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scsi_lib.c (82989B)


      1 /*
      2  * Copyright (C) 1999 Eric Youngdale
      3  * Copyright (C) 2014 Christoph Hellwig
      4  *
      5  *  SCSI queueing library.
      6  *      Initial versions: Eric Youngdale (eric@andante.org).
      7  *                        Based upon conversations with large numbers
      8  *                        of people at Linux Expo.
      9  */
     10 
     11 #include <linux/bio.h>
     12 #include <linux/bitops.h>
     13 #include <linux/blkdev.h>
     14 #include <linux/completion.h>
     15 #include <linux/kernel.h>
     16 #include <linux/export.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 #include <linux/blk-mq.h>
     23 #include <linux/ratelimit.h>
     24 #include <asm/unaligned.h>
     25 
     26 #include <scsi/scsi.h>
     27 #include <scsi/scsi_cmnd.h>
     28 #include <scsi/scsi_dbg.h>
     29 #include <scsi/scsi_device.h>
     30 #include <scsi/scsi_driver.h>
     31 #include <scsi/scsi_eh.h>
     32 #include <scsi/scsi_host.h>
     33 #include <scsi/scsi_transport.h> /* __scsi_init_queue() */
     34 #include <scsi/scsi_dh.h>
     35 
     36 #include <trace/events/scsi.h>
     37 
     38 #include "scsi_debugfs.h"
     39 #include "scsi_priv.h"
     40 #include "scsi_logging.h"
     41 
     42 static struct kmem_cache *scsi_sdb_cache;
     43 static struct kmem_cache *scsi_sense_cache;
     44 static struct kmem_cache *scsi_sense_isadma_cache;
     45 static DEFINE_MUTEX(scsi_sense_cache_mutex);
     46 
     47 static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd);
     48 
     49 static inline struct kmem_cache *
     50 scsi_select_sense_cache(bool unchecked_isa_dma)
     51 {
     52 	return unchecked_isa_dma ? scsi_sense_isadma_cache : scsi_sense_cache;
     53 }
     54 
     55 static void scsi_free_sense_buffer(bool unchecked_isa_dma,
     56 				   unsigned char *sense_buffer)
     57 {
     58 	kmem_cache_free(scsi_select_sense_cache(unchecked_isa_dma),
     59 			sense_buffer);
     60 }
     61 
     62 static unsigned char *scsi_alloc_sense_buffer(bool unchecked_isa_dma,
     63 	gfp_t gfp_mask, int numa_node)
     64 {
     65 	return kmem_cache_alloc_node(scsi_select_sense_cache(unchecked_isa_dma),
     66 				     gfp_mask, numa_node);
     67 }
     68 
     69 int scsi_init_sense_cache(struct Scsi_Host *shost)
     70 {
     71 	struct kmem_cache *cache;
     72 	int ret = 0;
     73 
     74 	cache = scsi_select_sense_cache(shost->unchecked_isa_dma);
     75 	if (cache)
     76 		return 0;
     77 
     78 	mutex_lock(&scsi_sense_cache_mutex);
     79 	if (shost->unchecked_isa_dma) {
     80 		scsi_sense_isadma_cache =
     81 			kmem_cache_create("scsi_sense_cache(DMA)",
     82 				SCSI_SENSE_BUFFERSIZE, 0,
     83 				SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA, NULL);
     84 		if (!scsi_sense_isadma_cache)
     85 			ret = -ENOMEM;
     86 	} else {
     87 		scsi_sense_cache =
     88 			kmem_cache_create_usercopy("scsi_sense_cache",
     89 				SCSI_SENSE_BUFFERSIZE, 0, SLAB_HWCACHE_ALIGN,
     90 				0, SCSI_SENSE_BUFFERSIZE, NULL);
     91 		if (!scsi_sense_cache)
     92 			ret = -ENOMEM;
     93 	}
     94 
     95 	mutex_unlock(&scsi_sense_cache_mutex);
     96 	return ret;
     97 }
     98 
     99 /*
    100  * When to reinvoke queueing after a resource shortage. It's 3 msecs to
    101  * not change behaviour from the previous unplug mechanism, experimentation
    102  * may prove this needs changing.
    103  */
    104 #define SCSI_QUEUE_DELAY	3
    105 
    106 static void
    107 scsi_set_blocked(struct scsi_cmnd *cmd, int reason)
    108 {
    109 	struct Scsi_Host *host = cmd->device->host;
    110 	struct scsi_device *device = cmd->device;
    111 	struct scsi_target *starget = scsi_target(device);
    112 
    113 	/*
    114 	 * Set the appropriate busy bit for the device/host.
    115 	 *
    116 	 * If the host/device isn't busy, assume that something actually
    117 	 * completed, and that we should be able to queue a command now.
    118 	 *
    119 	 * Note that the prior mid-layer assumption that any host could
    120 	 * always queue at least one command is now broken.  The mid-layer
    121 	 * will implement a user specifiable stall (see
    122 	 * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
    123 	 * if a command is requeued with no other commands outstanding
    124 	 * either for the device or for the host.
    125 	 */
    126 	switch (reason) {
    127 	case SCSI_MLQUEUE_HOST_BUSY:
    128 		atomic_set(&host->host_blocked, host->max_host_blocked);
    129 		break;
    130 	case SCSI_MLQUEUE_DEVICE_BUSY:
    131 	case SCSI_MLQUEUE_EH_RETRY:
    132 		atomic_set(&device->device_blocked,
    133 			   device->max_device_blocked);
    134 		break;
    135 	case SCSI_MLQUEUE_TARGET_BUSY:
    136 		atomic_set(&starget->target_blocked,
    137 			   starget->max_target_blocked);
    138 		break;
    139 	}
    140 }
    141 
    142 static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd)
    143 {
    144 	struct scsi_device *sdev = cmd->device;
    145 
    146 	if (cmd->request->rq_flags & RQF_DONTPREP) {
    147 		cmd->request->rq_flags &= ~RQF_DONTPREP;
    148 		scsi_mq_uninit_cmd(cmd);
    149 	} else {
    150 		WARN_ON_ONCE(true);
    151 	}
    152 	blk_mq_requeue_request(cmd->request, true);
    153 	put_device(&sdev->sdev_gendev);
    154 }
    155 
    156 /**
    157  * __scsi_queue_insert - private queue insertion
    158  * @cmd: The SCSI command being requeued
    159  * @reason:  The reason for the requeue
    160  * @unbusy: Whether the queue should be unbusied
    161  *
    162  * This is a private queue insertion.  The public interface
    163  * scsi_queue_insert() always assumes the queue should be unbusied
    164  * because it's always called before the completion.  This function is
    165  * for a requeue after completion, which should only occur in this
    166  * file.
    167  */
    168 static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
    169 {
    170 	struct scsi_device *device = cmd->device;
    171 
    172 	SCSI_LOG_MLQUEUE(1, scmd_printk(KERN_INFO, cmd,
    173 		"Inserting command %p into mlqueue\n", cmd));
    174 
    175 	scsi_set_blocked(cmd, reason);
    176 
    177 	/*
    178 	 * Decrement the counters, since these commands are no longer
    179 	 * active on the host/device.
    180 	 */
    181 	if (unbusy)
    182 		scsi_device_unbusy(device);
    183 
    184 	/*
    185 	 * Requeue this command.  It will go before all other commands
    186 	 * that are already in the queue. Schedule requeue work under
    187 	 * lock such that the kblockd_schedule_work() call happens
    188 	 * before blk_cleanup_queue() finishes.
    189 	 */
    190 	cmd->result = 0;
    191 
    192 	/*
    193 	 * Before a SCSI command is dispatched,
    194 	 * get_device(&sdev->sdev_gendev) is called and the host,
    195 	 * target and device busy counters are increased. Since
    196 	 * requeuing a request causes these actions to be repeated and
    197 	 * since scsi_device_unbusy() has already been called,
    198 	 * put_device(&device->sdev_gendev) must still be called. Call
    199 	 * put_device() after blk_mq_requeue_request() to avoid that
    200 	 * removal of the SCSI device can start before requeueing has
    201 	 * happened.
    202 	 */
    203 	blk_mq_requeue_request(cmd->request, true);
    204 	put_device(&device->sdev_gendev);
    205 }
    206 
    207 /*
    208  * Function:    scsi_queue_insert()
    209  *
    210  * Purpose:     Insert a command in the midlevel queue.
    211  *
    212  * Arguments:   cmd    - command that we are adding to queue.
    213  *              reason - why we are inserting command to queue.
    214  *
    215  * Lock status: Assumed that lock is not held upon entry.
    216  *
    217  * Returns:     Nothing.
    218  *
    219  * Notes:       We do this for one of two cases.  Either the host is busy
    220  *              and it cannot accept any more commands for the time being,
    221  *              or the device returned QUEUE_FULL and can accept no more
    222  *              commands.
    223  * Notes:       This could be called either from an interrupt context or a
    224  *              normal process context.
    225  */
    226 void scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
    227 {
    228 	__scsi_queue_insert(cmd, reason, true);
    229 }
    230 
    231 
    232 /**
    233  * __scsi_execute - insert request and wait for the result
    234  * @sdev:	scsi device
    235  * @cmd:	scsi command
    236  * @data_direction: data direction
    237  * @buffer:	data buffer
    238  * @bufflen:	len of buffer
    239  * @sense:	optional sense buffer
    240  * @sshdr:	optional decoded sense header
    241  * @timeout:	request timeout in seconds
    242  * @retries:	number of times to retry request
    243  * @flags:	flags for ->cmd_flags
    244  * @rq_flags:	flags for ->rq_flags
    245  * @resid:	optional residual length
    246  *
    247  * Returns the scsi_cmnd result field if a command was executed, or a negative
    248  * Linux error code if we didn't get that far.
    249  */
    250 int __scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
    251 		 int data_direction, void *buffer, unsigned bufflen,
    252 		 unsigned char *sense, struct scsi_sense_hdr *sshdr,
    253 		 int timeout, int retries, u64 flags, req_flags_t rq_flags,
    254 		 int *resid)
    255 {
    256 	struct request *req;
    257 	struct scsi_request *rq;
    258 	int ret = DRIVER_ERROR << 24;
    259 
    260 	req = blk_get_request(sdev->request_queue,
    261 			data_direction == DMA_TO_DEVICE ?
    262 			REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN, BLK_MQ_REQ_PREEMPT);
    263 	if (IS_ERR(req))
    264 		return ret;
    265 	rq = scsi_req(req);
    266 
    267 	if (bufflen &&	blk_rq_map_kern(sdev->request_queue, req,
    268 					buffer, bufflen, GFP_NOIO))
    269 		goto out;
    270 
    271 	rq->cmd_len = COMMAND_SIZE(cmd[0]);
    272 	memcpy(rq->cmd, cmd, rq->cmd_len);
    273 	rq->retries = retries;
    274 	req->timeout = timeout;
    275 	req->cmd_flags |= flags;
    276 	req->rq_flags |= rq_flags | RQF_QUIET;
    277 
    278 	/*
    279 	 * head injection *required* here otherwise quiesce won't work
    280 	 */
    281 	blk_execute_rq(req->q, NULL, req, 1);
    282 
    283 	/*
    284 	 * Some devices (USB mass-storage in particular) may transfer
    285 	 * garbage data together with a residue indicating that the data
    286 	 * is invalid.  Prevent the garbage from being misinterpreted
    287 	 * and prevent security leaks by zeroing out the excess data.
    288 	 */
    289 	if (unlikely(rq->resid_len > 0 && rq->resid_len <= bufflen))
    290 		memset(buffer + (bufflen - rq->resid_len), 0, rq->resid_len);
    291 
    292 	if (resid)
    293 		*resid = rq->resid_len;
    294 	if (sense && rq->sense_len)
    295 		memcpy(sense, rq->sense, SCSI_SENSE_BUFFERSIZE);
    296 	if (sshdr)
    297 		scsi_normalize_sense(rq->sense, rq->sense_len, sshdr);
    298 	ret = rq->result;
    299  out:
    300 	blk_put_request(req);
    301 
    302 	return ret;
    303 }
    304 EXPORT_SYMBOL(__scsi_execute);
    305 
    306 /*
    307  * Function:    scsi_init_cmd_errh()
    308  *
    309  * Purpose:     Initialize cmd fields related to error handling.
    310  *
    311  * Arguments:   cmd	- command that is ready to be queued.
    312  *
    313  * Notes:       This function has the job of initializing a number of
    314  *              fields related to error handling.   Typically this will
    315  *              be called once for each command, as required.
    316  */
    317 static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
    318 {
    319 	scsi_set_resid(cmd, 0);
    320 	memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
    321 	if (cmd->cmd_len == 0)
    322 		cmd->cmd_len = scsi_command_size(cmd->cmnd);
    323 }
    324 
    325 /*
    326  * Decrement the host_busy counter and wake up the error handler if necessary.
    327  * Avoid as follows that the error handler is not woken up if shost->host_busy
    328  * == shost->host_failed: use call_rcu() in scsi_eh_scmd_add() in combination
    329  * with an RCU read lock in this function to ensure that this function in its
    330  * entirety either finishes before scsi_eh_scmd_add() increases the
    331  * host_failed counter or that it notices the shost state change made by
    332  * scsi_eh_scmd_add().
