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/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>
20 #include <scsi/scsi.h>
21 #include <scsi/scsi_dbg.h>
22 #include <scsi/scsi_device.h>
23 #include <scsi/scsi_driver.h>
24 #include <scsi/scsi_eh.h>
25 #include <scsi/scsi_host.h>
26 #include <scsi/scsi_request.h>
28 #include "scsi_priv.h"
29 #include "scsi_logging.h"
32 #define SG_MEMPOOL_NR (sizeof(scsi_sg_pools)/sizeof(struct scsi_host_sg_pool))
33 #define SG_MEMPOOL_SIZE 32
35 struct scsi_host_sg_pool {
42 #if (SCSI_MAX_PHYS_SEGMENTS < 32)
43 #error SCSI_MAX_PHYS_SEGMENTS is too small
46 #define SP(x) { x, "sgpool-" #x }
47 struct scsi_host_sg_pool scsi_sg_pools[] = {
51 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
53 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
55 #if (SCSI_MAX_PHYS_SEGMENTS > 128)
57 #if (SCSI_MAX_PHYS_SEGMENTS > 256)
58 #error SCSI_MAX_PHYS_SEGMENTS is too large
68 * Function: scsi_insert_special_req()
70 * Purpose: Insert pre-formed request into request queue.
72 * Arguments: sreq - request that is ready to be queued.
73 * at_head - boolean. True if we should insert at head
74 * of queue, false if we should insert at tail.
76 * Lock status: Assumed that lock is not held upon entry.
80 * Notes: This function is called from character device and from
81 * ioctl types of functions where the caller knows exactly
82 * what SCSI command needs to be issued. The idea is that
83 * we merely inject the command into the queue (at the head
84 * for now), and then call the queue request function to actually
87 int scsi_insert_special_req(struct scsi_request *sreq, int at_head)
90 * Because users of this function are apt to reuse requests with no
91 * modification, we have to sanitise the request flags here
93 sreq->sr_request->flags &= ~REQ_DONTPREP;
94 blk_insert_request(sreq->sr_device->request_queue, sreq->sr_request,
100 * Function: scsi_queue_insert()
102 * Purpose: Insert a command in the midlevel queue.
104 * Arguments: cmd - command that we are adding to queue.
105 * reason - why we are inserting command to queue.
107 * Lock status: Assumed that lock is not held upon entry.
111 * Notes: We do this for one of two cases. Either the host is busy
112 * and it cannot accept any more commands for the time being,
113 * or the device returned QUEUE_FULL and can accept no more
115 * Notes: This could be called either from an interrupt context or a
116 * normal process context.
118 int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
120 struct Scsi_Host *host = cmd->device->host;
121 struct scsi_device *device = cmd->device;
124 printk("Inserting command %p into mlqueue\n", cmd));
127 * We are inserting the command into the ml queue. First, we
128 * cancel the timer, so it doesn't time out.
130 scsi_delete_timer(cmd);
133 * Next, set the appropriate busy bit for the device/host.
135 * If the host/device isn't busy, assume that something actually
136 * completed, and that we should be able to queue a command now.
138 * Note that the prior mid-layer assumption that any host could
139 * always queue at least one command is now broken. The mid-layer
140 * will implement a user specifiable stall (see
141 * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
142 * if a command is requeued with no other commands outstanding
143 * either for the device or for the host.
145 if (reason == SCSI_MLQUEUE_HOST_BUSY)
146 host->host_blocked = host->max_host_blocked;
147 else if (reason == SCSI_MLQUEUE_DEVICE_BUSY)
148 device->device_blocked = device->max_device_blocked;
151 * Register the fact that we own the thing for now.
153 cmd->state = SCSI_STATE_MLQUEUE;
154 cmd->owner = SCSI_OWNER_MIDLEVEL;
157 * Decrement the counters, since these commands are no longer
158 * active on the host/device.
160 scsi_device_unbusy(device);
163 * Insert this command at the head of the queue for it's device.
164 * It will go before all other commands that are already in the queue.
166 * NOTE: there is magic here about the way the queue is plugged if
167 * we have no outstanding commands.
169 * Although this *doesn't* plug the queue, it does call the request
170 * function. The SCSI request function detects the blocked condition
171 * and plugs the queue appropriately.
173 blk_insert_request(device->request_queue, cmd->request, 1, cmd, 1);
178 * Function: scsi_do_req
180 * Purpose: Queue a SCSI request
182 * Arguments: sreq - command descriptor.
183 * cmnd - actual SCSI command to be performed.
184 * buffer - data buffer.
185 * bufflen - size of data buffer.
186 * done - completion function to be run.
187 * timeout - how long to let it run before timeout.
188 * retries - number of retries we allow.
190 * Lock status: No locks held upon entry.
194 * Notes: This function is only used for queueing requests for things
195 * like ioctls and character device requests - this is because
196 * we essentially just inject a request into the queue for the
199 * In order to support the scsi_device_quiesce function, we
200 * now inject requests on the *head* of the device queue
201 * rather than the tail.
203 void scsi_do_req(struct scsi_request *sreq, const void *cmnd,
204 void *buffer, unsigned bufflen,
205 void (*done)(struct scsi_cmnd *),
206 int timeout, int retries)
209 * If the upper level driver is reusing these things, then
210 * we should release the low-level block now. Another one will
211 * be allocated later when this request is getting queued.
213 __scsi_release_request(sreq);
216 * Our own function scsi_done (which marks the host as not busy,
217 * disables the timeout counter, etc) will be called by us or by the
218 * scsi_hosts[host].queuecommand() function needs to also call
219 * the completion function for the high level driver.
