3ff538809786fb5647c0e8f2f6e74339aca0106d
[linux-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_unprep_request()
103  *
104  * Purpose:     Remove all preparation done for a request, including its
105  *              associated scsi_cmnd, so that it can be requeued.
106  *
107  * Arguments:   req     - request to unprepare
108  *
109  * Lock status: Assumed that no locks are held upon entry.
110  *
111  * Returns:     Nothing.
112  */
113 static void scsi_unprep_request(struct request *req)
114 {
115         struct scsi_cmnd *cmd = req->special;
116
117         req->flags &= ~REQ_DONTPREP;
118         req->special = (req->flags & REQ_SPECIAL) ? cmd->sc_request : NULL;
119
120         scsi_put_command(cmd);
121 }
122
123 /*
124  * Function:    scsi_queue_insert()
125  *
126  * Purpose:     Insert a command in the midlevel queue.
127  *
128  * Arguments:   cmd    - command that we are adding to queue.
129  *              reason - why we are inserting command to queue.
130  *
131  * Lock status: Assumed that lock is not held upon entry.
132  *
133  * Returns:     Nothing.
134  *
135  * Notes:       We do this for one of two cases.  Either the host is busy
136  *              and it cannot accept any more commands for the time being,
137  *              or the device returned QUEUE_FULL and can accept no more
138  *              commands.
139  * Notes:       This could be called either from an interrupt context or a
140  *              normal process context.
141  */
142 int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
143 {
144         struct Scsi_Host *host = cmd->device->host;
145         struct scsi_device *device = cmd->device;
146         struct request_queue *q = device->request_queue;
147         unsigned long flags;
148
149         SCSI_LOG_MLQUEUE(1,
150                  printk("Inserting command %p into mlqueue\n", cmd));
151
152         /*
153          * Set the appropriate busy bit for the device/host.
154          *
155          * If the host/device isn't busy, assume that something actually
156          * completed, and that we should be able to queue a command now.
157          *
158          * Note that the prior mid-layer assumption that any host could
159          * always queue at least one command is now broken.  The mid-layer
160          * will implement a user specifiable stall (see
161          * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
162          * if a command is requeued with no other commands outstanding
163          * either for the device or for the host.
164          */
165         if (reason == SCSI_MLQUEUE_HOST_BUSY)
166                 host->host_blocked = host->max_host_blocked;
167         else if (reason == SCSI_MLQUEUE_DEVICE_BUSY)
168                 device->device_blocked = device->max_device_blocked;
169
170         /*
171          * Decrement the counters, since these commands are no longer
172          * active on the host/device.
173          */
174         scsi_device_unbusy(device);
175
176         /*
177          * Requeue this command.  It will go before all other commands
178          * that are already in the queue.
179          *
180          * NOTE: there is magic here about the way the queue is plugged if
181          * we have no outstanding commands.
182          * 
183          * Although we *don't* plug the queue, we call the request
184          * function.  The SCSI request function detects the blocked condition
185          * and plugs the queue appropriately.
186          */
187         spin_lock_irqsave(q->queue_lock, flags);
188         blk_requeue_request(q, cmd->request);
189         spin_unlock_irqrestore(q->queue_lock, flags);
190
191         scsi_run_queue(q);
192
193         return 0;
194 }
195
196 /*
197  * Function:    scsi_do_req
198  *
199  * Purpose:     Queue a SCSI request
200  *
201  * Arguments:   sreq      - command descriptor.
202  *              cmnd      - actual SCSI command to be performed.
203  *              buffer    - data buffer.
204  *              bufflen   - size of data buffer.
205  *              done      - completion function to be run.
206  *              timeout   - how long to let it run before timeout.
207  *              retries   - number of retries we allow.
208  *
209  * Lock status: No locks held upon entry.
210  *
211  * Returns:     Nothing.
212  *
213  * Notes:       This function is only used for queueing requests for things
214  *              like ioctls and character device requests - this is because
215  *              we essentially just inject a request into the queue for the
216  *              device.
217  *
218  *              In order to support the scsi_device_quiesce function, we
219  *              now inject requests on the *head* of the device queue
220  *              rather than the tail.
221  */
222 void scsi_do_req(struct scsi_request *sreq, const void *cmnd,
223                  void *buffer, unsigned bufflen,
224                  void (*done)(struct scsi_cmnd *),
225                  int timeout, int retries)
226 {
227         /*
228          * If the upper level driver is reusing these things, then
229          * we should release the low-level block now.  Another one will
230          * be allocated later when this request is getting queued.
231          */
232         __scsi_release_request(sreq);
233
234         /*
235          * Our own function scsi_done (which marks the host as not busy,
236          * disables the timeout counter, etc) will be called by us or by the
237          * scsi_hosts[host].queuecommand() function needs to also call
238          * the completion function for the high level driver.
239          */
240         memcpy(sreq->sr_cmnd, cmnd, sizeof(sreq->sr_cmnd));
241         sreq->sr_bufflen = bufflen;
242         sreq->sr_buffer = buffer;
243         sreq->sr_allowed = retries;
244         sreq->sr_done = done;
245         sreq->sr_timeout_per_command = timeout;
246
247         if (sreq->sr_cmd_len == 0)
248                 sreq->sr_cmd_len = COMMAND_SIZE(sreq->sr_cmnd[0]);
249
250         /*
251          * head injection *required* here otherwise quiesce won't work
252          */
253         scsi_insert_special_req(sreq, 1);
254 }
255 EXPORT_SYMBOL(scsi_do_req);
256
257 /* This is the end routine we get to if a command was never attached
258  * to the request.  Simply complete the request without changing
259  * rq_status; this will cause a DRIVER_ERROR. */
260 static void scsi_wait_req_end_io(struct request *req)
261 {
262         BUG_ON(!req->waiting);
263
264         complete(req->waiting);
265 }
266
267 void scsi_wait_req(struct scsi_request *sreq, const void *cmnd, void *buffer,
268                    unsigned bufflen, int timeout, int retries)
269 {
270         DECLARE_COMPLETION(wait);
271         int write = (sreq->sr_data_direction == DMA_TO_DEVICE);
272         struct request *req;
273
274         req = blk_get_request(sreq->sr_device->request_queue, write,
275                               __GFP_WAIT);
276         if (bufflen && blk_rq_map_kern(sreq->sr_device->request_queue, req,
277                                        buffer, bufflen, __GFP_WAIT)) {
278                 sreq->sr_result = DRIVER_ERROR << 24;
279                 blk_put_request(req);
280                 return;
281         }
282
283         req->flags |= REQ_NOMERGE;
284         req->waiting = &wait;
285         req->end_io = scsi_wait_req_end_io;
286         req->cmd_len = COMMAND_SIZE(((u8 *)cmnd)[0]);
287         req->sense = sreq->sr_sense_buffer;
288         req->sense_len = 0;
289         memcpy(req->cmd, cmnd, req->cmd_len);
290         req->timeout = timeout;
291         req->flags |= REQ_BLOCK_PC;
292         req->rq_disk = NULL;
293         blk_insert_request(sreq->sr_device->request_queue, req,
294                            sreq->sr_data_direction == DMA_TO_DEVICE, NULL);
295         wait_for_completion(&wait);
296         sreq->sr_request->waiting = NULL;
297         sreq->sr_result = req->errors;
298         if (req->errors)
299                 sreq->sr_result |= (DRIVER_ERROR << 24);
300
301         blk_put_request(req);
302 }
303
304 EXPORT_SYMBOL(scsi_wait_req);
305
306 /**
307  * scsi_execute - insert request and wait for the result
308  * @sdev:       scsi device
309  * @cmd:        scsi command
310  * @data_direction: data direction
311  * @buffer:     data buffer
312  * @bufflen:    len of buffer
313  * @sense:      optional sense buffer
314  * @timeout:    request timeout in seconds
315  * @retries:    number of times to retry request
316  * @flags:      or into request flags;
317  *
318  * returns the req->errors value which is the the scsi_cmnd result
319  * field.
