x86: get rid of checkpatch.pl complains on apm_32.c
[linux-2.6/mini2440.git] / drivers / scsi / scsi_lib.c
blob7c4c889c5221e09ed9cb00380c5c3053256c8545
1 /*
2 * scsi_lib.c Copyright (C) 1999 Eric Youngdale
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 */
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 #include <linux/scatterlist.h>
22 #include <scsi/scsi.h>
23 #include <scsi/scsi_cmnd.h>
24 #include <scsi/scsi_dbg.h>
25 #include <scsi/scsi_device.h>
26 #include <scsi/scsi_driver.h>
27 #include <scsi/scsi_eh.h>
28 #include <scsi/scsi_host.h>
30 #include "scsi_priv.h"
31 #include "scsi_logging.h"
34 #define SG_MEMPOOL_NR ARRAY_SIZE(scsi_sg_pools)
35 #define SG_MEMPOOL_SIZE 2
38 * The maximum number of SG segments that we will put inside a scatterlist
39 * (unless chaining is used). Should ideally fit inside a single page, to
40 * avoid a higher order allocation.
42 #define SCSI_MAX_SG_SEGMENTS 128
44 struct scsi_host_sg_pool {
45 size_t size;
46 char *name;
47 struct kmem_cache *slab;
48 mempool_t *pool;
51 #define SP(x) { x, "sgpool-" #x }
52 static struct scsi_host_sg_pool scsi_sg_pools[] = {
53 SP(8),
54 SP(16),
55 #if (SCSI_MAX_SG_SEGMENTS > 16)
56 SP(32),
57 #if (SCSI_MAX_SG_SEGMENTS > 32)
58 SP(64),
59 #if (SCSI_MAX_SG_SEGMENTS > 64)
60 SP(128),
61 #endif
62 #endif
63 #endif
65 #undef SP
67 static void scsi_run_queue(struct request_queue *q);
70 * Function: scsi_unprep_request()
72 * Purpose: Remove all preparation done for a request, including its
73 * associated scsi_cmnd, so that it can be requeued.
75 * Arguments: req - request to unprepare
77 * Lock status: Assumed that no locks are held upon entry.
79 * Returns: Nothing.
81 static void scsi_unprep_request(struct request *req)
83 struct scsi_cmnd *cmd = req->special;
85 req->cmd_flags &= ~REQ_DONTPREP;
86 req->special = NULL;
88 scsi_put_command(cmd);
92 * Function: scsi_queue_insert()
94 * Purpose: Insert a command in the midlevel queue.
96 * Arguments: cmd - command that we are adding to queue.
97 * reason - why we are inserting command to queue.
99 * Lock status: Assumed that lock is not held upon entry.
101 * Returns: Nothing.
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.
110 int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
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;
117 SCSI_LOG_MLQUEUE(1,
118 printk("Inserting command %p into mlqueue\n", cmd));
121 * Set the appropriate busy bit for the device/host.
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.
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.
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;
139 * Decrement the counters, since these commands are no longer
140 * active on the host/device.
142 scsi_device_unbusy(device);
145 * Requeue this command. It will go before all other commands
146 * that are already in the queue.
148 * NOTE: there is magic here about the way the queue is plugged if
149 * we have no outstanding commands.
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.
155 spin_lock_irqsave(q->queue_lock, flags);
156 blk_requeue_request(q, cmd->request);
157 spin_unlock_irqrestore(q->queue_lock, flags);
159 scsi_run_queue(q);
161 return 0;
165 * scsi_execute - insert request and wait for the result
166 * @sdev: scsi device
167 * @cmd: scsi command
168 * @data_direction: data direction
169 * @buffer: data buffer
170 * @bufflen: len of buffer
171 * @sense: optional sense buffer
172 * @timeout: request timeout in seconds
173 * @retries: number of times to retry request
174 * @flags: or into request flags;
176 * returns the req->errors value which is the scsi_cmnd result
177 * field.
179 int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
180 int data_direction, void *buffer, unsigned bufflen,
181 unsigned char *sense, int timeout, int retries, int flags)
183 struct request *req;
184 int write = (data_direction == DMA_TO_DEVICE);
185 int ret = DRIVER_ERROR << 24;
187 req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
189 if (bufflen && blk_rq_map_kern(sdev->request_queue, req,
190 buffer, bufflen, __GFP_WAIT))
191 goto out;
193 req->cmd_len = COMMAND_SIZE(cmd[0]);
194 memcpy(req->cmd, cmd, req->cmd_len);
195 req->sense = sense;
196 req->sense_len = 0;
197 req->retries = retries;
198 req->timeout = timeout;
199 req->cmd_type = REQ_TYPE_BLOCK_PC;
200 req->cmd_flags |= flags | REQ_QUIET | REQ_PREEMPT;
203 * head injection *required* here otherwise quiesce won't work
205 blk_execute_rq(req->q, NULL, req, 1);
207 ret = req->errors;
208 out:
209 blk_put_request(req);
211 return ret;
213 EXPORT_SYMBOL(scsi_execute);
216 int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
217 int data_direction, void *buffer, unsigned bufflen,
218 struct scsi_sense_hdr *sshdr, int timeout, int retries)
220 char *sense = NULL;
221 int result;
223 if (sshdr) {
224 sense = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
225 if (!sense)
226 return DRIVER_ERROR << 24;
228 result = scsi_execute(sdev, cmd, data_direction, buffer, bufflen,
229 sense, timeout, retries, 0);
230 if (sshdr)
231 scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, sshdr);
233 kfree(sense);
234 return result;
236 EXPORT_SYMBOL(scsi_execute_req);
238 struct scsi_io_context {
239 void *data;
240 void (*done)(void *data, char *sense, int result, int resid);
241 char sense[SCSI_SENSE_BUFFERSIZE];
244 static struct kmem_cache *scsi_io_context_cache;
246 static void scsi_end_async(struct request *req, int uptodate)
248 struct scsi_io_context *sioc = req->end_io_data;
250 if (sioc->done)
251 sioc->done(sioc->data, sioc->sense, req->errors, req->data_len);
253 kmem_cache_free(scsi_io_context_cache, sioc);
254 __blk_put_request(req->q, req);
257 static int scsi_merge_bio(struct request *rq, struct bio *bio)
259 struct request_queue *q = rq->q;
261 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
262 if (rq_data_dir(rq) == WRITE)
263 bio->bi_rw |= (1 << BIO_RW);
264 blk_queue_bounce(q, &bio);
266 return blk_rq_append_bio(q, rq, bio);
269 static void scsi_bi_endio(struct bio *bio, int error)
271 bio_put(bio);
275 * scsi_req_map_sg - map a scatterlist into a request
276 * @rq: request to fill
277 * @sgl: scatterlist
278 * @nsegs: number of elements
279 * @bufflen: len of buffer
280 * @gfp: memory allocation flags
282 * scsi_req_map_sg maps a scatterlist into a request so that the
283 * request can be sent to the block layer. We do not trust the scatterlist
284 * sent to use, as some ULDs use that struct to only organize the pages.