    333  */
    334 static void scsi_dec_host_busy(struct Scsi_Host *shost)
    335 {
    336 	unsigned long flags;
    337 
    338 	rcu_read_lock();
    339 	atomic_dec(&shost->host_busy);
    340 	if (unlikely(scsi_host_in_recovery(shost))) {
    341 		spin_lock_irqsave(shost->host_lock, flags);
    342 		if (shost->host_failed || shost->host_eh_scheduled)
    343 			scsi_eh_wakeup(shost);
    344 		spin_unlock_irqrestore(shost->host_lock, flags);
    345 	}
    346 	rcu_read_unlock();
    347 }
    348 
    349 void scsi_device_unbusy(struct scsi_device *sdev)
    350 {
    351 	struct Scsi_Host *shost = sdev->host;
    352 	struct scsi_target *starget = scsi_target(sdev);
    353 
    354 	scsi_dec_host_busy(shost);
    355 
    356 	if (starget->can_queue > 0)
    357 		atomic_dec(&starget->target_busy);
    358 
    359 	atomic_dec(&sdev->device_busy);
    360 }
    361 
    362 static void scsi_kick_queue(struct request_queue *q)
    363 {
    364 	blk_mq_run_hw_queues(q, false);
    365 }
    366 
    367 /*
    368  * Called for single_lun devices on IO completion. Clear starget_sdev_user,
    369  * and call blk_run_queue for all the scsi_devices on the target -
    370  * including current_sdev first.
    371  *
    372  * Called with *no* scsi locks held.
    373  */
    374 static void scsi_single_lun_run(struct scsi_device *current_sdev)
    375 {
    376 	struct Scsi_Host *shost = current_sdev->host;
    377 	struct scsi_device *sdev, *tmp;
    378 	struct scsi_target *starget = scsi_target(current_sdev);
    379 	unsigned long flags;
    380 
    381 	spin_lock_irqsave(shost->host_lock, flags);
    382 	starget->starget_sdev_user = NULL;
    383 	spin_unlock_irqrestore(shost->host_lock, flags);
    384 
    385 	/*
    386 	 * Call blk_run_queue for all LUNs on the target, starting with
    387 	 * current_sdev. We race with others (to set starget_sdev_user),
    388 	 * but in most cases, we will be first. Ideally, each LU on the
    389 	 * target would get some limited time or requests on the target.
    390 	 */
    391 	scsi_kick_queue(current_sdev->request_queue);
    392 
    393 	spin_lock_irqsave(shost->host_lock, flags);
    394 	if (starget->starget_sdev_user)
    395 		goto out;
    396 	list_for_each_entry_safe(sdev, tmp, &starget->devices,
    397 			same_target_siblings) {
    398 		if (sdev == current_sdev)
    399 			continue;
    400 		if (scsi_device_get(sdev))
    401 			continue;
    402 
    403 		spin_unlock_irqrestore(shost->host_lock, flags);
    404 		scsi_kick_queue(sdev->request_queue);
    405 		spin_lock_irqsave(shost->host_lock, flags);
    406 	
    407 		scsi_device_put(sdev);
    408 	}
    409  out:
    410 	spin_unlock_irqrestore(shost->host_lock, flags);
    411 }
    412 
    413 static inline bool scsi_device_is_busy(struct scsi_device *sdev)
    414 {
    415 	if (atomic_read(&sdev->device_busy) >= sdev->queue_depth)
    416 		return true;
    417 	if (atomic_read(&sdev->device_blocked) > 0)
    418 		return true;
    419 	return false;
    420 }
    421 
    422 static inline bool scsi_target_is_busy(struct scsi_target *starget)
    423 {
    424 	if (starget->can_queue > 0) {
    425 		if (atomic_read(&starget->target_busy) >= starget->can_queue)
    426 			return true;
    427 		if (atomic_read(&starget->target_blocked) > 0)
    428 			return true;
    429 	}
    430 	return false;
    431 }
    432 
    433 static inline bool scsi_host_is_busy(struct Scsi_Host *shost)
    434 {
    435 	if (shost->can_queue > 0 &&
    436 	    atomic_read(&shost->host_busy) >= shost->can_queue)
    437 		return true;
    438 	if (atomic_read(&shost->host_blocked) > 0)
    439 		return true;
    440 	if (shost->host_self_blocked)
    441 		return true;
    442 	return false;
    443 }
    444 
    445 static void scsi_starved_list_run(struct Scsi_Host *shost)
    446 {
    447 	LIST_HEAD(starved_list);
    448 	struct scsi_device *sdev;
    449 	unsigned long flags;
    450 
    451 	spin_lock_irqsave(shost->host_lock, flags);
    452 	list_splice_init(&shost->starved_list, &starved_list);
    453 
    454 	while (!list_empty(&starved_list)) {
    455 		struct request_queue *slq;
    456 
    457 		/*
    458 		 * As long as shost is accepting commands and we have
    459 		 * starved queues, call blk_run_queue. scsi_request_fn
    460 		 * drops the queue_lock and can add us back to the
    461 		 * starved_list.
    462 		 *
    463 		 * host_lock protects the starved_list and starved_entry.
    464 		 * scsi_request_fn must get the host_lock before checking
    465 		 * or modifying starved_list or starved_entry.
    466 		 */
    467 		if (scsi_host_is_busy(shost))
    468 			break;
    469 
    470 		sdev = list_entry(starved_list.next,
    471 				  struct scsi_device, starved_entry);
    472 		list_del_init(&sdev->starved_entry);
    473 		if (scsi_target_is_busy(scsi_target(sdev))) {
    474 			list_move_tail(&sdev->starved_entry,
    475 				       &shost->starved_list);
    476 			continue;
    477 		}
    478 
    479 		/*
    480 		 * Once we drop the host lock, a racing scsi_remove_device()
    481 		 * call may remove the sdev from the starved list and destroy
    482 		 * it and the queue.  Mitigate by taking a reference to the
    483 		 * queue and never touching the sdev again after we drop the
    484 		 * host lock.  Note: if __scsi_remove_device() invokes
    485 		 * blk_cleanup_queue() before the queue is run from this
    486 		 * function then blk_run_queue() will return immediately since
    487 		 * blk_cleanup_queue() marks the queue with QUEUE_FLAG_DYING.
    488 		 */
    489 		slq = sdev->request_queue;
    490 		if (!blk_get_queue(slq))
    491 			continue;
    492 		spin_unlock_irqrestore(shost->host_lock, flags);
    493 
    494 		scsi_kick_queue(slq);
    495 		blk_put_queue(slq);
    496 
    497 		spin_lock_irqsave(shost->host_lock, flags);
    498 	}
    499 	/* put any unprocessed entries back */
    500 	list_splice(&starved_list, &shost->starved_list);
    501 	spin_unlock_irqrestore(shost->host_lock, flags);
    502 }
    503 
    504 /*
    505  * Function:   scsi_run_queue()
    506  *
    507  * Purpose:    Select a proper request queue to serve next
    508  *
    509  * Arguments:  q       - last request's queue
    510  *
    511  * Returns:     Nothing
    512  *
    513  * Notes:      The previous command was completely finished, start
    514  *             a new one if possible.
    515  */
    516 static void scsi_run_queue(struct request_queue *q)
    517 {
    518 	struct scsi_device *sdev = q->queuedata;
    519 
    520 	if (scsi_target(sdev)->single_lun)
    521 		scsi_single_lun_run(sdev);
    522 	if (!list_empty(&sdev->host->starved_list))
    523 		scsi_starved_list_run(sdev->host);
    524 
    525 	blk_mq_run_hw_queues(q, false);
    526 }
    527 
    528 void scsi_requeue_run_queue(struct work_struct *work)
    529 {
    530 	struct scsi_device *sdev;
    531 	struct request_queue *q;
    532 
    533 	sdev = container_of(work, struct scsi_device, requeue_work);
    534 	q = sdev->request_queue;
    535 	scsi_run_queue(q);
    536 }
    537 
    538 void scsi_run_host_queues(struct Scsi_Host *shost)
    539 {
    540 	struct scsi_device *sdev;
    541 
    542 	shost_for_each_device(sdev, shost)
    543 		scsi_run_queue(sdev->request_queue);
    544 }
    545 
    546 static void scsi_uninit_cmd(struct scsi_cmnd *cmd)
    547 {
    548 	if (!blk_rq_is_passthrough(cmd->request)) {
    549 		struct scsi_driver *drv = scsi_cmd_to_driver(cmd);
    550 
    551 		if (drv->uninit_command)
    552 			drv->uninit_command(cmd);
    553 	}
    554 }
    555 
    556 static void scsi_mq_free_sgtables(struct scsi_cmnd *cmd)
    557 {
    558 	if (cmd->sdb.table.nents)
    559 		sg_free_table_chained(&cmd->sdb.table, true);
    560 	if (scsi_prot_sg_count(cmd))
    561 		sg_free_table_chained(&cmd->prot_sdb->table, true);
    562 }
    563 
    564 static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
    565 {
    566 	scsi_mq_free_sgtables(cmd);
    567 	scsi_uninit_cmd(cmd);
    568 	scsi_del_cmd_from_list(cmd);
    569 }
    570 
    571 /* Returns false when no more bytes to process, true if there are more */
    572 static bool scsi_end_request(struct request *req, blk_status_t error,
    573 		unsigned int bytes)
    574 {
    575 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
    576 	struct scsi_device *sdev = cmd->device;
    577 	struct request_queue *q = sdev->request_queue;
    578 
    579 	if (blk_update_request(req, error, bytes))
    580 		return true;
    581 
    582 	if (blk_queue_add_random(q))
    583 		add_disk_randomness(req->rq_disk);
    584 
    585 	if (!blk_rq_is_scsi(req)) {
    586 		WARN_ON_ONCE(!(cmd->flags & SCMD_INITIALIZED));
    587 		cmd->flags &= ~SCMD_INITIALIZED;
    588 	}
    589 
    590 	/*
    591 	 * Calling rcu_barrier() is not necessary here because the
    592 	 * SCSI error handler guarantees that the function called by
    593 	 * call_rcu() has been called before scsi_end_request() is
    594 	 * called.
    595 	 */
    596 	destroy_rcu_head(&cmd->rcu);
    597 
    598 	/*
    599 	 * In the MQ case the command gets freed by __blk_mq_end_request,
    600 	 * so we have to do all cleanup that depends on it earlier.
    601 	 *
    602 	 * We also can't kick the queues from irq context, so we
    603 	 * will have to defer it to a workqueue.
    604 	 */
    605 	scsi_mq_uninit_cmd(cmd);
    606 
    607 	/*
    608 	 * queue is still alive, so grab the ref for preventing it
    609 	 * from being cleaned up during running queue.
    610 	 */
    611 	percpu_ref_get(&q->q_usage_counter);
    612 
    613 	__blk_mq_end_request(req, error);
    614 
    615 	if (scsi_target(sdev)->single_lun ||
    616 	    !list_empty(&sdev->host->starved_list))
    617 		kblockd_schedule_work(&sdev->requeue_work);
    618 	else
    619 		blk_mq_run_hw_queues(q, true);
    620 
    621 	percpu_ref_put(&q->q_usage_counter);
    622 	put_device(&sdev->sdev_gendev);
    623 	return false;
    624 }
    625 
    626 /**
    627  * scsi_result_to_blk_status - translate a SCSI result code into blk_status_t
    628  * @cmd:	SCSI command
    629  * @result:	scsi error code
    630  *
    631  * Translate a SCSI result code into a blk_status_t value. May reset the host
    632  * byte of @cmd->result.
    633  */
    634 static blk_status_t scsi_result_to_blk_status(struct scsi_cmnd *cmd, int result)
    635 {
    636 	switch (host_byte(result)) {
    637 	case DID_OK:
    638 		/*
    639 		 * Also check the other bytes than the status byte in result
    640 		 * to handle the case when a SCSI LLD sets result to
    641 		 * DRIVER_SENSE << 24 without setting SAM_STAT_CHECK_CONDITION.
    642 		 */
    643 		if (scsi_status_is_good(result) && (result & ~0xff) == 0)
    644 			return BLK_STS_OK;
    645 		return BLK_STS_IOERR;
    646 	case DID_TRANSPORT_FAILFAST:
    647 		return BLK_STS_TRANSPORT;
    648 	case DID_TARGET_FAILURE:
    649 		set_host_byte(cmd, DID_OK);
    650 		return BLK_STS_TARGET;
    651 	case DID_NEXUS_FAILURE:
    652 		set_host_byte(cmd, DID_OK);
    653 		return BLK_STS_NEXUS;
    654 	case DID_ALLOC_FAILURE:
    655 		set_host_byte(cmd, DID_OK);
    656 		return BLK_STS_NOSPC;
    657 	case DID_MEDIUM_ERROR:
    658 		set_host_byte(cmd, DID_OK);
    659 		return BLK_STS_MEDIUM;
    660 	default:
    661 		return BLK_STS_IOERR;
    662 	}
    663 }
    664 
    665 /* Helper for scsi_io_completion() when "reprep" action required. */
    666 static void scsi_io_completion_reprep(struct scsi_cmnd *cmd,
    667 				      struct request_queue *q)
    668 {
    669 	/* A new command will be prepared and issued. */
    670 	scsi_mq_requeue_cmd(cmd);
    671 }
    672 
    673 /* Helper for scsi_io_completion() when special action required. */
    674 static void scsi_io_completion_action(struct scsi_cmnd *cmd, int result)
    675 {
    676 	struct request_queue *q = cmd->device->request_queue;
    677 	struct request *req = cmd->request;
    678 	int level = 0;
    679 	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
    680 	      ACTION_DELAYED_RETRY} action;
    681 	unsigned long wait_for = (cmd->allowed + 1) * req->timeout;
    682 	struct scsi_sense_hdr sshdr;
    683 	bool sense_valid;
    684 	bool sense_current = true;      /* false implies "deferred sense" */
    685 	blk_status_t blk_stat;
    686 
    687 	sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
    688 	if (sense_valid)
    689 		sense_current = !scsi_sense_is_deferred(&sshdr);
    690 
    691 	blk_stat = scsi_result_to_blk_status(cmd, result);
    692 
    693 	if (host_byte(result) == DID_RESET) {
    694 		/* Third party bus reset or reset for error recovery
    695 		 * reasons.  Just retry the command and see what
    696 		 * happens.