320  **/
321 int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
322                  int data_direction, void *buffer, unsigned bufflen,
323                  unsigned char *sense, int timeout, int retries, int flags)
324 {
325         struct request *req;
326         int write = (data_direction == DMA_TO_DEVICE);
327         int ret = DRIVER_ERROR << 24;
328
329         req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
330
331         if (bufflen &&  blk_rq_map_kern(sdev->request_queue, req,
332                                         buffer, bufflen, __GFP_WAIT))
333                 goto out;
334
335         req->cmd_len = COMMAND_SIZE(cmd[0]);
336         memcpy(req->cmd, cmd, req->cmd_len);
337         req->sense = sense;
338         req->sense_len = 0;
339         req->timeout = timeout;
340         req->flags |= flags | REQ_BLOCK_PC | REQ_SPECIAL | REQ_QUIET;
341
342         /*
343          * head injection *required* here otherwise quiesce won't work
344          */
345         blk_execute_rq(req->q, NULL, req, 1);
346
347         ret = req->errors;
348  out:
349         blk_put_request(req);
350
351         return ret;
352 }
353 EXPORT_SYMBOL(scsi_execute);
354
355
356 int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
357                      int data_direction, void *buffer, unsigned bufflen,
358                      struct scsi_sense_hdr *sshdr, int timeout, int retries)
359 {
360         char *sense = NULL;
361         int result;
362         
363         if (sshdr) {
364                 sense = kmalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
365                 if (!sense)
366                         return DRIVER_ERROR << 24;
367                 memset(sense, 0, SCSI_SENSE_BUFFERSIZE);
368         }
369         result = scsi_execute(sdev, cmd, data_direction, buffer, bufflen,
370                                   sense, timeout, retries, 0);
371         if (sshdr)
372                 scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, sshdr);
373
374         kfree(sense);
375         return result;
376 }
377 EXPORT_SYMBOL(scsi_execute_req);
378
379 /*
380  * Function:    scsi_init_cmd_errh()
381  *
382  * Purpose:     Initialize cmd fields related to error handling.
383  *
384  * Arguments:   cmd     - command that is ready to be queued.
385  *
386  * Returns:     Nothing
387  *
388  * Notes:       This function has the job of initializing a number of
389  *              fields related to error handling.   Typically this will
390  *              be called once for each command, as required.
391  */
392 static int scsi_init_cmd_errh(struct scsi_cmnd *cmd)
393 {
394         cmd->serial_number = 0;
395
396         memset(cmd->sense_buffer, 0, sizeof cmd->sense_buffer);
397
398         if (cmd->cmd_len == 0)
399                 cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);
400
401         /*
402          * We need saved copies of a number of fields - this is because
403          * error handling may need to overwrite these with different values
404          * to run different commands, and once error handling is complete,
405          * we will need to restore these values prior to running the actual
406          * command.
407          */
408         cmd->old_use_sg = cmd->use_sg;
409         cmd->old_cmd_len = cmd->cmd_len;
410         cmd->sc_old_data_direction = cmd->sc_data_direction;
411         cmd->old_underflow = cmd->underflow;
412         memcpy(cmd->data_cmnd, cmd->cmnd, sizeof(cmd->cmnd));
413         cmd->buffer = cmd->request_buffer;
414         cmd->bufflen = cmd->request_bufflen;
415
416         return 1;
417 }
418
419 /*
420  * Function:   scsi_setup_cmd_retry()
421  *
422  * Purpose:    Restore the command state for a retry
423  *
424  * Arguments:  cmd      - command to be restored
425  *
426  * Returns:    Nothing
427  *
428  * Notes:      Immediately prior to retrying a command, we need
429  *             to restore certain fields that we saved above.
430  */
431 void scsi_setup_cmd_retry(struct scsi_cmnd *cmd)
432 {
433         memcpy(cmd->cmnd, cmd->data_cmnd, sizeof(cmd->data_cmnd));
434         cmd->request_buffer = cmd->buffer;
435         cmd->request_bufflen = cmd->bufflen;
436         cmd->use_sg = cmd->old_use_sg;
437         cmd->cmd_len = cmd->old_cmd_len;
438         cmd->sc_data_direction = cmd->sc_old_data_direction;
439         cmd->underflow = cmd->old_underflow;
440 }
441
442 void scsi_device_unbusy(struct scsi_device *sdev)
443 {
444         struct Scsi_Host *shost = sdev->host;
445         unsigned long flags;
446
447         spin_lock_irqsave(shost->host_lock, flags);
448         shost->host_busy--;
449         if (unlikely(scsi_host_in_recovery(shost) &&
450                      shost->host_failed))
451                 scsi_eh_wakeup(shost);
452         spin_unlock(shost->host_lock);
453         spin_lock(sdev->request_queue->queue_lock);
454         sdev->device_busy--;
455         spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
456 }
457
458 /*
459  * Called for single_lun devices on IO completion. Clear starget_sdev_user,
460  * and call blk_run_queue for all the scsi_devices on the target -
461  * including current_sdev first.
462  *
463  * Called with *no* scsi locks held.
464  */
465 static void scsi_single_lun_run(struct scsi_device *current_sdev)
466 {
467         struct Scsi_Host *shost = current_sdev->host;
468         struct scsi_device *sdev, *tmp;
469         struct scsi_target *starget = scsi_target(current_sdev);
470         unsigned long flags;
471
472         spin_lock_irqsave(shost->host_lock, flags);
473         starget->starget_sdev_user = NULL;
474         spin_unlock_irqrestore(shost->host_lock, flags);
475
476         /*
477          * Call blk_run_queue for all LUNs on the target, starting with
478          * current_sdev. We race with others (to set starget_sdev_user),
479          * but in most cases, we will be first. Ideally, each LU on the
480          * target would get some limited time or requests on the target.
481          */
482         blk_run_queue(current_sdev->request_queue);
483
484         spin_lock_irqsave(shost->host_lock, flags);
485         if (starget->starget_sdev_user)
486                 goto out;
487         list_for_each_entry_safe(sdev, tmp, &starget->devices,
488                         same_target_siblings) {
489                 if (sdev == current_sdev)
490                         continue;
491                 if (scsi_device_get(sdev))
492                         continue;
493
494                 spin_unlock_irqrestore(shost->host_lock, flags);
495                 blk_run_queue(sdev->request_queue);
496                 spin_lock_irqsave(shost->host_lock, flags);
497         
498                 scsi_device_put(sdev);
499         }
500  out:
501         spin_unlock_irqrestore(shost->host_lock, flags);
502 }
503
504 /*
505  * Function:    scsi_run_queue()
506  *
507  * Purpose:     Select a proper request queue to serve next
508  *
509  * Arguments:   q       - last request's queue
510  *
511  * Returns:     Nothing
512  *
513  * Notes:       The previous command was completely finished, start
514  *              a new one if possible.
515  */
516 static void scsi_run_queue(struct request_queue *q)
517 {
518         struct scsi_device *sdev = q->queuedata;
519         struct Scsi_Host *shost = sdev->host;
520         unsigned long flags;
521
522         if (sdev->single_lun)
523                 scsi_single_lun_run(sdev);
524
525         spin_lock_irqsave(shost->host_lock, flags);
526         while (!list_empty(&shost->starved_list) &&
527                !shost->host_blocked && !shost->host_self_blocked &&
528                 !((shost->can_queue > 0) &&
529                   (shost->host_busy >= shost->can_queue))) {
530                 /*
531                  * As long as shost is accepting commands and we have
532                  * starved queues, call blk_run_queue. scsi_request_fn
533                  * drops the queue_lock and can add us back to the
534                  * starved_list.
535                  *
536                  * host_lock protects the starved_list and starved_entry.
537                  * scsi_request_fn must get the host_lock before checking
538                  * or modifying starved_list or starved_entry.
539                  */
540                 sdev = list_entry(shost->starved_list.next,
541                                           struct scsi_device, starved_entry);
542                 list_del_init(&sdev->starved_entry);
543                 spin_unlock_irqrestore(shost->host_lock, flags);
544
545                 blk_run_queue(sdev->request_queue);
546
547                 spin_lock_irqsave(shost->host_lock, flags);
548                 if (unlikely(!list_empty(&sdev->starved_entry)))
549                         /*
550                          * sdev lost a race, and was put back on the
551                          * starved list. This is unlikely but without this
552                          * in theory we could loop forever.
553                          */
554                         break;
555         }
556         spin_unlock_irqrestore(shost->host_lock, flags);
557
558         blk_run_queue(q);
559 }
560
561 /*
562  * Function:    scsi_requeue_command()
563  *
564  * Purpose:     Handle post-processing of completed commands.
565  *
566  * Arguments:   q       - queue to operate on
567  *              cmd     - command that may need to be requeued.
568  *
569  * Returns:     Nothing
570  *
571  * Notes:       After command completion, there may be blocks left
572  *              over which weren't finished by the previous command
573  *              this can be for a number of reasons - the main one is
574  *              I/O errors in the middle of the request, in which case
575  *              we need to request the blocks that come after the bad
576  *              sector.
577  * Notes:       Upon return, cmd is a stale pointer.