221 memcpy(sreq->sr_cmnd, cmnd, sizeof(sreq->sr_cmnd));
222 sreq->sr_bufflen = bufflen;
223 sreq->sr_buffer = buffer;
224 sreq->sr_allowed = retries;
225 sreq->sr_done = done;
226 sreq->sr_timeout_per_command = timeout;
228 if (sreq->sr_cmd_len == 0)
229 sreq->sr_cmd_len = COMMAND_SIZE(sreq->sr_cmnd[0]);
232 * head injection *required* here otherwise quiesce won't work
234 scsi_insert_special_req(sreq, 1);
237 static void scsi_wait_done(struct scsi_cmnd *cmd)
239 struct request *req = cmd->request;
240 struct request_queue *q = cmd->device->request_queue;
243 req->rq_status = RQ_SCSI_DONE; /* Busy, but indicate request done */
245 spin_lock_irqsave(q->queue_lock, flags);
246 if (blk_rq_tagged(req))
247 blk_queue_end_tag(q, req);
248 spin_unlock_irqrestore(q->queue_lock, flags);
251 complete(req->waiting);
254 void scsi_wait_req(struct scsi_request *sreq, const void *cmnd, void *buffer,
255 unsigned bufflen, int timeout, int retries)
257 DECLARE_COMPLETION(wait);
259 sreq->sr_request->waiting = &wait;
260 sreq->sr_request->rq_status = RQ_SCSI_BUSY;
261 scsi_do_req(sreq, cmnd, buffer, bufflen, scsi_wait_done,
263 wait_for_completion(&wait);
264 sreq->sr_request->waiting = NULL;
265 if (sreq->sr_request->rq_status != RQ_SCSI_DONE)
266 sreq->sr_result |= (DRIVER_ERROR << 24);
268 __scsi_release_request(sreq);
272 * Function: scsi_init_cmd_errh()
274 * Purpose: Initialize cmd fields related to error handling.
276 * Arguments: cmd - command that is ready to be queued.
280 * Notes: This function has the job of initializing a number of
281 * fields related to error handling. Typically this will
282 * be called once for each command, as required.
284 static int scsi_init_cmd_errh(struct scsi_cmnd *cmd)
286 cmd->owner = SCSI_OWNER_MIDLEVEL;
287 cmd->serial_number = 0;
288 cmd->serial_number_at_timeout = 0;
289 cmd->abort_reason = 0;
291 memset(cmd->sense_buffer, 0, sizeof cmd->sense_buffer);
293 if (cmd->cmd_len == 0)
294 cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);
297 * We need saved copies of a number of fields - this is because
298 * error handling may need to overwrite these with different values
299 * to run different commands, and once error handling is complete,
300 * we will need to restore these values prior to running the actual
303 cmd->old_use_sg = cmd->use_sg;
304 cmd->old_cmd_len = cmd->cmd_len;
305 cmd->sc_old_data_direction = cmd->sc_data_direction;
306 cmd->old_underflow = cmd->underflow;
307 memcpy(cmd->data_cmnd, cmd->cmnd, sizeof(cmd->cmnd));
308 cmd->buffer = cmd->request_buffer;
309 cmd->bufflen = cmd->request_bufflen;
310 cmd->internal_timeout = NORMAL_TIMEOUT;
311 cmd->abort_reason = 0;
317 * Function: scsi_setup_cmd_retry()
319 * Purpose: Restore the command state for a retry
321 * Arguments: cmd - command to be restored
325 * Notes: Immediately prior to retrying a command, we need
326 * to restore certain fields that we saved above.
328 void scsi_setup_cmd_retry(struct scsi_cmnd *cmd)
330 memcpy(cmd->cmnd, cmd->data_cmnd, sizeof(cmd->data_cmnd));
331 cmd->request_buffer = cmd->buffer;
332 cmd->request_bufflen = cmd->bufflen;
333 cmd->use_sg = cmd->old_use_sg;
334 cmd->cmd_len = cmd->old_cmd_len;
335 cmd->sc_data_direction = cmd->sc_old_data_direction;
336 cmd->underflow = cmd->old_underflow;
339 void scsi_device_unbusy(struct scsi_device *sdev)
341 struct Scsi_Host *shost = sdev->host;
344 spin_lock_irqsave(shost->host_lock, flags);
346 if (unlikely(test_bit(SHOST_RECOVERY, &shost->shost_state) &&
348 scsi_eh_wakeup(shost);
349 spin_unlock(shost->host_lock);
350 spin_lock(&sdev->sdev_lock);
352 spin_unlock_irqrestore(&sdev->sdev_lock, flags);
356 * Called for single_lun devices on IO completion. Clear starget_sdev_user,
357 * and call blk_run_queue for all the scsi_devices on the target -
358 * including current_sdev first.
360 * Called with *no* scsi locks held.
362 static void scsi_single_lun_run(struct scsi_device *current_sdev)
364 struct Scsi_Host *shost = current_sdev->host;
365 struct scsi_device *sdev, *tmp;
368 spin_lock_irqsave(shost->host_lock, flags);
369 scsi_target(current_sdev)->starget_sdev_user = NULL;
370 spin_unlock_irqrestore(shost->host_lock, flags);
373 * Call blk_run_queue for all LUNs on the target, starting with
374 * current_sdev. We race with others (to set starget_sdev_user),
375 * but in most cases, we will be first. Ideally, each LU on the
376 * target would get some limited time or requests on the target.
378 blk_run_queue(current_sdev->request_queue);
380 spin_lock_irqsave(shost->host_lock, flags);
381 if (scsi_target(current_sdev)->starget_sdev_user)
383 list_for_each_entry_safe(sdev, tmp, ¤t_sdev->same_target_siblings,
384 same_target_siblings) {
385 if (scsi_device_get(sdev))
388 spin_unlock_irqrestore(shost->host_lock, flags);
389 blk_run_queue(sdev->request_queue);
390 spin_lock_irqsave(shost->host_lock, flags);
392 scsi_device_put(sdev);
395 spin_unlock_irqrestore(shost->host_lock, flags);
399 * Function: scsi_run_queue()
401 * Purpose: Select a proper request queue to serve next
403 * Arguments: q - last request's queue
407 * Notes: The previous command was completely finished, start
408 * a new one if possible.
410 static void scsi_run_queue(struct request_queue *q)
412 struct scsi_device *sdev = q->queuedata;
413 struct Scsi_Host *shost = sdev->host;
416 if (sdev->single_lun)
417 scsi_single_lun_run(sdev);
419 spin_lock_irqsave(shost->host_lock, flags);
420 while (!list_empty(&shost->starved_list) &&
421 !shost->host_blocked && !shost->host_self_blocked &&
422 !((shost->can_queue > 0) &&
423 (shost->host_busy >= shost->can_queue))) {
425 * As long as shost is accepting commands and we have
426 * starved queues, call blk_run_queue. scsi_request_fn
427 * drops the queue_lock and can add us back to the
430 * host_lock protects the starved_list and starved_entry.
