Merge branch 'misc' of master.kernel.org:/pub/scm/linux/kernel/git/galak/powerpc...
[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 #include <linux/hardirq.h>
20
21 #include <scsi/scsi.h>
22 #include <scsi/scsi_dbg.h>
23 #include <scsi/scsi_device.h>
24 #include <scsi/scsi_driver.h>
25 #include <scsi/scsi_eh.h>
26 #include <scsi/scsi_host.h>
27 #include <scsi/scsi_request.h>
28
29 #include "scsi_priv.h"
30 #include "scsi_logging.h"
31
32
33 #define SG_MEMPOOL_NR           (sizeof(scsi_sg_pools)/sizeof(struct scsi_host_sg_pool))
34 #define SG_MEMPOOL_SIZE         32
35
36 struct scsi_host_sg_pool {
37         size_t          size;
38         char            *name; 
39         kmem_cache_t    *slab;
40         mempool_t       *pool;
41 };
42
43 #if (SCSI_MAX_PHYS_SEGMENTS < 32)
44 #error SCSI_MAX_PHYS_SEGMENTS is too small
45 #endif
46
47 #define SP(x) { x, "sgpool-" #x } 
48 static struct scsi_host_sg_pool scsi_sg_pools[] = {
49         SP(8),
50         SP(16),
51         SP(32),
52 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
53         SP(64),
54 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
55         SP(128),
56 #if (SCSI_MAX_PHYS_SEGMENTS > 128)
57         SP(256),
58 #if (SCSI_MAX_PHYS_SEGMENTS > 256)
59 #error SCSI_MAX_PHYS_SEGMENTS is too large
60 #endif
61 #endif
62 #endif
63 #endif
64 };      
65 #undef SP
66
67 static void scsi_run_queue(struct request_queue *q);
68
69 /*
70  * Function:    scsi_unprep_request()
71  *
72  * Purpose:     Remove all preparation done for a request, including its
73  *              associated scsi_cmnd, so that it can be requeued.
74  *
75  * Arguments:   req     - request to unprepare
76  *
77  * Lock status: Assumed that no locks are held upon entry.
78  *
79  * Returns:     Nothing.
80  */
81 static void scsi_unprep_request(struct request *req)
82 {
83         struct scsi_cmnd *cmd = req->special;
84
85         req->flags &= ~REQ_DONTPREP;
86         req->special = (req->flags & REQ_SPECIAL) ? cmd->sc_request : NULL;
87
88         scsi_put_command(cmd);
89 }
90
91 /*
92  * Function:    scsi_queue_insert()
93  *
94  * Purpose:     Insert a command in the midlevel queue.
95  *
96  * Arguments:   cmd    - command that we are adding to queue.
97  *              reason - why we are inserting command to queue.
98  *
99  * Lock status: Assumed that lock is not held upon entry.
100  *
101  * Returns:     Nothing.
102  *
103  * Notes:       We do this for one of two cases.  Either the host is busy
104  *              and it cannot accept any more commands for the time being,
105  *              or the device returned QUEUE_FULL and can accept no more
106  *              commands.
107  * Notes:       This could be called either from an interrupt context or a
108  *              normal process context.
109  */
110 int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
111 {
112         struct Scsi_Host *host = cmd->device->host;
113         struct scsi_device *device = cmd->device;
114         struct request_queue *q = device->request_queue;
115         unsigned long flags;
116
117         SCSI_LOG_MLQUEUE(1,
118                  printk("Inserting command %p into mlqueue\n", cmd));
119
120         /*
121          * Set the appropriate busy bit for the device/host.
122          *
123          * If the host/device isn't busy, assume that something actually
124          * completed, and that we should be able to queue a command now.
125          *
126          * Note that the prior mid-layer assumption that any host could
127          * always queue at least one command is now broken.  The mid-layer
128          * will implement a user specifiable stall (see
129          * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
130          * if a command is requeued with no other commands outstanding
131          * either for the device or for the host.
132          */
133         if (reason == SCSI_MLQUEUE_HOST_BUSY)
134                 host->host_blocked = host->max_host_blocked;
135         else if (reason == SCSI_MLQUEUE_DEVICE_BUSY)
136                 device->device_blocked = device->max_device_blocked;
137
138         /*
139          * Decrement the counters, since these commands are no longer
140          * active on the host/device.
141          */
142         scsi_device_unbusy(device);
143
144         /*
145          * Requeue this command.  It will go before all other commands
146          * that are already in the queue.
147          *
148          * NOTE: there is magic here about the way the queue is plugged if
149          * we have no outstanding commands.
150          * 
151          * Although we *don't* plug the queue, we call the request
152          * function.  The SCSI request function detects the blocked condition
153          * and plugs the queue appropriately.
154          */
155         spin_lock_irqsave(q->queue_lock, flags);
156         blk_requeue_request(q, cmd->request);
157         spin_unlock_irqrestore(q->queue_lock, flags);
158
159         scsi_run_queue(q);
160
161         return 0;
162 }
163
164 /*
165  * Function:    scsi_do_req
166  *
167  * Purpose:     Queue a SCSI request
168  *
169  * Arguments:   sreq      - command descriptor.
170  *              cmnd      - actual SCSI command to be performed.
171  *              buffer    - data buffer.
172  *              bufflen   - size of data buffer.
173  *              done      - completion function to be run.
174  *              timeout   - how long to let it run before timeout.
175  *              retries   - number of retries we allow.
176  *
177  * Lock status: No locks held upon entry.
178  *
179  * Returns:     Nothing.
180  *
181  * Notes:       This function is only used for queueing requests for things
182  *              like ioctls and character device requests - this is because
183  *              we essentially just inject a request into the queue for the
184  *              device.
185  *
186  *              In order to support the scsi_device_quiesce function, we
187  *              now inject requests on the *head* of the device queue
188  *              rather than the tail.
189  */
190 void scsi_do_req(struct scsi_request *sreq, const void *cmnd,
191                  void *buffer, unsigned bufflen,
192                  void (*done)(struct scsi_cmnd *),
193                  int timeout, int retries)
194 {
195         /*
196          * If the upper level driver is reusing these things, then
197          * we should release the low-level block now.  Another one will
198          * be allocated later when this request is getting queued.
199          */
200         __scsi_release_request(sreq);
201
202         /*
203          * Our own function scsi_done (which marks the host as not busy,
204          * disables the timeout counter, etc) will be called by us or by the
205          * scsi_hosts[host].queuecommand() function needs to also call
206          * the completion function for the high level driver.
207          */
208         memcpy(sreq->sr_cmnd, cmnd, sizeof(sreq->sr_cmnd));
209         sreq->sr_bufflen = bufflen;
210         sreq->sr_buffer = buffer;
211         sreq->sr_allowed = retries;
212         sreq->sr_done = done;
213         sreq->sr_timeout_per_command = timeout;
214
215         if (sreq->sr_cmd_len == 0)
216                 sreq->sr_cmd_len = COMMAND_SIZE(sreq->sr_cmnd[0]);
217
218         /*
219          * head injection *required* here otherwise quiesce won't work
220          *
221          * Because users of this function are apt to reuse requests with no
222          * modification, we have to sanitise the request flags here
223          */
224         sreq->sr_request->flags &= ~REQ_DONTPREP;
225         blk_insert_request(sreq->sr_device->request_queue, sreq->sr_request,
226                            1, sreq);
227 }
228 EXPORT_SYMBOL(scsi_do_req);
229
230 /**
231  * scsi_execute - insert request and wait for the result
232  * @sdev:       scsi device
233  * @cmd:        scsi command
234  * @data_direction: data direction
235  * @buffer:     data buffer
236  * @bufflen:    len of buffer
237  * @sense:      optional sense buffer
238  * @timeout:    request timeout in seconds
239  * @retries:    number of times to retry request
240  * @flags:      or into request flags;
241  *
242  * returns the req->errors value which is the the scsi_cmnd result
243  * field.