578  */
579 static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
580 {
581         struct request *req = cmd->request;
582         unsigned long flags;
583
584         scsi_unprep_request(req);
585         spin_lock_irqsave(q->queue_lock, flags);
586         blk_requeue_request(q, req);
587         spin_unlock_irqrestore(q->queue_lock, flags);
588
589         scsi_run_queue(q);
590 }
591
592 void scsi_next_command(struct scsi_cmnd *cmd)
593 {
594         struct request_queue *q = cmd->device->request_queue;
595
596         scsi_put_command(cmd);
597         scsi_run_queue(q);
598 }
599
600 void scsi_run_host_queues(struct Scsi_Host *shost)
601 {
602         struct scsi_device *sdev;
603
604         shost_for_each_device(sdev, shost)
605                 scsi_run_queue(sdev->request_queue);
606 }
607
608 /*
609  * Function:    scsi_end_request()
610  *
611  * Purpose:     Post-processing of completed commands (usually invoked at end
612  *              of upper level post-processing and scsi_io_completion).
613  *
614  * Arguments:   cmd      - command that is complete.
615  *              uptodate - 1 if I/O indicates success, <= 0 for I/O error.
616  *              bytes    - number of bytes of completed I/O
617  *              requeue  - indicates whether we should requeue leftovers.
618  *
619  * Lock status: Assumed that lock is not held upon entry.
620  *
621  * Returns:     cmd if requeue required, NULL otherwise.
622  *
623  * Notes:       This is called for block device requests in order to
624  *              mark some number of sectors as complete.
625  * 
626  *              We are guaranteeing that the request queue will be goosed
627  *              at some point during this call.
628  * Notes:       If cmd was requeued, upon return it will be a stale pointer.
629  */
630 static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int uptodate,
631                                           int bytes, int requeue)
632 {
633         request_queue_t *q = cmd->device->request_queue;
634         struct request *req = cmd->request;
635         unsigned long flags;
636
637         /*
638          * If there are blocks left over at the end, set up the command
639          * to queue the remainder of them.
640          */
641         if (end_that_request_chunk(req, uptodate, bytes)) {
642                 int leftover = (req->hard_nr_sectors << 9);
643
644                 if (blk_pc_request(req))
645                         leftover = req->data_len;
646
647                 /* kill remainder if no retrys */
648                 if (!uptodate && blk_noretry_request(req))
649                         end_that_request_chunk(req, 0, leftover);
650                 else {
651                         if (requeue) {
652                                 /*
653                                  * Bleah.  Leftovers again.  Stick the
654                                  * leftovers in the front of the
655                                  * queue, and goose the queue again.
656                                  */
657                                 scsi_requeue_command(q, cmd);
658                                 cmd = NULL;
659                         }
660                         return cmd;
661                 }
662         }
663
664         add_disk_randomness(req->rq_disk);
665
666         spin_lock_irqsave(q->queue_lock, flags);
667         if (blk_rq_tagged(req))
668                 blk_queue_end_tag(q, req);
669         end_that_request_last(req);
670         spin_unlock_irqrestore(q->queue_lock, flags);
671
672         /*
673          * This will goose the queue request function at the end, so we don't
674          * need to worry about launching another command.
675          */
676         scsi_next_command(cmd);
677         return NULL;
678 }
679
680 static struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
681 {
682         struct scsi_host_sg_pool *sgp;
683         struct scatterlist *sgl;
684
685         BUG_ON(!cmd->use_sg);
686
687         switch (cmd->use_sg) {
688         case 1 ... 8:
689                 cmd->sglist_len = 0;
690                 break;
691         case 9 ... 16:
692                 cmd->sglist_len = 1;
693                 break;
694         case 17 ... 32:
695                 cmd->sglist_len = 2;
696                 break;
697 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
698         case 33 ... 64:
699                 cmd->sglist_len = 3;
700                 break;
701 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
702         case 65 ... 128:
703                 cmd->sglist_len = 4;
704                 break;
705 #if (SCSI_MAX_PHYS_SEGMENTS  > 128)
706         case 129 ... 256:
707                 cmd->sglist_len = 5;
708                 break;
709 #endif
710 #endif
711 #endif
712         default:
713                 return NULL;
714         }
715
716         sgp = scsi_sg_pools + cmd->sglist_len;
717         sgl = mempool_alloc(sgp->pool, gfp_mask);
718         return sgl;
719 }
720
721 static void scsi_free_sgtable(struct scatterlist *sgl, int index)
722 {
723         struct scsi_host_sg_pool *sgp;
724
725         BUG_ON(index >= SG_MEMPOOL_NR);
726
727         sgp = scsi_sg_pools + index;
728         mempool_free(sgl, sgp->pool);
729 }
730
731 /*
732  * Function:    scsi_release_buffers()
733  *
734  * Purpose:     Completion processing for block device I/O requests.
735  *
736  * Arguments:   cmd     - command that we are bailing.
737  *
738  * Lock status: Assumed that no lock is held upon entry.
739  *
740  * Returns:     Nothing
741  *
742  * Notes:       In the event that an upper level driver rejects a
743  *              command, we must release resources allocated during
744  *              the __init_io() function.  Primarily this would involve
745  *              the scatter-gather table, and potentially any bounce
746  *              buffers.
747  */
748 static void scsi_release_buffers(struct scsi_cmnd *cmd)
749 {
750         struct request *req = cmd->request;
751
752         /*
753          * Free up any indirection buffers we allocated for DMA purposes. 
754          */
755         if (cmd->use_sg)
756                 scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
757         else if (cmd->request_buffer != req->buffer)
758                 kfree(cmd->request_buffer);
759
760         /*
761          * Zero these out.  They now point to freed memory, and it is
762          * dangerous to hang onto the pointers.
763          */
764         cmd->buffer  = NULL;
765         cmd->bufflen = 0;
766         cmd->request_buffer = NULL;
767         cmd->request_bufflen = 0;
768 }
769
770 /*
771  * Function:    scsi_io_completion()
772  *
773  * Purpose:     Completion processing for block device I/O requests.
774  *
775  * Arguments:   cmd   - command that is finished.
776  *
777  * Lock status: Assumed that no lock is held upon entry.
778  *
779  * Returns:     Nothing
780  *
781  * Notes:       This function is matched in terms of capabilities to
782  *              the function that created the scatter-gather list.
783  *              In other words, if there are no bounce buffers
784  *              (the normal case for most drivers), we don't need
785  *              the logic to deal with cleaning up afterwards.
786  *
787  *              We must do one of several things here:
788  *
789  *              a) Call scsi_end_request.  This will finish off the
790  *                 specified number of sectors.  If we are done, the
791  *                 command block will be released, and the queue
792  *                 function will be goosed.  If we are not done, then
793  *                 scsi_end_request will directly goose the queue.
794  *
795  *              b) We can just use scsi_requeue_command() here.  This would
796  *                 be used if we just wanted to retry, for example.
797  */
798 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
799                         unsigned int block_bytes)
800 {
801         int result = cmd->result;
802         int this_count = cmd->bufflen;
803         request_queue_t *q = cmd->device->request_queue;
804         struct request *req = cmd->request;
805         int clear_errors = 1;
806         struct scsi_sense_hdr sshdr;
807         int sense_valid = 0;
808         int sense_deferred = 0;
809
810         if (blk_complete_barrier_rq(q, req, good_bytes >> 9))
811                 return;
812
813         /*
814          * Free up any indirection buffers we allocated for DMA purposes. 
815          * For the case of a READ, we need to copy the data out of the
816          * bounce buffer and into the real buffer.
817          */
818         if (cmd->use_sg)
819                 scsi_free_sgtable(cmd->buffer, cmd->sglist_len);
820         else if (cmd->buffer != req->buffer) {
821                 if (rq_data_dir(req) == READ) {
822                         unsigned long flags;
823                         char *to = bio_kmap_irq(req->bio, &flags);
824                         memcpy(to, cmd->buffer, cmd->bufflen);
825                         bio_kunmap_irq(to, &flags);
826                 }
827                 kfree(cmd->buffer);
828         }
829
830         if (result) {
831                 sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
832                 if (sense_valid)
833                         sense_deferred = scsi_sense_is_deferred(&sshdr);
834         }
835         if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
836                 req->errors = result;
837                 if (result) {
838                         clear_errors = 0;
839                         if (sense_valid && req->sense) {
840                                 /*
841                                  * SG_IO wants current and deferred errors
842                                  */
843                                 int len = 8 + cmd->sense_buffer[7];
844
845                                 if (len > SCSI_SENSE_BUFFERSIZE)
846                                         len = SCSI_SENSE_BUFFERSIZE;
847                                 memcpy(req->sense, cmd->sense_buffer,  len);
848                                 req->sense_len = len;
849                         }
850                 } else
851                         req->data_len = cmd->resid;
852         }
853
854         /*
855          * Zero these out.  They now point to freed memory, and it is
856          * dangerous to hang onto the pointers.
