Merge HEAD from ../scsi-misc-2.6-tmp
[sfrench/cifs-2.6.git] / drivers / scsi / scsi_lib.c
1 /*
2  *  scsi_lib.c Copyright (C) 1999 Eric Youngdale
3  *
4  *  SCSI queueing library.
5  *      Initial versions: Eric Youngdale (eric@andante.org).
6  *                        Based upon conversations with large numbers
7  *                        of people at Linux Expo.
8  */
9
10 #include <linux/bio.h>
11 #include <linux/blkdev.h>
12 #include <linux/completion.h>
13 #include <linux/kernel.h>
14 #include <linux/mempool.h>
15 #include <linux/slab.h>
16 #include <linux/init.h>
17 #include <linux/pci.h>
18 #include <linux/delay.h>
19
20 #include <scsi/scsi.h>
21 #include <scsi/scsi_dbg.h>
22 #include <scsi/scsi_device.h>
23 #include <scsi/scsi_driver.h>
24 #include <scsi/scsi_eh.h>
25 #include <scsi/scsi_host.h>
26 #include <scsi/scsi_request.h>
27
28 #include "scsi_priv.h"
29 #include "scsi_logging.h"
30
31
32 #define SG_MEMPOOL_NR           (sizeof(scsi_sg_pools)/sizeof(struct scsi_host_sg_pool))
33 #define SG_MEMPOOL_SIZE         32
34
35 struct scsi_host_sg_pool {
36         size_t          size;
37         char            *name; 
38         kmem_cache_t    *slab;
39         mempool_t       *pool;
40 };
41
42 #if (SCSI_MAX_PHYS_SEGMENTS < 32)
43 #error SCSI_MAX_PHYS_SEGMENTS is too small
44 #endif
45
46 #define SP(x) { x, "sgpool-" #x } 
47 static struct scsi_host_sg_pool scsi_sg_pools[] = {
48         SP(8),
49         SP(16),
50         SP(32),
51 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
52         SP(64),
53 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
54         SP(128),
55 #if (SCSI_MAX_PHYS_SEGMENTS > 128)
56         SP(256),
57 #if (SCSI_MAX_PHYS_SEGMENTS > 256)
58 #error SCSI_MAX_PHYS_SEGMENTS is too large
59 #endif
60 #endif
61 #endif
62 #endif
63 };      
64 #undef SP
65
66
67 /*
68  * Function:    scsi_insert_special_req()
69  *
70  * Purpose:     Insert pre-formed request into request queue.
71  *
72  * Arguments:   sreq    - request that is ready to be queued.
73  *              at_head - boolean.  True if we should insert at head
74  *                        of queue, false if we should insert at tail.
75  *
76  * Lock status: Assumed that lock is not held upon entry.
77  *
78  * Returns:     Nothing
79  *
80  * Notes:       This function is called from character device and from
81  *              ioctl types of functions where the caller knows exactly
82  *              what SCSI command needs to be issued.   The idea is that
83  *              we merely inject the command into the queue (at the head
84  *              for now), and then call the queue request function to actually
85  *              process it.
86  */
87 int scsi_insert_special_req(struct scsi_request *sreq, int at_head)
88 {
89         /*
90          * Because users of this function are apt to reuse requests with no
91          * modification, we have to sanitise the request flags here
92          */
93         sreq->sr_request->flags &= ~REQ_DONTPREP;
94         blk_insert_request(sreq->sr_device->request_queue, sreq->sr_request,
95                            at_head, sreq);
96         return 0;
97 }
98
99 static void scsi_run_queue(struct request_queue *q);
100
101 /*
102  * Function:    scsi_queue_insert()
103  *
104  * Purpose:     Insert a command in the midlevel queue.
105  *
106  * Arguments:   cmd    - command that we are adding to queue.
107  *              reason - why we are inserting command to queue.
108  *
109  * Lock status: Assumed that lock is not held upon entry.
110  *
111  * Returns:     Nothing.
112  *
113  * Notes:       We do this for one of two cases.  Either the host is busy
114  *              and it cannot accept any more commands for the time being,
115  *              or the device returned QUEUE_FULL and can accept no more
116  *              commands.
117  * Notes:       This could be called either from an interrupt context or a
118  *              normal process context.
119  */
120 int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
121 {
122         struct Scsi_Host *host = cmd->device->host;
123         struct scsi_device *device = cmd->device;
124         struct request_queue *q = device->request_queue;
125         unsigned long flags;
126
127         SCSI_LOG_MLQUEUE(1,
128                  printk("Inserting command %p into mlqueue\n", cmd));
129
130         /*
131          * Set the appropriate busy bit for the device/host.
132          *
133          * If the host/device isn't busy, assume that something actually
134          * completed, and that we should be able to queue a command now.
135          *
136          * Note that the prior mid-layer assumption that any host could
137          * always queue at least one command is now broken.  The mid-layer
138          * will implement a user specifiable stall (see
139          * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
140          * if a command is requeued with no other commands outstanding
141          * either for the device or for the host.
142          */
143         if (reason == SCSI_MLQUEUE_HOST_BUSY)
144                 host->host_blocked = host->max_host_blocked;
145         else if (reason == SCSI_MLQUEUE_DEVICE_BUSY)
146                 device->device_blocked = device->max_device_blocked;
147
148         /*
149          * Decrement the counters, since these commands are no longer
150          * active on the host/device.
151          */
152         scsi_device_unbusy(device);
153
154         /*
155          * Requeue this command.  It will go before all other commands
156          * that are already in the queue.
157          *
158          * NOTE: there is magic here about the way the queue is plugged if
159          * we have no outstanding commands.
160          * 
161          * Although we *don't* plug the queue, we call the request
162          * function.  The SCSI request function detects the blocked condition
163          * and plugs the queue appropriately.
164          */
165         spin_lock_irqsave(q->queue_lock, flags);
166         blk_requeue_request(q, cmd->request);
167         spin_unlock_irqrestore(q->queue_lock, flags);
168
169         scsi_run_queue(q);
170
171         return 0;
172 }
173
174 /*
175  * Function:    scsi_do_req
176  *
177  * Purpose:     Queue a SCSI request
178  *
179  * Arguments:   sreq      - command descriptor.
180  *              cmnd      - actual SCSI command to be performed.
181  *              buffer    - data buffer.
182  *              bufflen   - size of data buffer.
183  *              done      - completion function to be run.
184  *              timeout   - how long to let it run before timeout.
185  *              retries   - number of retries we allow.
186  *
187  * Lock status: No locks held upon entry.
188  *
189  * Returns:     Nothing.
190  *
191  * Notes:       This function is only used for queueing requests for things
192  *              like ioctls and character device requests - this is because
193  *              we essentially just inject a request into the queue for the
194  *              device.
195  *
196  *              In order to support the scsi_device_quiesce function, we
197  *              now inject requests on the *head* of the device queue
198  *              rather than the tail.
199  */
200 void scsi_do_req(struct scsi_request *sreq, const void *cmnd,
201                  void *buffer, unsigned bufflen,
202                  void (*done)(struct scsi_cmnd *),
203                  int timeout, int retries)
204 {
205         /*
206          * If the upper level driver is reusing these things, then
207          * we should release the low-level block now.  Another one will
208          * be allocated later when this request is getting queued.
209          */
210         __scsi_release_request(sreq);
211
212         /*
213          * Our own function scsi_done (which marks the host as not busy,
214          * disables the timeout counter, etc) will be called by us or by the
215          * scsi_hosts[host].queuecommand() function needs to also call
216          * the completion function for the high level driver.
217          */
218         memcpy(sreq->sr_cmnd, cmnd, sizeof(sreq->sr_cmnd));
219         sreq->sr_bufflen = bufflen;
220         sreq->sr_buffer = buffer;
221         sreq->sr_allowed = retries;
222         sreq->sr_done = done;
223         sreq->sr_timeout_per_command = timeout;
224
225         if (sreq->sr_cmd_len == 0)
226                 sreq->sr_cmd_len = COMMAND_SIZE(sreq->sr_cmnd[0]);
227
228         /*
229          * head injection *required* here otherwise quiesce won't work
230          */
231         scsi_insert_special_req(sreq, 1);
232 }
233 EXPORT_SYMBOL(scsi_do_req);
234
235 /* This is the end routine we get to if a command was never attached
236  * to the request.  Simply complete the request without changing
237  * rq_status; this will cause a DRIVER_ERROR. */
238 static void scsi_wait_req_end_io(struct request *req)
239 {
240         BUG_ON(!req->waiting);
241
242         complete(req->waiting);
243 }
244
245 void scsi_wait_req(struct scsi_request *sreq, const void *cmnd, void *buffer,
246                    unsigned bufflen, int timeout, int retries)
247 {
248         DECLARE_COMPLETION(wait);
249         int write = (sreq->sr_data_direction == DMA_TO_DEVICE);
250         struct request *req;
251
252         req = blk_get_request(sreq->sr_device->request_queue, write,
253                               __GFP_WAIT);
254         if (bufflen && blk_rq_map_kern(sreq->sr_device->request_queue, req,
255                                        buffer, bufflen, __GFP_WAIT)) {
256                 sreq->sr_result = DRIVER_ERROR << 24;
257                 blk_put_request(req);
258                 return;
259         }
260
261         req->flags |= REQ_NOMERGE;
262         req->waiting = &wait;
263         req->end_io = scsi_wait_req_end_io;
264         req->cmd_len = COMMAND_SIZE(((u8 *)cmnd)[0]);
265         req->sense = sreq->sr_sense_buffer;
266         req->sense_len = 0;
267         memcpy(req->cmd, cmnd, req->cmd_len);
268         req->timeout = timeout;
269         req->flags |= REQ_BLOCK_PC;
270         req->rq_disk = NULL;
271         blk_insert_request(sreq->sr_device->request_queue, req,
272                            sreq->sr_data_direction == DMA_TO_DEVICE, NULL);
273         wait_for_completion(&wait);
274         sreq->sr_request->waiting = NULL;
275         sreq->sr_result = req->errors;
276         if (req->errors)
277                 sreq->sr_result |= (DRIVER_ERROR << 24);
278
279         blk_put_request(req);
280 }
281
282 EXPORT_SYMBOL(scsi_wait_req);
283
284 /**
285  * scsi_execute_req - insert request and wait for the result
286  * @sdev:       scsi device
287  * @cmd:        scsi command
288  * @data_direction: data direction
289  * @buffer:     data buffer
290  * @bufflen:    len of buffer
291  * @sense:      optional sense buffer
292  * @timeout:    request timeout in seconds
293  * @retries:    number of times to retry request
294  *
295  * scsi_execute_req returns the req->errors value which is the
296  * the scsi_cmnd result field.
