1/*
   2 *  scsi_lib.c Copyright (C) 1999 Eric Youngdale
   3 *
   4 *  SCSI queueing library.
   5 *      Initial versions: Eric Youngdale (eric@andante.org).
   6 *                        Based upon conversations with large numbers
   7 *                        of people at Linux Expo.
   8 */
   9
  10#include <linux/bio.h>
  11#include <linux/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>
  22
  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>
  30
  31#include "scsi_priv.h"
  32#include "scsi_logging.h"
  33
  34
  35#define SG_MEMPOOL_NR		ARRAY_SIZE(scsi_sg_pools)
  36#define SG_MEMPOOL_SIZE		2
  37
  38struct scsi_host_sg_pool {
  39	size_t		size;
  40	char		*name;
  41	struct kmem_cache	*slab;
  42	mempool_t	*pool;
  43};
  44
  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)
  48#endif
  49static struct scsi_host_sg_pool scsi_sg_pools[] = {
  50	SP(8),
  51	SP(16),
  52#if (SCSI_MAX_SG_SEGMENTS > 32)
  53	SP(32),
  54#if (SCSI_MAX_SG_SEGMENTS > 64)
  55	SP(64),
  56#if (SCSI_MAX_SG_SEGMENTS > 128)
  57	SP(128),
  58#if (SCSI_MAX_SG_SEGMENTS > 256)
  59#error SCSI_MAX_SG_SEGMENTS is too large (256 MAX)
  60#endif
  61#endif
  62#endif
  63#endif
  64	SP(SCSI_MAX_SG_SEGMENTS)
  65};
  66#undef SP
  67
  68struct kmem_cache *scsi_sdb_cache;
  69
  70/*
  71 * When to reinvoke queueing after a resource shortage. It's 3 msecs to
  72 * not change behaviour from the previous unplug mechanism, experimentation
  73 * may prove this needs changing.
  74 */
  75#define SCSI_QUEUE_DELAY	3
  76
  77/*
  78 * Function:	scsi_unprep_request()
  79 *
  80 * Purpose:	Remove all preparation done for a request, including its
  81 *		associated scsi_cmnd, so that it can be requeued.
  82 *
  83 * Arguments:	req	- request to unprepare
  84 *
  85 * Lock status:	Assumed that no locks are held upon entry.
  86 *
  87 * Returns:	Nothing.
  88 */
  89static void scsi_unprep_request(struct request *req)
  90{
  91	struct scsi_cmnd *cmd = req->special;
  92
  93	blk_unprep_request(req);
  94	req->special = NULL;
  95
  96	scsi_put_command(cmd);
  97}
  98
  99/**
 100 * __scsi_queue_insert - private queue insertion
 101 * @cmd: The SCSI command being requeued
 102 * @reason:  The reason for the requeue
 103 * @unbusy: Whether the queue should be unbusied
 104 *
 105 * This is a private queue insertion.  The public interface
 106 * scsi_queue_insert() always assumes the queue should be unbusied
 107 * because it's always called before the completion.  This function is
 108 * for a requeue after completion, which should only occur in this
 109 * file.
 110 */
 111static int __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)
 112{
 113	struct Scsi_Host *host = cmd->device->host;
 114	struct scsi_device *device = cmd->device;
 115	struct scsi_target *starget = scsi_target(device);
 116	struct request_queue *q = device->request_queue;
 117	unsigned long flags;
 118
 119	SCSI_LOG_MLQUEUE(1,
 120		 printk("Inserting command %p into mlqueue\n", cmd));
 121
 122	/*
 123	 * Set the appropriate busy bit for the device/host.
 124	 *
 125	 * If the host/device isn't busy, assume that something actually
 126	 * completed, and that we should be able to queue a command now.
 127	 *
 128	 * Note that the prior mid-layer assumption that any host could
 129	 * always queue at least one command is now broken.  The mid-layer
 130	 * will implement a user specifiable stall (see
 131	 * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
 132	 * if a command is requeued with no other commands outstanding
 133	 * either for the device or for the host.
 134	 */
 135	switch (reason) {
 136	case SCSI_MLQUEUE_HOST_BUSY:
 137		host->host_blocked = host->max_host_blocked;
 138		break;
 139	case SCSI_MLQUEUE_DEVICE_BUSY:
 140	case SCSI_MLQUEUE_EH_RETRY:
 141		device->device_blocked = device->max_device_blocked;
 142		break;
 143	case SCSI_MLQUEUE_TARGET_BUSY:
 144		starget->target_blocked = starget->max_target_blocked;
 145		break;
 146	}
 147
 148	/*
 149	 * Decrement the counters, since these commands are no longer
 150	 * active on the host/device.
 151	 */
 152	if (unbusy)
 153		scsi_device_unbusy(device);
 154
 155	/*
 156	 * Requeue this command.  It will go before all other commands
 157	 * that are already in the queue.
 158	 */
 159	spin_lock_irqsave(q->queue_lock, flags);
 160	blk_requeue_request(q, cmd->request);
 161	spin_unlock_irqrestore(q->queue_lock, flags);
 162
 163	kblockd_schedule_work(q, &device->requeue_work);
 164
 165	return 0;
 166}
 167
 168/*
 169 * Function:    scsi_queue_insert()
 170 *
 171 * Purpose:     Insert a command in the midlevel queue.
 172 *
 173 * Arguments:   cmd    - command that we are adding to queue.
 174 *              reason - why we are inserting command to queue.
 175 *
 176 * Lock status: Assumed that lock is not held upon entry.
 177 *
 178 * Returns:     Nothing.
 179 *
 180 * Notes:       We do this for one of two cases.  Either the host is busy
 181 *              and it cannot accept any more commands for the time being,
 182 *              or the device returned QUEUE_FULL and can accept no more
 183 *              commands.
 184 * Notes:       This could be called either from an interrupt context or a
 185 *              normal process context.
 186 */
 187int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
 188{
 189	return __scsi_queue_insert(cmd, reason, 1);
 190}
 191/**
 192 * scsi_execute - insert request and wait for the result
 193 * @sdev:	scsi device
 194 * @cmd:	scsi command
 195 * @data_direction: data direction
 196 * @buffer:	data buffer
 197 * @bufflen:	len of buffer
 198 * @sense:	optional sense buffer
 199 * @timeout:	request timeout in seconds
 200 * @retries:	number of times to retry request
 201 * @flags:	or into request flags;
 202 * @resid:	optional residual length
 203 *
 204 * returns the req->errors value which is the scsi_cmnd result
 205 * field.
 206 */
 207int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
 208		 int data_direction, void *buffer, unsigned bufflen,
 209		 unsigned char *sense, int timeout, int retries, int flags,
 210		 int *resid)
 211{
 212	struct request *req;
 213	int write = (data_direction == DMA_TO_DEVICE);
 214	int ret = DRIVER_ERROR << 24;
 215
 216	req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
 217	if (!req)
 218		return ret;
 219
 220	if (bufflen &&	blk_rq_map_kern(sdev->request_queue, req,
 221					buffer, bufflen, __GFP_WAIT))
 222		goto out;
 223
 224	req->cmd_len = COMMAND_SIZE(cmd[0]);
 225	memcpy(req->cmd, cmd, req->cmd_len);
 226	req->sense = sense;
 227	req->sense_len = 0;
 228	req->retries = retries;
 229	req->timeout = timeout;
 230	req->cmd_type = REQ_TYPE_BLOCK_PC;
 231	req->cmd_flags |= flags | REQ_QUIET | REQ_PREEMPT;
 232
 233	/*
 234	 * head injection *required* here otherwise quiesce won't work
 235	 */
 236	blk_execute_rq(req->q, NULL, req, 1);
 237
 238	/*
 239	 * Some devices (USB mass-storage in particular) may transfer
 240	 * garbage data together with a residue indicating that the data
 241	 * is invalid.  Prevent the garbage from being misinterpreted
 242	 * and prevent security leaks by zeroing out the excess data.
 243	 */
 244	if (unlikely(req->resid_len > 0 && req->resid_len <= bufflen))
 245		memset(buffer + (bufflen - req->resid_len), 0, req->resid_len);
 246
 247	if (resid)
 248		*resid = req->resid_len;
 249	ret = req->errors;
 250 out:
 251	blk_put_request(req);
 252
 253	return ret;
 254}
 255EXPORT_SYMBOL(scsi_execute);
 256
 257
 258int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
 259		     int data_direction, void *buffer, unsigned bufflen,
 260		     struct scsi_sense_hdr *sshdr, int timeout, int retries,
 261		     int *resid)
 262{
 263	char *sense = NULL;
 264	int result;
 265	
 266	if (sshdr) {
 267		sense = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
 268		if (!sense)
 269			return DRIVER_ERROR << 24;
 270	}
 271	result = scsi_execute(sdev, cmd, data_direction, buffer, bufflen,
 272			      sense, timeout, retries, 0, resid);
 273	if (sshdr)
 274		scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, sshdr);
 275
 276	kfree(sense);
 277	return result;
 278}
 279EXPORT_SYMBOL(scsi_execute_req);
 280
 281/*
 282 * Function:    scsi_init_cmd_errh()
 283 *
 284 * Purpose:     Initialize cmd fields related to error handling.
 285 *
 286 * Arguments:   cmd	- command that is ready to be queued.
 287 *
 288 * Notes:       This function has the job of initializing a number of
 289 *              fields related to error handling.   Typically this will
 290 *              be called once for each command, as required.
 291 */
 292static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
 293{
 294	cmd->serial_number = 0;
 295	scsi_set_resid(cmd, 0);
 296	memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
 297	if (cmd->cmd_len == 0)
 298		cmd->cmd_len = scsi_command_size(cmd->cmnd);
 299}
 300
 301void scsi_device_unbusy(struct scsi_device *sdev)
 302{
 303	struct Scsi_Host *shost = sdev->host;
 304	struct scsi_target *starget = scsi_target(sdev);
 305	unsigned long flags;
 306
 307	spin_lock_irqsave(shost->host_lock, flags);
 308	shost->host_busy--;
 309	starget->target_busy--;
 310	if (unlikely(scsi_host_in_recovery(shost) &&
 311		     (shost->host_failed || shost->host_eh_scheduled)))
 312		scsi_eh_wakeup(shost);
 313	spin_unlock(shost->host_lock);
 314	spin_lock(sdev->request_queue->queue_lock);
 315	sdev->device_busy--;
 316	spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
 317}
 318
 319/*
 320 * Called for single_lun devices on IO completion. Clear starget_sdev_user,
 321 * and call blk_run_queue for all the scsi_devices on the target -
 322 * including current_sdev first.
 323 *
 324 * Called with *no* scsi locks held.
