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.
10 #include <linux/bio.h>
11 #include <linux/bitops.h>
12 #include <linux/blkdev.h>
13 #include <linux/completion.h>
14 #include <linux/kernel.h>
15 #include <linux/mempool.h>
16 #include <linux/slab.h>
17 #include <linux/init.h>
18 #include <linux/pci.h>
19 #include <linux/delay.h>
20 #include <linux/hardirq.h>
21 #include <linux/scatterlist.h>
23 #include <scsi/scsi.h>
24 #include <scsi/scsi_cmnd.h>
25 #include <scsi/scsi_dbg.h>
26 #include <scsi/scsi_device.h>
27 #include <scsi/scsi_driver.h>
28 #include <scsi/scsi_eh.h>
29 #include <scsi/scsi_host.h>
31 #include "scsi_priv.h"
32 #include "scsi_logging.h"
35 #define SG_MEMPOOL_NR ARRAY_SIZE(scsi_sg_pools)
36 #define SG_MEMPOOL_SIZE 2
38 struct scsi_host_sg_pool {
41 struct kmem_cache *slab;
45 #define SP(x) { x, "sgpool-" __stringify(x) }
46 #if (SCSI_MAX_SG_SEGMENTS < 32)
47 #error SCSI_MAX_SG_SEGMENTS is too small (must be 32 or greater)
49 static struct scsi_host_sg_pool scsi_sg_pools[] = {
52 #if (SCSI_MAX_SG_SEGMENTS > 32)
54 #if (SCSI_MAX_SG_SEGMENTS > 64)
56 #if (SCSI_MAX_SG_SEGMENTS > 128)
58 #if (SCSI_MAX_SG_SEGMENTS > 256)
59 #error SCSI_MAX_SG_SEGMENTS is too large (256 MAX)
64 SP(SCSI_MAX_SG_SEGMENTS)
68 struct kmem_cache *scsi_sdb_cache;
70 static void scsi_run_queue(struct request_queue *q);
73 * Function: scsi_unprep_request()
75 * Purpose: Remove all preparation done for a request, including its
76 * associated scsi_cmnd, so that it can be requeued.
78 * Arguments: req - request to unprepare
80 * Lock status: Assumed that no locks are held upon entry.
84 static void scsi_unprep_request(struct request *req)
86 struct scsi_cmnd *cmd = req->special;
88 req->cmd_flags &= ~REQ_DONTPREP;
91 scsi_put_command(cmd);
95 * __scsi_queue_insert - private queue insertion
96 * @cmd: The SCSI command being requeued
97 * @reason: The reason for the requeue
98 * @unbusy: Whether the queue should be unbusied
100 * This is a private queue insertion. The public interface
101 * scsi_queue_insert() always assumes the queue should be unbusied
102 * because it's always called before the completion. This function is
103 * for a requeue after completion, which should only occur in this
106 static int __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)
108 struct Scsi_Host *host = cmd->device->host;
109 struct scsi_device *device = cmd->device;
110 struct scsi_target *starget = scsi_target(device);
111 struct request_queue *q = device->request_queue;
115 printk("Inserting command %p into mlqueue\n", cmd));
118 * Set the appropriate busy bit for the device/host.
120 * If the host/device isn't busy, assume that something actually
121 * completed, and that we should be able to queue a command now.
123 * Note that the prior mid-layer assumption that any host could
124 * always queue at least one command is now broken. The mid-layer
125 * will implement a user specifiable stall (see
126 * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
127 * if a command is requeued with no other commands outstanding
128 * either for the device or for the host.
131 case SCSI_MLQUEUE_HOST_BUSY:
132 host->host_blocked = host->max_host_blocked;
134 case SCSI_MLQUEUE_DEVICE_BUSY:
135 device->device_blocked = device->max_device_blocked;
137 case SCSI_MLQUEUE_TARGET_BUSY:
138 starget->target_blocked = starget->max_target_blocked;
143 * Decrement the counters, since these commands are no longer
144 * active on the host/device.
147 scsi_device_unbusy(device);
150 * Requeue this command. It will go before all other commands
151 * that are already in the queue.
153 * NOTE: there is magic here about the way the queue is plugged if
154 * we have no outstanding commands.
156 * Although we *don't* plug the queue, we call the request
157 * function. The SCSI request function detects the blocked condition
158 * and plugs the queue appropriately.
160 spin_lock_irqsave(q->queue_lock, flags);
161 blk_requeue_request(q, cmd->request);
162 spin_unlock_irqrestore(q->queue_lock, flags);
170 * Function: scsi_queue_insert()
172 * Purpose: Insert a command in the midlevel queue.
174 * Arguments: cmd - command that we are adding to queue.
175 * reason - why we are inserting command to queue.
177 * Lock status: Assumed that lock is not held upon entry.
181 * Notes: We do this for one of two cases. Either the host is busy
182 * and it cannot accept any more commands for the time being,
183 * or the device returned QUEUE_FULL and can accept no more
185 * Notes: This could be called either from an interrupt context or a
186 * normal process context.
188 int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
190 return __scsi_queue_insert(cmd, reason, 1);
193 * scsi_execute - insert request and wait for the result
196 * @data_direction: data direction
197 * @buffer: data buffer
198 * @bufflen: len of buffer
199 * @sense: optional sense buffer
200 * @timeout: request timeout in seconds
201 * @retries: number of times to retry request
202 * @flags: or into request flags;
203 * @resid: optional residual length
205 * returns the req->errors value which is the scsi_cmnd result
208 int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
209 int data_direction, void *buffer, unsigned bufflen,
210 unsigned char *sense, int timeout, int retries, int flags,
214 int write = (data_direction == DMA_TO_DEVICE);
215 int ret = DRIVER_ERROR << 24;
217 req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
219 if (bufflen && blk_rq_map_kern(sdev->request_queue, req,
220 buffer, bufflen, __GFP_WAIT))
223 req->cmd_len = COMMAND_SIZE(cmd[0]);
224 memcpy(req->cmd, cmd, req->cmd_len);
227 req->retries = retries;
228 req->timeout = timeout;
229 req->cmd_type = REQ_TYPE_BLOCK_PC;
230 req->cmd_flags |= flags | REQ_QUIET | REQ_PREEMPT;
233 * head injection *required* here otherwise quiesce won't work
235 blk_execute_rq(req->q, NULL, req, 1);
238 * Some devices (USB mass-storage in particular) may transfer
239 * garbage data together with a residue indicating that the data
240 * is invalid. Prevent the garbage from being misinterpreted
241 * and prevent security leaks by zeroing out the excess data.
243 if (unlikely(req->data_len > 0 && req->data_len <= bufflen))
244 memset(buffer + (bufflen - req->data_len), 0, req->data_len);
247 *resid = req->data_len;
250 blk_put_request(req);
254 EXPORT_SYMBOL(scsi_execute);
257 int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
258 int data_direction, void *buffer, unsigned bufflen,
259 struct scsi_sense_hdr *sshdr, int timeout, int retries,
266 sense = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
268 return DRIVER_ERROR << 24;
270 result = scsi_execute(sdev, cmd, data_direction, buffer, bufflen,
271 sense, timeout, retries, 0, resid);
273 scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, sshdr);
278 EXPORT_SYMBOL(scsi_execute_req);
280 struct scsi_io_context {
282 void (*done)(void *data, char *sense, int result, int resid);
283 char sense[SCSI_SENSE_BUFFERSIZE];
286 static struct kmem_cache *scsi_io_context_cache;
288 static void scsi_end_async(struct request *req, int uptodate)
290 struct scsi_io_context *sioc = req->end_io_data;
293 sioc->done(sioc->data, sioc->sense, req->errors, req->data_len);
295 kmem_cache_free(scsi_io_context_cache, sioc);
296 __blk_put_request(req->q, req);
299 static int scsi_merge_bio(struct request *rq, struct bio *bio)
301 struct request_queue *q = rq->q;
303 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
304 if (rq_data_dir(rq) == WRITE)
305 bio->bi_rw |= (1 << BIO_RW);
306 blk_queue_bounce(q, &bio);
308 return blk_rq_append_bio(q, rq, bio);
311 static void scsi_bi_endio(struct bio *bio, int error)
317 * scsi_req_map_sg - map a scatterlist into a request
318 * @rq: request to fill
320 * @nsegs: number of elements
321 * @bufflen: len of buffer
322 * @gfp: memory allocation flags
324 * scsi_req_map_sg maps a scatterlist into a request so that the
325 * request can be sent to the block layer. We do not trust the scatterlist
326 * sent to use, as some ULDs use that struct to only organize the pages.
