Merge /spare/repo/linux-2.6/
[linux-2.6] / 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 static void scsi_release_buffers(struct scsi_cmnd *cmd);
101
102 /*
103  * Function:    scsi_unprep_request()
104  *
105  * Purpose:     Remove all preparation done for a request, including its
106  *              associated scsi_cmnd, so that it can be requeued.
107  *
108  * Arguments:   req     - request to unprepare
109  *
110  * Lock status: Assumed that no locks are held upon entry.
111  *
112  * Returns:     Nothing.
113  */
114 static void scsi_unprep_request(struct request *req)
115 {
116         struct scsi_cmnd *cmd = req->special;
117
118         req->flags &= ~REQ_DONTPREP;
119         req->special = (req->flags & REQ_SPECIAL) ? cmd->sc_request : NULL;
120
121         scsi_put_command(cmd);
122 }
123
124 /*
125  * Function:    scsi_queue_insert()
126  *
127  * Purpose:     Insert a command in the midlevel queue.
128  *
129  * Arguments:   cmd    - command that we are adding to queue.
130  *              reason - why we are inserting command to queue.
131  *
132  * Lock status: Assumed that lock is not held upon entry.
133  *
134  * Returns:     Nothing.
135  *
136  * Notes:       We do this for one of two cases.  Either the host is busy
137  *              and it cannot accept any more commands for the time being,
138  *              or the device returned QUEUE_FULL and can accept no more
139  *              commands.
140  * Notes:       This could be called either from an interrupt context or a
141  *              normal process context.
142  */
143 int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
144 {
145         struct Scsi_Host *host = cmd->device->host;
146         struct scsi_device *device = cmd->device;
147         struct request_queue *q = device->request_queue;
148         unsigned long flags;
149
150         SCSI_LOG_MLQUEUE(1,
151                  printk("Inserting command %p into mlqueue\n", cmd));
152
153         /*
154          * Set the appropriate busy bit for the device/host.
155          *
156          * If the host/device isn't busy, assume that something actually
157          * completed, and that we should be able to queue a command now.
158          *
159          * Note that the prior mid-layer assumption that any host could
160          * always queue at least one command is now broken.  The mid-layer
161          * will implement a user specifiable stall (see
162          * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
163          * if a command is requeued with no other commands outstanding
164          * either for the device or for the host.
165          */
166         if (reason == SCSI_MLQUEUE_HOST_BUSY)
167                 host->host_blocked = host->max_host_blocked;
168         else if (reason == SCSI_MLQUEUE_DEVICE_BUSY)
169                 device->device_blocked = device->max_device_blocked;
170
171         /*
172          * Decrement the counters, since these commands are no longer
173          * active on the host/device.
174          */
175         scsi_device_unbusy(device);
176
177         /*
178          * Requeue this command.  It will go before all other commands
179          * that are already in the queue.
180          *
181          * NOTE: there is magic here about the way the queue is plugged if
182          * we have no outstanding commands.
183          * 
184          * Although we *don't* plug the queue, we call the request
185          * function.  The SCSI request function detects the blocked condition
186          * and plugs the queue appropriately.
187          */
188         spin_lock_irqsave(q->queue_lock, flags);
189         blk_requeue_request(q, cmd->request);
190         spin_unlock_irqrestore(q->queue_lock, flags);
191
192         scsi_run_queue(q);
193
194         return 0;
195 }
196
197 /*
198  * Function:    scsi_do_req
199  *
200  * Purpose:     Queue a SCSI request
201  *
202  * Arguments:   sreq      - command descriptor.
203  *              cmnd      - actual SCSI command to be performed.
204  *              buffer    - data buffer.
205  *              bufflen   - size of data buffer.
206  *              done      - completion function to be run.
207  *              timeout   - how long to let it run before timeout.
208  *              retries   - number of retries we allow.
209  *
210  * Lock status: No locks held upon entry.
211  *
212  * Returns:     Nothing.
213  *
214  * Notes:       This function is only used for queueing requests for things
215  *              like ioctls and character device requests - this is because
216  *              we essentially just inject a request into the queue for the
217  *              device.
218  *
219  *              In order to support the scsi_device_quiesce function, we
220  *              now inject requests on the *head* of the device queue
221  *              rather than the tail.
222  */
223 void scsi_do_req(struct scsi_request *sreq, const void *cmnd,
224                  void *buffer, unsigned bufflen,
225                  void (*done)(struct scsi_cmnd *),
226                  int timeout, int retries)
227 {
228         /*
229          * If the upper level driver is reusing these things, then
230          * we should release the low-level block now.  Another one will
231          * be allocated later when this request is getting queued.
232          */
233         __scsi_release_request(sreq);
234
235         /*
236          * Our own function scsi_done (which marks the host as not busy,
237          * disables the timeout counter, etc) will be called by us or by the
238          * scsi_hosts[host].queuecommand() function needs to also call
239          * the completion function for the high level driver.
240          */
241         memcpy(sreq->sr_cmnd, cmnd, sizeof(sreq->sr_cmnd));
242         sreq->sr_bufflen = bufflen;
243         sreq->sr_buffer = buffer;
244         sreq->sr_allowed = retries;
245         sreq->sr_done = done;
246         sreq->sr_timeout_per_command = timeout;
247
248         if (sreq->sr_cmd_len == 0)
249                 sreq->sr_cmd_len = COMMAND_SIZE(sreq->sr_cmnd[0]);
250
251         /*
252          * head injection *required* here otherwise quiesce won't work
253          */
254         scsi_insert_special_req(sreq, 1);
255 }
256 EXPORT_SYMBOL(scsi_do_req);
257
258 /* This is the end routine we get to if a command was never attached
259  * to the request.  Simply complete the request without changing
260  * rq_status; this will cause a DRIVER_ERROR. */
261 static void scsi_wait_req_end_io(struct request *req)
262 {
263         BUG_ON(!req->waiting);
264
265         complete(req->waiting);
266 }
267
268 void scsi_wait_req(struct scsi_request *sreq, const void *cmnd, void *buffer,
269                    unsigned bufflen, int timeout, int retries)
270 {
271         DECLARE_COMPLETION(wait);
272         int write = (sreq->sr_data_direction == DMA_TO_DEVICE);
273         struct request *req;
274
275         req = blk_get_request(sreq->sr_device->request_queue, write,
276                               __GFP_WAIT);
277         if (bufflen && blk_rq_map_kern(sreq->sr_device->request_queue, req,
278                                        buffer, bufflen, __GFP_WAIT)) {
279                 sreq->sr_result = DRIVER_ERROR << 24;
280                 blk_put_request(req);
281                 return;
282         }
283
284         req->flags |= REQ_NOMERGE;
285         req->waiting = &wait;
286         req->end_io = scsi_wait_req_end_io;
287         req->cmd_len = COMMAND_SIZE(((u8 *)cmnd)[0]);
288         req->sense = sreq->sr_sense_buffer;
289         req->sense_len = 0;
290         memcpy(req->cmd, cmnd, req->cmd_len);
291         req->timeout = timeout;
292         req->flags |= REQ_BLOCK_PC;
293         req->rq_disk = NULL;
294         blk_insert_request(sreq->sr_device->request_queue, req,
295                            sreq->sr_data_direction == DMA_TO_DEVICE, NULL);
296         wait_for_completion(&wait);
297         sreq->sr_request->waiting = NULL;
298         sreq->sr_result = req->errors;
299         if (req->errors)
300                 sreq->sr_result |= (DRIVER_ERROR << 24);
301
302         blk_put_request(req);
303 }
304
305 EXPORT_SYMBOL(scsi_wait_req);
306
307 /**
308  * scsi_execute - insert request and wait for the result
309  * @sdev:       scsi device
310  * @cmd:        scsi command
311  * @data_direction: data direction
312  * @buffer:     data buffer
313  * @bufflen:    len of buffer
314  * @sense:      optional sense buffer
315  * @timeout:    request timeout in seconds
316  * @retries:    number of times to retry request
317  * @flags:      or into request flags;
318  *
319  * returns the req->errors value which is the the scsi_cmnd result
320  * field.