 325 */
 326static void scsi_single_lun_run(struct scsi_device *current_sdev)
 327{
 328	struct Scsi_Host *shost = current_sdev->host;
 329	struct scsi_device *sdev, *tmp;
 330	struct scsi_target *starget = scsi_target(current_sdev);
 331	unsigned long flags;
 332
 333	spin_lock_irqsave(shost->host_lock, flags);
 334	starget->starget_sdev_user = NULL;
 335	spin_unlock_irqrestore(shost->host_lock, flags);
 336
 337	/*
 338	 * Call blk_run_queue for all LUNs on the target, starting with
 339	 * current_sdev. We race with others (to set starget_sdev_user),
 340	 * but in most cases, we will be first. Ideally, each LU on the
 341	 * target would get some limited time or requests on the target.
 342	 */
 343	blk_run_queue(current_sdev->request_queue);
 344
 345	spin_lock_irqsave(shost->host_lock, flags);
 346	if (starget->starget_sdev_user)
 347		goto out;
 348	list_for_each_entry_safe(sdev, tmp, &starget->devices,
 349			same_target_siblings) {
 350		if (sdev == current_sdev)
 351			continue;
 352		if (scsi_device_get(sdev))
 353			continue;
 354
 355		spin_unlock_irqrestore(shost->host_lock, flags);
 356		blk_run_queue(sdev->request_queue);
 357		spin_lock_irqsave(shost->host_lock, flags);
 358	
 359		scsi_device_put(sdev);
 360	}
 361 out:
 362	spin_unlock_irqrestore(shost->host_lock, flags);
 363}
 364
 365static inline int scsi_device_is_busy(struct scsi_device *sdev)
 366{
 367	if (sdev->device_busy >= sdev->queue_depth || sdev->device_blocked)
 368		return 1;
 369
 370	return 0;
 371}
 372
 373static inline int scsi_target_is_busy(struct scsi_target *starget)
 374{
 375	return ((starget->can_queue > 0 &&
 376		 starget->target_busy >= starget->can_queue) ||
 377		 starget->target_blocked);
 378}
 379
 380static inline int scsi_host_is_busy(struct Scsi_Host *shost)
 381{
 382	if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
 383	    shost->host_blocked || shost->host_self_blocked)
 384		return 1;
 385
 386	return 0;
 387}
 388
 389/*
 390 * Function:	scsi_run_queue()
 391 *
 392 * Purpose:	Select a proper request queue to serve next
 393 *
 394 * Arguments:	q	- last request's queue
 395 *
 396 * Returns:     Nothing
 397 *
 398 * Notes:	The previous command was completely finished, start
 399 *		a new one if possible.
 400 */
 401static void scsi_run_queue(struct request_queue *q)
 402{
 403	struct scsi_device *sdev = q->queuedata;
 404	struct Scsi_Host *shost;
 405	LIST_HEAD(starved_list);
 406	unsigned long flags;
 407
 408	/* if the device is dead, sdev will be NULL, so no queue to run */
 409	if (!sdev)
 410		return;
 411
 412	shost = sdev->host;
 413	if (scsi_target(sdev)->single_lun)
 414		scsi_single_lun_run(sdev);
 415
 416	spin_lock_irqsave(shost->host_lock, flags);
 417	list_splice_init(&shost->starved_list, &starved_list);
 418
 419	while (!list_empty(&starved_list)) {
 420		/*
 421		 * As long as shost is accepting commands and we have
 422		 * starved queues, call blk_run_queue. scsi_request_fn
 423		 * drops the queue_lock and can add us back to the
 424		 * starved_list.
 425		 *
 426		 * host_lock protects the starved_list and starved_entry.
 427		 * scsi_request_fn must get the host_lock before checking
 428		 * or modifying starved_list or starved_entry.
 429		 */
 430		if (scsi_host_is_busy(shost))
 431			break;
 432
 433		sdev = list_entry(starved_list.next,
 434				  struct scsi_device, starved_entry);
 435		list_del_init(&sdev->starved_entry);
 436		if (scsi_target_is_busy(scsi_target(sdev))) {
 437			list_move_tail(&sdev->starved_entry,
 438				       &shost->starved_list);
 439			continue;
 440		}
 441
 442		spin_unlock(shost->host_lock);
 443		spin_lock(sdev->request_queue->queue_lock);
 444		__blk_run_queue(sdev->request_queue);
 445		spin_unlock(sdev->request_queue->queue_lock);
 446		spin_lock(shost->host_lock);
 447	}
 448	/* put any unprocessed entries back */
 449	list_splice(&starved_list, &shost->starved_list);
 450	spin_unlock_irqrestore(shost->host_lock, flags);
 451
 452	blk_run_queue(q);
 453}
 454
 455void scsi_requeue_run_queue(struct work_struct *work)
 456{
 457	struct scsi_device *sdev;
 458	struct request_queue *q;
 459
 460	sdev = container_of(work, struct scsi_device, requeue_work);
 461	q = sdev->request_queue;
 462	scsi_run_queue(q);
 463}
 464
 465/*
 466 * Function:	scsi_requeue_command()
 467 *
 468 * Purpose:	Handle post-processing of completed commands.
 469 *
 470 * Arguments:	q	- queue to operate on
 471 *		cmd	- command that may need to be requeued.
 472 *
 473 * Returns:	Nothing
 474 *
 475 * Notes:	After command completion, there may be blocks left
 476 *		over which weren't finished by the previous command
 477 *		this can be for a number of reasons - the main one is
 478 *		I/O errors in the middle of the request, in which case
 479 *		we need to request the blocks that come after the bad
 480 *		sector.
 481 * Notes:	Upon return, cmd is a stale pointer.
 482 */
 483static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
 484{
 485	struct request *req = cmd->request;
 486	unsigned long flags;
 487
 488	spin_lock_irqsave(q->queue_lock, flags);
 489	scsi_unprep_request(req);
 490	blk_requeue_request(q, req);
 491	spin_unlock_irqrestore(q->queue_lock, flags);
 492
 493	scsi_run_queue(q);
 494}
 495
 496void scsi_next_command(struct scsi_cmnd *cmd)
 497{
 498	struct scsi_device *sdev = cmd->device;
 499	struct request_queue *q = sdev->request_queue;
 500
 501	/* need to hold a reference on the device before we let go of the cmd */
 502	get_device(&sdev->sdev_gendev);
 503
 504	scsi_put_command(cmd);
 505	scsi_run_queue(q);
 506
 507	/* ok to remove device now */
 508	put_device(&sdev->sdev_gendev);
 509}
 510
 511void scsi_run_host_queues(struct Scsi_Host *shost)
 512{
 513	struct scsi_device *sdev;
 514
 515	shost_for_each_device(sdev, shost)
 516		scsi_run_queue(sdev->request_queue);
 517}
 518
 519static void __scsi_release_buffers(struct scsi_cmnd *, int);
 520
 521/*
 522 * Function:    scsi_end_request()
 523 *
 524 * Purpose:     Post-processing of completed commands (usually invoked at end
 525 *		of upper level post-processing and scsi_io_completion).
 526 *
 527 * Arguments:   cmd	 - command that is complete.
 528 *              error    - 0 if I/O indicates success, < 0 for I/O error.
 529 *              bytes    - number of bytes of completed I/O
 530 *		requeue  - indicates whether we should requeue leftovers.
 531 *
 532 * Lock status: Assumed that lock is not held upon entry.
 533 *
 534 * Returns:     cmd if requeue required, NULL otherwise.
 535 *
 536 * Notes:       This is called for block device requests in order to
 537 *              mark some number of sectors as complete.
 538 * 
 539 *		We are guaranteeing that the request queue will be goosed
 540 *		at some point during this call.
 541 * Notes:	If cmd was requeued, upon return it will be a stale pointer.
 542 */
 543static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
 544					  int bytes, int requeue)
 545{
 546	struct request_queue *q = cmd->device->request_queue;
 547	struct request *req = cmd->request;
 548
 549	/*
 550	 * If there are blocks left over at the end, set up the command
 551	 * to queue the remainder of them.
 552	 */
 553	if (blk_end_request(req, error, bytes)) {
 554		/* kill remainder if no retrys */
 555		if (error && scsi_noretry_cmd(cmd))
 556			blk_end_request_all(req, error);
 557		else {
 558			if (requeue) {
 559				/*
 560				 * Bleah.  Leftovers again.  Stick the
 561				 * leftovers in the front of the
 562				 * queue, and goose the queue again.
 563				 */
 564				scsi_release_buffers(cmd);
 565				scsi_requeue_command(q, cmd);
 566				cmd = NULL;
 567			}
 568			return cmd;
 569		}
 570	}
 571
 572	/*
 573	 * This will goose the queue request function at the end, so we don't
 574	 * need to worry about launching another command.
 575	 */
 576	__scsi_release_buffers(cmd, 0);
 577	scsi_next_command(cmd);
 578	return NULL;
 579}
 580
 581static inline unsigned int scsi_sgtable_index(unsigned short nents)
 582{
 583	unsigned int index;
 584
 585	BUG_ON(nents > SCSI_MAX_SG_SEGMENTS);
 586
 587	if (nents <= 8)
 588		index = 0;
 589	else
 590		index = get_count_order(nents) - 3;
 591
 592	return index;
 593}
 594
 595static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)
 596{
 597	struct scsi_host_sg_pool *sgp;
 598
 599	sgp = scsi_sg_pools + scsi_sgtable_index(nents);
 600	mempool_free(sgl, sgp->pool);
 601}
 602
 603static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
 604{
 605	struct scsi_host_sg_pool *sgp;
 606
 607	sgp = scsi_sg_pools + scsi_sgtable_index(nents);
 608	return mempool_alloc(sgp->pool, gfp_mask);
 609}
 610
 611static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents,
 612			      gfp_t gfp_mask)
 613{
 614	int ret;
 615
 616	BUG_ON(!nents);
 617
 618	ret = __sg_alloc_table(&sdb->table, nents, SCSI_MAX_SG_SEGMENTS,
 619			       gfp_mask, scsi_sg_alloc);
 620	if (unlikely(ret))
 621		__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS,
 622				scsi_sg_free);
 623
 624	return ret;
 625}
 626
 627static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
 628{
 629	__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
 630}
 631
 632static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
 633{
 634
 635	if (cmd->sdb.table.nents)
 636		scsi_free_sgtable(&cmd->sdb);
 637
 638	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
 639
 640	if (do_bidi_check && scsi_bidi_cmnd(cmd)) {
 641		struct scsi_data_buffer *bidi_sdb =
 642			cmd->request->next_rq->special;
 643		scsi_free_sgtable(bidi_sdb);
 644		kmem_cache_free(scsi_sdb_cache, bidi_sdb);
 645		cmd->request->next_rq->special = NULL;
 646	}
 647
 648	if (scsi_prot_sg_count(cmd))
 649		scsi_free_sgtable(cmd->prot_sdb);
 650}
 651
 652/*
 653 * Function:    scsi_release_buffers()
 654 *
 655 * Purpose:     Completion processing for block device I/O requests.
 656 *
 657 * Arguments:   cmd	- command that we are bailing.
 658 *
 659 * Lock status: Assumed that no lock is held upon entry.