297  **/
298 int scsi_execute_req(struct scsi_device *sdev, unsigned char *cmd,
299                      int data_direction, void *buffer, unsigned bufflen,
300                      unsigned char *sense, int timeout, int retries)
301 {
302         struct request *req;
303         int write = (data_direction == DMA_TO_DEVICE);
304         int ret = DRIVER_ERROR << 24;
305
306         req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
307
308         if (bufflen &&  blk_rq_map_kern(sdev->request_queue, req,
309                                         buffer, bufflen, __GFP_WAIT))
310                 goto out;
311
312         req->cmd_len = COMMAND_SIZE(cmd[0]);
313         memcpy(req->cmd, cmd, req->cmd_len);
314         req->sense = sense;
315         req->sense_len = 0;
316         req->timeout = timeout;
317         req->flags |= REQ_BLOCK_PC | REQ_SPECIAL;
318
319         /*
320          * head injection *required* here otherwise quiesce won't work
321          */
322         blk_execute_rq(req->q, NULL, req, 1);
323
324         ret = req->errors;
325  out:
326         blk_put_request(req);
327
328         return ret;
329 }
330
331 EXPORT_SYMBOL(scsi_execute_req);
332
333 /*
334  * Function:    scsi_init_cmd_errh()
335  *
336  * Purpose:     Initialize cmd fields related to error handling.
337  *
338  * Arguments:   cmd     - command that is ready to be queued.
339  *
340  * Returns:     Nothing
341  *
342  * Notes:       This function has the job of initializing a number of
343  *              fields related to error handling.   Typically this will
344  *              be called once for each command, as required.
345  */
346 static int scsi_init_cmd_errh(struct scsi_cmnd *cmd)
347 {
348         cmd->serial_number = 0;
349
350         memset(cmd->sense_buffer, 0, sizeof cmd->sense_buffer);
351
352         if (cmd->cmd_len == 0)
353                 cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);
354
355         /*
356          * We need saved copies of a number of fields - this is because
357          * error handling may need to overwrite these with different values
358          * to run different commands, and once error handling is complete,
359          * we will need to restore these values prior to running the actual
360          * command.
361          */
362         cmd->old_use_sg = cmd->use_sg;
363         cmd->old_cmd_len = cmd->cmd_len;
364         cmd->sc_old_data_direction = cmd->sc_data_direction;
365         cmd->old_underflow = cmd->underflow;
366         memcpy(cmd->data_cmnd, cmd->cmnd, sizeof(cmd->cmnd));
367         cmd->buffer = cmd->request_buffer;
368         cmd->bufflen = cmd->request_bufflen;
369
370         return 1;
371 }
372
373 /*
374  * Function:   scsi_setup_cmd_retry()
375  *
376  * Purpose:    Restore the command state for a retry
377  *
378  * Arguments:  cmd      - command to be restored
379  *
380  * Returns:    Nothing
381  *
382  * Notes:      Immediately prior to retrying a command, we need
383  *             to restore certain fields that we saved above.
384  */
385 void scsi_setup_cmd_retry(struct scsi_cmnd *cmd)
386 {
387         memcpy(cmd->cmnd, cmd->data_cmnd, sizeof(cmd->data_cmnd));
388         cmd->request_buffer = cmd->buffer;
389         cmd->request_bufflen = cmd->bufflen;
390         cmd->use_sg = cmd->old_use_sg;
391         cmd->cmd_len = cmd->old_cmd_len;
392         cmd->sc_data_direction = cmd->sc_old_data_direction;
393         cmd->underflow = cmd->old_underflow;
394 }
395
396 void scsi_device_unbusy(struct scsi_device *sdev)
397 {
398         struct Scsi_Host *shost = sdev->host;
399         unsigned long flags;
400
401         spin_lock_irqsave(shost->host_lock, flags);
402         shost->host_busy--;
403         if (unlikely((shost->shost_state == SHOST_RECOVERY) &&
404                      shost->host_failed))
405                 scsi_eh_wakeup(shost);
406         spin_unlock(shost->host_lock);
407         spin_lock(sdev->request_queue->queue_lock);
408         sdev->device_busy--;
409         spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
410 }
411
412 /*
413  * Called for single_lun devices on IO completion. Clear starget_sdev_user,
414  * and call blk_run_queue for all the scsi_devices on the target -
415  * including current_sdev first.
416  *
417  * Called with *no* scsi locks held.
418  */
419 static void scsi_single_lun_run(struct scsi_device *current_sdev)
420 {
421         struct Scsi_Host *shost = current_sdev->host;
422         struct scsi_device *sdev, *tmp;
423         struct scsi_target *starget = scsi_target(current_sdev);
424         unsigned long flags;
425
426         spin_lock_irqsave(shost->host_lock, flags);
427         starget->starget_sdev_user = NULL;
428         spin_unlock_irqrestore(shost->host_lock, flags);
429
430         /*
431          * Call blk_run_queue for all LUNs on the target, starting with
432          * current_sdev. We race with others (to set starget_sdev_user),
433          * but in most cases, we will be first. Ideally, each LU on the
434          * target would get some limited time or requests on the target.
435          */
436         blk_run_queue(current_sdev->request_queue);
437
438         spin_lock_irqsave(shost->host_lock, flags);
439         if (starget->starget_sdev_user)
440                 goto out;
441         list_for_each_entry_safe(sdev, tmp, &starget->devices,
442                         same_target_siblings) {
443                 if (sdev == current_sdev)
444                         continue;
445                 if (scsi_device_get(sdev))
446                         continue;
447
448                 spin_unlock_irqrestore(shost->host_lock, flags);
449                 blk_run_queue(sdev->request_queue);
450                 spin_lock_irqsave(shost->host_lock, flags);
451         
452                 scsi_device_put(sdev);
453         }
454  out:
455         spin_unlock_irqrestore(shost->host_lock, flags);
456 }
457
458 /*
459  * Function:    scsi_run_queue()
460  *
461  * Purpose:     Select a proper request queue to serve next
462  *
463  * Arguments:   q       - last request's queue
464  *
465  * Returns:     Nothing
466  *
467  * Notes:       The previous command was completely finished, start
468  *              a new one if possible.
469  */
470 static void scsi_run_queue(struct request_queue *q)
471 {
472         struct scsi_device *sdev = q->queuedata;
473         struct Scsi_Host *shost = sdev->host;
474         unsigned long flags;
475
476         if (sdev->single_lun)
477                 scsi_single_lun_run(sdev);
478
479         spin_lock_irqsave(shost->host_lock, flags);
480         while (!list_empty(&shost->starved_list) &&
481                !shost->host_blocked && !shost->host_self_blocked &&
482                 !((shost->can_queue > 0) &&
483                   (shost->host_busy >= shost->can_queue))) {
484                 /*
485                  * As long as shost is accepting commands and we have
486                  * starved queues, call blk_run_queue. scsi_request_fn
487                  * drops the queue_lock and can add us back to the
488                  * starved_list.
489                  *
490                  * host_lock protects the starved_list and starved_entry.
491                  * scsi_request_fn must get the host_lock before checking
492                  * or modifying starved_list or starved_entry.
493                  */
494                 sdev = list_entry(shost->starved_list.next,
495                                           struct scsi_device, starved_entry);
496                 list_del_init(&sdev->starved_entry);
497                 spin_unlock_irqrestore(shost->host_lock, flags);
498
499                 blk_run_queue(sdev->request_queue);
500
501                 spin_lock_irqsave(shost->host_lock, flags);
502                 if (unlikely(!list_empty(&sdev->starved_entry)))
503                         /*
504                          * sdev lost a race, and was put back on the
505                          * starved list. This is unlikely but without this
506                          * in theory we could loop forever.