328 static int scsi_req_map_sg(struct request *rq, struct scatterlist *sgl,
329 int nsegs, unsigned bufflen, gfp_t gfp)
331 struct request_queue *q = rq->q;
332 int nr_pages = (bufflen + sgl[0].offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
333 unsigned int data_len = bufflen, len, bytes, off;
334 struct scatterlist *sg;
336 struct bio *bio = NULL;
337 int i, err, nr_vecs = 0;
339 for_each_sg(sgl, sg, nsegs, i) {
344 while (len > 0 && data_len > 0) {
346 * sg sends a scatterlist that is larger than
347 * the data_len it wants transferred for certain
350 bytes = min_t(unsigned int, len, PAGE_SIZE - off);
351 bytes = min(bytes, data_len);
354 nr_vecs = min_t(int, BIO_MAX_PAGES, nr_pages);
357 bio = bio_alloc(gfp, nr_vecs);
362 bio->bi_end_io = scsi_bi_endio;
365 if (bio_add_pc_page(q, bio, page, bytes, off) !=
372 if (bio->bi_vcnt >= nr_vecs) {
373 err = scsi_merge_bio(rq, bio);
388 rq->buffer = rq->data = NULL;
389 rq->data_len = bufflen;
393 while ((bio = rq->bio) != NULL) {
394 rq->bio = bio->bi_next;
396 * call endio instead of bio_put incase it was bounced
405 * scsi_execute_async - insert request
408 * @cmd_len: length of scsi cdb
409 * @data_direction: DMA_TO_DEVICE, DMA_FROM_DEVICE, or DMA_NONE
410 * @buffer: data buffer (this can be a kernel buffer or scatterlist)
411 * @bufflen: len of buffer
412 * @use_sg: if buffer is a scatterlist this is the number of elements
413 * @timeout: request timeout in seconds
414 * @retries: number of times to retry request
415 * @privdata: data passed to done()
416 * @done: callback function when done
417 * @gfp: memory allocation flags
419 int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
420 int cmd_len, int data_direction, void *buffer, unsigned bufflen,
421 int use_sg, int timeout, int retries, void *privdata,
422 void (*done)(void *, char *, int, int), gfp_t gfp)
425 struct scsi_io_context *sioc;
427 int write = (data_direction == DMA_TO_DEVICE);
429 sioc = kmem_cache_zalloc(scsi_io_context_cache, gfp);
431 return DRIVER_ERROR << 24;
433 req = blk_get_request(sdev->request_queue, write, gfp);
436 req->cmd_type = REQ_TYPE_BLOCK_PC;
437 req->cmd_flags |= REQ_QUIET;
440 err = scsi_req_map_sg(req, buffer, use_sg, bufflen, gfp);
442 err = blk_rq_map_kern(req->q, req, buffer, bufflen, gfp);
447 req->cmd_len = cmd_len;
448 memset(req->cmd, 0, BLK_MAX_CDB); /* ATAPI hates garbage after CDB */
449 memcpy(req->cmd, cmd, req->cmd_len);
450 req->sense = sioc->sense;
452 req->timeout = timeout;
453 req->retries = retries;
454 req->end_io_data = sioc;
456 sioc->data = privdata;
459 blk_execute_rq_nowait(req->q, NULL, req, 1, scsi_end_async);
463 blk_put_request(req);
465 kmem_cache_free(scsi_io_context_cache, sioc);
466 return DRIVER_ERROR << 24;
468 EXPORT_SYMBOL_GPL(scsi_execute_async);
471 * Function: scsi_init_cmd_errh()
473 * Purpose: Initialize cmd fields related to error handling.
475 * Arguments: cmd - command that is ready to be queued.
477 * Notes: This function has the job of initializing a number of
478 * fields related to error handling. Typically this will
479 * be called once for each command, as required.
481 static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
483 cmd->serial_number = 0;
484 scsi_set_resid(cmd, 0);
485 memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
486 if (cmd->cmd_len == 0)
487 cmd->cmd_len = scsi_command_size(cmd->cmnd);
490 void scsi_device_unbusy(struct scsi_device *sdev)
492 struct Scsi_Host *shost = sdev->host;
493 struct scsi_target *starget = scsi_target(sdev);
496 spin_lock_irqsave(shost->host_lock, flags);
498 starget->target_busy--;
499 if (unlikely(scsi_host_in_recovery(shost) &&
500 (shost->host_failed || shost->host_eh_scheduled)))
501 scsi_eh_wakeup(shost);
502 spin_unlock(shost->host_lock);
503 spin_lock(sdev->request_queue->queue_lock);
505 spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
509 * Called for single_lun devices on IO completion. Clear starget_sdev_user,
510 * and call blk_run_queue for all the scsi_devices on the target -
511 * including current_sdev first.
513 * Called with *no* scsi locks held.
515 static void scsi_single_lun_run(struct scsi_device *current_sdev)
517 struct Scsi_Host *shost = current_sdev->host;
518 struct scsi_device *sdev, *tmp;
519 struct scsi_target *starget = scsi_target(current_sdev);
522 spin_lock_irqsave(shost->host_lock, flags);
523 starget->starget_sdev_user = NULL;
524 spin_unlock_irqrestore(shost->host_lock, flags);
527 * Call blk_run_queue for all LUNs on the target, starting with
528 * current_sdev. We race with others (to set starget_sdev_user),
529 * but in most cases, we will be first. Ideally, each LU on the
530 * target would get some limited time or requests on the target.
532 blk_run_queue(current_sdev->request_queue);
534 spin_lock_irqsave(shost->host_lock, flags);
535 if (starget->starget_sdev_user)
537 list_for_each_entry_safe(sdev, tmp, &starget->devices,
538 same_target_siblings) {
539 if (sdev == current_sdev)
541 if (scsi_device_get(sdev))
544 spin_unlock_irqrestore(shost->host_lock, flags);
545 blk_run_queue(sdev->request_queue);
546 spin_lock_irqsave(shost->host_lock, flags);
548 scsi_device_put(sdev);
551 spin_unlock_irqrestore(shost->host_lock, flags);
554 static inline int scsi_device_is_busy(struct scsi_device *sdev)
556 if (sdev->device_busy >= sdev->queue_depth || sdev->device_blocked)
562 static inline int scsi_target_is_busy(struct scsi_target *starget)
564 return ((starget->can_queue > 0 &&
565 starget->target_busy >= starget->can_queue) ||
566 starget->target_blocked);
569 static inline int scsi_host_is_busy(struct Scsi_Host *shost)
571 if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
572 shost->host_blocked || shost->host_self_blocked)
579 * Function: scsi_run_queue()
581 * Purpose: Select a proper request queue to serve next
583 * Arguments: q - last request's queue
587 * Notes: The previous command was completely finished, start
588 * a new one if possible.
590 static void scsi_run_queue(struct request_queue *q)
592 struct scsi_device *sdev = q->queuedata;
593 struct Scsi_Host *shost = sdev->host;
594 LIST_HEAD(starved_list);
597 if (scsi_target(sdev)->single_lun)
598 scsi_single_lun_run(sdev);
600 spin_lock_irqsave(shost->host_lock, flags);
601 list_splice_init(&shost->starved_list, &starved_list);
603 while (!list_empty(&starved_list)) {
607 * As long as shost is accepting commands and we have
608 * starved queues, call blk_run_queue. scsi_request_fn
609 * drops the queue_lock and can add us back to the
612 * host_lock protects the starved_list and starved_entry.
613 * scsi_request_fn must get the host_lock before checking
614 * or modifying starved_list or starved_entry.
616 if (scsi_host_is_busy(shost))
619 sdev = list_entry(starved_list.next,
620 struct scsi_device, starved_entry);
621 list_del_init(&sdev->starved_entry);
622 if (scsi_target_is_busy(scsi_target(sdev))) {
623 list_move_tail(&sdev->starved_entry,
624 &shost->starved_list);
628 spin_unlock(shost->host_lock);
630 spin_lock(sdev->request_queue->queue_lock);
631 flagset = test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) &&
632 !test_bit(QUEUE_FLAG_REENTER,
633 &sdev->request_queue->queue_flags);
635 queue_flag_set(QUEUE_FLAG_REENTER, sdev->request_queue);
636 __blk_run_queue(sdev->request_queue);
638 queue_flag_clear(QUEUE_FLAG_REENTER, sdev->request_queue);
639 spin_unlock(sdev->request_queue->queue_lock);
641 spin_lock(shost->host_lock);
643 /* put any unprocessed entries back */
644 list_splice(&starved_list, &shost->starved_list);
645 spin_unlock_irqrestore(shost->host_lock, flags);
651 * Function: scsi_requeue_command()
653 * Purpose: Handle post-processing of completed commands.
655 * Arguments: q - queue to operate on
656 * cmd - command that may need to be requeued.