 660 *
 661 * Returns:     Nothing
 662 *
 663 * Notes:       In the event that an upper level driver rejects a
 664 *		command, we must release resources allocated during
 665 *		the __init_io() function.  Primarily this would involve
 666 *		the scatter-gather table, and potentially any bounce
 667 *		buffers.
 668 */
 669void scsi_release_buffers(struct scsi_cmnd *cmd)
 670{
 671	__scsi_release_buffers(cmd, 1);
 672}
 673EXPORT_SYMBOL(scsi_release_buffers);
 674
 675static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
 676{
 677	int error = 0;
 678
 679	switch(host_byte(result)) {
 680	case DID_TRANSPORT_FAILFAST:
 681		error = -ENOLINK;
 682		break;
 683	case DID_TARGET_FAILURE:
 684		cmd->result |= (DID_OK << 16);
 685		error = -EREMOTEIO;
 686		break;
 687	case DID_NEXUS_FAILURE:
 688		cmd->result |= (DID_OK << 16);
 689		error = -EBADE;
 690		break;
 691	default:
 692		error = -EIO;
 693		break;
 694	}
 695
 696	return error;
 697}
 698
 699/*
 700 * Function:    scsi_io_completion()
 701 *
 702 * Purpose:     Completion processing for block device I/O requests.
 703 *
 704 * Arguments:   cmd   - command that is finished.
 705 *
 706 * Lock status: Assumed that no lock is held upon entry.
 707 *
 708 * Returns:     Nothing
 709 *
 710 * Notes:       This function is matched in terms of capabilities to
 711 *              the function that created the scatter-gather list.
 712 *              In other words, if there are no bounce buffers
 713 *              (the normal case for most drivers), we don't need
 714 *              the logic to deal with cleaning up afterwards.
 715 *
 716 *		We must call scsi_end_request().  This will finish off
 717 *		the specified number of sectors.  If we are done, the
 718 *		command block will be released and the queue function
 719 *		will be goosed.  If we are not done then we have to
 720 *		figure out what to do next:
 721 *
 722 *		a) We can call scsi_requeue_command().  The request
 723 *		   will be unprepared and put back on the queue.  Then
 724 *		   a new command will be created for it.  This should
 725 *		   be used if we made forward progress, or if we want
 726 *		   to switch from READ(10) to READ(6) for example.
 727 *
 728 *		b) We can call scsi_queue_insert().  The request will
 729 *		   be put back on the queue and retried using the same
 730 *		   command as before, possibly after a delay.
 731 *
 732 *		c) We can call blk_end_request() with -EIO to fail
 733 *		   the remainder of the request.
 734 */
 735void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 736{
 737	int result = cmd->result;
 738	struct request_queue *q = cmd->device->request_queue;
 739	struct request *req = cmd->request;
 740	int error = 0;
 741	struct scsi_sense_hdr sshdr;
 742	int sense_valid = 0;
 743	int sense_deferred = 0;
 744	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
 745	      ACTION_DELAYED_RETRY} action;
 746	char *description = NULL;
 747
 748	if (result) {
 749		sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
 750		if (sense_valid)
 751			sense_deferred = scsi_sense_is_deferred(&sshdr);
 752	}
 753
 754	if (req->cmd_type == REQ_TYPE_BLOCK_PC) { /* SG_IO ioctl from block level */
 755		req->errors = result;
 756		if (result) {
 757			if (sense_valid && req->sense) {
 758				/*
 759				 * SG_IO wants current and deferred errors
 760				 */
 761				int len = 8 + cmd->sense_buffer[7];
 762
 763				if (len > SCSI_SENSE_BUFFERSIZE)
 764					len = SCSI_SENSE_BUFFERSIZE;
 765				memcpy(req->sense, cmd->sense_buffer,  len);
 766				req->sense_len = len;
 767			}
 768			if (!sense_deferred)
 769				error = __scsi_error_from_host_byte(cmd, result);
 770		}
 771
 772		req->resid_len = scsi_get_resid(cmd);
 773
 774		if (scsi_bidi_cmnd(cmd)) {
 775			/*
 776			 * Bidi commands Must be complete as a whole,
 777			 * both sides at once.
 778			 */
 779			req->next_rq->resid_len = scsi_in(cmd)->resid;
 780
 781			scsi_release_buffers(cmd);
 782			blk_end_request_all(req, 0);
 783
 784			scsi_next_command(cmd);
 785			return;
 786		}
 787	}
 788
 789	/* no bidi support for !REQ_TYPE_BLOCK_PC yet */
 790	BUG_ON(blk_bidi_rq(req));
 791
 792	/*
 793	 * Next deal with any sectors which we were able to correctly
 794	 * handle.
 795	 */
 796	SCSI_LOG_HLCOMPLETE(1, printk("%u sectors total, "
 797				      "%d bytes done.\n",
 798				      blk_rq_sectors(req), good_bytes));
 799
 800	/*
 801	 * Recovered errors need reporting, but they're always treated
 802	 * as success, so fiddle the result code here.  For BLOCK_PC
 803	 * we already took a copy of the original into rq->errors which
 804	 * is what gets returned to the user
 805	 */
 806	if (sense_valid && (sshdr.sense_key == RECOVERED_ERROR)) {
 807		/* if ATA PASS-THROUGH INFORMATION AVAILABLE skip
 808		 * print since caller wants ATA registers. Only occurs on
 809		 * SCSI ATA PASS_THROUGH commands when CK_COND=1
 810		 */
 811		if ((sshdr.asc == 0x0) && (sshdr.ascq == 0x1d))
 812			;
 813		else if (!(req->cmd_flags & REQ_QUIET))
 814			scsi_print_sense("", cmd);
 815		result = 0;
 816		/* BLOCK_PC may have set error */
 817		error = 0;
 818	}
 819
 820	/*
 821	 * A number of bytes were successfully read.  If there
 822	 * are leftovers and there is some kind of error
 823	 * (result != 0), retry the rest.
 824	 */
 825	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
 826		return;
 827
 828	error = __scsi_error_from_host_byte(cmd, result);
 829
 830	if (host_byte(result) == DID_RESET) {
 831		/* Third party bus reset or reset for error recovery
 832		 * reasons.  Just retry the command and see what
 833		 * happens.
 834		 */
 835		action = ACTION_RETRY;
 836	} else if (sense_valid && !sense_deferred) {
 837		switch (sshdr.sense_key) {
 838		case UNIT_ATTENTION:
 839			if (cmd->device->removable) {
 840				/* Detected disc change.  Set a bit
 841				 * and quietly refuse further access.
 842				 */
 843				cmd->device->changed = 1;
 844				description = "Media Changed";
 845				action = ACTION_FAIL;
 846			} else {
 847				/* Must have been a power glitch, or a
 848				 * bus reset.  Could not have been a
 849				 * media change, so we just retry the
 850				 * command and see what happens.
 851				 */
 852				action = ACTION_RETRY;
 853			}
 854			break;
 855		case ILLEGAL_REQUEST:
 856			/* If we had an ILLEGAL REQUEST returned, then
 857			 * we may have performed an unsupported
 858			 * command.  The only thing this should be
 859			 * would be a ten byte read where only a six
 860			 * byte read was supported.  Also, on a system
 861			 * where READ CAPACITY failed, we may have
 862			 * read past the end of the disk.
 863			 */
 864			if ((cmd->device->use_10_for_rw &&
 865			    sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
 866			    (cmd->cmnd[0] == READ_10 ||
 867			     cmd->cmnd[0] == WRITE_10)) {
 868				/* This will issue a new 6-byte command. */
 869				cmd->device->use_10_for_rw = 0;
 870				action = ACTION_REPREP;
 871			} else if (sshdr.asc == 0x10) /* DIX */ {
 872				description = "Host Data Integrity Failure";
 873				action = ACTION_FAIL;
 874				error = -EILSEQ;
 875			/* INVALID COMMAND OPCODE or INVALID FIELD IN CDB */
 876			} else if ((sshdr.asc == 0x20 || sshdr.asc == 0x24) &&
 877				   (cmd->cmnd[0] == UNMAP ||
 878				    cmd->cmnd[0] == WRITE_SAME_16 ||
 879				    cmd->cmnd[0] == WRITE_SAME)) {
 880				description = "Discard failure";
 881				action = ACTION_FAIL;
 882			} else
 883				action = ACTION_FAIL;
 884			break;
 885		case ABORTED_COMMAND:
 886			action = ACTION_FAIL;
 887			if (sshdr.asc == 0x10) { /* DIF */
 888				description = "Target Data Integrity Failure";
 889				error = -EILSEQ;
 890			}
 891			break;
 892		case NOT_READY:
 893			/* If the device is in the process of becoming
 894			 * ready, or has a temporary blockage, retry.
 895			 */
 896			if (sshdr.asc == 0x04) {
 897				switch (sshdr.ascq) {
 898				case 0x01: /* becoming ready */
 899				case 0x04: /* format in progress */
 900				case 0x05: /* rebuild in progress */
 901				case 0x06: /* recalculation in progress */
 902				case 0x07: /* operation in progress */
 903				case 0x08: /* Long write in progress */
 904				case 0x09: /* self test in progress */
 905				case 0x14: /* space allocation in progress */
 906					action = ACTION_DELAYED_RETRY;
 907					break;
 908				default:
 909					description = "Device not ready";
 910					action = ACTION_FAIL;
 911					break;
 912				}
 913			} else {
 914				description = "Device not ready";
 915				action = ACTION_FAIL;
 916			}
 917			break;
 918		case VOLUME_OVERFLOW:
 919			/* See SSC3rXX or current. */
 920			action = ACTION_FAIL;
 921			break;
 922		default:
 923			description = "Unhandled sense code";
 924			action = ACTION_FAIL;
 925			break;
 926		}
 927	} else {
 928		description = "Unhandled error code";
 929		action = ACTION_FAIL;
 930	}
 931
 932	switch (action) {
 933	case ACTION_FAIL:
 934		/* Give up and fail the remainder of the request */
 935		scsi_release_buffers(cmd);
 936		if (!(req->cmd_flags & REQ_QUIET)) {
 937			if (description)
 938				scmd_printk(KERN_INFO, cmd, "%s\n",
 939					    description);
 940			scsi_print_result(cmd);
 941			if (driver_byte(result) & DRIVER_SENSE)
 942				scsi_print_sense("", cmd);
 943			scsi_print_command(cmd);
 944		}
 945		if (blk_end_request_err(req, error))
 946			scsi_requeue_command(q, cmd);
 947		else
 948			scsi_next_command(cmd);
 949		break;
 950	case ACTION_REPREP:
 951		/* Unprep the request and put it back at the head of the queue.
 952		 * A new command will be prepared and issued.
 953		 */
 954		scsi_release_buffers(cmd);
 955		scsi_requeue_command(q, cmd);
 956		break;
 957	case ACTION_RETRY:
 958		/* Retry the same command immediately */
 959		__scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, 0);
 960		break;
 961	case ACTION_DELAYED_RETRY:
 962		/* Retry the same command after a delay */
 963		__scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, 0);
 964		break;
 965	}
 966}
 967
 968static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
 969			     gfp_t gfp_mask)
 970{
 971	int count;
 972
 973	/*
 974	 * If sg table allocation fails, requeue request later.
