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