244  **/
245 int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
246                  int data_direction, void *buffer, unsigned bufflen,
247                  unsigned char *sense, int timeout, int retries, int flags)
248 {
249         struct request *req;
250         int write = (data_direction == DMA_TO_DEVICE);
251         int ret = DRIVER_ERROR << 24;
252
253         req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
254
255         if (bufflen &&  blk_rq_map_kern(sdev->request_queue, req,
256                                         buffer, bufflen, __GFP_WAIT))
257                 goto out;
258
259         req->cmd_len = COMMAND_SIZE(cmd[0]);
260         memcpy(req->cmd, cmd, req->cmd_len);
261         req->sense = sense;
262         req->sense_len = 0;
263         req->retries = retries;
264         req->timeout = timeout;
265         req->flags |= flags | REQ_BLOCK_PC | REQ_SPECIAL | REQ_QUIET;
266
267         /*
268          * head injection *required* here otherwise quiesce won't work
269          */
270         blk_execute_rq(req->q, NULL, req, 1);
271
272         ret = req->errors;
273  out:
274         blk_put_request(req);
275
276         return ret;
277 }
278 EXPORT_SYMBOL(scsi_execute);
279
280
281 int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
282                      int data_direction, void *buffer, unsigned bufflen,
283                      struct scsi_sense_hdr *sshdr, int timeout, int retries)
284 {
285         char *sense = NULL;
286         int result;
287         
288         if (sshdr) {
289                 sense = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
290                 if (!sense)
291                         return DRIVER_ERROR << 24;
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, int uptodate)
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  * @cmd_len:    length of scsi cdb
440  * @data_direction: data direction
441  * @buffer:     data buffer (this can be a kernel buffer or scatterlist)
442  * @bufflen:    len of buffer
443  * @use_sg:     if buffer is a scatterlist this is the number of elements
444  * @timeout:    request timeout in seconds
445  * @retries:    number of times to retry request
446  * @flags:      or into request flags
447  **/
448 int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
449                        int cmd_len, int data_direction, void *buffer, unsigned bufflen,
450                        int use_sg, int timeout, int retries, void *privdata,
451                        void (*done)(void *, char *, int, int), gfp_t gfp)
452 {
453         struct request *req;
454         struct scsi_io_context *sioc;
455         int err = 0;
456         int write = (data_direction == DMA_TO_DEVICE);
457
458         sioc = kmem_cache_alloc(scsi_io_context_cache, gfp);
459         if (!sioc)
460                 return DRIVER_ERROR << 24;
461         memset(sioc, 0, sizeof(*sioc));
462
463         req = blk_get_request(sdev->request_queue, write, gfp);
464         if (!req)
465                 goto free_sense;
466         req->flags |= REQ_BLOCK_PC | REQ_QUIET;
467
468         if (use_sg)
469                 err = scsi_req_map_sg(req, buffer, use_sg, bufflen, gfp);
470         else if (bufflen)
471                 err = blk_rq_map_kern(req->q, req, buffer, bufflen, gfp);
472
473         if (err)
474                 goto free_req;
475
476         req->cmd_len = cmd_len;
477         memcpy(req->cmd, cmd, req->cmd_len);
478         req->sense = sioc->sense;
479         req->sense_len = 0;
480         req->timeout = timeout;
481         req->retries = retries;
482         req->end_io_data = sioc;
483
484         sioc->data = privdata;
485         sioc->done = done;
486
487         blk_execute_rq_nowait(req->q, NULL, req, 1, scsi_end_async);
488         return 0;
489
490 free_req:
491         blk_put_request(req);
492 free_sense:
493         kfree(sioc);
494         return DRIVER_ERROR << 24;
495 }
496 EXPORT_SYMBOL_GPL(scsi_execute_async);
497
498 /*
499  * Function:    scsi_init_cmd_errh()
500  *
501  * Purpose:     Initialize cmd fields related to error handling.
502  *
503  * Arguments:   cmd     - command that is ready to be queued.
504  *
505  * Returns:     Nothing
506  *
507  * Notes:       This function has the job of initializing a number of
508  *              fields related to error handling.   Typically this will
509  *              be called once for each command, as required.
510  */
511 static int scsi_init_cmd_errh(struct scsi_cmnd *cmd)
512 {
513         cmd->serial_number = 0;
514
515         memset(cmd->sense_buffer, 0, sizeof cmd->sense_buffer);
516
517         if (cmd->cmd_len == 0)
518                 cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);
519
520         /*
521          * We need saved copies of a number of fields - this is because
522          * error handling may need to overwrite these with different values
523          * to run different commands, and once error handling is complete,
524          * we will need to restore these values prior to running the actual
525          * command.
526          */
527         cmd->old_use_sg = cmd->use_sg;
528         cmd->old_cmd_len = cmd->cmd_len;
529         cmd->sc_old_data_direction = cmd->sc_data_direction;
530         cmd->old_underflow = cmd->underflow;
531         memcpy(cmd->data_cmnd, cmd->cmnd, sizeof(cmd->cmnd));
532         cmd->buffer = cmd->request_buffer;
533         cmd->bufflen = cmd->request_bufflen;
534
535         return 1;
536 }
537
538 /*
539  * Function:   scsi_setup_cmd_retry()
540  *
541  * Purpose:    Restore the command state for a retry
542  *
543  * Arguments:  cmd      - command to be restored
544  *
545  * Returns:    Nothing
546  *
547  * Notes:      Immediately prior to retrying a command, we need
548  *             to restore certain fields that we saved above.
549  */
550 void scsi_setup_cmd_retry(struct scsi_cmnd *cmd)
551 {
552         memcpy(cmd->cmnd, cmd->data_cmnd, sizeof(cmd->data_cmnd));
553         cmd->request_buffer = cmd->buffer;
554         cmd->request_bufflen = cmd->bufflen;
555         cmd->use_sg = cmd->old_use_sg;
556         cmd->cmd_len = cmd->old_cmd_len;
557         cmd->sc_data_direction = cmd->sc_old_data_direction;
558         cmd->underflow = cmd->old_underflow;
559 }
560
561 void scsi_device_unbusy(struct scsi_device *sdev)
562 {
563         struct Scsi_Host *shost = sdev->host;
564         unsigned long flags;
565
566         spin_lock_irqsave(shost->host_lock, flags);
567         shost->host_busy--;
568         if (unlikely(scsi_host_in_recovery(shost) &&
569                      shost->host_failed))
570                 scsi_eh_wakeup(shost);
571         spin_unlock(shost->host_lock);
572         spin_lock(sdev->request_queue->queue_lock);
573         sdev->device_busy--;
574         spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
575 }
576
577 /*
578  * Called for single_lun devices on IO completion. Clear starget_sdev_user,
579  * and call blk_run_queue for all the scsi_devices on the target -
580  * including current_sdev first.
581  *
582  * Called with *no* scsi locks held.
583  */
584 static void scsi_single_lun_run(struct scsi_device *current_sdev)
585 {
586         struct Scsi_Host *shost = current_sdev->host;
587         struct scsi_device *sdev, *tmp;
588         struct scsi_target *starget = scsi_target(current_sdev);
589         unsigned long flags;
590
591         spin_lock_irqsave(shost->host_lock, flags);
592         starget->starget_sdev_user = NULL;
593         spin_unlock_irqrestore(shost->host_lock, flags);
594
595         /*
596          * Call blk_run_queue for all LUNs on the target, starting with
597          * current_sdev. We race with others (to set starget_sdev_user),
598          * but in most cases, we will be first. Ideally, each LU on the
599          * target would get some limited time or requests on the target.
600          */
601         blk_run_queue(current_sdev->request_queue);
602
603         spin_lock_irqsave(shost->host_lock, flags);
604         if (starget->starget_sdev_user)
605                 goto out;
606         list_for_each_entry_safe(sdev, tmp, &starget->devices,
607                         same_target_siblings) {
608                 if (sdev == current_sdev)
609                         continue;
610                 if (scsi_device_get(sdev))
611                         continue;
612
613                 spin_unlock_irqrestore(shost->host_lock, flags);
614                 blk_run_queue(sdev->request_queue);
615                 spin_lock_irqsave(shost->host_lock, flags);
616         
617                 scsi_device_put(sdev);
618         }
619  out:
620         spin_unlock_irqrestore(shost->host_lock, flags);
621 }
622
623 /*
624  * Function:    scsi_run_queue()
625  *
626  * Purpose:     Select a proper request queue to serve next
627  *
628  * Arguments:   q       - last request's queue
629  *
630  * Returns:     Nothing
631  *
632  * Notes:       The previous command was completely finished, start
633  *              a new one if possible.
634  */
635 static void scsi_run_queue(struct request_queue *q)
636 {
637         struct scsi_device *sdev = q->queuedata;
638         struct Scsi_Host *shost = sdev->host;
639         unsigned long flags;
640
641         if (sdev->single_lun)
642                 scsi_single_lun_run(sdev);
643
644         spin_lock_irqsave(shost->host_lock, flags);
645         while (!list_empty(&shost->starved_list) &&
646                !shost->host_blocked && !shost->host_self_blocked &&
647                 !((shost->can_queue > 0) &&
648                   (shost->host_busy >= shost->can_queue))) {
649                 /*
650                  * As long as shost is accepting commands and we have
651                  * starved queues, call blk_run_queue. scsi_request_fn
652                  * drops the queue_lock and can add us back to the
653                  * starved_list.
654                  *
655                  * host_lock protects the starved_list and starved_entry.
656                  * scsi_request_fn must get the host_lock before checking
657                  * or modifying starved_list or starved_entry.
658                  */
659                 sdev = list_entry(shost->starved_list.next,
660                                           struct scsi_device, starved_entry);
661                 list_del_init(&sdev->starved_entry);
662                 spin_unlock_irqrestore(shost->host_lock, flags);
663
664                 blk_run_queue(sdev->request_queue);
665
666                 spin_lock_irqsave(shost->host_lock, flags);
667                 if (unlikely(!list_empty(&sdev->starved_entry)))
668                         /*
669                          * sdev lost a race, and was put back on the
670                          * starved list. This is unlikely but without this
671                          * in theory we could loop forever.
672                          */
673                         break;
674         }
675         spin_unlock_irqrestore(shost->host_lock, flags);
676
677         blk_run_queue(q);
678 }
679
680 /*
681  * Function:    scsi_requeue_command()
682  *
683  * Purpose:     Handle post-processing of completed commands.
684  *
685  * Arguments:   q       - queue to operate on
686  *              cmd     - command that may need to be requeued.
687  *
688  * Returns:     Nothing
689  *
690  * Notes:       After command completion, there may be blocks left
691  *              over which weren't finished by the previous command
692  *              this can be for a number of reasons - the main one is
693  *              I/O errors in the middle of the request, in which case
694  *              we need to request the blocks that come after the bad
695  *              sector.
696  * Notes:       Upon return, cmd is a stale pointer.