    697 		 */
    698 		action = ACTION_RETRY;
    699 	} else if (sense_valid && sense_current) {
    700 		switch (sshdr.sense_key) {
    701 		case UNIT_ATTENTION:
    702 			if (cmd->device->removable) {
    703 				/* Detected disc change.  Set a bit
    704 				 * and quietly refuse further access.
    705 				 */
    706 				cmd->device->changed = 1;
    707 				action = ACTION_FAIL;
    708 			} else {
    709 				/* Must have been a power glitch, or a
    710 				 * bus reset.  Could not have been a
    711 				 * media change, so we just retry the
    712 				 * command and see what happens.
    713 				 */
    714 				action = ACTION_RETRY;
    715 			}
    716 			break;
    717 		case ILLEGAL_REQUEST:
    718 			/* If we had an ILLEGAL REQUEST returned, then
    719 			 * we may have performed an unsupported
    720 			 * command.  The only thing this should be
    721 			 * would be a ten byte read where only a six
    722 			 * byte read was supported.  Also, on a system
    723 			 * where READ CAPACITY failed, we may have
    724 			 * read past the end of the disk.
    725 			 */
    726 			if ((cmd->device->use_10_for_rw &&
    727 			    sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
    728 			    (cmd->cmnd[0] == READ_10 ||
    729 			     cmd->cmnd[0] == WRITE_10)) {
    730 				/* This will issue a new 6-byte command. */
    731 				cmd->device->use_10_for_rw = 0;
    732 				action = ACTION_REPREP;
    733 			} else if (sshdr.asc == 0x10) /* DIX */ {
    734 				action = ACTION_FAIL;
    735 				blk_stat = BLK_STS_PROTECTION;
    736 			/* INVALID COMMAND OPCODE or INVALID FIELD IN CDB */
    737 			} else if (sshdr.asc == 0x20 || sshdr.asc == 0x24) {
    738 				action = ACTION_FAIL;
    739 				blk_stat = BLK_STS_TARGET;
    740 			} else
    741 				action = ACTION_FAIL;
    742 			break;
    743 		case ABORTED_COMMAND:
    744 			action = ACTION_FAIL;
    745 			if (sshdr.asc == 0x10) /* DIF */
    746 				blk_stat = BLK_STS_PROTECTION;
    747 			break;
    748 		case NOT_READY:
    749 			/* If the device is in the process of becoming
    750 			 * ready, or has a temporary blockage, retry.
    751 			 */
    752 			if (sshdr.asc == 0x04) {
    753 				switch (sshdr.ascq) {
    754 				case 0x01: /* becoming ready */
    755 				case 0x04: /* format in progress */
    756 				case 0x05: /* rebuild in progress */
    757 				case 0x06: /* recalculation in progress */
    758 				case 0x07: /* operation in progress */
    759 				case 0x08: /* Long write in progress */
    760 				case 0x09: /* self test in progress */
    761 				case 0x14: /* space allocation in progress */
    762 				case 0x1a: /* start stop unit in progress */
    763 				case 0x1b: /* sanitize in progress */
    764 				case 0x1d: /* configuration in progress */
    765 				case 0x24: /* depopulation in progress */
    766 					action = ACTION_DELAYED_RETRY;
    767 					break;
    768 				default:
    769 					action = ACTION_FAIL;
    770 					break;
    771 				}
    772 			} else
    773 				action = ACTION_FAIL;
    774 			break;
    775 		case VOLUME_OVERFLOW:
    776 			/* See SSC3rXX or current. */
    777 			action = ACTION_FAIL;
    778 			break;
    779 		default:
    780 			action = ACTION_FAIL;
    781 			break;
    782 		}
    783 	} else
    784 		action = ACTION_FAIL;
    785 
    786 	if (action != ACTION_FAIL &&
    787 	    time_before(cmd->jiffies_at_alloc + wait_for, jiffies))
    788 		action = ACTION_FAIL;
    789 
    790 	switch (action) {
    791 	case ACTION_FAIL:
    792 		/* Give up and fail the remainder of the request */
    793 		if (!(req->rq_flags & RQF_QUIET)) {
    794 			static DEFINE_RATELIMIT_STATE(_rs,
    795 					DEFAULT_RATELIMIT_INTERVAL,
    796 					DEFAULT_RATELIMIT_BURST);
    797 
    798 			if (unlikely(scsi_logging_level))
    799 				level =
    800 				     SCSI_LOG_LEVEL(SCSI_LOG_MLCOMPLETE_SHIFT,
    801 						    SCSI_LOG_MLCOMPLETE_BITS);
    802 
    803 			/*
    804 			 * if logging is enabled the failure will be printed
    805 			 * in scsi_log_completion(), so avoid duplicate messages
    806 			 */
    807 			if (!level && __ratelimit(&_rs)) {
    808 				scsi_print_result(cmd, NULL, FAILED);
    809 				if (driver_byte(result) == DRIVER_SENSE)
    810 					scsi_print_sense(cmd);
    811 				scsi_print_command(cmd);
    812 			}
    813 		}
    814 		if (!scsi_end_request(req, blk_stat, blk_rq_err_bytes(req)))
    815 			return;
    816 		/*FALLTHRU*/
    817 	case ACTION_REPREP:
    818 		scsi_io_completion_reprep(cmd, q);
    819 		break;
    820 	case ACTION_RETRY:
    821 		/* Retry the same command immediately */
    822 		__scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, false);
    823 		break;
    824 	case ACTION_DELAYED_RETRY:
    825 		/* Retry the same command after a delay */
    826 		__scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, false);
    827 		break;
    828 	}
    829 }
    830 
    831 /*
    832  * Helper for scsi_io_completion() when cmd->result is non-zero. Returns a
    833  * new result that may suppress further error checking. Also modifies
    834  * *blk_statp in some cases.
    835  */
    836 static int scsi_io_completion_nz_result(struct scsi_cmnd *cmd, int result,
    837 					blk_status_t *blk_statp)
    838 {
    839 	bool sense_valid;
    840 	bool sense_current = true;	/* false implies "deferred sense" */
    841 	struct request *req = cmd->request;
    842 	struct scsi_sense_hdr sshdr;
    843 
    844 	sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
    845 	if (sense_valid)
    846 		sense_current = !scsi_sense_is_deferred(&sshdr);
    847 
    848 	if (blk_rq_is_passthrough(req)) {
    849 		if (sense_valid) {
    850 			/*
    851 			 * SG_IO wants current and deferred errors
    852 			 */
    853 			scsi_req(req)->sense_len =
    854 				min(8 + cmd->sense_buffer[7],
    855 				    SCSI_SENSE_BUFFERSIZE);
    856 		}
    857 		if (sense_current)
    858 			*blk_statp = scsi_result_to_blk_status(cmd, result);
    859 	} else if (blk_rq_bytes(req) == 0 && sense_current) {
    860 		/*
    861 		 * Flush commands do not transfers any data, and thus cannot use
    862 		 * good_bytes != blk_rq_bytes(req) as the signal for an error.
    863 		 * This sets *blk_statp explicitly for the problem case.
    864 		 */
    865 		*blk_statp = scsi_result_to_blk_status(cmd, result);
    866 	}
    867 	/*
    868 	 * Recovered errors need reporting, but they're always treated as
    869 	 * success, so fiddle the result code here.  For passthrough requests
    870 	 * we already took a copy of the original into sreq->result which
    871 	 * is what gets returned to the user
    872 	 */
    873 	if (sense_valid && (sshdr.sense_key == RECOVERED_ERROR)) {
    874 		bool do_print = true;
    875 		/*
    876 		 * if ATA PASS-THROUGH INFORMATION AVAILABLE [0x0, 0x1d]
    877 		 * skip print since caller wants ATA registers. Only occurs
    878 		 * on SCSI ATA PASS_THROUGH commands when CK_COND=1
    879 		 */
    880 		if ((sshdr.asc == 0x0) && (sshdr.ascq == 0x1d))
    881 			do_print = false;
    882 		else if (req->rq_flags & RQF_QUIET)
    883 			do_print = false;
    884 		if (do_print)
    885 			scsi_print_sense(cmd);
    886 		result = 0;
    887 		/* for passthrough, *blk_statp may be set */
    888 		*blk_statp = BLK_STS_OK;
    889 	}
    890 	/*
    891 	 * Another corner case: the SCSI status byte is non-zero but 'good'.
    892 	 * Example: PRE-FETCH command returns SAM_STAT_CONDITION_MET when
    893 	 * it is able to fit nominated LBs in its cache (and SAM_STAT_GOOD
    894 	 * if it can't fit). Treat SAM_STAT_CONDITION_MET and the related
    895 	 * intermediate statuses (both obsolete in SAM-4) as good.
    896 	 */
    897 	if (status_byte(result) && scsi_status_is_good(result)) {
    898 		result = 0;
    899 		*blk_statp = BLK_STS_OK;
    900 	}
    901 	return result;
    902 }
    903 
    904 /*
    905  * Function:    scsi_io_completion()
    906  *
    907  * Purpose:     Completion processing for block device I/O requests.
    908  *
    909  * Arguments:   cmd   - command that is finished.
    910  *
    911  * Lock status: Assumed that no lock is held upon entry.
    912  *
    913  * Returns:     Nothing
    914  *
    915  * Notes:       We will finish off the specified number of sectors.  If we
    916  *		are done, the command block will be released and the queue
    917  *		function will be goosed.  If we are not done then we have to
    918  *		figure out what to do next:
    919  *
    920  *		a) We can call scsi_requeue_command().  The request
    921  *		   will be unprepared and put back on the queue.  Then
    922  *		   a new command will be created for it.  This should
    923  *		   be used if we made forward progress, or if we want
    924  *		   to switch from READ(10) to READ(6) for example.
    925  *
    926  *		b) We can call __scsi_queue_insert().  The request will
    927  *		   be put back on the queue and retried using the same
    928  *		   command as before, possibly after a delay.
    929  *
    930  *		c) We can call scsi_end_request() with blk_stat other than
    931  *		   BLK_STS_OK, to fail the remainder of the request.
    932  */
    933 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
    934 {
    935 	int result = cmd->result;
    936 	struct request_queue *q = cmd->device->request_queue;
    937 	struct request *req = cmd->request;
    938 	blk_status_t blk_stat = BLK_STS_OK;
    939 
    940 	if (unlikely(result))	/* a nz result may or may not be an error */
    941 		result = scsi_io_completion_nz_result(cmd, result, &blk_stat);
    942 
    943 	if (unlikely(blk_rq_is_passthrough(req))) {
    944 		/*
    945 		 * scsi_result_to_blk_status may have reset the host_byte
    946 		 */
    947 		scsi_req(req)->result = cmd->result;
    948 	}
    949 
    950 	/*
    951 	 * Next deal with any sectors which we were able to correctly
    952 	 * handle.
    953 	 */
    954 	SCSI_LOG_HLCOMPLETE(1, scmd_printk(KERN_INFO, cmd,
    955 		"%u sectors total, %d bytes done.\n",
    956 		blk_rq_sectors(req), good_bytes));
    957 
    958 	/*
    959 	 * Next deal with any sectors which we were able to correctly
    960 	 * handle. Failed, zero length commands always need to drop down
    961 	 * to retry code. Fast path should return in this block.
    962 	 */
    963 	if (likely(blk_rq_bytes(req) > 0 || blk_stat == BLK_STS_OK)) {
    964 		if (likely(!scsi_end_request(req, blk_stat, good_bytes)))
    965 			return; /* no bytes remaining */
    966 	}
    967 
    968 	/* Kill remainder if no retries. */
    969 	if (unlikely(blk_stat && scsi_noretry_cmd(cmd))) {
    970 		if (scsi_end_request(req, blk_stat, blk_rq_bytes(req)))
    971 			WARN_ONCE(true,
    972 			    "Bytes remaining after failed, no-retry command");
    973 		return;
    974 	}
    975 
    976 	/*
    977 	 * If there had been no error, but we have leftover bytes in the
    978 	 * requeues just queue the command up again.
    979 	 */
    980 	if (likely(result == 0))
    981 		scsi_io_completion_reprep(cmd, q);
    982 	else
    983 		scsi_io_completion_action(cmd, result);
    984 }
    985 
    986 static blk_status_t scsi_init_sgtable(struct request *req,
    987 		struct scsi_data_buffer *sdb)
    988 {
    989 	int count;
    990 
    991 	/*
    992 	 * If sg table allocation fails, requeue request later.
    993 	 */
    994 	if (unlikely(sg_alloc_table_chained(&sdb->table,
    995 			blk_rq_nr_phys_segments(req), sdb->table.sgl)))
    996 		return BLK_STS_RESOURCE;
    997 
    998 	/* 
    999 	 * Next, walk the list, and fill in the addresses and sizes of
   1000 	 * each segment.