 975	 */
 976	if (unlikely(scsi_alloc_sgtable(sdb, req->nr_phys_segments,
 977					gfp_mask))) {
 978		return BLKPREP_DEFER;
 979	}
 980
 981	req->buffer = NULL;
 982
 983	/* 
 984	 * Next, walk the list, and fill in the addresses and sizes of
 985	 * each segment.
 986	 */
 987	count = blk_rq_map_sg(req->q, req, sdb->table.sgl);
 988	BUG_ON(count > sdb->table.nents);
 989	sdb->table.nents = count;
 990	sdb->length = blk_rq_bytes(req);
 991	return BLKPREP_OK;
 992}
 993
 994/*
 995 * Function:    scsi_init_io()
 996 *
 997 * Purpose:     SCSI I/O initialize function.
 998 *
 999 * Arguments:   cmd   - Command descriptor we wish to initialize
1000 *
1001 * Returns:     0 on success
1002 *		BLKPREP_DEFER if the failure is retryable
1003 *		BLKPREP_KILL if the failure is fatal
1004 */
1005int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
1006{
1007	struct request *rq = cmd->request;
1008
1009	int error = scsi_init_sgtable(rq, &cmd->sdb, gfp_mask);
1010	if (error)
1011		goto err_exit;
1012
1013	if (blk_bidi_rq(rq)) {
1014		struct scsi_data_buffer *bidi_sdb = kmem_cache_zalloc(
1015			scsi_sdb_cache, GFP_ATOMIC);
1016		if (!bidi_sdb) {
1017			error = BLKPREP_DEFER;
1018			goto err_exit;
1019		}
1020
1021		rq->next_rq->special = bidi_sdb;
1022		error = scsi_init_sgtable(rq->next_rq, bidi_sdb, GFP_ATOMIC);
1023		if (error)
1024			goto err_exit;
1025	}
1026
1027	if (blk_integrity_rq(rq)) {
1028		struct scsi_data_buffer *prot_sdb = cmd->prot_sdb;
1029		int ivecs, count;
1030
1031		BUG_ON(prot_sdb == NULL);
1032		ivecs = blk_rq_count_integrity_sg(rq->q, rq->bio);
1033
1034		if (scsi_alloc_sgtable(prot_sdb, ivecs, gfp_mask)) {
1035			error = BLKPREP_DEFER;
1036			goto err_exit;
1037		}
1038
1039		count = blk_rq_map_integrity_sg(rq->q, rq->bio,
1040						prot_sdb->table.sgl);
1041		BUG_ON(unlikely(count > ivecs));
1042		BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
1043
1044		cmd->prot_sdb = prot_sdb;
1045		cmd->prot_sdb->table.nents = count;
1046	}
1047
1048	return BLKPREP_OK ;
1049
1050err_exit:
1051	scsi_release_buffers(cmd);
1052	cmd->request->special = NULL;
1053	scsi_put_command(cmd);
1054	return error;
1055}
1056EXPORT_SYMBOL(scsi_init_io);
1057
1058static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
1059		struct request *req)
1060{
1061	struct scsi_cmnd *cmd;
1062
1063	if (!req->special) {
1064		cmd = scsi_get_command(sdev, GFP_ATOMIC);
1065		if (unlikely(!cmd))
1066			return NULL;
1067		req->special = cmd;
1068	} else {
1069		cmd = req->special;
1070	}
1071
1072	/* pull a tag out of the request if we have one */
1073	cmd->tag = req->tag;
1074	cmd->request = req;
1075
1076	cmd->cmnd = req->cmd;
1077	cmd->prot_op = SCSI_PROT_NORMAL;
1078
1079	return cmd;
1080}
1081
1082int scsi_setup_blk_pc_cmnd(struct scsi_device *sdev, struct request *req)
1083{
1084	struct scsi_cmnd *cmd;
1085	int ret = scsi_prep_state_check(sdev, req);
1086
1087	if (ret != BLKPREP_OK)
1088		return ret;
1089
1090	cmd = scsi_get_cmd_from_req(sdev, req);
1091	if (unlikely(!cmd))
1092		return BLKPREP_DEFER;
1093
1094	/*
1095	 * BLOCK_PC requests may transfer data, in which case they must
1096	 * a bio attached to them.  Or they might contain a SCSI command
1097	 * that does not transfer data, in which case they may optionally
1098	 * submit a request without an attached bio.
1099	 */
1100	if (req->bio) {
1101		int ret;
1102
1103		BUG_ON(!req->nr_phys_segments);
1104
1105		ret = scsi_init_io(cmd, GFP_ATOMIC);
1106		if (unlikely(ret))
1107			return ret;
1108	} else {
1109		BUG_ON(blk_rq_bytes(req));
1110
1111		memset(&cmd->sdb, 0, sizeof(cmd->sdb));
1112		req->buffer = NULL;
1113	}
1114
1115	cmd->cmd_len = req->cmd_len;
1116	if (!blk_rq_bytes(req))
1117		cmd->sc_data_direction = DMA_NONE;
1118	else if (rq_data_dir(req) == WRITE)
1119		cmd->sc_data_direction = DMA_TO_DEVICE;
1120	else
1121		cmd->sc_data_direction = DMA_FROM_DEVICE;
1122	
1123	cmd->transfersize = blk_rq_bytes(req);
1124	cmd->allowed = req->retries;
1125	return BLKPREP_OK;
1126}
1127EXPORT_SYMBOL(scsi_setup_blk_pc_cmnd);
1128
1129/*
1130 * Setup a REQ_TYPE_FS command.  These are simple read/write request
1131 * from filesystems that still need to be translated to SCSI CDBs from
1132 * the ULD.
1133 */
1134int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
1135{
1136	struct scsi_cmnd *cmd;
1137	int ret = scsi_prep_state_check(sdev, req);
1138
1139	if (ret != BLKPREP_OK)
1140		return ret;
1141
1142	if (unlikely(sdev->scsi_dh_data && sdev->scsi_dh_data->scsi_dh
1143			 && sdev->scsi_dh_data->scsi_dh->prep_fn)) {
1144		ret = sdev->scsi_dh_data->scsi_dh->prep_fn(sdev, req);
1145		if (ret != BLKPREP_OK)
1146			return ret;
1147	}
1148
1149	/*
1150	 * Filesystem requests must transfer data.
1151	 */
1152	BUG_ON(!req->nr_phys_segments);
1153
1154	cmd = scsi_get_cmd_from_req(sdev, req);
1155	if (unlikely(!cmd))
1156		return BLKPREP_DEFER;
1157
1158	memset(cmd->cmnd, 0, BLK_MAX_CDB);
1159	return scsi_init_io(cmd, GFP_ATOMIC);
1160}
1161EXPORT_SYMBOL(scsi_setup_fs_cmnd);
1162
1163int scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
1164{
1165	int ret = BLKPREP_OK;
1166
1167	/*
1168	 * If the device is not in running state we will reject some
1169	 * or all commands.
1170	 */
1171	if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
1172		switch (sdev->sdev_state) {
1173		case SDEV_OFFLINE:
1174			/*
1175			 * If the device is offline we refuse to process any
1176			 * commands.  The device must be brought online
1177			 * before trying any recovery commands.
1178			 */
1179			sdev_printk(KERN_ERR, sdev,
1180				    "rejecting I/O to offline device\n");
1181			ret = BLKPREP_KILL;
1182			break;
1183		case SDEV_DEL:
1184			/*
1185			 * If the device is fully deleted, we refuse to
1186			 * process any commands as well.
1187			 */
1188			sdev_printk(KERN_ERR, sdev,
1189				    "rejecting I/O to dead device\n");
1190			ret = BLKPREP_KILL;
1191			break;
1192		case SDEV_QUIESCE:
1193		case SDEV_BLOCK:
1194		case SDEV_CREATED_BLOCK:
1195			/*
1196			 * If the devices is blocked we defer normal commands.
1197			 */
1198			if (!(req->cmd_flags & REQ_PREEMPT))
1199				ret = BLKPREP_DEFER;
1200			break;
1201		default:
1202			/*
1203			 * For any other not fully online state we only allow
1204			 * special commands.  In particular any user initiated
1205			 * command is not allowed.
1206			 */
1207			if (!(req->cmd_flags & REQ_PREEMPT))
1208				ret = BLKPREP_KILL;
1209			break;
1210		}
1211	}
1212	return ret;
1213}
1214EXPORT_SYMBOL(scsi_prep_state_check);
1215
1216int scsi_prep_return(struct request_queue *q, struct request *req, int ret)
1217{
1218	struct scsi_device *sdev = q->queuedata;
1219
1220	switch (ret) {
1221	case BLKPREP_KILL:
1222		req->errors = DID_NO_CONNECT << 16;
1223		/* release the command and kill it */
1224		if (req->special) {
1225			struct scsi_cmnd *cmd = req->special;
1226			scsi_release_buffers(cmd);
1227			scsi_put_command(cmd);
1228			req->special = NULL;
1229		}
1230		break;
1231	case BLKPREP_DEFER:
1232		/*
1233		 * If we defer, the blk_peek_request() returns NULL, but the
1234		 * queue must be restarted, so we schedule a callback to happen
1235		 * shortly.
1236		 */
1237		if (sdev->device_busy == 0)
1238			blk_delay_queue(q, SCSI_QUEUE_DELAY);
1239		break;
1240	default:
1241		req->cmd_flags |= REQ_DONTPREP;
1242	}
1243
1244	return ret;
1245}
1246EXPORT_SYMBOL(scsi_prep_return);
1247
1248int scsi_prep_fn(struct request_queue *q, struct request *req)
1249{
1250	struct scsi_device *sdev = q->queuedata;
1251	int ret = BLKPREP_KILL;
1252
1253	if (req->cmd_type == REQ_TYPE_BLOCK_PC)
1254		ret = scsi_setup_blk_pc_cmnd(sdev, req);
1255	return scsi_prep_return(q, req, ret);
1256}
1257EXPORT_SYMBOL(scsi_prep_fn);
1258
1259/*
1260 * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
1261 * return 0.
1262 *
1263 * Called with the queue_lock held.
1264 */
1265static inline int scsi_dev_queue_ready(struct request_queue *q,
1266				  struct scsi_device *sdev)
1267{
1268	if (sdev->device_busy == 0 && sdev->device_blocked) {
1269		/*
1270		 * unblock after device_blocked iterates to zero
1271		 */
1272		if (--sdev->device_blocked == 0) {
1273			SCSI_LOG_MLQUEUE(3,
1274				   sdev_printk(KERN_INFO, sdev,
1275				   "unblocking device at zero depth\n"));
1276		} else {
1277			blk_delay_queue(q, SCSI_QUEUE_DELAY);
1278			return 0;
1279		}
1280	}
1281	if (scsi_device_is_busy(sdev))
1282		return 0;
1283
1284	return 1;
1285}
1286
1287
1288/*
1289 * scsi_target_queue_ready: checks if there we can send commands to target
1290 * @sdev: scsi device on starget to check.