286 static int scsi_req_map_sg(struct request *rq, struct scatterlist *sgl,
287 int nsegs, unsigned bufflen, gfp_t gfp)
289 struct request_queue *q = rq->q;
290 int nr_pages = (bufflen + sgl[0].offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
291 unsigned int data_len = bufflen, len, bytes, off;
292 struct scatterlist *sg;
293 struct page *page;
294 struct bio *bio = NULL;
295 int i, err, nr_vecs = 0;
297 for_each_sg(sgl, sg, nsegs, i) {
298 page = sg_page(sg);
299 off = sg->offset;
300 len = sg->length;
301 data_len += len;
303 while (len > 0 && data_len > 0) {
305 * sg sends a scatterlist that is larger than
306 * the data_len it wants transferred for certain
307 * IO sizes
309 bytes = min_t(unsigned int, len, PAGE_SIZE - off);
310 bytes = min(bytes, data_len);
312 if (!bio) {
313 nr_vecs = min_t(int, BIO_MAX_PAGES, nr_pages);
314 nr_pages -= nr_vecs;
316 bio = bio_alloc(gfp, nr_vecs);
317 if (!bio) {
318 err = -ENOMEM;
319 goto free_bios;
321 bio->bi_end_io = scsi_bi_endio;
324 if (bio_add_pc_page(q, bio, page, bytes, off) !=
325 bytes) {
326 bio_put(bio);
327 err = -EINVAL;
328 goto free_bios;
331 if (bio->bi_vcnt >= nr_vecs) {
332 err = scsi_merge_bio(rq, bio);
333 if (err) {
334 bio_endio(bio, 0);
335 goto free_bios;
337 bio = NULL;
340 page++;
341 len -= bytes;
342 data_len -=bytes;
343 off = 0;
347 rq->buffer = rq->data = NULL;
348 rq->data_len = bufflen;
349 return 0;
351 free_bios:
352 while ((bio = rq->bio) != NULL) {
353 rq->bio = bio->bi_next;
355 * call endio instead of bio_put incase it was bounced
357 bio_endio(bio, 0);
360 return err;
364 * scsi_execute_async - insert request
365 * @sdev: scsi device
366 * @cmd: scsi command
367 * @cmd_len: length of scsi cdb
368 * @data_direction: DMA_TO_DEVICE, DMA_FROM_DEVICE, or DMA_NONE
369 * @buffer: data buffer (this can be a kernel buffer or scatterlist)
370 * @bufflen: len of buffer
371 * @use_sg: if buffer is a scatterlist this is the number of elements
372 * @timeout: request timeout in seconds
373 * @retries: number of times to retry request
374 * @privdata: data passed to done()
375 * @done: callback function when done
376 * @gfp: memory allocation flags
378 int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
379 int cmd_len, int data_direction, void *buffer, unsigned bufflen,
380 int use_sg, int timeout, int retries, void *privdata,
381 void (*done)(void *, char *, int, int), gfp_t gfp)
383 struct request *req;
384 struct scsi_io_context *sioc;
385 int err = 0;
386 int write = (data_direction == DMA_TO_DEVICE);
388 sioc = kmem_cache_zalloc(scsi_io_context_cache, gfp);
389 if (!sioc)
390 return DRIVER_ERROR << 24;
392 req = blk_get_request(sdev->request_queue, write, gfp);
393 if (!req)
394 goto free_sense;
395 req->cmd_type = REQ_TYPE_BLOCK_PC;
396 req->cmd_flags |= REQ_QUIET;
398 if (use_sg)
399 err = scsi_req_map_sg(req, buffer, use_sg, bufflen, gfp);
400 else if (bufflen)
401 err = blk_rq_map_kern(req->q, req, buffer, bufflen, gfp);
403 if (err)
404 goto free_req;
406 req->cmd_len = cmd_len;
407 memset(req->cmd, 0, BLK_MAX_CDB); /* ATAPI hates garbage after CDB */
408 memcpy(req->cmd, cmd, req->cmd_len);
409 req->sense = sioc->sense;
410 req->sense_len = 0;
411 req->timeout = timeout;
412 req->retries = retries;
413 req->end_io_data = sioc;
415 sioc->data = privdata;
416 sioc->done = done;
418 blk_execute_rq_nowait(req->q, NULL, req, 1, scsi_end_async);
419 return 0;
421 free_req:
422 blk_put_request(req);
423 free_sense:
424 kmem_cache_free(scsi_io_context_cache, sioc);
425 return DRIVER_ERROR << 24;
427 EXPORT_SYMBOL_GPL(scsi_execute_async);
430 * Function: scsi_init_cmd_errh()
432 * Purpose: Initialize cmd fields related to error handling.
434 * Arguments: cmd - command that is ready to be queued.
436 * Notes: This function has the job of initializing a number of
437 * fields related to error handling. Typically this will
438 * be called once for each command, as required.
440 static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
442 cmd->serial_number = 0;
443 cmd->resid = 0;
444 memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
445 if (cmd->cmd_len == 0)
446 cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);
449 void scsi_device_unbusy(struct scsi_device *sdev)
451 struct Scsi_Host *shost = sdev->host;
452 unsigned long flags;
454 spin_lock_irqsave(shost->host_lock, flags);
455 shost->host_busy--;
456 if (unlikely(scsi_host_in_recovery(shost) &&
457 (shost->host_failed || shost->host_eh_scheduled)))
458 scsi_eh_wakeup(shost);
459 spin_unlock(shost->host_lock);
460 spin_lock(sdev->request_queue->queue_lock);
461 sdev->device_busy--;
462 spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
466 * Called for single_lun devices on IO completion. Clear starget_sdev_user,
467 * and call blk_run_queue for all the scsi_devices on the target -
468 * including current_sdev first.
470 * Called with *no* scsi locks held.
472 static void scsi_single_lun_run(struct scsi_device *current_sdev)
474 struct Scsi_Host *shost = current_sdev->host;
475 struct scsi_device *sdev, *tmp;
476 struct scsi_target *starget = scsi_target(current_sdev);
477 unsigned long flags;
479 spin_lock_irqsave(shost->host_lock, flags);
480 starget->starget_sdev_user = NULL;
481 spin_unlock_irqrestore(shost->host_lock, flags);
484 * Call blk_run_queue for all LUNs on the target, starting with
485 * current_sdev. We race with others (to set starget_sdev_user),
486 * but in most cases, we will be first. Ideally, each LU on the
487 * target would get some limited time or requests on the target.
489 blk_run_queue(current_sdev->request_queue);
491 spin_lock_irqsave(shost->host_lock, flags);
492 if (starget->starget_sdev_user)
493 goto out;
494 list_for_each_entry_safe(sdev, tmp, &starget->devices,
495 same_target_siblings) {
496 if (sdev == current_sdev)
497 continue;
498 if (scsi_device_get(sdev))
499 continue;
501 spin_unlock_irqrestore(shost->host_lock, flags);
502 blk_run_queue(sdev->request_queue);
503 spin_lock_irqsave(shost->host_lock, flags);
505 scsi_device_put(sdev);
507 out:
508 spin_unlock_irqrestore(shost->host_lock, flags);
512 * Function: scsi_run_queue()
514 * Purpose: Select a proper request queue to serve next
516 * Arguments: q - last request's queue
518 * Returns: Nothing
520 * Notes: The previous command was completely finished, start
521 * a new one if possible.
523 static void scsi_run_queue(struct request_queue *q)
525 struct scsi_device *sdev = q->queuedata;
526 struct Scsi_Host *shost = sdev->host;
527 unsigned long flags;
529 if (scsi_target(sdev)->single_lun)
530 scsi_single_lun_run(sdev);
532 spin_lock_irqsave(shost->host_lock, flags);
533 while (!list_empty(&shost->starved_list) &&
534 !shost->host_blocked && !shost->host_self_blocked &&
535 !((shost->can_queue > 0) &&
536 (shost->host_busy >= shost->can_queue))) {
538 * As long as shost is accepting commands and we have
539 * starved queues, call blk_run_queue. scsi_request_fn
540 * drops the queue_lock and can add us back to the
541 * starved_list.
543 * host_lock protects the starved_list and starved_entry.
544 * scsi_request_fn must get the host_lock before checking
545 * or modifying starved_list or starved_entry.
547 sdev = list_entry(shost->starved_list.next,
548 struct scsi_device, starved_entry);
549 list_del_init(&sdev->starved_entry);
550 spin_unlock_irqrestore(shost->host_lock, flags);
553 if (test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) &&
554 !test_and_set_bit(QUEUE_FLAG_REENTER,
555 &sdev->request_queue->queue_flags)) {
556 blk_run_queue(sdev->request_queue);
557 clear_bit(QUEUE_FLAG_REENTER,
558 &sdev->request_queue->queue_flags);
559 } else
560 blk_run_queue(sdev->request_queue);
562 spin_lock_irqsave(shost->host_lock, flags);
563 if (unlikely(!list_empty(&sdev->starved_entry)))
565 * sdev lost a race, and was put back on the
566 * starved list. This is unlikely but without this
567 * in theory we could loop forever.
569 break;
571 spin_unlock_irqrestore(shost->host_lock, flags);
573 blk_run_queue(q);
577 * Function: scsi_requeue_command()
579 * Purpose: Handle post-processing of completed commands.
581 * Arguments: q - queue to operate on
582 * cmd - command that may need to be requeued.
584 * Returns: Nothing
586 * Notes: After command completion, there may be blocks left
587 * over which weren't finished by the previous command
588 * this can be for a number of reasons - the main one is
589 * I/O errors in the middle of the request, in which case
590 * we need to request the blocks that come after the bad
591 * sector.
592 * Notes: Upon return, cmd is a stale pointer.
594 static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
596 struct request *req = cmd->request;
597 unsigned long flags;
599 scsi_unprep_request(req);
600 spin_lock_irqsave(q->queue_lock, flags);
601 blk_requeue_request(q, req);
602 spin_unlock_irqrestore(q->queue_lock, flags);
604 scsi_run_queue(q);
607 void scsi_next_command(struct scsi_cmnd *cmd)
609 struct scsi_device *sdev = cmd->device;
610 struct request_queue *q = sdev->request_queue;
612 /* need to hold a reference on the device before we let go of the cmd */
613 get_device(&sdev->sdev_gendev);
615 scsi_put_command(cmd);
616 scsi_run_queue(q);
618 /* ok to remove device now */
619 put_device(&sdev->sdev_gendev);
622 void scsi_run_host_queues(struct Scsi_Host *shost)
624 struct scsi_device *sdev;
626 shost_for_each_device(sdev, shost)
627 scsi_run_queue(sdev->request_queue);
631 * Function: scsi_end_request()
633 * Purpose: Post-processing of completed commands (usually invoked at end
634 * of upper level post-processing and scsi_io_completion).
636 * Arguments: cmd - command that is complete.