   1001 	 */
   1002 	count = blk_rq_map_sg(req->q, req, sdb->table.sgl);
   1003 	BUG_ON(count > sdb->table.nents);
   1004 	sdb->table.nents = count;
   1005 	sdb->length = blk_rq_payload_bytes(req);
   1006 	return BLK_STS_OK;
   1007 }
   1008 
   1009 /*
   1010  * Function:    scsi_init_io()
   1011  *
   1012  * Purpose:     SCSI I/O initialize function.
   1013  *
   1014  * Arguments:   cmd   - Command descriptor we wish to initialize
   1015  *
   1016  * Returns:     BLK_STS_OK on success
   1017  *		BLK_STS_RESOURCE if the failure is retryable
   1018  *		BLK_STS_IOERR if the failure is fatal
   1019  */
   1020 blk_status_t scsi_init_io(struct scsi_cmnd *cmd)
   1021 {
   1022 	struct request *rq = cmd->request;
   1023 	blk_status_t ret;
   1024 
   1025 	if (WARN_ON_ONCE(!blk_rq_nr_phys_segments(rq)))
   1026 		return BLK_STS_IOERR;
   1027 
   1028 	ret = scsi_init_sgtable(rq, &cmd->sdb);
   1029 	if (ret)
   1030 		return ret;
   1031 
   1032 	if (blk_integrity_rq(rq)) {
   1033 		struct scsi_data_buffer *prot_sdb = cmd->prot_sdb;
   1034 		int ivecs, count;
   1035 
   1036 		if (WARN_ON_ONCE(!prot_sdb)) {
   1037 			/*
   1038 			 * This can happen if someone (e.g. multipath)
   1039 			 * queues a command to a device on an adapter
   1040 			 * that does not support DIX.
   1041 			 */
   1042 			ret = BLK_STS_IOERR;
   1043 			goto out_free_sgtables;
   1044 		}
   1045 
   1046 		ivecs = blk_rq_count_integrity_sg(rq->q, rq->bio);
   1047 
   1048 		if (sg_alloc_table_chained(&prot_sdb->table, ivecs,
   1049 				prot_sdb->table.sgl)) {
   1050 			ret = BLK_STS_RESOURCE;
   1051 			goto out_free_sgtables;
   1052 		}
   1053 
   1054 		count = blk_rq_map_integrity_sg(rq->q, rq->bio,
   1055 						prot_sdb->table.sgl);
   1056 		BUG_ON(count > ivecs);
   1057 		BUG_ON(count > queue_max_integrity_segments(rq->q));
   1058 
   1059 		cmd->prot_sdb = prot_sdb;
   1060 		cmd->prot_sdb->table.nents = count;
   1061 	}
   1062 
   1063 	return BLK_STS_OK;
   1064 out_free_sgtables:
   1065 	scsi_mq_free_sgtables(cmd);
   1066 	return ret;
   1067 }
   1068 EXPORT_SYMBOL(scsi_init_io);
   1069 
   1070 /**
   1071  * scsi_initialize_rq - initialize struct scsi_cmnd partially
   1072  * @rq: Request associated with the SCSI command to be initialized.
   1073  *
   1074  * This function initializes the members of struct scsi_cmnd that must be
   1075  * initialized before request processing starts and that won't be
   1076  * reinitialized if a SCSI command is requeued.
   1077  *
   1078  * Called from inside blk_get_request() for pass-through requests and from
   1079  * inside scsi_init_command() for filesystem requests.
   1080  */
   1081 static void scsi_initialize_rq(struct request *rq)
   1082 {
   1083 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
   1084 
   1085 	scsi_req_init(&cmd->req);
   1086 	init_rcu_head(&cmd->rcu);
   1087 	cmd->jiffies_at_alloc = jiffies;
   1088 	cmd->retries = 0;
   1089 }
   1090 
   1091 /* Add a command to the list used by the aacraid and dpt_i2o drivers */
   1092 void scsi_add_cmd_to_list(struct scsi_cmnd *cmd)
   1093 {
   1094 	struct scsi_device *sdev = cmd->device;
   1095 	struct Scsi_Host *shost = sdev->host;
   1096 	unsigned long flags;
   1097 
   1098 	if (shost->use_cmd_list) {
   1099 		spin_lock_irqsave(&sdev->list_lock, flags);
   1100 		list_add_tail(&cmd->list, &sdev->cmd_list);
   1101 		spin_unlock_irqrestore(&sdev->list_lock, flags);
   1102 	}
   1103 }
   1104 
   1105 /* Remove a command from the list used by the aacraid and dpt_i2o drivers */
   1106 void scsi_del_cmd_from_list(struct scsi_cmnd *cmd)
   1107 {
   1108 	struct scsi_device *sdev = cmd->device;
   1109 	struct Scsi_Host *shost = sdev->host;
   1110 	unsigned long flags;
   1111 
   1112 	if (shost->use_cmd_list) {
   1113 		spin_lock_irqsave(&sdev->list_lock, flags);
   1114 		BUG_ON(list_empty(&cmd->list));
   1115 		list_del_init(&cmd->list);
   1116 		spin_unlock_irqrestore(&sdev->list_lock, flags);
   1117 	}
   1118 }
   1119 
   1120 /* Called after a request has been started. */
   1121 void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
   1122 {
   1123 	void *buf = cmd->sense_buffer;
   1124 	void *prot = cmd->prot_sdb;
   1125 	struct request *rq = blk_mq_rq_from_pdu(cmd);
   1126 	unsigned int flags = cmd->flags & SCMD_PRESERVED_FLAGS;
   1127 	unsigned long jiffies_at_alloc;
   1128 	int retries;
   1129 
   1130 	if (!blk_rq_is_scsi(rq) && !(flags & SCMD_INITIALIZED)) {
   1131 		flags |= SCMD_INITIALIZED;
   1132 		scsi_initialize_rq(rq);
   1133 	}
   1134 
   1135 	jiffies_at_alloc = cmd->jiffies_at_alloc;
   1136 	retries = cmd->retries;
   1137 	/* zero out the cmd, except for the embedded scsi_request */
   1138 	memset((char *)cmd + sizeof(cmd->req), 0,
   1139 		sizeof(*cmd) - sizeof(cmd->req) + dev->host->hostt->cmd_size);
   1140 
   1141 	cmd->device = dev;
   1142 	cmd->sense_buffer = buf;
   1143 	cmd->prot_sdb = prot;
   1144 	cmd->flags = flags;
   1145 	INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
   1146 	cmd->jiffies_at_alloc = jiffies_at_alloc;
   1147 	cmd->retries = retries;
   1148 
   1149 	scsi_add_cmd_to_list(cmd);
   1150 }
   1151 
   1152 static blk_status_t scsi_setup_scsi_cmnd(struct scsi_device *sdev,
   1153 		struct request *req)
   1154 {
   1155 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
   1156 
   1157 	/*
   1158 	 * Passthrough requests may transfer data, in which case they must
   1159 	 * a bio attached to them.  Or they might contain a SCSI command
   1160 	 * that does not transfer data, in which case they may optionally
   1161 	 * submit a request without an attached bio.
   1162 	 */
   1163 	if (req->bio) {
   1164 		blk_status_t ret = scsi_init_io(cmd);
   1165 		if (unlikely(ret != BLK_STS_OK))
   1166 			return ret;
   1167 	} else {
   1168 		BUG_ON(blk_rq_bytes(req));
   1169 
   1170 		memset(&cmd->sdb, 0, sizeof(cmd->sdb));
   1171 	}
   1172 
   1173 	cmd->cmd_len = scsi_req(req)->cmd_len;
   1174 	cmd->cmnd = scsi_req(req)->cmd;
   1175 	cmd->transfersize = blk_rq_bytes(req);
   1176 	cmd->allowed = scsi_req(req)->retries;
   1177 	return BLK_STS_OK;
   1178 }
   1179 
   1180 /*
   1181  * Setup a normal block command.  These are simple request from filesystems
   1182  * that still need to be translated to SCSI CDBs from the ULD.
   1183  */
   1184 static blk_status_t scsi_setup_fs_cmnd(struct scsi_device *sdev,
   1185 		struct request *req)
   1186 {
   1187 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
   1188 
   1189 	if (unlikely(sdev->handler && sdev->handler->prep_fn)) {
   1190 		blk_status_t ret = sdev->handler->prep_fn(sdev, req);
   1191 		if (ret != BLK_STS_OK)
   1192 			return ret;
   1193 	}
   1194 
   1195 	cmd->cmnd = scsi_req(req)->cmd = scsi_req(req)->__cmd;
   1196 	memset(cmd->cmnd, 0, BLK_MAX_CDB);
   1197 	return scsi_cmd_to_driver(cmd)->init_command(cmd);
   1198 }
   1199 
   1200 static blk_status_t scsi_setup_cmnd(struct scsi_device *sdev,
   1201 		struct request *req)
   1202 {
   1203 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
   1204 
   1205 	if (!blk_rq_bytes(req))
   1206 		cmd->sc_data_direction = DMA_NONE;
   1207 	else if (rq_data_dir(req) == WRITE)
   1208 		cmd->sc_data_direction = DMA_TO_DEVICE;
   1209 	else
   1210 		cmd->sc_data_direction = DMA_FROM_DEVICE;
   1211 
   1212 	if (blk_rq_is_scsi(req))
   1213 		return scsi_setup_scsi_cmnd(sdev, req);
   1214 	else
   1215 		return scsi_setup_fs_cmnd(sdev, req);
   1216 }
   1217 
   1218 static blk_status_t
   1219 scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
   1220 {
   1221 	switch (sdev->sdev_state) {
   1222 	case SDEV_OFFLINE:
   1223 	case SDEV_TRANSPORT_OFFLINE:
   1224 		/*
   1225 		 * If the device is offline we refuse to process any
   1226 		 * commands.  The device must be brought online
   1227 		 * before trying any recovery commands.
   1228 		 */
   1229 		sdev_printk(KERN_ERR, sdev,
   1230 			    "rejecting I/O to offline device\n");
   1231 		return BLK_STS_IOERR;
   1232 	case SDEV_DEL:
   1233 		/*
   1234 		 * If the device is fully deleted, we refuse to
   1235 		 * process any commands as well.
   1236 		 */
   1237 		sdev_printk(KERN_ERR, sdev,
   1238 			    "rejecting I/O to dead device\n");
   1239 		return BLK_STS_IOERR;
   1240 	case SDEV_BLOCK:
   1241 	case SDEV_CREATED_BLOCK:
   1242 		return BLK_STS_RESOURCE;
   1243 	case SDEV_QUIESCE:
   1244 		/*
   1245 		 * If the devices is blocked we defer normal commands.
   1246 		 */
   1247 		if (req && !(req->rq_flags & RQF_PREEMPT))
   1248 			return BLK_STS_RESOURCE;
   1249 		return BLK_STS_OK;
   1250 	default:
   1251 		/*
   1252 		 * For any other not fully online state we only allow
   1253 		 * special commands.  In particular any user initiated
   1254 		 * command is not allowed.
   1255 		 */
   1256 		if (req && !(req->rq_flags & RQF_PREEMPT))
   1257 			return BLK_STS_IOERR;
   1258 		return BLK_STS_OK;
   1259 	}
   1260 }
   1261 
   1262 /*
   1263  * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
   1264  * return 0.
   1265  *
   1266  * Called with the queue_lock held.
   1267  */
   1268 static inline int scsi_dev_queue_ready(struct request_queue *q,
   1269 				  struct scsi_device *sdev)
   1270 {
   1271 	unsigned int busy;
   1272 
   1273 	busy = atomic_inc_return(&sdev->device_busy) - 1;
   1274 	if (atomic_read(&sdev->device_blocked)) {
   1275 		if (busy)
   1276 			goto out_dec;
   1277 
   1278 		/*
   1279 		 * unblock after device_blocked iterates to zero
   1280 		 */
   1281 		if (atomic_dec_return(&sdev->device_blocked) > 0)
   1282 			goto out_dec;
   1283 		SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
   1284 				   "unblocking device at zero depth\n"));
   1285 	}
   1286 
   1287 	if (busy >= sdev->queue_depth)
   1288 		goto out_dec;
   1289 
   1290 	return 1;
   1291 out_dec:
   1292 	atomic_dec(&sdev->device_busy);
   1293 	return 0;
   1294 }
   1295 
   1296 /*
   1297  * scsi_target_queue_ready: checks if there we can send commands to target
   1298  * @sdev: scsi device on starget to check.
   1299  */
   1300 static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
   1301 					   struct scsi_device *sdev)
   1302 {
   1303 	struct scsi_target *starget = scsi_target(sdev);
   1304 	unsigned int busy;
   1305 
   1306 	if (starget->single_lun) {
   1307 		spin_lock_irq(shost->host_lock);
   1308 		if (starget->starget_sdev_user &&
   1309 		    starget->starget_sdev_user != sdev) {
   1310 			spin_unlock_irq(shost->host_lock);
   1311 			return 0;
   1312 		}
   1313 		starget->starget_sdev_user = sdev;
   1314 		spin_unlock_irq(shost->host_lock);
   1315 	}
   1316 
   1317 	if (starget->can_queue <= 0)
   1318 		return 1;
   1319 
   1320 	busy = atomic_inc_return(&starget->target_busy) - 1;
   1321 	if (atomic_read(&starget->target_blocked) > 0) {
   1322 		if (busy)
   1323 			goto starved;
   1324 
   1325 		/*
   1326 		 * unblock after target_blocked iterates to zero
   1327 		 */
   1328 		if (atomic_dec_return(&starget->target_blocked) > 0)
   1329 			goto out_dec;
   1330 
   1331 		SCSI_LOG_MLQUEUE(3, starget_printk(KERN_INFO, starget,
   1332 				 "unblocking target at zero depth\n"));
   1333 	}
   1334 
   1335 	if (busy >= starget->can_queue)
   1336 		goto starved;
   1337 
   1338 	return 1;
   1339 
   1340 starved:
   1341 	spin_lock_irq(shost->host_lock);
   1342 	list_move_tail(&sdev->starved_entry, &shost->starved_list);
   1343 	spin_unlock_irq(shost->host_lock);
   1344 out_dec:
   1345 	if (starget->can_queue > 0)
   1346 		atomic_dec(&starget->target_busy);
   1347 	return 0;
   1348 }
   1349 
   1350 /*
   1351  * scsi_host_queue_ready: if we can send requests to shost, return 1 else
   1352  * return 0. We must end up running the queue again whenever 0 is
   1353  * returned, else IO can hang.