431 * scsi_request_fn must get the host_lock before checking
432 * or modifying starved_list or starved_entry.
434 sdev = list_entry(shost->starved_list.next,
435 struct scsi_device, starved_entry);
436 list_del_init(&sdev->starved_entry);
437 spin_unlock_irqrestore(shost->host_lock, flags);
439 blk_run_queue(sdev->request_queue);
441 spin_lock_irqsave(shost->host_lock, flags);
442 if (unlikely(!list_empty(&sdev->starved_entry)))
444 * sdev lost a race, and was put back on the
445 * starved list. This is unlikely but without this
446 * in theory we could loop forever.
450 spin_unlock_irqrestore(shost->host_lock, flags);
456 * Function: scsi_requeue_command()
458 * Purpose: Handle post-processing of completed commands.
460 * Arguments: q - queue to operate on
461 * cmd - command that may need to be requeued.
465 * Notes: After command completion, there may be blocks left
466 * over which weren't finished by the previous command
467 * this can be for a number of reasons - the main one is
468 * I/O errors in the middle of the request, in which case
469 * we need to request the blocks that come after the bad
472 static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
474 cmd->request->flags &= ~REQ_DONTPREP;
475 blk_insert_request(q, cmd->request, 1, cmd, 1);
480 void scsi_next_command(struct scsi_cmnd *cmd)
482 struct request_queue *q = cmd->device->request_queue;
484 scsi_put_command(cmd);
488 void scsi_run_host_queues(struct Scsi_Host *shost)
490 struct scsi_device *sdev;
492 shost_for_each_device(sdev, shost)
493 scsi_run_queue(sdev->request_queue);
497 * Function: scsi_end_request()
499 * Purpose: Post-processing of completed commands called from interrupt
500 * handler or a bottom-half handler.
502 * Arguments: cmd - command that is complete.
503 * uptodate - 1 if I/O indicates success, 0 for I/O error.
504 * sectors - number of sectors we want to mark.
505 * requeue - indicates whether we should requeue leftovers.
506 * frequeue - indicates that if we release the command block
507 * that the queue request function should be called.
509 * Lock status: Assumed that lock is not held upon entry.
513 * Notes: This is called for block device requests in order to
514 * mark some number of sectors as complete.
516 * We are guaranteeing that the request queue will be goosed
517 * at some point during this call.
519 static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int uptodate,
520 int bytes, int requeue)
522 request_queue_t *q = cmd->device->request_queue;
523 struct request *req = cmd->request;
527 * If there are blocks left over at the end, set up the command
528 * to queue the remainder of them.
530 if (end_that_request_chunk(req, uptodate, bytes)) {
531 int leftover = (req->hard_nr_sectors << 9);
533 if (blk_pc_request(req))
534 leftover = req->data_len;
536 /* kill remainder if no retrys */
537 if (!uptodate && blk_noretry_request(req))
538 end_that_request_chunk(req, 0, leftover);
542 * Bleah. Leftovers again. Stick the
543 * leftovers in the front of the
544 * queue, and goose the queue again.
546 scsi_requeue_command(q, cmd);
552 add_disk_randomness(req->rq_disk);
554 spin_lock_irqsave(q->queue_lock, flags);
555 if (blk_rq_tagged(req))
556 blk_queue_end_tag(q, req);
557 end_that_request_last(req);
558 spin_unlock_irqrestore(q->queue_lock, flags);
561 * This will goose the queue request function at the end, so we don't
562 * need to worry about launching another command.
564 scsi_next_command(cmd);
568 static struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, int gfp_mask)
570 struct scsi_host_sg_pool *sgp;
571 struct scatterlist *sgl;
573 BUG_ON(!cmd->use_sg);
575 switch (cmd->use_sg) {
585 #if (SCSI_MAX_PHYS_SEGMENTS > 32)
589 #if (SCSI_MAX_PHYS_SEGMENTS > 64)
593 #if (SCSI_MAX_PHYS_SEGMENTS > 128)
604 sgp = scsi_sg_pools + cmd->sglist_len;
605 sgl = mempool_alloc(sgp->pool, gfp_mask);
607 memset(sgl, 0, sgp->size);
611 static void scsi_free_sgtable(struct scatterlist *sgl, int index)
613 struct scsi_host_sg_pool *sgp;
615 BUG_ON(index > SG_MEMPOOL_NR);
617 sgp = scsi_sg_pools + index;
618 mempool_free(sgl, sgp->pool);
622 * Function: scsi_release_buffers()
624 * Purpose: Completion processing for block device I/O requests.
626 * Arguments: cmd - command that we are bailing.
628 * Lock status: Assumed that no lock is held upon entry.
632 * Notes: In the event that an upper level driver rejects a
633 * command, we must release resources allocated during
634 * the __init_io() function. Primarily this would involve
635 * the scatter-gather table, and potentially any bounce
638 static void scsi_release_buffers(struct scsi_cmnd *cmd)
640 struct request *req = cmd->request;
643 * Free up any indirection buffers we allocated for DMA purposes.
646 scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
647 else if (cmd->request_buffer != req->buffer)
648 kfree(cmd->request_buffer);
651 * Zero these out. They now point to freed memory, and it is
652 * dangerous to hang onto the pointers.
656 cmd->request_buffer = NULL;
657 cmd->request_bufflen = 0;
661 * Function: scsi_io_completion()
663 * Purpose: Completion processing for block device I/O requests.
665 * Arguments: cmd - command that is finished.
667 * Lock status: Assumed that no lock is held upon entry.
671 * Notes: This function is matched in terms of capabilities to
672 * the function that created the scatter-gather list.
673 * In other words, if there are no bounce buffers
674 * (the normal case for most drivers), we don't need
675 * the logic to deal with cleaning up afterwards.
677 * We must do one of several things here:
679 * a) Call scsi_end_request. This will finish off the
680 * specified number of sectors. If we are done, the
681 * command block will be released, and the queue
682 * function will be goosed. If we are not done, then
683 * scsi_end_request will directly goose the queue.
