsi_sense_valid(sshdr) &&
2001                 sshdr->sense_key == UNIT_ATTENTION && --retries);
2002
2003        if (!sshdr)
2004                /* could not allocate sense buffer, so can't process it */
2005                return result;
2006
2007        if (sdev->removable && scsi_sense_valid(sshdr) &&
2008            (sshdr->sense_key == UNIT_ATTENTION ||
2009             sshdr->sense_key == NOT_READY)) {
2010                sdev->changed = 1;
2011                result = 0;
2012        }
2013        if (!sshdr_external)
2014                kfree(sshdr);
2015        return result;
2016}
2017EXPORT_SYMBOL(scsi_test_unit_ready);
2018
2019/**
2020 *      scsi_device_set_state - Take the given device through the device state model.
2021 *      @sdev:  scsi device to change the state of.
2022 *      @state: state to change to.
2023 *
2024 *      Returns zero if unsuccessful or an error if the requested 
2025 *      transition is illegal.
2026 */
2027int
2028scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
2029{
2030        enum scsi_device_state oldstate = sdev->sdev_state;
2031
2032        if (state == oldstate)
2033                return 0;
2034
2035        switch (state) {
2036        case SDEV_CREATED:
2037                switch (oldstate) {
2038                case SDEV_CREATED_BLOCK:
2039                        break;
2040                default:
2041                        goto illegal;
2042                }
2043                break;
2044                        
2045        case SDEV_RUNNING:
2046                switch (oldstate) {
2047                case SDEV_CREATED:
2048                case SDEV_OFFLINE:
2049                case SDEV_QUIESCE:
2050                case SDEV_BLOCK:
2051                        break;
2052                default:
2053                        goto illegal;
2054                }
2055                break;
2056
2057        case SDEV_QUIESCE:
2058                switch (oldstate) {
2059                case SDEV_RUNNING:
2060                case SDEV_OFFLINE:
2061                        break;
2062                default:
2063                        goto illegal;
2064                }
2065                break;
2066
2067        case SDEV_OFFLINE:
2068                switch (oldstate) {
2069                case SDEV_CREATED:
2070                case SDEV_RUNNING:
2071                case SDEV_QUIESCE:
2072                case SDEV_BLOCK:
2073                        break;
2074                default:
2075                        goto illegal;
2076                }
2077                break;
2078
2079        case SDEV_BLOCK:
2080                switch (oldstate) {
2081                case SDEV_RUNNING:
2082                case SDEV_CREATED_BLOCK:
2083                        break;
2084                default:
2085                        goto illegal;
2086                }
2087                break;
2088
2089        case SDEV_CREATED_BLOCK:
2090                switch (oldstate) {
2091                case SDEV_CREATED:
2092                        break;
2093                default:
2094                        goto illegal;
2095                }
2096                break;
2097
2098        case SDEV_CANCEL:
2099                switch (oldstate) {
2100                case SDEV_CREATED:
2101                case SDEV_RUNNING:
2102                case SDEV_QUIESCE:
2103                case SDEV_OFFLINE:
2104                case SDEV_BLOCK:
2105                        break;
2106                default:
2107                        goto illegal;
2108                }
2109                break;
2110
2111        case SDEV_DEL:
2112                switch (oldstate) {
2113                case SDEV_CREATED:
2114                case SDEV_RUNNING:
2115                case SDEV_OFFLINE:
2116                case SDEV_CANCEL:
2117                        break;
2118                default:
2119                        goto illegal;
2120                }
2121                break;
2122
2123        }
2124        sdev->sdev_state = state;
2125        return 0;
2126
2127 illegal:
2128        SCSI_LOG_ERROR_RECOVERY(1, 
2129                                sdev_printk(KERN_ERR, sdev,
2130                                            "Illegal state transition %s->%s\n",
2131                                            scsi_device_state_name(oldstate),
2132                                            scsi_device_state_name(state))
2133                                );
2134        return -EINVAL;
2135}
2136EXPORT_SYMBOL(scsi_device_set_state);
2137
2138/**
2139 *      sdev_evt_emit - emit a single SCSI device uevent
2140 *      @sdev: associated SCSI device
2141 *      @evt: event to emit
2142 *
2143 *      Send a single uevent (scsi_event) to the associated scsi_device.