1291 *
1292 * Called with the host lock held.
1293 */
1294static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
1295					   struct scsi_device *sdev)
1296{
1297	struct scsi_target *starget = scsi_target(sdev);
1298
1299	if (starget->single_lun) {
1300		if (starget->starget_sdev_user &&
1301		    starget->starget_sdev_user != sdev)
1302			return 0;
1303		starget->starget_sdev_user = sdev;
1304	}
1305
1306	if (starget->target_busy == 0 && starget->target_blocked) {
1307		/*
1308		 * unblock after target_blocked iterates to zero
1309		 */
1310		if (--starget->target_blocked == 0) {
1311			SCSI_LOG_MLQUEUE(3, starget_printk(KERN_INFO, starget,
1312					 "unblocking target at zero depth\n"));
1313		} else
1314			return 0;
1315	}
1316
1317	if (scsi_target_is_busy(starget)) {
1318		if (list_empty(&sdev->starved_entry))
1319			list_add_tail(&sdev->starved_entry,
1320				      &shost->starved_list);
1321		return 0;
1322	}
1323
1324	/* We're OK to process the command, so we can't be starved */
1325	if (!list_empty(&sdev->starved_entry))
1326		list_del_init(&sdev->starved_entry);
1327	return 1;
1328}
1329
1330/*
1331 * scsi_host_queue_ready: if we can send requests to shost, return 1 else
1332 * return 0. We must end up running the queue again whenever 0 is
1333 * returned, else IO can hang.
1334 *
1335 * Called with host_lock held.
1336 */
1337static inline int scsi_host_queue_ready(struct request_queue *q,
1338				   struct Scsi_Host *shost,
1339				   struct scsi_device *sdev)
1340{
1341	if (scsi_host_in_recovery(shost))
1342		return 0;
1343	if (shost->host_busy == 0 && shost->host_blocked) {
1344		/*
1345		 * unblock after host_blocked iterates to zero
1346		 */
1347		if (--shost->host_blocked == 0) {
1348			SCSI_LOG_MLQUEUE(3,
1349				printk("scsi%d unblocking host at zero depth\n",
1350					shost->host_no));
1351		} else {
1352			return 0;
1353		}
1354	}
1355	if (scsi_host_is_busy(shost)) {
1356		if (list_empty(&sdev->starved_entry))
1357			list_add_tail(&sdev->starved_entry, &shost->starved_list);
1358		return 0;
1359	}
1360
1361	/* We're OK to process the command, so we can't be starved */
1362	if (!list_empty(&sdev->starved_entry))
1363		list_del_init(&sdev->starved_entry);
1364
1365	return 1;
1366}
1367
1368/*
1369 * Busy state exporting function for request stacking drivers.
1370 *
1371 * For efficiency, no lock is taken to check the busy state of
1372 * shost/starget/sdev, since the returned value is not guaranteed and
1373 * may be changed after request stacking drivers call the function,
1374 * regardless of taking lock or not.
1375 *
1376 * When scsi can't dispatch I/Os anymore and needs to kill I/Os
1377 * (e.g. !sdev), scsi needs to return 'not busy'.
1378 * Otherwise, request stacking drivers may hold requests forever.
1379 */
1380static int scsi_lld_busy(struct request_queue *q)
1381{
1382	struct scsi_device *sdev = q->queuedata;
1383	struct Scsi_Host *shost;
1384	struct scsi_target *starget;
1385
1386	if (!sdev)
1387		return 0;
1388
1389	shost = sdev->host;
1390	starget = scsi_target(sdev);
1391
1392	if (scsi_host_in_recovery(shost) || scsi_host_is_busy(shost) ||
1393	    scsi_target_is_busy(starget) || scsi_device_is_busy(sdev))
1394		return 1;
1395
1396	return 0;
1397}
1398
1399/*
1400 * Kill a request for a dead device
1401 */
1402static void scsi_kill_request(struct request *req, struct request_queue *q)
1403{
1404	struct scsi_cmnd *cmd = req->special;
1405	struct scsi_device *sdev;
1406	struct scsi_target *starget;
1407	struct Scsi_Host *shost;
1408
1409	blk_start_request(req);
1410
1411	sdev = cmd->device;
1412	starget = scsi_target(sdev);
1413	shost = sdev->host;
1414	scsi_init_cmd_errh(cmd);
1415	cmd->result = DID_NO_CONNECT << 16;
1416	atomic_inc(&cmd->device->iorequest_cnt);
1417
1418	/*
1419	 * SCSI request completion path will do scsi_device_unbusy(),
1420	 * bump busy counts.  To bump the counters, we need to dance
1421	 * with the locks as normal issue path does.
1422	 */
1423	sdev->device_busy++;
1424	spin_unlock(sdev->request_queue->queue_lock);
1425	spin_lock(shost->host_lock);
1426	shost->host_busy++;
1427	starget->target_busy++;
1428	spin_unlock(shost->host_lock);
1429	spin_lock(sdev->request_queue->queue_lock);
1430
1431	blk_complete_request(req);
1432}
1433
1434static void scsi_softirq_done(struct request *rq)
1435{
1436	struct scsi_cmnd *cmd = rq->special;
1437	unsigned long wait_for = (cmd->allowed + 1) * rq->timeout;
1438	int disposition;
1439
1440	INIT_LIST_HEAD(&cmd->eh_entry);
1441
1442	atomic_inc(&cmd->device->iodone_cnt);
1443	if (cmd->result)
1444		atomic_inc(&cmd->device->ioerr_cnt);
1445
1446	disposition = scsi_decide_disposition(cmd);
1447	if (disposition != SUCCESS &&
1448	    time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
1449		sdev_printk(KERN_ERR, cmd->device,
1450			    "timing out command, waited %lus\n",
1451			    wait_for/HZ);
1452		disposition = SUCCESS;
1453	}
1454			
1455	scsi_log_completion(cmd, disposition);
1456
1457	switch (disposition) {
1458		case SUCCESS:
1459			scsi_finish_command(cmd);
1460			break;
1461		case NEEDS_RETRY:
1462			scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY);
1463			break;
1464		case ADD_TO_MLQUEUE:
1465			scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
1466			break;
1467		default:
1468			if (!scsi_eh_scmd_add(cmd, 0))
1469				scsi_finish_command(cmd);
1470	}
1471}
1472
1473/*
1474 * Function:    scsi_request_fn()
1475 *
1476 * Purpose:     Main strategy routine for SCSI.
1477 *
1478 * Arguments:   q       - Pointer to actual queue.
1479 *
1480 * Returns:     Nothing
1481 *
1482 * Lock status: IO request lock assumed to be held when called.
1483 */
1484static void scsi_request_fn(struct request_queue *q)
1485{
1486	struct scsi_device *sdev = q->queuedata;
1487	struct Scsi_Host *shost;
1488	struct scsi_cmnd *cmd;
1489	struct request *req;
1490
1491	if (!sdev) {
1492		printk("scsi: killing requests for dead queue\n");
1493		while ((req = blk_peek_request(q)) != NULL)
1494			scsi_kill_request(req, q);
1495		return;
1496	}
1497
1498	if(!get_device(&sdev->sdev_gendev))
1499		/* We must be tearing the block queue down already */
1500		return;
1501
1502	/*
1503	 * To start with, we keep looping until the queue is empty, or until
1504	 * the host is no longer able to accept any more requests.
1505	 */
1506	shost = sdev->host;
1507	for (;;) {
1508		int rtn;
1509		/*
1510		 * get next queueable request.  We do this early to make sure
1511		 * that the request is fully prepared even if we cannot 
1512		 * accept it.
1513		 */
1514		req = blk_peek_request(q);
1515		if (!req || !scsi_dev_queue_ready(q, sdev))
1516			break;
1517
1518		if (unlikely(!scsi_device_online(sdev))) {
1519			sdev_printk(KERN_ERR, sdev,
1520				    "rejecting I/O to offline device\n");
1521			scsi_kill_request(req, q);
1522			continue;
1523		}
1524
1525
1526		/*
1527		 * Remove the request from the request list.
1528		 */
1529		if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
1530			blk_start_request(req);
1531		sdev->device_busy++;
1532
1533		spin_unlock(q->queue_lock);
1534		cmd = req->special;
1535		if (unlikely(cmd == NULL)) {
1536			printk(KERN_CRIT "impossible request in %s.\n"
1537					 "please mail a stack trace to "
1538					 "linux-scsi@vger.kernel.org\n",
1539					 __func__);
1540			blk_dump_rq_flags(req, "foo");
1541			BUG();
1542		}
1543		spin_lock(shost->host_lock);
1544
1545		/*
1546		 * We hit this when the driver is using a host wide
1547		 * tag map. For device level tag maps the queue_depth check
1548		 * in the device ready fn would prevent us from trying
1549		 * to allocate a tag. Since the map is a shared host resource
1550		 * we add the dev to the starved list so it eventually gets
1551		 * a run when a tag is freed.
1552		 */
1553		if (blk_queue_tagged(q) && !blk_rq_tagged(req)) {
1554			if (list_empty(&sdev->starved_entry))
1555				list_add_tail(&sdev->starved_entry,
1556					      &shost->starved_list);
1557			goto not_ready;
1558		}
1559
1560		if (!scsi_target_queue_ready(shost, sdev))
1561			goto not_ready;
1562
1563		if (!scsi_host_queue_ready(q, shost, sdev))
1564			goto not_ready;
1565
1566		scsi_target(sdev)->target_busy++;
1567		shost->host_busy++;
1568
1569		/*
1570		 * XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
1571		 *		take the lock again.
1572		 */
1573		spin_unlock_irq(shost->host_lock);
1574
1575		/*
1576		 * Finally, initialize any error handling parameters, and set up
1577		 * the timers for timeouts.
1578		 */
1579		scsi_init_cmd_errh(cmd);
1580
1581		/*
1582		 * Dispatch the command to the low-level driver.
1583		 */
1584		rtn = scsi_dispatch_cmd(cmd);
1585		spin_lock_irq(q->queue_lock);
1586		if (rtn)
1587			goto out_delay;
1588	}
1589
1590	goto out;
1591
1592 not_ready:
1593	spin_unlock_irq(shost->host_lock);
1594
1595	/*
1596	 * lock q, handle tag, requeue req, and decrement device_busy. We
1597	 * must return with queue_lock held.
1598	 *
1599	 * Decrementing device_busy without checking it is OK, as all such
1600	 * cases (host limits or settings) should run the queue at some
1601	 * later time.