697  */
698 static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
699 {
700         struct request *req = cmd->request;
701         unsigned long flags;
702
703         scsi_unprep_request(req);
704         spin_lock_irqsave(q->queue_lock, flags);
705         blk_requeue_request(q, req);
706         spin_unlock_irqrestore(q->queue_lock, flags);
707
708         scsi_run_queue(q);
709 }
710
711 void scsi_next_command(struct scsi_cmnd *cmd)
712 {
713         struct scsi_device *sdev = cmd->device;
714         struct request_queue *q = sdev->request_queue;
715
716         /* need to hold a reference on the device before we let go of the cmd */
717         get_device(&sdev->sdev_gendev);
718
719         scsi_put_command(cmd);
720         scsi_run_queue(q);
721
722         /* ok to remove device now */
723         put_device(&sdev->sdev_gendev);
724 }
725
726 void scsi_run_host_queues(struct Scsi_Host *shost)
727 {
728         struct scsi_device *sdev;
729
730         shost_for_each_device(sdev, shost)
731                 scsi_run_queue(sdev->request_queue);
732 }
733
734 /*
735  * Function:    scsi_end_request()
736  *
737  * Purpose:     Post-processing of completed commands (usually invoked at end
738  *              of upper level post-processing and scsi_io_completion).
739  *
740  * Arguments:   cmd      - command that is complete.
741  *              uptodate - 1 if I/O indicates success, <= 0 for I/O error.
742  *              bytes    - number of bytes of completed I/O
743  *              requeue  - indicates whether we should requeue leftovers.
744  *
745  * Lock status: Assumed that lock is not held upon entry.
746  *
747  * Returns:     cmd if requeue required, NULL otherwise.
748  *
749  * Notes:       This is called for block device requests in order to
750  *              mark some number of sectors as complete.
751  * 
752  *              We are guaranteeing that the request queue will be goosed
753  *              at some point during this call.
754  * Notes:       If cmd was requeued, upon return it will be a stale pointer.
755  */
756 static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int uptodate,
757                                           int bytes, int requeue)
758 {
759         request_queue_t *q = cmd->device->request_queue;
760         struct request *req = cmd->request;
761         unsigned long flags;
762
763         /*
764          * If there are blocks left over at the end, set up the command
765          * to queue the remainder of them.
766          */
767         if (end_that_request_chunk(req, uptodate, bytes)) {
768                 int leftover = (req->hard_nr_sectors << 9);
769
770                 if (blk_pc_request(req))
771                         leftover = req->data_len;
772
773                 /* kill remainder if no retrys */
774                 if (!uptodate && blk_noretry_request(req))
775                         end_that_request_chunk(req, 0, leftover);
776                 else {
777                         if (requeue) {
778                                 /*
779                                  * Bleah.  Leftovers again.  Stick the
780                                  * leftovers in the front of the
781                                  * queue, and goose the queue again.
782                                  */
783                                 scsi_requeue_command(q, cmd);
784                                 cmd = NULL;
785                         }
786                         return cmd;
787                 }
788         }
789
790         add_disk_randomness(req->rq_disk);
791
792         spin_lock_irqsave(q->queue_lock, flags);
793         if (blk_rq_tagged(req))
794                 blk_queue_end_tag(q, req);
795         end_that_request_last(req, uptodate);
796         spin_unlock_irqrestore(q->queue_lock, flags);
797
798         /*
799          * This will goose the queue request function at the end, so we don't
800          * need to worry about launching another command.
801          */
802         scsi_next_command(cmd);
803         return NULL;
804 }
805
806 static struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
807 {
808         struct scsi_host_sg_pool *sgp;
809         struct scatterlist *sgl;
810
811         BUG_ON(!cmd->use_sg);
812
813         switch (cmd->use_sg) {
814         case 1 ... 8:
815                 cmd->sglist_len = 0;
816                 break;
817         case 9 ... 16:
818                 cmd->sglist_len = 1;
819                 break;
820         case 17 ... 32:
821                 cmd->sglist_len = 2;
822                 break;
823 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
824         case 33 ... 64:
825                 cmd->sglist_len = 3;
826                 break;
827 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
828         case 65 ... 128:
829                 cmd->sglist_len = 4;
830                 break;
831 #if (SCSI_MAX_PHYS_SEGMENTS  > 128)
832         case 129 ... 256:
833                 cmd->sglist_len = 5;
834                 break;
835 #endif
836 #endif
837 #endif
838         default:
839                 return NULL;
840         }
841
842         sgp = scsi_sg_pools + cmd->sglist_len;
843         sgl = mempool_alloc(sgp->pool, gfp_mask);
844         return sgl;
845 }
846
847 static void scsi_free_sgtable(struct scatterlist *sgl, int index)
848 {
849         struct scsi_host_sg_pool *sgp;
850
851         BUG_ON(index >= SG_MEMPOOL_NR);
852
853         sgp = scsi_sg_pools + index;
854         mempool_free(sgl, sgp->pool);
855 }
856
857 /*
858  * Function:    scsi_release_buffers()
859  *
860  * Purpose:     Completion processing for block device I/O requests.
861  *
862  * Arguments:   cmd     - command that we are bailing.
863  *
864  * Lock status: Assumed that no lock is held upon entry.
865  *
866  * Returns:     Nothing
867  *
868  * Notes:       In the event that an upper level driver rejects a
869  *              command, we must release resources allocated during
870  *              the __init_io() function.  Primarily this would involve
871  *              the scatter-gather table, and potentially any bounce
872  *              buffers.
873  */
874 static void scsi_release_buffers(struct scsi_cmnd *cmd)
875 {
876         struct request *req = cmd->request;
877
878         /*
879          * Free up any indirection buffers we allocated for DMA purposes. 
880          */
881         if (cmd->use_sg)
882                 scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
883         else if (cmd->request_buffer != req->buffer)
884                 kfree(cmd->request_buffer);
885
886         /*
887          * Zero these out.  They now point to freed memory, and it is
888          * dangerous to hang onto the pointers.
889          */
890         cmd->buffer  = NULL;
891         cmd->bufflen = 0;
892         cmd->request_buffer = NULL;
893         cmd->request_bufflen = 0;
894 }
895
896 /*
897  * Function:    scsi_io_completion()
898  *
899  * Purpose:     Completion processing for block device I/O requests.
900  *
901  * Arguments:   cmd   - command that is finished.
902  *
903  * Lock status: Assumed that no lock is held upon entry.
904  *
905  * Returns:     Nothing
906  *
907  * Notes:       This function is matched in terms of capabilities to
908  *              the function that created the scatter-gather list.
909  *              In other words, if there are no bounce buffers
910  *              (the normal case for most drivers), we don't need
911  *              the logic to deal with cleaning up afterwards.
912  *
913  *              We must do one of several things here:
914  *
915  *              a) Call scsi_end_request.  This will finish off the
916  *                 specified number of sectors.  If we are done, the
917  *                 command block will be released, and the queue
918  *                 function will be goosed.  If we are not done, then
919  *                 scsi_end_request will directly goose the queue.
920  *
921  *              b) We can just use scsi_requeue_command() here.  This would
922  *                 be used if we just wanted to retry, for example.
923  */
924 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
925                         unsigned int block_bytes)
926 {
927         int result = cmd->result;
928         int this_count = cmd->bufflen;
929         request_queue_t *q = cmd->device->request_queue;
930         struct request *req = cmd->request;
931         int clear_errors = 1;
932         struct scsi_sense_hdr sshdr;
933         int sense_valid = 0;
934         int sense_deferred = 0;
935
936         /*
937          * Free up any indirection buffers we allocated for DMA purposes. 
938          * For the case of a READ, we need to copy the data out of the
939          * bounce buffer and into the real buffer.
940          */
941         if (cmd->use_sg)
942                 scsi_free_sgtable(cmd->buffer, cmd->sglist_len);
943         else if (cmd->buffer != req->buffer) {
944                 if (rq_data_dir(req) == READ) {
945                         unsigned long flags;
946                         char *to = bio_kmap_irq(req->bio, &flags);
947                         memcpy(to, cmd->buffer, cmd->bufflen);
948                         bio_kunmap_irq(to, &flags);
949                 }
950                 kfree(cmd->buffer);
951         }
952
953         if (result) {
954                 sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
955                 if (sense_valid)
956                         sense_deferred = scsi_sense_is_deferred(&sshdr);
957         }
958         if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
959                 req->errors = result;
960                 if (result) {
961                         clear_errors = 0;
962                         if (sense_valid && req->sense) {
963                                 /*
964                                  * SG_IO wants current and deferred errors
965                                  */
966                                 int len = 8 + cmd->sense_buffer[7];
967
968                                 if (len > SCSI_SENSE_BUFFERSIZE)
969                                         len = SCSI_SENSE_BUFFERSIZE;
970                                 memcpy(req->sense, cmd->sense_buffer,  len);
971                                 req->sense_len = len;
972                         }
973                 } else
974                         req->data_len = cmd->resid;
975         }
976
977         /*
978          * Zero these out.  They now point to freed memory, and it is
979          * dangerous to hang onto the pointers.
980          */
981         cmd->buffer  = NULL;
982         cmd->bufflen = 0;
983         cmd->request_buffer = NULL;
984         cmd->request_bufflen = 0;
985
986         /*
987          * Next deal with any sectors which we were able to correctly
988          * handle.
989          */
990         if (good_bytes >= 0) {
991                 SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, %d bytes done.\n",
992                                               req->nr_sectors, good_bytes));
993                 SCSI_LOG_HLCOMPLETE(1, printk("use_sg is %d\n", cmd->use_sg));
994
995                 if (clear_errors)
996                         req->errors = 0;
997                 /*
998                  * If multiple sectors are requested in one buffer, then
999                  * they will have been finished off by the first command.