685 * b) We can just use scsi_requeue_command() here. This would
686 * be used if we just wanted to retry, for example.
688 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
689 unsigned int block_bytes)
691 int result = cmd->result;
692 int this_count = cmd->bufflen;
693 request_queue_t *q = cmd->device->request_queue;
694 struct request *req = cmd->request;
695 int clear_errors = 1;
696 struct scsi_sense_hdr sshdr;
699 * Free up any indirection buffers we allocated for DMA purposes.
700 * For the case of a READ, we need to copy the data out of the
701 * bounce buffer and into the real buffer.
704 scsi_free_sgtable(cmd->buffer, cmd->sglist_len);
705 else if (cmd->buffer != req->buffer) {
706 if (rq_data_dir(req) == READ) {
708 char *to = bio_kmap_irq(req->bio, &flags);
709 memcpy(to, cmd->buffer, cmd->bufflen);
710 bio_kunmap_irq(to, &flags);
715 if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
716 req->errors = result;
719 if (scsi_command_normalize_sense(cmd, &sshdr)) {
721 * SG_IO wants to know about deferred errors
723 int len = 8 + cmd->sense_buffer[7];
725 if (len > SCSI_SENSE_BUFFERSIZE)
726 len = SCSI_SENSE_BUFFERSIZE;
727 memcpy(req->sense, cmd->sense_buffer, len);
728 req->sense_len = len;
731 req->data_len = cmd->resid;
735 * Zero these out. They now point to freed memory, and it is
736 * dangerous to hang onto the pointers.
740 cmd->request_buffer = NULL;
741 cmd->request_bufflen = 0;
744 * Next deal with any sectors which we were able to correctly
747 if (good_bytes >= 0) {
748 SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, %d bytes done.\n",
749 req->nr_sectors, good_bytes));
750 SCSI_LOG_HLCOMPLETE(1, printk("use_sg is %d\n", cmd->use_sg));
755 * If multiple sectors are requested in one buffer, then
756 * they will have been finished off by the first command.
757 * If not, then we have a multi-buffer command.
759 * If block_bytes != 0, it means we had a medium error
760 * of some sort, and that we want to mark some number of
761 * sectors as not uptodate. Thus we want to inhibit
762 * requeueing right here - we will requeue down below
763 * when we handle the bad sectors.
765 cmd = scsi_end_request(cmd, 1, good_bytes, result == 0);
768 * If the command completed without error, then either finish off the
769 * rest of the command, or start a new one.
771 if (result == 0 || cmd == NULL ) {
776 * Now, if we were good little boys and girls, Santa left us a request
777 * sense buffer. We can extract information from this, so we
778 * can choose a block to remap, etc.
780 if (driver_byte(result) != 0) {
781 if (scsi_command_normalize_sense(cmd, &sshdr) &&
782 !scsi_sense_is_deferred(&sshdr)) {
784 * If the device is in the process of becoming ready,
787 if (sshdr.asc == 0x04 && sshdr.ascq == 0x01) {
788 scsi_requeue_command(q, cmd);
791 if (sshdr.sense_key == UNIT_ATTENTION) {
792 if (cmd->device->removable) {
793 /* detected disc change. set a bit
794 * and quietly refuse further access.
796 cmd->device->changed = 1;
797 cmd = scsi_end_request(cmd, 0,
802 * Must have been a power glitch, or a
803 * bus reset. Could not have been a
804 * media change, so we just retry the
805 * request and see what happens.
807 scsi_requeue_command(q, cmd);
813 * If we had an ILLEGAL REQUEST returned, then we may have
814 * performed an unsupported command. The only thing this
815 * should be would be a ten byte read where only a six byte
816 * read was supported. Also, on a system where READ CAPACITY
817 * failed, we may have read past the end of the disk.
821 * XXX: Following is probably broken since deferred errors
822 * fall through [dpg 20040827]
824 switch (sshdr.sense_key) {
825 case ILLEGAL_REQUEST:
826 if (cmd->device->use_10_for_rw &&
827 (cmd->cmnd[0] == READ_10 ||
828 cmd->cmnd[0] == WRITE_10)) {
829 cmd->device->use_10_for_rw = 0;
831 * This will cause a retry with a 6-byte
834 scsi_requeue_command(q, cmd);
837 cmd = scsi_end_request(cmd, 0, this_count, 1);
842 printk(KERN_INFO "Device %s not ready.\n",
843 req->rq_disk ? req->rq_disk->disk_name : "");
844 cmd = scsi_end_request(cmd, 0, this_count, 1);
846 case VOLUME_OVERFLOW:
847 printk("scsi%d: ERROR on channel %d, id %d, lun %d, CDB: ",
848 cmd->device->host->host_no, (int) cmd->device->channel,
849 (int) cmd->device->id, (int) cmd->device->lun);
850 __scsi_print_command(cmd->data_cmnd);
851 scsi_print_sense("", cmd);
852 cmd = scsi_end_request(cmd, 0, block_bytes, 1);
857 } /* driver byte != 0 */
858 if (host_byte(result) == DID_RESET) {
860 * Third party bus reset or reset for error
861 * recovery reasons. Just retry the request
862 * and see what happens.
864 scsi_requeue_command(q, cmd);
868 printk("SCSI error : <%d %d %d %d> return code = 0x%x\n",
869 cmd->device->host->host_no,
870 cmd->device->channel,
872 cmd->device->lun, result);
874 if (driver_byte(result) & DRIVER_SENSE)
875 scsi_print_sense("", cmd);
877 * Mark a single buffer as not uptodate. Queue the remainder.
878 * We sometimes get this cruft in the event that a medium error
879 * isn't properly reported.
881 block_bytes = req->hard_cur_sectors << 9;
883 block_bytes = req->data_len;
884 cmd = scsi_end_request(cmd, 0, block_bytes, 1);
889 * Function: scsi_init_io()
891 * Purpose: SCSI I/O initialize function.