   1354  */
   1355 static inline int scsi_host_queue_ready(struct request_queue *q,
   1356 				   struct Scsi_Host *shost,
   1357 				   struct scsi_device *sdev)
   1358 {
   1359 	unsigned int busy;
   1360 
   1361 	if (scsi_host_in_recovery(shost))
   1362 		return 0;
   1363 
   1364 	busy = atomic_inc_return(&shost->host_busy) - 1;
   1365 	if (atomic_read(&shost->host_blocked) > 0) {
   1366 		if (busy)
   1367 			goto starved;
   1368 
   1369 		/*
   1370 		 * unblock after host_blocked iterates to zero
   1371 		 */
   1372 		if (atomic_dec_return(&shost->host_blocked) > 0)
   1373 			goto out_dec;
   1374 
   1375 		SCSI_LOG_MLQUEUE(3,
   1376 			shost_printk(KERN_INFO, shost,
   1377 				     "unblocking host at zero depth\n"));
   1378 	}
   1379 
   1380 	if (shost->can_queue > 0 && busy >= shost->can_queue)
   1381 		goto starved;
   1382 	if (shost->host_self_blocked)
   1383 		goto starved;
   1384 
   1385 	/* We're OK to process the command, so we can't be starved */
   1386 	if (!list_empty(&sdev->starved_entry)) {
   1387 		spin_lock_irq(shost->host_lock);
   1388 		if (!list_empty(&sdev->starved_entry))
   1389 			list_del_init(&sdev->starved_entry);
   1390 		spin_unlock_irq(shost->host_lock);
   1391 	}
   1392 
   1393 	return 1;
   1394 
   1395 starved:
   1396 	spin_lock_irq(shost->host_lock);
   1397 	if (list_empty(&sdev->starved_entry))
   1398 		list_add_tail(&sdev->starved_entry, &shost->starved_list);
   1399 	spin_unlock_irq(shost->host_lock);
   1400 out_dec:
   1401 	scsi_dec_host_busy(shost);
   1402 	return 0;
   1403 }
   1404 
   1405 /*
   1406  * Busy state exporting function for request stacking drivers.
   1407  *
   1408  * For efficiency, no lock is taken to check the busy state of
   1409  * shost/starget/sdev, since the returned value is not guaranteed and
   1410  * may be changed after request stacking drivers call the function,
   1411  * regardless of taking lock or not.
   1412  *
   1413  * When scsi can't dispatch I/Os anymore and needs to kill I/Os scsi
   1414  * needs to return 'not busy'. Otherwise, request stacking drivers
   1415  * may hold requests forever.
   1416  */
   1417 static bool scsi_mq_lld_busy(struct request_queue *q)
   1418 {
   1419 	struct scsi_device *sdev = q->queuedata;
   1420 	struct Scsi_Host *shost;
   1421 
   1422 	if (blk_queue_dying(q))
   1423 		return false;
   1424 
   1425 	shost = sdev->host;
   1426 
   1427 	/*
   1428 	 * Ignore host/starget busy state.
   1429 	 * Since block layer does not have a concept of fairness across
   1430 	 * multiple queues, congestion of host/starget needs to be handled
   1431 	 * in SCSI layer.
   1432 	 */
   1433 	if (scsi_host_in_recovery(shost) || scsi_device_is_busy(sdev))
   1434 		return true;
   1435 
   1436 	return false;
   1437 }
   1438 
   1439 static void scsi_softirq_done(struct request *rq)
   1440 {
   1441 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
   1442 	unsigned long wait_for = (cmd->allowed + 1) * rq->timeout;
   1443 	int disposition;
   1444 
   1445 	INIT_LIST_HEAD(&cmd->eh_entry);
   1446 
   1447 	atomic_inc(&cmd->device->iodone_cnt);
   1448 	if (cmd->result)
   1449 		atomic_inc(&cmd->device->ioerr_cnt);
   1450 
   1451 	disposition = scsi_decide_disposition(cmd);
   1452 	if (disposition != SUCCESS &&
   1453 	    time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
   1454 		sdev_printk(KERN_ERR, cmd->device,
   1455 			    "timing out command, waited %lus\n",
   1456 			    wait_for/HZ);
   1457 		disposition = SUCCESS;
   1458 	}
   1459 
   1460 	scsi_log_completion(cmd, disposition);
   1461 
   1462 	switch (disposition) {
   1463 		case SUCCESS:
   1464 			scsi_finish_command(cmd);
   1465 			break;
   1466 		case NEEDS_RETRY:
   1467 			scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY);
   1468 			break;
   1469 		case ADD_TO_MLQUEUE:
   1470 			scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
   1471 			break;
   1472 		default:
   1473 			scsi_eh_scmd_add(cmd);
   1474 			break;
   1475 	}
   1476 }
   1477 
   1478 /**
   1479  * scsi_dispatch_command - Dispatch a command to the low-level driver.
   1480  * @cmd: command block we are dispatching.
   1481  *
   1482  * Return: nonzero return request was rejected and device's queue needs to be
   1483  * plugged.
   1484  */
   1485 static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
   1486 {
   1487 	struct Scsi_Host *host = cmd->device->host;
   1488 	int rtn = 0;
   1489 
   1490 	atomic_inc(&cmd->device->iorequest_cnt);
   1491 
   1492 	/* check if the device is still usable */
   1493 	if (unlikely(cmd->device->sdev_state == SDEV_DEL)) {
   1494 		/* in SDEV_DEL we error all commands. DID_NO_CONNECT
   1495 		 * returns an immediate error upwards, and signals
   1496 		 * that the device is no longer present */
   1497 		cmd->result = DID_NO_CONNECT << 16;
   1498 		goto done;
   1499 	}
   1500 
   1501 	/* Check to see if the scsi lld made this device blocked. */
   1502 	if (unlikely(scsi_device_blocked(cmd->device))) {
   1503 		/*
   1504 		 * in blocked state, the command is just put back on
   1505 		 * the device queue.  The suspend state has already
   1506 		 * blocked the queue so future requests should not
   1507 		 * occur until the device transitions out of the
   1508 		 * suspend state.
   1509 		 */
   1510 		SCSI_LOG_MLQUEUE(3, scmd_printk(KERN_INFO, cmd,
   1511 			"queuecommand : device blocked\n"));
   1512 		return SCSI_MLQUEUE_DEVICE_BUSY;
   1513 	}
   1514 
   1515 	/* Store the LUN value in cmnd, if needed. */
   1516 	if (cmd->device->lun_in_cdb)
   1517 		cmd->cmnd[1] = (cmd->cmnd[1] & 0x1f) |
   1518 			       (cmd->device->lun << 5 & 0xe0);
   1519 
   1520 	scsi_log_send(cmd);
   1521 
   1522 	/*
   1523 	 * Before we queue this command, check if the command
   1524 	 * length exceeds what the host adapter can handle.
   1525 	 */
   1526 	if (cmd->cmd_len > cmd->device->host->max_cmd_len) {
   1527 		SCSI_LOG_MLQUEUE(3, scmd_printk(KERN_INFO, cmd,
   1528 			       "queuecommand : command too long. "
   1529 			       "cdb_size=%d host->max_cmd_len=%d\n",
   1530 			       cmd->cmd_len, cmd->device->host->max_cmd_len));
   1531 		cmd->result = (DID_ABORT << 16);
   1532 		goto done;
   1533 	}
   1534 
   1535 	if (unlikely(host->shost_state == SHOST_DEL)) {
   1536 		cmd->result = (DID_NO_CONNECT << 16);
   1537 		goto done;
   1538 
   1539 	}
   1540 
   1541 	trace_scsi_dispatch_cmd_start(cmd);
   1542 	rtn = host->hostt->queuecommand(host, cmd);
   1543 	if (rtn) {
   1544 		trace_scsi_dispatch_cmd_error(cmd, rtn);
   1545 		if (rtn != SCSI_MLQUEUE_DEVICE_BUSY &&
   1546 		    rtn != SCSI_MLQUEUE_TARGET_BUSY)
   1547 			rtn = SCSI_MLQUEUE_HOST_BUSY;
   1548 
   1549 		SCSI_LOG_MLQUEUE(3, scmd_printk(KERN_INFO, cmd,
   1550 			"queuecommand : request rejected\n"));
   1551 	}
   1552 
   1553 	return rtn;
   1554  done:
   1555 	cmd->scsi_done(cmd);
   1556 	return 0;
   1557 }
   1558 
   1559 /* Size in bytes of the sg-list stored in the scsi-mq command-private data. */
   1560 static unsigned int scsi_mq_sgl_size(struct Scsi_Host *shost)
   1561 {
   1562 	return min_t(unsigned int, shost->sg_tablesize, SG_CHUNK_SIZE) *
   1563 		sizeof(struct scatterlist);
   1564 }
   1565 
   1566 static blk_status_t scsi_mq_prep_fn(struct request *req)
   1567 {
   1568 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
   1569 	struct scsi_device *sdev = req->q->queuedata;
   1570 	struct Scsi_Host *shost = sdev->host;
   1571 	struct scatterlist *sg;
   1572 
   1573 	scsi_init_command(sdev, cmd);
   1574 
   1575 	cmd->request = req;
   1576 	cmd->tag = req->tag;
   1577 	cmd->prot_op = SCSI_PROT_NORMAL;
   1578 
   1579 	sg = (void *)cmd + sizeof(struct scsi_cmnd) + shost->hostt->cmd_size;
   1580 	cmd->sdb.table.sgl = sg;
   1581 
   1582 	if (scsi_host_get_prot(shost)) {
   1583 		memset(cmd->prot_sdb, 0, sizeof(struct scsi_data_buffer));
   1584 
   1585 		cmd->prot_sdb->table.sgl =
   1586 			(struct scatterlist *)(cmd->prot_sdb + 1);
   1587 	}
   1588 
   1589 	blk_mq_start_request(req);
   1590 
   1591 	return scsi_setup_cmnd(sdev, req);
   1592 }
   1593 
   1594 static void scsi_mq_done(struct scsi_cmnd *cmd)
   1595 {
   1596 	if (unlikely(test_and_set_bit(SCMD_STATE_COMPLETE, &cmd->state)))
   1597 		return;
   1598 	trace_scsi_dispatch_cmd_done(cmd);
   1599 
   1600 	/*
   1601 	 * If the block layer didn't complete the request due to a timeout
   1602 	 * injection, scsi must clear its internal completed state so that the
   1603 	 * timeout handler will see it needs to escalate its own error
   1604 	 * recovery.
   1605 	 */
   1606 	if (unlikely(!blk_mq_complete_request(cmd->request)))
   1607 		clear_bit(SCMD_STATE_COMPLETE, &cmd->state);
   1608 }
   1609 
   1610 static void scsi_mq_put_budget(struct blk_mq_hw_ctx *hctx)
   1611 {
   1612 	struct request_queue *q = hctx->queue;
   1613 	struct scsi_device *sdev = q->queuedata;
   1614 
   1615 	atomic_dec(&sdev->device_busy);
   1616 	put_device(&sdev->sdev_gendev);
   1617 }
   1618 
   1619 static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx)
   1620 {
   1621 	struct request_queue *q = hctx->queue;
   1622 	struct scsi_device *sdev = q->queuedata;
   1623 
   1624 	if (!get_device(&sdev->sdev_gendev))
   1625 		goto out;
   1626 	if (!scsi_dev_queue_ready(q, sdev))
   1627 		goto out_put_device;
   1628 
   1629 	return true;
   1630 
   1631 out_put_device:
   1632 	put_device(&sdev->sdev_gendev);
   1633 out:
   1634 	if (atomic_read(&sdev->device_busy) == 0 && !scsi_device_blocked(sdev))
   1635 		blk_mq_delay_run_hw_queue(hctx, SCSI_QUEUE_DELAY);
   1636 	return false;
   1637 }
   1638 
   1639 static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
   1640 			 const struct blk_mq_queue_data *bd)
   1641 {
   1642 	struct request *req = bd->rq;
   1643 	struct request_queue *q = req->q;
   1644 	struct scsi_device *sdev = q->queuedata;
   1645 	struct Scsi_Host *shost = sdev->host;
   1646 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
   1647 	blk_status_t ret;
   1648 	int reason;
   1649 
   1650 	/*
   1651 	 * If the device is not in running state we will reject some or all
   1652 	 * commands.