507                          */
508                         break;
509         }
510         spin_unlock_irqrestore(shost->host_lock, flags);
511
512         blk_run_queue(q);
513 }
514
515 /*
516  * Function:    scsi_requeue_command()
517  *
518  * Purpose:     Handle post-processing of completed commands.
519  *
520  * Arguments:   q       - queue to operate on
521  *              cmd     - command that may need to be requeued.
522  *
523  * Returns:     Nothing
524  *
525  * Notes:       After command completion, there may be blocks left
526  *              over which weren't finished by the previous command
527  *              this can be for a number of reasons - the main one is
528  *              I/O errors in the middle of the request, in which case
529  *              we need to request the blocks that come after the bad
530  *              sector.
531  */
532 static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
533 {
534         unsigned long flags;
535
536         cmd->request->flags &= ~REQ_DONTPREP;
537
538         spin_lock_irqsave(q->queue_lock, flags);
539         blk_requeue_request(q, cmd->request);
540         spin_unlock_irqrestore(q->queue_lock, flags);
541
542         scsi_run_queue(q);
543 }
544
545 void scsi_next_command(struct scsi_cmnd *cmd)
546 {
547         struct request_queue *q = cmd->device->request_queue;
548
549         scsi_put_command(cmd);
550         scsi_run_queue(q);
551 }
552
553 void scsi_run_host_queues(struct Scsi_Host *shost)
554 {
555         struct scsi_device *sdev;
556
557         shost_for_each_device(sdev, shost)
558                 scsi_run_queue(sdev->request_queue);
559 }
560
561 /*
562  * Function:    scsi_end_request()
563  *
564  * Purpose:     Post-processing of completed commands (usually invoked at end
565  *              of upper level post-processing and scsi_io_completion).
566  *
567  * Arguments:   cmd      - command that is complete.
568  *              uptodate - 1 if I/O indicates success, <= 0 for I/O error.
569  *              bytes    - number of bytes of completed I/O
570  *              requeue  - indicates whether we should requeue leftovers.
571  *
572  * Lock status: Assumed that lock is not held upon entry.
573  *
574  * Returns:     cmd if requeue done or required, NULL otherwise
575  *
576  * Notes:       This is called for block device requests in order to
577  *              mark some number of sectors as complete.
578  * 
579  *              We are guaranteeing that the request queue will be goosed
580  *              at some point during this call.
581  */
582 static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int uptodate,
583                                           int bytes, int requeue)
584 {
585         request_queue_t *q = cmd->device->request_queue;
586         struct request *req = cmd->request;
587         unsigned long flags;
588
589         /*
590          * If there are blocks left over at the end, set up the command
591          * to queue the remainder of them.
592          */
593         if (end_that_request_chunk(req, uptodate, bytes)) {
594                 int leftover = (req->hard_nr_sectors << 9);
595
596                 if (blk_pc_request(req))
597                         leftover = req->data_len;
598
599                 /* kill remainder if no retrys */
600                 if (!uptodate && blk_noretry_request(req))
601                         end_that_request_chunk(req, 0, leftover);
602                 else {
603                         if (requeue)
604                                 /*
605                                  * Bleah.  Leftovers again.  Stick the
606                                  * leftovers in the front of the
607                                  * queue, and goose the queue again.
608                                  */
609                                 scsi_requeue_command(q, cmd);
610
611                         return cmd;
612                 }
613         }
614
615         add_disk_randomness(req->rq_disk);
616
617         spin_lock_irqsave(q->queue_lock, flags);
618         if (blk_rq_tagged(req))
619                 blk_queue_end_tag(q, req);
620         end_that_request_last(req);
621         spin_unlock_irqrestore(q->queue_lock, flags);
622
623         /*
624          * This will goose the queue request function at the end, so we don't
625          * need to worry about launching another command.
626          */
627         scsi_next_command(cmd);
628         return NULL;
629 }
630
631 static struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, int gfp_mask)
632 {
633         struct scsi_host_sg_pool *sgp;
634         struct scatterlist *sgl;
635
636         BUG_ON(!cmd->use_sg);
637
638         switch (cmd->use_sg) {
639         case 1 ... 8:
640                 cmd->sglist_len = 0;
641                 break;
642         case 9 ... 16:
643                 cmd->sglist_len = 1;
644                 break;
645         case 17 ... 32:
646                 cmd->sglist_len = 2;
647                 break;
648 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
649         case 33 ... 64:
650                 cmd->sglist_len = 3;
651                 break;
652 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
653         case 65 ... 128:
654                 cmd->sglist_len = 4;
655                 break;
656 #if (SCSI_MAX_PHYS_SEGMENTS  > 128)
657         case 129 ... 256:
658                 cmd->sglist_len = 5;
659                 break;
660 #endif
661 #endif
662 #endif
663         default:
664                 return NULL;
665         }
666
667         sgp = scsi_sg_pools + cmd->sglist_len;
668         sgl = mempool_alloc(sgp->pool, gfp_mask);
669         return sgl;
670 }
671
672 static void scsi_free_sgtable(struct scatterlist *sgl, int index)
673 {
674         struct scsi_host_sg_pool *sgp;
675
676         BUG_ON(index >= SG_MEMPOOL_NR);
677
678         sgp = scsi_sg_pools + index;
679         mempool_free(sgl, sgp->pool);
680 }
681
682 /*
683  * Function:    scsi_release_buffers()
684  *
685  * Purpose:     Completion processing for block device I/O requests.
686  *
687  * Arguments:   cmd     - command that we are bailing.
688  *
689  * Lock status: Assumed that no lock is held upon entry.
690  *
691  * Returns:     Nothing
692  *
693  * Notes:       In the event that an upper level driver rejects a
694  *              command, we must release resources allocated during
695  *              the __init_io() function.  Primarily this would involve
696  *              the scatter-gather table, and potentially any bounce
697  *              buffers.
698  */
699 static void scsi_release_buffers(struct scsi_cmnd *cmd)
700 {
701         struct request *req = cmd->request;
702
703         /*
704          * Free up any indirection buffers we allocated for DMA purposes. 
705          */
706         if (cmd->use_sg)
707                 scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
708         else if (cmd->request_buffer != req->buffer)
709                 kfree(cmd->request_buffer);
710
711         /*
712          * Zero these out.  They now point to freed memory, and it is
713          * dangerous to hang onto the pointers.
714          */
715         cmd->buffer  = NULL;
716         cmd->bufflen = 0;
717         cmd->request_buffer = NULL;
718         cmd->request_bufflen = 0;
719 }
720
721 /*
722  * Function:    scsi_io_completion()
723  *
724  * Purpose:     Completion processing for block device I/O requests.
725  *
726  * Arguments:   cmd   - command that is finished.
727  *
728  * Lock status: Assumed that no lock is held upon entry.
729  *
730  * Returns:     Nothing
731  *
732  * Notes:       This function is matched in terms of capabilities to
733  *              the function that created the scatter-gather list.
734  *              In other words, if there are no bounce buffers
735  *              (the normal case for most drivers), we don't need
736  *              the logic to deal with cleaning up afterwards.
737  *
738  *              We must do one of several things here:
739  *
740  *              a) Call scsi_end_request.  This will finish off the
741  *                 specified number of sectors.  If we are done, the
742  *                 command block will be released, and the queue
743  *                 function will be goosed.  If we are not done, then
744  *                 scsi_end_request will directly goose the queue.
745  *
746  *              b) We can just use scsi_requeue_command() here.  This would
747  *                 be used if we just wanted to retry, for example.
748  */
749 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
750                         unsigned int block_bytes)
751 {
752         int result = cmd->result;
753         int this_count = cmd->bufflen;
754         request_queue_t *q = cmd->device->request_queue;
755         struct request *req = cmd->request;
756         int clear_errors = 1;
757         struct scsi_sense_hdr sshdr;
758         int sense_valid = 0;
759         int sense_deferred = 0;
760
761         if (blk_complete_barrier_rq(q, req, good_bytes >> 9))
762                 return;
763
764         /*
765          * Free up any indirection buffers we allocated for DMA purposes. 
766          * For the case of a READ, we need to copy the data out of the
767          * bounce buffer and into the real buffer.
768          */
769         if (cmd->use_sg)
770                 scsi_free_sgtable(cmd->buffer, cmd->sglist_len);
771         else if (cmd->buffer != req->buffer) {
772                 if (rq_data_dir(req) == READ) {
773                         unsigned long flags;
774                         char *to = bio_kmap_irq(req->bio, &flags);
775                         memcpy(to, cmd->buffer, cmd->bufflen);
776                         bio_kunmap_irq(to, &flags);
777                 }
778                 kfree(cmd->buffer);
779         }
780
781         if (result) {
782                 sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
783                 if (sense_valid)
784                         sense_deferred = scsi_sense_is_deferred(&sshdr);
785         }
786         if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
787                 req->errors = result;
788                 if (result) {
789                         clear_errors = 0;
790                         if (sense_valid && req->sense) {
791                                 /*
792                                  * SG_IO wants current and deferred errors
793                                  */
794                                 int len = 8 + cmd->sense_buffer[7];
795
796                                 if (len > SCSI_SENSE_BUFFERSIZE)
797                                         len = SCSI_SENSE_BUFFERSIZE;
798                                 memcpy(req->sense, cmd->sense_buffer,  len);
799                                 req->sense_len = len;
800                         }
801                 } else
802                         req->data_len = cmd->resid;
803         }
804
805         /*
806          * Zero these out.  They now point to freed memory, and it is
807          * dangerous to hang onto the pointers.