1602	 */
1603	spin_lock_irq(q->queue_lock);
1604	blk_requeue_request(q, req);
1605	sdev->device_busy--;
1606out_delay:
1607	if (sdev->device_busy == 0)
1608		blk_delay_queue(q, SCSI_QUEUE_DELAY);
1609out:
1610	/* must be careful here...if we trigger the ->remove() function
1611	 * we cannot be holding the q lock */
1612	spin_unlock_irq(q->queue_lock);
1613	put_device(&sdev->sdev_gendev);
1614	spin_lock_irq(q->queue_lock);
1615}
1616
1617u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
1618{
1619	struct device *host_dev;
1620	u64 bounce_limit = 0xffffffff;
1621
1622	if (shost->unchecked_isa_dma)
1623		return BLK_BOUNCE_ISA;
1624	/*
1625	 * Platforms with virtual-DMA translation
1626	 * hardware have no practical limit.
1627	 */
1628	if (!PCI_DMA_BUS_IS_PHYS)
1629		return BLK_BOUNCE_ANY;
1630
1631	host_dev = scsi_get_device(shost);
1632	if (host_dev && host_dev->dma_mask)
1633		bounce_limit = *host_dev->dma_mask;
1634
1635	return bounce_limit;
1636}
1637EXPORT_SYMBOL(scsi_calculate_bounce_limit);
1638
1639struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
1640					 request_fn_proc *request_fn)
1641{
1642	struct request_queue *q;
1643	struct device *dev = shost->shost_gendev.parent;
1644
1645	q = blk_init_queue(request_fn, NULL);
1646	if (!q)
1647		return NULL;
1648
1649	/*
1650	 * this limit is imposed by hardware restrictions
1651	 */
1652	blk_queue_max_segments(q, min_t(unsigned short, shost->sg_tablesize,
1653					SCSI_MAX_SG_CHAIN_SEGMENTS));
1654
1655	if (scsi_host_prot_dma(shost)) {
1656		shost->sg_prot_tablesize =
1657			min_not_zero(shost->sg_prot_tablesize,
1658				     (unsigned short)SCSI_MAX_PROT_SG_SEGMENTS);
1659		BUG_ON(shost->sg_prot_tablesize < shost->sg_tablesize);
1660		blk_queue_max_integrity_segments(q, shost->sg_prot_tablesize);
1661	}
1662
1663	blk_queue_max_hw_sectors(q, shost->max_sectors);
1664	blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
1665	blk_queue_segment_boundary(q, shost->dma_boundary);
1666	dma_set_seg_boundary(dev, shost->dma_boundary);
1667
1668	blk_queue_max_segment_size(q, dma_get_max_seg_size(dev));
1669
1670	if (!shost->use_clustering)
1671		q->limits.cluster = 0;
1672
1673	/*
1674	 * set a reasonable default alignment on word boundaries: the
1675	 * host and device may alter it using
1676	 * blk_queue_update_dma_alignment() later.
1677	 */
1678	blk_queue_dma_alignment(q, 0x03);
1679
1680	return q;
1681}
1682EXPORT_SYMBOL(__scsi_alloc_queue);
1683
1684struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
1685{
1686	struct request_queue *q;
1687
1688	q = __scsi_alloc_queue(sdev->host, scsi_request_fn);
1689	if (!q)
1690		return NULL;
1691
1692	blk_queue_prep_rq(q, scsi_prep_fn);
1693	blk_queue_softirq_done(q, scsi_softirq_done);
1694	blk_queue_rq_timed_out(q, scsi_times_out);
1695	blk_queue_lld_busy(q, scsi_lld_busy);
1696	return q;
1697}
1698
1699void scsi_free_queue(struct request_queue *q)
1700{
1701	blk_cleanup_queue(q);
1702}
1703
1704/*
1705 * Function:    scsi_block_requests()
1706 *
1707 * Purpose:     Utility function used by low-level drivers to prevent further
1708 *		commands from being queued to the device.
1709 *
1710 * Arguments:   shost       - Host in question
1711 *
1712 * Returns:     Nothing
1713 *
1714 * Lock status: No locks are assumed held.
1715 *
1716 * Notes:       There is no timer nor any other means by which the requests
1717 *		get unblocked other than the low-level driver calling
1718 *		scsi_unblock_requests().
1719 */
1720void scsi_block_requests(struct Scsi_Host *shost)
1721{
1722	shost->host_self_blocked = 1;
1723}
1724EXPORT_SYMBOL(scsi_block_requests);
1725
1726/*
1727 * Function:    scsi_unblock_requests()
1728 *
1729 * Purpose:     Utility function used by low-level drivers to allow further
1730 *		commands from being queued to the device.
1731 *
1732 * Arguments:   shost       - Host in question
1733 *
1734 * Returns:     Nothing
1735 *
1736 * Lock status: No locks are assumed held.
1737 *
1738 * Notes:       There is no timer nor any other means by which the requests
1739 *		get unblocked other than the low-level driver calling
1740 *		scsi_unblock_requests().
1741 *
1742 *		This is done as an API function so that changes to the
1743 *		internals of the scsi mid-layer won't require wholesale
1744 *		changes to drivers that use this feature.
1745 */
1746void scsi_unblock_requests(struct Scsi_Host *shost)
1747{
1748	shost->host_self_blocked = 0;
1749	scsi_run_host_queues(shost);
1750}
1751EXPORT_SYMBOL(scsi_unblock_requests);
1752
1753int __init scsi_init_queue(void)
1754{
1755	int i;
1756
1757	scsi_sdb_cache = kmem_cache_create("scsi_data_buffer",
1758					   sizeof(struct scsi_data_buffer),
1759					   0, 0, NULL);
1760	if (!scsi_sdb_cache) {
1761		printk(KERN_ERR "SCSI: can't init scsi sdb cache\n");
1762		return -ENOMEM;
1763	}
1764
1765	for (i = 0; i < SG_MEMPOOL_NR; i++) {
1766		struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1767		int size = sgp->size * sizeof(struct scatterlist);
1768
1769		sgp->slab = kmem_cache_create(sgp->name, size, 0,
1770				SLAB_HWCACHE_ALIGN, NULL);
1771		if (!sgp->slab) {
1772			printk(KERN_ERR "SCSI: can't init sg slab %s\n",
1773					sgp->name);
1774			goto cleanup_sdb;
1775		}
1776
1777		sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
1778						     sgp->slab);
1779		if (!sgp->pool) {
1780			printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
1781					sgp->name);
1782			goto cleanup_sdb;
1783		}
1784	}
1785
1786	return 0;
1787
1788cleanup_sdb:
1789	for (i = 0; i < SG_MEMPOOL_NR; i++) {
1790		struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1791		if (sgp->pool)
1792			mempool_destroy(sgp->pool);
1793		if (sgp->slab)
1794			kmem_cache_destroy(sgp->slab);
1795	}
1796	kmem_cache_destroy(scsi_sdb_cache);
1797
1798	return -ENOMEM;
1799}
1800
1801void scsi_exit_queue(void)
1802{
1803	int i;
1804
1805	kmem_cache_destroy(scsi_sdb_cache);
1806
1807	for (i = 0; i < SG_MEMPOOL_NR; i++) {
1808		struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
1809		mempool_destroy(sgp->pool);
1810		kmem_cache_destroy(sgp->slab);
1811	}
1812}
1813
1814/**
1815 *	scsi_mode_select - issue a mode select
1816 *	@sdev:	SCSI device to be queried
1817 *	@pf:	Page format bit (1 == standard, 0 == vendor specific)
1818 *	@sp:	Save page bit (0 == don't save, 1 == save)
1819 *	@modepage: mode page being requested
1820 *	@buffer: request buffer (may not be smaller than eight bytes)
1821 *	@len:	length of request buffer.
1822 *	@timeout: command timeout
1823 *	@retries: number of retries before failing
1824 *	@data: returns a structure abstracting the mode header data
1825 *	@sshdr: place to put sense data (or NULL if no sense to be collected).
1826 *		must be SCSI_SENSE_BUFFERSIZE big.
1827 *
1828 *	Returns zero if successful; negative error number or scsi
1829 *	status on error
1830 *
1831 */
1832int
1833scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
1834		 unsigned char *buffer, int len, int timeout, int retries,
1835		 struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1836{
1837	unsigned char cmd[10];
1838	unsigned char *real_buffer;
1839	int ret;
1840
1841	memset(cmd, 0, sizeof(cmd));
1842	cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
1843
1844	if (sdev->use_10_for_ms) {
1845		if (len > 65535)
1846			return -EINVAL;
1847		real_buffer = kmalloc(8 + len, GFP_KERNEL);
1848		if (!real_buffer)
1849			return -ENOMEM;
1850		memcpy(real_buffer + 8, buffer, len);
1851		len += 8;
1852		real_buffer[0] = 0;
1853		real_buffer[1] = 0;
1854		real_buffer[2] = data->medium_type;
1855		real_buffer[3] = data->device_specific;
1856		real_buffer[4] = data->longlba ? 0x01 : 0;
1857		real_buffer[5] = 0;
1858		real_buffer[6] = data->block_descriptor_length >> 8;
1859		real_buffer[7] = data->block_descriptor_length;
1860
1861		cmd[0] = MODE_SELECT_10;
1862		cmd[7] = len >> 8;
1863		cmd[8] = len;
1864	} else {
1865		if (len > 255 || data->block_descriptor_length > 255 ||
1866		    data->longlba)
1867			return -EINVAL;
1868
1869		real_buffer = kmalloc(4 + len, GFP_KERNEL);
1870		if (!real_buffer)
1871			return -ENOMEM;
1872		memcpy(real_buffer + 4, buffer, len);
1873		len += 4;
1874		real_buffer[0] = 0;
1875		real_buffer[1] = data->medium_type;
1876		real_buffer[2] = data->device_specific;
1877		real_buffer[3] = data->block_descriptor_length;
1878		
1879
1880		cmd[0] = MODE_SELECT;
1881		cmd[4] = len;
1882	}
1883
1884	ret = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, real_buffer, len,
1885			       sshdr, timeout, retries, NULL);
1886	kfree(real_buffer);
1887	return ret;
1888}
1889EXPORT_SYMBOL_GPL(scsi_mode_select);
1890
1891/**
1892 *	scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
1893 *	@sdev:	SCSI device to be queried
1894 *	@dbd:	set if mode sense will allow block descriptors to be returned
1895 *	@modepage: mode page being requested
1896 *	@buffer: request buffer (may not be smaller than eight bytes)
1897 *	@len:	length of request buffer.
1898 *	@timeout: command timeout
1899 *	@retries: number of retries before failing
1900 *	@data: returns a structure abstracting the mode header data
1901 *	@sshdr: place to put sense data (or NULL if no sense to be collected).
1902 *		must be SCSI_SENSE_BUFFERSIZE big.
1903 *
1904 *	Returns zero if unsuccessful, or the header offset (either 4
1905 *	or 8 depending on whether a six or ten byte command was
1906 *	issued) if successful.