   1653 	 */
   1654 	if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
   1655 		ret = scsi_prep_state_check(sdev, req);
   1656 		if (ret != BLK_STS_OK)
   1657 			goto out_put_budget;
   1658 	}
   1659 
   1660 	ret = BLK_STS_RESOURCE;
   1661 	if (!scsi_target_queue_ready(shost, sdev))
   1662 		goto out_put_budget;
   1663 	if (!scsi_host_queue_ready(q, shost, sdev))
   1664 		goto out_dec_target_busy;
   1665 
   1666 	if (!(req->rq_flags & RQF_DONTPREP)) {
   1667 		ret = scsi_mq_prep_fn(req);
   1668 		if (ret != BLK_STS_OK)
   1669 			goto out_dec_host_busy;
   1670 		req->rq_flags |= RQF_DONTPREP;
   1671 	} else {
   1672 		clear_bit(SCMD_STATE_COMPLETE, &cmd->state);
   1673 		blk_mq_start_request(req);
   1674 	}
   1675 
   1676 	if (sdev->simple_tags)
   1677 		cmd->flags |= SCMD_TAGGED;
   1678 	else
   1679 		cmd->flags &= ~SCMD_TAGGED;
   1680 
   1681 	scsi_init_cmd_errh(cmd);
   1682 	cmd->scsi_done = scsi_mq_done;
   1683 
   1684 	reason = scsi_dispatch_cmd(cmd);
   1685 	if (reason) {
   1686 		scsi_set_blocked(cmd, reason);
   1687 		ret = BLK_STS_RESOURCE;
   1688 		goto out_dec_host_busy;
   1689 	}
   1690 
   1691 	return BLK_STS_OK;
   1692 
   1693 out_dec_host_busy:
   1694 	scsi_dec_host_busy(shost);
   1695 out_dec_target_busy:
   1696 	if (scsi_target(sdev)->can_queue > 0)
   1697 		atomic_dec(&scsi_target(sdev)->target_busy);
   1698 out_put_budget:
   1699 	scsi_mq_put_budget(hctx);
   1700 	switch (ret) {
   1701 	case BLK_STS_OK:
   1702 		break;
   1703 	case BLK_STS_RESOURCE:
   1704 		if (atomic_read(&sdev->device_busy) ||
   1705 		    scsi_device_blocked(sdev))
   1706 			ret = BLK_STS_DEV_RESOURCE;
   1707 		break;
   1708 	default:
   1709 		if (unlikely(!scsi_device_online(sdev)))
   1710 			scsi_req(req)->result = DID_NO_CONNECT << 16;
   1711 		else
   1712 			scsi_req(req)->result = DID_ERROR << 16;
   1713 		/*
   1714 		 * Make sure to release all allocated resources when
   1715 		 * we hit an error, as we will never see this command
   1716 		 * again.
   1717 		 */
   1718 		if (req->rq_flags & RQF_DONTPREP)
   1719 			scsi_mq_uninit_cmd(cmd);
   1720 		break;
   1721 	}
   1722 	return ret;
   1723 }
   1724 
   1725 static enum blk_eh_timer_return scsi_timeout(struct request *req,
   1726 		bool reserved)
   1727 {
   1728 	if (reserved)
   1729 		return BLK_EH_RESET_TIMER;
   1730 	return scsi_times_out(req);
   1731 }
   1732 
   1733 static int scsi_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
   1734 				unsigned int hctx_idx, unsigned int numa_node)
   1735 {
   1736 	struct Scsi_Host *shost = set->driver_data;
   1737 	const bool unchecked_isa_dma = shost->unchecked_isa_dma;
   1738 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
   1739 	struct scatterlist *sg;
   1740 
   1741 	if (unchecked_isa_dma)
   1742 		cmd->flags |= SCMD_UNCHECKED_ISA_DMA;
   1743 	cmd->sense_buffer = scsi_alloc_sense_buffer(unchecked_isa_dma,
   1744 						    GFP_KERNEL, numa_node);
   1745 	if (!cmd->sense_buffer)
   1746 		return -ENOMEM;
   1747 	cmd->req.sense = cmd->sense_buffer;
   1748 
   1749 	if (scsi_host_get_prot(shost)) {
   1750 		sg = (void *)cmd + sizeof(struct scsi_cmnd) +
   1751 			shost->hostt->cmd_size;
   1752 		cmd->prot_sdb = (void *)sg + scsi_mq_sgl_size(shost);
   1753 	}
   1754 
   1755 	return 0;
   1756 }
   1757 
   1758 static void scsi_mq_exit_request(struct blk_mq_tag_set *set, struct request *rq,
   1759 				 unsigned int hctx_idx)
   1760 {
   1761 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
   1762 
   1763 	scsi_free_sense_buffer(cmd->flags & SCMD_UNCHECKED_ISA_DMA,
   1764 			       cmd->sense_buffer);
   1765 }
   1766 
   1767 static int scsi_map_queues(struct blk_mq_tag_set *set)
   1768 {
   1769 	struct Scsi_Host *shost = container_of(set, struct Scsi_Host, tag_set);
   1770 
   1771 	if (shost->hostt->map_queues)
   1772 		return shost->hostt->map_queues(shost);
   1773 	return blk_mq_map_queues(&set->map[0]);
   1774 }
   1775 
   1776 void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
   1777 {
   1778 	struct device *dev = shost->dma_dev;
   1779 
   1780 	/*
   1781 	 * this limit is imposed by hardware restrictions
   1782 	 */
   1783 	blk_queue_max_segments(q, min_t(unsigned short, shost->sg_tablesize,
   1784 					SG_MAX_SEGMENTS));
   1785 
   1786 	if (scsi_host_prot_dma(shost)) {
   1787 		shost->sg_prot_tablesize =
   1788 			min_not_zero(shost->sg_prot_tablesize,
   1789 				     (unsigned short)SCSI_MAX_PROT_SG_SEGMENTS);
   1790 		BUG_ON(shost->sg_prot_tablesize < shost->sg_tablesize);
   1791 		blk_queue_max_integrity_segments(q, shost->sg_prot_tablesize);
   1792 	}
   1793 
   1794 	blk_queue_max_hw_sectors(q, shost->max_sectors);
   1795 	if (shost->unchecked_isa_dma)
   1796 		blk_queue_bounce_limit(q, BLK_BOUNCE_ISA);
   1797 	blk_queue_segment_boundary(q, shost->dma_boundary);
   1798 	dma_set_seg_boundary(dev, shost->dma_boundary);
   1799 
   1800 	blk_queue_max_segment_size(q, shost->max_segment_size);
   1801 	dma_set_max_seg_size(dev, shost->max_segment_size);
   1802 
   1803 	/*
   1804 	 * Set a reasonable default alignment:  The larger of 32-byte (dword),
   1805 	 * which is a common minimum for HBAs, and the minimum DMA alignment,
   1806 	 * which is set by the platform.
   1807 	 *
   1808 	 * Devices that require a bigger alignment can increase it later.
   1809 	 */
   1810 	blk_queue_dma_alignment(q, max(4, dma_get_cache_alignment()) - 1);
   1811 }
   1812 EXPORT_SYMBOL_GPL(__scsi_init_queue);
   1813 
   1814 static const struct blk_mq_ops scsi_mq_ops = {
   1815 	.get_budget	= scsi_mq_get_budget,
   1816 	.put_budget	= scsi_mq_put_budget,
   1817 	.queue_rq	= scsi_queue_rq,
   1818 	.complete	= scsi_softirq_done,
   1819 	.timeout	= scsi_timeout,
   1820 #ifdef CONFIG_BLK_DEBUG_FS
   1821 	.show_rq	= scsi_show_rq,
   1822 #endif
   1823 	.init_request	= scsi_mq_init_request,
   1824 	.exit_request	= scsi_mq_exit_request,
   1825 	.initialize_rq_fn = scsi_initialize_rq,
   1826 	.busy		= scsi_mq_lld_busy,
   1827 	.map_queues	= scsi_map_queues,
   1828 };
   1829 
   1830 struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev)
   1831 {
   1832 	sdev->request_queue = blk_mq_init_queue(&sdev->host->tag_set);
   1833 	if (IS_ERR(sdev->request_queue))
   1834 		return NULL;
   1835 
   1836 	sdev->request_queue->queuedata = sdev;
   1837 	__scsi_init_queue(sdev->host, sdev->request_queue);
   1838 	blk_queue_flag_set(QUEUE_FLAG_SCSI_PASSTHROUGH, sdev->request_queue);
   1839 	return sdev->request_queue;
   1840 }
   1841 
   1842 int scsi_mq_setup_tags(struct Scsi_Host *shost)
   1843 {
   1844 	unsigned int cmd_size, sgl_size;
   1845 
   1846 	sgl_size = scsi_mq_sgl_size(shost);
   1847 	cmd_size = sizeof(struct scsi_cmnd) + shost->hostt->cmd_size + sgl_size;
   1848 	if (scsi_host_get_prot(shost))
   1849 		cmd_size += sizeof(struct scsi_data_buffer) + sgl_size;
   1850 
   1851 	memset(&shost->tag_set, 0, sizeof(shost->tag_set));
   1852 	shost->tag_set.ops = &scsi_mq_ops;
   1853 	shost->tag_set.nr_hw_queues = shost->nr_hw_queues ? : 1;
   1854 	shost->tag_set.queue_depth = shost->can_queue;
   1855 	shost->tag_set.cmd_size = cmd_size;
   1856 	shost->tag_set.numa_node = NUMA_NO_NODE;
   1857 	shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
   1858 	shost->tag_set.flags |=
   1859 		BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
   1860 	shost->tag_set.driver_data = shost;
   1861 
   1862 	return blk_mq_alloc_tag_set(&shost->tag_set);
   1863 }
   1864 
   1865 void scsi_mq_destroy_tags(struct Scsi_Host *shost)
   1866 {
   1867 	blk_mq_free_tag_set(&shost->tag_set);
   1868 }
   1869 
   1870 /**
   1871  * scsi_device_from_queue - return sdev associated with a request_queue
   1872  * @q: The request queue to return the sdev from
   1873  *
   1874  * Return the sdev associated with a request queue or NULL if the
   1875  * request_queue does not reference a SCSI device.
   1876  */
   1877 struct scsi_device *scsi_device_from_queue(struct request_queue *q)
   1878 {
   1879 	struct scsi_device *sdev = NULL;
   1880 
   1881 	if (q->mq_ops == &scsi_mq_ops)
   1882 		sdev = q->queuedata;
   1883 	if (!sdev || !get_device(&sdev->sdev_gendev))
   1884 		sdev = NULL;
   1885 
   1886 	return sdev;
   1887 }
   1888 EXPORT_SYMBOL_GPL(scsi_device_from_queue);
   1889 
   1890 /*
   1891  * Function:    scsi_block_requests()
   1892  *
   1893  * Purpose:     Utility function used by low-level drivers to prevent further
   1894  *		commands from being queued to the device.
   1895  *
   1896  * Arguments:   shost       - Host in question
   1897  *
   1898  * Returns:     Nothing
   1899  *
   1900  * Lock status: No locks are assumed held.
   1901  *
   1902  * Notes:       There is no timer nor any other means by which the requests
   1903  *		get unblocked other than the low-level driver calling
   1904  *		scsi_unblock_requests().
   1905  */
   1906 void scsi_block_requests(struct Scsi_Host *shost)
   1907 {
   1908 	shost->host_self_blocked = 1;
   1909 }
   1910 EXPORT_SYMBOL(scsi_block_requests);
   1911 
   1912 /*
   1913  * Function:    scsi_unblock_requests()
   1914  *
   1915  * Purpose:     Utility function used by low-level drivers to allow further
   1916  *		commands from being queued to the device.
   1917  *
   1918  * Arguments:   shost       - Host in question
   1919  *
   1920  * Returns:     Nothing
   1921  *
   1922  * Lock status: No locks are assumed held.
   1923  *
   1924  * Notes:       There is no timer nor any other means by which the requests
   1925  *		get unblocked other than the low-level driver calling
   1926  *		scsi_unblock_requests().
   1927  *
   1928  *		This is done as an API function so that changes to the
   1929  *		internals of the scsi mid-layer won't require wholesale
   1930  *		changes to drivers that use this feature.
   1931  */
   1932 void scsi_unblock_requests(struct Scsi_Host *shost)
   1933 {
   1934 	shost->host_self_blocked = 0;
   1935 	scsi_run_host_queues(shost);
   1936 }
   1937 EXPORT_SYMBOL(scsi_unblock_requests);
   1938 
   1939 int __init scsi_init_queue(void)
   1940 {
   1941 	scsi_sdb_cache = kmem_cache_create("scsi_data_buffer",
   1942 					   sizeof(struct scsi_data_buffer),
   1943 					   0, 0, NULL);
   1944 	if (!scsi_sdb_cache) {
   1945 		printk(KERN_ERR "SCSI: can't init scsi sdb cache\n");
   1946 		return -ENOMEM;
   1947 	}
   1948 
   1949 	return 0;
   1950 }
   1951 
   1952 void scsi_exit_queue(void)
   1953 {
   1954 	kmem_cache_destroy(scsi_sense_cache);
   1955 	kmem_cache_destroy(scsi_sense_isadma_cache);
   1956 	kmem_cache_destroy(scsi_sdb_cache);
   1957 }
   1958 
   1959 /**
   1960  *	scsi_mode_select - issue a mode select
   1961  *	@sdev:	SCSI device to be queried
   1962  *	@pf:	Page format bit (1 == standard, 0 == vendor specific)
   1963  *	@sp:	Save page bit (0 == don't save, 1 == save)
   1964  *	@modepage: mode page being requested
   1965  *	@buffer: request buffer (may not be smaller than eight bytes)
   1966  *	@len:	length of request buffer.