808          */
809         cmd->buffer  = NULL;
810         cmd->bufflen = 0;
811         cmd->request_buffer = NULL;
812         cmd->request_bufflen = 0;
813
814         /*
815          * Next deal with any sectors which we were able to correctly
816          * handle.
817          */
818         if (good_bytes >= 0) {
819                 SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, %d bytes done.\n",
820                                               req->nr_sectors, good_bytes));
821                 SCSI_LOG_HLCOMPLETE(1, printk("use_sg is %d\n", cmd->use_sg));
822
823                 if (clear_errors)
824                         req->errors = 0;
825                 /*
826                  * If multiple sectors are requested in one buffer, then
827                  * they will have been finished off by the first command.
828                  * If not, then we have a multi-buffer command.
829                  *
830                  * If block_bytes != 0, it means we had a medium error
831                  * of some sort, and that we want to mark some number of
832                  * sectors as not uptodate.  Thus we want to inhibit
833                  * requeueing right here - we will requeue down below
834                  * when we handle the bad sectors.
835                  */
836                 cmd = scsi_end_request(cmd, 1, good_bytes, result == 0);
837
838                 /*
839                  * If the command completed without error, then either finish off the
840                  * rest of the command, or start a new one.
841                  */
842                 if (result == 0 || cmd == NULL ) {
843                         return;
844                 }
845         }
846         /*
847          * Now, if we were good little boys and girls, Santa left us a request
848          * sense buffer.  We can extract information from this, so we
849          * can choose a block to remap, etc.
850          */
851         if (sense_valid && !sense_deferred) {
852                 switch (sshdr.sense_key) {
853                 case UNIT_ATTENTION:
854                         if (cmd->device->removable) {
855                                 /* detected disc change.  set a bit 
856                                  * and quietly refuse further access.
857                                  */
858                                 cmd->device->changed = 1;
859                                 cmd = scsi_end_request(cmd, 0,
860                                                 this_count, 1);
861                                 return;
862                         } else {
863                                 /*
864                                 * Must have been a power glitch, or a
865                                 * bus reset.  Could not have been a
866                                 * media change, so we just retry the
867                                 * request and see what happens.  
868                                 */
869                                 scsi_requeue_command(q, cmd);
870                                 return;
871                         }
872                         break;
873                 case ILLEGAL_REQUEST:
874                         /*
875                         * If we had an ILLEGAL REQUEST returned, then we may
876                         * have performed an unsupported command.  The only
877                         * thing this should be would be a ten byte read where
878                         * only a six byte read was supported.  Also, on a
879                         * system where READ CAPACITY failed, we may have read
880                         * past the end of the disk.
881                         */
882                         if (cmd->device->use_10_for_rw &&
883                             (cmd->cmnd[0] == READ_10 ||
884                              cmd->cmnd[0] == WRITE_10)) {
885                                 cmd->device->use_10_for_rw = 0;
886                                 /*
887                                  * This will cause a retry with a 6-byte
888                                  * command.
889                                  */
890                                 scsi_requeue_command(q, cmd);
891                                 result = 0;
892                         } else {
893                                 cmd = scsi_end_request(cmd, 0, this_count, 1);
894                                 return;
895                         }
896                         break;
897                 case NOT_READY:
898                         /*
899                          * If the device is in the process of becoming ready,
900                          * retry.
901                          */
902                         if (sshdr.asc == 0x04 && sshdr.ascq == 0x01) {
903                                 scsi_requeue_command(q, cmd);
904                                 return;
905                         }
906                         printk(KERN_INFO "Device %s not ready.\n",
907                                req->rq_disk ? req->rq_disk->disk_name : "");
908                         cmd = scsi_end_request(cmd, 0, this_count, 1);
909                         return;
910                 case VOLUME_OVERFLOW:
911                         printk(KERN_INFO "Volume overflow <%d %d %d %d> CDB: ",
912                                cmd->device->host->host_no,
913                                (int)cmd->device->channel,
914                                (int)cmd->device->id, (int)cmd->device->lun);
915                         __scsi_print_command(cmd->data_cmnd);
916                         scsi_print_sense("", cmd);
917                         cmd = scsi_end_request(cmd, 0, block_bytes, 1);
918                         return;
919                 default:
920                         break;
921                 }
922         }                       /* driver byte != 0 */
923         if (host_byte(result) == DID_RESET) {
924                 /*
925                  * Third party bus reset or reset for error
926                  * recovery reasons.  Just retry the request
927                  * and see what happens.  
928                  */
929                 scsi_requeue_command(q, cmd);
930                 return;
931         }
932         if (result) {
933                 if (!(req->flags & REQ_SPECIAL))
934                         printk(KERN_INFO "SCSI error : <%d %d %d %d> return code "
935                                "= 0x%x\n", cmd->device->host->host_no,
936                                cmd->device->channel,
937                                cmd->device->id,
938                                cmd->device->lun, result);
939
940                 if (driver_byte(result) & DRIVER_SENSE)
941                         scsi_print_sense("", cmd);
942                 /*
943                  * Mark a single buffer as not uptodate.  Queue the remainder.
944                  * We sometimes get this cruft in the event that a medium error
945                  * isn't properly reported.
946                  */
947                 block_bytes = req->hard_cur_sectors << 9;
948                 if (!block_bytes)
949                         block_bytes = req->data_len;
950                 cmd = scsi_end_request(cmd, 0, block_bytes, 1);
951         }
952 }
953 EXPORT_SYMBOL(scsi_io_completion);
954
955 /*
956  * Function:    scsi_init_io()
957  *
958  * Purpose:     SCSI I/O initialize function.
959  *
960  * Arguments:   cmd   - Command descriptor we wish to initialize
961  *
962  * Returns:     0 on success
963  *              BLKPREP_DEFER if the failure is retryable
964  *              BLKPREP_KILL if the failure is fatal
965  */
966 static int scsi_init_io(struct scsi_cmnd *cmd)
967 {
968         struct request     *req = cmd->request;
969         struct scatterlist *sgpnt;
970         int                count;
971
972         /*
973          * if this is a rq->data based REQ_BLOCK_PC, setup for a non-sg xfer
974          */
975         if ((req->flags & REQ_BLOCK_PC) && !req->bio) {
976                 cmd->request_bufflen = req->data_len;
977                 cmd->request_buffer = req->data;
978                 req->buffer = req->data;
979                 cmd->use_sg = 0;
980                 return 0;
981         }
982
983         /*
984          * we used to not use scatter-gather for single segment request,
985          * but now we do (it makes highmem I/O easier to support without
986          * kmapping pages)
987          */
988         cmd->use_sg = req->nr_phys_segments;
989
990         /*
991          * if sg table allocation fails, requeue request later.
992          */
993         sgpnt = scsi_alloc_sgtable(cmd, GFP_ATOMIC);
994         if (unlikely(!sgpnt))
995                 return BLKPREP_DEFER;
996
997         cmd->request_buffer = (char *) sgpnt;
998         cmd->request_bufflen = req->nr_sectors << 9;
999         if (blk_pc_request(req))
1000                 cmd->request_bufflen = req->data_len;
1001         req->buffer = NULL;
1002
1003         /* 
1004          * Next, walk the list, and fill in the addresses and sizes of
1005          * each segment.