857          */
858         cmd->buffer  = NULL;
859         cmd->bufflen = 0;
860         cmd->request_buffer = NULL;
861         cmd->request_bufflen = 0;
862
863         /*
864          * Next deal with any sectors which we were able to correctly
865          * handle.
866          */
867         if (good_bytes >= 0) {
868                 SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, %d bytes done.\n",
869                                               req->nr_sectors, good_bytes));
870                 SCSI_LOG_HLCOMPLETE(1, printk("use_sg is %d\n", cmd->use_sg));
871
872                 if (clear_errors)
873                         req->errors = 0;
874                 /*
875                  * If multiple sectors are requested in one buffer, then
876                  * they will have been finished off by the first command.
877                  * If not, then we have a multi-buffer command.
878                  *
879                  * If block_bytes != 0, it means we had a medium error
880                  * of some sort, and that we want to mark some number of
881                  * sectors as not uptodate.  Thus we want to inhibit
882                  * requeueing right here - we will requeue down below
883                  * when we handle the bad sectors.
884                  */
885
886                 /*
887                  * If the command completed without error, then either
888                  * finish off the rest of the command, or start a new one.
889                  */
890                 if (scsi_end_request(cmd, 1, good_bytes, result == 0) == NULL)
891                         return;
892         }
893         /*
894          * Now, if we were good little boys and girls, Santa left us a request
895          * sense buffer.  We can extract information from this, so we
896          * can choose a block to remap, etc.
897          */
898         if (sense_valid && !sense_deferred) {
899                 switch (sshdr.sense_key) {
900                 case UNIT_ATTENTION:
901                         if (cmd->device->removable) {
902                                 /* detected disc change.  set a bit 
903                                  * and quietly refuse further access.
904                                  */
905                                 cmd->device->changed = 1;
906                                 scsi_end_request(cmd, 0,
907                                                 this_count, 1);
908                                 return;
909                         } else {
910                                 /*
911                                 * Must have been a power glitch, or a
912                                 * bus reset.  Could not have been a
913                                 * media change, so we just retry the
914                                 * request and see what happens.  
915                                 */
916                                 scsi_requeue_command(q, cmd);
917                                 return;
918                         }
919                         break;
920                 case ILLEGAL_REQUEST:
921                         /*
922                         * If we had an ILLEGAL REQUEST returned, then we may
923                         * have performed an unsupported command.  The only
924                         * thing this should be would be a ten byte read where
925                         * only a six byte read was supported.  Also, on a
926                         * system where READ CAPACITY failed, we may have read
927                         * past the end of the disk.
928                         */
929                         if (cmd->device->use_10_for_rw &&
930                             (cmd->cmnd[0] == READ_10 ||
931                              cmd->cmnd[0] == WRITE_10)) {
932                                 cmd->device->use_10_for_rw = 0;
933                                 /*
934                                  * This will cause a retry with a 6-byte
935                                  * command.
936                                  */
937                                 scsi_requeue_command(q, cmd);
938                                 result = 0;
939                         } else {
940                                 scsi_end_request(cmd, 0, this_count, 1);
941                                 return;
942                         }
943                         break;
944                 case NOT_READY:
945                         /*
946                          * If the device is in the process of becoming ready,
947                          * retry.
948                          */
949                         if (sshdr.asc == 0x04 && sshdr.ascq == 0x01) {
950                                 scsi_requeue_command(q, cmd);
951                                 return;
952                         }
953                         if (!(req->flags & REQ_QUIET))
954                                 dev_printk(KERN_INFO,
955                                            &cmd->device->sdev_gendev,
956                                            "Device not ready.\n");
957                         scsi_end_request(cmd, 0, this_count, 1);
958                         return;
959                 case VOLUME_OVERFLOW:
960                         if (!(req->flags & REQ_QUIET)) {
961                                 dev_printk(KERN_INFO,
962                                            &cmd->device->sdev_gendev,
963                                            "Volume overflow, CDB: ");
964                                 __scsi_print_command(cmd->data_cmnd);
965                                 scsi_print_sense("", cmd);
966                         }
967                         scsi_end_request(cmd, 0, block_bytes, 1);
968                         return;
969                 default:
970                         break;
971                 }
972         }                       /* driver byte != 0 */
973         if (host_byte(result) == DID_RESET) {
974                 /*
975                  * Third party bus reset or reset for error
976                  * recovery reasons.  Just retry the request
977                  * and see what happens.  
978                  */
979                 scsi_requeue_command(q, cmd);
980                 return;
981         }
982         if (result) {
983                 if (!(req->flags & REQ_QUIET)) {
984                         dev_printk(KERN_INFO, &cmd->device->sdev_gendev,
985                                    "SCSI error: return code = 0x%x\n", result);
986
987                         if (driver_byte(result) & DRIVER_SENSE)
988                                 scsi_print_sense("", cmd);
989                 }
990                 /*
991                  * Mark a single buffer as not uptodate.  Queue the remainder.
992                  * We sometimes get this cruft in the event that a medium error
993                  * isn't properly reported.
994                  */
995                 block_bytes = req->hard_cur_sectors << 9;
996                 if (!block_bytes)
997                         block_bytes = req->data_len;
998                 scsi_end_request(cmd, 0, block_bytes, 1);
999         }
1000 }
1001 EXPORT_SYMBOL(scsi_io_completion);
1002
1003 /*
1004  * Function:    scsi_init_io()
1005  *
1006  * Purpose:     SCSI I/O initialize function.
1007  *
1008  * Arguments:   cmd   - Command descriptor we wish to initialize
1009  *
1010  * Returns:     0 on success
1011  *              BLKPREP_DEFER if the failure is retryable
1012  *              BLKPREP_KILL if the failure is fatal
1013  */
1014 static int scsi_init_io(struct scsi_cmnd *cmd)
1015 {
1016         struct request     *req = cmd->request;
1017         struct scatterlist *sgpnt;
1018         int                count;
1019
1020         /*
1021          * if this is a rq->data based REQ_BLOCK_PC, setup for a non-sg xfer
1022          */
1023         if ((req->flags & REQ_BLOCK_PC) && !req->bio) {
1024                 cmd->request_bufflen = req->data_len;
1025                 cmd->request_buffer = req->data;
1026                 req->buffer = req->data;
1027                 cmd->use_sg = 0;
1028                 return 0;
1029         }
1030
1031         /*
1032          * we used to not use scatter-gather for single segment request,
1033          * but now we do (it makes highmem I/O easier to support without
1034          * kmapping pages)
1035          */
1036         cmd->use_sg = req->nr_phys_segments;
1037
1038         /*
1039          * if sg table allocation fails, requeue request later.
1040          */
1041         sgpnt = scsi_alloc_sgtable(cmd, GFP_ATOMIC);
1042         if (unlikely(!sgpnt)) {
1043                 scsi_unprep_request(req);
1044                 return BLKPREP_DEFER;
1045         }
1046
1047         cmd->request_buffer = (char *) sgpnt;
1048         cmd->request_bufflen = req->nr_sectors << 9;
1049         if (blk_pc_request(req))
1050                 cmd->request_bufflen = req->data_len;
1051         req->buffer = NULL;
1052
1053         /* 
1054          * Next, walk the list, and fill in the addresses and sizes of
1055          * each segment.