321  **/
322 int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
323                  int data_direction, void *buffer, unsigned bufflen,
324                  unsigned char *sense, int timeout, int retries, int flags)
325 {
326         struct request *req;
327         int write = (data_direction == DMA_TO_DEVICE);
328         int ret = DRIVER_ERROR << 24;
329
330         req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
331
332         if (bufflen &&  blk_rq_map_kern(sdev->request_queue, req,
333                                         buffer, bufflen, __GFP_WAIT))
334                 goto out;
335
336         req->cmd_len = COMMAND_SIZE(cmd[0]);
337         memcpy(req->cmd, cmd, req->cmd_len);
338         req->sense = sense;
339         req->sense_len = 0;
340         req->timeout = timeout;
341         req->flags |= flags | REQ_BLOCK_PC | REQ_SPECIAL | REQ_QUIET;
342
343         /*
344          * head injection *required* here otherwise quiesce won't work
345          */
346         blk_execute_rq(req->q, NULL, req, 1);
347
348         ret = req->errors;
349  out:
350         blk_put_request(req);
351
352         return ret;
353 }
354 EXPORT_SYMBOL(scsi_execute);
355
356
357 int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
358                      int data_direction, void *buffer, unsigned bufflen,
359                      struct scsi_sense_hdr *sshdr, int timeout, int retries)
360 {
361         char *sense = NULL;
362         int result;
363         
364         if (sshdr) {
365                 sense = kmalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
366                 if (!sense)
367                         return DRIVER_ERROR << 24;
368                 memset(sense, 0, SCSI_SENSE_BUFFERSIZE);
369         }
370         result = scsi_execute(sdev, cmd, data_direction, buffer, bufflen,
371                                   sense, timeout, retries, 0);
372         if (sshdr)
373                 scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, sshdr);
374
375         kfree(sense);
376         return result;
377 }
378 EXPORT_SYMBOL(scsi_execute_req);
379
380 /*
381  * Function:    scsi_init_cmd_errh()
382  *
383  * Purpose:     Initialize cmd fields related to error handling.
384  *
385  * Arguments:   cmd     - command that is ready to be queued.
386  *
387  * Returns:     Nothing
388  *
389  * Notes:       This function has the job of initializing a number of
390  *              fields related to error handling.   Typically this will
391  *              be called once for each command, as required.
392  */
393 static int scsi_init_cmd_errh(struct scsi_cmnd *cmd)
394 {
395         cmd->serial_number = 0;
396
397         memset(cmd->sense_buffer, 0, sizeof cmd->sense_buffer);
398
399         if (cmd->cmd_len == 0)
400                 cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);
401
402         /*
403          * We need saved copies of a number of fields - this is because
404          * error handling may need to overwrite these with different values
405          * to run different commands, and once error handling is complete,
406          * we will need to restore these values prior to running the actual
407          * command.
408          */
409         cmd->old_use_sg = cmd->use_sg;
410         cmd->old_cmd_len = cmd->cmd_len;
411         cmd->sc_old_data_direction = cmd->sc_data_direction;
412         cmd->old_underflow = cmd->underflow;
413         memcpy(cmd->data_cmnd, cmd->cmnd, sizeof(cmd->cmnd));
414         cmd->buffer = cmd->request_buffer;
415         cmd->bufflen = cmd->request_bufflen;
416
417         return 1;
418 }
419
420 /*
421  * Function:   scsi_setup_cmd_retry()
422  *
423  * Purpose:    Restore the command state for a retry
424  *
425  * Arguments:  cmd      - command to be restored
426  *
427  * Returns:    Nothing
428  *
429  * Notes:      Immediately prior to retrying a command, we need
430  *             to restore certain fields that we saved above.
431  */
432 void scsi_setup_cmd_retry(struct scsi_cmnd *cmd)
433 {
434         memcpy(cmd->cmnd, cmd->data_cmnd, sizeof(cmd->data_cmnd));
435         cmd->request_buffer = cmd->buffer;
436         cmd->request_bufflen = cmd->bufflen;
437         cmd->use_sg = cmd->old_use_sg;
438         cmd->cmd_len = cmd->old_cmd_len;
439         cmd->sc_data_direction = cmd->sc_old_data_direction;
440         cmd->underflow = cmd->old_underflow;
441 }
442
443 void scsi_device_unbusy(struct scsi_device *sdev)
444 {
445         struct Scsi_Host *shost = sdev->host;
446         unsigned long flags;
447
448         spin_lock_irqsave(shost->host_lock, flags);
449         shost->host_busy--;
450         if (unlikely(scsi_host_in_recovery(shost) &&
451                      shost->host_failed))
452                 scsi_eh_wakeup(shost);
453         spin_unlock(shost->host_lock);
454         spin_lock(sdev->request_queue->queue_lock);
455         sdev->device_busy--;
456         spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
457 }
458
459 /*
460  * Called for single_lun devices on IO completion. Clear starget_sdev_user,
461  * and call blk_run_queue for all the scsi_devices on the target -
462  * including current_sdev first.
463  *
464  * Called with *no* scsi locks held.
465  */
466 static void scsi_single_lun_run(struct scsi_device *current_sdev)
467 {
468         struct Scsi_Host *shost = current_sdev->host;
469         struct scsi_device *sdev, *tmp;
470         struct scsi_target *starget = scsi_target(current_sdev);
471         unsigned long flags;
472
473         spin_lock_irqsave(shost->host_lock, flags);
474         starget->starget_sdev_user = NULL;
475         spin_unlock_irqrestore(shost->host_lock, flags);
476
477         /*
478          * Call blk_run_queue for all LUNs on the target, starting with
479          * current_sdev. We race with others (to set starget_sdev_user),
480          * but in most cases, we will be first. Ideally, each LU on the
481          * target would get some limited time or requests on the target.
482          */
483         blk_run_queue(current_sdev->request_queue);
484
485         spin_lock_irqsave(shost->host_lock, flags);
486         if (starget->starget_sdev_user)
487                 goto out;
488         list_for_each_entry_safe(sdev, tmp, &starget->devices,
489                         same_target_siblings) {
490                 if (sdev == current_sdev)
491                         continue;
492                 if (scsi_device_get(sdev))
493                         continue;
494
495                 spin_unlock_irqrestore(shost->host_lock, flags);
496                 blk_run_queue(sdev->request_queue);
497                 spin_lock_irqsave(shost->host_lock, flags);
498         
499                 scsi_device_put(sdev);
500         }
501  out:
502         spin_unlock_irqrestore(shost->host_lock, flags);
503 }
504
505 /*
506  * Function:    scsi_run_queue()
507  *
508  * Purpose:     Select a proper request queue to serve next
509  *
510  * Arguments:   q       - last request's queue
511  *
512  * Returns:     Nothing
513  *
514  * Notes:       The previous command was completely finished, start
515  *              a new one if possible.
516  */
517 static void scsi_run_queue(struct request_queue *q)
518 {
519         struct scsi_device *sdev = q->queuedata;
520         struct Scsi_Host *shost = sdev->host;
521         unsigned long flags;
522
523         if (sdev->single_lun)
524                 scsi_single_lun_run(sdev);
525
526         spin_lock_irqsave(shost->host_lock, flags);
527         while (!list_empty(&shost->starved_list) &&
528                !shost->host_blocked && !shost->host_self_blocked &&
529                 !((shost->can_queue > 0) &&
530                   (shost->host_busy >= shost->can_queue))) {
531                 /*
532                  * As long as shost is accepting commands and we have
533                  * starved queues, call blk_run_queue. scsi_request_fn
534                  * drops the queue_lock and can add us back to the
535                  * starved_list.
536                  *
537                  * host_lock protects the starved_list and starved_entry.
538                  * scsi_request_fn must get the host_lock before checking
539                  * or modifying starved_list or starved_entry.
540                  */
541                 sdev = list_entry(shost->starved_list.next,
542                                           struct scsi_device, starved_entry);
543                 list_del_init(&sdev->starved_entry);
544                 spin_unlock_irqrestore(shost->host_lock, flags);
545
546                 blk_run_queue(sdev->request_queue);
547
548                 spin_lock_irqsave(shost->host_lock, flags);
549                 if (unlikely(!list_empty(&sdev->starved_entry)))
550                         /*
551                          * sdev lost a race, and was put back on the
552                          * starved list. This is unlikely but without this
553                          * in theory we could loop forever.
554                          */
555                         break;
556         }
557         spin_unlock_irqrestore(shost->host_lock, flags);
558
559         blk_run_queue(q);
560 }
561
562 /*
563  * Function:    scsi_requeue_command()
564  *
565  * Purpose:     Handle post-processing of completed commands.
566  *
567  * Arguments:   q       - queue to operate on
568  *              cmd     - command that may need to be requeued.
569  *
570  * Returns:     Nothing
571  *
572  * Notes:       After command completion, there may be blocks left
573  *              over which weren't finished by the previous command
574  *              this can be for a number of reasons - the main one is
575  *              I/O errors in the middle of the request, in which case
576  *              we need to request the blocks that come after the bad
577  *              sector.
578  * Notes:       Upon return, cmd is a stale pointer.