660 * Notes: After command completion, there may be blocks left
661 * over which weren't finished by the previous command
662 * this can be for a number of reasons - the main one is
663 * I/O errors in the middle of the request, in which case
664 * we need to request the blocks that come after the bad
666 * Notes: Upon return, cmd is a stale pointer.
668 static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
670 struct request *req = cmd->request;
673 spin_lock_irqsave(q->queue_lock, flags);
674 scsi_unprep_request(req);
675 blk_requeue_request(q, req);
676 spin_unlock_irqrestore(q->queue_lock, flags);
681 void scsi_next_command(struct scsi_cmnd *cmd)
683 struct scsi_device *sdev = cmd->device;
684 struct request_queue *q = sdev->request_queue;
686 /* need to hold a reference on the device before we let go of the cmd */
687 get_device(&sdev->sdev_gendev);
689 scsi_put_command(cmd);
692 /* ok to remove device now */
693 put_device(&sdev->sdev_gendev);
696 void scsi_run_host_queues(struct Scsi_Host *shost)
698 struct scsi_device *sdev;
700 shost_for_each_device(sdev, shost)
701 scsi_run_queue(sdev->request_queue);
705 * Function: scsi_end_request()
707 * Purpose: Post-processing of completed commands (usually invoked at end
708 * of upper level post-processing and scsi_io_completion).
710 * Arguments: cmd - command that is complete.
711 * error - 0 if I/O indicates success, < 0 for I/O error.
712 * bytes - number of bytes of completed I/O
713 * requeue - indicates whether we should requeue leftovers.
715 * Lock status: Assumed that lock is not held upon entry.
717 * Returns: cmd if requeue required, NULL otherwise.
719 * Notes: This is called for block device requests in order to
720 * mark some number of sectors as complete.
722 * We are guaranteeing that the request queue will be goosed
723 * at some point during this call.
724 * Notes: If cmd was requeued, upon return it will be a stale pointer.
726 static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
727 int bytes, int requeue)
729 struct request_queue *q = cmd->device->request_queue;
730 struct request *req = cmd->request;
733 * If there are blocks left over at the end, set up the command
734 * to queue the remainder of them.
736 if (blk_end_request(req, error, bytes)) {
737 int leftover = (req->hard_nr_sectors << 9);
739 if (blk_pc_request(req))
740 leftover = req->data_len;
742 /* kill remainder if no retrys */
743 if (error && scsi_noretry_cmd(cmd))
744 blk_end_request(req, error, leftover);
748 * Bleah. Leftovers again. Stick the
749 * leftovers in the front of the
750 * queue, and goose the queue again.
752 scsi_requeue_command(q, cmd);
760 * This will goose the queue request function at the end, so we don't
761 * need to worry about launching another command.
763 scsi_next_command(cmd);
767 static inline unsigned int scsi_sgtable_index(unsigned short nents)
771 BUG_ON(nents > SCSI_MAX_SG_SEGMENTS);
776 index = get_count_order(nents) - 3;
781 static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)
783 struct scsi_host_sg_pool *sgp;
785 sgp = scsi_sg_pools + scsi_sgtable_index(nents);
786 mempool_free(sgl, sgp->pool);
789 static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
791 struct scsi_host_sg_pool *sgp;
793 sgp = scsi_sg_pools + scsi_sgtable_index(nents);
794 return mempool_alloc(sgp->pool, gfp_mask);
797 static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents,
804 ret = __sg_alloc_table(&sdb->table, nents, SCSI_MAX_SG_SEGMENTS,
805 gfp_mask, scsi_sg_alloc);
807 __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS,
813 static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
815 __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
819 * Function: scsi_release_buffers()
821 * Purpose: Completion processing for block device I/O requests.
823 * Arguments: cmd - command that we are bailing.
825 * Lock status: Assumed that no lock is held upon entry.
829 * Notes: In the event that an upper level driver rejects a
830 * command, we must release resources allocated during
831 * the __init_io() function. Primarily this would involve
832 * the scatter-gather table, and potentially any bounce
835 void scsi_release_buffers(struct scsi_cmnd *cmd)
837 if (cmd->sdb.table.nents)
838 scsi_free_sgtable(&cmd->sdb);
840 memset(&cmd->sdb, 0, sizeof(cmd->sdb));
842 if (scsi_bidi_cmnd(cmd)) {
843 struct scsi_data_buffer *bidi_sdb =
844 cmd->request->next_rq->special;
845 scsi_free_sgtable(bidi_sdb);
846 kmem_cache_free(scsi_sdb_cache, bidi_sdb);
847 cmd->request->next_rq->special = NULL;
850 if (scsi_prot_sg_count(cmd))
851 scsi_free_sgtable(cmd->prot_sdb);
853 EXPORT_SYMBOL(scsi_release_buffers);
856 * Bidi commands Must be complete as a whole, both sides at once.
857 * If part of the bytes were written and lld returned
858 * scsi_in()->resid and/or scsi_out()->resid this information will be left
859 * in req->data_len and req->next_rq->data_len. The upper-layer driver can
860 * decide what to do with this information.
862 static void scsi_end_bidi_request(struct scsi_cmnd *cmd)
864 struct request *req = cmd->request;
865 unsigned int dlen = req->data_len;
866 unsigned int next_dlen = req->next_rq->data_len;
868 req->data_len = scsi_out(cmd)->resid;
869 req->next_rq->data_len = scsi_in(cmd)->resid;
871 /* The req and req->next_rq have not been completed */
872 BUG_ON(blk_end_bidi_request(req, 0, dlen, next_dlen));
874 scsi_release_buffers(cmd);
877 * This will goose the queue request function at the end, so we don't
878 * need to worry about launching another command.
880 scsi_next_command(cmd);
884 * Function: scsi_io_completion()
886 * Purpose: Completion processing for block device I/O requests.
888 * Arguments: cmd - command that is finished.
890 * Lock status: Assumed that no lock is held upon entry.
894 * Notes: This function is matched in terms of capabilities to
895 * the function that created the scatter-gather list.
896 * In other words, if there are no bounce buffers
897 * (the normal case for most drivers), we don't need
898 * the logic to deal with cleaning up afterwards.
900 * We must call scsi_end_request(). This will finish off
901 * the specified number of sectors. If we are done, the
902 * command block will be released and the queue function
903 * will be goosed. If we are not done then we have to
904 * figure out what to do next:
906 * a) We can call scsi_requeue_command(). The request
907 * will be unprepared and put back on the queue. Then
908 * a new command will be created for it. This should
909 * be used if we made forward progress, or if we want
910 * to switch from READ(10) to READ(6) for example.
912 * b) We can call scsi_queue_insert(). The request will
913 * be put back on the queue and retried using the same
914 * command as before, possibly after a delay.
916 * c) We can call blk_end_request() with -EIO to fail
917 * the remainder of the request.
919 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
921 int result = cmd->result;
923 struct request_queue *q = cmd->device->request_queue;
924 struct request *req = cmd->request;
926 struct scsi_sense_hdr sshdr;
928 int sense_deferred = 0;
929 enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
930 ACTION_DELAYED_RETRY} action;
931 char *description = NULL;
934 sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
936 sense_deferred = scsi_sense_is_deferred(&sshdr);
939 if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
940 req->errors = result;
942 if (sense_valid && req->sense) {
944 * SG_IO wants current and deferred errors
946 int len = 8 + cmd->sense_buffer[7];
948 if (len > SCSI_SENSE_BUFFERSIZE)
949 len = SCSI_SENSE_BUFFERSIZE;
950 memcpy(req->sense, cmd->sense_buffer, len);
951 req->sense_len = len;
956 if (scsi_bidi_cmnd(cmd)) {
957 /* will also release_buffers */
958 scsi_end_bidi_request(cmd);
961 req->data_len = scsi_get_resid(cmd);
964 BUG_ON(blk_bidi_rq(req)); /* bidi not support for !blk_pc_request yet */
965 scsi_release_buffers(cmd);
968 * Next deal with any sectors which we were able to correctly
971 SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, "
973 req->nr_sectors, good_bytes));
975 /* A number of bytes were successfully read. If there
976 * are leftovers and there is some kind of error
977 * (result != 0), retry the rest.
979 if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
981 this_count = blk_rq_bytes(req);
983 if (host_byte(result) == DID_RESET) {
984 /* Third party bus reset or reset for error recovery
985 * reasons. Just retry the command and see what
988 action = ACTION_RETRY;
989 } else if (sense_valid && !sense_deferred) {
990 switch (sshdr.sense_key) {
992 if (cmd->device->removable) {
993 /* Detected disc change. Set a bit
994 * and quietly refuse further access.
996 cmd->device->changed = 1;
997 description = "Media Changed";
998 action = ACTION_FAIL;
1000 /* Must have been a power glitch, or a
1001 * bus reset. Could not have been a
1002 * media change, so we just retry the
1003 * command and see what happens.