   1967  *	@timeout: command timeout
   1968  *	@retries: number of retries before failing
   1969  *	@data: returns a structure abstracting the mode header data
   1970  *	@sshdr: place to put sense data (or NULL if no sense to be collected).
   1971  *		must be SCSI_SENSE_BUFFERSIZE big.
   1972  *
   1973  *	Returns zero if successful; negative error number or scsi
   1974  *	status on error
   1975  *
   1976  */
   1977 int
   1978 scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
   1979 		 unsigned char *buffer, int len, int timeout, int retries,
   1980 		 struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
   1981 {
   1982 	unsigned char cmd[10];
   1983 	unsigned char *real_buffer;
   1984 	int ret;
   1985 
   1986 	memset(cmd, 0, sizeof(cmd));
   1987 	cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
   1988 
   1989 	if (sdev->use_10_for_ms) {
   1990 		if (len > 65535)
   1991 			return -EINVAL;
   1992 		real_buffer = kmalloc(8 + len, GFP_KERNEL);
   1993 		if (!real_buffer)
   1994 			return -ENOMEM;
   1995 		memcpy(real_buffer + 8, buffer, len);
   1996 		len += 8;
   1997 		real_buffer[0] = 0;
   1998 		real_buffer[1] = 0;
   1999 		real_buffer[2] = data->medium_type;
   2000 		real_buffer[3] = data->device_specific;
   2001 		real_buffer[4] = data->longlba ? 0x01 : 0;
   2002 		real_buffer[5] = 0;
   2003 		real_buffer[6] = data->block_descriptor_length >> 8;
   2004 		real_buffer[7] = data->block_descriptor_length;
   2005 
   2006 		cmd[0] = MODE_SELECT_10;
   2007 		cmd[7] = len >> 8;
   2008 		cmd[8] = len;
   2009 	} else {
   2010 		if (len > 255 || data->block_descriptor_length > 255 ||
   2011 		    data->longlba)
   2012 			return -EINVAL;
   2013 
   2014 		real_buffer = kmalloc(4 + len, GFP_KERNEL);
   2015 		if (!real_buffer)
   2016 			return -ENOMEM;
   2017 		memcpy(real_buffer + 4, buffer, len);
   2018 		len += 4;
   2019 		real_buffer[0] = 0;
   2020 		real_buffer[1] = data->medium_type;
   2021 		real_buffer[2] = data->device_specific;
   2022 		real_buffer[3] = data->block_descriptor_length;
   2023 		
   2024 
   2025 		cmd[0] = MODE_SELECT;
   2026 		cmd[4] = len;
   2027 	}
   2028 
   2029 	ret = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, real_buffer, len,
   2030 			       sshdr, timeout, retries, NULL);
   2031 	kfree(real_buffer);
   2032 	return ret;
   2033 }
   2034 EXPORT_SYMBOL_GPL(scsi_mode_select);
   2035 
   2036 /**
   2037  *	scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
   2038  *	@sdev:	SCSI device to be queried
   2039  *	@dbd:	set if mode sense will allow block descriptors to be returned
   2040  *	@modepage: mode page being requested
   2041  *	@buffer: request buffer (may not be smaller than eight bytes)
   2042  *	@len:	length of request buffer.
   2043  *	@timeout: command timeout
   2044  *	@retries: number of retries before failing
   2045  *	@data: returns a structure abstracting the mode header data
   2046  *	@sshdr: place to put sense data (or NULL if no sense to be collected).
   2047  *		must be SCSI_SENSE_BUFFERSIZE big.
   2048  *
   2049  *	Returns zero if unsuccessful, or the header offset (either 4
   2050  *	or 8 depending on whether a six or ten byte command was
   2051  *	issued) if successful.
   2052  */
   2053 int
   2054 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
   2055 		  unsigned char *buffer, int len, int timeout, int retries,
   2056 		  struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
   2057 {
   2058 	unsigned char cmd[12];
   2059 	int use_10_for_ms;
   2060 	int header_length;
   2061 	int result, retry_count = retries;
   2062 	struct scsi_sense_hdr my_sshdr;
   2063 
   2064 	memset(data, 0, sizeof(*data));
   2065 	memset(&cmd[0], 0, 12);
   2066 	cmd[1] = dbd & 0x18;	/* allows DBD and LLBA bits */
   2067 	cmd[2] = modepage;
   2068 
   2069 	/* caller might not be interested in sense, but we need it */
   2070 	if (!sshdr)
   2071 		sshdr = &my_sshdr;
   2072 
   2073  retry:
   2074 	use_10_for_ms = sdev->use_10_for_ms;
   2075 
   2076 	if (use_10_for_ms) {
   2077 		if (len < 8)
   2078 			len = 8;
   2079 
   2080 		cmd[0] = MODE_SENSE_10;
   2081 		cmd[8] = len;
   2082 		header_length = 8;
   2083 	} else {
   2084 		if (len < 4)
   2085 			len = 4;
   2086 
   2087 		cmd[0] = MODE_SENSE;
   2088 		cmd[4] = len;
   2089 		header_length = 4;
   2090 	}
   2091 
   2092 	memset(buffer, 0, len);
   2093 
   2094 	result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
   2095 				  sshdr, timeout, retries, NULL);
   2096 
   2097 	/* This code looks awful: what it's doing is making sure an
   2098 	 * ILLEGAL REQUEST sense return identifies the actual command
   2099 	 * byte as the problem.  MODE_SENSE commands can return
   2100 	 * ILLEGAL REQUEST if the code page isn't supported */
   2101 
   2102 	if (use_10_for_ms && !scsi_status_is_good(result) &&
   2103 	    driver_byte(result) == DRIVER_SENSE) {
   2104 		if (scsi_sense_valid(sshdr)) {
   2105 			if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
   2106 			    (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
   2107 				/* 
   2108 				 * Invalid command operation code
   2109 				 */
   2110 				sdev->use_10_for_ms = 0;
   2111 				goto retry;
   2112 			}
   2113 		}
   2114 	}
   2115 
   2116 	if(scsi_status_is_good(result)) {
   2117 		if (unlikely(buffer[0] == 0x86 && buffer[1] == 0x0b &&
   2118 			     (modepage == 6 || modepage == 8))) {
   2119 			/* Initio breakage? */
   2120 			header_length = 0;
   2121 			data->length = 13;
   2122 			data->medium_type = 0;
   2123 			data->device_specific = 0;
   2124 			data->longlba = 0;
   2125 			data->block_descriptor_length = 0;
   2126 		} else if(use_10_for_ms) {
   2127 			data->length = buffer[0]*256 + buffer[1] + 2;
   2128 			data->medium_type = buffer[2];
   2129 			data->device_specific = buffer[3];
   2130 			data->longlba = buffer[4] & 0x01;
   2131 			data->block_descriptor_length = buffer[6]*256
   2132 				+ buffer[7];
   2133 		} else {
   2134 			data->length = buffer[0] + 1;
   2135 			data->medium_type = buffer[1];
   2136 			data->device_specific = buffer[2];
   2137 			data->block_descriptor_length = buffer[3];
   2138 		}
   2139 		data->header_length = header_length;
   2140 	} else if ((status_byte(result) == CHECK_CONDITION) &&
   2141 		   scsi_sense_valid(sshdr) &&
   2142 		   sshdr->sense_key == UNIT_ATTENTION && retry_count) {
   2143 		retry_count--;
   2144 		goto retry;
   2145 	}
   2146 
   2147 	return result;
   2148 }
   2149 EXPORT_SYMBOL(scsi_mode_sense);
   2150 
   2151 /**
   2152  *	scsi_test_unit_ready - test if unit is ready
   2153  *	@sdev:	scsi device to change the state of.
   2154  *	@timeout: command timeout
   2155  *	@retries: number of retries before failing
   2156  *	@sshdr: outpout pointer for decoded sense information.
   2157  *
   2158  *	Returns zero if unsuccessful or an error if TUR failed.  For
   2159  *	removable media, UNIT_ATTENTION sets ->changed flag.
   2160  **/
   2161 int
   2162 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries,
   2163 		     struct scsi_sense_hdr *sshdr)
   2164 {
   2165 	char cmd[] = {
   2166 		TEST_UNIT_READY, 0, 0, 0, 0, 0,
   2167 	};
   2168 	int result;
   2169 
   2170 	/* try to eat the UNIT_ATTENTION if there are enough retries */
   2171 	do {
   2172 		result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
   2173 					  timeout, 1, NULL);
   2174 		if (sdev->removable && scsi_sense_valid(sshdr) &&
   2175 		    sshdr->sense_key == UNIT_ATTENTION)
   2176 			sdev->changed = 1;
   2177 	} while (scsi_sense_valid(sshdr) &&
   2178 		 sshdr->sense_key == UNIT_ATTENTION && --retries);
   2179 
   2180 	return result;
   2181 }
   2182 EXPORT_SYMBOL(scsi_test_unit_ready);
   2183 
   2184 /**
   2185  *	scsi_device_set_state - Take the given device through the device state model.
   2186  *	@sdev:	scsi device to change the state of.
   2187  *	@state:	state to change to.
   2188  *
   2189  *	Returns zero if successful or an error if the requested
   2190  *	transition is illegal.
   2191  */
   2192 int
   2193 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
   2194 {
   2195 	enum scsi_device_state oldstate = sdev->sdev_state;
   2196 
   2197 	if (state == oldstate)
   2198 		return 0;
   2199 
   2200 	switch (state) {
   2201 	case SDEV_CREATED:
   2202 		switch (oldstate) {
   2203 		case SDEV_CREATED_BLOCK:
   2204 			break;
   2205 		default:
   2206 			goto illegal;
   2207 		}
   2208 		break;
   2209 			
   2210 	case SDEV_RUNNING:
   2211 		switch (oldstate) {
   2212 		case SDEV_CREATED:
   2213 		case SDEV_OFFLINE:
   2214 		case SDEV_TRANSPORT_OFFLINE:
   2215 		case SDEV_QUIESCE:
   2216 		case SDEV_BLOCK:
   2217 			break;
   2218 		default:
   2219 			goto illegal;
   2220 		}
   2221 		break;
   2222 
   2223 	case SDEV_QUIESCE:
   2224 		switch (oldstate) {
   2225 		case SDEV_RUNNING:
   2226 		case SDEV_OFFLINE:
   2227 		case SDEV_TRANSPORT_OFFLINE:
   2228 			break;
   2229 		default:
   2230 			goto illegal;
   2231 		}
   2232 		break;
   2233 
   2234 	case SDEV_OFFLINE:
   2235 	case SDEV_TRANSPORT_OFFLINE:
   2236 		switch (oldstate) {
   2237 		case SDEV_CREATED:
   2238 		case SDEV_RUNNING:
   2239 		case SDEV_QUIESCE:
   2240 		case SDEV_BLOCK:
   2241 			break;
   2242 		default:
   2243 			goto illegal;
   2244 		}
   2245 		break;
   2246 
   2247 	case SDEV_BLOCK:
   2248 		switch (oldstate) {
   2249 		case SDEV_RUNNING:
   2250 		case SDEV_CREATED_BLOCK:
   2251 		case SDEV_OFFLINE:
   2252 			break;
   2253 		default:
   2254 			goto illegal;
   2255 		}
   2256 		break;
   2257 
   2258 	case SDEV_CREATED_BLOCK:
   2259 		switch (oldstate) {
   2260 		case SDEV_CREATED:
   2261 			break;
   2262 		default:
   2263 			goto illegal;
   2264 		}
   2265 		break;
   2266 
   2267 	case SDEV_CANCEL:
   2268 		switch (oldstate) {
   2269 		case SDEV_CREATED:
   2270 		case SDEV_RUNNING:
   2271 		case SDEV_QUIESCE:
   2272 		case SDEV_OFFLINE:
   2273 		case SDEV_TRANSPORT_OFFLINE:
   2274 			break;
   2275 		default:
   2276 			goto illegal;
   2277 		}
   2278 		break;
   2279 
   2280 	case SDEV_DEL:
   2281 		switch (oldstate) {
   2282 		case SDEV_CREATED:
   2283 		case SDEV_RUNNING:
   2284 		case SDEV_OFFLINE:
   2285 		case SDEV_TRANSPORT_OFFLINE:
   2286 		case SDEV_CANCEL:
   2287 		case SDEV_BLOCK:
   2288 		case SDEV_CREATED_BLOCK:
   2289 			break;
   2290 		default:
   2291 			goto illegal;
   2292 		}
   2293 		break;
   2294 
   2295 	}
   2296 	sdev->sdev_state = state;
   2297 	return 0;
   2298 
   2299  illegal:
   2300 	SCSI_LOG_ERROR_RECOVERY(1,
   2301 				sdev_printk(KERN_ERR, sdev,
   2302 					    "Illegal state transition %s->%s",
   2303 					    scsi_device_state_name(oldstate),
   2304 					    scsi_device_state_name(state))
   2305 				);
   2306 	return -EINVAL;
   2307 }
   2308 EXPORT_SYMBOL(scsi_device_set_state);
   2309 
   2310 /**
   2311  * 	sdev_evt_emit - emit a single SCSI device uevent
   2312  *	@sdev: associated SCSI device
   2313  *	@evt: event to emit
   2314  *
   2315  *	Send a single uevent (scsi_event) to the associated scsi_device.