579  */
580 static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
581 {
582         struct request *req = cmd->request;
583         unsigned long flags;
584
585         scsi_unprep_request(req);
586         spin_lock_irqsave(q->queue_lock, flags);
587         blk_requeue_request(q, req);
588         spin_unlock_irqrestore(q->queue_lock, flags);
589
590         scsi_run_queue(q);
591 }
592
593 void scsi_next_command(struct scsi_cmnd *cmd)
594 {
595         struct request_queue *q = cmd->device->request_queue;
596
597         scsi_put_command(cmd);
598         scsi_run_queue(q);
599 }
600
601 void scsi_run_host_queues(struct Scsi_Host *shost)
602 {
603         struct scsi_device *sdev;
604
605         shost_for_each_device(sdev, shost)
606                 scsi_run_queue(sdev->request_queue);
607 }
608
609 /*
610  * Function:    scsi_end_request()
611  *
612  * Purpose:     Post-processing of completed commands (usually invoked at end
613  *              of upper level post-processing and scsi_io_completion).
614  *
615  * Arguments:   cmd      - command that is complete.
616  *              uptodate - 1 if I/O indicates success, <= 0 for I/O error.
617  *              bytes    - number of bytes of completed I/O
618  *              requeue  - indicates whether we should requeue leftovers.
619  *
620  * Lock status: Assumed that lock is not held upon entry.
621  *
622  * Returns:     cmd if requeue required, NULL otherwise.
623  *
624  * Notes:       This is called for block device requests in order to
625  *              mark some number of sectors as complete.
626  * 
627  *              We are guaranteeing that the request queue will be goosed
628  *              at some point during this call.
629  * Notes:       If cmd was requeued, upon return it will be a stale pointer.
630  */
631 static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int uptodate,
632                                           int bytes, int requeue)
633 {
634         request_queue_t *q = cmd->device->request_queue;
635         struct request *req = cmd->request;
636         unsigned long flags;
637
638         /*
639          * If there are blocks left over at the end, set up the command
640          * to queue the remainder of them.
641          */
642         if (end_that_request_chunk(req, uptodate, bytes)) {
643                 int leftover = (req->hard_nr_sectors << 9);
644
645                 if (blk_pc_request(req))
646                         leftover = req->data_len;
647
648                 /* kill remainder if no retrys */
649                 if (!uptodate && blk_noretry_request(req))
650                         end_that_request_chunk(req, 0, leftover);
651                 else {
652                         if (requeue) {
653                                 /*
654                                  * Bleah.  Leftovers again.  Stick the
655                                  * leftovers in the front of the
656                                  * queue, and goose the queue again.
657                                  */
658                                 scsi_requeue_command(q, cmd);
659                                 cmd = NULL;
660                         }
661                         return cmd;
662                 }
663         }
664
665         add_disk_randomness(req->rq_disk);
666
667         spin_lock_irqsave(q->queue_lock, flags);
668         if (blk_rq_tagged(req))
669                 blk_queue_end_tag(q, req);
670         end_that_request_last(req);
671         spin_unlock_irqrestore(q->queue_lock, flags);
672
673         /*
674          * This will goose the queue request function at the end, so we don't
675          * need to worry about launching another command.
676          */
677         scsi_next_command(cmd);
678         return NULL;
679 }
680
681 static struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, int gfp_mask)
682 {
683         struct scsi_host_sg_pool *sgp;
684         struct scatterlist *sgl;
685
686         BUG_ON(!cmd->use_sg);
687
688         switch (cmd->use_sg) {
689         case 1 ... 8:
690                 cmd->sglist_len = 0;
691                 break;
692         case 9 ... 16:
693                 cmd->sglist_len = 1;
694                 break;
695         case 17 ... 32:
696                 cmd->sglist_len = 2;
697                 break;
698 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
699         case 33 ... 64:
700                 cmd->sglist_len = 3;
701                 break;
702 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
703         case 65 ... 128:
704                 cmd->sglist_len = 4;
705                 break;
706 #if (SCSI_MAX_PHYS_SEGMENTS  > 128)
707         case 129 ... 256:
708                 cmd->sglist_len = 5;
709                 break;
710 #endif
711 #endif
712 #endif
713         default:
714                 return NULL;
715         }
716
717         sgp = scsi_sg_pools + cmd->sglist_len;
718         sgl = mempool_alloc(sgp->pool, gfp_mask);
719         return sgl;
720 }
721
722 static void scsi_free_sgtable(struct scatterlist *sgl, int index)
723 {
724         struct scsi_host_sg_pool *sgp;
725
726         BUG_ON(index >= SG_MEMPOOL_NR);
727
728         sgp = scsi_sg_pools + index;
729         mempool_free(sgl, sgp->pool);
730 }
731
732 /*
733  * Function:    scsi_release_buffers()
734  *
735  * Purpose:     Completion processing for block device I/O requests.
736  *
737  * Arguments:   cmd     - command that we are bailing.
738  *
739  * Lock status: Assumed that no lock is held upon entry.
740  *
741  * Returns:     Nothing
742  *
743  * Notes:       In the event that an upper level driver rejects a
744  *              command, we must release resources allocated during
745  *              the __init_io() function.  Primarily this would involve
746  *              the scatter-gather table, and potentially any bounce
747  *              buffers.
748  */
749 static void scsi_release_buffers(struct scsi_cmnd *cmd)
750 {
751         struct request *req = cmd->request;
752
753         /*
754          * Free up any indirection buffers we allocated for DMA purposes. 
755          */
756         if (cmd->use_sg)
757                 scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
758         else if (cmd->request_buffer != req->buffer)
759                 kfree(cmd->request_buffer);
760
761         /*
762          * Zero these out.  They now point to freed memory, and it is
763          * dangerous to hang onto the pointers.
764          */
765         cmd->buffer  = NULL;
766         cmd->bufflen = 0;
767         cmd->request_buffer = NULL;
768         cmd->request_bufflen = 0;
769 }
770
771 /*
772  * Function:    scsi_io_completion()
773  *
774  * Purpose:     Completion processing for block device I/O requests.
775  *
776  * Arguments:   cmd   - command that is finished.
777  *
778  * Lock status: Assumed that no lock is held upon entry.
779  *
780  * Returns:     Nothing
781  *
782  * Notes:       This function is matched in terms of capabilities to
783  *              the function that created the scatter-gather list.
784  *              In other words, if there are no bounce buffers
785  *              (the normal case for most drivers), we don't need
786  *              the logic to deal with cleaning up afterwards.
787  *
788  *              We must do one of several things here:
789  *
790  *              a) Call scsi_end_request.  This will finish off the
791  *                 specified number of sectors.  If we are done, the
792  *                 command block will be released, and the queue
793  *                 function will be goosed.  If we are not done, then
794  *                 scsi_end_request will directly goose the queue.
795  *
796  *              b) We can just use scsi_requeue_command() here.  This would
797  *                 be used if we just wanted to retry, for example.
798  */
799 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
800                         unsigned int block_bytes)
801 {
802         int result = cmd->result;
803         int this_count = cmd->bufflen;
804         request_queue_t *q = cmd->device->request_queue;
805         struct request *req = cmd->request;
806         int clear_errors = 1;
807         struct scsi_sense_hdr sshdr;
808         int sense_valid = 0;
809         int sense_deferred = 0;
810
811         if (blk_complete_barrier_rq(q, req, good_bytes >> 9))
812                 return;
813
814         /*
815          * Free up any indirection buffers we allocated for DMA purposes. 
816          * For the case of a READ, we need to copy the data out of the
817          * bounce buffer and into the real buffer.
818          */
819         if (cmd->use_sg)
820                 scsi_free_sgtable(cmd->buffer, cmd->sglist_len);
821         else if (cmd->buffer != req->buffer) {
822                 if (rq_data_dir(req) == READ) {
823                         unsigned long flags;
824                         char *to = bio_kmap_irq(req->bio, &flags);
825                         memcpy(to, cmd->buffer, cmd->bufflen);
826                         bio_kunmap_irq(to, &flags);
827                 }
828                 kfree(cmd->buffer);
829         }
830
831         if (result) {
832                 sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
833                 if (sense_valid)
834                         sense_deferred = scsi_sense_is_deferred(&sshdr);
835         }
836         if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
837                 req->errors = result;
838                 if (result) {
839                         clear_errors = 0;
840                         if (sense_valid && req->sense) {
841                                 /*
842                                  * SG_IO wants current and deferred errors
843                                  */
844                                 int len = 8 + cmd->sense_buffer[7];
845
846                                 if (len > SCSI_SENSE_BUFFERSIZE)
847                                         len = SCSI_SENSE_BUFFERSIZE;
848                                 memcpy(req->sense, cmd->sense_buffer,  len);
849                                 req->sense_len = len;
850                         }
851                 } else
852                         req->data_len = cmd->resid;
853         }
854
855         /*
856          * Zero these out.  They now point to freed memory, and it is
857          * dangerous to hang onto the pointers.