1005 action = ACTION_RETRY;
1008 case ILLEGAL_REQUEST:
1009 /* If we had an ILLEGAL REQUEST returned, then
1010 * we may have performed an unsupported
1011 * command. The only thing this should be
1012 * would be a ten byte read where only a six
1013 * byte read was supported. Also, on a system
1014 * where READ CAPACITY failed, we may have
1015 * read past the end of the disk.
1017 if ((cmd->device->use_10_for_rw &&
1018 sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
1019 (cmd->cmnd[0] == READ_10 ||
1020 cmd->cmnd[0] == WRITE_10)) {
1021 /* This will issue a new 6-byte command. */
1022 cmd->device->use_10_for_rw = 0;
1023 action = ACTION_REPREP;
1025 action = ACTION_FAIL;
1027 case ABORTED_COMMAND:
1028 if (sshdr.asc == 0x10) { /* DIF */
1029 action = ACTION_FAIL;
1030 description = "Data Integrity Failure";
1032 action = ACTION_RETRY;
1035 /* If the device is in the process of becoming
1036 * ready, or has a temporary blockage, retry.
1038 if (sshdr.asc == 0x04) {
1039 switch (sshdr.ascq) {
1040 case 0x01: /* becoming ready */
1041 case 0x04: /* format in progress */
1042 case 0x05: /* rebuild in progress */
1043 case 0x06: /* recalculation in progress */
1044 case 0x07: /* operation in progress */
1045 case 0x08: /* Long write in progress */
1046 case 0x09: /* self test in progress */
1047 action = ACTION_DELAYED_RETRY;
1050 description = "Device not ready";
1051 action = ACTION_FAIL;
1055 description = "Device not ready";
1056 action = ACTION_FAIL;
1059 case VOLUME_OVERFLOW:
1060 /* See SSC3rXX or current. */
1061 action = ACTION_FAIL;
1064 description = "Unhandled sense code";
1065 action = ACTION_FAIL;
1069 description = "Unhandled error code";
1070 action = ACTION_FAIL;
1075 /* Give up and fail the remainder of the request */
1076 if (!(req->cmd_flags & REQ_QUIET)) {
1078 scmd_printk(KERN_INFO, cmd, "%s\n",
1080 scsi_print_result(cmd);
1081 if (driver_byte(result) & DRIVER_SENSE)
1082 scsi_print_sense("", cmd);
1084 blk_end_request(req, -EIO, blk_rq_bytes(req));
1085 scsi_next_command(cmd);
1088 /* Unprep the request and put it back at the head of the queue.
1089 * A new command will be prepared and issued.
1091 scsi_requeue_command(q, cmd);
1094 /* Retry the same command immediately */
1095 __scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, 0);
1097 case ACTION_DELAYED_RETRY:
1098 /* Retry the same command after a delay */
1099 __scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, 0);
1104 static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
1110 * If sg table allocation fails, requeue request later.
1112 if (unlikely(scsi_alloc_sgtable(sdb, req->nr_phys_segments,
1114 return BLKPREP_DEFER;
1120 * Next, walk the list, and fill in the addresses and sizes of
1123 count = blk_rq_map_sg(req->q, req, sdb->table.sgl);
1124 BUG_ON(count > sdb->table.nents);
1125 sdb->table.nents = count;
1126 if (blk_pc_request(req))
1127 sdb->length = req->data_len;
1129 sdb->length = req->nr_sectors << 9;
1134 * Function: scsi_init_io()
1136 * Purpose: SCSI I/O initialize function.
1138 * Arguments: cmd - Command descriptor we wish to initialize
1140 * Returns: 0 on success
1141 * BLKPREP_DEFER if the failure is retryable
1142 * BLKPREP_KILL if the failure is fatal
1144 int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
1146 int error = scsi_init_sgtable(cmd->request, &cmd->sdb, gfp_mask);
1150 if (blk_bidi_rq(cmd->request)) {
1151 struct scsi_data_buffer *bidi_sdb = kmem_cache_zalloc(
1152 scsi_sdb_cache, GFP_ATOMIC);
1154 error = BLKPREP_DEFER;
1158 cmd->request->next_rq->special = bidi_sdb;
1159 error = scsi_init_sgtable(cmd->request->next_rq, bidi_sdb,
1165 if (blk_integrity_rq(cmd->request)) {
1166 struct scsi_data_buffer *prot_sdb = cmd->prot_sdb;
1169 BUG_ON(prot_sdb == NULL);
1170 ivecs = blk_rq_count_integrity_sg(cmd->request);
1172 if (scsi_alloc_sgtable(prot_sdb, ivecs, gfp_mask)) {
1173 error = BLKPREP_DEFER;
1177 count = blk_rq_map_integrity_sg(cmd->request,
1178 prot_sdb->table.sgl);
1179 BUG_ON(unlikely(count > ivecs));
1181 cmd->prot_sdb = prot_sdb;
1182 cmd->prot_sdb->table.nents = count;
1188 scsi_release_buffers(cmd);
1189 if (error == BLKPREP_KILL)
1190 scsi_put_command(cmd);
1191 else /* BLKPREP_DEFER */
1192 scsi_unprep_request(cmd->request);
1196 EXPORT_SYMBOL(scsi_init_io);
1198 static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
1199 struct request *req)
1201 struct scsi_cmnd *cmd;
1203 if (!req->special) {
1204 cmd = scsi_get_command(sdev, GFP_ATOMIC);
1212 /* pull a tag out of the request if we have one */
1213 cmd->tag = req->tag;
1216 cmd->cmnd = req->cmd;
1221 int scsi_setup_blk_pc_cmnd(struct scsi_device *sdev, struct request *req)
1223 struct scsi_cmnd *cmd;
1224 int ret = scsi_prep_state_check(sdev, req);
1226 if (ret != BLKPREP_OK)
1229 cmd = scsi_get_cmd_from_req(sdev, req);
1231 return BLKPREP_DEFER;
1234 * BLOCK_PC requests may transfer data, in which case they must
1235 * a bio attached to them. Or they might contain a SCSI command
1236 * that does not transfer data, in which case they may optionally
1237 * submit a request without an attached bio.
1242 BUG_ON(!req->nr_phys_segments);
1244 ret = scsi_init_io(cmd, GFP_ATOMIC);
1248 BUG_ON(req->data_len);
1251 memset(&cmd->sdb, 0, sizeof(cmd->sdb));
1255 cmd->cmd_len = req->cmd_len;
1257 cmd->sc_data_direction = DMA_NONE;
1258 else if (rq_data_dir(req) == WRITE)
1259 cmd->sc_data_direction = DMA_TO_DEVICE;
1261 cmd->sc_data_direction = DMA_FROM_DEVICE;
1263 cmd->transfersize = req->data_len;
1264 cmd->allowed = req->retries;
1267 EXPORT_SYMBOL(scsi_setup_blk_pc_cmnd);
1270 * Setup a REQ_TYPE_FS command. These are simple read/write request
1271 * from filesystems that still need to be translated to SCSI CDBs from
1274 int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
1276 struct scsi_cmnd *cmd;
1277 int ret = scsi_prep_state_check(sdev, req);
1279 if (ret != BLKPREP_OK)
1282 if (unlikely(sdev->scsi_dh_data && sdev->scsi_dh_data->scsi_dh
1283 && sdev->scsi_dh_data->scsi_dh->prep_fn)) {
1284 ret = sdev->scsi_dh_data->scsi_dh->prep_fn(sdev, req);
1285 if (ret != BLKPREP_OK)
1290 * Filesystem requests must transfer data.
1292 BUG_ON(!req->nr_phys_segments);
1294 cmd = scsi_get_cmd_from_req(sdev, req);
1296 return BLKPREP_DEFER;
1298 memset(cmd->cmnd, 0, BLK_MAX_CDB);
1299 return scsi_init_io(cmd, GFP_ATOMIC);
1301 EXPORT_SYMBOL(scsi_setup_fs_cmnd);
1303 int scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
1305 int ret = BLKPREP_OK;
1308 * If the device is not in running state we will reject some
1311 if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
1312 switch (sdev->sdev_state) {
1315 * If the device is offline we refuse to process any
1316 * commands. The device must be brought online
1317 * before trying any recovery commands.
1319 sdev_printk(KERN_ERR, sdev,
1320 "rejecting I/O to offline device\n");
1325 * If the device is fully deleted, we refuse to
1326 * process any commands as well.
1328 sdev_printk(KERN_ERR, sdev,
1329 "rejecting I/O to dead device\n");
1334 case SDEV_CREATED_BLOCK:
1336 * If the devices is blocked we defer normal commands.