637 * error - 0 if I/O indicates success, < 0 for I/O error.
638 * bytes - number of bytes of completed I/O
639 * requeue - indicates whether we should requeue leftovers.
641 * Lock status: Assumed that lock is not held upon entry.
643 * Returns: cmd if requeue required, NULL otherwise.
645 * Notes: This is called for block device requests in order to
646 * mark some number of sectors as complete.
648 * We are guaranteeing that the request queue will be goosed
649 * at some point during this call.
650 * Notes: If cmd was requeued, upon return it will be a stale pointer.
652 static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
653 int bytes, int requeue)
655 struct request_queue *q = cmd->device->request_queue;
656 struct request *req = cmd->request;
659 * If there are blocks left over at the end, set up the command
660 * to queue the remainder of them.
662 if (blk_end_request(req, error, bytes)) {
663 int leftover = (req->hard_nr_sectors << 9);
665 if (blk_pc_request(req))
666 leftover = req->data_len;
668 /* kill remainder if no retrys */
669 if (error && blk_noretry_request(req))
670 blk_end_request(req, error, leftover);
671 else {
672 if (requeue) {
674 * Bleah. Leftovers again. Stick the
675 * leftovers in the front of the
676 * queue, and goose the queue again.
678 scsi_requeue_command(q, cmd);
679 cmd = NULL;
681 return cmd;
686 * This will goose the queue request function at the end, so we don't
687 * need to worry about launching another command.
689 scsi_next_command(cmd);
690 return NULL;
694 * Like SCSI_MAX_SG_SEGMENTS, but for archs that have sg chaining. This limit
695 * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
697 #define SCSI_MAX_SG_CHAIN_SEGMENTS 2048
699 static inline unsigned int scsi_sgtable_index(unsigned short nents)
701 unsigned int index;
703 switch (nents) {
704 case 1 ... 8:
705 index = 0;
706 break;
707 case 9 ... 16:
708 index = 1;
709 break;
710 #if (SCSI_MAX_SG_SEGMENTS > 16)
711 case 17 ... 32:
712 index = 2;
713 break;
714 #if (SCSI_MAX_SG_SEGMENTS > 32)
715 case 33 ... 64:
716 index = 3;
717 break;
718 #if (SCSI_MAX_SG_SEGMENTS > 64)
719 case 65 ... 128:
720 index = 4;
721 break;
722 #endif
723 #endif
724 #endif
725 default:
726 printk(KERN_ERR "scsi: bad segment count=%d\n", nents);
727 BUG();
730 return index;
733 static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)
735 struct scsi_host_sg_pool *sgp;
737 sgp = scsi_sg_pools + scsi_sgtable_index(nents);
738 mempool_free(sgl, sgp->pool);
741 static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
743 struct scsi_host_sg_pool *sgp;
745 sgp = scsi_sg_pools + scsi_sgtable_index(nents);
746 return mempool_alloc(sgp->pool, gfp_mask);
749 int scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
751 int ret;
753 BUG_ON(!cmd->use_sg);
755 ret = __sg_alloc_table(&cmd->sg_table, cmd->use_sg,
756 SCSI_MAX_SG_SEGMENTS, gfp_mask, scsi_sg_alloc);
757 if (unlikely(ret))
758 __sg_free_table(&cmd->sg_table, SCSI_MAX_SG_SEGMENTS,
759 scsi_sg_free);
761 cmd->request_buffer = cmd->sg_table.sgl;
762 return ret;
765 EXPORT_SYMBOL(scsi_alloc_sgtable);
767 void scsi_free_sgtable(struct scsi_cmnd *cmd)
769 __sg_free_table(&cmd->sg_table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
772 EXPORT_SYMBOL(scsi_free_sgtable);
775 * Function: scsi_release_buffers()
777 * Purpose: Completion processing for block device I/O requests.
779 * Arguments: cmd - command that we are bailing.
781 * Lock status: Assumed that no lock is held upon entry.
783 * Returns: Nothing
785 * Notes: In the event that an upper level driver rejects a
786 * command, we must release resources allocated during
787 * the __init_io() function. Primarily this would involve
788 * the scatter-gather table, and potentially any bounce
789 * buffers.
791 static void scsi_release_buffers(struct scsi_cmnd *cmd)
793 if (cmd->use_sg)
794 scsi_free_sgtable(cmd);
797 * Zero these out. They now point to freed memory, and it is
798 * dangerous to hang onto the pointers.
800 cmd->request_buffer = NULL;
801 cmd->request_bufflen = 0;
805 * Function: scsi_io_completion()
807 * Purpose: Completion processing for block device I/O requests.
809 * Arguments: cmd - command that is finished.
811 * Lock status: Assumed that no lock is held upon entry.
813 * Returns: Nothing
815 * Notes: This function is matched in terms of capabilities to
816 * the function that created the scatter-gather list.
817 * In other words, if there are no bounce buffers
818 * (the normal case for most drivers), we don't need
819 * the logic to deal with cleaning up afterwards.
821 * We must do one of several things here:
823 * a) Call scsi_end_request. This will finish off the
824 * specified number of sectors. If we are done, the
825 * command block will be released, and the queue
826 * function will be goosed. If we are not done, then
827 * scsi_end_request will directly goose the queue.
829 * b) We can just use scsi_requeue_command() here. This would
830 * be used if we just wanted to retry, for example.
832 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
834 int result = cmd->result;
835 int this_count = cmd->request_bufflen;
836 struct request_queue *q = cmd->device->request_queue;
837 struct request *req = cmd->request;
838 int clear_errors = 1;
839 struct scsi_sense_hdr sshdr;
840 int sense_valid = 0;
841 int sense_deferred = 0;
843 scsi_release_buffers(cmd);
845 if (result) {
846 sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
847 if (sense_valid)
848 sense_deferred = scsi_sense_is_deferred(&sshdr);
851 if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
852 req->errors = result;
853 if (result) {
854 clear_errors = 0;
855 if (sense_valid && req->sense) {
857 * SG_IO wants current and deferred errors
859 int len = 8 + cmd->sense_buffer[7];
861 if (len > SCSI_SENSE_BUFFERSIZE)
862 len = SCSI_SENSE_BUFFERSIZE;
863 memcpy(req->sense, cmd->sense_buffer, len);
864 req->sense_len = len;
867 req->data_len = cmd->resid;
871 * Next deal with any sectors which we were able to correctly
872 * handle.
874 SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, "
875 "%d bytes done.\n",
876 req->nr_sectors, good_bytes));
877 SCSI_LOG_HLCOMPLETE(1, printk("use_sg is %d\n", cmd->use_sg));
879 if (clear_errors)
880 req->errors = 0;
882 /* A number of bytes were successfully read. If there
883 * are leftovers and there is some kind of error
884 * (result != 0), retry the rest.
886 if (scsi_end_request(cmd, 0, good_bytes, result == 0) == NULL)
887 return;
889 /* good_bytes = 0, or (inclusive) there were leftovers and
890 * result = 0, so scsi_end_request couldn't retry.
892 if (sense_valid && !sense_deferred) {
893 switch (sshdr.sense_key) {
894 case UNIT_ATTENTION:
895 if (cmd->device->removable) {
896 /* Detected disc change. Set a bit
897 * and quietly refuse further access.
899 cmd->device->changed = 1;
900 scsi_end_request(cmd, -EIO, this_count, 1);
901 return;
902 } else {
903 /* Must have been a power glitch, or a
904 * bus reset. Could not have been a
905 * media change, so we just retry the
906 * request and see what happens.
908 scsi_requeue_command(q, cmd);
909 return;
911 break;
912 case ILLEGAL_REQUEST:
913 /* If we had an ILLEGAL REQUEST returned, then
914 * we may have performed an unsupported
915 * command. The only thing this should be
916 * would be a ten byte read where only a six
917 * byte read was supported. Also, on a system
918 * where READ CAPACITY failed, we may have
919 * read past the end of the disk.
921 if ((cmd->device->use_10_for_rw &&
922 sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
923 (cmd->cmnd[0] == READ_10 ||
924 cmd->cmnd[0] == WRITE_10)) {
925 cmd->device->use_10_for_rw = 0;
926 /* This will cause a retry with a
927 * 6-byte command.
929 scsi_requeue_command(q, cmd);
930 return;
931 } else {
932 scsi_end_request(cmd, -EIO, this_count, 1);
933 return;
935 break;
936 case NOT_READY:
937 /* If the device is in the process of becoming
938 * ready, or has a temporary blockage, retry.