858          */
859         cmd->buffer  = NULL;
860         cmd->bufflen = 0;
861         cmd->request_buffer = NULL;
862         cmd->request_bufflen = 0;
863
864         /*
865          * Next deal with any sectors which we were able to correctly
866          * handle.
867          */
868         if (good_bytes >= 0) {
869                 SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, %d bytes done.\n",
870                                               req->nr_sectors, good_bytes));
871                 SCSI_LOG_HLCOMPLETE(1, printk("use_sg is %d\n", cmd->use_sg));
872
873                 if (clear_errors)
874                         req->errors = 0;
875                 /*
876                  * If multiple sectors are requested in one buffer, then
877                  * they will have been finished off by the first command.
878                  * If not, then we have a multi-buffer command.
879                  *
880                  * If block_bytes != 0, it means we had a medium error
881                  * of some sort, and that we want to mark some number of
882                  * sectors as not uptodate.  Thus we want to inhibit
883                  * requeueing right here - we will requeue down below
884                  * when we handle the bad sectors.
885                  */
886
887                 /*
888                  * If the command completed without error, then either
889                  * finish off the rest of the command, or start a new one.
890                  */
891                 if (scsi_end_request(cmd, 1, good_bytes, result == 0) == NULL)
892                         return;
893         }
894         /*
895          * Now, if we were good little boys and girls, Santa left us a request
896          * sense buffer.  We can extract information from this, so we
897          * can choose a block to remap, etc.
898          */
899         if (sense_valid && !sense_deferred) {
900                 switch (sshdr.sense_key) {
901                 case UNIT_ATTENTION:
902                         if (cmd->device->removable) {
903                                 /* detected disc change.  set a bit 
904                                  * and quietly refuse further access.
905                                  */
906                                 cmd->device->changed = 1;
907                                 scsi_end_request(cmd, 0,
908                                                 this_count, 1);
909                                 return;
910                         } else {
911                                 /*
912                                 * Must have been a power glitch, or a
913                                 * bus reset.  Could not have been a
914                                 * media change, so we just retry the
915                                 * request and see what happens.  
916                                 */
917                                 scsi_requeue_command(q, cmd);
918                                 return;
919                         }
920                         break;
921                 case ILLEGAL_REQUEST:
922                         /*
923                         * If we had an ILLEGAL REQUEST returned, then we may
924                         * have performed an unsupported command.  The only
925                         * thing this should be would be a ten byte read where
926                         * only a six byte read was supported.  Also, on a
927                         * system where READ CAPACITY failed, we may have read
928                         * past the end of the disk.
929                         */
930                         if (cmd->device->use_10_for_rw &&
931                             (cmd->cmnd[0] == READ_10 ||
932                              cmd->cmnd[0] == WRITE_10)) {
933                                 cmd->device->use_10_for_rw = 0;
934                                 /*
935                                  * This will cause a retry with a 6-byte
936                                  * command.
937                                  */
938                                 scsi_requeue_command(q, cmd);
939                                 result = 0;
940                         } else {
941                                 scsi_end_request(cmd, 0, this_count, 1);
942                                 return;
943                         }
944                         break;
945                 case NOT_READY:
946                         /*
947                          * If the device is in the process of becoming ready,
948                          * retry.
949                          */
950                         if (sshdr.asc == 0x04 && sshdr.ascq == 0x01) {
951                                 scsi_requeue_command(q, cmd);
952                                 return;
953                         }
954                         if (!(req->flags & REQ_QUIET))
955                                 dev_printk(KERN_INFO,
956                                            &cmd->device->sdev_gendev,
957                                            "Device not ready.\n");
958                         scsi_end_request(cmd, 0, this_count, 1);
959                         return;
960                 case VOLUME_OVERFLOW:
961                         if (!(req->flags & REQ_QUIET)) {
962                                 dev_printk(KERN_INFO,
963                                            &cmd->device->sdev_gendev,
964                                            "Volume overflow, CDB: ");
965                                 __scsi_print_command(cmd->data_cmnd);
966                                 scsi_print_sense("", cmd);
967                         }
968                         scsi_end_request(cmd, 0, block_bytes, 1);
969                         return;
970                 default:
971                         break;
972                 }
973         }                       /* driver byte != 0 */
974         if (host_byte(result) == DID_RESET) {
975                 /*
976                  * Third party bus reset or reset for error
977                  * recovery reasons.  Just retry the request
978                  * and see what happens.  
979                  */
980                 scsi_requeue_command(q, cmd);
981                 return;
982         }
983         if (result) {
984                 if (!(req->flags & REQ_QUIET)) {
985                         dev_printk(KERN_INFO, &cmd->device->sdev_gendev,
986                                    "SCSI error: return code = 0x%x\n", result);
987
988                         if (driver_byte(result) & DRIVER_SENSE)
989                                 scsi_print_sense("", cmd);
990                 }
991                 /*
992                  * Mark a single buffer as not uptodate.  Queue the remainder.
993                  * We sometimes get this cruft in the event that a medium error
994                  * isn't properly reported.
995                  */
996                 block_bytes = req->hard_cur_sectors << 9;
997                 if (!block_bytes)
998                         block_bytes = req->data_len;
999                 scsi_end_request(cmd, 0, block_bytes, 1);
1000         }
1001 }
1002 EXPORT_SYMBOL(scsi_io_completion);
1003
1004 /*
1005  * Function:    scsi_init_io()
1006  *
1007  * Purpose:     SCSI I/O initialize function.
1008  *
1009  * Arguments:   cmd   - Command descriptor we wish to initialize
1010  *
1011  * Returns:     0 on success
1012  *              BLKPREP_DEFER if the failure is retryable
1013  *              BLKPREP_KILL if the failure is fatal
1014  */
1015 static int scsi_init_io(struct scsi_cmnd *cmd)
1016 {
1017         struct request     *req = cmd->request;
1018         struct scatterlist *sgpnt;
1019         int                count;
1020
1021         /*
1022          * if this is a rq->data based REQ_BLOCK_PC, setup for a non-sg xfer
1023          */
1024         if ((req->flags & REQ_BLOCK_PC) && !req->bio) {
1025                 cmd->request_bufflen = req->data_len;
1026                 cmd->request_buffer = req->data;
1027                 req->buffer = req->data;
1028                 cmd->use_sg = 0;
1029                 return 0;
1030         }
1031
1032         /*
1033          * we used to not use scatter-gather for single segment request,
1034          * but now we do (it makes highmem I/O easier to support without
1035          * kmapping pages)
1036          */
1037         cmd->use_sg = req->nr_phys_segments;
1038
1039         /*
1040          * if sg table allocation fails, requeue request later.
1041          */
1042         sgpnt = scsi_alloc_sgtable(cmd, GFP_ATOMIC);
1043         if (unlikely(!sgpnt))
1044                 return BLKPREP_DEFER;
1045
1046         cmd->request_buffer = (char *) sgpnt;
1047         cmd->request_bufflen = req->nr_sectors << 9;
1048         if (blk_pc_request(req))
1049                 cmd->request_bufflen = req->data_len;
1050         req->buffer = NULL;
1051
1052         /* 
1053          * Next, walk the list, and fill in the addresses and sizes of
1054          * each segment.