1338 if (!(req->cmd_flags & REQ_PREEMPT))
1339 ret = BLKPREP_DEFER;
1343 * For any other not fully online state we only allow
1344 * special commands. In particular any user initiated
1345 * command is not allowed.
1347 if (!(req->cmd_flags & REQ_PREEMPT))
1354 EXPORT_SYMBOL(scsi_prep_state_check);
1356 int scsi_prep_return(struct request_queue *q, struct request *req, int ret)
1358 struct scsi_device *sdev = q->queuedata;
1362 req->errors = DID_NO_CONNECT << 16;
1363 /* release the command and kill it */
1365 struct scsi_cmnd *cmd = req->special;
1366 scsi_release_buffers(cmd);
1367 scsi_put_command(cmd);
1368 req->special = NULL;
1373 * If we defer, the elv_next_request() returns NULL, but the
1374 * queue must be restarted, so we plug here if no returning
1375 * command will automatically do that.
1377 if (sdev->device_busy == 0)
1381 req->cmd_flags |= REQ_DONTPREP;
1386 EXPORT_SYMBOL(scsi_prep_return);
1388 int scsi_prep_fn(struct request_queue *q, struct request *req)
1390 struct scsi_device *sdev = q->queuedata;
1391 int ret = BLKPREP_KILL;
1393 if (req->cmd_type == REQ_TYPE_BLOCK_PC)
1394 ret = scsi_setup_blk_pc_cmnd(sdev, req);
1395 return scsi_prep_return(q, req, ret);
1399 * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1402 * Called with the queue_lock held.
1404 static inline int scsi_dev_queue_ready(struct request_queue *q,
1405 struct scsi_device *sdev)
1407 if (sdev->device_busy == 0 && sdev->device_blocked) {
1409 * unblock after device_blocked iterates to zero
1411 if (--sdev->device_blocked == 0) {
1413 sdev_printk(KERN_INFO, sdev,
1414 "unblocking device at zero depth\n"));
1420 if (scsi_device_is_busy(sdev))
1428 * scsi_target_queue_ready: checks if there we can send commands to target
1429 * @sdev: scsi device on starget to check.
1431 * Called with the host lock held.
1433 static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
1434 struct scsi_device *sdev)
1436 struct scsi_target *starget = scsi_target(sdev);
1438 if (starget->single_lun) {
1439 if (starget->starget_sdev_user &&
1440 starget->starget_sdev_user != sdev)
1442 starget->starget_sdev_user = sdev;
1445 if (starget->target_busy == 0 && starget->target_blocked) {
1447 * unblock after target_blocked iterates to zero
1449 if (--starget->target_blocked == 0) {
1450 SCSI_LOG_MLQUEUE(3, starget_printk(KERN_INFO, starget,
1451 "unblocking target at zero depth\n"));
1453 blk_plug_device(sdev->request_queue);
1458 if (scsi_target_is_busy(starget)) {
1459 if (list_empty(&sdev->starved_entry)) {
1460 list_add_tail(&sdev->starved_entry,
1461 &shost->starved_list);
1466 /* We're OK to process the command, so we can't be starved */
1467 if (!list_empty(&sdev->starved_entry))
1468 list_del_init(&sdev->starved_entry);
1473 * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1474 * return 0. We must end up running the queue again whenever 0 is
1475 * returned, else IO can hang.
1477 * Called with host_lock held.
1479 static inline int scsi_host_queue_ready(struct request_queue *q,
1480 struct Scsi_Host *shost,
1481 struct scsi_device *sdev)
1483 if (scsi_host_in_recovery(shost))
1485 if (shost->host_busy == 0 && shost->host_blocked) {
1487 * unblock after host_blocked iterates to zero
1489 if (--shost->host_blocked == 0) {
1491 printk("scsi%d unblocking host at zero depth\n",
1497 if (scsi_host_is_busy(shost)) {
1498 if (list_empty(&sdev->starved_entry))
1499 list_add_tail(&sdev->starved_entry, &shost->starved_list);
1503 /* We're OK to process the command, so we can't be starved */
1504 if (!list_empty(&sdev->starved_entry))
1505 list_del_init(&sdev->starved_entry);
1511 * Busy state exporting function for request stacking drivers.
1513 * For efficiency, no lock is taken to check the busy state of
1514 * shost/starget/sdev, since the returned value is not guaranteed and
1515 * may be changed after request stacking drivers call the function,
1516 * regardless of taking lock or not.
1518 * When scsi can't dispatch I/Os anymore and needs to kill I/Os
1519 * (e.g. !sdev), scsi needs to return 'not busy'.
1520 * Otherwise, request stacking drivers may hold requests forever.
1522 static int scsi_lld_busy(struct request_queue *q)
1524 struct scsi_device *sdev = q->queuedata;
1525 struct Scsi_Host *shost;
1526 struct scsi_target *starget;
1532 starget = scsi_target(sdev);
1534 if (scsi_host_in_recovery(shost) || scsi_host_is_busy(shost) ||
1535 scsi_target_is_busy(starget) || scsi_device_is_busy(sdev))
1542 * Kill a request for a dead device
1544 static void scsi_kill_request(struct request *req, struct request_queue *q)
1546 struct scsi_cmnd *cmd = req->special;
1547 struct scsi_device *sdev = cmd->device;
1548 struct scsi_target *starget = scsi_target(sdev);
1549 struct Scsi_Host *shost = sdev->host;
1551 blkdev_dequeue_request(req);
1553 if (unlikely(cmd == NULL)) {
1554 printk(KERN_CRIT "impossible request in %s.\n",
1559 scsi_init_cmd_errh(cmd);
1560 cmd->result = DID_NO_CONNECT << 16;
1561 atomic_inc(&cmd->device->iorequest_cnt);
1564 * SCSI request completion path will do scsi_device_unbusy(),
1565 * bump busy counts. To bump the counters, we need to dance
1566 * with the locks as normal issue path does.
1568 sdev->device_busy++;
1569 spin_unlock(sdev->request_queue->queue_lock);
1570 spin_lock(shost->host_lock);
1572 starget->target_busy++;
1573 spin_unlock(shost->host_lock);
1574 spin_lock(sdev->request_queue->queue_lock);
1576 blk_complete_request(req);
1579 static void scsi_softirq_done(struct request *rq)
1581 struct scsi_cmnd *cmd = rq->special;
1582 unsigned long wait_for = (cmd->allowed + 1) * rq->timeout;
1585 INIT_LIST_HEAD(&cmd->eh_entry);
1588 * Set the serial numbers back to zero
1590 cmd->serial_number = 0;
1592 atomic_inc(&cmd->device->iodone_cnt);
1594 atomic_inc(&cmd->device->ioerr_cnt);
1596 disposition = scsi_decide_disposition(cmd);
1597 if (disposition != SUCCESS &&
1598 time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
1599 sdev_printk(KERN_ERR, cmd->device,
1600 "timing out command, waited %lus\n",
1602 disposition = SUCCESS;
1605 scsi_log_completion(cmd, disposition);
1607 switch (disposition) {
1609 scsi_finish_command(cmd);
1612 scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY);
1614 case ADD_TO_MLQUEUE:
1615 scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
1618 if (!scsi_eh_scmd_add(cmd, 0))
1619 scsi_finish_command(cmd);
1624 * Function: scsi_request_fn()
1626 * Purpose: Main strategy routine for SCSI.
1628 * Arguments: q - Pointer to actual queue.
1632 * Lock status: IO request lock assumed to be held when called.
1634 static void scsi_request_fn(struct request_queue *q)
1636 struct scsi_device *sdev = q->queuedata;
1637 struct Scsi_Host *shost;
1638 struct scsi_cmnd *cmd;
1639 struct request *req;
1642 printk("scsi: killing requests for dead queue\n");
1643 while ((req = elv_next_request(q)) != NULL)
1644 scsi_kill_request(req, q);
1648 if(!get_device(&sdev->sdev_gendev))
1649 /* We must be tearing the block queue down already */
1653 * To start with, we keep looping until the queue is empty, or until
1654 * the host is no longer able to accept any more requests.
1657 while (!blk_queue_plugged(q)) {
1660 * get next queueable request. We do this early to make sure
1661 * that the request is fully prepared even if we cannot
1664 req = elv_next_request(q);
1665 if (!req || !scsi_dev_queue_ready(q, sdev))
1668 if (unlikely(!scsi_device_online(sdev))) {
1669 sdev_printk(KERN_ERR, sdev,
1670 "rejecting I/O to offline device\n");
1671 scsi_kill_request(req, q);
1677 * Remove the request from the request list.