1006          */
1007         count = blk_rq_map_sg(req->q, req, cmd->request_buffer);
1008
1009         /*
1010          * mapped well, send it off
1011          */
1012         if (likely(count <= cmd->use_sg)) {
1013                 cmd->use_sg = count;
1014                 return 0;
1015         }
1016
1017         printk(KERN_ERR "Incorrect number of segments after building list\n");
1018         printk(KERN_ERR "counted %d, received %d\n", count, cmd->use_sg);
1019         printk(KERN_ERR "req nr_sec %lu, cur_nr_sec %u\n", req->nr_sectors,
1020                         req->current_nr_sectors);
1021
1022         /* release the command and kill it */
1023         scsi_release_buffers(cmd);
1024         scsi_put_command(cmd);
1025         return BLKPREP_KILL;
1026 }
1027
1028 static int scsi_prepare_flush_fn(request_queue_t *q, struct request *rq)
1029 {
1030         struct scsi_device *sdev = q->queuedata;
1031         struct scsi_driver *drv;
1032
1033         if (sdev->sdev_state == SDEV_RUNNING) {
1034                 drv = *(struct scsi_driver **) rq->rq_disk->private_data;
1035
1036                 if (drv->prepare_flush)
1037                         return drv->prepare_flush(q, rq);
1038         }
1039
1040         return 0;
1041 }
1042
1043 static void scsi_end_flush_fn(request_queue_t *q, struct request *rq)
1044 {
1045         struct scsi_device *sdev = q->queuedata;
1046         struct request *flush_rq = rq->end_io_data;
1047         struct scsi_driver *drv;
1048
1049         if (flush_rq->errors) {
1050                 printk("scsi: barrier error, disabling flush support\n");
1051                 blk_queue_ordered(q, QUEUE_ORDERED_NONE);
1052         }
1053
1054         if (sdev->sdev_state == SDEV_RUNNING) {
1055                 drv = *(struct scsi_driver **) rq->rq_disk->private_data;
1056                 drv->end_flush(q, rq);
1057         }
1058 }
1059
1060 static int scsi_issue_flush_fn(request_queue_t *q, struct gendisk *disk,
1061                                sector_t *error_sector)
1062 {
1063         struct scsi_device *sdev = q->queuedata;
1064         struct scsi_driver *drv;
1065
1066         if (sdev->sdev_state != SDEV_RUNNING)
1067                 return -ENXIO;
1068
1069         drv = *(struct scsi_driver **) disk->private_data;
1070         if (drv->issue_flush)
1071                 return drv->issue_flush(&sdev->sdev_gendev, error_sector);
1072
1073         return -EOPNOTSUPP;
1074 }
1075
1076 static void scsi_generic_done(struct scsi_cmnd *cmd)
1077 {
1078         BUG_ON(!blk_pc_request(cmd->request));
1079         scsi_io_completion(cmd, cmd->result == 0 ? cmd->bufflen : 0, 0);
1080 }
1081
1082 static int scsi_prep_fn(struct request_queue *q, struct request *req)
1083 {
1084         struct scsi_device *sdev = q->queuedata;
1085         struct scsi_cmnd *cmd;
1086         int specials_only = 0;
1087
1088         /*
1089          * Just check to see if the device is online.  If it isn't, we
1090          * refuse to process any commands.  The device must be brought
1091          * online before trying any recovery commands
1092          */
1093         if (unlikely(!scsi_device_online(sdev))) {
1094                 printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to offline device\n",
1095                        sdev->host->host_no, sdev->id, sdev->lun);
1096                 return BLKPREP_KILL;
1097         }
1098         if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
1099                 /* OK, we're not in a running state don't prep
1100                  * user commands */
1101                 if (sdev->sdev_state == SDEV_DEL) {
1102                         /* Device is fully deleted, no commands
1103                          * at all allowed down */
1104                         printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to dead device\n",
1105                                sdev->host->host_no, sdev->id, sdev->lun);
1106                         return BLKPREP_KILL;
1107                 }
1108                 /* OK, we only allow special commands (i.e. not
1109                  * user initiated ones */
1110                 specials_only = sdev->sdev_state;
1111         }
1112
1113         /*
1114          * Find the actual device driver associated with this command.
1115          * The SPECIAL requests are things like character device or
1116          * ioctls, which did not originate from ll_rw_blk.  Note that
1117          * the special field is also used to indicate the cmd for
1118          * the remainder of a partially fulfilled request that can 
1119          * come up when there is a medium error.  We have to treat
1120          * these two cases differently.  We differentiate by looking
1121          * at request->cmd, as this tells us the real story.
1122          */
1123         if (req->flags & REQ_SPECIAL && req->special) {
1124                 struct scsi_request *sreq = req->special;
1125
1126                 if (sreq->sr_magic == SCSI_REQ_MAGIC) {
1127                         cmd = scsi_get_command(sreq->sr_device, GFP_ATOMIC);
1128                         if (unlikely(!cmd))
1129                                 goto defer;
1130                         scsi_init_cmd_from_req(cmd, sreq);
1131                 } else
1132                         cmd = req->special;
1133         } else if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1134
1135                 if(unlikely(specials_only) && !(req->flags & REQ_SPECIAL)) {
1136                         if(specials_only == SDEV_QUIESCE ||
1137                                         specials_only == SDEV_BLOCK)
1138                                 return BLKPREP_DEFER;
1139                         
1140                         printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to device being removed\n",
1141                                sdev->host->host_no, sdev->id, sdev->lun);
1142                         return BLKPREP_KILL;
1143                 }
1144                         
1145                         
1146                 /*
1147                  * Now try and find a command block that we can use.
1148                  */
1149                 if (!req->special) {
1150                         cmd = scsi_get_command(sdev, GFP_ATOMIC);
1151                         if (unlikely(!cmd))
1152                                 goto defer;
1153                 } else
1154                         cmd = req->special;
1155                 
1156                 /* pull a tag out of the request if we have one */
1157                 cmd->tag = req->tag;
1158         } else {
1159                 blk_dump_rq_flags(req, "SCSI bad req");
1160                 return BLKPREP_KILL;
1161         }
1162         
1163         /* note the overloading of req->special.  When the tag
1164          * is active it always means cmd.  If the tag goes
1165          * back for re-queueing, it may be reset */
1166         req->special = cmd;
1167         cmd->request = req;
1168         
1169         /*
1170          * FIXME: drop the lock here because the functions below
1171          * expect to be called without the queue lock held.  Also,
1172          * previously, we dequeued the request before dropping the
1173          * lock.  We hope REQ_STARTED prevents anything untoward from
1174          * happening now.
1175          */
1176         if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1177                 struct scsi_driver *drv;
1178                 int ret;
1179
1180                 /*
1181                  * This will do a couple of things:
1182                  *  1) Fill in the actual SCSI command.
1183                  *  2) Fill in any other upper-level specific fields
1184                  * (timeout).
1185                  *
1186                  * If this returns 0, it means that the request failed
1187                  * (reading past end of disk, reading offline device,
1188                  * etc).   This won't actually talk to the device, but
1189                  * some kinds of consistency checking may cause the     
1190                  * request to be rejected immediately.
1191                  */
1192
1193                 /* 
1194                  * This sets up the scatter-gather table (allocating if
1195                  * required).
1196                  */
1197                 ret = scsi_init_io(cmd);
1198                 if (ret)        /* BLKPREP_KILL return also releases the command */
1199                         return ret;
1200                 
1201                 /*
1202                  * Initialize the actual SCSI command for this request.
1203                  */
1204                 if (req->rq_disk) {
1205                         drv = *(struct scsi_driver **)req->rq_disk->private_data;
1206                         if (unlikely(!drv->init_command(cmd))) {
1207                                 scsi_release_buffers(cmd);
1208                                 scsi_put_command(cmd);
1209                                 return BLKPREP_KILL;
1210                         }
1211                 } else {
1212                         memcpy(cmd->cmnd, req->cmd, sizeof(cmd->cmnd));
1213                         if (rq_data_dir(req) == WRITE)
1214                                 cmd->sc_data_direction = DMA_TO_DEVICE;
1215                         else if (req->data_len)
1216                                 cmd->sc_data_direction = DMA_FROM_DEVICE;
1217                         else
1218                                 cmd->sc_data_direction = DMA_NONE;
1219                         
1220                         cmd->transfersize = req->data_len;
1221                         cmd->allowed = 3;
1222                         cmd->timeout_per_command = req->timeout;
1223                         cmd->done = scsi_generic_done;
1224                 }
1225         }
1226
1227         /*
1228          * The request is now prepped, no need to come back here
1229          */
1230         req->flags |= REQ_DONTPREP;
1231         return BLKPREP_OK;
1232
1233  defer:
1234         /* If we defer, the elv_next_request() returns NULL, but the
1235          * queue must be restarted, so we plug here if no returning
1236          * command will automatically do that. */
1237         if (sdev->device_busy == 0)
1238                 blk_plug_device(q);
1239         return BLKPREP_DEFER;
1240 }
1241
1242 /*
1243  * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1244  * return 0.
1245  *
1246  * Called with the queue_lock held.
1247  */
1248 static inline int scsi_dev_queue_ready(struct request_queue *q,
1249                                   struct scsi_device *sdev)
1250 {
1251         if (sdev->device_busy >= sdev->queue_depth)
1252                 return 0;
1253         if (sdev->device_busy == 0 && sdev->device_blocked) {
1254                 /*
1255                  * unblock after device_blocked iterates to zero
1256                  */
1257                 if (--sdev->device_blocked == 0) {
1258                         SCSI_LOG_MLQUEUE(3,
1259                                 printk("scsi%d (%d:%d) unblocking device at"
1260                                        " zero depth\n", sdev->host->host_no,
1261                                        sdev->id, sdev->lun));
1262                 } else {
1263                         blk_plug_device(q);
1264                         return 0;
1265                 }
1266         }
1267         if (sdev->device_blocked)
1268                 return 0;
1269
1270         return 1;
1271 }
1272
1273 /*
1274  * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1275  * return 0. We must end up running the queue again whenever 0 is
1276  * returned, else IO can hang.
1277  *
1278  * Called with host_lock held.