1055          */
1056         count = blk_rq_map_sg(req->q, req, cmd->request_buffer);
1057
1058         /*
1059          * mapped well, send it off
1060          */
1061         if (likely(count <= cmd->use_sg)) {
1062                 cmd->use_sg = count;
1063                 return 0;
1064         }
1065
1066         printk(KERN_ERR "Incorrect number of segments after building list\n");
1067         printk(KERN_ERR "counted %d, received %d\n", count, cmd->use_sg);
1068         printk(KERN_ERR "req nr_sec %lu, cur_nr_sec %u\n", req->nr_sectors,
1069                         req->current_nr_sectors);
1070
1071         /* release the command and kill it */
1072         scsi_release_buffers(cmd);
1073         scsi_put_command(cmd);
1074         return BLKPREP_KILL;
1075 }
1076
1077 static int scsi_prepare_flush_fn(request_queue_t *q, struct request *rq)
1078 {
1079         struct scsi_device *sdev = q->queuedata;
1080         struct scsi_driver *drv;
1081
1082         if (sdev->sdev_state == SDEV_RUNNING) {
1083                 drv = *(struct scsi_driver **) rq->rq_disk->private_data;
1084
1085                 if (drv->prepare_flush)
1086                         return drv->prepare_flush(q, rq);
1087         }
1088
1089         return 0;
1090 }
1091
1092 static void scsi_end_flush_fn(request_queue_t *q, struct request *rq)
1093 {
1094         struct scsi_device *sdev = q->queuedata;
1095         struct request *flush_rq = rq->end_io_data;
1096         struct scsi_driver *drv;
1097
1098         if (flush_rq->errors) {
1099                 printk("scsi: barrier error, disabling flush support\n");
1100                 blk_queue_ordered(q, QUEUE_ORDERED_NONE);
1101         }
1102
1103         if (sdev->sdev_state == SDEV_RUNNING) {
1104                 drv = *(struct scsi_driver **) rq->rq_disk->private_data;
1105                 drv->end_flush(q, rq);
1106         }
1107 }
1108
1109 static int scsi_issue_flush_fn(request_queue_t *q, struct gendisk *disk,
1110                                sector_t *error_sector)
1111 {
1112         struct scsi_device *sdev = q->queuedata;
1113         struct scsi_driver *drv;
1114
1115         if (sdev->sdev_state != SDEV_RUNNING)
1116                 return -ENXIO;
1117
1118         drv = *(struct scsi_driver **) disk->private_data;
1119         if (drv->issue_flush)
1120                 return drv->issue_flush(&sdev->sdev_gendev, error_sector);
1121
1122         return -EOPNOTSUPP;
1123 }
1124
1125 static void scsi_generic_done(struct scsi_cmnd *cmd)
1126 {
1127         BUG_ON(!blk_pc_request(cmd->request));
1128         scsi_io_completion(cmd, cmd->result == 0 ? cmd->bufflen : 0, 0);
1129 }
1130
1131 static int scsi_prep_fn(struct request_queue *q, struct request *req)
1132 {
1133         struct scsi_device *sdev = q->queuedata;
1134         struct scsi_cmnd *cmd;
1135         int specials_only = 0;
1136
1137         /*
1138          * Just check to see if the device is online.  If it isn't, we
1139          * refuse to process any commands.  The device must be brought
1140          * online before trying any recovery commands
1141          */
1142         if (unlikely(!scsi_device_online(sdev))) {
1143                 printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to offline device\n",
1144                        sdev->host->host_no, sdev->id, sdev->lun);
1145                 goto kill;
1146         }
1147         if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
1148                 /* OK, we're not in a running state don't prep
1149                  * user commands */
1150                 if (sdev->sdev_state == SDEV_DEL) {
1151                         /* Device is fully deleted, no commands
1152                          * at all allowed down */
1153                         printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to dead device\n",
1154                                sdev->host->host_no, sdev->id, sdev->lun);
1155                         goto kill;
1156                 }
1157                 /* OK, we only allow special commands (i.e. not
1158                  * user initiated ones */
1159                 specials_only = sdev->sdev_state;
1160         }
1161
1162         /*
1163          * Find the actual device driver associated with this command.
1164          * The SPECIAL requests are things like character device or
1165          * ioctls, which did not originate from ll_rw_blk.  Note that
1166          * the special field is also used to indicate the cmd for
1167          * the remainder of a partially fulfilled request that can 
1168          * come up when there is a medium error.  We have to treat
1169          * these two cases differently.  We differentiate by looking
1170          * at request->cmd, as this tells us the real story.
1171          */
1172         if (req->flags & REQ_SPECIAL && req->special) {
1173                 struct scsi_request *sreq = req->special;
1174
1175                 if (sreq->sr_magic == SCSI_REQ_MAGIC) {
1176                         cmd = scsi_get_command(sreq->sr_device, GFP_ATOMIC);
1177                         if (unlikely(!cmd))
1178                                 goto defer;
1179                         scsi_init_cmd_from_req(cmd, sreq);
1180                 } else
1181                         cmd = req->special;
1182         } else if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1183
1184                 if(unlikely(specials_only) && !(req->flags & REQ_SPECIAL)) {
1185                         if(specials_only == SDEV_QUIESCE ||
1186                                         specials_only == SDEV_BLOCK)
1187                                 goto defer;
1188                         
1189                         printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to device being removed\n",
1190                                sdev->host->host_no, sdev->id, sdev->lun);
1191                         goto kill;
1192                 }
1193                         
1194                         
1195                 /*
1196                  * Now try and find a command block that we can use.
1197                  */
1198                 if (!req->special) {
1199                         cmd = scsi_get_command(sdev, GFP_ATOMIC);
1200                         if (unlikely(!cmd))
1201                                 goto defer;
1202                 } else
1203                         cmd = req->special;
1204                 
1205                 /* pull a tag out of the request if we have one */
1206                 cmd->tag = req->tag;
1207         } else {
1208                 blk_dump_rq_flags(req, "SCSI bad req");
1209                 goto kill;
1210         }
1211         
1212         /* note the overloading of req->special.  When the tag
1213          * is active it always means cmd.  If the tag goes
1214          * back for re-queueing, it may be reset */
1215         req->special = cmd;
1216         cmd->request = req;
1217         
1218         /*
1219          * FIXME: drop the lock here because the functions below
1220          * expect to be called without the queue lock held.  Also,
1221          * previously, we dequeued the request before dropping the
1222          * lock.  We hope REQ_STARTED prevents anything untoward from
1223          * happening now.
1224          */
1225         if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1226                 struct scsi_driver *drv;
1227                 int ret;
1228
1229                 /*
1230                  * This will do a couple of things:
1231                  *  1) Fill in the actual SCSI command.
1232                  *  2) Fill in any other upper-level specific fields
1233                  * (timeout).
1234                  *
1235                  * If this returns 0, it means that the request failed
1236                  * (reading past end of disk, reading offline device,
1237                  * etc).   This won't actually talk to the device, but
1238                  * some kinds of consistency checking may cause the     
1239                  * request to be rejected immediately.
1240                  */
1241
1242                 /* 
1243                  * This sets up the scatter-gather table (allocating if
1244                  * required).
1245                  */
1246                 ret = scsi_init_io(cmd);
1247                 switch(ret) {
1248                 case BLKPREP_KILL:
1249                         /* BLKPREP_KILL return also releases the command */
1250                         goto kill;
1251                 case BLKPREP_DEFER:
1252                         goto defer;
1253                 }
1254                 
1255                 /*
1256                  * Initialize the actual SCSI command for this request.
1257                  */
1258                 if (req->rq_disk) {
1259                         drv = *(struct scsi_driver **)req->rq_disk->private_data;
1260                         if (unlikely(!drv->init_command(cmd))) {
1261                                 scsi_release_buffers(cmd);
1262                                 scsi_put_command(cmd);
1263                                 goto kill;
1264                         }
1265                 } else {
1266                         memcpy(cmd->cmnd, req->cmd, sizeof(cmd->cmnd));
1267                         cmd->cmd_len = req->cmd_len;
1268                         if (rq_data_dir(req) == WRITE)
1269                                 cmd->sc_data_direction = DMA_TO_DEVICE;
1270                         else if (req->data_len)
1271                                 cmd->sc_data_direction = DMA_FROM_DEVICE;
1272                         else
1273                                 cmd->sc_data_direction = DMA_NONE;
1274                         
1275                         cmd->transfersize = req->data_len;
1276                         cmd->allowed = 3;
1277                         cmd->timeout_per_command = req->timeout;
1278                         cmd->done = scsi_generic_done;
1279                 }
1280         }
1281
1282         /*
1283          * The request is now prepped, no need to come back here
1284          */
1285         req->flags |= REQ_DONTPREP;
1286         return BLKPREP_OK;
1287
1288  defer:
1289         /* If we defer, the elv_next_request() returns NULL, but the
1290          * queue must be restarted, so we plug here if no returning
1291          * command will automatically do that. */
1292         if (sdev->device_busy == 0)
1293                 blk_plug_device(q);
1294         return BLKPREP_DEFER;
1295  kill:
1296         req->errors = DID_NO_CONNECT << 16;
1297         return BLKPREP_KILL;
1298 }
1299
1300 /*
1301  * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1302  * return 0.
1303  *
1304  * Called with the queue_lock held.
1305  */
1306 static inline int scsi_dev_queue_ready(struct request_queue *q,
1307                                   struct scsi_device *sdev)
1308 {
1309         if (sdev->device_busy >= sdev->queue_depth)
1310                 return 0;
1311         if (sdev->device_busy == 0 && sdev->device_blocked) {
1312                 /*
1313                  * unblock after device_blocked iterates to zero
1314                  */
1315                 if (--sdev->device_blocked == 0) {
1316                         SCSI_LOG_MLQUEUE(3,
1317                                 printk("scsi%d (%d:%d) unblocking device at"
1318                                        " zero depth\n", sdev->host->host_no,
1319                                        sdev->id, sdev->lun));
1320                 } else {
1321                         blk_plug_device(q);
1322                         return 0;
1323                 }
1324         }
1325         if (sdev->device_blocked)
1326                 return 0;
1327
1328         return 1;
1329 }
1330
1331 /*
1332  * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1333  * return 0. We must end up running the queue again whenever 0 is
1334  * returned, else IO can hang.