1679 if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1680 blkdev_dequeue_request(req);
1681 sdev->device_busy++;
1683 spin_unlock(q->queue_lock);
1685 if (unlikely(cmd == NULL)) {
1686 printk(KERN_CRIT "impossible request in %s.\n"
1687 "please mail a stack trace to "
1688 "linux-scsi@vger.kernel.org\n",
1690 blk_dump_rq_flags(req, "foo");
1693 spin_lock(shost->host_lock);
1696 * We hit this when the driver is using a host wide
1697 * tag map. For device level tag maps the queue_depth check
1698 * in the device ready fn would prevent us from trying
1699 * to allocate a tag. Since the map is a shared host resource
1700 * we add the dev to the starved list so it eventually gets
1701 * a run when a tag is freed.
1703 if (blk_queue_tagged(q) && !blk_rq_tagged(req)) {
1704 if (list_empty(&sdev->starved_entry))
1705 list_add_tail(&sdev->starved_entry,
1706 &shost->starved_list);
1710 if (!scsi_target_queue_ready(shost, sdev))
1713 if (!scsi_host_queue_ready(q, shost, sdev))
1716 scsi_target(sdev)->target_busy++;
1720 * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1721 * take the lock again.
1723 spin_unlock_irq(shost->host_lock);
1726 * Finally, initialize any error handling parameters, and set up
1727 * the timers for timeouts.
1729 scsi_init_cmd_errh(cmd);
1732 * Dispatch the command to the low-level driver.
1734 rtn = scsi_dispatch_cmd(cmd);
1735 spin_lock_irq(q->queue_lock);
1737 /* we're refusing the command; because of
1738 * the way locks get dropped, we need to
1739 * check here if plugging is required */
1740 if(sdev->device_busy == 0)
1750 spin_unlock_irq(shost->host_lock);
1753 * lock q, handle tag, requeue req, and decrement device_busy. We
1754 * must return with queue_lock held.
1756 * Decrementing device_busy without checking it is OK, as all such
1757 * cases (host limits or settings) should run the queue at some
1760 spin_lock_irq(q->queue_lock);
1761 blk_requeue_request(q, req);
1762 sdev->device_busy--;
1763 if(sdev->device_busy == 0)
1766 /* must be careful here...if we trigger the ->remove() function
1767 * we cannot be holding the q lock */
1768 spin_unlock_irq(q->queue_lock);
1769 put_device(&sdev->sdev_gendev);
1770 spin_lock_irq(q->queue_lock);
1773 u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1775 struct device *host_dev;
1776 u64 bounce_limit = 0xffffffff;
1778 if (shost->unchecked_isa_dma)
1779 return BLK_BOUNCE_ISA;
1781 * Platforms with virtual-DMA translation
1782 * hardware have no practical limit.
1784 if (!PCI_DMA_BUS_IS_PHYS)
1785 return BLK_BOUNCE_ANY;
1787 host_dev = scsi_get_device(shost);
1788 if (host_dev && host_dev->dma_mask)
1789 bounce_limit = *host_dev->dma_mask;
1791 return bounce_limit;
1793 EXPORT_SYMBOL(scsi_calculate_bounce_limit);
1795 struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
1796 request_fn_proc *request_fn)
1798 struct request_queue *q;
1799 struct device *dev = shost->shost_gendev.parent;
1801 q = blk_init_queue(request_fn, NULL);
1806 * this limit is imposed by hardware restrictions
1808 blk_queue_max_hw_segments(q, shost->sg_tablesize);
1809 blk_queue_max_phys_segments(q, SCSI_MAX_SG_CHAIN_SEGMENTS);
1811 blk_queue_max_sectors(q, shost->max_sectors);
1812 blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1813 blk_queue_segment_boundary(q, shost->dma_boundary);
1814 dma_set_seg_boundary(dev, shost->dma_boundary);
1816 blk_queue_max_segment_size(q, dma_get_max_seg_size(dev));
1818 /* New queue, no concurrency on queue_flags */
1819 if (!shost->use_clustering)
1820 queue_flag_clear_unlocked(QUEUE_FLAG_CLUSTER, q);
1823 * set a reasonable default alignment on word boundaries: the
1824 * host and device may alter it using
1825 * blk_queue_update_dma_alignment() later.
1827 blk_queue_dma_alignment(q, 0x03);
1831 EXPORT_SYMBOL(__scsi_alloc_queue);
1833 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1835 struct request_queue *q;
1837 q = __scsi_alloc_queue(sdev->host, scsi_request_fn);
1841 blk_queue_prep_rq(q, scsi_prep_fn);
1842 blk_queue_softirq_done(q, scsi_softirq_done);
1843 blk_queue_rq_timed_out(q, scsi_times_out);
1844 blk_queue_lld_busy(q, scsi_lld_busy);
1848 void scsi_free_queue(struct request_queue *q)
1850 blk_cleanup_queue(q);
1854 * Function: scsi_block_requests()
1856 * Purpose: Utility function used by low-level drivers to prevent further
1857 * commands from being queued to the device.
1859 * Arguments: shost - Host in question
1863 * Lock status: No locks are assumed held.
1865 * Notes: There is no timer nor any other means by which the requests
1866 * get unblocked other than the low-level driver calling
1867 * scsi_unblock_requests().
1869 void scsi_block_requests(struct Scsi_Host *shost)
1871 shost->host_self_blocked = 1;
1873 EXPORT_SYMBOL(scsi_block_requests);
1876 * Function: scsi_unblock_requests()
1878 * Purpose: Utility function used by low-level drivers to allow further
1879 * commands from being queued to the device.
1881 * Arguments: shost - Host in question
1885 * Lock status: No locks are assumed held.
1887 * Notes: There is no timer nor any other means by which the requests
1888 * get unblocked other than the low-level driver calling
1889 * scsi_unblock_requests().
1891 * This is done as an API function so that changes to the
1892 * internals of the scsi mid-layer won't require wholesale
1893 * changes to drivers that use this feature.
1895 void scsi_unblock_requests(struct Scsi_Host *shost)
1897 shost->host_self_blocked = 0;
1898 scsi_run_host_queues(shost);
1900 EXPORT_SYMBOL(scsi_unblock_requests);
1902 int __init scsi_init_queue(void)
1906 scsi_io_context_cache = kmem_cache_create("scsi_io_context",
1907 sizeof(struct scsi_io_context),
1909 if (!scsi_io_context_cache) {
1910 printk(KERN_ERR "SCSI: can't init scsi io context cache\n");
1914 scsi_sdb_cache = kmem_cache_create("scsi_data_buffer",
1915 sizeof(struct scsi_data_buffer),
1917 if (!scsi_sdb_cache) {
1918 printk(KERN_ERR "SCSI: can't init scsi sdb cache\n");
1919 goto cleanup_io_context;
1922 for (i = 0; i < SG_MEMPOOL_NR; i++) {
1923 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1924 int size = sgp->size * sizeof(struct scatterlist);
1926 sgp->slab = kmem_cache_create(sgp->name, size, 0,
1927 SLAB_HWCACHE_ALIGN, NULL);
1929 printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1934 sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
1937 printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1946 for (i = 0; i < SG_MEMPOOL_NR; i++) {
1947 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1949 mempool_destroy(sgp->pool);
1951 kmem_cache_destroy(sgp->slab);
1953 kmem_cache_destroy(scsi_sdb_cache);
1955 kmem_cache_destroy(scsi_io_context_cache);
1960 void scsi_exit_queue(void)
1964 kmem_cache_destroy(scsi_io_context_cache);
1965 kmem_cache_destroy(scsi_sdb_cache);
1967 for (i = 0; i < SG_MEMPOOL_NR; i++) {
1968 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1969 mempool_destroy(sgp->pool);
1970 kmem_cache_destroy(sgp->slab);
1975 * scsi_mode_select - issue a mode select
1976 * @sdev: SCSI device to be queried
1977 * @pf: Page format bit (1 == standard, 0 == vendor specific)
1978 * @sp: Save page bit (0 == don't save, 1 == save)
1979 * @modepage: mode page being requested
1980 * @buffer: request buffer (may not be smaller than eight bytes)
1981 * @len: length of request buffer.
1982 * @timeout: command timeout
1983 * @retries: number of retries before failing
1984 * @data: returns a structure abstracting the mode header data
1985 * @sshdr: place to put sense data (or NULL if no sense to be collected).
1986 * must be SCSI_SENSE_BUFFERSIZE big.