1056          */
1057         count = blk_rq_map_sg(req->q, req, cmd->request_buffer);
1058
1059         /*
1060          * mapped well, send it off
1061          */
1062         if (likely(count <= cmd->use_sg)) {
1063                 cmd->use_sg = count;
1064                 return 0;
1065         }
1066
1067         printk(KERN_ERR "Incorrect number of segments after building list\n");
1068         printk(KERN_ERR "counted %d, received %d\n", count, cmd->use_sg);
1069         printk(KERN_ERR "req nr_sec %lu, cur_nr_sec %u\n", req->nr_sectors,
1070                         req->current_nr_sectors);
1071
1072         /* release the command and kill it */
1073         scsi_release_buffers(cmd);
1074         scsi_put_command(cmd);
1075         return BLKPREP_KILL;
1076 }
1077
1078 static int scsi_prepare_flush_fn(request_queue_t *q, struct request *rq)
1079 {
1080         struct scsi_device *sdev = q->queuedata;
1081         struct scsi_driver *drv;
1082
1083         if (sdev->sdev_state == SDEV_RUNNING) {
1084                 drv = *(struct scsi_driver **) rq->rq_disk->private_data;
1085
1086                 if (drv->prepare_flush)
1087                         return drv->prepare_flush(q, rq);
1088         }
1089
1090         return 0;
1091 }
1092
1093 static void scsi_end_flush_fn(request_queue_t *q, struct request *rq)
1094 {
1095         struct scsi_device *sdev = q->queuedata;
1096         struct request *flush_rq = rq->end_io_data;
1097         struct scsi_driver *drv;
1098
1099         if (flush_rq->errors) {
1100                 printk("scsi: barrier error, disabling flush support\n");
1101                 blk_queue_ordered(q, QUEUE_ORDERED_NONE);
1102         }
1103
1104         if (sdev->sdev_state == SDEV_RUNNING) {
1105                 drv = *(struct scsi_driver **) rq->rq_disk->private_data;
1106                 drv->end_flush(q, rq);
1107         }
1108 }
1109
1110 static int scsi_issue_flush_fn(request_queue_t *q, struct gendisk *disk,
1111                                sector_t *error_sector)
1112 {
1113         struct scsi_device *sdev = q->queuedata;
1114         struct scsi_driver *drv;
1115
1116         if (sdev->sdev_state != SDEV_RUNNING)
1117                 return -ENXIO;
1118
1119         drv = *(struct scsi_driver **) disk->private_data;
1120         if (drv->issue_flush)
1121                 return drv->issue_flush(&sdev->sdev_gendev, error_sector);
1122
1123         return -EOPNOTSUPP;
1124 }
1125
1126 static void scsi_generic_done(struct scsi_cmnd *cmd)
1127 {
1128         BUG_ON(!blk_pc_request(cmd->request));
1129         scsi_io_completion(cmd, cmd->result == 0 ? cmd->bufflen : 0, 0);
1130 }
1131
1132 static int scsi_prep_fn(struct request_queue *q, struct request *req)
1133 {
1134         struct scsi_device *sdev = q->queuedata;
1135         struct scsi_cmnd *cmd;
1136         int specials_only = 0;
1137
1138         /*
1139          * Just check to see if the device is online.  If it isn't, we
1140          * refuse to process any commands.  The device must be brought
1141          * online before trying any recovery commands
1142          */
1143         if (unlikely(!scsi_device_online(sdev))) {
1144                 printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to offline device\n",
1145                        sdev->host->host_no, sdev->id, sdev->lun);
1146                 goto kill;
1147         }
1148         if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
1149                 /* OK, we're not in a running state don't prep
1150                  * user commands */
1151                 if (sdev->sdev_state == SDEV_DEL) {
1152                         /* Device is fully deleted, no commands
1153                          * at all allowed down */
1154                         printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to dead device\n",
1155                                sdev->host->host_no, sdev->id, sdev->lun);
1156                         goto kill;
1157                 }
1158                 /* OK, we only allow special commands (i.e. not
1159                  * user initiated ones */
1160                 specials_only = sdev->sdev_state;
1161         }
1162
1163         /*
1164          * Find the actual device driver associated with this command.
1165          * The SPECIAL requests are things like character device or
1166          * ioctls, which did not originate from ll_rw_blk.  Note that
1167          * the special field is also used to indicate the cmd for
1168          * the remainder of a partially fulfilled request that can 
1169          * come up when there is a medium error.  We have to treat
1170          * these two cases differently.  We differentiate by looking
1171          * at request->cmd, as this tells us the real story.
1172          */
1173         if (req->flags & REQ_SPECIAL && req->special) {
1174                 struct scsi_request *sreq = req->special;
1175
1176                 if (sreq->sr_magic == SCSI_REQ_MAGIC) {
1177                         cmd = scsi_get_command(sreq->sr_device, GFP_ATOMIC);
1178                         if (unlikely(!cmd))
1179                                 goto defer;
1180                         scsi_init_cmd_from_req(cmd, sreq);
1181                 } else
1182                         cmd = req->special;
1183         } else if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1184
1185                 if(unlikely(specials_only) && !(req->flags & REQ_SPECIAL)) {
1186                         if(specials_only == SDEV_QUIESCE ||
1187                                         specials_only == SDEV_BLOCK)
1188                                 goto defer;
1189                         
1190                         printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to device being removed\n",
1191                                sdev->host->host_no, sdev->id, sdev->lun);
1192                         goto kill;
1193                 }
1194                         
1195                         
1196                 /*
1197                  * Now try and find a command block that we can use.
1198                  */
1199                 if (!req->special) {
1200                         cmd = scsi_get_command(sdev, GFP_ATOMIC);
1201                         if (unlikely(!cmd))
1202                                 goto defer;
1203                 } else
1204                         cmd = req->special;
1205                 
1206                 /* pull a tag out of the request if we have one */
1207                 cmd->tag = req->tag;
1208         } else {
1209                 blk_dump_rq_flags(req, "SCSI bad req");
1210                 goto kill;
1211         }
1212         
1213         /* note the overloading of req->special.  When the tag
1214          * is active it always means cmd.  If the tag goes
1215          * back for re-queueing, it may be reset */
1216         req->special = cmd;
1217         cmd->request = req;
1218         
1219         /*
1220          * FIXME: drop the lock here because the functions below
1221          * expect to be called without the queue lock held.  Also,
1222          * previously, we dequeued the request before dropping the
1223          * lock.  We hope REQ_STARTED prevents anything untoward from
1224          * happening now.
1225          */
1226         if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1227                 struct scsi_driver *drv;
1228                 int ret;
1229
1230                 /*
1231                  * This will do a couple of things:
1232                  *  1) Fill in the actual SCSI command.
1233                  *  2) Fill in any other upper-level specific fields
1234                  * (timeout).
1235                  *
1236                  * If this returns 0, it means that the request failed
1237                  * (reading past end of disk, reading offline device,
1238                  * etc).   This won't actually talk to the device, but
1239                  * some kinds of consistency checking may cause the     
1240                  * request to be rejected immediately.
1241                  */
1242
1243                 /* 
1244                  * This sets up the scatter-gather table (allocating if
1245                  * required).
1246                  */
1247                 ret = scsi_init_io(cmd);
1248                 switch(ret) {
1249                         /* For BLKPREP_KILL/DEFER the cmd was released */
1250                 case BLKPREP_KILL:
1251                         goto kill;
1252                 case BLKPREP_DEFER:
1253                         goto defer;
1254                 }
1255                 
1256                 /*
1257                  * Initialize the actual SCSI command for this request.
1258                  */
1259                 if (req->rq_disk) {
1260                         drv = *(struct scsi_driver **)req->rq_disk->private_data;
1261                         if (unlikely(!drv->init_command(cmd))) {
1262                                 scsi_release_buffers(cmd);
1263                                 scsi_put_command(cmd);
1264                                 goto kill;
1265                         }
1266                 } else {
1267                         memcpy(cmd->cmnd, req->cmd, sizeof(cmd->cmnd));
1268                         cmd->cmd_len = req->cmd_len;
1269                         if (rq_data_dir(req) == WRITE)
1270                                 cmd->sc_data_direction = DMA_TO_DEVICE;
1271                         else if (req->data_len)
1272                                 cmd->sc_data_direction = DMA_FROM_DEVICE;
1273                         else
1274                                 cmd->sc_data_direction = DMA_NONE;
1275                         
1276                         cmd->transfersize = req->data_len;
1277                         cmd->allowed = 3;
1278                         cmd->timeout_per_command = req->timeout;
1279                         cmd->done = scsi_generic_done;
1280                 }
1281         }
1282
1283         /*
1284          * The request is now prepped, no need to come back here
1285          */
1286         req->flags |= REQ_DONTPREP;
1287         return BLKPREP_OK;
1288
1289  defer:
1290         /* If we defer, the elv_next_request() returns NULL, but the
1291          * queue must be restarted, so we plug here if no returning
1292          * command will automatically do that. */
1293         if (sdev->device_busy == 0)
1294                 blk_plug_device(q);
1295         return BLKPREP_DEFER;
1296  kill:
1297         req->errors = DID_NO_CONNECT << 16;
1298         return BLKPREP_KILL;
1299 }
1300
1301 /*
1302  * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1303  * return 0.
1304  *
1305  * Called with the queue_lock held.
1306  */
1307 static inline int scsi_dev_queue_ready(struct request_queue *q,
1308                                   struct scsi_device *sdev)
1309 {
1310         if (sdev->device_busy >= sdev->queue_depth)
1311                 return 0;
1312         if (sdev->device_busy == 0 && sdev->device_blocked) {
1313                 /*
1314                  * unblock after device_blocked iterates to zero
1315                  */
1316                 if (--sdev->device_blocked == 0) {
1317                         SCSI_LOG_MLQUEUE(3,
1318                                 printk("scsi%d (%d:%d) unblocking device at"
1319                                        " zero depth\n", sdev->host->host_no,
1320                                        sdev->id, sdev->lun));
1321                 } else {
1322                         blk_plug_device(q);
1323                         return 0;
1324                 }
1325         }
1326         if (sdev->device_blocked)
1327                 return 0;
1328
1329         return 1;
1330 }
1331
1332 /*
1333  * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1334  * return 0. We must end up running the queue again whenever 0 is
1335  * returned, else IO can hang.