1335  *
1336  * Called with host_lock held.
1337  */
1338 static inline int scsi_host_queue_ready(struct request_queue *q,
1339                                    struct Scsi_Host *shost,
1340                                    struct scsi_device *sdev)
1341 {
1342         if (scsi_host_in_recovery(shost))
1343                 return 0;
1344         if (shost->host_busy == 0 && shost->host_blocked) {
1345                 /*
1346                  * unblock after host_blocked iterates to zero
1347                  */
1348                 if (--shost->host_blocked == 0) {
1349                         SCSI_LOG_MLQUEUE(3,
1350                                 printk("scsi%d unblocking host at zero depth\n",
1351                                         shost->host_no));
1352                 } else {
1353                         blk_plug_device(q);
1354                         return 0;
1355                 }
1356         }
1357         if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
1358             shost->host_blocked || shost->host_self_blocked) {
1359                 if (list_empty(&sdev->starved_entry))
1360                         list_add_tail(&sdev->starved_entry, &shost->starved_list);
1361                 return 0;
1362         }
1363
1364         /* We're OK to process the command, so we can't be starved */
1365         if (!list_empty(&sdev->starved_entry))
1366                 list_del_init(&sdev->starved_entry);
1367
1368         return 1;
1369 }
1370
1371 /*
1372  * Kill a request for a dead device
1373  */
1374 static void scsi_kill_request(struct request *req, request_queue_t *q)
1375 {
1376         struct scsi_cmnd *cmd = req->special;
1377
1378         blkdev_dequeue_request(req);
1379
1380         if (unlikely(cmd == NULL)) {
1381                 printk(KERN_CRIT "impossible request in %s.\n",
1382                                  __FUNCTION__);
1383                 BUG();
1384         }
1385
1386         scsi_init_cmd_errh(cmd);
1387         cmd->result = DID_NO_CONNECT << 16;
1388         atomic_inc(&cmd->device->iorequest_cnt);
1389         __scsi_done(cmd);
1390 }
1391
1392 /*
1393  * Function:    scsi_request_fn()
1394  *
1395  * Purpose:     Main strategy routine for SCSI.
1396  *
1397  * Arguments:   q       - Pointer to actual queue.
1398  *
1399  * Returns:     Nothing
1400  *
1401  * Lock status: IO request lock assumed to be held when called.
1402  */
1403 static void scsi_request_fn(struct request_queue *q)
1404 {
1405         struct scsi_device *sdev = q->queuedata;
1406         struct Scsi_Host *shost;
1407         struct scsi_cmnd *cmd;
1408         struct request *req;
1409
1410         if (!sdev) {
1411                 printk("scsi: killing requests for dead queue\n");
1412                 while ((req = elv_next_request(q)) != NULL)
1413                         scsi_kill_request(req, q);
1414                 return;
1415         }
1416
1417         if(!get_device(&sdev->sdev_gendev))
1418                 /* We must be tearing the block queue down already */
1419                 return;
1420
1421         /*
1422          * To start with, we keep looping until the queue is empty, or until
1423          * the host is no longer able to accept any more requests.
1424          */
1425         shost = sdev->host;
1426         while (!blk_queue_plugged(q)) {
1427                 int rtn;
1428                 /*
1429                  * get next queueable request.  We do this early to make sure
1430                  * that the request is fully prepared even if we cannot 
1431                  * accept it.
1432                  */
1433                 req = elv_next_request(q);
1434                 if (!req || !scsi_dev_queue_ready(q, sdev))
1435                         break;
1436
1437                 if (unlikely(!scsi_device_online(sdev))) {
1438                         printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to offline device\n",
1439                                sdev->host->host_no, sdev->id, sdev->lun);
1440                         scsi_kill_request(req, q);
1441                         continue;
1442                 }
1443
1444
1445                 /*
1446                  * Remove the request from the request list.
1447                  */
1448                 if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1449                         blkdev_dequeue_request(req);
1450                 sdev->device_busy++;
1451
1452                 spin_unlock(q->queue_lock);
1453                 cmd = req->special;
1454                 if (unlikely(cmd == NULL)) {
1455                         printk(KERN_CRIT "impossible request in %s.\n"
1456                                          "please mail a stack trace to "
1457                                          "linux-scsi@vger.kernel.org",
1458                                          __FUNCTION__);
1459                         BUG();
1460                 }
1461                 spin_lock(shost->host_lock);
1462
1463                 if (!scsi_host_queue_ready(q, shost, sdev))
1464                         goto not_ready;
1465                 if (sdev->single_lun) {
1466                         if (scsi_target(sdev)->starget_sdev_user &&
1467                             scsi_target(sdev)->starget_sdev_user != sdev)
1468                                 goto not_ready;
1469                         scsi_target(sdev)->starget_sdev_user = sdev;
1470                 }
1471                 shost->host_busy++;
1472
1473                 /*
1474                  * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1475                  *              take the lock again.
1476                  */
1477                 spin_unlock_irq(shost->host_lock);
1478
1479                 /*
1480                  * Finally, initialize any error handling parameters, and set up
1481                  * the timers for timeouts.
1482                  */
1483                 scsi_init_cmd_errh(cmd);
1484
1485                 /*
1486                  * Dispatch the command to the low-level driver.
1487                  */
1488                 rtn = scsi_dispatch_cmd(cmd);
1489                 spin_lock_irq(q->queue_lock);
1490                 if(rtn) {
1491                         /* we're refusing the command; because of
1492                          * the way locks get dropped, we need to 
1493                          * check here if plugging is required */
1494                         if(sdev->device_busy == 0)
1495                                 blk_plug_device(q);
1496
1497                         break;
1498                 }
1499         }
1500
1501         goto out;
1502
1503  not_ready:
1504         spin_unlock_irq(shost->host_lock);
1505
1506         /*
1507          * lock q, handle tag, requeue req, and decrement device_busy. We
1508          * must return with queue_lock held.
1509          *
1510          * Decrementing device_busy without checking it is OK, as all such
1511          * cases (host limits or settings) should run the queue at some
1512          * later time.
1513          */
1514         spin_lock_irq(q->queue_lock);
1515         blk_requeue_request(q, req);
1516         sdev->device_busy--;
1517         if(sdev->device_busy == 0)
1518                 blk_plug_device(q);
1519  out:
1520         /* must be careful here...if we trigger the ->remove() function
1521          * we cannot be holding the q lock */
1522         spin_unlock_irq(q->queue_lock);
1523         put_device(&sdev->sdev_gendev);
1524         spin_lock_irq(q->queue_lock);
1525 }
1526
1527 u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1528 {
1529         struct device *host_dev;
1530         u64 bounce_limit = 0xffffffff;
1531
1532         if (shost->unchecked_isa_dma)
1533                 return BLK_BOUNCE_ISA;
1534         /*
1535          * Platforms with virtual-DMA translation
1536          * hardware have no practical limit.
1537          */
1538         if (!PCI_DMA_BUS_IS_PHYS)
1539                 return BLK_BOUNCE_ANY;
1540
1541         host_dev = scsi_get_device(shost);
1542         if (host_dev && host_dev->dma_mask)
1543                 bounce_limit = *host_dev->dma_mask;
1544
1545         return bounce_limit;
1546 }
1547 EXPORT_SYMBOL(scsi_calculate_bounce_limit);
1548
1549 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1550 {
1551         struct Scsi_Host *shost = sdev->host;
1552         struct request_queue *q;
1553
1554         q = blk_init_queue(scsi_request_fn, NULL);
1555         if (!q)
1556                 return NULL;
1557
1558         blk_queue_prep_rq(q, scsi_prep_fn);
1559
1560         blk_queue_max_hw_segments(q, shost->sg_tablesize);
1561         blk_queue_max_phys_segments(q, SCSI_MAX_PHYS_SEGMENTS);
1562         blk_queue_max_sectors(q, shost->max_sectors);
1563         blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1564         blk_queue_segment_boundary(q, shost->dma_boundary);
1565         blk_queue_issue_flush_fn(q, scsi_issue_flush_fn);
1566
1567         /*
1568          * ordered tags are superior to flush ordering
1569          */
1570         if (shost->ordered_tag)
1571                 blk_queue_ordered(q, QUEUE_ORDERED_TAG);
1572         else if (shost->ordered_flush) {
1573                 blk_queue_ordered(q, QUEUE_ORDERED_FLUSH);
1574                 q->prepare_flush_fn = scsi_prepare_flush_fn;
1575                 q->end_flush_fn = scsi_end_flush_fn;
1576         }
1577
1578         if (!shost->use_clustering)
1579                 clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
1580         return q;
1581 }
1582
1583 void scsi_free_queue(struct request_queue *q)
1584 {
1585         blk_cleanup_queue(q);
1586 }
1587
1588 /*
1589  * Function:    scsi_block_requests()
1590  *
1591  * Purpose:     Utility function used by low-level drivers to prevent further
1592  *              commands from being queued to the device.