1000                  * If not, then we have a multi-buffer command.
1001                  *
1002                  * If block_bytes != 0, it means we had a medium error
1003                  * of some sort, and that we want to mark some number of
1004                  * sectors as not uptodate.  Thus we want to inhibit
1005                  * requeueing right here - we will requeue down below
1006                  * when we handle the bad sectors.
1007                  */
1008
1009                 /*
1010                  * If the command completed without error, then either
1011                  * finish off the rest of the command, or start a new one.
1012                  */
1013                 if (scsi_end_request(cmd, 1, good_bytes, result == 0) == NULL)
1014                         return;
1015         }
1016         /*
1017          * Now, if we were good little boys and girls, Santa left us a request
1018          * sense buffer.  We can extract information from this, so we
1019          * can choose a block to remap, etc.
1020          */
1021         if (sense_valid && !sense_deferred) {
1022                 switch (sshdr.sense_key) {
1023                 case UNIT_ATTENTION:
1024                         if (cmd->device->removable) {
1025                                 /* detected disc change.  set a bit 
1026                                  * and quietly refuse further access.
1027                                  */
1028                                 cmd->device->changed = 1;
1029                                 scsi_end_request(cmd, 0,
1030                                                 this_count, 1);
1031                                 return;
1032                         } else {
1033                                 /*
1034                                 * Must have been a power glitch, or a
1035                                 * bus reset.  Could not have been a
1036                                 * media change, so we just retry the
1037                                 * request and see what happens.  
1038                                 */
1039                                 scsi_requeue_command(q, cmd);
1040                                 return;
1041                         }
1042                         break;
1043                 case ILLEGAL_REQUEST:
1044                         /*
1045                         * If we had an ILLEGAL REQUEST returned, then we may
1046                         * have performed an unsupported command.  The only
1047                         * thing this should be would be a ten byte read where
1048                         * only a six byte read was supported.  Also, on a
1049                         * system where READ CAPACITY failed, we may have read
1050                         * past the end of the disk.
1051                         */
1052                         if ((cmd->device->use_10_for_rw &&
1053                             sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
1054                             (cmd->cmnd[0] == READ_10 ||
1055                              cmd->cmnd[0] == WRITE_10)) {
1056                                 cmd->device->use_10_for_rw = 0;
1057                                 /*
1058                                  * This will cause a retry with a 6-byte
1059                                  * command.
1060                                  */
1061                                 scsi_requeue_command(q, cmd);
1062                                 result = 0;
1063                         } else {
1064                                 scsi_end_request(cmd, 0, this_count, 1);
1065                                 return;
1066                         }
1067                         break;
1068                 case NOT_READY:
1069                         /*
1070                          * If the device is in the process of becoming ready,
1071                          * retry.
1072                          */
1073                         if (sshdr.asc == 0x04 && sshdr.ascq == 0x01) {
1074                                 scsi_requeue_command(q, cmd);
1075                                 return;
1076                         }
1077                         if (!(req->flags & REQ_QUIET))
1078                                 scmd_printk(KERN_INFO, cmd,
1079                                            "Device not ready.\n");
1080                         scsi_end_request(cmd, 0, this_count, 1);
1081                         return;
1082                 case VOLUME_OVERFLOW:
1083                         if (!(req->flags & REQ_QUIET)) {
1084                                 scmd_printk(KERN_INFO, cmd,
1085                                            "Volume overflow, CDB: ");
1086                                 __scsi_print_command(cmd->data_cmnd);
1087                                 scsi_print_sense("", cmd);
1088                         }
1089                         scsi_end_request(cmd, 0, block_bytes, 1);
1090                         return;
1091                 default:
1092                         break;
1093                 }
1094         }                       /* driver byte != 0 */
1095         if (host_byte(result) == DID_RESET) {
1096                 /*
1097                  * Third party bus reset or reset for error
1098                  * recovery reasons.  Just retry the request
1099                  * and see what happens.  
1100                  */
1101                 scsi_requeue_command(q, cmd);
1102                 return;
1103         }
1104         if (result) {
1105                 if (!(req->flags & REQ_QUIET)) {
1106                         scmd_printk(KERN_INFO, cmd,
1107                                    "SCSI error: return code = 0x%x\n", result);
1108
1109                         if (driver_byte(result) & DRIVER_SENSE)
1110                                 scsi_print_sense("", cmd);
1111                 }
1112                 /*
1113                  * Mark a single buffer as not uptodate.  Queue the remainder.
1114                  * We sometimes get this cruft in the event that a medium error
1115                  * isn't properly reported.
1116                  */
1117                 block_bytes = req->hard_cur_sectors << 9;
1118                 if (!block_bytes)
1119                         block_bytes = req->data_len;
1120                 scsi_end_request(cmd, 0, block_bytes, 1);
1121         }
1122 }
1123 EXPORT_SYMBOL(scsi_io_completion);
1124
1125 /*
1126  * Function:    scsi_init_io()
1127  *
1128  * Purpose:     SCSI I/O initialize function.
1129  *
1130  * Arguments:   cmd   - Command descriptor we wish to initialize
1131  *
1132  * Returns:     0 on success
1133  *              BLKPREP_DEFER if the failure is retryable
1134  *              BLKPREP_KILL if the failure is fatal
1135  */
1136 static int scsi_init_io(struct scsi_cmnd *cmd)
1137 {
1138         struct request     *req = cmd->request;
1139         struct scatterlist *sgpnt;
1140         int                count;
1141
1142         /*
1143          * if this is a rq->data based REQ_BLOCK_PC, setup for a non-sg xfer
1144          */
1145         if ((req->flags & REQ_BLOCK_PC) && !req->bio) {
1146                 cmd->request_bufflen = req->data_len;
1147                 cmd->request_buffer = req->data;
1148                 req->buffer = req->data;
1149                 cmd->use_sg = 0;
1150                 return 0;
1151         }
1152
1153         /*
1154          * we used to not use scatter-gather for single segment request,
1155          * but now we do (it makes highmem I/O easier to support without
1156          * kmapping pages)
1157          */
1158         cmd->use_sg = req->nr_phys_segments;
1159
1160         /*
1161          * if sg table allocation fails, requeue request later.
1162          */
1163         sgpnt = scsi_alloc_sgtable(cmd, GFP_ATOMIC);
1164         if (unlikely(!sgpnt)) {
1165                 scsi_unprep_request(req);
1166                 return BLKPREP_DEFER;
1167         }
1168
1169         cmd->request_buffer = (char *) sgpnt;
1170         cmd->request_bufflen = req->nr_sectors << 9;
1171         if (blk_pc_request(req))
1172                 cmd->request_bufflen = req->data_len;
1173         req->buffer = NULL;
1174
1175         /* 
1176          * Next, walk the list, and fill in the addresses and sizes of
1177          * each segment.
1178          */
1179         count = blk_rq_map_sg(req->q, req, cmd->request_buffer);
1180
1181         /*
1182          * mapped well, send it off
1183          */
1184         if (likely(count <= cmd->use_sg)) {
1185                 cmd->use_sg = count;
1186                 return 0;
1187         }
1188
1189         printk(KERN_ERR "Incorrect number of segments after building list\n");
1190         printk(KERN_ERR "counted %d, received %d\n", count, cmd->use_sg);
1191         printk(KERN_ERR "req nr_sec %lu, cur_nr_sec %u\n", req->nr_sectors,
1192                         req->current_nr_sectors);
1193
1194         /* release the command and kill it */
1195         scsi_release_buffers(cmd);
1196         scsi_put_command(cmd);
1197         return BLKPREP_KILL;
1198 }
1199
1200 static int scsi_issue_flush_fn(request_queue_t *q, struct gendisk *disk,
1201                                sector_t *error_sector)
1202 {
1203         struct scsi_device *sdev = q->queuedata;
1204         struct scsi_driver *drv;
1205
1206         if (sdev->sdev_state != SDEV_RUNNING)
1207                 return -ENXIO;
1208
1209         drv = *(struct scsi_driver **) disk->private_data;
1210         if (drv->issue_flush)
1211                 return drv->issue_flush(&sdev->sdev_gendev, error_sector);
1212
1213         return -EOPNOTSUPP;
1214 }
1215
1216 static void scsi_blk_pc_done(struct scsi_cmnd *cmd)
1217 {
1218         BUG_ON(!blk_pc_request(cmd->request));
1219         /*
1220          * This will complete the whole command with uptodate=1 so
1221          * as far as the block layer is concerned the command completed
1222          * successfully. Since this is a REQ_BLOCK_PC command the
1223          * caller should check the request's errors value
1224          */
1225         scsi_io_completion(cmd, cmd->bufflen, 0);
1226 }
1227
1228 static void scsi_setup_blk_pc_cmnd(struct scsi_cmnd *cmd)
1229 {
1230         struct request *req = cmd->request;
1231
1232         BUG_ON(sizeof(req->cmd) > sizeof(cmd->cmnd));
1233         memcpy(cmd->cmnd, req->cmd, sizeof(cmd->cmnd));
1234         cmd->cmd_len = req->cmd_len;
1235         if (!req->data_len)
1236                 cmd->sc_data_direction = DMA_NONE;
1237         else if (rq_data_dir(req) == WRITE)
1238                 cmd->sc_data_direction = DMA_TO_DEVICE;
1239         else
1240                 cmd->sc_data_direction = DMA_FROM_DEVICE;
1241         
1242         cmd->transfersize = req->data_len;
1243         cmd->allowed = req->retries;
1244         cmd->timeout_per_command = req->timeout;
1245         cmd->done = scsi_blk_pc_done;
1246 }
1247
1248 static int scsi_prep_fn(struct request_queue *q, struct request *req)
1249 {
1250         struct scsi_device *sdev = q->queuedata;
1251         struct scsi_cmnd *cmd;
1252         int specials_only = 0;
1253
1254         /*
1255          * Just check to see if the device is online.  If it isn't, we
1256          * refuse to process any commands.  The device must be brought
1257          * online before trying any recovery commands
1258          */
1259         if (unlikely(!scsi_device_online(sdev))) {
1260                 sdev_printk(KERN_ERR, sdev,
1261                             "rejecting I/O to offline device\n");
1262                 goto kill;
1263         }
1264         if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
1265                 /* OK, we're not in a running state don't prep
1266                  * user commands */
1267                 if (sdev->sdev_state == SDEV_DEL) {
1268                         /* Device is fully deleted, no commands
1269                          * at all allowed down */
1270                         sdev_printk(KERN_ERR, sdev,
1271                                     "rejecting I/O to dead device\n");
1272                         goto kill;
1273                 }
1274                 /* OK, we only allow special commands (i.e. not
1275                  * user initiated ones */
1276                 specials_only = sdev->sdev_state;
1277         }
1278
1279         /*
1280          * Find the actual device driver associated with this command.