1336  *
1337  * Called with host_lock held.
1338  */
1339 static inline int scsi_host_queue_ready(struct request_queue *q,
1340                                    struct Scsi_Host *shost,
1341                                    struct scsi_device *sdev)
1342 {
1343         if (scsi_host_in_recovery(shost))
1344                 return 0;
1345         if (shost->host_busy == 0 && shost->host_blocked) {
1346                 /*
1347                  * unblock after host_blocked iterates to zero
1348                  */
1349                 if (--shost->host_blocked == 0) {
1350                         SCSI_LOG_MLQUEUE(3,
1351                                 printk("scsi%d unblocking host at zero depth\n",
1352                                         shost->host_no));
1353                 } else {
1354                         blk_plug_device(q);
1355                         return 0;
1356                 }
1357         }
1358         if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
1359             shost->host_blocked || shost->host_self_blocked) {
1360                 if (list_empty(&sdev->starved_entry))
1361                         list_add_tail(&sdev->starved_entry, &shost->starved_list);
1362                 return 0;
1363         }
1364
1365         /* We're OK to process the command, so we can't be starved */
1366         if (!list_empty(&sdev->starved_entry))
1367                 list_del_init(&sdev->starved_entry);
1368
1369         return 1;
1370 }
1371
1372 /*
1373  * Kill a request for a dead device
1374  */
1375 static void scsi_kill_request(struct request *req, request_queue_t *q)
1376 {
1377         struct scsi_cmnd *cmd = req->special;
1378
1379         blkdev_dequeue_request(req);
1380
1381         if (unlikely(cmd == NULL)) {
1382                 printk(KERN_CRIT "impossible request in %s.\n",
1383                                  __FUNCTION__);
1384                 BUG();
1385         }
1386
1387         scsi_init_cmd_errh(cmd);
1388         cmd->result = DID_NO_CONNECT << 16;
1389         atomic_inc(&cmd->device->iorequest_cnt);
1390         __scsi_done(cmd);
1391 }
1392
1393 /*
1394  * Function:    scsi_request_fn()
1395  *
1396  * Purpose:     Main strategy routine for SCSI.
1397  *
1398  * Arguments:   q       - Pointer to actual queue.
1399  *
1400  * Returns:     Nothing
1401  *
1402  * Lock status: IO request lock assumed to be held when called.
1403  */
1404 static void scsi_request_fn(struct request_queue *q)
1405 {
1406         struct scsi_device *sdev = q->queuedata;
1407         struct Scsi_Host *shost;
1408         struct scsi_cmnd *cmd;
1409         struct request *req;
1410
1411         if (!sdev) {
1412                 printk("scsi: killing requests for dead queue\n");
1413                 while ((req = elv_next_request(q)) != NULL)
1414                         scsi_kill_request(req, q);
1415                 return;
1416         }
1417
1418         if(!get_device(&sdev->sdev_gendev))
1419                 /* We must be tearing the block queue down already */
1420                 return;
1421
1422         /*
1423          * To start with, we keep looping until the queue is empty, or until
1424          * the host is no longer able to accept any more requests.
1425          */
1426         shost = sdev->host;
1427         while (!blk_queue_plugged(q)) {
1428                 int rtn;
1429                 /*
1430                  * get next queueable request.  We do this early to make sure
1431                  * that the request is fully prepared even if we cannot 
1432                  * accept it.
1433                  */
1434                 req = elv_next_request(q);
1435                 if (!req || !scsi_dev_queue_ready(q, sdev))
1436                         break;
1437
1438                 if (unlikely(!scsi_device_online(sdev))) {
1439                         printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to offline device\n",
1440                                sdev->host->host_no, sdev->id, sdev->lun);
1441                         scsi_kill_request(req, q);
1442                         continue;
1443                 }
1444
1445
1446                 /*
1447                  * Remove the request from the request list.
1448                  */
1449                 if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1450                         blkdev_dequeue_request(req);
1451                 sdev->device_busy++;
1452
1453                 spin_unlock(q->queue_lock);
1454                 cmd = req->special;
1455                 if (unlikely(cmd == NULL)) {
1456                         printk(KERN_CRIT "impossible request in %s.\n"
1457                                          "please mail a stack trace to "
1458                                          "linux-scsi@vger.kernel.org",
1459                                          __FUNCTION__);
1460                         BUG();
1461                 }
1462                 spin_lock(shost->host_lock);
1463
1464                 if (!scsi_host_queue_ready(q, shost, sdev))
1465                         goto not_ready;
1466                 if (sdev->single_lun) {
1467                         if (scsi_target(sdev)->starget_sdev_user &&
1468                             scsi_target(sdev)->starget_sdev_user != sdev)
1469                                 goto not_ready;
1470                         scsi_target(sdev)->starget_sdev_user = sdev;
1471                 }
1472                 shost->host_busy++;
1473
1474                 /*
1475                  * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1476                  *              take the lock again.
1477                  */
1478                 spin_unlock_irq(shost->host_lock);
1479
1480                 /*
1481                  * Finally, initialize any error handling parameters, and set up
1482                  * the timers for timeouts.
1483                  */
1484                 scsi_init_cmd_errh(cmd);
1485
1486                 /*
1487                  * Dispatch the command to the low-level driver.
1488                  */
1489                 rtn = scsi_dispatch_cmd(cmd);
1490                 spin_lock_irq(q->queue_lock);
1491                 if(rtn) {
1492                         /* we're refusing the command; because of
1493                          * the way locks get dropped, we need to 
1494                          * check here if plugging is required */
1495                         if(sdev->device_busy == 0)
1496                                 blk_plug_device(q);
1497
1498                         break;
1499                 }
1500         }
1501
1502         goto out;
1503
1504  not_ready:
1505         spin_unlock_irq(shost->host_lock);
1506
1507         /*
1508          * lock q, handle tag, requeue req, and decrement device_busy. We
1509          * must return with queue_lock held.
1510          *
1511          * Decrementing device_busy without checking it is OK, as all such
1512          * cases (host limits or settings) should run the queue at some
1513          * later time.
1514          */
1515         spin_lock_irq(q->queue_lock);
1516         blk_requeue_request(q, req);
1517         sdev->device_busy--;
1518         if(sdev->device_busy == 0)
1519                 blk_plug_device(q);
1520  out:
1521         /* must be careful here...if we trigger the ->remove() function
1522          * we cannot be holding the q lock */
1523         spin_unlock_irq(q->queue_lock);
1524         put_device(&sdev->sdev_gendev);
1525         spin_lock_irq(q->queue_lock);
1526 }
1527
1528 u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1529 {
1530         struct device *host_dev;
1531         u64 bounce_limit = 0xffffffff;
1532
1533         if (shost->unchecked_isa_dma)
1534                 return BLK_BOUNCE_ISA;
1535         /*
1536          * Platforms with virtual-DMA translation
1537          * hardware have no practical limit.
1538          */
1539         if (!PCI_DMA_BUS_IS_PHYS)
1540                 return BLK_BOUNCE_ANY;
1541
1542         host_dev = scsi_get_device(shost);
1543         if (host_dev && host_dev->dma_mask)
1544                 bounce_limit = *host_dev->dma_mask;
1545
1546         return bounce_limit;
1547 }
1548 EXPORT_SYMBOL(scsi_calculate_bounce_limit);
1549
1550 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1551 {
1552         struct Scsi_Host *shost = sdev->host;
1553         struct request_queue *q;
1554
1555         q = blk_init_queue(scsi_request_fn, NULL);
1556         if (!q)
1557                 return NULL;
1558
1559         blk_queue_prep_rq(q, scsi_prep_fn);
1560
1561         blk_queue_max_hw_segments(q, shost->sg_tablesize);
1562         blk_queue_max_phys_segments(q, SCSI_MAX_PHYS_SEGMENTS);
1563         blk_queue_max_sectors(q, shost->max_sectors);
1564         blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1565         blk_queue_segment_boundary(q, shost->dma_boundary);
1566         blk_queue_issue_flush_fn(q, scsi_issue_flush_fn);
1567
1568         /*
1569          * ordered tags are superior to flush ordering
1570          */
1571         if (shost->ordered_tag)
1572                 blk_queue_ordered(q, QUEUE_ORDERED_TAG);
1573         else if (shost->ordered_flush) {
1574                 blk_queue_ordered(q, QUEUE_ORDERED_FLUSH);
1575                 q->prepare_flush_fn = scsi_prepare_flush_fn;
1576                 q->end_flush_fn = scsi_end_flush_fn;
1577         }
1578
1579         if (!shost->use_clustering)
1580                 clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
1581         return q;
1582 }
1583
1584 void scsi_free_queue(struct request_queue *q)
1585 {
1586         blk_cleanup_queue(q);
1587 }
1588
1589 /*
1590  * Function:    scsi_block_requests()
1591  *
1592  * Purpose:     Utility function used by low-level drivers to prevent further
1593  *              commands from being queued to the device.