2144 */
2145static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
2146{
2147        int idx = 0;
2148        char *envp[3];
2149
2150        switch (evt->evt_type) {
2151        case SDEV_EVT_MEDIA_CHANGE:
2152                envp[idx++] = "SDEV_MEDIA_CHANGE=1";
2153                break;
2154
2155        default:
2156                /* do nothing */
2157                break;
2158        }
2159
2160        envp[idx++] = NULL;
2161
2162        kobject_uevent_env(&sdev->sdev_gendev.kobj, KOBJ_CHANGE, envp);
2163}
2164
2165/**
2166 *      sdev_evt_thread - send a uevent for each scsi event
2167 *      @work: work struct for scsi_device
2168 *
2169 *      Dispatch queued events to their associated scsi_device kobjects
2170 *      as uevents.
2171 */
2172void scsi_evt_thread(struct work_struct *work)
2173{
2174        struct scsi_device *sdev;
2175        LIST_HEAD(event_list);
2176
2177        sdev = container_of(work, struct scsi_device, event_work);
2178
2179        while (1) {
2180                struct scsi_event *evt;
2181                struct list_head *this, *tmp;
2182                unsigned long flags;
2183
2184                spin_lock_irqsave(&sdev->list_lock, flags);
2185                list_splice_init(&sdev->event_list, &event_list);
2186                spin_unlock_irqrestore(&sdev->list_lock, flags);
2187
2188                if (list_empty(&event_list))
2189                        break;
2190
2191                list_for_each_safe(this, tmp, &event_list) {
2192                        evt = list_entry(this, struct scsi_event, node);
2193                        list_del(&evt->node);
2194                        scsi_evt_emit(sdev, evt);
2195                        kfree(evt);
2196                }
2197        }
2198}
2199
2200/**
2201 *      sdev_evt_send - send asserted event to uevent thread
2202 *      @sdev: scsi_device event occurred on
2203 *      @evt: event to send
2204 *
2205 *      Assert scsi device event asynchronously.
2206 */
2207void sdev_evt_send(struct scsi_device *sdev, struct scsi_event *evt)
2208{
2209        unsigned long flags;
2210
2211#if 0
2212        /* FIXME: currently this check eliminates all media change events
2213         * for polled devices.  Need to update to discriminate between AN
2214         * and polled events */
2215        if (!test_bit(evt->evt_type, sdev->supported_events)) {
2216                kfree(evt);
2217                return;
2218        }
2219#endif
2220
2221        spin_lock_irqsave(&sdev->list_lock, flags);
2222        list_add_tail(&evt->node, &sdev->event_list);
2223        schedule_work(&sdev->event_work);
2224        spin_unlock_irqrestore(&sdev->list_lock, flags);
2225}
2226EXPORT_SYMBOL_GPL(sdev_evt_send);
2227
2228/**
2229 *      sdev_evt_alloc - allocate a new scsi event
2230 *      @evt_type: type of event to allocate
2231 *      @gfpflags: GFP flags for allocation
2232 *
2233 *      Allocates and returns a new scsi_event.
2234 */
2235struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
2236                                  gfp_t gfpflags)
2237{
2238        struct scsi_event *evt = kzalloc(sizeof(struct scsi_event), gfpflags);
2239        if (!evt)
2240                return NULL;
2241
2242        evt->evt_type = evt_type;
2243        INIT_LIST_HEAD(&evt->node);
2244
2245        /* evt_type-specific initialization, if any */
2246        switch (evt_type) {
2247        case SDEV_EVT_MEDIA_CHANGE:
2248        default:
2249                /* do nothing */
2250                break;
2251        }
2252
2253        return evt;
2254}
2255EXPORT_SYMBOL_GPL(sdev_evt_alloc);
2256
2257/**
2258 *      sdev_evt_send_simple - send asserted event to uevent thread
2259 *      @sdev: scsi_device event occurred on
2260 *      @evt_type: type of event to send
2261 *      @gfpflags: GFP flags for allocation
2262 *
2263 *      Assert scsi device event asynchronously, given an event type.
2264 */
2265void sdev_evt_send_simple(struct scsi_device *sdev,
2266                          enum scsi_device_event evt_type, gfp_t gfpflags)
2267{
2268        struct scsi_event *evt = sdev_evt_alloc(evt_type, gfpflags);
2269        if (!evt) {
2270                sdev_printk(KERN_ERR, sdev, "event %d eaten due to OOM\n",
2271                            evt_type);
2272                return;
2273        }
2274
2275        sdev_evt_send(sdev, evt);
2276}
2277EXPORT_SYMBOL_GPL(sdev_evt_send_simple);
2278
2279/**
2280 *      scsi_device_quiesce - Block user issued commands.
2281 *      @sdev:  scsi device to quiesce.
2282 *
2283 *      This works by trying to transition to the SDEV_QUIESCE state
2284 *      (which must be a legal transition).  When the device is in this
2285 *      state, only special requests will be accepted, all others will
2286 *      be deferred.  Since special requests may also be requeued requests,
2287 *      a successful return doesn't guarantee the device will be 
2288 *      totally quiescent.