1281          * The SPECIAL requests are things like character device or
1282          * ioctls, which did not originate from ll_rw_blk.  Note that
1283          * the special field is also used to indicate the cmd for
1284          * the remainder of a partially fulfilled request that can 
1285          * come up when there is a medium error.  We have to treat
1286          * these two cases differently.  We differentiate by looking
1287          * at request->cmd, as this tells us the real story.
1288          */
1289         if (req->flags & REQ_SPECIAL && req->special) {
1290                 struct scsi_request *sreq = req->special;
1291
1292                 if (sreq->sr_magic == SCSI_REQ_MAGIC) {
1293                         cmd = scsi_get_command(sreq->sr_device, GFP_ATOMIC);
1294                         if (unlikely(!cmd))
1295                                 goto defer;
1296                         scsi_init_cmd_from_req(cmd, sreq);
1297                 } else
1298                         cmd = req->special;
1299         } else if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1300
1301                 if(unlikely(specials_only) && !(req->flags & REQ_SPECIAL)) {
1302                         if(specials_only == SDEV_QUIESCE ||
1303                                         specials_only == SDEV_BLOCK)
1304                                 goto defer;
1305                         
1306                         sdev_printk(KERN_ERR, sdev,
1307                                     "rejecting I/O to device being removed\n");
1308                         goto kill;
1309                 }
1310                         
1311                         
1312                 /*
1313                  * Now try and find a command block that we can use.
1314                  */
1315                 if (!req->special) {
1316                         cmd = scsi_get_command(sdev, GFP_ATOMIC);
1317                         if (unlikely(!cmd))
1318                                 goto defer;
1319                 } else
1320                         cmd = req->special;
1321                 
1322                 /* pull a tag out of the request if we have one */
1323                 cmd->tag = req->tag;
1324         } else {
1325                 blk_dump_rq_flags(req, "SCSI bad req");
1326                 goto kill;
1327         }
1328         
1329         /* note the overloading of req->special.  When the tag
1330          * is active it always means cmd.  If the tag goes
1331          * back for re-queueing, it may be reset */
1332         req->special = cmd;
1333         cmd->request = req;
1334         
1335         /*
1336          * FIXME: drop the lock here because the functions below
1337          * expect to be called without the queue lock held.  Also,
1338          * previously, we dequeued the request before dropping the
1339          * lock.  We hope REQ_STARTED prevents anything untoward from
1340          * happening now.
1341          */
1342         if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1343                 int ret;
1344
1345                 /*
1346                  * This will do a couple of things:
1347                  *  1) Fill in the actual SCSI command.
1348                  *  2) Fill in any other upper-level specific fields
1349                  * (timeout).
1350                  *
1351                  * If this returns 0, it means that the request failed
1352                  * (reading past end of disk, reading offline device,
1353                  * etc).   This won't actually talk to the device, but
1354                  * some kinds of consistency checking may cause the     
1355                  * request to be rejected immediately.
1356                  */
1357
1358                 /* 
1359                  * This sets up the scatter-gather table (allocating if
1360                  * required).
1361                  */
1362                 ret = scsi_init_io(cmd);
1363                 switch(ret) {
1364                         /* For BLKPREP_KILL/DEFER the cmd was released */
1365                 case BLKPREP_KILL:
1366                         goto kill;
1367                 case BLKPREP_DEFER:
1368                         goto defer;
1369                 }
1370                 
1371                 /*
1372                  * Initialize the actual SCSI command for this request.
1373                  */
1374                 if (req->flags & REQ_BLOCK_PC) {
1375                         scsi_setup_blk_pc_cmnd(cmd);
1376                 } else if (req->rq_disk) {
1377                         struct scsi_driver *drv;
1378
1379                         drv = *(struct scsi_driver **)req->rq_disk->private_data;
1380                         if (unlikely(!drv->init_command(cmd))) {
1381                                 scsi_release_buffers(cmd);
1382                                 scsi_put_command(cmd);
1383                                 goto kill;
1384                         }
1385                 }
1386         }
1387
1388         /*
1389          * The request is now prepped, no need to come back here
1390          */
1391         req->flags |= REQ_DONTPREP;
1392         return BLKPREP_OK;
1393
1394  defer:
1395         /* If we defer, the elv_next_request() returns NULL, but the
1396          * queue must be restarted, so we plug here if no returning
1397          * command will automatically do that. */
1398         if (sdev->device_busy == 0)
1399                 blk_plug_device(q);
1400         return BLKPREP_DEFER;
1401  kill:
1402         req->errors = DID_NO_CONNECT << 16;
1403         return BLKPREP_KILL;
1404 }
1405
1406 /*
1407  * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1408  * return 0.
1409  *
1410  * Called with the queue_lock held.
1411  */
1412 static inline int scsi_dev_queue_ready(struct request_queue *q,
1413                                   struct scsi_device *sdev)
1414 {
1415         if (sdev->device_busy >= sdev->queue_depth)
1416                 return 0;
1417         if (sdev->device_busy == 0 && sdev->device_blocked) {
1418                 /*
1419                  * unblock after device_blocked iterates to zero
1420                  */
1421                 if (--sdev->device_blocked == 0) {
1422                         SCSI_LOG_MLQUEUE(3,
1423                                    sdev_printk(KERN_INFO, sdev,
1424                                    "unblocking device at zero depth\n"));
1425                 } else {
1426                         blk_plug_device(q);
1427                         return 0;
1428                 }
1429         }
1430         if (sdev->device_blocked)
1431                 return 0;
1432
1433         return 1;
1434 }
1435
1436 /*
1437  * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1438  * return 0. We must end up running the queue again whenever 0 is
1439  * returned, else IO can hang.
1440  *
1441  * Called with host_lock held.
1442  */
1443 static inline int scsi_host_queue_ready(struct request_queue *q,
1444                                    struct Scsi_Host *shost,
1445                                    struct scsi_device *sdev)
1446 {
1447         if (scsi_host_in_recovery(shost))
1448                 return 0;
1449         if (shost->host_busy == 0 && shost->host_blocked) {
1450                 /*
1451                  * unblock after host_blocked iterates to zero
1452                  */
1453                 if (--shost->host_blocked == 0) {
1454                         SCSI_LOG_MLQUEUE(3,
1455                                 printk("scsi%d unblocking host at zero depth\n",
1456                                         shost->host_no));
1457                 } else {
1458                         blk_plug_device(q);
1459                         return 0;
1460                 }
1461         }
1462         if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
1463             shost->host_blocked || shost->host_self_blocked) {
1464                 if (list_empty(&sdev->starved_entry))
1465                         list_add_tail(&sdev->starved_entry, &shost->starved_list);
1466                 return 0;
1467         }
1468
1469         /* We're OK to process the command, so we can't be starved */
1470         if (!list_empty(&sdev->starved_entry))
1471                 list_del_init(&sdev->starved_entry);
1472
1473         return 1;
1474 }
1475
1476 /*
1477  * Kill a request for a dead device
1478  */
1479 static void scsi_kill_request(struct request *req, request_queue_t *q)
1480 {
1481         struct scsi_cmnd *cmd = req->special;
1482         struct scsi_device *sdev = cmd->device;
1483         struct Scsi_Host *shost = sdev->host;
1484
1485         blkdev_dequeue_request(req);
1486
1487         if (unlikely(cmd == NULL)) {
1488                 printk(KERN_CRIT "impossible request in %s.\n",
1489                                  __FUNCTION__);
1490                 BUG();
1491         }
1492
1493         scsi_init_cmd_errh(cmd);
1494         cmd->result = DID_NO_CONNECT << 16;
1495         atomic_inc(&cmd->device->iorequest_cnt);
1496
1497         /*
1498          * SCSI request completion path will do scsi_device_unbusy(),
1499          * bump busy counts.  To bump the counters, we need to dance
1500          * with the locks as normal issue path does.