1594  *
1595  * Arguments:   shost       - Host in question
1596  *
1597  * Returns:     Nothing
1598  *
1599  * Lock status: No locks are assumed held.
1600  *
1601  * Notes:       There is no timer nor any other means by which the requests
1602  *              get unblocked other than the low-level driver calling
1603  *              scsi_unblock_requests().
1604  */
1605 void scsi_block_requests(struct Scsi_Host *shost)
1606 {
1607         shost->host_self_blocked = 1;
1608 }
1609 EXPORT_SYMBOL(scsi_block_requests);
1610
1611 /*
1612  * Function:    scsi_unblock_requests()
1613  *
1614  * Purpose:     Utility function used by low-level drivers to allow further
1615  *              commands from being queued to the device.
1616  *
1617  * Arguments:   shost       - Host in question
1618  *
1619  * Returns:     Nothing
1620  *
1621  * Lock status: No locks are assumed held.
1622  *
1623  * Notes:       There is no timer nor any other means by which the requests
1624  *              get unblocked other than the low-level driver calling
1625  *              scsi_unblock_requests().
1626  *
1627  *              This is done as an API function so that changes to the
1628  *              internals of the scsi mid-layer won't require wholesale
1629  *              changes to drivers that use this feature.
1630  */
1631 void scsi_unblock_requests(struct Scsi_Host *shost)
1632 {
1633         shost->host_self_blocked = 0;
1634         scsi_run_host_queues(shost);
1635 }
1636 EXPORT_SYMBOL(scsi_unblock_requests);
1637
1638 int __init scsi_init_queue(void)
1639 {
1640         int i;
1641
1642         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1643                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1644                 int size = sgp->size * sizeof(struct scatterlist);
1645
1646                 sgp->slab = kmem_cache_create(sgp->name, size, 0,
1647                                 SLAB_HWCACHE_ALIGN, NULL, NULL);
1648                 if (!sgp->slab) {
1649                         printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1650                                         sgp->name);
1651                 }
1652
1653                 sgp->pool = mempool_create(SG_MEMPOOL_SIZE,
1654                                 mempool_alloc_slab, mempool_free_slab,
1655                                 sgp->slab);
1656                 if (!sgp->pool) {
1657                         printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1658                                         sgp->name);
1659                 }
1660         }
1661
1662         return 0;
1663 }
1664
1665 void scsi_exit_queue(void)
1666 {
1667         int i;
1668
1669         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1670                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1671                 mempool_destroy(sgp->pool);
1672                 kmem_cache_destroy(sgp->slab);
1673         }
1674 }
1675 /**
1676  *      scsi_mode_sense - issue a mode sense, falling back from 10 to 
1677  *              six bytes if necessary.
1678  *      @sdev:  SCSI device to be queried
1679  *      @dbd:   set if mode sense will allow block descriptors to be returned
1680  *      @modepage: mode page being requested
1681  *      @buffer: request buffer (may not be smaller than eight bytes)
1682  *      @len:   length of request buffer.
1683  *      @timeout: command timeout
1684  *      @retries: number of retries before failing
1685  *      @data: returns a structure abstracting the mode header data
1686  *      @sense: place to put sense data (or NULL if no sense to be collected).
1687  *              must be SCSI_SENSE_BUFFERSIZE big.
1688  *
1689  *      Returns zero if unsuccessful, or the header offset (either 4
1690  *      or 8 depending on whether a six or ten byte command was
1691  *      issued) if successful.
1692  **/
1693 int
1694 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
1695                   unsigned char *buffer, int len, int timeout, int retries,
1696                   struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr) {
1697         unsigned char cmd[12];
1698         int use_10_for_ms;
1699         int header_length;
1700         int result;
1701         struct scsi_sense_hdr my_sshdr;
1702
1703         memset(data, 0, sizeof(*data));
1704         memset(&cmd[0], 0, 12);
1705         cmd[1] = dbd & 0x18;    /* allows DBD and LLBA bits */
1706         cmd[2] = modepage;
1707
1708         /* caller might not be interested in sense, but we need it */
1709         if (!sshdr)
1710                 sshdr = &my_sshdr;
1711
1712  retry:
1713         use_10_for_ms = sdev->use_10_for_ms;
1714
1715         if (use_10_for_ms) {
1716                 if (len < 8)
1717                         len = 8;
1718
1719                 cmd[0] = MODE_SENSE_10;
1720                 cmd[8] = len;
1721                 header_length = 8;
1722         } else {
1723                 if (len < 4)
1724                         len = 4;
1725
1726                 cmd[0] = MODE_SENSE;
1727                 cmd[4] = len;
1728                 header_length = 4;
1729         }
1730
1731         memset(buffer, 0, len);
1732
1733         result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
1734                                   sshdr, timeout, retries);
1735
1736         /* This code looks awful: what it's doing is making sure an
1737          * ILLEGAL REQUEST sense return identifies the actual command
1738          * byte as the problem.  MODE_SENSE commands can return
1739          * ILLEGAL REQUEST if the code page isn't supported */
1740
1741         if (use_10_for_ms && !scsi_status_is_good(result) &&
1742             (driver_byte(result) & DRIVER_SENSE)) {
1743                 if (scsi_sense_valid(sshdr)) {
1744                         if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
1745                             (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
1746                                 /* 
1747                                  * Invalid command operation code
1748                                  */
1749                                 sdev->use_10_for_ms = 0;
1750                                 goto retry;
1751                         }
1752                 }
1753         }
1754
1755         if(scsi_status_is_good(result)) {
1756                 data->header_length = header_length;
1757                 if(use_10_for_ms) {
1758                         data->length = buffer[0]*256 + buffer[1] + 2;
1759                         data->medium_type = buffer[2];
1760                         data->device_specific = buffer[3];
1761                         data->longlba = buffer[4] & 0x01;
1762                         data->block_descriptor_length = buffer[6]*256
1763                                 + buffer[7];
1764                 } else {
1765                         data->length = buffer[0] + 1;
1766                         data->medium_type = buffer[1];
1767                         data->device_specific = buffer[2];
1768                         data->block_descriptor_length = buffer[3];
1769                 }
1770         }
1771
1772         return result;
1773 }
1774 EXPORT_SYMBOL(scsi_mode_sense);
1775
1776 int
1777 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries)
1778 {
1779         char cmd[] = {
1780                 TEST_UNIT_READY, 0, 0, 0, 0, 0,
1781         };
1782         struct scsi_sense_hdr sshdr;
1783         int result;
1784         
1785         result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, &sshdr,
1786                                   timeout, retries);
1787
1788         if ((driver_byte(result) & DRIVER_SENSE) && sdev->removable) {
1789
1790                 if ((scsi_sense_valid(&sshdr)) &&
1791                     ((sshdr.sense_key == UNIT_ATTENTION) ||
1792                      (sshdr.sense_key == NOT_READY))) {
1793                         sdev->changed = 1;
1794                         result = 0;
1795                 }
1796         }
1797         return result;
1798 }
1799 EXPORT_SYMBOL(scsi_test_unit_ready);
1800
1801 /**
1802  *      scsi_device_set_state - Take the given device through the device
1803  *              state model.
1804  *      @sdev:  scsi device to change the state of.
1805  *      @state: state to change to.
1806  *
1807  *      Returns zero if unsuccessful or an error if the requested 
1808  *      transition is illegal.