1988 * Returns zero if successful; negative error number or scsi
1993 scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
1994 unsigned char *buffer, int len, int timeout, int retries,
1995 struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1997 unsigned char cmd[10];
1998 unsigned char *real_buffer;
2001 memset(cmd, 0, sizeof(cmd));
2002 cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
2004 if (sdev->use_10_for_ms) {
2007 real_buffer = kmalloc(8 + len, GFP_KERNEL);
2010 memcpy(real_buffer + 8, buffer, len);
2014 real_buffer[2] = data->medium_type;
2015 real_buffer[3] = data->device_specific;
2016 real_buffer[4] = data->longlba ? 0x01 : 0;
2018 real_buffer[6] = data->block_descriptor_length >> 8;
2019 real_buffer[7] = data->block_descriptor_length;
2021 cmd[0] = MODE_SELECT_10;
2025 if (len > 255 || data->block_descriptor_length > 255 ||
2029 real_buffer = kmalloc(4 + len, GFP_KERNEL);
2032 memcpy(real_buffer + 4, buffer, len);
2035 real_buffer[1] = data->medium_type;
2036 real_buffer[2] = data->device_specific;
2037 real_buffer[3] = data->block_descriptor_length;
2040 cmd[0] = MODE_SELECT;
2044 ret = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, real_buffer, len,
2045 sshdr, timeout, retries, NULL);
2049 EXPORT_SYMBOL_GPL(scsi_mode_select);
2052 * scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
2053 * @sdev: SCSI device to be queried
2054 * @dbd: set if mode sense will allow block descriptors to be returned
2055 * @modepage: mode page being requested
2056 * @buffer: request buffer (may not be smaller than eight bytes)
2057 * @len: length of request buffer.
2058 * @timeout: command timeout
2059 * @retries: number of retries before failing
2060 * @data: returns a structure abstracting the mode header data
2061 * @sshdr: place to put sense data (or NULL if no sense to be collected).
2062 * must be SCSI_SENSE_BUFFERSIZE big.
2064 * Returns zero if unsuccessful, or the header offset (either 4
2065 * or 8 depending on whether a six or ten byte command was
2066 * issued) if successful.
2069 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
2070 unsigned char *buffer, int len, int timeout, int retries,
2071 struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
2073 unsigned char cmd[12];
2077 struct scsi_sense_hdr my_sshdr;
2079 memset(data, 0, sizeof(*data));
2080 memset(&cmd[0], 0, 12);
2081 cmd[1] = dbd & 0x18; /* allows DBD and LLBA bits */
2084 /* caller might not be interested in sense, but we need it */
2089 use_10_for_ms = sdev->use_10_for_ms;
2091 if (use_10_for_ms) {
2095 cmd[0] = MODE_SENSE_10;
2102 cmd[0] = MODE_SENSE;
2107 memset(buffer, 0, len);
2109 result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
2110 sshdr, timeout, retries, NULL);
2112 /* This code looks awful: what it's doing is making sure an
2113 * ILLEGAL REQUEST sense return identifies the actual command
2114 * byte as the problem. MODE_SENSE commands can return
2115 * ILLEGAL REQUEST if the code page isn't supported */
2117 if (use_10_for_ms && !scsi_status_is_good(result) &&
2118 (driver_byte(result) & DRIVER_SENSE)) {
2119 if (scsi_sense_valid(sshdr)) {
2120 if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
2121 (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
2123 * Invalid command operation code
2125 sdev->use_10_for_ms = 0;
2131 if(scsi_status_is_good(result)) {
2132 if (unlikely(buffer[0] == 0x86 && buffer[1] == 0x0b &&
2133 (modepage == 6 || modepage == 8))) {
2134 /* Initio breakage? */
2137 data->medium_type = 0;
2138 data->device_specific = 0;
2140 data->block_descriptor_length = 0;
2141 } else if(use_10_for_ms) {
2142 data->length = buffer[0]*256 + buffer[1] + 2;
2143 data->medium_type = buffer[2];
2144 data->device_specific = buffer[3];
2145 data->longlba = buffer[4] & 0x01;
2146 data->block_descriptor_length = buffer[6]*256
2149 data->length = buffer[0] + 1;
2150 data->medium_type = buffer[1];
2151 data->device_specific = buffer[2];
2152 data->block_descriptor_length = buffer[3];
2154 data->header_length = header_length;
2159 EXPORT_SYMBOL(scsi_mode_sense);
2162 * scsi_test_unit_ready - test if unit is ready
2163 * @sdev: scsi device to change the state of.
2164 * @timeout: command timeout
2165 * @retries: number of retries before failing
2166 * @sshdr_external: Optional pointer to struct scsi_sense_hdr for
2167 * returning sense. Make sure that this is cleared before passing
2170 * Returns zero if unsuccessful or an error if TUR failed. For
2171 * removable media, a return of NOT_READY or UNIT_ATTENTION is
2172 * translated to success, with the ->changed flag updated.
2175 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries,
2176 struct scsi_sense_hdr *sshdr_external)
2179 TEST_UNIT_READY, 0, 0, 0, 0, 0,
2181 struct scsi_sense_hdr *sshdr;
2184 if (!sshdr_external)
2185 sshdr = kzalloc(sizeof(*sshdr), GFP_KERNEL);
2187 sshdr = sshdr_external;
2189 /* try to eat the UNIT_ATTENTION if there are enough retries */
2191 result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
2192 timeout, retries, NULL);
2193 if (sdev->removable && scsi_sense_valid(sshdr) &&
2194 sshdr->sense_key == UNIT_ATTENTION)
2196 } while (scsi_sense_valid(sshdr) &&
2197 sshdr->sense_key == UNIT_ATTENTION && --retries);
2200 /* could not allocate sense buffer, so can't process it */
2203 if (sdev->removable && scsi_sense_valid(sshdr) &&
2204 (sshdr->sense_key == UNIT_ATTENTION ||
2205 sshdr->sense_key == NOT_READY)) {
2209 if (!sshdr_external)
2213 EXPORT_SYMBOL(scsi_test_unit_ready);
2216 * scsi_device_set_state - Take the given device through the device state model.
2217 * @sdev: scsi device to change the state of.
2218 * @state: state to change to.
2220 * Returns zero if unsuccessful or an error if the requested
2221 * transition is illegal.
2224 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
2226 enum scsi_device_state oldstate = sdev->sdev_state;
2228 if (state == oldstate)
2234 case SDEV_CREATED_BLOCK:
2278 case SDEV_CREATED_BLOCK:
2285 case SDEV_CREATED_BLOCK:
2320 sdev->sdev_state = state;
2324 SCSI_LOG_ERROR_RECOVERY(1,
2325 sdev_printk(KERN_ERR, sdev,
2326 "Illegal state transition %s->%s\n",
2327 scsi_device_state_name(oldstate),
2328 scsi_device_state_name(state))
2332 EXPORT_SYMBOL(scsi_device_set_state);
2335 * sdev_evt_emit - emit a single SCSI device uevent
2336 * @sdev: associated SCSI device
2337 * @evt: event to emit
2339 * Send a single uevent (scsi_event) to the associated scsi_device.
2341 static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
2346 switch (evt->evt_type) {
2347 case SDEV_EVT_MEDIA_CHANGE:
2348 envp[idx++] = "SDEV_MEDIA_CHANGE=1";
2358 kobject_uevent_env(&sdev->sdev_gendev.kobj, KOBJ_CHANGE, envp);
2362 * sdev_evt_thread - send a uevent for each scsi event
2363 * @work: work struct for scsi_device
2365 * Dispatch queued events to their associated scsi_device kobjects
2368 void scsi_evt_thread(struct work_struct *work)
2370 struct scsi_device *sdev;
2371 LIST_HEAD(event_list);
2373 sdev = container_of(work, struct scsi_device, event_work);
2376 struct scsi_event *evt;
2377 struct list_head *this, *tmp;
2378 unsigned long flags;
2380 spin_lock_irqsave(&sdev->list_lock, flags);
2381 list_splice_init(&sdev->event_list, &event_list);
2382 spin_unlock_irqrestore(&sdev->list_lock, flags);
2384 if (list_empty(&event_list))
2387 list_for_each_safe(this, tmp, &event_list) {
2388 evt = list_entry(this, struct scsi_event, node);
2389 list_del(&evt->node);
2390 scsi_evt_emit(sdev, evt);
2397 * sdev_evt_send - send asserted event to uevent thread
2398 * @sdev: scsi_device event occurred on
2399 * @evt: event to send
2401 * Assert scsi device event asynchronously.
2403 void sdev_evt_send(struct scsi_device *sdev, struct scsi_event *evt)
2405 unsigned long flags;
2408 /* FIXME: currently this check eliminates all media change events
2409 * for polled devices. Need to update to discriminate between AN
2410 * and polled events */
2411 if (!test_bit(evt->evt_type, sdev->supported_events)) {
2417 spin_lock_irqsave(&sdev->list_lock, flags);
2418 list_add_tail(&evt->node, &sdev->event_list);
2419 schedule_work(&sdev->event_work);
2420 spin_unlock_irqrestore(&sdev->list_lock, flags);
2422 EXPORT_SYMBOL_GPL(sdev_evt_send);
2425 * sdev_evt_alloc - allocate a new scsi event
2426 * @evt_type: type of event to allocate
2427 * @gfpflags: GFP flags for allocation
2429 * Allocates and returns a new scsi_event.