1907 */
1908int
1909scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
1910		  unsigned char *buffer, int len, int timeout, int retries,
1911		  struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
1912{
1913	unsigned char cmd[12];
1914	int use_10_for_ms;
1915	int header_length;
1916	int result;
1917	struct scsi_sense_hdr my_sshdr;
1918
1919	memset(data, 0, sizeof(*data));
1920	memset(&cmd[0], 0, 12);
1921	cmd[1] = dbd & 0x18;	/* allows DBD and LLBA bits */
1922	cmd[2] = modepage;
1923
1924	/* caller might not be interested in sense, but we need it */
1925	if (!sshdr)
1926		sshdr = &my_sshdr;
1927
1928 retry:
1929	use_10_for_ms = sdev->use_10_for_ms;
1930
1931	if (use_10_for_ms) {
1932		if (len < 8)
1933			len = 8;
1934
1935		cmd[0] = MODE_SENSE_10;
1936		cmd[8] = len;
1937		header_length = 8;
1938	} else {
1939		if (len < 4)
1940			len = 4;
1941
1942		cmd[0] = MODE_SENSE;
1943		cmd[4] = len;
1944		header_length = 4;
1945	}
1946
1947	memset(buffer, 0, len);
1948
1949	result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
1950				  sshdr, timeout, retries, NULL);
1951
1952	/* This code looks awful: what it's doing is making sure an
1953	 * ILLEGAL REQUEST sense return identifies the actual command
1954	 * byte as the problem.  MODE_SENSE commands can return
1955	 * ILLEGAL REQUEST if the code page isn't supported */
1956
1957	if (use_10_for_ms && !scsi_status_is_good(result) &&
1958	    (driver_byte(result) & DRIVER_SENSE)) {
1959		if (scsi_sense_valid(sshdr)) {
1960			if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
1961			    (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
1962				/* 
1963				 * Invalid command operation code
1964				 */
1965				sdev->use_10_for_ms = 0;
1966				goto retry;
1967			}
1968		}
1969	}
1970
1971	if(scsi_status_is_good(result)) {
1972		if (unlikely(buffer[0] == 0x86 && buffer[1] == 0x0b &&
1973			     (modepage == 6 || modepage == 8))) {
1974			/* Initio breakage? */
1975			header_length = 0;
1976			data->length = 13;
1977			data->medium_type = 0;
1978			data->device_specific = 0;
1979			data->longlba = 0;
1980			data->block_descriptor_length = 0;
1981		} else if(use_10_for_ms) {
1982			data->length = buffer[0]*256 + buffer[1] + 2;
1983			data->medium_type = buffer[2];
1984			data->device_specific = buffer[3];
1985			data->longlba = buffer[4] & 0x01;
1986			data->block_descriptor_length = buffer[6]*256
1987				+ buffer[7];
1988		} else {
1989			data->length = buffer[0] + 1;
1990			data->medium_type = buffer[1];
1991			data->device_specific = buffer[2];
1992			data->block_descriptor_length = buffer[3];
1993		}
1994		data->header_length = header_length;
1995	}
1996
1997	return result;
1998}
1999EXPORT_SYMBOL(scsi_mode_sense);
2000
2001/**
2002 *	scsi_test_unit_ready - test if unit is ready
2003 *	@sdev:	scsi device to change the state of.
2004 *	@timeout: command timeout
2005 *	@retries: number of retries before failing
2006 *	@sshdr_external: Optional pointer to struct scsi_sense_hdr for
2007 *		returning sense. Make sure that this is cleared before passing
2008 *		in.
2009 *
2010 *	Returns zero if unsuccessful or an error if TUR failed.  For
2011 *	removable media, UNIT_ATTENTION sets ->changed flag.
2012 **/
2013int
2014scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries,
2015		     struct scsi_sense_hdr *sshdr_external)
2016{
2017	char cmd[] = {
2018		TEST_UNIT_READY, 0, 0, 0, 0, 0,
2019	};
2020	struct scsi_sense_hdr *sshdr;
2021	int result;
2022
2023	if (!sshdr_external)
2024		sshdr = kzalloc(sizeof(*sshdr), GFP_KERNEL);
2025	else
2026		sshdr = sshdr_external;
2027
2028	/* try to eat the UNIT_ATTENTION if there are enough retries */
2029	do {
2030		result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
2031					  timeout, retries, NULL);
2032		if (sdev->removable && scsi_sense_valid(sshdr) &&
2033		    sshdr->sense_key == UNIT_ATTENTION)
2034			sdev->changed = 1;
2035	} while (scsi_sense_valid(sshdr) &&
2036		 sshdr->sense_key == UNIT_ATTENTION && --retries);
2037
2038	if (!sshdr_external)
2039		kfree(sshdr);
2040	return result;
2041}
2042EXPORT_SYMBOL(scsi_test_unit_ready);
2043
2044/**
2045 *	scsi_device_set_state - Take the given device through the device state model.
2046 *	@sdev:	scsi device to change the state of.
2047 *	@state:	state to change to.
2048 *
2049 *	Returns zero if unsuccessful or an error if the requested 
2050 *	transition is illegal.
2051 */
2052int
2053scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
2054{
2055	enum scsi_device_state oldstate = sdev->sdev_state;
2056
2057	if (state == oldstate)
2058		return 0;
2059
2060	switch (state) {
2061	case SDEV_CREATED:
2062		switch (oldstate) {
2063		case SDEV_CREATED_BLOCK:
2064			break;
2065		default:
2066			goto illegal;
2067		}
2068		break;
2069			
2070	case SDEV_RUNNING:
2071		switch (oldstate) {
2072		case SDEV_CREATED:
2073		case SDEV_OFFLINE:
2074		case SDEV_QUIESCE:
2075		case SDEV_BLOCK:
2076			break;
2077		default:
2078			goto illegal;
2079		}
2080		break;
2081
2082	case SDEV_QUIESCE:
2083		switch (oldstate) {
2084		case SDEV_RUNNING:
2085		case SDEV_OFFLINE:
2086			break;
2087		default:
2088			goto illegal;
2089		}
2090		break;
2091
2092	case SDEV_OFFLINE:
2093		switch (oldstate) {
2094		case SDEV_CREATED:
2095		case SDEV_RUNNING:
2096		case SDEV_QUIESCE:
2097		case SDEV_BLOCK:
2098			break;
2099		default:
2100			goto illegal;
2101		}
2102		break;
2103
2104	case SDEV_BLOCK:
2105		switch (oldstate) {
2106		case SDEV_RUNNING:
2107		case SDEV_CREATED_BLOCK:
2108			break;
2109		default:
2110			goto illegal;
2111		}
2112		break;
2113
2114	case SDEV_CREATED_BLOCK:
2115		switch (oldstate) {
2116		case SDEV_CREATED:
2117			break;
2118		default:
2119			goto illegal;
2120		}
2121		break;
2122
2123	case SDEV_CANCEL:
2124		switch (oldstate) {
2125		case SDEV_CREATED:
2126		case SDEV_RUNNING:
2127		case SDEV_QUIESCE:
2128		case SDEV_OFFLINE:
2129		case SDEV_BLOCK:
2130			break;
2131		default:
2132			goto illegal;
2133		}
2134		break;
2135
2136	case SDEV_DEL:
2137		switch (oldstate) {
2138		case SDEV_CREATED:
2139		case SDEV_RUNNING:
2140		case SDEV_OFFLINE:
2141		case SDEV_CANCEL:
2142			break;
2143		default:
2144			goto illegal;
2145		}
2146		break;
2147
2148	}
2149	sdev->sdev_state = state;
2150	return 0;
2151
2152 illegal:
2153	SCSI_LOG_ERROR_RECOVERY(1, 
2154				sdev_printk(KERN_ERR, sdev,
2155					    "Illegal state transition %s->%s\n",
2156					    scsi_device_state_name(oldstate),
2157					    scsi_device_state_name(state))
2158				);
2159	return -EINVAL;
2160}
2161EXPORT_SYMBOL(scsi_device_set_state);
2162
2163/**
2164 * 	sdev_evt_emit - emit a single SCSI device uevent
2165 *	@sdev: associated SCSI device
2166 *	@evt: event to emit
2167 *
2168 *	Send a single uevent (scsi_event) to the associated scsi_device.
2169 */
2170static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
2171{
2172	int idx = 0;
2173	char *envp[3];
2174
2175	switch (evt->evt_type) {
2176	case SDEV_EVT_MEDIA_CHANGE:
2177		envp[idx++] = "SDEV_MEDIA_CHANGE=1";
2178		break;
2179
2180	default:
2181		/* do nothing */
2182		break;
2183	}
2184
2185	envp[idx++] = NULL;
2186
2187	kobject_uevent_env(&sdev->sdev_gendev.kobj, KOBJ_CHANGE, envp);
2188}
2189
2190/**
2191 * 	sdev_evt_thread - send a uevent for each scsi event
2192 *	@work: work struct for scsi_device
2193 *
2194 *	Dispatch queued events to their associated scsi_device kobjects
2195 *	as uevents.
2196 */
2197void scsi_evt_thread(struct work_struct *work)
2198{
2199	struct scsi_device *sdev;
2200	LIST_HEAD(event_list);
2201
2202	sdev = container_of(work, struct scsi_device, event_work);
2203
2204	while (1) {
2205		struct scsi_event *evt;
2206		struct list_head *this, *tmp;
2207		unsigned long flags;
2208
2209		spin_lock_irqsave(&sdev->list_lock, flags);
2210		list_splice_init(&sdev->event_list, &event_list);
2211		spin_unlock_irqrestore(&sdev->list_lock, flags);
2212
2213		if (list_empty(&event_list))
2214			break;
2215
2216		list_for_each_safe(this, tmp, &event_list) {
2217			evt = list_entry(this, struct scsi_event, node);
2218			list_del(&evt->node);
2219			scsi_evt_emit(sdev, evt);
2220			kfree(evt);
2221		}
2222	}
2223}
2224
2225/**
2226 * 	sdev_evt_send - send asserted event to uevent thread
2227 *	@sdev: scsi_device event occurred on
2228 *	@evt: event to send
2229 *
2230 *	Assert scsi device event asynchronously.
2231 */
2232void sdev_evt_send(struct scsi_device *sdev, struct scsi_event *evt)
2233{
2234	unsigned long flags;
2235
2236#if 0
2237	/* FIXME: currently this check eliminates all media change events
2238	 * for polled devices.  Need to update to discriminate between AN
2239	 * and polled events */
2240	if (!test_bit(evt->evt_type, sdev->supported_events)) {
2241		kfree(evt);
2242		return;
2243	}
2244#endif
2245
2246	spin_lock_irqsave(&sdev->list_lock, flags);
2247	list_add_tail(&evt->node, &sdev->event_list);
2248	schedule_work(&sdev->event_work);
2249	spin_unlock_irqrestore(&sdev->list_lock, flags);
2250}
2251EXPORT_SYMBOL_GPL(sdev_evt_send);
2252
2253/**
2254 * 	sdev_evt_alloc - allocate a new scsi event
2255 *	@evt_type: type of event to allocate
2256 *	@gfpflags: GFP flags for allocation
2257 *
2258 *	Allocates and returns a new scsi_event.