1279  */
1280 static inline int scsi_host_queue_ready(struct request_queue *q,
1281                                    struct Scsi_Host *shost,
1282                                    struct scsi_device *sdev)
1283 {
1284         if (shost->shost_state == SHOST_RECOVERY)
1285                 return 0;
1286         if (shost->host_busy == 0 && shost->host_blocked) {
1287                 /*
1288                  * unblock after host_blocked iterates to zero
1289                  */
1290                 if (--shost->host_blocked == 0) {
1291                         SCSI_LOG_MLQUEUE(3,
1292                                 printk("scsi%d unblocking host at zero depth\n",
1293                                         shost->host_no));
1294                 } else {
1295                         blk_plug_device(q);
1296                         return 0;
1297                 }
1298         }
1299         if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
1300             shost->host_blocked || shost->host_self_blocked) {
1301                 if (list_empty(&sdev->starved_entry))
1302                         list_add_tail(&sdev->starved_entry, &shost->starved_list);
1303                 return 0;
1304         }
1305
1306         /* We're OK to process the command, so we can't be starved */
1307         if (!list_empty(&sdev->starved_entry))
1308                 list_del_init(&sdev->starved_entry);
1309
1310         return 1;
1311 }
1312
1313 /*
1314  * Kill requests for a dead device
1315  */
1316 static void scsi_kill_requests(request_queue_t *q)
1317 {
1318         struct request *req;
1319
1320         while ((req = elv_next_request(q)) != NULL) {
1321                 blkdev_dequeue_request(req);
1322                 req->flags |= REQ_QUIET;
1323                 while (end_that_request_first(req, 0, req->nr_sectors))
1324                         ;
1325                 end_that_request_last(req);
1326         }
1327 }
1328
1329 /*
1330  * Function:    scsi_request_fn()
1331  *
1332  * Purpose:     Main strategy routine for SCSI.
1333  *
1334  * Arguments:   q       - Pointer to actual queue.
1335  *
1336  * Returns:     Nothing
1337  *
1338  * Lock status: IO request lock assumed to be held when called.
1339  */
1340 static void scsi_request_fn(struct request_queue *q)
1341 {
1342         struct scsi_device *sdev = q->queuedata;
1343         struct Scsi_Host *shost;
1344         struct scsi_cmnd *cmd;
1345         struct request *req;
1346
1347         if (!sdev) {
1348                 printk("scsi: killing requests for dead queue\n");
1349                 scsi_kill_requests(q);
1350                 return;
1351         }
1352
1353         if(!get_device(&sdev->sdev_gendev))
1354                 /* We must be tearing the block queue down already */
1355                 return;
1356
1357         /*
1358          * To start with, we keep looping until the queue is empty, or until
1359          * the host is no longer able to accept any more requests.
1360          */
1361         shost = sdev->host;
1362         while (!blk_queue_plugged(q)) {
1363                 int rtn;
1364                 /*
1365                  * get next queueable request.  We do this early to make sure
1366                  * that the request is fully prepared even if we cannot 
1367                  * accept it.
1368                  */
1369                 req = elv_next_request(q);
1370                 if (!req || !scsi_dev_queue_ready(q, sdev))
1371                         break;
1372
1373                 if (unlikely(!scsi_device_online(sdev))) {
1374                         printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to offline device\n",
1375                                sdev->host->host_no, sdev->id, sdev->lun);
1376                         blkdev_dequeue_request(req);
1377                         req->flags |= REQ_QUIET;
1378                         while (end_that_request_first(req, 0, req->nr_sectors))
1379                                 ;
1380                         end_that_request_last(req);
1381                         continue;
1382                 }
1383
1384
1385                 /*
1386                  * Remove the request from the request list.
1387                  */
1388                 if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1389                         blkdev_dequeue_request(req);
1390                 sdev->device_busy++;
1391
1392                 spin_unlock(q->queue_lock);
1393                 spin_lock(shost->host_lock);
1394
1395                 if (!scsi_host_queue_ready(q, shost, sdev))
1396                         goto not_ready;
1397                 if (sdev->single_lun) {
1398                         if (scsi_target(sdev)->starget_sdev_user &&
1399                             scsi_target(sdev)->starget_sdev_user != sdev)
1400                                 goto not_ready;
1401                         scsi_target(sdev)->starget_sdev_user = sdev;
1402                 }
1403                 shost->host_busy++;
1404
1405                 /*
1406                  * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1407                  *              take the lock again.
1408                  */
1409                 spin_unlock_irq(shost->host_lock);
1410
1411                 cmd = req->special;
1412                 if (unlikely(cmd == NULL)) {
1413                         printk(KERN_CRIT "impossible request in %s.\n"
1414                                          "please mail a stack trace to "
1415                                          "linux-scsi@vger.kernel.org",
1416                                          __FUNCTION__);
1417                         BUG();
1418                 }
1419
1420                 /*
1421                  * Finally, initialize any error handling parameters, and set up
1422                  * the timers for timeouts.
1423                  */
1424                 scsi_init_cmd_errh(cmd);
1425
1426                 /*
1427                  * Dispatch the command to the low-level driver.
1428                  */
1429                 rtn = scsi_dispatch_cmd(cmd);
1430                 spin_lock_irq(q->queue_lock);
1431                 if(rtn) {
1432                         /* we're refusing the command; because of
1433                          * the way locks get dropped, we need to 
1434                          * check here if plugging is required */
1435                         if(sdev->device_busy == 0)
1436                                 blk_plug_device(q);
1437
1438                         break;
1439                 }
1440         }
1441
1442         goto out;
1443
1444  not_ready:
1445         spin_unlock_irq(shost->host_lock);
1446
1447         /*
1448          * lock q, handle tag, requeue req, and decrement device_busy. We
1449          * must return with queue_lock held.
1450          *
1451          * Decrementing device_busy without checking it is OK, as all such
1452          * cases (host limits or settings) should run the queue at some
1453          * later time.
1454          */
1455         spin_lock_irq(q->queue_lock);
1456         blk_requeue_request(q, req);
1457         sdev->device_busy--;
1458         if(sdev->device_busy == 0)
1459                 blk_plug_device(q);
1460  out:
1461         /* must be careful here...if we trigger the ->remove() function
1462          * we cannot be holding the q lock */
1463         spin_unlock_irq(q->queue_lock);
1464         put_device(&sdev->sdev_gendev);
1465         spin_lock_irq(q->queue_lock);
1466 }
1467
1468 u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1469 {
1470         struct device *host_dev;
1471         u64 bounce_limit = 0xffffffff;
1472
1473         if (shost->unchecked_isa_dma)
1474                 return BLK_BOUNCE_ISA;
1475         /*
1476          * Platforms with virtual-DMA translation
1477          * hardware have no practical limit.
1478          */
1479         if (!PCI_DMA_BUS_IS_PHYS)
1480                 return BLK_BOUNCE_ANY;
1481
1482         host_dev = scsi_get_device(shost);
1483         if (host_dev && host_dev->dma_mask)
1484                 bounce_limit = *host_dev->dma_mask;
1485
1486         return bounce_limit;
1487 }
1488 EXPORT_SYMBOL(scsi_calculate_bounce_limit);
1489
1490 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1491 {
1492         struct Scsi_Host *shost = sdev->host;
1493         struct request_queue *q;
1494
1495         q = blk_init_queue(scsi_request_fn, NULL);
1496         if (!q)
1497                 return NULL;
1498
1499         blk_queue_prep_rq(q, scsi_prep_fn);
1500
1501         blk_queue_max_hw_segments(q, shost->sg_tablesize);
1502         blk_queue_max_phys_segments(q, SCSI_MAX_PHYS_SEGMENTS);
1503         blk_queue_max_sectors(q, shost->max_sectors);
1504         blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1505         blk_queue_segment_boundary(q, shost->dma_boundary);
1506         blk_queue_issue_flush_fn(q, scsi_issue_flush_fn);
1507
1508         /*
1509          * ordered tags are superior to flush ordering
1510          */
1511         if (shost->ordered_tag)
1512                 blk_queue_ordered(q, QUEUE_ORDERED_TAG);
1513         else if (shost->ordered_flush) {
1514                 blk_queue_ordered(q, QUEUE_ORDERED_FLUSH);
1515                 q->prepare_flush_fn = scsi_prepare_flush_fn;
1516                 q->end_flush_fn = scsi_end_flush_fn;
1517         }
1518
1519         if (!shost->use_clustering)
1520                 clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
1521         return q;
1522 }
1523
1524 void scsi_free_queue(struct request_queue *q)
1525 {
1526         blk_cleanup_queue(q);
1527 }
1528
1529 /*
1530  * Function:    scsi_block_requests()
1531  *
1532  * Purpose:     Utility function used by low-level drivers to prevent further
1533  *              commands from being queued to the device.
1534  *
1535  * Arguments:   shost       - Host in question
1536  *
1537  * Returns:     Nothing
1538  *
1539  * Lock status: No locks are assumed held.
1540  *
1541  * Notes:       There is no timer nor any other means by which the requests
1542  *              get unblocked other than the low-level driver calling
1543  *              scsi_unblock_requests().
1544  */
1545 void scsi_block_requests(struct Scsi_Host *shost)
1546 {
1547         shost->host_self_blocked = 1;
1548 }
1549 EXPORT_SYMBOL(scsi_block_requests);
1550
1551 /*
1552  * Function:    scsi_unblock_requests()
1553  *
1554  * Purpose:     Utility function used by low-level drivers to allow further
1555  *              commands from being queued to the device.