940 if (sshdr.asc == 0x04) {
941 switch (sshdr.ascq) {
942 case 0x01: /* becoming ready */
943 case 0x04: /* format in progress */
944 case 0x05: /* rebuild in progress */
945 case 0x06: /* recalculation in progress */
946 case 0x07: /* operation in progress */
947 case 0x08: /* Long write in progress */
948 case 0x09: /* self test in progress */
949 scsi_requeue_command(q, cmd);
950 return;
951 default:
952 break;
955 if (!(req->cmd_flags & REQ_QUIET))
956 scsi_cmd_print_sense_hdr(cmd,
957 "Device not ready",
958 &sshdr);
960 scsi_end_request(cmd, -EIO, this_count, 1);
961 return;
962 case VOLUME_OVERFLOW:
963 if (!(req->cmd_flags & REQ_QUIET)) {
964 scmd_printk(KERN_INFO, cmd,
965 "Volume overflow, CDB: ");
966 __scsi_print_command(cmd->cmnd);
967 scsi_print_sense("", cmd);
969 /* See SSC3rXX or current. */
970 scsi_end_request(cmd, -EIO, this_count, 1);
971 return;
972 default:
973 break;
976 if (host_byte(result) == DID_RESET) {
977 /* Third party bus reset or reset for error recovery
978 * reasons. Just retry the request and see what
979 * happens.
981 scsi_requeue_command(q, cmd);
982 return;
984 if (result) {
985 if (!(req->cmd_flags & REQ_QUIET)) {
986 scsi_print_result(cmd);
987 if (driver_byte(result) & DRIVER_SENSE)
988 scsi_print_sense("", cmd);
991 scsi_end_request(cmd, -EIO, this_count, !result);
995 * Function: scsi_init_io()
997 * Purpose: SCSI I/O initialize function.
999 * Arguments: cmd - Command descriptor we wish to initialize
1001 * Returns: 0 on success
1002 * BLKPREP_DEFER if the failure is retryable
1004 static int scsi_init_io(struct scsi_cmnd *cmd)
1006 struct request *req = cmd->request;
1007 int count;
1010 * We used to not use scatter-gather for single segment request,
1011 * but now we do (it makes highmem I/O easier to support without
1012 * kmapping pages)
1014 cmd->use_sg = req->nr_phys_segments;
1017 * If sg table allocation fails, requeue request later.
1019 if (unlikely(scsi_alloc_sgtable(cmd, GFP_ATOMIC))) {
1020 scsi_unprep_request(req);
1021 return BLKPREP_DEFER;
1024 req->buffer = NULL;
1025 if (blk_pc_request(req))
1026 cmd->request_bufflen = req->data_len;
1027 else
1028 cmd->request_bufflen = req->nr_sectors << 9;
1031 * Next, walk the list, and fill in the addresses and sizes of
1032 * each segment.
1034 count = blk_rq_map_sg(req->q, req, cmd->request_buffer);
1035 BUG_ON(count > cmd->use_sg);
1036 cmd->use_sg = count;
1037 return BLKPREP_OK;
1040 static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
1041 struct request *req)
1043 struct scsi_cmnd *cmd;
1045 if (!req->special) {
1046 cmd = scsi_get_command(sdev, GFP_ATOMIC);
1047 if (unlikely(!cmd))
1048 return NULL;
1049 req->special = cmd;
1050 } else {
1051 cmd = req->special;
1054 /* pull a tag out of the request if we have one */
1055 cmd->tag = req->tag;
1056 cmd->request = req;
1058 return cmd;
1061 int scsi_setup_blk_pc_cmnd(struct scsi_device *sdev, struct request *req)
1063 struct scsi_cmnd *cmd;
1064 int ret = scsi_prep_state_check(sdev, req);
1066 if (ret != BLKPREP_OK)
1067 return ret;
1069 cmd = scsi_get_cmd_from_req(sdev, req);
1070 if (unlikely(!cmd))
1071 return BLKPREP_DEFER;
1074 * BLOCK_PC requests may transfer data, in which case they must
1075 * a bio attached to them. Or they might contain a SCSI command
1076 * that does not transfer data, in which case they may optionally
1077 * submit a request without an attached bio.
1079 if (req->bio) {
1080 int ret;
1082 BUG_ON(!req->nr_phys_segments);
1084 ret = scsi_init_io(cmd);
1085 if (unlikely(ret))
1086 return ret;
1087 } else {
1088 BUG_ON(req->data_len);
1089 BUG_ON(req->data);
1091 cmd->request_bufflen = 0;
1092 cmd->request_buffer = NULL;
1093 cmd->use_sg = 0;
1094 req->buffer = NULL;
1097 BUILD_BUG_ON(sizeof(req->cmd) > sizeof(cmd->cmnd));
1098 memcpy(cmd->cmnd, req->cmd, sizeof(cmd->cmnd));
1099 cmd->cmd_len = req->cmd_len;
1100 if (!req->data_len)
1101 cmd->sc_data_direction = DMA_NONE;
1102 else if (rq_data_dir(req) == WRITE)
1103 cmd->sc_data_direction = DMA_TO_DEVICE;
1104 else
1105 cmd->sc_data_direction = DMA_FROM_DEVICE;
1107 cmd->transfersize = req->data_len;
1108 cmd->allowed = req->retries;
1109 cmd->timeout_per_command = req->timeout;
1110 return BLKPREP_OK;
1112 EXPORT_SYMBOL(scsi_setup_blk_pc_cmnd);
1115 * Setup a REQ_TYPE_FS command. These are simple read/write request
1116 * from filesystems that still need to be translated to SCSI CDBs from
1117 * the ULD.
1119 int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
1121 struct scsi_cmnd *cmd;
1122 int ret = scsi_prep_state_check(sdev, req);
1124 if (ret != BLKPREP_OK)
1125 return ret;
1127 * Filesystem requests must transfer data.
1129 BUG_ON(!req->nr_phys_segments);
1131 cmd = scsi_get_cmd_from_req(sdev, req);
1132 if (unlikely(!cmd))
1133 return BLKPREP_DEFER;
1135 return scsi_init_io(cmd);
1137 EXPORT_SYMBOL(scsi_setup_fs_cmnd);
1139 int scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
1141 int ret = BLKPREP_OK;
1144 * If the device is not in running state we will reject some
1145 * or all commands.
1147 if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
1148 switch (sdev->sdev_state) {
1149 case SDEV_OFFLINE:
1151 * If the device is offline we refuse to process any
1152 * commands. The device must be brought online
1153 * before trying any recovery commands.
1155 sdev_printk(KERN_ERR, sdev,
1156 "rejecting I/O to offline device\n");
1157 ret = BLKPREP_KILL;
1158 break;
1159 case SDEV_DEL:
1161 * If the device is fully deleted, we refuse to
1162 * process any commands as well.
1164 sdev_printk(KERN_ERR, sdev,
1165 "rejecting I/O to dead device\n");
1166 ret = BLKPREP_KILL;
1167 break;
1168 case SDEV_QUIESCE:
1169 case SDEV_BLOCK:
1171 * If the devices is blocked we defer normal commands.
1173 if (!(req->cmd_flags & REQ_PREEMPT))
1174 ret = BLKPREP_DEFER;
1175 break;
1176 default:
1178 * For any other not fully online state we only allow
1179 * special commands. In particular any user initiated
1180 * command is not allowed.
1182 if (!(req->cmd_flags & REQ_PREEMPT))
1183 ret = BLKPREP_KILL;
1184 break;
1187 return ret;
1189 EXPORT_SYMBOL(scsi_prep_state_check);
1191 int scsi_prep_return(struct request_queue *q, struct request *req, int ret)
1193 struct scsi_device *sdev = q->queuedata;
1195 switch (ret) {
1196 case BLKPREP_KILL:
1197 req->errors = DID_NO_CONNECT << 16;
1198 /* release the command and kill it */
1199 if (req->special) {
1200 struct scsi_cmnd *cmd = req->special;
1201 scsi_release_buffers(cmd);
1202 scsi_put_command(cmd);
1203 req->special = NULL;
1205 break;
1206 case BLKPREP_DEFER:
1208 * If we defer, the elv_next_request() returns NULL, but the
1209 * queue must be restarted, so we plug here if no returning
1210 * command will automatically do that.
1212 if (sdev->device_busy == 0)
1213 blk_plug_device(q);
1214 break;
1215 default:
1216 req->cmd_flags |= REQ_DONTPREP;
1219 return ret;
1221 EXPORT_SYMBOL(scsi_prep_return);
1223 int scsi_prep_fn(struct request_queue *q, struct request *req)
1225 struct scsi_device *sdev = q->queuedata;
1226 int ret = BLKPREP_KILL;
1228 if (req->cmd_type == REQ_TYPE_BLOCK_PC)
1229 ret = scsi_setup_blk_pc_cmnd(sdev, req);
1230 return scsi_prep_return(q, req, ret);
1234 * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1235 * return 0.
1237 * Called with the queue_lock held.
1239 static inline int scsi_dev_queue_ready(struct request_queue *q,
1240 struct scsi_device *sdev)
1242 if (sdev->device_busy >= sdev->queue_depth)
1243 return 0;
1244 if (sdev->device_busy == 0 && sdev->device_blocked) {
1246 * unblock after device_blocked iterates to zero
1248 if (--sdev->device_blocked == 0) {
1249 SCSI_LOG_MLQUEUE(3,
1250 sdev_printk(KERN_INFO, sdev,
1251 "unblocking device at zero depth\n"));
1252 } else {
1253 blk_plug_device(q);
1254 return 0;
1257 if (sdev->device_blocked)
1258 return 0;
1260 return 1;
1264 * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1265 * return 0. We must end up running the queue again whenever 0 is
1266 * returned, else IO can hang.