2259 */
2260struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
2261				  gfp_t gfpflags)
2262{
2263	struct scsi_event *evt = kzalloc(sizeof(struct scsi_event), gfpflags);
2264	if (!evt)
2265		return NULL;
2266
2267	evt->evt_type = evt_type;
2268	INIT_LIST_HEAD(&evt->node);
2269
2270	/* evt_type-specific initialization, if any */
2271	switch (evt_type) {
2272	case SDEV_EVT_MEDIA_CHANGE:
2273	default:
2274		/* do nothing */
2275		break;
2276	}
2277
2278	return evt;
2279}
2280EXPORT_SYMBOL_GPL(sdev_evt_alloc);
2281
2282/**
2283 * 	sdev_evt_send_simple - send asserted event to uevent thread
2284 *	@sdev: scsi_device event occurred on
2285 *	@evt_type: type of event to send
2286 *	@gfpflags: GFP flags for allocation
2287 *
2288 *	Assert scsi device event asynchronously, given an event type.
2289 */
2290void sdev_evt_send_simple(struct scsi_device *sdev,
2291			  enum scsi_device_event evt_type, gfp_t gfpflags)
2292{
2293	struct scsi_event *evt = sdev_evt_alloc(evt_type, gfpflags);
2294	if (!evt) {
2295		sdev_printk(KERN_ERR, sdev, "event %d eaten due to OOM\n",
2296			    evt_type);
2297		return;
2298	}
2299
2300	sdev_evt_send(sdev, evt);
2301}
2302EXPORT_SYMBOL_GPL(sdev_evt_send_simple);
2303
2304/**
2305 *	scsi_device_quiesce - Block user issued commands.
2306 *	@sdev:	scsi device to quiesce.
2307 *
2308 *	This works by trying to transition to the SDEV_QUIESCE state
2309 *	(which must be a legal transition).  When the device is in this
2310 *	state, only special requests will be accepted, all others will
2311 *	be deferred.  Since special requests may also be requeued requests,
2312 *	a successful return doesn't guarantee the device will be 
2313 *	totally quiescent.
2314 *
2315 *	Must be called with user context, may sleep.
2316 *
2317 *	Returns zero if unsuccessful or an error if not.
2318 */
2319int
2320scsi_device_quiesce(struct scsi_device *sdev)
2321{
2322	int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
2323	if (err)
2324		return err;
2325
2326	scsi_run_queue(sdev->request_queue);
2327	while (sdev->device_busy) {
2328		msleep_interruptible(200);
2329		scsi_run_queue(sdev->request_queue);
2330	}
2331	return 0;
2332}
2333EXPORT_SYMBOL(scsi_device_quiesce);
2334
2335/**
2336 *	scsi_device_resume - Restart user issued commands to a quiesced device.
2337 *	@sdev:	scsi device to resume.
2338 *
2339 *	Moves the device from quiesced back to running and restarts the
2340 *	queues.
2341 *
2342 *	Must be called with user context, may sleep.
2343 */
2344void
2345scsi_device_resume(struct scsi_device *sdev)
2346{
2347	if(scsi_device_set_state(sdev, SDEV_RUNNING))
2348		return;
2349	scsi_run_queue(sdev->request_queue);
2350}
2351EXPORT_SYMBOL(scsi_device_resume);
2352
2353static void
2354device_quiesce_fn(struct scsi_device *sdev, void *data)
2355{
2356	scsi_device_quiesce(sdev);
2357}
2358
2359void
2360scsi_target_quiesce(struct scsi_target *starget)
2361{
2362	starget_for_each_device(starget, NULL, device_quiesce_fn);
2363}
2364EXPORT_SYMBOL(scsi_target_quiesce);
2365
2366static void
2367device_resume_fn(struct scsi_device *sdev, void *data)
2368{
2369	scsi_device_resume(sdev);
2370}
2371
2372void
2373scsi_target_resume(struct scsi_target *starget)
2374{
2375	starget_for_each_device(starget, NULL, device_resume_fn);
2376}
2377EXPORT_SYMBOL(scsi_target_resume);
2378
2379/**
2380 * scsi_internal_device_block - internal function to put a device temporarily into the SDEV_BLOCK state
2381 * @sdev:	device to block
2382 *
2383 * Block request made by scsi lld's to temporarily stop all
2384 * scsi commands on the specified device.  Called from interrupt
2385 * or normal process context.
2386 *
2387 * Returns zero if successful or error if not
2388 *
2389 * Notes:       
2390 *	This routine transitions the device to the SDEV_BLOCK state
2391 *	(which must be a legal transition).  When the device is in this
2392 *	state, all commands are deferred until the scsi lld reenables
2393 *	the device with scsi_device_unblock or device_block_tmo fires.
2394 *	This routine assumes the host_lock is held on entry.
2395 */
2396int
2397scsi_internal_device_block(struct scsi_device *sdev)
2398{
2399	struct request_queue *q = sdev->request_queue;
2400	unsigned long flags;
2401	int err = 0;
2402
2403	err = scsi_device_set_state(sdev, SDEV_BLOCK);
2404	if (err) {
2405		err = scsi_device_set_state(sdev, SDEV_CREATED_BLOCK);
2406
2407		if (err)
2408			return err;
2409	}
2410
2411	/* 
2412	 * The device has transitioned to SDEV_BLOCK.  Stop the
2413	 * block layer from calling the midlayer with this device's
2414	 * request queue. 
2415	 */
2416	spin_lock_irqsave(q->queue_lock, flags);
2417	blk_stop_queue(q);
2418	spin_unlock_irqrestore(q->queue_lock, flags);
2419
2420	return 0;
2421}
2422EXPORT_SYMBOL_GPL(scsi_internal_device_block);
2423 
2424/**
2425 * scsi_internal_device_unblock - resume a device after a block request
2426 * @sdev:	device to resume
2427 *
2428 * Called by scsi lld's or the midlayer to restart the device queue
2429 * for the previously suspended scsi device.  Called from interrupt or
2430 * normal process context.
2431 *
2432 * Returns zero if successful or error if not.
2433 *
2434 * Notes:       
2435 *	This routine transitions the device to the SDEV_RUNNING state
2436 *	(which must be a legal transition) allowing the midlayer to
2437 *	goose the queue for this device.  This routine assumes the 
2438 *	host_lock is held upon entry.
2439 */
2440int
2441scsi_internal_device_unblock(struct scsi_device *sdev)
2442{
2443	struct request_queue *q = sdev->request_queue; 
2444	unsigned long flags;
2445	
2446	/* 
2447	 * Try to transition the scsi device to SDEV_RUNNING
2448	 * and goose the device queue if successful.  
2449	 */
2450	if (sdev->sdev_state == SDEV_BLOCK)
2451		sdev->sdev_state = SDEV_RUNNING;
2452	else if (sdev->sdev_state == SDEV_CREATED_BLOCK)
2453		sdev->sdev_state = SDEV_CREATED;
2454	else if (sdev->sdev_state != SDEV_CANCEL &&
2455		 sdev->sdev_state != SDEV_OFFLINE)
2456		return -EINVAL;
2457
2458	spin_lock_irqsave(q->queue_lock, flags);
2459	blk_start_queue(q);
2460	spin_unlock_irqrestore(q->queue_lock, flags);
2461
2462	return 0;
2463}
2464EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
2465
2466static void
2467device_block(struct scsi_device *sdev, void *data)
2468{
2469	scsi_internal_device_block(sdev);
2470}
2471
2472static int
2473target_block(struct device *dev, void *data)
2474{
2475	if (scsi_is_target_device(dev))
2476		starget_for_each_device(to_scsi_target(dev), NULL,
2477					device_block);
2478	return 0;
2479}
2480
2481void
2482scsi_target_block(struct device *dev)
2483{
2484	if (scsi_is_target_device(dev))
2485		starget_for_each_device(to_scsi_target(dev), NULL,
2486					device_block);
2487	else
2488		device_for_each_child(dev, NULL, target_block);
2489}
2490EXPORT_SYMBOL_GPL(scsi_target_block);
2491
2492static void
2493device_unblock(struct scsi_device *sdev, void *data)
2494{
2495	scsi_internal_device_unblock(sdev);
2496}
2497
2498static int
2499target_unblock(struct device *dev, void *data)
2500{
2501	if (scsi_is_target_device(dev))
2502		starget_for_each_device(to_scsi_target(dev), NULL,
2503					device_unblock);
2504	return 0;
2505}
2506
2507void
2508scsi_target_unblock(struct device *dev)
2509{
2510	if (scsi_is_target_device(dev))
2511		starget_for_each_device(to_scsi_target(dev), NULL,
2512					device_unblock);
2513	else
2514		device_for_each_child(dev, NULL, target_unblock);
2515}
2516EXPORT_SYMBOL_GPL(scsi_target_unblock);
2517
2518/**
2519 * scsi_kmap_atomic_sg - find and atomically map an sg-elemnt
2520 * @sgl:	scatter-gather list
2521 * @sg_count:	number of segments in sg
2522 * @offset:	offset in bytes into sg, on return offset into the mapped area
2523 * @len:	bytes to map, on return number of bytes mapped
2524 *
2525 * Returns virtual address of the start of the mapped page
2526 */
2527void *scsi_kmap_atomic_sg(struct scatterlist *sgl, int sg_count,
2528			  size_t *offset, size_t *len)
2529{
2530	int i;
2531	size_t sg_len = 0, len_complete = 0;
2532	struct scatterlist *sg;
2533	struct page *page;
2534
2535	WARN_ON(!irqs_disabled());
2536
2537	for_each_sg(sgl, sg, sg_count, i) {
2538		len_complete = sg_len; /* Complete sg-entries */
2539		sg_len += sg->length;
2540		if (sg_len > *offset)
2541			break;
2542	}
2543
2544	if (unlikely(i == sg_count)) {
2545		printk(KERN_ERR "%s: Bytes in sg: %zu, requested offset %zu, "
2546			"elements %d\n",
2547		       __func__, sg_len, *offset, sg_count);
2548		WARN_ON(1);
2549		return NULL;
2550	}
2551
2552	/* Offset starting from the beginning of first page in this sg-entry */
2553	*offset = *offset - len_complete + sg->offset;
2554
2555	/* Assumption: contiguous pages can be accessed as "page + i" */
2556	page = nth_page(sg_page(sg), (*offset >> PAGE_SHIFT));
2557	*offset &= ~PAGE_MASK;
2558
2559	/* Bytes in this sg-entry from *offset to the end of the page */
2560	sg_len = PAGE_SIZE - *offset;
2561	if (*len > sg_len)
2562		*len = sg_len;
2563
2564	return kmap_atomic(page, KM_BIO_SRC_IRQ);
2565}
2566EXPORT_SYMBOL(scsi_kmap_atomic_sg);
2567
2568/**
2569 * scsi_kunmap_atomic_sg - atomically unmap a virtual address, previously mapped with scsi_kmap_atomic_sg
2570 * @virt:	virtual address to be unmapped
2571 */
2572void scsi_kunmap_atomic_sg(void *virt)
2573{
2574	kunmap_atomic(virt, KM_BIO_SRC_IRQ);
2575}
2576EXPORT_SYMBOL(scsi_kunmap_atomic_sg);