1593  *
1594  * Arguments:   shost       - Host in question
1595  *
1596  * Returns:     Nothing
1597  *
1598  * Lock status: No locks are assumed held.
1599  *
1600  * Notes:       There is no timer nor any other means by which the requests
1601  *              get unblocked other than the low-level driver calling
1602  *              scsi_unblock_requests().
1603  */
1604 void scsi_block_requests(struct Scsi_Host *shost)
1605 {
1606         shost->host_self_blocked = 1;
1607 }
1608 EXPORT_SYMBOL(scsi_block_requests);
1609
1610 /*
1611  * Function:    scsi_unblock_requests()
1612  *
1613  * Purpose:     Utility function used by low-level drivers to allow further
1614  *              commands from being queued to the device.
1615  *
1616  * Arguments:   shost       - Host in question
1617  *
1618  * Returns:     Nothing
1619  *
1620  * Lock status: No locks are assumed held.
1621  *
1622  * Notes:       There is no timer nor any other means by which the requests
1623  *              get unblocked other than the low-level driver calling
1624  *              scsi_unblock_requests().
1625  *
1626  *              This is done as an API function so that changes to the
1627  *              internals of the scsi mid-layer won't require wholesale
1628  *              changes to drivers that use this feature.
1629  */
1630 void scsi_unblock_requests(struct Scsi_Host *shost)
1631 {
1632         shost->host_self_blocked = 0;
1633         scsi_run_host_queues(shost);
1634 }
1635 EXPORT_SYMBOL(scsi_unblock_requests);
1636
1637 int __init scsi_init_queue(void)
1638 {
1639         int i;
1640
1641         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1642                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1643                 int size = sgp->size * sizeof(struct scatterlist);
1644
1645                 sgp->slab = kmem_cache_create(sgp->name, size, 0,
1646                                 SLAB_HWCACHE_ALIGN, NULL, NULL);
1647                 if (!sgp->slab) {
1648                         printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1649                                         sgp->name);
1650                 }
1651
1652                 sgp->pool = mempool_create(SG_MEMPOOL_SIZE,
1653                                 mempool_alloc_slab, mempool_free_slab,
1654                                 sgp->slab);
1655                 if (!sgp->pool) {
1656                         printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1657                                         sgp->name);
1658                 }
1659         }
1660
1661         return 0;
1662 }
1663
1664 void scsi_exit_queue(void)
1665 {
1666         int i;
1667
1668         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1669                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1670                 mempool_destroy(sgp->pool);
1671                 kmem_cache_destroy(sgp->slab);
1672         }
1673 }
1674 /**
1675  *      scsi_mode_sense - issue a mode sense, falling back from 10 to 
1676  *              six bytes if necessary.
1677  *      @sdev:  SCSI device to be queried
1678  *      @dbd:   set if mode sense will allow block descriptors to be returned
1679  *      @modepage: mode page being requested
1680  *      @buffer: request buffer (may not be smaller than eight bytes)
1681  *      @len:   length of request buffer.
1682  *      @timeout: command timeout
1683  *      @retries: number of retries before failing
1684  *      @data: returns a structure abstracting the mode header data
1685  *      @sense: place to put sense data (or NULL if no sense to be collected).
1686  *              must be SCSI_SENSE_BUFFERSIZE big.
1687  *
1688  *      Returns zero if unsuccessful, or the header offset (either 4
1689  *      or 8 depending on whether a six or ten byte command was
1690  *      issued) if successful.
1691  **/
1692 int
1693 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
1694                   unsigned char *buffer, int len, int timeout, int retries,
1695                   struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr) {
1696         unsigned char cmd[12];
1697         int use_10_for_ms;
1698         int header_length;
1699         int result;
1700         struct scsi_sense_hdr my_sshdr;
1701
1702         memset(data, 0, sizeof(*data));
1703         memset(&cmd[0], 0, 12);
1704         cmd[1] = dbd & 0x18;    /* allows DBD and LLBA bits */
1705         cmd[2] = modepage;
1706
1707         /* caller might not be interested in sense, but we need it */
1708         if (!sshdr)
1709                 sshdr = &my_sshdr;
1710
1711  retry:
1712         use_10_for_ms = sdev->use_10_for_ms;
1713
1714         if (use_10_for_ms) {
1715                 if (len < 8)
1716                         len = 8;
1717
1718                 cmd[0] = MODE_SENSE_10;
1719                 cmd[8] = len;
1720                 header_length = 8;
1721         } else {
1722                 if (len < 4)
1723                         len = 4;
1724
1725                 cmd[0] = MODE_SENSE;
1726                 cmd[4] = len;
1727                 header_length = 4;
1728         }
1729
1730         memset(buffer, 0, len);
1731
1732         result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
1733                                   sshdr, timeout, retries);
1734
1735         /* This code looks awful: what it's doing is making sure an
1736          * ILLEGAL REQUEST sense return identifies the actual command
1737          * byte as the problem.  MODE_SENSE commands can return
1738          * ILLEGAL REQUEST if the code page isn't supported */
1739
1740         if (use_10_for_ms && !scsi_status_is_good(result) &&
1741             (driver_byte(result) & DRIVER_SENSE)) {
1742                 if (scsi_sense_valid(sshdr)) {
1743                         if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
1744                             (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
1745                                 /* 
1746                                  * Invalid command operation code
1747                                  */
1748                                 sdev->use_10_for_ms = 0;
1749                                 goto retry;
1750                         }
1751                 }
1752         }
1753
1754         if(scsi_status_is_good(result)) {
1755                 data->header_length = header_length;
1756                 if(use_10_for_ms) {
1757                         data->length = buffer[0]*256 + buffer[1] + 2;
1758                         data->medium_type = buffer[2];
1759                         data->device_specific = buffer[3];
1760                         data->longlba = buffer[4] & 0x01;
1761                         data->block_descriptor_length = buffer[6]*256
1762                                 + buffer[7];
1763                 } else {
1764                         data->length = buffer[0] + 1;
1765                         data->medium_type = buffer[1];
1766                         data->device_specific = buffer[2];
1767                         data->block_descriptor_length = buffer[3];
1768                 }
1769         }
1770
1771         return result;
1772 }
1773 EXPORT_SYMBOL(scsi_mode_sense);
1774
1775 int
1776 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries)
1777 {
1778         char cmd[] = {
1779                 TEST_UNIT_READY, 0, 0, 0, 0, 0,
1780         };
1781         struct scsi_sense_hdr sshdr;
1782         int result;
1783         
1784         result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, &sshdr,
1785                                   timeout, retries);
1786
1787         if ((driver_byte(result) & DRIVER_SENSE) && sdev->removable) {
1788
1789                 if ((scsi_sense_valid(&sshdr)) &&
1790                     ((sshdr.sense_key == UNIT_ATTENTION) ||
1791                      (sshdr.sense_key == NOT_READY))) {
1792                         sdev->changed = 1;
1793                         result = 0;
1794                 }
1795         }
1796         return result;
1797 }
1798 EXPORT_SYMBOL(scsi_test_unit_ready);
1799
1800 /**
1801  *      scsi_device_set_state - Take the given device through the device
1802  *              state model.
1803  *      @sdev:  scsi device to change the state of.
1804  *      @state: state to change to.
1805  *
1806  *      Returns zero if unsuccessful or an error if the requested 
1807  *      transition is illegal.