1268 * Called with host_lock held.
1270 static inline int scsi_host_queue_ready(struct request_queue *q,
1271 struct Scsi_Host *shost,
1272 struct scsi_device *sdev)
1274 if (scsi_host_in_recovery(shost))
1275 return 0;
1276 if (shost->host_busy == 0 && shost->host_blocked) {
1278 * unblock after host_blocked iterates to zero
1280 if (--shost->host_blocked == 0) {
1281 SCSI_LOG_MLQUEUE(3,
1282 printk("scsi%d unblocking host at zero depth\n",
1283 shost->host_no));
1284 } else {
1285 blk_plug_device(q);
1286 return 0;
1289 if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
1290 shost->host_blocked || shost->host_self_blocked) {
1291 if (list_empty(&sdev->starved_entry))
1292 list_add_tail(&sdev->starved_entry, &shost->starved_list);
1293 return 0;
1296 /* We're OK to process the command, so we can't be starved */
1297 if (!list_empty(&sdev->starved_entry))
1298 list_del_init(&sdev->starved_entry);
1300 return 1;
1304 * Kill a request for a dead device
1306 static void scsi_kill_request(struct request *req, struct request_queue *q)
1308 struct scsi_cmnd *cmd = req->special;
1309 struct scsi_device *sdev = cmd->device;
1310 struct Scsi_Host *shost = sdev->host;
1312 blkdev_dequeue_request(req);
1314 if (unlikely(cmd == NULL)) {
1315 printk(KERN_CRIT "impossible request in %s.\n",
1316 __FUNCTION__);
1317 BUG();
1320 scsi_init_cmd_errh(cmd);
1321 cmd->result = DID_NO_CONNECT << 16;
1322 atomic_inc(&cmd->device->iorequest_cnt);
1325 * SCSI request completion path will do scsi_device_unbusy(),
1326 * bump busy counts. To bump the counters, we need to dance
1327 * with the locks as normal issue path does.
1329 sdev->device_busy++;
1330 spin_unlock(sdev->request_queue->queue_lock);
1331 spin_lock(shost->host_lock);
1332 shost->host_busy++;
1333 spin_unlock(shost->host_lock);
1334 spin_lock(sdev->request_queue->queue_lock);
1336 __scsi_done(cmd);
1339 static void scsi_softirq_done(struct request *rq)
1341 struct scsi_cmnd *cmd = rq->completion_data;
1342 unsigned long wait_for = (cmd->allowed + 1) * cmd->timeout_per_command;
1343 int disposition;
1345 INIT_LIST_HEAD(&cmd->eh_entry);
1347 disposition = scsi_decide_disposition(cmd);
1348 if (disposition != SUCCESS &&
1349 time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
1350 sdev_printk(KERN_ERR, cmd->device,
1351 "timing out command, waited %lus\n",
1352 wait_for/HZ);
1353 disposition = SUCCESS;
1356 scsi_log_completion(cmd, disposition);
1358 switch (disposition) {
1359 case SUCCESS:
1360 scsi_finish_command(cmd);
1361 break;
1362 case NEEDS_RETRY:
1363 scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY);
1364 break;
1365 case ADD_TO_MLQUEUE:
1366 scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
1367 break;
1368 default:
1369 if (!scsi_eh_scmd_add(cmd, 0))
1370 scsi_finish_command(cmd);
1375 * Function: scsi_request_fn()
1377 * Purpose: Main strategy routine for SCSI.
1379 * Arguments: q - Pointer to actual queue.
1381 * Returns: Nothing
1383 * Lock status: IO request lock assumed to be held when called.
1385 static void scsi_request_fn(struct request_queue *q)
1387 struct scsi_device *sdev = q->queuedata;
1388 struct Scsi_Host *shost;
1389 struct scsi_cmnd *cmd;
1390 struct request *req;
1392 if (!sdev) {
1393 printk("scsi: killing requests for dead queue\n");
1394 while ((req = elv_next_request(q)) != NULL)
1395 scsi_kill_request(req, q);
1396 return;
1399 if(!get_device(&sdev->sdev_gendev))
1400 /* We must be tearing the block queue down already */
1401 return;
1404 * To start with, we keep looping until the queue is empty, or until
1405 * the host is no longer able to accept any more requests.
1407 shost = sdev->host;
1408 while (!blk_queue_plugged(q)) {
1409 int rtn;
1411 * get next queueable request. We do this early to make sure
1412 * that the request is fully prepared even if we cannot
1413 * accept it.
1415 req = elv_next_request(q);
1416 if (!req || !scsi_dev_queue_ready(q, sdev))
1417 break;
1419 if (unlikely(!scsi_device_online(sdev))) {
1420 sdev_printk(KERN_ERR, sdev,
1421 "rejecting I/O to offline device\n");
1422 scsi_kill_request(req, q);
1423 continue;
1428 * Remove the request from the request list.
1430 if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1431 blkdev_dequeue_request(req);
1432 sdev->device_busy++;
1434 spin_unlock(q->queue_lock);
1435 cmd = req->special;
1436 if (unlikely(cmd == NULL)) {
1437 printk(KERN_CRIT "impossible request in %s.\n"
1438 "please mail a stack trace to "
1439 "linux-scsi@vger.kernel.org\n",
1440 __FUNCTION__);
1441 blk_dump_rq_flags(req, "foo");
1442 BUG();
1444 spin_lock(shost->host_lock);
1446 if (!scsi_host_queue_ready(q, shost, sdev))
1447 goto not_ready;
1448 if (scsi_target(sdev)->single_lun) {
1449 if (scsi_target(sdev)->starget_sdev_user &&
1450 scsi_target(sdev)->starget_sdev_user != sdev)
1451 goto not_ready;
1452 scsi_target(sdev)->starget_sdev_user = sdev;
1454 shost->host_busy++;
1457 * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1458 * take the lock again.
1460 spin_unlock_irq(shost->host_lock);
1463 * Finally, initialize any error handling parameters, and set up
1464 * the timers for timeouts.
1466 scsi_init_cmd_errh(cmd);
1469 * Dispatch the command to the low-level driver.
1471 rtn = scsi_dispatch_cmd(cmd);
1472 spin_lock_irq(q->queue_lock);
1473 if(rtn) {
1474 /* we're refusing the command; because of
1475 * the way locks get dropped, we need to
1476 * check here if plugging is required */
1477 if(sdev->device_busy == 0)
1478 blk_plug_device(q);
1480 break;
1484 goto out;
1486 not_ready:
1487 spin_unlock_irq(shost->host_lock);
1490 * lock q, handle tag, requeue req, and decrement device_busy. We
1491 * must return with queue_lock held.
1493 * Decrementing device_busy without checking it is OK, as all such
1494 * cases (host limits or settings) should run the queue at some
1495 * later time.
1497 spin_lock_irq(q->queue_lock);
1498 blk_requeue_request(q, req);
1499 sdev->device_busy--;
1500 if(sdev->device_busy == 0)
1501 blk_plug_device(q);
1502 out:
1503 /* must be careful here...if we trigger the ->remove() function
1504 * we cannot be holding the q lock */
1505 spin_unlock_irq(q->queue_lock);
1506 put_device(&sdev->sdev_gendev);
1507 spin_lock_irq(q->queue_lock);
1510 u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1512 struct device *host_dev;
1513 u64 bounce_limit = 0xffffffff;
1515 if (shost->unchecked_isa_dma)
1516 return BLK_BOUNCE_ISA;
1518 * Platforms with virtual-DMA translation
1519 * hardware have no practical limit.
1521 if (!PCI_DMA_BUS_IS_PHYS)
1522 return BLK_BOUNCE_ANY;
1524 host_dev = scsi_get_device(shost);
1525 if (host_dev && host_dev->dma_mask)
1526 bounce_limit = *host_dev->dma_mask;
1528 return bounce_limit;
1530 EXPORT_SYMBOL(scsi_calculate_bounce_limit);
1532 struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
1533 request_fn_proc *request_fn)
1535 struct request_queue *q;
1537 q = blk_init_queue(request_fn, NULL);
1538 if (!q)
1539 return NULL;
1542 * this limit is imposed by hardware restrictions
1544 blk_queue_max_hw_segments(q, shost->sg_tablesize);
1547 * In the future, sg chaining support will be mandatory and this
1548 * ifdef can then go away. Right now we don't have all archs
1549 * converted, so better keep it safe.