893 * Arguments: cmd - Command descriptor we wish to initialize
895 * Returns: 0 on success
896 * BLKPREP_DEFER if the failure is retryable
897 * BLKPREP_KILL if the failure is fatal
899 static int scsi_init_io(struct scsi_cmnd *cmd)
901 struct request *req = cmd->request;
902 struct scatterlist *sgpnt;
906 * if this is a rq->data based REQ_BLOCK_PC, setup for a non-sg xfer
908 if ((req->flags & REQ_BLOCK_PC) && !req->bio) {
909 cmd->request_bufflen = req->data_len;
910 cmd->request_buffer = req->data;
911 req->buffer = req->data;
917 * we used to not use scatter-gather for single segment request,
918 * but now we do (it makes highmem I/O easier to support without
921 cmd->use_sg = req->nr_phys_segments;
924 * if sg table allocation fails, requeue request later.
926 sgpnt = scsi_alloc_sgtable(cmd, GFP_ATOMIC);
927 if (unlikely(!sgpnt)) {
928 req->flags |= REQ_SPECIAL;
929 return BLKPREP_DEFER;
932 cmd->request_buffer = (char *) sgpnt;
933 cmd->request_bufflen = req->nr_sectors << 9;
934 if (blk_pc_request(req))
935 cmd->request_bufflen = req->data_len;
939 * Next, walk the list, and fill in the addresses and sizes of
942 count = blk_rq_map_sg(req->q, req, cmd->request_buffer);
945 * mapped well, send it off
947 if (likely(count <= cmd->use_sg)) {
952 printk(KERN_ERR "Incorrect number of segments after building list\n");
953 printk(KERN_ERR "counted %d, received %d\n", count, cmd->use_sg);
954 printk(KERN_ERR "req nr_sec %lu, cur_nr_sec %u\n", req->nr_sectors,
955 req->current_nr_sectors);
957 /* release the command and kill it */
958 scsi_release_buffers(cmd);
959 scsi_put_command(cmd);
963 static int scsi_issue_flush_fn(request_queue_t *q, struct gendisk *disk,
964 sector_t *error_sector)
966 struct scsi_device *sdev = q->queuedata;
967 struct scsi_driver *drv;
969 if (sdev->sdev_state != SDEV_RUNNING)
972 drv = *(struct scsi_driver **) disk->private_data;
973 if (drv->issue_flush)
974 return drv->issue_flush(&sdev->sdev_gendev, error_sector);
979 static int scsi_prep_fn(struct request_queue *q, struct request *req)
981 struct scsi_device *sdev = q->queuedata;
982 struct scsi_cmnd *cmd;
983 int specials_only = 0;
986 * Just check to see if the device is online. If it isn't, we
987 * refuse to process any commands. The device must be brought
988 * online before trying any recovery commands
990 if (unlikely(!scsi_device_online(sdev))) {
991 printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to offline device\n",
992 sdev->host->host_no, sdev->id, sdev->lun);
995 if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
996 /* OK, we're not in a running state don't prep
998 if (sdev->sdev_state == SDEV_DEL) {
999 /* Device is fully deleted, no commands
1000 * at all allowed down */
1001 printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to dead device\n",
1002 sdev->host->host_no, sdev->id, sdev->lun);
1003 return BLKPREP_KILL;
1005 /* OK, we only allow special commands (i.e. not
1006 * user initiated ones */
1007 specials_only = sdev->sdev_state;
1011 * Find the actual device driver associated with this command.
1012 * The SPECIAL requests are things like character device or
1013 * ioctls, which did not originate from ll_rw_blk. Note that
1014 * the special field is also used to indicate the cmd for
1015 * the remainder of a partially fulfilled request that can
1016 * come up when there is a medium error. We have to treat
1017 * these two cases differently. We differentiate by looking
1018 * at request->cmd, as this tells us the real story.
1020 if (req->flags & REQ_SPECIAL) {
1021 struct scsi_request *sreq = req->special;
1023 if (sreq->sr_magic == SCSI_REQ_MAGIC) {
1024 cmd = scsi_get_command(sreq->sr_device, GFP_ATOMIC);
1027 scsi_init_cmd_from_req(cmd, sreq);
1030 } else if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1032 if(unlikely(specials_only)) {
1033 if(specials_only == SDEV_QUIESCE ||
1034 specials_only == SDEV_BLOCK)
1035 return BLKPREP_DEFER;
1037 printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to device being removed\n",
1038 sdev->host->host_no, sdev->id, sdev->lun);
1039 return BLKPREP_KILL;
1044 * Now try and find a command block that we can use.
1046 if (!req->special) {
1047 cmd = scsi_get_command(sdev, GFP_ATOMIC);
1053 /* pull a tag out of the request if we have one */
1054 cmd->tag = req->tag;
1056 blk_dump_rq_flags(req, "SCSI bad req");
1057 return BLKPREP_KILL;
1060 /* note the overloading of req->special. When the tag
1061 * is active it always means cmd. If the tag goes
1062 * back for re-queueing, it may be reset */
1067 * FIXME: drop the lock here because the functions below
1068 * expect to be called without the queue lock held. Also,
1069 * previously, we dequeued the request before dropping the
1070 * lock. We hope REQ_STARTED prevents anything untoward from
1073 if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
1074 struct scsi_driver *drv;
1078 * This will do a couple of things:
1079 * 1) Fill in the actual SCSI command.
1080 * 2) Fill in any other upper-level specific fields
1083 * If this returns 0, it means that the request failed
1084 * (reading past end of disk, reading offline device,
1085 * etc). This won't actually talk to the device, but
1086 * some kinds of consistency checking may cause the
1087 * request to be rejected immediately.
1091 * This sets up the scatter-gather table (allocating if
1094 ret = scsi_init_io(cmd);
1095 if (ret) /* BLKPREP_KILL return also releases the command */
1099 * Initialize the actual SCSI command for this request.
1101 drv = *(struct scsi_driver **)req->rq_disk->private_data;
1102 if (unlikely(!drv->init_command(cmd))) {
1103 scsi_release_buffers(cmd);
1104 scsi_put_command(cmd);
1105 return BLKPREP_KILL;
1110 * The request is now prepped, no need to come back here
1112 req->flags |= REQ_DONTPREP;
1116 /* If we defer, the elv_next_request() returns NULL, but the
1117 * queue must be restarted, so we plug here if no returning
1118 * command will automatically do that. */
1119 if (sdev->device_busy == 0)
1121 return BLKPREP_DEFER;
1125 * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1128 * Called with the queue_lock held.