1501          */
1502         sdev->device_busy++;
1503         spin_unlock(sdev->request_queue->queue_lock);
1504         spin_lock(shost->host_lock);
1505         shost->host_busy++;
1506         spin_unlock(shost->host_lock);
1507         spin_lock(sdev->request_queue->queue_lock);
1508
1509         __scsi_done(cmd);
1510 }
1511
1512 static void scsi_softirq_done(struct request *rq)
1513 {
1514         struct scsi_cmnd *cmd = rq->completion_data;
1515         unsigned long wait_for = (cmd->allowed + 1) * cmd->timeout_per_command;
1516         int disposition;
1517
1518         INIT_LIST_HEAD(&cmd->eh_entry);
1519
1520         disposition = scsi_decide_disposition(cmd);
1521         if (disposition != SUCCESS &&
1522             time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
1523                 sdev_printk(KERN_ERR, cmd->device,
1524                             "timing out command, waited %lus\n",
1525                             wait_for/HZ);
1526                 disposition = SUCCESS;
1527         }
1528                         
1529         scsi_log_completion(cmd, disposition);
1530
1531         switch (disposition) {
1532                 case SUCCESS:
1533                         scsi_finish_command(cmd);
1534                         break;
1535                 case NEEDS_RETRY:
1536                         scsi_retry_command(cmd);
1537                         break;
1538                 case ADD_TO_MLQUEUE:
1539                         scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
1540                         break;
1541                 default:
1542                         if (!scsi_eh_scmd_add(cmd, 0))
1543                                 scsi_finish_command(cmd);
1544         }
1545 }
1546
1547 /*
1548  * Function:    scsi_request_fn()
1549  *
1550  * Purpose:     Main strategy routine for SCSI.
1551  *
1552  * Arguments:   q       - Pointer to actual queue.
1553  *
1554  * Returns:     Nothing
1555  *
1556  * Lock status: IO request lock assumed to be held when called.
1557  */
1558 static void scsi_request_fn(struct request_queue *q)
1559 {
1560         struct scsi_device *sdev = q->queuedata;
1561         struct Scsi_Host *shost;
1562         struct scsi_cmnd *cmd;
1563         struct request *req;
1564
1565         if (!sdev) {
1566                 printk("scsi: killing requests for dead queue\n");
1567                 while ((req = elv_next_request(q)) != NULL)
1568                         scsi_kill_request(req, q);
1569                 return;
1570         }
1571
1572         if(!get_device(&sdev->sdev_gendev))
1573                 /* We must be tearing the block queue down already */
1574                 return;
1575
1576         /*
1577          * To start with, we keep looping until the queue is empty, or until
1578          * the host is no longer able to accept any more requests.
1579          */
1580         shost = sdev->host;
1581         while (!blk_queue_plugged(q)) {
1582                 int rtn;
1583                 /*
1584                  * get next queueable request.  We do this early to make sure
1585                  * that the request is fully prepared even if we cannot 
1586                  * accept it.
1587                  */
1588                 req = elv_next_request(q);
1589                 if (!req || !scsi_dev_queue_ready(q, sdev))
1590                         break;
1591
1592                 if (unlikely(!scsi_device_online(sdev))) {
1593                         sdev_printk(KERN_ERR, sdev,
1594                                     "rejecting I/O to offline device\n");
1595                         scsi_kill_request(req, q);
1596                         continue;
1597                 }
1598
1599
1600                 /*
1601                  * Remove the request from the request list.
1602                  */
1603                 if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1604                         blkdev_dequeue_request(req);
1605                 sdev->device_busy++;
1606
1607                 spin_unlock(q->queue_lock);
1608                 cmd = req->special;
1609                 if (unlikely(cmd == NULL)) {
1610                         printk(KERN_CRIT "impossible request in %s.\n"
1611                                          "please mail a stack trace to "
1612                                          "linux-scsi@vger.kernel.org",
1613                                          __FUNCTION__);
1614                         BUG();
1615                 }
1616                 spin_lock(shost->host_lock);
1617
1618                 if (!scsi_host_queue_ready(q, shost, sdev))
1619                         goto not_ready;
1620                 if (sdev->single_lun) {
1621                         if (scsi_target(sdev)->starget_sdev_user &&
1622                             scsi_target(sdev)->starget_sdev_user != sdev)
1623                                 goto not_ready;
1624                         scsi_target(sdev)->starget_sdev_user = sdev;
1625                 }
1626                 shost->host_busy++;
1627
1628                 /*
1629                  * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1630                  *              take the lock again.
1631                  */
1632                 spin_unlock_irq(shost->host_lock);
1633
1634                 /*
1635                  * Finally, initialize any error handling parameters, and set up
1636                  * the timers for timeouts.
1637                  */
1638                 scsi_init_cmd_errh(cmd);
1639
1640                 /*
1641                  * Dispatch the command to the low-level driver.
1642                  */
1643                 rtn = scsi_dispatch_cmd(cmd);
1644                 spin_lock_irq(q->queue_lock);
1645                 if(rtn) {
1646                         /* we're refusing the command; because of
1647                          * the way locks get dropped, we need to 
1648                          * check here if plugging is required */
1649                         if(sdev->device_busy == 0)
1650                                 blk_plug_device(q);
1651
1652                         break;
1653                 }
1654         }
1655
1656         goto out;
1657
1658  not_ready:
1659         spin_unlock_irq(shost->host_lock);
1660
1661         /*
1662          * lock q, handle tag, requeue req, and decrement device_busy. We
1663          * must return with queue_lock held.
1664          *
1665          * Decrementing device_busy without checking it is OK, as all such
1666          * cases (host limits or settings) should run the queue at some
1667          * later time.
1668          */
1669         spin_lock_irq(q->queue_lock);
1670         blk_requeue_request(q, req);
1671         sdev->device_busy--;
1672         if(sdev->device_busy == 0)
1673                 blk_plug_device(q);
1674  out:
1675         /* must be careful here...if we trigger the ->remove() function
1676          * we cannot be holding the q lock */
1677         spin_unlock_irq(q->queue_lock);
1678         put_device(&sdev->sdev_gendev);
1679         spin_lock_irq(q->queue_lock);
1680 }
1681
1682 u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1683 {
1684         struct device *host_dev;
1685         u64 bounce_limit = 0xffffffff;
1686
1687         if (shost->unchecked_isa_dma)
1688                 return BLK_BOUNCE_ISA;
1689         /*
1690          * Platforms with virtual-DMA translation
1691          * hardware have no practical limit.
1692          */
1693         if (!PCI_DMA_BUS_IS_PHYS)
1694                 return BLK_BOUNCE_ANY;
1695
1696         host_dev = scsi_get_device(shost);
1697         if (host_dev && host_dev->dma_mask)
1698                 bounce_limit = *host_dev->dma_mask;
1699
1700         return bounce_limit;
1701 }
1702 EXPORT_SYMBOL(scsi_calculate_bounce_limit);
1703
1704 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1705 {
1706         struct Scsi_Host *shost = sdev->host;
1707         struct request_queue *q;
1708
1709         q = blk_init_queue(scsi_request_fn, NULL);
1710         if (!q)
1711                 return NULL;
1712
1713         blk_queue_prep_rq(q, scsi_prep_fn);
1714
1715         blk_queue_max_hw_segments(q, shost->sg_tablesize);
1716         blk_queue_max_phys_segments(q, SCSI_MAX_PHYS_SEGMENTS);
1717         blk_queue_max_sectors(q, shost->max_sectors);
1718         blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1719         blk_queue_segment_boundary(q, shost->dma_boundary);
1720         blk_queue_issue_flush_fn(q, scsi_issue_flush_fn);
1721         blk_queue_softirq_done(q, scsi_softirq_done);
1722
1723         if (!shost->use_clustering)
1724                 clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
1725         return q;
1726 }
1727
1728 void scsi_free_queue(struct request_queue *q)
1729 {
1730         blk_cleanup_queue(q);
1731 }
1732
1733 /*
1734  * Function:    scsi_block_requests()
1735  *
1736  * Purpose:     Utility function used by low-level drivers to prevent further
1737  *              commands from being queued to the device.
1738  *
1739  * Arguments:   shost       - Host in question
1740  *
1741  * Returns:     Nothing
1742  *
1743  * Lock status: No locks are assumed held.
1744  *
1745  * Notes:       There is no timer nor any other means by which the requests
1746  *              get unblocked other than the low-level driver calling
1747  *              scsi_unblock_requests().
1748  */
1749 void scsi_block_requests(struct Scsi_Host *shost)
1750 {
1751         shost->host_self_blocked = 1;
1752 }
1753 EXPORT_SYMBOL(scsi_block_requests);
1754
1755 /*
1756  * Function:    scsi_unblock_requests()
1757  *
1758  * Purpose:     Utility function used by low-level drivers to allow further
1759  *              commands from being queued to the device.
1760  *
1761  * Arguments:   shost       - Host in question
1762  *
1763  * Returns:     Nothing
1764  *
1765  * Lock status: No locks are assumed held.
1766  *
1767  * Notes:       There is no timer nor any other means by which the requests
1768  *              get unblocked other than the low-level driver calling
1769  *              scsi_unblock_requests().
1770  *
1771  *              This is done as an API function so that changes to the
1772  *              internals of the scsi mid-layer won't require wholesale
1773  *              changes to drivers that use this feature.