1551 #ifdef ARCH_HAS_SG_CHAIN
1552 if (shost->use_sg_chaining)
1553 blk_queue_max_phys_segments(q, SCSI_MAX_SG_CHAIN_SEGMENTS);
1554 else
1555 blk_queue_max_phys_segments(q, SCSI_MAX_SG_SEGMENTS);
1556 #else
1557 blk_queue_max_phys_segments(q, SCSI_MAX_SG_SEGMENTS);
1558 #endif
1560 blk_queue_max_sectors(q, shost->max_sectors);
1561 blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1562 blk_queue_segment_boundary(q, shost->dma_boundary);
1564 if (!shost->use_clustering)
1565 clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
1568 * set a reasonable default alignment on word boundaries: the
1569 * host and device may alter it using
1570 * blk_queue_update_dma_alignment() later.
1572 blk_queue_dma_alignment(q, 0x03);
1574 return q;
1576 EXPORT_SYMBOL(__scsi_alloc_queue);
1578 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1580 struct request_queue *q;
1582 q = __scsi_alloc_queue(sdev->host, scsi_request_fn);
1583 if (!q)
1584 return NULL;
1586 blk_queue_prep_rq(q, scsi_prep_fn);
1587 blk_queue_softirq_done(q, scsi_softirq_done);
1588 return q;
1591 void scsi_free_queue(struct request_queue *q)
1593 blk_cleanup_queue(q);
1597 * Function: scsi_block_requests()
1599 * Purpose: Utility function used by low-level drivers to prevent further
1600 * commands from being queued to the device.
1602 * Arguments: shost - Host in question
1604 * Returns: Nothing
1606 * Lock status: No locks are assumed held.
1608 * Notes: There is no timer nor any other means by which the requests
1609 * get unblocked other than the low-level driver calling
1610 * scsi_unblock_requests().
1612 void scsi_block_requests(struct Scsi_Host *shost)
1614 shost->host_self_blocked = 1;
1616 EXPORT_SYMBOL(scsi_block_requests);
1619 * Function: scsi_unblock_requests()
1621 * Purpose: Utility function used by low-level drivers to allow further
1622 * commands from being queued to the device.
1624 * Arguments: shost - Host in question
1626 * Returns: Nothing
1628 * Lock status: No locks are assumed held.
1630 * Notes: There is no timer nor any other means by which the requests
1631 * get unblocked other than the low-level driver calling
1632 * scsi_unblock_requests().
1634 * This is done as an API function so that changes to the
1635 * internals of the scsi mid-layer won't require wholesale
1636 * changes to drivers that use this feature.
1638 void scsi_unblock_requests(struct Scsi_Host *shost)
1640 shost->host_self_blocked = 0;
1641 scsi_run_host_queues(shost);
1643 EXPORT_SYMBOL(scsi_unblock_requests);
1645 int __init scsi_init_queue(void)
1647 int i;
1649 scsi_io_context_cache = kmem_cache_create("scsi_io_context",
1650 sizeof(struct scsi_io_context),
1651 0, 0, NULL);
1652 if (!scsi_io_context_cache) {
1653 printk(KERN_ERR "SCSI: can't init scsi io context cache\n");
1654 return -ENOMEM;
1657 for (i = 0; i < SG_MEMPOOL_NR; i++) {
1658 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1659 int size = sgp->size * sizeof(struct scatterlist);
1661 sgp->slab = kmem_cache_create(sgp->name, size, 0,
1662 SLAB_HWCACHE_ALIGN, NULL);
1663 if (!sgp->slab) {
1664 printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1665 sgp->name);
1668 sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
1669 sgp->slab);
1670 if (!sgp->pool) {
1671 printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1672 sgp->name);
1676 return 0;
1679 void scsi_exit_queue(void)
1681 int i;
1683 kmem_cache_destroy(scsi_io_context_cache);
1685 for (i = 0; i < SG_MEMPOOL_NR; i++) {
1686 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1687 mempool_destroy(sgp->pool);
1688 kmem_cache_destroy(sgp->slab);
1693 * scsi_mode_select - issue a mode select
1694 * @sdev: SCSI device to be queried
1695 * @pf: Page format bit (1 == standard, 0 == vendor specific)
1696 * @sp: Save page bit (0 == don't save, 1 == save)
1697 * @modepage: mode page being requested
1698 * @buffer: request buffer (may not be smaller than eight bytes)
1699 * @len: length of request buffer.
1700 * @timeout: command timeout
1701 * @retries: number of retries before failing
1702 * @data: returns a structure abstracting the mode header data
1703 * @sshdr: place to put sense data (or NULL if no sense to be collected).
1704 * must be SCSI_SENSE_BUFFERSIZE big.
1706 * Returns zero if successful; negative error number or scsi
1707 * status on error
1711 scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
1712 unsigned char *buffer, int len, int timeout, int retries,
1713 struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1715 unsigned char cmd[10];
1716 unsigned char *real_buffer;
1717 int ret;
1719 memset(cmd, 0, sizeof(cmd));
1720 cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
1722 if (sdev->use_10_for_ms) {
1723 if (len > 65535)
1724 return -EINVAL;
1725 real_buffer = kmalloc(8 + len, GFP_KERNEL);
1726 if (!real_buffer)
1727 return -ENOMEM;
1728 memcpy(real_buffer + 8, buffer, len);
1729 len += 8;
1730 real_buffer[0] = 0;
1731 real_buffer[1] = 0;
1732 real_buffer[2] = data->medium_type;
1733 real_buffer[3] = data->device_specific;
1734 real_buffer[4] = data->longlba ? 0x01 : 0;
1735 real_buffer[5] = 0;
1736 real_buffer[6] = data->block_descriptor_length >> 8;
1737 real_buffer[7] = data->block_descriptor_length;
1739 cmd[0] = MODE_SELECT_10;
1740 cmd[7] = len >> 8;
1741 cmd[8] = len;
1742 } else {
1743 if (len > 255 || data->block_descriptor_length > 255 ||
1744 data->longlba)
1745 return -EINVAL;
1747 real_buffer = kmalloc(4 + len, GFP_KERNEL);
1748 if (!real_buffer)
1749 return -ENOMEM;
1750 memcpy(real_buffer + 4, buffer, len);
1751 len += 4;
1752 real_buffer[0] = 0;
1753 real_buffer[1] = data->medium_type;
1754 real_buffer[2] = data->device_specific;
1755 real_buffer[3] = data->block_descriptor_length;
1758 cmd[0] = MODE_SELECT;
1759 cmd[4] = len;
1762 ret = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, real_buffer, len,
1763 sshdr, timeout, retries);
1764 kfree(real_buffer);
1765 return ret;
1767 EXPORT_SYMBOL_GPL(scsi_mode_select);
1770 * scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
1771 * @sdev: SCSI device to be queried
1772 * @dbd: set if mode sense will allow block descriptors to be returned
1773 * @modepage: mode page being requested
1774 * @buffer: request buffer (may not be smaller than eight bytes)
1775 * @len: length of request buffer.
1776 * @timeout: command timeout
1777 * @retries: number of retries before failing
1778 * @data: returns a structure abstracting the mode header data
1779 * @sshdr: place to put sense data (or NULL if no sense to be collected).
1780 * must be SCSI_SENSE_BUFFERSIZE big.
1782 * Returns zero if unsuccessful, or the header offset (either 4
1783 * or 8 depending on whether a six or ten byte command was
1784 * issued) if successful.
1787 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
1788 unsigned char *buffer, int len, int timeout, int retries,
1789 struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1791 unsigned char cmd[12];
1792 int use_10_for_ms;
1793 int header_length;
1794 int result;
1795 struct scsi_sense_hdr my_sshdr;
1797 memset(data, 0, sizeof(*data));
1798 memset(&cmd[0], 0, 12);
1799 cmd[1] = dbd & 0x18; /* allows DBD and LLBA bits */
1800 cmd[2] = modepage;
1802 /* caller might not be interested in sense, but we need it */
1803 if (!sshdr)
1804 sshdr = &my_sshdr;
1806 retry:
1807 use_10_for_ms = sdev->use_10_for_ms;
1809 if (use_10_for_ms) {
1810 if (len < 8)
1811 len = 8;
1813 cmd[0] = MODE_SENSE_10;
1814 cmd[8] = len;
1815 header_length = 8;
1816 } else {
1817 if (len < 4)
1818 len = 4;
1820 cmd[0] = MODE_SENSE;
1821 cmd[4] = len;
1822 header_length = 4;
1825 memset(buffer, 0, len);
1827 result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
1828 sshdr, timeout, retries);
1830 /* This code looks awful: what it's doing is making sure an
1831 * ILLEGAL REQUEST sense return identifies the actual command
1832 * byte as the problem. MODE_SENSE commands can return
1833 * ILLEGAL REQUEST if the code page isn't supported */
1835 if (use_10_for_ms && !scsi_status_is_good(result) &&
1836 (driver_byte(result) & DRIVER_SENSE)) {
1837 if (scsi_sense_valid(sshdr)) {
1838 if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
1839 (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
1841 * Invalid command operation code
1843 sdev->use_10_for_ms = 0;
1844 goto retry;
1849 if(scsi_status_is_good(result)) {
1850 if (unlikely(buffer[0] == 0x86 && buffer[1] == 0x0b &&
1851 (modepage == 6 || modepage == 8))) {
1852 /* Initio breakage? */
1853 header_length = 0;
1854 data->length = 13;
1855 data->medium_type = 0;
1856 data->device_specific = 0;
1857 data->longlba = 0;
1858 data->block_descriptor_length = 0;
1859 } else if(use_10_for_ms) {
1860 data->length = buffer[0]*256 + buffer[1] + 2;
1861 data->medium_type = buffer[2];
1862 data->device_specific = buffer[3];
1863 data->longlba = buffer[4] & 0x01;
1864 data->block_descriptor_length = buffer[6]*256
1865 + buffer[7];
1866 } else {
1867 data->length = buffer[0] + 1;
1868 data->medium_type = buffer[1];
1869 data->device_specific = buffer[2];
1870 data->block_descriptor_length = buffer[3];
1872 data->header_length = header_length;
1875 return result;
1877 EXPORT_SYMBOL(scsi_mode_sense);
1880 * scsi_test_unit_ready - test if unit is ready
1881 * @sdev: scsi device to change the state of.