1130 static inline int scsi_dev_queue_ready(struct request_queue *q,
1131 struct scsi_device *sdev)
1133 if (sdev->device_busy >= sdev->queue_depth)
1135 if (sdev->device_busy == 0 && sdev->device_blocked) {
1137 * unblock after device_blocked iterates to zero
1139 if (--sdev->device_blocked == 0) {
1141 printk("scsi%d (%d:%d) unblocking device at"
1142 " zero depth\n", sdev->host->host_no,
1143 sdev->id, sdev->lun));
1149 if (sdev->device_blocked)
1156 * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1157 * return 0. We must end up running the queue again whenever 0 is
1158 * returned, else IO can hang.
1160 * Called with host_lock held.
1162 static inline int scsi_host_queue_ready(struct request_queue *q,
1163 struct Scsi_Host *shost,
1164 struct scsi_device *sdev)
1166 if (test_bit(SHOST_RECOVERY, &shost->shost_state))
1168 if (shost->host_busy == 0 && shost->host_blocked) {
1170 * unblock after host_blocked iterates to zero
1172 if (--shost->host_blocked == 0) {
1174 printk("scsi%d unblocking host at zero depth\n",
1181 if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
1182 shost->host_blocked || shost->host_self_blocked) {
1183 if (list_empty(&sdev->starved_entry))
1184 list_add_tail(&sdev->starved_entry, &shost->starved_list);
1188 /* We're OK to process the command, so we can't be starved */
1189 if (!list_empty(&sdev->starved_entry))
1190 list_del_init(&sdev->starved_entry);
1196 * Function: scsi_request_fn()
1198 * Purpose: Main strategy routine for SCSI.
1200 * Arguments: q - Pointer to actual queue.
1204 * Lock status: IO request lock assumed to be held when called.
1206 static void scsi_request_fn(struct request_queue *q)
1208 struct scsi_device *sdev = q->queuedata;
1209 struct Scsi_Host *shost = sdev->host;
1210 struct scsi_cmnd *cmd;
1211 struct request *req;
1213 if(!get_device(&sdev->sdev_gendev))
1214 /* We must be tearing the block queue down already */
1218 * To start with, we keep looping until the queue is empty, or until
1219 * the host is no longer able to accept any more requests.
1221 while (!blk_queue_plugged(q)) {
1224 * get next queueable request. We do this early to make sure
1225 * that the request is fully prepared even if we cannot
1228 req = elv_next_request(q);
1229 if (!req || !scsi_dev_queue_ready(q, sdev))
1232 if (unlikely(!scsi_device_online(sdev))) {
1233 printk(KERN_ERR "scsi%d (%d:%d): rejecting I/O to offline device\n",
1234 sdev->host->host_no, sdev->id, sdev->lun);
1235 blkdev_dequeue_request(req);
1236 req->flags |= REQ_QUIET;
1237 while (end_that_request_first(req, 0, req->nr_sectors))
1239 end_that_request_last(req);
1245 * Remove the request from the request list.
1247 if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1248 blkdev_dequeue_request(req);
1249 sdev->device_busy++;
1251 spin_unlock(q->queue_lock);
1252 spin_lock(shost->host_lock);
1254 if (!scsi_host_queue_ready(q, shost, sdev))
1256 if (sdev->single_lun) {
1257 if (scsi_target(sdev)->starget_sdev_user &&
1258 scsi_target(sdev)->starget_sdev_user != sdev)
1260 scsi_target(sdev)->starget_sdev_user = sdev;
1265 * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1266 * take the lock again.
1268 spin_unlock_irq(shost->host_lock);
1271 if (unlikely(cmd == NULL)) {
1272 printk(KERN_CRIT "impossible request in %s.\n"
1273 "please mail a stack trace to "
1274 "linux-scsi@vger.kernel.org",
1280 * Finally, initialize any error handling parameters, and set up
1281 * the timers for timeouts.
1283 scsi_init_cmd_errh(cmd);
1286 * Dispatch the command to the low-level driver.
1288 rtn = scsi_dispatch_cmd(cmd);
1289 spin_lock_irq(q->queue_lock);
1291 /* we're refusing the command; because of
1292 * the way locks get dropped, we need to
1293 * check here if plugging is required */
1294 if(sdev->device_busy == 0)
1304 spin_unlock_irq(shost->host_lock);
1307 * lock q, handle tag, requeue req, and decrement device_busy. We
1308 * must return with queue_lock held.
1310 * Decrementing device_busy without checking it is OK, as all such
1311 * cases (host limits or settings) should run the queue at some
1314 spin_lock_irq(q->queue_lock);
1315 blk_requeue_request(q, req);
1316 sdev->device_busy--;
1317 if(sdev->device_busy == 0)
1320 /* must be careful here...if we trigger the ->remove() function
1321 * we cannot be holding the q lock */
1322 spin_unlock_irq(q->queue_lock);
1323 put_device(&sdev->sdev_gendev);
1324 spin_lock_irq(q->queue_lock);
1327 u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1329 struct device *host_dev;
1330 u64 bounce_limit = 0xffffffff;
1332 if (shost->unchecked_isa_dma)
1333 return BLK_BOUNCE_ISA;
1335 * Platforms with virtual-DMA translation
1336 * hardware have no practical limit.
1338 if (!PCI_DMA_BUS_IS_PHYS)
1339 return BLK_BOUNCE_ANY;
1341 host_dev = scsi_get_device(shost);
1342 if (host_dev && host_dev->dma_mask)
1343 bounce_limit = *host_dev->dma_mask;
1345 return bounce_limit;
1348 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1350 struct Scsi_Host *shost = sdev->host;
1351 struct request_queue *q;
1353 q = blk_init_queue(scsi_request_fn, &sdev->sdev_lock);
1357 blk_queue_prep_rq(q, scsi_prep_fn);
1359 blk_queue_max_hw_segments(q, shost->sg_tablesize);
1360 blk_queue_max_phys_segments(q, SCSI_MAX_PHYS_SEGMENTS);
1361 blk_queue_max_sectors(q, shost->max_sectors);
1362 blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1363 blk_queue_segment_boundary(q, shost->dma_boundary);
1364 blk_queue_issue_flush_fn(q, scsi_issue_flush_fn);
1366 if (!shost->use_clustering)
1367 clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
1371 void scsi_free_queue(struct request_queue *q)
1373 blk_cleanup_queue(q);
1377 * Function: scsi_block_requests()
1379 * Purpose: Utility function used by low-level drivers to prevent further
1380 * commands from being queued to the device.