2289 *
2290 *      Must be called with user context, may sleep.
2291 *
2292 *      Returns zero if unsuccessful or an error if not.
2293 */
2294int
2295scsi_device_quiesce(struct scsi_device *sdev)
2296{
2297        int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
2298        if (err)
2299                return err;
2300
2301        scsi_run_queue(sdev->request_queue);
2302        while (sdev->device_busy) {
2303                msleep_interruptible(200);
2304                scsi_run_queue(sdev->request_queue);
2305        }
2306        return 0;
2307}
2308EXPORT_SYMBOL(scsi_device_quiesce);
2309
2310/**
2311 *      scsi_device_resume - Restart user issued commands to a quiesced device.
2312 *      @sdev:  scsi device to resume.
2313 *
2314 *      Moves the device from quiesced back to running and restarts the
2315 *      queues.
2316 *
2317 *      Must be called with user context, may sleep.
2318 */
2319void
2320scsi_device_resume(struct scsi_device *sdev)
2321{
2322        if(scsi_device_set_state(sdev, SDEV_RUNNING))
2323                return;
2324        scsi_run_queue(sdev->request_queue);
2325}
2326EXPORT_SYMBOL(scsi_device_resume);
2327
2328static void
2329device_quiesce_fn(struct scsi_device *sdev, void *data)
2330{
2331        scsi_device_quiesce(sdev);
2332}
2333
2334void
2335scsi_target_quiesce(struct scsi_target *starget)
2336{
2337        starget_for_each_device(starget, NULL, device_quiesce_fn);
2338}
2339EXPORT_SYMBOL(scsi_target_quiesce);
2340
2341static void
2342device_resume_fn(struct scsi_device *sdev, void *data)
2343{
2344        scsi_device_resume(sdev);
2345}
2346
2347void
2348scsi_target_resume(struct scsi_target *starget)
2349{
2350        starget_for_each_device(starget, NULL, device_resume_fn);
2351}
2352EXPORT_SYMBOL(scsi_target_resume);
2353
2354/**
2355 * scsi_internal_device_block - internal function to put a device temporarily into the SDEV_BLOCK state
2356 * @sdev:       device to block
2357 *
2358 * Block request made by scsi lld's to temporarily stop all
2359 * scsi commands on the specified device.  Called from interrupt
2360 * or normal process context.
2361 *
2362 * Returns zero if successful or error if not
2363 *
2364 * Notes:       
2365 *      This routine transitions the device to the SDEV_BLOCK state
2366 *      (which must be a legal transition).  When the device is in this
2367 *      state, all commands are deferred until the scsi lld reenables
2368 *      the device with scsi_device_unblock or device_block_tmo fires.
2369 *      This routine assumes the host_lock is held on entry.
2370 */
2371int
2372scsi_internal_device_block(struct scsi_device *sdev)
2373{
2374        struct request_queue *q = sdev->request_queue;
2375        unsigned long flags;
2376        int err = 0;
2377
2378        err = scsi_device_set_state(sdev, SDEV_BLOCK);
2379        if (err) {
2380                err = scsi_device_set_state(sdev, SDEV_CREATED_BLOCK);
2381
2382                if (err)
2383                        return err;
2384        }
2385
2386        /* 
2387         * The device has transitioned to SDEV_BLOCK.  Stop the
2388         * block layer from calling the midlayer with this device's
2389         * request queue. 
2390         */
2391        spin_lock_irqsave(q->queue_lock, flags);
2392        blk_stop_queue(q);
2393        spin_unlock_irqrestore(q->queue_lock, flags);
2394
2395        return 0;
2396}
2397EXPORT_SYMBOL_GPL(scsi_internal_device_block);
2398 
2399/**
2400 * scsi_internal_device_unblock - resume a device after a block request
2401 * @sdev:       device to resume
2402 *
2403 * Called by scsi lld's or the midlayer to restart the device queue
2404 * for the previously suspended scsi device.  Called from interrupt or
2405 * normal process context.
2406 *
2407 * Returns zero if successful or error if not.
2408 *
2409 * Notes:       
2410 *      This routine transitions the device to the SDEV_RUNNING state
2411 *      (which must be a legal transition) allowing the midlayer to
2412 *      goose the queue for this device.  This routine assumes the 
2413 *      host_lock is held upon entry.
2414 */
2415int
2416scsi_internal_device_unblock(struct scsi_device *sdev)
2417{
2418        struct request_queue *q = sdev->request_queue; 
2419        unsigned long flags;
2420        
2421        /* 
2422         * Try to transition the scsi device to SDEV_RUNNING
2423         * and goose the device queue if successful.  