1809  **/
1810 int
1811 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
1812 {
1813         enum scsi_device_state oldstate = sdev->sdev_state;
1814
1815         if (state == oldstate)
1816                 return 0;
1817
1818         switch (state) {
1819         case SDEV_CREATED:
1820                 /* There are no legal states that come back to
1821                  * created.  This is the manually initialised start
1822                  * state */
1823                 goto illegal;
1824                         
1825         case SDEV_RUNNING:
1826                 switch (oldstate) {
1827                 case SDEV_CREATED:
1828                 case SDEV_OFFLINE:
1829                 case SDEV_QUIESCE:
1830                 case SDEV_BLOCK:
1831                         break;
1832                 default:
1833                         goto illegal;
1834                 }
1835                 break;
1836
1837         case SDEV_QUIESCE:
1838                 switch (oldstate) {
1839                 case SDEV_RUNNING:
1840                 case SDEV_OFFLINE:
1841                         break;
1842                 default:
1843                         goto illegal;
1844                 }
1845                 break;
1846
1847         case SDEV_OFFLINE:
1848                 switch (oldstate) {
1849                 case SDEV_CREATED:
1850                 case SDEV_RUNNING:
1851                 case SDEV_QUIESCE:
1852                 case SDEV_BLOCK:
1853                         break;
1854                 default:
1855                         goto illegal;
1856                 }
1857                 break;
1858
1859         case SDEV_BLOCK:
1860                 switch (oldstate) {
1861                 case SDEV_CREATED:
1862                 case SDEV_RUNNING:
1863                         break;
1864                 default:
1865                         goto illegal;
1866                 }
1867                 break;
1868
1869         case SDEV_CANCEL:
1870                 switch (oldstate) {
1871                 case SDEV_CREATED:
1872                 case SDEV_RUNNING:
1873                 case SDEV_OFFLINE:
1874                 case SDEV_BLOCK:
1875                         break;
1876                 default:
1877                         goto illegal;
1878                 }
1879                 break;
1880
1881         case SDEV_DEL:
1882                 switch (oldstate) {
1883                 case SDEV_CANCEL:
1884                         break;
1885                 default:
1886                         goto illegal;
1887                 }
1888                 break;
1889
1890         }
1891         sdev->sdev_state = state;
1892         return 0;
1893
1894  illegal:
1895         SCSI_LOG_ERROR_RECOVERY(1, 
1896                                 dev_printk(KERN_ERR, &sdev->sdev_gendev,
1897                                            "Illegal state transition %s->%s\n",
1898                                            scsi_device_state_name(oldstate),
1899                                            scsi_device_state_name(state))
1900                                 );
1901         return -EINVAL;
1902 }
1903 EXPORT_SYMBOL(scsi_device_set_state);
1904
1905 /**
1906  *      scsi_device_quiesce - Block user issued commands.
1907  *      @sdev:  scsi device to quiesce.
1908  *
1909  *      This works by trying to transition to the SDEV_QUIESCE state
1910  *      (which must be a legal transition).  When the device is in this
1911  *      state, only special requests will be accepted, all others will
1912  *      be deferred.  Since special requests may also be requeued requests,
1913  *      a successful return doesn't guarantee the device will be 
1914  *      totally quiescent.
1915  *
1916  *      Must be called with user context, may sleep.
1917  *
1918  *      Returns zero if unsuccessful or an error if not.
1919  **/
1920 int
1921 scsi_device_quiesce(struct scsi_device *sdev)
1922 {
1923         int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
1924         if (err)
1925                 return err;
1926
1927         scsi_run_queue(sdev->request_queue);
1928         while (sdev->device_busy) {
1929                 msleep_interruptible(200);
1930                 scsi_run_queue(sdev->request_queue);
1931         }
1932         return 0;
1933 }
1934 EXPORT_SYMBOL(scsi_device_quiesce);
1935
1936 /**
1937  *      scsi_device_resume - Restart user issued commands to a quiesced device.
1938  *      @sdev:  scsi device to resume.
1939  *
1940  *      Moves the device from quiesced back to running and restarts the
1941  *      queues.
1942  *
1943  *      Must be called with user context, may sleep.
1944  **/
1945 void
1946 scsi_device_resume(struct scsi_device *sdev)
1947 {
1948         if(scsi_device_set_state(sdev, SDEV_RUNNING))
1949                 return;
1950         scsi_run_queue(sdev->request_queue);
1951 }
1952 EXPORT_SYMBOL(scsi_device_resume);
1953
1954 static void
1955 device_quiesce_fn(struct scsi_device *sdev, void *data)
1956 {
1957         scsi_device_quiesce(sdev);
1958 }
1959
1960 void
1961 scsi_target_quiesce(struct scsi_target *starget)
1962 {
1963         starget_for_each_device(starget, NULL, device_quiesce_fn);
1964 }
1965 EXPORT_SYMBOL(scsi_target_quiesce);
1966
1967 static void
1968 device_resume_fn(struct scsi_device *sdev, void *data)
1969 {
1970         scsi_device_resume(sdev);
1971 }
1972
1973 void
1974 scsi_target_resume(struct scsi_target *starget)
1975 {
1976         starget_for_each_device(starget, NULL, device_resume_fn);
1977 }
1978 EXPORT_SYMBOL(scsi_target_resume);
1979
1980 /**
1981  * scsi_internal_device_block - internal function to put a device
1982  *                              temporarily into the SDEV_BLOCK state
1983  * @sdev:       device to block
1984  *
1985  * Block request made by scsi lld's to temporarily stop all
1986  * scsi commands on the specified device.  Called from interrupt
1987  * or normal process context.
1988  *
1989  * Returns zero if successful or error if not
1990  *
1991  * Notes:       
1992  *      This routine transitions the device to the SDEV_BLOCK state
1993  *      (which must be a legal transition).  When the device is in this
1994  *      state, all commands are deferred until the scsi lld reenables
1995  *      the device with scsi_device_unblock or device_block_tmo fires.
1996  *      This routine assumes the host_lock is held on entry.
1997  **/
1998 int
1999 scsi_internal_device_block(struct scsi_device *sdev)
2000 {
2001         request_queue_t *q = sdev->request_queue;
2002         unsigned long flags;
2003         int err = 0;
2004
2005         err = scsi_device_set_state(sdev, SDEV_BLOCK);
2006         if (err)
2007                 return err;
2008
2009         /* 
2010          * The device has transitioned to SDEV_BLOCK.  Stop the
2011          * block layer from calling the midlayer with this device's
2012          * request queue. 
2013          */
2014         spin_lock_irqsave(q->queue_lock, flags);
2015         blk_stop_queue(q);
2016         spin_unlock_irqrestore(q->queue_lock, flags);
2017
2018         return 0;
2019 }
2020 EXPORT_SYMBOL_GPL(scsi_internal_device_block);
2021  
2022 /**
2023  * scsi_internal_device_unblock - resume a device after a block request
2024  * @sdev:       device to resume
2025  *
2026  * Called by scsi lld's or the midlayer to restart the device queue
2027  * for the previously suspended scsi device.  Called from interrupt or
2028  * normal process context.
2029  *
2030  * Returns zero if successful or error if not.
2031  *
2032  * Notes:       
2033  *      This routine transitions the device to the SDEV_RUNNING state
2034  *      (which must be a legal transition) allowing the midlayer to
2035  *      goose the queue for this device.  This routine assumes the 
2036  *      host_lock is held upon entry.
2037  **/
2038 int
2039 scsi_internal_device_unblock(struct scsi_device *sdev)
2040 {
2041         request_queue_t *q = sdev->request_queue; 
2042         int err;
2043         unsigned long flags;
2044         
2045         /* 
2046          * Try to transition the scsi device to SDEV_RUNNING
2047          * and goose the device queue if successful.  
2048          */
2049         err = scsi_device_set_state(sdev, SDEV_RUNNING);
2050         if (err)
2051                 return err;
2052
2053         spin_lock_irqsave(q->queue_lock, flags);
2054         blk_start_queue(q);
2055         spin_unlock_irqrestore(q->queue_lock, flags);
2056
2057         return 0;
2058 }
2059 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
2060
2061 static void
2062 device_block(struct scsi_device *sdev, void *data)
2063 {
2064         scsi_internal_device_block(sdev);
2065 }
2066
2067 static int
2068 target_block(struct device *dev, void *data)
2069 {
2070         if (scsi_is_target_device(dev))
2071                 starget_for_each_device(to_scsi_target(dev), NULL,
2072                                         device_block);
2073         return 0;
2074 }
2075
2076 void
2077 scsi_target_block(struct device *dev)
2078 {
2079         if (scsi_is_target_device(dev))
2080                 starget_for_each_device(to_scsi_target(dev), NULL,
2081                                         device_block);
2082         else
2083                 device_for_each_child(dev, NULL, target_block);
2084 }
2085 EXPORT_SYMBOL_GPL(scsi_target_block);
2086
2087 static void
2088 device_unblock(struct scsi_device *sdev, void *data)
2089 {
2090         scsi_internal_device_unblock(sdev);
2091 }
2092
2093 static int
2094 target_unblock(struct device *dev, void *data)
2095 {
2096         if (scsi_is_target_device(dev))
2097                 starget_for_each_device(to_scsi_target(dev), NULL,
2098                                         device_unblock);
2099         return 0;
2100 }
2101
2102 void
2103 scsi_target_unblock(struct device *dev)
2104 {
2105         if (scsi_is_target_device(dev))
2106                 starget_for_each_device(to_scsi_target(dev), NULL,
2107                                         device_unblock);
2108         else
2109                 device_for_each_child(dev, NULL, target_unblock);
2110 }
2111 EXPORT_SYMBOL_GPL(scsi_target_unblock);