1382 * Arguments: shost - Host in question
1386 * Lock status: No locks are assumed held.
1388 * Notes: There is no timer nor any other means by which the requests
1389 * get unblocked other than the low-level driver calling
1390 * scsi_unblock_requests().
1392 void scsi_block_requests(struct Scsi_Host *shost)
1394 shost->host_self_blocked = 1;
1398 * Function: scsi_unblock_requests()
1400 * Purpose: Utility function used by low-level drivers to allow further
1401 * commands from being queued to the device.
1403 * Arguments: shost - Host in question
1407 * Lock status: No locks are assumed held.
1409 * Notes: There is no timer nor any other means by which the requests
1410 * get unblocked other than the low-level driver calling
1411 * scsi_unblock_requests().
1413 * This is done as an API function so that changes to the
1414 * internals of the scsi mid-layer won't require wholesale
1415 * changes to drivers that use this feature.
1417 void scsi_unblock_requests(struct Scsi_Host *shost)
1419 shost->host_self_blocked = 0;
1420 scsi_run_host_queues(shost);
1423 int __init scsi_init_queue(void)
1427 for (i = 0; i < SG_MEMPOOL_NR; i++) {
1428 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1429 int size = sgp->size * sizeof(struct scatterlist);
1431 sgp->slab = kmem_cache_create(sgp->name, size, 0,
1432 SLAB_HWCACHE_ALIGN, NULL, NULL);
1434 printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1438 sgp->pool = mempool_create(SG_MEMPOOL_SIZE,
1439 mempool_alloc_slab, mempool_free_slab,
1442 printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1450 void scsi_exit_queue(void)
1454 for (i = 0; i < SG_MEMPOOL_NR; i++) {
1455 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1456 mempool_destroy(sgp->pool);
1457 kmem_cache_destroy(sgp->slab);
1461 * __scsi_mode_sense - issue a mode sense, falling back from 10 to
1462 * six bytes if necessary.
1463 * @sreq: SCSI request to fill in with the MODE_SENSE
1464 * @dbd: set if mode sense will allow block descriptors to be returned
1465 * @modepage: mode page being requested
1466 * @buffer: request buffer (may not be smaller than eight bytes)
1467 * @len: length of request buffer.
1468 * @timeout: command timeout
1469 * @retries: number of retries before failing
1470 * @data: returns a structure abstracting the mode header data
1472 * Returns zero if unsuccessful, or the header offset (either 4
1473 * or 8 depending on whether a six or ten byte command was
1474 * issued) if successful.
1477 __scsi_mode_sense(struct scsi_request *sreq, int dbd, int modepage,
1478 unsigned char *buffer, int len, int timeout, int retries,
1479 struct scsi_mode_data *data) {
1480 unsigned char cmd[12];
1484 memset(data, 0, sizeof(*data));
1485 memset(&cmd[0], 0, 12);
1486 cmd[1] = dbd & 0x18; /* allows DBD and LLBA bits */
1490 use_10_for_ms = sreq->sr_device->use_10_for_ms;
1492 if (use_10_for_ms) {
1496 cmd[0] = MODE_SENSE_10;
1503 cmd[0] = MODE_SENSE;
1508 sreq->sr_cmd_len = 0;
1509 memset(sreq->sr_sense_buffer, 0, sizeof(sreq->sr_sense_buffer));
1510 sreq->sr_data_direction = DMA_FROM_DEVICE;
1512 memset(buffer, 0, len);
1514 scsi_wait_req(sreq, cmd, buffer, len, timeout, retries);
1516 /* This code looks awful: what it's doing is making sure an
1517 * ILLEGAL REQUEST sense return identifies the actual command
1518 * byte as the problem. MODE_SENSE commands can return
1519 * ILLEGAL REQUEST if the code page isn't supported */
1521 if (use_10_for_ms && !scsi_status_is_good(sreq->sr_result) &&
1522 (driver_byte(sreq->sr_result) & DRIVER_SENSE)) {
1523 struct scsi_sense_hdr sshdr;
1525 if (scsi_request_normalize_sense(sreq, &sshdr)) {
1526 if ((sshdr.sense_key == ILLEGAL_REQUEST) &&
1527 (sshdr.asc == 0x20) && (sshdr.ascq == 0)) {
1529 * Invalid command operation code
1531 sreq->sr_device->use_10_for_ms = 0;
1537 if(scsi_status_is_good(sreq->sr_result)) {
1538 data->header_length = header_length;
1540 data->length = buffer[0]*256 + buffer[1] + 2;
1541 data->medium_type = buffer[2];
1542 data->device_specific = buffer[3];
1543 data->longlba = buffer[4] & 0x01;
1544 data->block_descriptor_length = buffer[6]*256
1547 data->length = buffer[0] + 1;
1548 data->medium_type = buffer[1];
1549 data->device_specific = buffer[2];
1550 data->block_descriptor_length = buffer[3];
1554 return sreq->sr_result;
1558 * scsi_mode_sense - issue a mode sense, falling back from 10 to
1559 * six bytes if necessary.
1560 * @sdev: scsi device to send command to.
1561 * @dbd: set if mode sense will disable block descriptors in the return
1562 * @modepage: mode page being requested
1563 * @buffer: request buffer (may not be smaller than eight bytes)
1564 * @len: length of request buffer.
1565 * @timeout: command timeout
1566 * @retries: number of retries before failing
1568 * Returns zero if unsuccessful, or the header offset (either 4
1569 * or 8 depending on whether a six or ten byte command was
1570 * issued) if successful.