1882 * @timeout: command timeout
1883 * @retries: number of retries before failing
1884 * @sshdr_external: Optional pointer to struct scsi_sense_hdr for
1885 * returning sense. Make sure that this is cleared before passing
1886 * in.
1888 * Returns zero if unsuccessful or an error if TUR failed. For
1889 * removable media, a return of NOT_READY or UNIT_ATTENTION is
1890 * translated to success, with the ->changed flag updated.
1893 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries,
1894 struct scsi_sense_hdr *sshdr_external)
1896 char cmd[] = {
1897 TEST_UNIT_READY, 0, 0, 0, 0, 0,
1899 struct scsi_sense_hdr *sshdr;
1900 int result;
1902 if (!sshdr_external)
1903 sshdr = kzalloc(sizeof(*sshdr), GFP_KERNEL);
1904 else
1905 sshdr = sshdr_external;
1907 /* try to eat the UNIT_ATTENTION if there are enough retries */
1908 do {
1909 result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
1910 timeout, retries);
1911 } while ((driver_byte(result) & DRIVER_SENSE) &&
1912 sshdr && sshdr->sense_key == UNIT_ATTENTION &&
1913 --retries);
1915 if (!sshdr)
1916 /* could not allocate sense buffer, so can't process it */
1917 return result;
1919 if ((driver_byte(result) & DRIVER_SENSE) && sdev->removable) {
1921 if ((scsi_sense_valid(sshdr)) &&
1922 ((sshdr->sense_key == UNIT_ATTENTION) ||
1923 (sshdr->sense_key == NOT_READY))) {
1924 sdev->changed = 1;
1925 result = 0;
1928 if (!sshdr_external)
1929 kfree(sshdr);
1930 return result;
1932 EXPORT_SYMBOL(scsi_test_unit_ready);
1935 * scsi_device_set_state - Take the given device through the device state model.
1936 * @sdev: scsi device to change the state of.
1937 * @state: state to change to.
1939 * Returns zero if unsuccessful or an error if the requested
1940 * transition is illegal.
1943 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
1945 enum scsi_device_state oldstate = sdev->sdev_state;
1947 if (state == oldstate)
1948 return 0;
1950 switch (state) {
1951 case SDEV_CREATED:
1952 /* There are no legal states that come back to
1953 * created. This is the manually initialised start
1954 * state */
1955 goto illegal;
1957 case SDEV_RUNNING:
1958 switch (oldstate) {
1959 case SDEV_CREATED:
1960 case SDEV_OFFLINE:
1961 case SDEV_QUIESCE:
1962 case SDEV_BLOCK:
1963 break;
1964 default:
1965 goto illegal;
1967 break;
1969 case SDEV_QUIESCE:
1970 switch (oldstate) {
1971 case SDEV_RUNNING:
1972 case SDEV_OFFLINE:
1973 break;
1974 default:
1975 goto illegal;
1977 break;
1979 case SDEV_OFFLINE:
1980 switch (oldstate) {
1981 case SDEV_CREATED:
1982 case SDEV_RUNNING:
1983 case SDEV_QUIESCE:
1984 case SDEV_BLOCK:
1985 break;
1986 default:
1987 goto illegal;
1989 break;
1991 case SDEV_BLOCK:
1992 switch (oldstate) {
1993 case SDEV_CREATED:
1994 case SDEV_RUNNING:
1995 break;
1996 default:
1997 goto illegal;
1999 break;
2001 case SDEV_CANCEL:
2002 switch (oldstate) {
2003 case SDEV_CREATED:
2004 case SDEV_RUNNING:
2005 case SDEV_QUIESCE:
2006 case SDEV_OFFLINE:
2007 case SDEV_BLOCK:
2008 break;
2009 default:
2010 goto illegal;
2012 break;
2014 case SDEV_DEL:
2015 switch (oldstate) {
2016 case SDEV_CREATED:
2017 case SDEV_RUNNING:
2018 case SDEV_OFFLINE:
2019 case SDEV_CANCEL:
2020 break;
2021 default:
2022 goto illegal;
2024 break;
2027 sdev->sdev_state = state;
2028 return 0;
2030 illegal:
2031 SCSI_LOG_ERROR_RECOVERY(1,
2032 sdev_printk(KERN_ERR, sdev,
2033 "Illegal state transition %s->%s\n",
2034 scsi_device_state_name(oldstate),
2035 scsi_device_state_name(state))
2037 return -EINVAL;
2039 EXPORT_SYMBOL(scsi_device_set_state);
2042 * sdev_evt_emit - emit a single SCSI device uevent
2043 * @sdev: associated SCSI device
2044 * @evt: event to emit
2046 * Send a single uevent (scsi_event) to the associated scsi_device.
2048 static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
2050 int idx = 0;
2051 char *envp[3];
2053 switch (evt->evt_type) {
2054 case SDEV_EVT_MEDIA_CHANGE:
2055 envp[idx++] = "SDEV_MEDIA_CHANGE=1";
2056 break;
2058 default:
2059 /* do nothing */
2060 break;
2063 envp[idx++] = NULL;
2065 kobject_uevent_env(&sdev->sdev_gendev.kobj, KOBJ_CHANGE, envp);
2069 * sdev_evt_thread - send a uevent for each scsi event
2070 * @work: work struct for scsi_device
2072 * Dispatch queued events to their associated scsi_device kobjects
2073 * as uevents.
2075 void scsi_evt_thread(struct work_struct *work)
2077 struct scsi_device *sdev;
2078 LIST_HEAD(event_list);
2080 sdev = container_of(work, struct scsi_device, event_work);
2082 while (1) {
2083 struct scsi_event *evt;
2084 struct list_head *this, *tmp;
2085 unsigned long flags;
2087 spin_lock_irqsave(&sdev->list_lock, flags);
2088 list_splice_init(&sdev->event_list, &event_list);
2089 spin_unlock_irqrestore(&sdev->list_lock, flags);
2091 if (list_empty(&event_list))
2092 break;
2094 list_for_each_safe(this, tmp, &event_list) {
2095 evt = list_entry(this, struct scsi_event, node);
2096 list_del(&evt->node);
2097 scsi_evt_emit(sdev, evt);
2098 kfree(evt);
2104 * sdev_evt_send - send asserted event to uevent thread
2105 * @sdev: scsi_device event occurred on
2106 * @evt: event to send
2108 * Assert scsi device event asynchronously.
2110 void sdev_evt_send(struct scsi_device *sdev, struct scsi_event *evt)
2112 unsigned long flags;
2114 if (!test_bit(evt->evt_type, sdev->supported_events)) {
2115 kfree(evt);
2116 return;
2119 spin_lock_irqsave(&sdev->list_lock, flags);
2120 list_add_tail(&evt->node, &sdev->event_list);
2121 schedule_work(&sdev->event_work);
2122 spin_unlock_irqrestore(&sdev->list_lock, flags);
2124 EXPORT_SYMBOL_GPL(sdev_evt_send);
2127 * sdev_evt_alloc - allocate a new scsi event
2128 * @evt_type: type of event to allocate
2129 * @gfpflags: GFP flags for allocation
2131 * Allocates and returns a new scsi_event.
2133 struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
2134 gfp_t gfpflags)
2136 struct scsi_event *evt = kzalloc(sizeof(struct scsi_event), gfpflags);
2137 if (!evt)
2138 return NULL;
2140 evt->evt_type = evt_type;
2141 INIT_LIST_HEAD(&evt->node);
2143 /* evt_type-specific initialization, if any */
2144 switch (evt_type) {
2145 case SDEV_EVT_MEDIA_CHANGE:
2146 default:
2147 /* do nothing */
2148 break;
2151 return evt;
2153 EXPORT_SYMBOL_GPL(sdev_evt_alloc);
2156 * sdev_evt_send_simple - send asserted event to uevent thread
2157 * @sdev: scsi_device event occurred on
2158 * @evt_type: type of event to send
2159 * @gfpflags: GFP flags for allocation
2161 * Assert scsi device event asynchronously, given an event type.