1556  *
1557  * Arguments:   shost       - Host in question
1558  *
1559  * Returns:     Nothing
1560  *
1561  * Lock status: No locks are assumed held.
1562  *
1563  * Notes:       There is no timer nor any other means by which the requests
1564  *              get unblocked other than the low-level driver calling
1565  *              scsi_unblock_requests().
1566  *
1567  *              This is done as an API function so that changes to the
1568  *              internals of the scsi mid-layer won't require wholesale
1569  *              changes to drivers that use this feature.
1570  */
1571 void scsi_unblock_requests(struct Scsi_Host *shost)
1572 {
1573         shost->host_self_blocked = 0;
1574         scsi_run_host_queues(shost);
1575 }
1576 EXPORT_SYMBOL(scsi_unblock_requests);
1577
1578 int __init scsi_init_queue(void)
1579 {
1580         int i;
1581
1582         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1583                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1584                 int size = sgp->size * sizeof(struct scatterlist);
1585
1586                 sgp->slab = kmem_cache_create(sgp->name, size, 0,
1587                                 SLAB_HWCACHE_ALIGN, NULL, NULL);
1588                 if (!sgp->slab) {
1589                         printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1590                                         sgp->name);
1591                 }
1592
1593                 sgp->pool = mempool_create(SG_MEMPOOL_SIZE,
1594                                 mempool_alloc_slab, mempool_free_slab,
1595                                 sgp->slab);
1596                 if (!sgp->pool) {
1597                         printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1598                                         sgp->name);
1599                 }
1600         }
1601
1602         return 0;
1603 }
1604
1605 void scsi_exit_queue(void)
1606 {
1607         int i;
1608
1609         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1610                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1611                 mempool_destroy(sgp->pool);
1612                 kmem_cache_destroy(sgp->slab);
1613         }
1614 }
1615 /**
1616  *      __scsi_mode_sense - issue a mode sense, falling back from 10 to 
1617  *              six bytes if necessary.
1618  *      @sreq:  SCSI request to fill in with the MODE_SENSE
1619  *      @dbd:   set if mode sense will allow block descriptors to be returned
1620  *      @modepage: mode page being requested
1621  *      @buffer: request buffer (may not be smaller than eight bytes)
1622  *      @len:   length of request buffer.
1623  *      @timeout: command timeout
1624  *      @retries: number of retries before failing
1625  *      @data: returns a structure abstracting the mode header data
1626  *
1627  *      Returns zero if unsuccessful, or the header offset (either 4
1628  *      or 8 depending on whether a six or ten byte command was
1629  *      issued) if successful.
1630  **/
1631 int
1632 __scsi_mode_sense(struct scsi_request *sreq, int dbd, int modepage,
1633                   unsigned char *buffer, int len, int timeout, int retries,
1634                   struct scsi_mode_data *data) {
1635         unsigned char cmd[12];
1636         int use_10_for_ms;
1637         int header_length;
1638
1639         memset(data, 0, sizeof(*data));
1640         memset(&cmd[0], 0, 12);
1641         cmd[1] = dbd & 0x18;    /* allows DBD and LLBA bits */
1642         cmd[2] = modepage;
1643
1644  retry:
1645         use_10_for_ms = sreq->sr_device->use_10_for_ms;
1646
1647         if (use_10_for_ms) {
1648                 if (len < 8)
1649                         len = 8;
1650
1651                 cmd[0] = MODE_SENSE_10;
1652                 cmd[8] = len;
1653                 header_length = 8;
1654         } else {
1655                 if (len < 4)
1656                         len = 4;
1657
1658                 cmd[0] = MODE_SENSE;
1659                 cmd[4] = len;
1660                 header_length = 4;
1661         }
1662
1663         sreq->sr_cmd_len = 0;
1664         memset(sreq->sr_sense_buffer, 0, sizeof(sreq->sr_sense_buffer));
1665         sreq->sr_data_direction = DMA_FROM_DEVICE;
1666
1667         memset(buffer, 0, len);
1668
1669         scsi_wait_req(sreq, cmd, buffer, len, timeout, retries);
1670
1671         /* This code looks awful: what it's doing is making sure an
1672          * ILLEGAL REQUEST sense return identifies the actual command
1673          * byte as the problem.  MODE_SENSE commands can return
1674          * ILLEGAL REQUEST if the code page isn't supported */
1675
1676         if (use_10_for_ms && !scsi_status_is_good(sreq->sr_result) &&
1677             (driver_byte(sreq->sr_result) & DRIVER_SENSE)) {
1678                 struct scsi_sense_hdr sshdr;
1679
1680                 if (scsi_request_normalize_sense(sreq, &sshdr)) {
1681                         if ((sshdr.sense_key == ILLEGAL_REQUEST) &&
1682                             (sshdr.asc == 0x20) && (sshdr.ascq == 0)) {
1683                                 /* 
1684                                  * Invalid command operation code
1685                                  */
1686                                 sreq->sr_device->use_10_for_ms = 0;
1687                                 goto retry;
1688                         }
1689                 }
1690         }
1691
1692         if(scsi_status_is_good(sreq->sr_result)) {
1693                 data->header_length = header_length;
1694                 if(use_10_for_ms) {
1695                         data->length = buffer[0]*256 + buffer[1] + 2;
1696                         data->medium_type = buffer[2];
1697                         data->device_specific = buffer[3];
1698                         data->longlba = buffer[4] & 0x01;
1699                         data->block_descriptor_length = buffer[6]*256
1700                                 + buffer[7];
1701                 } else {
1702                         data->length = buffer[0] + 1;
1703                         data->medium_type = buffer[1];
1704                         data->device_specific = buffer[2];
1705                         data->block_descriptor_length = buffer[3];
1706                 }
1707         }
1708
1709         return sreq->sr_result;
1710 }
1711 EXPORT_SYMBOL(__scsi_mode_sense);
1712
1713 /**
1714  *      scsi_mode_sense - issue a mode sense, falling back from 10 to 
1715  *              six bytes if necessary.
1716  *      @sdev:  scsi device to send command to.
1717  *      @dbd:   set if mode sense will disable block descriptors in the return
1718  *      @modepage: mode page being requested
1719  *      @buffer: request buffer (may not be smaller than eight bytes)
1720  *      @len:   length of request buffer.
1721  *      @timeout: command timeout
1722  *      @retries: number of retries before failing
1723  *
1724  *      Returns zero if unsuccessful, or the header offset (either 4
1725  *      or 8 depending on whether a six or ten byte command was
1726  *      issued) if successful.
1727  **/
1728 int
1729 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
1730                 unsigned char *buffer, int len, int timeout, int retries,
1731                 struct scsi_mode_data *data)
1732 {
1733         struct scsi_request *sreq = scsi_allocate_request(sdev, GFP_KERNEL);
1734         int ret;
1735
1736         if (!sreq)
1737                 return -1;
1738
1739         ret = __scsi_mode_sense(sreq, dbd, modepage, buffer, len,
1740                                 timeout, retries, data);
1741
1742         scsi_release_request(sreq);
1743
1744         return ret;
1745 }
1746 EXPORT_SYMBOL(scsi_mode_sense);
1747
1748 int
1749 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries)
1750 {
1751         struct scsi_request *sreq;
1752         char cmd[] = {
1753                 TEST_UNIT_READY, 0, 0, 0, 0, 0,
1754         };
1755         int result;
1756         
1757         sreq = scsi_allocate_request(sdev, GFP_KERNEL);
1758         if (!sreq)
1759                 return -ENOMEM;
1760
1761         sreq->sr_data_direction = DMA_NONE;
1762         scsi_wait_req(sreq, cmd, NULL, 0, timeout, retries);
1763
1764         if ((driver_byte(sreq->sr_result) & DRIVER_SENSE) && sdev->removable) {
1765                 struct scsi_sense_hdr sshdr;
1766
1767                 if ((scsi_request_normalize_sense(sreq, &sshdr)) &&
1768                     ((sshdr.sense_key == UNIT_ATTENTION) ||
1769                      (sshdr.sense_key == NOT_READY))) {
1770                         sdev->changed = 1;
1771                         sreq->sr_result = 0;
1772                 }
1773         }
1774         result = sreq->sr_result;
1775         scsi_release_request(sreq);
1776         return result;
1777 }
1778 EXPORT_SYMBOL(scsi_test_unit_ready);
1779
1780 /**
1781  *      scsi_device_set_state - Take the given device through the device
1782  *              state model.
1783  *      @sdev:  scsi device to change the state of.
1784  *      @state: state to change to.
1785  *
1786  *      Returns zero if unsuccessful or an error if the requested 
1787  *      transition is illegal.