1774  */
1775 void scsi_unblock_requests(struct Scsi_Host *shost)
1776 {
1777         shost->host_self_blocked = 0;
1778         scsi_run_host_queues(shost);
1779 }
1780 EXPORT_SYMBOL(scsi_unblock_requests);
1781
1782 int __init scsi_init_queue(void)
1783 {
1784         int i;
1785
1786         scsi_io_context_cache = kmem_cache_create("scsi_io_context",
1787                                         sizeof(struct scsi_io_context),
1788                                         0, 0, NULL, NULL);
1789         if (!scsi_io_context_cache) {
1790                 printk(KERN_ERR "SCSI: can't init scsi io context cache\n");
1791                 return -ENOMEM;
1792         }
1793
1794         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1795                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1796                 int size = sgp->size * sizeof(struct scatterlist);
1797
1798                 sgp->slab = kmem_cache_create(sgp->name, size, 0,
1799                                 SLAB_HWCACHE_ALIGN, NULL, NULL);
1800                 if (!sgp->slab) {
1801                         printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1802                                         sgp->name);
1803                 }
1804
1805                 sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
1806                                                      sgp->slab);
1807                 if (!sgp->pool) {
1808                         printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1809                                         sgp->name);
1810                 }
1811         }
1812
1813         return 0;
1814 }
1815
1816 void scsi_exit_queue(void)
1817 {
1818         int i;
1819
1820         kmem_cache_destroy(scsi_io_context_cache);
1821
1822         for (i = 0; i < SG_MEMPOOL_NR; i++) {
1823                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1824                 mempool_destroy(sgp->pool);
1825                 kmem_cache_destroy(sgp->slab);
1826         }
1827 }
1828
1829 /**
1830  *      scsi_mode_select - issue a mode select
1831  *      @sdev:  SCSI device to be queried
1832  *      @pf:    Page format bit (1 == standard, 0 == vendor specific)
1833  *      @sp:    Save page bit (0 == don't save, 1 == save)
1834  *      @modepage: mode page being requested
1835  *      @buffer: request buffer (may not be smaller than eight bytes)
1836  *      @len:   length of request buffer.
1837  *      @timeout: command timeout
1838  *      @retries: number of retries before failing
1839  *      @data: returns a structure abstracting the mode header data
1840  *      @sense: place to put sense data (or NULL if no sense to be collected).
1841  *              must be SCSI_SENSE_BUFFERSIZE big.
1842  *
1843  *      Returns zero if successful; negative error number or scsi
1844  *      status on error
1845  *
1846  */
1847 int
1848 scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
1849                  unsigned char *buffer, int len, int timeout, int retries,
1850                  struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1851 {
1852         unsigned char cmd[10];
1853         unsigned char *real_buffer;
1854         int ret;
1855
1856         memset(cmd, 0, sizeof(cmd));
1857         cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
1858
1859         if (sdev->use_10_for_ms) {
1860                 if (len > 65535)
1861                         return -EINVAL;
1862                 real_buffer = kmalloc(8 + len, GFP_KERNEL);
1863                 if (!real_buffer)
1864                         return -ENOMEM;
1865                 memcpy(real_buffer + 8, buffer, len);
1866                 len += 8;
1867                 real_buffer[0] = 0;
1868                 real_buffer[1] = 0;
1869                 real_buffer[2] = data->medium_type;
1870                 real_buffer[3] = data->device_specific;
1871                 real_buffer[4] = data->longlba ? 0x01 : 0;
1872                 real_buffer[5] = 0;
1873                 real_buffer[6] = data->block_descriptor_length >> 8;
1874                 real_buffer[7] = data->block_descriptor_length;
1875
1876                 cmd[0] = MODE_SELECT_10;
1877                 cmd[7] = len >> 8;
1878                 cmd[8] = len;
1879         } else {
1880                 if (len > 255 || data->block_descriptor_length > 255 ||
1881                     data->longlba)
1882                         return -EINVAL;
1883
1884                 real_buffer = kmalloc(4 + len, GFP_KERNEL);
1885                 if (!real_buffer)
1886                         return -ENOMEM;
1887                 memcpy(real_buffer + 4, buffer, len);
1888                 len += 4;
1889                 real_buffer[0] = 0;
1890                 real_buffer[1] = data->medium_type;
1891                 real_buffer[2] = data->device_specific;
1892                 real_buffer[3] = data->block_descriptor_length;
1893                 
1894
1895                 cmd[0] = MODE_SELECT;
1896                 cmd[4] = len;
1897         }
1898
1899         ret = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, real_buffer, len,
1900                                sshdr, timeout, retries);
1901         kfree(real_buffer);
1902         return ret;
1903 }
1904 EXPORT_SYMBOL_GPL(scsi_mode_select);
1905
1906 /**
1907  *      scsi_mode_sense - issue a mode sense, falling back from 10 to 
1908  *              six bytes if necessary.
1909  *      @sdev:  SCSI device to be queried
1910  *      @dbd:   set if mode sense will allow block descriptors to be returned
1911  *      @modepage: mode page being requested
1912  *      @buffer: request buffer (may not be smaller than eight bytes)
1913  *      @len:   length of request buffer.
1914  *      @timeout: command timeout
1915  *      @retries: number of retries before failing
1916  *      @data: returns a structure abstracting the mode header data
1917  *      @sense: place to put sense data (or NULL if no sense to be collected).
1918  *              must be SCSI_SENSE_BUFFERSIZE big.
1919  *
1920  *      Returns zero if unsuccessful, or the header offset (either 4
1921  *      or 8 depending on whether a six or ten byte command was
1922  *      issued) if successful.
1923  **/
1924 int
1925 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
1926                   unsigned char *buffer, int len, int timeout, int retries,
1927                   struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1928 {
1929         unsigned char cmd[12];
1930         int use_10_for_ms;
1931         int header_length;
1932         int result;
1933         struct scsi_sense_hdr my_sshdr;
1934
1935         memset(data, 0, sizeof(*data));
1936         memset(&cmd[0], 0, 12);
1937         cmd[1] = dbd & 0x18;    /* allows DBD and LLBA bits */
1938         cmd[2] = modepage;
1939
1940         /* caller might not be interested in sense, but we need it */
1941         if (!sshdr)
1942                 sshdr = &my_sshdr;
1943
1944  retry:
1945         use_10_for_ms = sdev->use_10_for_ms;
1946
1947         if (use_10_for_ms) {
1948                 if (len < 8)
1949                         len = 8;
1950
1951                 cmd[0] = MODE_SENSE_10;
1952                 cmd[8] = len;
1953                 header_length = 8;
1954         } else {
1955                 if (len < 4)
1956                         len = 4;
1957
1958                 cmd[0] = MODE_SENSE;
1959                 cmd[4] = len;
1960                 header_length = 4;
1961         }
1962
1963         memset(buffer, 0, len);
1964
1965         result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
1966                                   sshdr, timeout, retries);
1967
1968         /* This code looks awful: what it's doing is making sure an
1969          * ILLEGAL REQUEST sense return identifies the actual command
1970          * byte as the problem.  MODE_SENSE commands can return
1971          * ILLEGAL REQUEST if the code page isn't supported */
1972
1973         if (use_10_for_ms && !scsi_status_is_good(result) &&
1974             (driver_byte(result) & DRIVER_SENSE)) {
1975                 if (scsi_sense_valid(sshdr)) {
1976                         if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
1977                             (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
1978                                 /* 
1979                                  * Invalid command operation code
1980                                  */
1981                                 sdev->use_10_for_ms = 0;
1982                                 goto retry;
1983                         }
1984                 }
1985         }
1986
1987         if(scsi_status_is_good(result)) {
1988                 if (unlikely(buffer[0] == 0x86 && buffer[1] == 0x0b &&
1989                              (modepage == 6 || modepage == 8))) {
1990                         /* Initio breakage? */
1991                         header_length = 0;
1992                         data->length = 13;
1993                         data->medium_type = 0;
1994                         data->device_specific = 0;
1995                         data->longlba = 0;
1996                         data->block_descriptor_length = 0;
1997                 } else if(use_10_for_ms) {
1998                         data->length = buffer[0]*256 + buffer[1] + 2;
1999                         data->medium_type = buffer[2];
2000                         data->device_specific = buffer[3];
2001                         data->longlba = buffer[4] & 0x01;
2002                         data->block_descriptor_length = buffer[6]*256
2003                                 + buffer[7];
2004                 } else {
2005                         data->length = buffer[0] + 1;
2006                         data->medium_type = buffer[1];
2007                         data->device_specific = buffer[2];
2008                         data->block_descriptor_length = buffer[3];
2009                 }
2010                 data->header_length = header_length;
2011         }
2012
2013         return result;
2014 }
2015 EXPORT_SYMBOL(scsi_mode_sense);
2016
2017 int
2018 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries)
2019 {
2020         char cmd[] = {
2021                 TEST_UNIT_READY, 0, 0, 0, 0, 0,
2022         };
2023         struct scsi_sense_hdr sshdr;
2024         int result;
2025         
2026         result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, &sshdr,
2027                                   timeout, retries);
2028
2029         if ((driver_byte(result) & DRIVER_SENSE) && sdev->removable) {
2030
2031                 if ((scsi_sense_valid(&sshdr)) &&
2032                     ((sshdr.sense_key == UNIT_ATTENTION) ||
2033                      (sshdr.sense_key == NOT_READY))) {
2034                         sdev->changed = 1;
2035                         result = 0;
2036                 }
2037         }
2038         return result;
2039 }
2040 EXPORT_SYMBOL(scsi_test_unit_ready);
2041
2042 /**
2043  *      scsi_device_set_state - Take the given device through the device
2044  *              state model.
2045  *      @sdev:  scsi device to change the state of.
2046  *      @state: state to change to.
2047  *
2048  *      Returns zero if unsuccessful or an error if the requested 
2049  *      transition is illegal.