1808  **/
1809 int
1810 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
1811 {
1812         enum scsi_device_state oldstate = sdev->sdev_state;
1813
1814         if (state == oldstate)
1815                 return 0;
1816
1817         switch (state) {
1818         case SDEV_CREATED:
1819                 /* There are no legal states that come back to
1820                  * created.  This is the manually initialised start
1821                  * state */
1822                 goto illegal;
1823                         
1824         case SDEV_RUNNING:
1825                 switch (oldstate) {
1826                 case SDEV_CREATED:
1827                 case SDEV_OFFLINE:
1828                 case SDEV_QUIESCE:
1829                 case SDEV_BLOCK:
1830                         break;
1831                 default:
1832                         goto illegal;
1833                 }
1834                 break;
1835
1836         case SDEV_QUIESCE:
1837                 switch (oldstate) {
1838                 case SDEV_RUNNING:
1839                 case SDEV_OFFLINE:
1840                         break;
1841                 default:
1842                         goto illegal;
1843                 }
1844                 break;
1845
1846         case SDEV_OFFLINE:
1847                 switch (oldstate) {
1848                 case SDEV_CREATED:
1849                 case SDEV_RUNNING:
1850                 case SDEV_QUIESCE:
1851                 case SDEV_BLOCK:
1852                         break;
1853                 default:
1854                         goto illegal;
1855                 }
1856                 break;
1857
1858         case SDEV_BLOCK:
1859                 switch (oldstate) {
1860                 case SDEV_CREATED:
1861                 case SDEV_RUNNING:
1862                         break;
1863                 default:
1864                         goto illegal;
1865                 }
1866                 break;
1867
1868         case SDEV_CANCEL:
1869                 switch (oldstate) {
1870                 case SDEV_CREATED:
1871                 case SDEV_RUNNING:
1872                 case SDEV_OFFLINE:
1873                 case SDEV_BLOCK:
1874                         break;
1875                 default:
1876                         goto illegal;
1877                 }
1878                 break;
1879
1880         case SDEV_DEL:
1881                 switch (oldstate) {
1882                 case SDEV_CANCEL:
1883                         break;
1884                 default:
1885                         goto illegal;
1886                 }
1887                 break;
1888
1889         }
1890         sdev->sdev_state = state;
1891         return 0;
1892
1893  illegal:
1894         SCSI_LOG_ERROR_RECOVERY(1, 
1895                                 dev_printk(KERN_ERR, &sdev->sdev_gendev,
1896                                            "Illegal state transition %s->%s\n",
1897                                            scsi_device_state_name(oldstate),
1898                                            scsi_device_state_name(state))
1899                                 );
1900         return -EINVAL;
1901 }
1902 EXPORT_SYMBOL(scsi_device_set_state);
1903
1904 /**
1905  *      scsi_device_quiesce - Block user issued commands.
1906  *      @sdev:  scsi device to quiesce.
1907  *
1908  *      This works by trying to transition to the SDEV_QUIESCE state
1909  *      (which must be a legal transition).  When the device is in this
1910  *      state, only special requests will be accepted, all others will
1911  *      be deferred.  Since special requests may also be requeued requests,
1912  *      a successful return doesn't guarantee the device will be 
1913  *      totally quiescent.
1914  *
1915  *      Must be called with user context, may sleep.
1916  *
1917  *      Returns zero if unsuccessful or an error if not.
1918  **/
1919 int
1920 scsi_device_quiesce(struct scsi_device *sdev)
1921 {
1922         int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
1923         if (err)
1924                 return err;
1925
1926         scsi_run_queue(sdev->request_queue);
1927         while (sdev->device_busy) {
1928                 msleep_interruptible(200);
1929                 scsi_run_queue(sdev->request_queue);
1930         }
1931         return 0;
1932 }
1933 EXPORT_SYMBOL(scsi_device_quiesce);
1934
1935 /**
1936  *      scsi_device_resume - Restart user issued commands to a quiesced device.
1937  *      @sdev:  scsi device to resume.
1938  *
1939  *      Moves the device from quiesced back to running and restarts the
1940  *      queues.
1941  *
1942  *      Must be called with user context, may sleep.
1943  **/
1944 void
1945 scsi_device_resume(struct scsi_device *sdev)
1946 {
1947         if(scsi_device_set_state(sdev, SDEV_RUNNING))
1948                 return;
1949         scsi_run_queue(sdev->request_queue);
1950 }
1951 EXPORT_SYMBOL(scsi_device_resume);
1952
1953 static void
1954 device_quiesce_fn(struct scsi_device *sdev, void *data)
1955 {
1956         scsi_device_quiesce(sdev);
1957 }
1958
1959 void
1960 scsi_target_quiesce(struct scsi_target *starget)
1961 {
1962         starget_for_each_device(starget, NULL, device_quiesce_fn);
1963 }
1964 EXPORT_SYMBOL(scsi_target_quiesce);
1965
1966 static void
1967 device_resume_fn(struct scsi_device *sdev, void *data)
1968 {
1969         scsi_device_resume(sdev);
1970 }
1971
1972 void
1973 scsi_target_resume(struct scsi_target *starget)
1974 {
1975         starget_for_each_device(starget, NULL, device_resume_fn);
1976 }
1977 EXPORT_SYMBOL(scsi_target_resume);
1978
1979 /**
1980  * scsi_internal_device_block - internal function to put a device
1981  *                              temporarily into the SDEV_BLOCK state
1982  * @sdev:       device to block
1983  *
1984  * Block request made by scsi lld's to temporarily stop all
1985  * scsi commands on the specified device.  Called from interrupt
1986  * or normal process context.
1987  *
1988  * Returns zero if successful or error if not
1989  *
1990  * Notes:       
1991  *      This routine transitions the device to the SDEV_BLOCK state
1992  *      (which must be a legal transition).  When the device is in this
1993  *      state, all commands are deferred until the scsi lld reenables
1994  *      the device with scsi_device_unblock or device_block_tmo fires.
1995  *      This routine assumes the host_lock is held on entry.
1996  **/
1997 int
1998 scsi_internal_device_block(struct scsi_device *sdev)
1999 {
2000         request_queue_t *q = sdev->request_queue;
2001         unsigned long flags;
2002         int err = 0;
2003
2004         err = scsi_device_set_state(sdev, SDEV_BLOCK);
2005         if (err)
2006                 return err;
2007
2008         /* 
2009          * The device has transitioned to SDEV_BLOCK.  Stop the
2010          * block layer from calling the midlayer with this device's
2011          * request queue. 
2012          */
2013         spin_lock_irqsave(q->queue_lock, flags);
2014         blk_stop_queue(q);
2015         spin_unlock_irqrestore(q->queue_lock, flags);
2016
2017         return 0;
2018 }
2019 EXPORT_SYMBOL_GPL(scsi_internal_device_block);
2020  
2021 /**
2022  * scsi_internal_device_unblock - resume a device after a block request
2023  * @sdev:       device to resume
2024  *
2025  * Called by scsi lld's or the midlayer to restart the device queue
2026  * for the previously suspended scsi device.  Called from interrupt or
2027  * normal process context.
2028  *
2029  * Returns zero if successful or error if not.
2030  *
2031  * Notes:       
2032  *      This routine transitions the device to the SDEV_RUNNING state
2033  *      (which must be a legal transition) allowing the midlayer to
2034  *      goose the queue for this device.  This routine assumes the 
2035  *      host_lock is held upon entry.
2036  **/
2037 int
2038 scsi_internal_device_unblock(struct scsi_device *sdev)
2039 {
2040         request_queue_t *q = sdev->request_queue; 
2041         int err;
2042         unsigned long flags;
2043         
2044         /* 
2045          * Try to transition the scsi device to SDEV_RUNNING
2046          * and goose the device queue if successful.  
2047          */
2048         err = scsi_device_set_state(sdev, SDEV_RUNNING);
2049         if (err)
2050                 return err;
2051
2052         spin_lock_irqsave(q->queue_lock, flags);
2053         blk_start_queue(q);
2054         spin_unlock_irqrestore(q->queue_lock, flags);
2055
2056         return 0;
2057 }
2058 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
2059
2060 static void
2061 device_block(struct scsi_device *sdev, void *data)
2062 {
2063         scsi_internal_device_block(sdev);
2064 }
2065
2066 static int
2067 target_block(struct device *dev, void *data)
2068 {
2069         if (scsi_is_target_device(dev))
2070                 starget_for_each_device(to_scsi_target(dev), NULL,
2071                                         device_block);
2072         return 0;
2073 }
2074
2075 void
2076 scsi_target_block(struct device *dev)
2077 {
2078         if (scsi_is_target_device(dev))
2079                 starget_for_each_device(to_scsi_target(dev), NULL,
2080                                         device_block);
2081         else
2082                 device_for_each_child(dev, NULL, target_block);
2083 }
2084 EXPORT_SYMBOL_GPL(scsi_target_block);
2085
2086 static void
2087 device_unblock(struct scsi_device *sdev, void *data)
2088 {
2089         scsi_internal_device_unblock(sdev);
2090 }
2091
2092 static int
2093 target_unblock(struct device *dev, void *data)
2094 {
2095         if (scsi_is_target_device(dev))
2096                 starget_for_each_device(to_scsi_target(dev), NULL,
2097                                         device_unblock);
2098         return 0;
2099 }
2100
2101 void
2102 scsi_target_unblock(struct device *dev)
2103 {
2104         if (scsi_is_target_device(dev))
2105                 starget_for_each_device(to_scsi_target(dev), NULL,
2106                                         device_unblock);
2107         else
2108                 device_for_each_child(dev, NULL, target_unblock);
2109 }
2110 EXPORT_SYMBOL_GPL(scsi_target_unblock);