2163 void sdev_evt_send_simple(struct scsi_device *sdev,
2164 enum scsi_device_event evt_type, gfp_t gfpflags)
2166 struct scsi_event *evt = sdev_evt_alloc(evt_type, gfpflags);
2167 if (!evt) {
2168 sdev_printk(KERN_ERR, sdev, "event %d eaten due to OOM\n",
2169 evt_type);
2170 return;
2173 sdev_evt_send(sdev, evt);
2175 EXPORT_SYMBOL_GPL(sdev_evt_send_simple);
2178 * scsi_device_quiesce - Block user issued commands.
2179 * @sdev: scsi device to quiesce.
2181 * This works by trying to transition to the SDEV_QUIESCE state
2182 * (which must be a legal transition). When the device is in this
2183 * state, only special requests will be accepted, all others will
2184 * be deferred. Since special requests may also be requeued requests,
2185 * a successful return doesn't guarantee the device will be
2186 * totally quiescent.
2188 * Must be called with user context, may sleep.
2190 * Returns zero if unsuccessful or an error if not.
2193 scsi_device_quiesce(struct scsi_device *sdev)
2195 int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
2196 if (err)
2197 return err;
2199 scsi_run_queue(sdev->request_queue);
2200 while (sdev->device_busy) {
2201 msleep_interruptible(200);
2202 scsi_run_queue(sdev->request_queue);
2204 return 0;
2206 EXPORT_SYMBOL(scsi_device_quiesce);
2209 * scsi_device_resume - Restart user issued commands to a quiesced device.
2210 * @sdev: scsi device to resume.
2212 * Moves the device from quiesced back to running and restarts the
2213 * queues.
2215 * Must be called with user context, may sleep.
2217 void
2218 scsi_device_resume(struct scsi_device *sdev)
2220 if(scsi_device_set_state(sdev, SDEV_RUNNING))
2221 return;
2222 scsi_run_queue(sdev->request_queue);
2224 EXPORT_SYMBOL(scsi_device_resume);
2226 static void
2227 device_quiesce_fn(struct scsi_device *sdev, void *data)
2229 scsi_device_quiesce(sdev);
2232 void
2233 scsi_target_quiesce(struct scsi_target *starget)
2235 starget_for_each_device(starget, NULL, device_quiesce_fn);
2237 EXPORT_SYMBOL(scsi_target_quiesce);
2239 static void
2240 device_resume_fn(struct scsi_device *sdev, void *data)
2242 scsi_device_resume(sdev);
2245 void
2246 scsi_target_resume(struct scsi_target *starget)
2248 starget_for_each_device(starget, NULL, device_resume_fn);
2250 EXPORT_SYMBOL(scsi_target_resume);
2253 * scsi_internal_device_block - internal function to put a device temporarily into the SDEV_BLOCK state
2254 * @sdev: device to block
2256 * Block request made by scsi lld's to temporarily stop all
2257 * scsi commands on the specified device. Called from interrupt
2258 * or normal process context.
2260 * Returns zero if successful or error if not
2262 * Notes:
2263 * This routine transitions the device to the SDEV_BLOCK state
2264 * (which must be a legal transition). When the device is in this
2265 * state, all commands are deferred until the scsi lld reenables
2266 * the device with scsi_device_unblock or device_block_tmo fires.
2267 * This routine assumes the host_lock is held on entry.
2270 scsi_internal_device_block(struct scsi_device *sdev)
2272 struct request_queue *q = sdev->request_queue;
2273 unsigned long flags;
2274 int err = 0;
2276 err = scsi_device_set_state(sdev, SDEV_BLOCK);
2277 if (err)
2278 return err;
2281 * The device has transitioned to SDEV_BLOCK. Stop the
2282 * block layer from calling the midlayer with this device's
2283 * request queue.
2285 spin_lock_irqsave(q->queue_lock, flags);
2286 blk_stop_queue(q);
2287 spin_unlock_irqrestore(q->queue_lock, flags);
2289 return 0;
2291 EXPORT_SYMBOL_GPL(scsi_internal_device_block);
2294 * scsi_internal_device_unblock - resume a device after a block request
2295 * @sdev: device to resume
2297 * Called by scsi lld's or the midlayer to restart the device queue
2298 * for the previously suspended scsi device. Called from interrupt or
2299 * normal process context.
2301 * Returns zero if successful or error if not.
2303 * Notes:
2304 * This routine transitions the device to the SDEV_RUNNING state
2305 * (which must be a legal transition) allowing the midlayer to
2306 * goose the queue for this device. This routine assumes the
2307 * host_lock is held upon entry.
2310 scsi_internal_device_unblock(struct scsi_device *sdev)
2312 struct request_queue *q = sdev->request_queue;
2313 int err;
2314 unsigned long flags;
2317 * Try to transition the scsi device to SDEV_RUNNING
2318 * and goose the device queue if successful.
2320 err = scsi_device_set_state(sdev, SDEV_RUNNING);
2321 if (err)
2322 return err;
2324 spin_lock_irqsave(q->queue_lock, flags);
2325 blk_start_queue(q);
2326 spin_unlock_irqrestore(q->queue_lock, flags);
2328 return 0;
2330 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
2332 static void
2333 device_block(struct scsi_device *sdev, void *data)
2335 scsi_internal_device_block(sdev);
2338 static int
2339 target_block(struct device *dev, void *data)
2341 if (scsi_is_target_device(dev))
2342 starget_for_each_device(to_scsi_target(dev), NULL,
2343 device_block);
2344 return 0;
2347 void
2348 scsi_target_block(struct device *dev)
2350 if (scsi_is_target_device(dev))
2351 starget_for_each_device(to_scsi_target(dev), NULL,
2352 device_block);
2353 else
2354 device_for_each_child(dev, NULL, target_block);
2356 EXPORT_SYMBOL_GPL(scsi_target_block);
2358 static void
2359 device_unblock(struct scsi_device *sdev, void *data)
2361 scsi_internal_device_unblock(sdev);
2364 static int
2365 target_unblock(struct device *dev, void *data)
2367 if (scsi_is_target_device(dev))
2368 starget_for_each_device(to_scsi_target(dev), NULL,
2369 device_unblock);
2370 return 0;
2373 void
2374 scsi_target_unblock(struct device *dev)
2376 if (scsi_is_target_device(dev))
2377 starget_for_each_device(to_scsi_target(dev), NULL,
2378 device_unblock);
2379 else
2380 device_for_each_child(dev, NULL, target_unblock);
2382 EXPORT_SYMBOL_GPL(scsi_target_unblock);
2385 * scsi_kmap_atomic_sg - find and atomically map an sg-elemnt
2386 * @sgl: scatter-gather list
2387 * @sg_count: number of segments in sg
2388 * @offset: offset in bytes into sg, on return offset into the mapped area
2389 * @len: bytes to map, on return number of bytes mapped
2391 * Returns virtual address of the start of the mapped page
2393 void *scsi_kmap_atomic_sg(struct scatterlist *sgl, int sg_count,
2394 size_t *offset, size_t *len)
2396 int i;
2397 size_t sg_len = 0, len_complete = 0;
2398 struct scatterlist *sg;
2399 struct page *page;
2401 WARN_ON(!irqs_disabled());
2403 for_each_sg(sgl, sg, sg_count, i) {
2404 len_complete = sg_len; /* Complete sg-entries */
2405 sg_len += sg->length;
2406 if (sg_len > *offset)
2407 break;
2410 if (unlikely(i == sg_count)) {
2411 printk(KERN_ERR "%s: Bytes in sg: %zu, requested offset %zu, "
2412 "elements %d\n",
2413 __FUNCTION__, sg_len, *offset, sg_count);
2414 WARN_ON(1);
2415 return NULL;
2418 /* Offset starting from the beginning of first page in this sg-entry */
2419 *offset = *offset - len_complete + sg->offset;
2421 /* Assumption: contiguous pages can be accessed as "page + i" */
2422 page = nth_page(sg_page(sg), (*offset >> PAGE_SHIFT));
2423 *offset &= ~PAGE_MASK;
2425 /* Bytes in this sg-entry from *offset to the end of the page */
2426 sg_len = PAGE_SIZE - *offset;
2427 if (*len > sg_len)
2428 *len = sg_len;
2430 return kmap_atomic(page, KM_BIO_SRC_IRQ);
2432 EXPORT_SYMBOL(scsi_kmap_atomic_sg);
2435 * scsi_kunmap_atomic_sg - atomically unmap a virtual address, previously mapped with scsi_kmap_atomic_sg
2436 * @virt: virtual address to be unmapped
2438 void scsi_kunmap_atomic_sg(void *virt)
2440 kunmap_atomic(virt, KM_BIO_SRC_IRQ);
2442 EXPORT_SYMBOL(scsi_kunmap_atomic_sg);