1573 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
1574 unsigned char *buffer, int len, int timeout, int retries,
1575 struct scsi_mode_data *data)
1577 struct scsi_request *sreq = scsi_allocate_request(sdev, GFP_KERNEL);
1583 ret = __scsi_mode_sense(sreq, dbd, modepage, buffer, len,
1584 timeout, retries, data);
1586 scsi_release_request(sreq);
1592 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries)
1594 struct scsi_request *sreq;
1596 TEST_UNIT_READY, 0, 0, 0, 0, 0,
1600 sreq = scsi_allocate_request(sdev, GFP_KERNEL);
1604 sreq->sr_data_direction = DMA_NONE;
1605 scsi_wait_req(sreq, cmd, NULL, 0, timeout, retries);
1607 if ((driver_byte(sreq->sr_result) & DRIVER_SENSE) &&
1608 ((sreq->sr_sense_buffer[2] & 0x0f) == UNIT_ATTENTION ||
1609 (sreq->sr_sense_buffer[2] & 0x0f) == NOT_READY) &&
1612 sreq->sr_result = 0;
1614 result = sreq->sr_result;
1615 scsi_release_request(sreq);
1618 EXPORT_SYMBOL(scsi_test_unit_ready);
1621 * scsi_device_set_state - Take the given device through the device
1623 * @sdev: scsi device to change the state of.
1624 * @state: state to change to.
1626 * Returns zero if unsuccessful or an error if the requested
1627 * transition is illegal.
1630 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
1632 enum scsi_device_state oldstate = sdev->sdev_state;
1634 if (state == oldstate)
1639 /* There are no legal states that come back to
1640 * created. This is the manually initialised start
1709 sdev->sdev_state = state;
1713 dev_printk(KERN_ERR, &sdev->sdev_gendev,
1714 "Illegal state transition %s->%s\n",
1715 scsi_device_state_name(oldstate),
1716 scsi_device_state_name(state));
1720 EXPORT_SYMBOL(scsi_device_set_state);
1723 * scsi_device_quiesce - Block user issued commands.
1724 * @sdev: scsi device to quiesce.
1726 * This works by trying to transition to the SDEV_QUIESCE state
1727 * (which must be a legal transition). When the device is in this
1728 * state, only special requests will be accepted, all others will
1729 * be deferred. Since special requests may also be requeued requests,
1730 * a successful return doesn't guarantee the device will be
1731 * totally quiescent.
1733 * Must be called with user context, may sleep.
1735 * Returns zero if unsuccessful or an error if not.
1738 scsi_device_quiesce(struct scsi_device *sdev)
1740 int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
1744 scsi_run_queue(sdev->request_queue);
1745 while (sdev->device_busy) {
1746 msleep_interruptible(200);
1747 scsi_run_queue(sdev->request_queue);
1751 EXPORT_SYMBOL(scsi_device_quiesce);
1754 * scsi_device_resume - Restart user issued commands to a quiesced device.
1755 * @sdev: scsi device to resume.
1757 * Moves the device from quiesced back to running and restarts the
1760 * Must be called with user context, may sleep.
1763 scsi_device_resume(struct scsi_device *sdev)
1765 if(scsi_device_set_state(sdev, SDEV_RUNNING))
1767 scsi_run_queue(sdev->request_queue);
1769 EXPORT_SYMBOL(scsi_device_resume);
1772 device_quiesce_fn(struct device *dev, void *data)
1774 scsi_device_quiesce(to_scsi_device(dev));
1779 scsi_target_quiesce(struct scsi_target *starget)
1781 device_for_each_child(&starget->dev, NULL, device_quiesce_fn);
1783 EXPORT_SYMBOL(scsi_target_quiesce);
1786 device_resume_fn(struct device *dev, void *data)
1788 scsi_device_resume(to_scsi_device(dev));
1793 scsi_target_resume(struct scsi_target *starget)
1795 device_for_each_child(&starget->dev, NULL, device_resume_fn);
1797 EXPORT_SYMBOL(scsi_target_resume);
1800 * scsi_internal_device_block - internal function to put a device
1801 * temporarily into the SDEV_BLOCK state
1802 * @sdev: device to block
1804 * Block request made by scsi lld's to temporarily stop all
1805 * scsi commands on the specified device. Called from interrupt
1806 * or normal process context.
1808 * Returns zero if successful or error if not
1811 * This routine transitions the device to the SDEV_BLOCK state
1812 * (which must be a legal transition). When the device is in this
1813 * state, all commands are deferred until the scsi lld reenables
1814 * the device with scsi_device_unblock or device_block_tmo fires.
1815 * This routine assumes the host_lock is held on entry.
1818 scsi_internal_device_block(struct scsi_device *sdev)
1820 request_queue_t *q = sdev->request_queue;
1821 unsigned long flags;
1824 err = scsi_device_set_state(sdev, SDEV_BLOCK);
1829 * The device has transitioned to SDEV_BLOCK. Stop the
1830 * block layer from calling the midlayer with this device's
1833 spin_lock_irqsave(q->queue_lock, flags);
1835 spin_unlock_irqrestore(q->queue_lock, flags);
1839 EXPORT_SYMBOL_GPL(scsi_internal_device_block);
1842 * scsi_internal_device_unblock - resume a device after a block request
1843 * @sdev: device to resume
1845 * Called by scsi lld's or the midlayer to restart the device queue
1846 * for the previously suspended scsi device. Called from interrupt or
1847 * normal process context.
1849 * Returns zero if successful or error if not.
1852 * This routine transitions the device to the SDEV_RUNNING state
1853 * (which must be a legal transition) allowing the midlayer to
1854 * goose the queue for this device. This routine assumes the
1855 * host_lock is held upon entry.
1858 scsi_internal_device_unblock(struct scsi_device *sdev)
1860 request_queue_t *q = sdev->request_queue;
1862 unsigned long flags;
1865 * Try to transition the scsi device to SDEV_RUNNING
1866 * and goose the device queue if successful.
1868 err = scsi_device_set_state(sdev, SDEV_RUNNING);
1872 spin_lock_irqsave(q->queue_lock, flags);
1874 spin_unlock_irqrestore(q->queue_lock, flags);
1878 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);