2431 struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
2434 struct scsi_event *evt = kzalloc(sizeof(struct scsi_event), gfpflags);
2438 evt->evt_type = evt_type;
2439 INIT_LIST_HEAD(&evt->node);
2441 /* evt_type-specific initialization, if any */
2443 case SDEV_EVT_MEDIA_CHANGE:
2451 EXPORT_SYMBOL_GPL(sdev_evt_alloc);
2454 * sdev_evt_send_simple - send asserted event to uevent thread
2455 * @sdev: scsi_device event occurred on
2456 * @evt_type: type of event to send
2457 * @gfpflags: GFP flags for allocation
2459 * Assert scsi device event asynchronously, given an event type.
2461 void sdev_evt_send_simple(struct scsi_device *sdev,
2462 enum scsi_device_event evt_type, gfp_t gfpflags)
2464 struct scsi_event *evt = sdev_evt_alloc(evt_type, gfpflags);
2466 sdev_printk(KERN_ERR, sdev, "event %d eaten due to OOM\n",
2471 sdev_evt_send(sdev, evt);
2473 EXPORT_SYMBOL_GPL(sdev_evt_send_simple);
2476 * scsi_device_quiesce - Block user issued commands.
2477 * @sdev: scsi device to quiesce.
2479 * This works by trying to transition to the SDEV_QUIESCE state
2480 * (which must be a legal transition). When the device is in this
2481 * state, only special requests will be accepted, all others will
2482 * be deferred. Since special requests may also be requeued requests,
2483 * a successful return doesn't guarantee the device will be
2484 * totally quiescent.
2486 * Must be called with user context, may sleep.
2488 * Returns zero if unsuccessful or an error if not.
2491 scsi_device_quiesce(struct scsi_device *sdev)
2493 int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
2497 scsi_run_queue(sdev->request_queue);
2498 while (sdev->device_busy) {
2499 msleep_interruptible(200);
2500 scsi_run_queue(sdev->request_queue);
2504 EXPORT_SYMBOL(scsi_device_quiesce);
2507 * scsi_device_resume - Restart user issued commands to a quiesced device.
2508 * @sdev: scsi device to resume.
2510 * Moves the device from quiesced back to running and restarts the
2513 * Must be called with user context, may sleep.
2516 scsi_device_resume(struct scsi_device *sdev)
2518 if(scsi_device_set_state(sdev, SDEV_RUNNING))
2520 scsi_run_queue(sdev->request_queue);
2522 EXPORT_SYMBOL(scsi_device_resume);
2525 device_quiesce_fn(struct scsi_device *sdev, void *data)
2527 scsi_device_quiesce(sdev);
2531 scsi_target_quiesce(struct scsi_target *starget)
2533 starget_for_each_device(starget, NULL, device_quiesce_fn);
2535 EXPORT_SYMBOL(scsi_target_quiesce);
2538 device_resume_fn(struct scsi_device *sdev, void *data)
2540 scsi_device_resume(sdev);
2544 scsi_target_resume(struct scsi_target *starget)
2546 starget_for_each_device(starget, NULL, device_resume_fn);
2548 EXPORT_SYMBOL(scsi_target_resume);
2551 * scsi_internal_device_block - internal function to put a device temporarily into the SDEV_BLOCK state
2552 * @sdev: device to block
2554 * Block request made by scsi lld's to temporarily stop all
2555 * scsi commands on the specified device. Called from interrupt
2556 * or normal process context.
2558 * Returns zero if successful or error if not
2561 * This routine transitions the device to the SDEV_BLOCK state
2562 * (which must be a legal transition). When the device is in this
2563 * state, all commands are deferred until the scsi lld reenables
2564 * the device with scsi_device_unblock or device_block_tmo fires.
2565 * This routine assumes the host_lock is held on entry.
2568 scsi_internal_device_block(struct scsi_device *sdev)
2570 struct request_queue *q = sdev->request_queue;
2571 unsigned long flags;
2574 err = scsi_device_set_state(sdev, SDEV_BLOCK);
2576 err = scsi_device_set_state(sdev, SDEV_CREATED_BLOCK);
2583 * The device has transitioned to SDEV_BLOCK. Stop the
2584 * block layer from calling the midlayer with this device's
2587 spin_lock_irqsave(q->queue_lock, flags);
2589 spin_unlock_irqrestore(q->queue_lock, flags);
2593 EXPORT_SYMBOL_GPL(scsi_internal_device_block);
2596 * scsi_internal_device_unblock - resume a device after a block request
2597 * @sdev: device to resume
2599 * Called by scsi lld's or the midlayer to restart the device queue
2600 * for the previously suspended scsi device. Called from interrupt or
2601 * normal process context.
2603 * Returns zero if successful or error if not.
2606 * This routine transitions the device to the SDEV_RUNNING state
2607 * (which must be a legal transition) allowing the midlayer to
2608 * goose the queue for this device. This routine assumes the
2609 * host_lock is held upon entry.
2612 scsi_internal_device_unblock(struct scsi_device *sdev)
2614 struct request_queue *q = sdev->request_queue;
2616 unsigned long flags;
2619 * Try to transition the scsi device to SDEV_RUNNING
2620 * and goose the device queue if successful.
2622 err = scsi_device_set_state(sdev, SDEV_RUNNING);
2624 err = scsi_device_set_state(sdev, SDEV_CREATED);
2630 spin_lock_irqsave(q->queue_lock, flags);
2632 spin_unlock_irqrestore(q->queue_lock, flags);
2636 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
2639 device_block(struct scsi_device *sdev, void *data)
2641 scsi_internal_device_block(sdev);
2645 target_block(struct device *dev, void *data)
2647 if (scsi_is_target_device(dev))
2648 starget_for_each_device(to_scsi_target(dev), NULL,
2654 scsi_target_block(struct device *dev)
2656 if (scsi_is_target_device(dev))
2657 starget_for_each_device(to_scsi_target(dev), NULL,
2660 device_for_each_child(dev, NULL, target_block);
2662 EXPORT_SYMBOL_GPL(scsi_target_block);
2665 device_unblock(struct scsi_device *sdev, void *data)
2667 scsi_internal_device_unblock(sdev);
2671 target_unblock(struct device *dev, void *data)
2673 if (scsi_is_target_device(dev))
2674 starget_for_each_device(to_scsi_target(dev), NULL,
2680 scsi_target_unblock(struct device *dev)
2682 if (scsi_is_target_device(dev))
2683 starget_for_each_device(to_scsi_target(dev), NULL,
2686 device_for_each_child(dev, NULL, target_unblock);
2688 EXPORT_SYMBOL_GPL(scsi_target_unblock);
2691 * scsi_kmap_atomic_sg - find and atomically map an sg-elemnt
2692 * @sgl: scatter-gather list
2693 * @sg_count: number of segments in sg
2694 * @offset: offset in bytes into sg, on return offset into the mapped area
2695 * @len: bytes to map, on return number of bytes mapped
2697 * Returns virtual address of the start of the mapped page
2699 void *scsi_kmap_atomic_sg(struct scatterlist *sgl, int sg_count,
2700 size_t *offset, size_t *len)
2703 size_t sg_len = 0, len_complete = 0;
2704 struct scatterlist *sg;
2707 WARN_ON(!irqs_disabled());
2709 for_each_sg(sgl, sg, sg_count, i) {
2710 len_complete = sg_len; /* Complete sg-entries */
2711 sg_len += sg->length;
2712 if (sg_len > *offset)
2716 if (unlikely(i == sg_count)) {
2717 printk(KERN_ERR "%s: Bytes in sg: %zu, requested offset %zu, "
2719 __func__, sg_len, *offset, sg_count);
2724 /* Offset starting from the beginning of first page in this sg-entry */
2725 *offset = *offset - len_complete + sg->offset;
2727 /* Assumption: contiguous pages can be accessed as "page + i" */
2728 page = nth_page(sg_page(sg), (*offset >> PAGE_SHIFT));
2729 *offset &= ~PAGE_MASK;
2731 /* Bytes in this sg-entry from *offset to the end of the page */
2732 sg_len = PAGE_SIZE - *offset;
2736 return kmap_atomic(page, KM_BIO_SRC_IRQ);
2738 EXPORT_SYMBOL(scsi_kmap_atomic_sg);
2741 * scsi_kunmap_atomic_sg - atomically unmap a virtual address, previously mapped with scsi_kmap_atomic_sg
2742 * @virt: virtual address to be unmapped
2744 void scsi_kunmap_atomic_sg(void *virt)
2746 kunmap_atomic(virt, KM_BIO_SRC_IRQ);
2748 EXPORT_SYMBOL(scsi_kunmap_atomic_sg);