2050  **/
2051 int
2052 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
2053 {
2054         enum scsi_device_state oldstate = sdev->sdev_state;
2055
2056         if (state == oldstate)
2057                 return 0;
2058
2059         switch (state) {
2060         case SDEV_CREATED:
2061                 /* There are no legal states that come back to
2062                  * created.  This is the manually initialised start
2063                  * state */
2064                 goto illegal;
2065                         
2066         case SDEV_RUNNING:
2067                 switch (oldstate) {
2068                 case SDEV_CREATED:
2069                 case SDEV_OFFLINE:
2070                 case SDEV_QUIESCE:
2071                 case SDEV_BLOCK:
2072                         break;
2073                 default:
2074                         goto illegal;
2075                 }
2076                 break;
2077
2078         case SDEV_QUIESCE:
2079                 switch (oldstate) {
2080                 case SDEV_RUNNING:
2081                 case SDEV_OFFLINE:
2082                         break;
2083                 default:
2084                         goto illegal;
2085                 }
2086                 break;
2087
2088         case SDEV_OFFLINE:
2089                 switch (oldstate) {
2090                 case SDEV_CREATED:
2091                 case SDEV_RUNNING:
2092                 case SDEV_QUIESCE:
2093                 case SDEV_BLOCK:
2094                         break;
2095                 default:
2096                         goto illegal;
2097                 }
2098                 break;
2099
2100         case SDEV_BLOCK:
2101                 switch (oldstate) {
2102                 case SDEV_CREATED:
2103                 case SDEV_RUNNING:
2104                         break;
2105                 default:
2106                         goto illegal;
2107                 }
2108                 break;
2109
2110         case SDEV_CANCEL:
2111                 switch (oldstate) {
2112                 case SDEV_CREATED:
2113                 case SDEV_RUNNING:
2114                 case SDEV_OFFLINE:
2115                 case SDEV_BLOCK:
2116                         break;
2117                 default:
2118                         goto illegal;
2119                 }
2120                 break;
2121
2122         case SDEV_DEL:
2123                 switch (oldstate) {
2124                 case SDEV_CANCEL:
2125                         break;
2126                 default:
2127                         goto illegal;
2128                 }
2129                 break;
2130
2131         }
2132         sdev->sdev_state = state;
2133         return 0;
2134
2135  illegal:
2136         SCSI_LOG_ERROR_RECOVERY(1, 
2137                                 sdev_printk(KERN_ERR, sdev,
2138                                             "Illegal state transition %s->%s\n",
2139                                             scsi_device_state_name(oldstate),
2140                                             scsi_device_state_name(state))
2141                                 );
2142         return -EINVAL;
2143 }
2144 EXPORT_SYMBOL(scsi_device_set_state);
2145
2146 /**
2147  *      scsi_device_quiesce - Block user issued commands.
2148  *      @sdev:  scsi device to quiesce.
2149  *
2150  *      This works by trying to transition to the SDEV_QUIESCE state
2151  *      (which must be a legal transition).  When the device is in this
2152  *      state, only special requests will be accepted, all others will
2153  *      be deferred.  Since special requests may also be requeued requests,
2154  *      a successful return doesn't guarantee the device will be 
2155  *      totally quiescent.
2156  *
2157  *      Must be called with user context, may sleep.
2158  *
2159  *      Returns zero if unsuccessful or an error if not.
2160  **/
2161 int
2162 scsi_device_quiesce(struct scsi_device *sdev)
2163 {
2164         int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
2165         if (err)
2166                 return err;
2167
2168         scsi_run_queue(sdev->request_queue);
2169         while (sdev->device_busy) {
2170                 msleep_interruptible(200);
2171                 scsi_run_queue(sdev->request_queue);
2172         }
2173         return 0;
2174 }
2175 EXPORT_SYMBOL(scsi_device_quiesce);
2176
2177 /**
2178  *      scsi_device_resume - Restart user issued commands to a quiesced device.
2179  *      @sdev:  scsi device to resume.
2180  *
2181  *      Moves the device from quiesced back to running and restarts the
2182  *      queues.
2183  *
2184  *      Must be called with user context, may sleep.
2185  **/
2186 void
2187 scsi_device_resume(struct scsi_device *sdev)
2188 {
2189         if(scsi_device_set_state(sdev, SDEV_RUNNING))
2190                 return;
2191         scsi_run_queue(sdev->request_queue);
2192 }
2193 EXPORT_SYMBOL(scsi_device_resume);
2194
2195 static void
2196 device_quiesce_fn(struct scsi_device *sdev, void *data)
2197 {
2198         scsi_device_quiesce(sdev);
2199 }
2200
2201 void
2202 scsi_target_quiesce(struct scsi_target *starget)
2203 {
2204         starget_for_each_device(starget, NULL, device_quiesce_fn);
2205 }
2206 EXPORT_SYMBOL(scsi_target_quiesce);
2207
2208 static void
2209 device_resume_fn(struct scsi_device *sdev, void *data)
2210 {
2211         scsi_device_resume(sdev);
2212 }
2213
2214 void
2215 scsi_target_resume(struct scsi_target *starget)
2216 {
2217         starget_for_each_device(starget, NULL, device_resume_fn);
2218 }
2219 EXPORT_SYMBOL(scsi_target_resume);
2220
2221 /**
2222  * scsi_internal_device_block - internal function to put a device
2223  *                              temporarily into the SDEV_BLOCK state
2224  * @sdev:       device to block
2225  *
2226  * Block request made by scsi lld's to temporarily stop all
2227  * scsi commands on the specified device.  Called from interrupt
2228  * or normal process context.
2229  *
2230  * Returns zero if successful or error if not
2231  *
2232  * Notes:       
2233  *      This routine transitions the device to the SDEV_BLOCK state
2234  *      (which must be a legal transition).  When the device is in this
2235  *      state, all commands are deferred until the scsi lld reenables
2236  *      the device with scsi_device_unblock or device_block_tmo fires.
2237  *      This routine assumes the host_lock is held on entry.
2238  **/
2239 int
2240 scsi_internal_device_block(struct scsi_device *sdev)
2241 {
2242         request_queue_t *q = sdev->request_queue;
2243         unsigned long flags;
2244         int err = 0;
2245
2246         err = scsi_device_set_state(sdev, SDEV_BLOCK);
2247         if (err)
2248                 return err;
2249
2250         /* 
2251          * The device has transitioned to SDEV_BLOCK.  Stop the
2252          * block layer from calling the midlayer with this device's
2253          * request queue. 
2254          */
2255         spin_lock_irqsave(q->queue_lock, flags);
2256         blk_stop_queue(q);
2257         spin_unlock_irqrestore(q->queue_lock, flags);
2258
2259         return 0;
2260 }
2261 EXPORT_SYMBOL_GPL(scsi_internal_device_block);
2262  
2263 /**
2264  * scsi_internal_device_unblock - resume a device after a block request
2265  * @sdev:       device to resume
2266  *
2267  * Called by scsi lld's or the midlayer to restart the device queue
2268  * for the previously suspended scsi device.  Called from interrupt or
2269  * normal process context.
2270  *
2271  * Returns zero if successful or error if not.
2272  *
2273  * Notes:       
2274  *      This routine transitions the device to the SDEV_RUNNING state
2275  *      (which must be a legal transition) allowing the midlayer to
2276  *      goose the queue for this device.  This routine assumes the 
2277  *      host_lock is held upon entry.
2278  **/
2279 int
2280 scsi_internal_device_unblock(struct scsi_device *sdev)
2281 {
2282         request_queue_t *q = sdev->request_queue; 
2283         int err;
2284         unsigned long flags;
2285         
2286         /* 
2287          * Try to transition the scsi device to SDEV_RUNNING
2288          * and goose the device queue if successful.  
2289          */
2290         err = scsi_device_set_state(sdev, SDEV_RUNNING);
2291         if (err)
2292                 return err;
2293
2294         spin_lock_irqsave(q->queue_lock, flags);
2295         blk_start_queue(q);
2296         spin_unlock_irqrestore(q->queue_lock, flags);
2297
2298         return 0;
2299 }
2300 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
2301
2302 static void
2303 device_block(struct scsi_device *sdev, void *data)
2304 {
2305         scsi_internal_device_block(sdev);
2306 }
2307
2308 static int
2309 target_block(struct device *dev, void *data)
2310 {
2311         if (scsi_is_target_device(dev))
2312                 starget_for_each_device(to_scsi_target(dev), NULL,
2313                                         device_block);
2314         return 0;
2315 }
2316
2317 void
2318 scsi_target_block(struct device *dev)
2319 {
2320         if (scsi_is_target_device(dev))
2321                 starget_for_each_device(to_scsi_target(dev), NULL,
2322                                         device_block);
2323         else
2324                 device_for_each_child(dev, NULL, target_block);
2325 }
2326 EXPORT_SYMBOL_GPL(scsi_target_block);
2327
2328 static void
2329 device_unblock(struct scsi_device *sdev, void *data)
2330 {
2331         scsi_internal_device_unblock(sdev);
2332 }
2333
2334 static int
2335 target_unblock(struct device *dev, void *data)
2336 {
2337         if (scsi_is_target_device(dev))
2338                 starget_for_each_device(to_scsi_target(dev), NULL,
2339                                         device_unblock);
2340         return 0;
2341 }
2342
2343 void
2344 scsi_target_unblock(struct device *dev)
2345 {
2346         if (scsi_is_target_device(dev))
2347                 starget_for_each_device(to_scsi_target(dev), NULL,
2348                                         device_unblock);
2349         else
2350                 device_for_each_child(dev, NULL, target_unblock);
2351 }
2352 EXPORT_SYMBOL_GPL(scsi_target_unblock);