2424         */
2425        if (sdev->sdev_state == SDEV_BLOCK)
2426                sdev->sdev_state = SDEV_RUNNING;
2427        else if (sdev->sdev_state == SDEV_CREATED_BLOCK)
2428                sdev->sdev_state = SDEV_CREATED;
2429        else
2430                return -EINVAL;
2431
2432        spin_lock_irqsave(q->queue_lock, flags);
2433        blk_start_queue(q);
2434        spin_unlock_irqrestore(q->queue_lock, flags);
2435
2436        return 0;
2437}
2438EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
2439
2440static void
2441device_block(struct scsi_device *sdev, void *data)
2442{
2443        scsi_internal_device_block(sdev);
2444}
2445
2446static int
2447target_block(struct device *dev, void *data)
2448{
2449        if (scsi_is_target_device(dev))
2450                starget_for_each_device(to_scsi_target(dev), NULL,
2451                                        device_block);
2452        return 0;
2453}
2454
2455void
2456scsi_target_block(struct device *dev)
2457{
2458        if (scsi_is_target_device(dev))
2459                starget_for_each_device(to_scsi_target(dev), NULL,
2460                                        device_block);
2461        else
2462                device_for_each_child(dev, NULL, target_block);
2463}
2464EXPORT_SYMBOL_GPL(scsi_target_block);
2465
2466static void
2467device_unblock(struct scsi_device *sdev, void *data)
2468{
2469        scsi_internal_device_unblock(sdev);
2470}
2471
2472static int
2473target_unblock(struct device *dev, void *data)
2474{
2475        if (scsi_is_target_device(dev))
2476                starget_for_each_device(to_scsi_target(dev), NULL,
2477                                        device_unblock);
2478        return 0;
2479}
2480
2481void
2482scsi_target_unblock(struct device *dev)
2483{
2484        if (scsi_is_target_device(dev))
2485                starget_for_each_device(to_scsi_target(dev), NULL,
2486                                        device_unblock);
2487        else
2488                device_for_each_child(dev, NULL, target_unblock);
2489}
2490EXPORT_SYMBOL_GPL(scsi_target_unblock);
2491
2492/**
2493 * scsi_kmap_atomic_sg - find and atomically map an sg-elemnt
2494 * @sgl:        scatter-gather list
2495 * @sg_count:   number of segments in sg
2496 * @offset:     offset in bytes into sg, on return offset into the mapped area
2497 * @len:        bytes to map, on return number of bytes mapped
2498 *
2499 * Returns virtual address of the start of the mapped page
2500 */
2501void *scsi_kmap_atomic_sg(struct scatterlist *sgl, int sg_count,
2502                          size_t *offset, size_t *len)
2503{
2504        int i;
2505        size_t sg_len = 0, len_complete = 0;
2506        struct scatterlist *sg;
2507        struct page *page;
2508
2509        WARN_ON(!irqs_disabled());
2510
2511        for_each_sg(sgl, sg, sg_count, i) {
2512                len_complete = sg_len; /* Complete sg-entries */
2513                sg_len += sg->length;
2514                if (sg_len > *offset)
2515                        break;
2516        }
2517
2518        if (unlikely(i == sg_count)) {
2519                printk(KERN_ERR "%s: Bytes in sg: %zu, requested offset %zu, "
2520                        "elements %d\n",
2521                       __func__, sg_len, *offset, sg_count);
2522                WARN_ON(1);
2523                return NULL;
2524        }
2525
2526        /* Offset starting from the beginning of first page in this sg-entry */
2527        *offset = *offset - len_complete + sg->offset;
2528
2529        /* Assumption: contiguous pages can be accessed as "page + i" */
2530        page = nth_page(sg_page(sg), (*offset >> PAGE_SHIFT));
2531        *offset &= ~PAGE_MASK;
2532
2533        /* Bytes in this sg-entry from *offset to the end of the page */
2534        sg_len = PAGE_SIZE - *offset;
2535        if (*len > sg_len)
2536                *len = sg_len;
2537
2538        return kmap_atomic(page, KM_BIO_SRC_IRQ);
2539}
2540EXPORT_SYMBOL(scsi_kmap_atomic_sg);
2541
2542/**
2543 * scsi_kunmap_atomic_sg - atomically unmap a virtual address, previously mapped with scsi_kmap_atomic_sg
2544 * @virt:       virtual address to be unmapped
2545 */
2546void scsi_kunmap_atomic_sg(void *virt)
2547{
2548        kunmap_atomic(virt, KM_BIO_SRC_IRQ);
2549}
2550EXPORT_SYMBOL(scsi_kunmap_atomic_sg);
2551