1788  **/
1789 int
1790 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
1791 {
1792         enum scsi_device_state oldstate = sdev->sdev_state;
1793
1794         if (state == oldstate)
1795                 return 0;
1796
1797         switch (state) {
1798         case SDEV_CREATED:
1799                 /* There are no legal states that come back to
1800                  * created.  This is the manually initialised start
1801                  * state */
1802                 goto illegal;
1803                         
1804         case SDEV_RUNNING:
1805                 switch (oldstate) {
1806                 case SDEV_CREATED:
1807                 case SDEV_OFFLINE:
1808                 case SDEV_QUIESCE:
1809                 case SDEV_BLOCK:
1810                         break;
1811                 default:
1812                         goto illegal;
1813                 }
1814                 break;
1815
1816         case SDEV_QUIESCE:
1817                 switch (oldstate) {
1818                 case SDEV_RUNNING:
1819                 case SDEV_OFFLINE:
1820                         break;
1821                 default:
1822                         goto illegal;
1823                 }
1824                 break;
1825
1826         case SDEV_OFFLINE:
1827                 switch (oldstate) {
1828                 case SDEV_CREATED:
1829                 case SDEV_RUNNING:
1830                 case SDEV_QUIESCE:
1831                 case SDEV_BLOCK:
1832                         break;
1833                 default:
1834                         goto illegal;
1835                 }
1836                 break;
1837
1838         case SDEV_BLOCK:
1839                 switch (oldstate) {
1840                 case SDEV_CREATED:
1841                 case SDEV_RUNNING:
1842                         break;
1843                 default:
1844                         goto illegal;
1845                 }
1846                 break;
1847
1848         case SDEV_CANCEL:
1849                 switch (oldstate) {
1850                 case SDEV_CREATED:
1851                 case SDEV_RUNNING:
1852                 case SDEV_OFFLINE:
1853                 case SDEV_BLOCK:
1854                         break;
1855                 default:
1856                         goto illegal;
1857                 }
1858                 break;
1859
1860         case SDEV_DEL:
1861                 switch (oldstate) {
1862                 case SDEV_CANCEL:
1863                         break;
1864                 default:
1865                         goto illegal;
1866                 }
1867                 break;
1868
1869         }
1870         sdev->sdev_state = state;
1871         return 0;
1872
1873  illegal:
1874         SCSI_LOG_ERROR_RECOVERY(1, 
1875                                 dev_printk(KERN_ERR, &sdev->sdev_gendev,
1876                                            "Illegal state transition %s->%s\n",
1877                                            scsi_device_state_name(oldstate),
1878                                            scsi_device_state_name(state))
1879                                 );
1880         return -EINVAL;
1881 }
1882 EXPORT_SYMBOL(scsi_device_set_state);
1883
1884 /**
1885  *      scsi_device_quiesce - Block user issued commands.
1886  *      @sdev:  scsi device to quiesce.
1887  *
1888  *      This works by trying to transition to the SDEV_QUIESCE state
1889  *      (which must be a legal transition).  When the device is in this
1890  *      state, only special requests will be accepted, all others will
1891  *      be deferred.  Since special requests may also be requeued requests,
1892  *      a successful return doesn't guarantee the device will be 
1893  *      totally quiescent.
1894  *
1895  *      Must be called with user context, may sleep.
1896  *
1897  *      Returns zero if unsuccessful or an error if not.
1898  **/
1899 int
1900 scsi_device_quiesce(struct scsi_device *sdev)
1901 {
1902         int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
1903         if (err)
1904                 return err;
1905
1906         scsi_run_queue(sdev->request_queue);
1907         while (sdev->device_busy) {
1908                 msleep_interruptible(200);
1909                 scsi_run_queue(sdev->request_queue);
1910         }
1911         return 0;
1912 }
1913 EXPORT_SYMBOL(scsi_device_quiesce);
1914
1915 /**
1916  *      scsi_device_resume - Restart user issued commands to a quiesced device.
1917  *      @sdev:  scsi device to resume.
1918  *
1919  *      Moves the device from quiesced back to running and restarts the
1920  *      queues.
1921  *
1922  *      Must be called with user context, may sleep.
1923  **/
1924 void
1925 scsi_device_resume(struct scsi_device *sdev)
1926 {
1927         if(scsi_device_set_state(sdev, SDEV_RUNNING))
1928                 return;
1929         scsi_run_queue(sdev->request_queue);
1930 }
1931 EXPORT_SYMBOL(scsi_device_resume);
1932
1933 static void
1934 device_quiesce_fn(struct scsi_device *sdev, void *data)
1935 {
1936         scsi_device_quiesce(sdev);
1937 }
1938
1939 void
1940 scsi_target_quiesce(struct scsi_target *starget)
1941 {
1942         starget_for_each_device(starget, NULL, device_quiesce_fn);
1943 }
1944 EXPORT_SYMBOL(scsi_target_quiesce);
1945
1946 static void
1947 device_resume_fn(struct scsi_device *sdev, void *data)
1948 {
1949         scsi_device_resume(sdev);
1950 }
1951
1952 void
1953 scsi_target_resume(struct scsi_target *starget)
1954 {
1955         starget_for_each_device(starget, NULL, device_resume_fn);
1956 }
1957 EXPORT_SYMBOL(scsi_target_resume);
1958
1959 /**
1960  * scsi_internal_device_block - internal function to put a device
1961  *                              temporarily into the SDEV_BLOCK state
1962  * @sdev:       device to block
1963  *
1964  * Block request made by scsi lld's to temporarily stop all
1965  * scsi commands on the specified device.  Called from interrupt
1966  * or normal process context.
1967  *
1968  * Returns zero if successful or error if not
1969  *
1970  * Notes:       
1971  *      This routine transitions the device to the SDEV_BLOCK state
1972  *      (which must be a legal transition).  When the device is in this
1973  *      state, all commands are deferred until the scsi lld reenables
1974  *      the device with scsi_device_unblock or device_block_tmo fires.
1975  *      This routine assumes the host_lock is held on entry.
1976  **/
1977 int
1978 scsi_internal_device_block(struct scsi_device *sdev)
1979 {
1980         request_queue_t *q = sdev->request_queue;
1981         unsigned long flags;
1982         int err = 0;
1983
1984         err = scsi_device_set_state(sdev, SDEV_BLOCK);
1985         if (err)
1986                 return err;
1987
1988         /* 
1989          * The device has transitioned to SDEV_BLOCK.  Stop the
1990          * block layer from calling the midlayer with this device's
1991          * request queue. 
1992          */
1993         spin_lock_irqsave(q->queue_lock, flags);
1994         blk_stop_queue(q);
1995         spin_unlock_irqrestore(q->queue_lock, flags);
1996
1997         return 0;
1998 }
1999 EXPORT_SYMBOL_GPL(scsi_internal_device_block);
2000  
2001 /**
2002  * scsi_internal_device_unblock - resume a device after a block request
2003  * @sdev:       device to resume
2004  *
2005  * Called by scsi lld's or the midlayer to restart the device queue
2006  * for the previously suspended scsi device.  Called from interrupt or
2007  * normal process context.
2008  *
2009  * Returns zero if successful or error if not.
2010  *
2011  * Notes:       
2012  *      This routine transitions the device to the SDEV_RUNNING state
2013  *      (which must be a legal transition) allowing the midlayer to
2014  *      goose the queue for this device.  This routine assumes the 
2015  *      host_lock is held upon entry.
2016  **/
2017 int
2018 scsi_internal_device_unblock(struct scsi_device *sdev)
2019 {
2020         request_queue_t *q = sdev->request_queue; 
2021         int err;
2022         unsigned long flags;
2023         
2024         /* 
2025          * Try to transition the scsi device to SDEV_RUNNING
2026          * and goose the device queue if successful.  
2027          */
2028         err = scsi_device_set_state(sdev, SDEV_RUNNING);
2029         if (err)
2030                 return err;
2031
2032         spin_lock_irqsave(q->queue_lock, flags);
2033         blk_start_queue(q);
2034         spin_unlock_irqrestore(q->queue_lock, flags);
2035
2036         return 0;
2037 }
2038 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
2039
2040 static void
2041 device_block(struct scsi_device *sdev, void *data)
2042 {
2043         scsi_internal_device_block(sdev);
2044 }
2045
2046 static int
2047 target_block(struct device *dev, void *data)
2048 {
2049         if (scsi_is_target_device(dev))
2050                 starget_for_each_device(to_scsi_target(dev), NULL,
2051                                         device_block);
2052         return 0;
2053 }
2054
2055 void
2056 scsi_target_block(struct device *dev)
2057 {
2058         if (scsi_is_target_device(dev))
2059                 starget_for_each_device(to_scsi_target(dev), NULL,
2060                                         device_block);
2061         else
2062                 device_for_each_child(dev, NULL, target_block);
2063 }
2064 EXPORT_SYMBOL_GPL(scsi_target_block);
2065
2066 static void
2067 device_unblock(struct scsi_device *sdev, void *data)
2068 {
2069         scsi_internal_device_unblock(sdev);
2070 }
2071
2072 static int
2073 target_unblock(struct device *dev, void *data)
2074 {
2075         if (scsi_is_target_device(dev))
2076                 starget_for_each_device(to_scsi_target(dev), NULL,
2077                                         device_unblock);
2078         return 0;
2079 }
2080
2081 void
2082 scsi_target_unblock(struct device *dev)
2083 {
2084         if (scsi_is_target_device(dev))
2085                 starget_for_each_device(to_scsi_target(dev), NULL,
2086                                         device_unblock);
2087         else
2088                 device_for_each_child(dev, NULL, target_unblock);
2089 }
2090 EXPORT_SYMBOL_GPL(scsi_target_unblock);