   2316  */
   2317 static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
   2318 {
   2319 	int idx = 0;
   2320 	char *envp[3];
   2321 
   2322 	switch (evt->evt_type) {
   2323 	case SDEV_EVT_MEDIA_CHANGE:
   2324 		envp[idx++] = "SDEV_MEDIA_CHANGE=1";
   2325 		break;
   2326 	case SDEV_EVT_INQUIRY_CHANGE_REPORTED:
   2327 		scsi_rescan_device(&sdev->sdev_gendev);
   2328 		envp[idx++] = "SDEV_UA=INQUIRY_DATA_HAS_CHANGED";
   2329 		break;
   2330 	case SDEV_EVT_CAPACITY_CHANGE_REPORTED:
   2331 		envp[idx++] = "SDEV_UA=CAPACITY_DATA_HAS_CHANGED";
   2332 		break;
   2333 	case SDEV_EVT_SOFT_THRESHOLD_REACHED_REPORTED:
   2334 	       envp[idx++] = "SDEV_UA=THIN_PROVISIONING_SOFT_THRESHOLD_REACHED";
   2335 		break;
   2336 	case SDEV_EVT_MODE_PARAMETER_CHANGE_REPORTED:
   2337 		envp[idx++] = "SDEV_UA=MODE_PARAMETERS_CHANGED";
   2338 		break;
   2339 	case SDEV_EVT_LUN_CHANGE_REPORTED:
   2340 		envp[idx++] = "SDEV_UA=REPORTED_LUNS_DATA_HAS_CHANGED";
   2341 		break;
   2342 	case SDEV_EVT_ALUA_STATE_CHANGE_REPORTED:
   2343 		envp[idx++] = "SDEV_UA=ASYMMETRIC_ACCESS_STATE_CHANGED";
   2344 		break;
   2345 	case SDEV_EVT_POWER_ON_RESET_OCCURRED:
   2346 		envp[idx++] = "SDEV_UA=POWER_ON_RESET_OCCURRED";
   2347 		break;
   2348 	default:
   2349 		/* do nothing */
   2350 		break;
   2351 	}
   2352 
   2353 	envp[idx++] = NULL;
   2354 
   2355 	kobject_uevent_env(&sdev->sdev_gendev.kobj, KOBJ_CHANGE, envp);
   2356 }
   2357 
   2358 /**
   2359  * 	sdev_evt_thread - send a uevent for each scsi event
   2360  *	@work: work struct for scsi_device
   2361  *
   2362  *	Dispatch queued events to their associated scsi_device kobjects
   2363  *	as uevents.
   2364  */
   2365 void scsi_evt_thread(struct work_struct *work)
   2366 {
   2367 	struct scsi_device *sdev;
   2368 	enum scsi_device_event evt_type;
   2369 	LIST_HEAD(event_list);
   2370 
   2371 	sdev = container_of(work, struct scsi_device, event_work);
   2372 
   2373 	for (evt_type = SDEV_EVT_FIRST; evt_type <= SDEV_EVT_LAST; evt_type++)
   2374 		if (test_and_clear_bit(evt_type, sdev->pending_events))
   2375 			sdev_evt_send_simple(sdev, evt_type, GFP_KERNEL);
   2376 
   2377 	while (1) {
   2378 		struct scsi_event *evt;
   2379 		struct list_head *this, *tmp;
   2380 		unsigned long flags;
   2381 
   2382 		spin_lock_irqsave(&sdev->list_lock, flags);
   2383 		list_splice_init(&sdev->event_list, &event_list);
   2384 		spin_unlock_irqrestore(&sdev->list_lock, flags);
   2385 
   2386 		if (list_empty(&event_list))
   2387 			break;
   2388 
   2389 		list_for_each_safe(this, tmp, &event_list) {
   2390 			evt = list_entry(this, struct scsi_event, node);
   2391 			list_del(&evt->node);
   2392 			scsi_evt_emit(sdev, evt);
   2393 			kfree(evt);
   2394 		}
   2395 	}
   2396 }
   2397 
   2398 /**
   2399  * 	sdev_evt_send - send asserted event to uevent thread
   2400  *	@sdev: scsi_device event occurred on
   2401  *	@evt: event to send
   2402  *
   2403  *	Assert scsi device event asynchronously.
   2404  */
   2405 void sdev_evt_send(struct scsi_device *sdev, struct scsi_event *evt)
   2406 {
   2407 	unsigned long flags;
   2408 
   2409 #if 0
   2410 	/* FIXME: currently this check eliminates all media change events
   2411 	 * for polled devices.  Need to update to discriminate between AN
   2412 	 * and polled events */
   2413 	if (!test_bit(evt->evt_type, sdev->supported_events)) {
   2414 		kfree(evt);
   2415 		return;
   2416 	}
   2417 #endif
   2418 
   2419 	spin_lock_irqsave(&sdev->list_lock, flags);
   2420 	list_add_tail(&evt->node, &sdev->event_list);
   2421 	schedule_work(&sdev->event_work);
   2422 	spin_unlock_irqrestore(&sdev->list_lock, flags);
   2423 }
   2424 EXPORT_SYMBOL_GPL(sdev_evt_send);
   2425 
   2426 /**
   2427  * 	sdev_evt_alloc - allocate a new scsi event
   2428  *	@evt_type: type of event to allocate
   2429  *	@gfpflags: GFP flags for allocation
   2430  *
   2431  *	Allocates and returns a new scsi_event.
   2432  */
   2433 struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
   2434 				  gfp_t gfpflags)
   2435 {
   2436 	struct scsi_event *evt = kzalloc(sizeof(struct scsi_event), gfpflags);
   2437 	if (!evt)
   2438 		return NULL;
   2439 
   2440 	evt->evt_type = evt_type;
   2441 	INIT_LIST_HEAD(&evt->node);
   2442 
   2443 	/* evt_type-specific initialization, if any */
   2444 	switch (evt_type) {
   2445 	case SDEV_EVT_MEDIA_CHANGE:
   2446 	case SDEV_EVT_INQUIRY_CHANGE_REPORTED:
   2447 	case SDEV_EVT_CAPACITY_CHANGE_REPORTED:
   2448 	case SDEV_EVT_SOFT_THRESHOLD_REACHED_REPORTED:
   2449 	case SDEV_EVT_MODE_PARAMETER_CHANGE_REPORTED:
   2450 	case SDEV_EVT_LUN_CHANGE_REPORTED:
   2451 	case SDEV_EVT_ALUA_STATE_CHANGE_REPORTED:
   2452 	case SDEV_EVT_POWER_ON_RESET_OCCURRED:
   2453 	default:
   2454 		/* do nothing */
   2455 		break;
   2456 	}
   2457 
   2458 	return evt;
   2459 }
   2460 EXPORT_SYMBOL_GPL(sdev_evt_alloc);
   2461 
   2462 /**
   2463  * 	sdev_evt_send_simple - send asserted event to uevent thread
   2464  *	@sdev: scsi_device event occurred on
   2465  *	@evt_type: type of event to send
   2466  *	@gfpflags: GFP flags for allocation
   2467  *
   2468  *	Assert scsi device event asynchronously, given an event type.
   2469  */
   2470 void sdev_evt_send_simple(struct scsi_device *sdev,
   2471 			  enum scsi_device_event evt_type, gfp_t gfpflags)
   2472 {
   2473 	struct scsi_event *evt = sdev_evt_alloc(evt_type, gfpflags);
   2474 	if (!evt) {
   2475 		sdev_printk(KERN_ERR, sdev, "event %d eaten due to OOM\n",
   2476 			    evt_type);
   2477 		return;
   2478 	}
   2479 
   2480 	sdev_evt_send(sdev, evt);
   2481 }
   2482 EXPORT_SYMBOL_GPL(sdev_evt_send_simple);
   2483 
   2484 /**
   2485  *	scsi_device_quiesce - Block user issued commands.
   2486  *	@sdev:	scsi device to quiesce.
   2487  *
   2488  *	This works by trying to transition to the SDEV_QUIESCE state
   2489  *	(which must be a legal transition).  When the device is in this
   2490  *	state, only special requests will be accepted, all others will
   2491  *	be deferred.  Since special requests may also be requeued requests,
   2492  *	a successful return doesn't guarantee the device will be 
   2493  *	totally quiescent.
   2494  *
   2495  *	Must be called with user context, may sleep.
   2496  *
   2497  *	Returns zero if unsuccessful or an error if not.
   2498  */
   2499 int
   2500 scsi_device_quiesce(struct scsi_device *sdev)
   2501 {
   2502 	struct request_queue *q = sdev->request_queue;
   2503 	int err;
   2504 
   2505 	/*
   2506 	 * It is allowed to call scsi_device_quiesce() multiple times from
   2507 	 * the same context but concurrent scsi_device_quiesce() calls are
   2508 	 * not allowed.
   2509 	 */
   2510 	WARN_ON_ONCE(sdev->quiesced_by && sdev->quiesced_by != current);
   2511 
   2512 	if (sdev->quiesced_by == current)
   2513 		return 0;
   2514 
   2515 	blk_set_pm_only(q);
   2516 
   2517 	blk_mq_freeze_queue(q);
   2518 	/*
   2519 	 * Ensure that the effect of blk_set_pm_only() will be visible
   2520 	 * for percpu_ref_tryget() callers that occur after the queue
   2521 	 * unfreeze even if the queue was already frozen before this function
   2522 	 * was called. See also https://lwn.net/Articles/573497/.
   2523 	 */
   2524 	synchronize_rcu();
   2525 	blk_mq_unfreeze_queue(q);
   2526 
   2527 	mutex_lock(&sdev->state_mutex);
   2528 	err = scsi_device_set_state(sdev, SDEV_QUIESCE);
   2529 	if (err == 0)
   2530 		sdev->quiesced_by = current;
   2531 	else
   2532 		blk_clear_pm_only(q);
   2533 	mutex_unlock(&sdev->state_mutex);
   2534 
   2535 	return err;
   2536 }
   2537 EXPORT_SYMBOL(scsi_device_quiesce);
   2538 
   2539 /**
   2540  *	scsi_device_resume - Restart user issued commands to a quiesced device.
   2541  *	@sdev:	scsi device to resume.
   2542  *
   2543  *	Moves the device from quiesced back to running and restarts the
   2544  *	queues.
   2545  *
   2546  *	Must be called with user context, may sleep.
   2547  */
   2548 void scsi_device_resume(struct scsi_device *sdev)
   2549 {
   2550 	/* check if the device state was mutated prior to resume, and if
   2551 	 * so assume the state is being managed elsewhere (for example
   2552 	 * device deleted during suspend)
   2553 	 */
   2554 	mutex_lock(&sdev->state_mutex);
   2555 	if (sdev->quiesced_by) {
   2556 		sdev->quiesced_by = NULL;
   2557 		blk_clear_pm_only(sdev->request_queue);
   2558 	}
   2559 	if (sdev->sdev_state == SDEV_QUIESCE)
   2560 		scsi_device_set_state(sdev, SDEV_RUNNING);
   2561 	mutex_unlock(&sdev->state_mutex);
   2562 }
   2563 EXPORT_SYMBOL(scsi_device_resume);
   2564 
   2565 static void
   2566 device_quiesce_fn(struct scsi_device *sdev, void *data)
   2567 {
   2568 	scsi_device_quiesce(sdev);
   2569 }
   2570 
   2571 void
   2572 scsi_target_quiesce(struct scsi_target *starget)
   2573 {
   2574 	starget_for_each_device(starget, NULL, device_quiesce_fn);
   2575 }
   2576 EXPORT_SYMBOL(scsi_target_quiesce);
   2577 
   2578 static void
   2579 device_resume_fn(struct scsi_device *sdev, void *data)
   2580 {
   2581 	scsi_device_resume(sdev);
   2582 }
   2583 
   2584 void
   2585 scsi_target_resume(struct scsi_target *starget)
   2586 {
   2587 	starget_for_each_device(starget, NULL, device_resume_fn);
   2588 }
   2589 EXPORT_SYMBOL(scsi_target_resume);
   2590 
   2591 /**
   2592  * scsi_internal_device_block_nowait - try to transition to the SDEV_BLOCK state
   2593  * @sdev: device to block
   2594  *
   2595  * Pause SCSI command processing on the specified device. Does not sleep.
   2596  *
   2597  * Returns zero if successful or a negative error code upon failure.
   2598  *
   2599  * Notes:
   2600  * This routine transitions the device to the SDEV_BLOCK state (which must be
   2601  * a legal transition). When the device is in this state, command processing
   2602  * is paused until the device leaves the SDEV_BLOCK state. See also
   2603  * scsi_internal_device_unblock_nowait().
   2604  */
   2605 int scsi_internal_device_block_nowait(struct scsi_device *sdev)
   2606 {
   2607 	struct request_queue *q = sdev->request_queue;
   2608 	int err = 0;
   2609 
   2610 	err = scsi_device_set_state(sdev, SDEV_BLOCK);
   2611 	if (err) {
   2612 		err = scsi_device_set_state(sdev, SDEV_CREATED_BLOCK);
   2613 
   2614 		if (err)
   2615 			return err;
   2616 	}
   2617 
   2618 	/* 
   2619 	 * The device has transitioned to SDEV_BLOCK.  Stop the
   2620 	 * block layer from calling the midlayer with this device's
   2621 	 * request queue. 
   2622 	 */
   2623 	blk_mq_quiesce_queue_nowait(q);
   2624 	return 0;
   2625 }
   2626 EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
   2627 
   2628 /**
   2629  * scsi_internal_device_block - try to transition to the SDEV_BLOCK state
   2630  * @sdev: device to block
   2631  *
   2632  * Pause SCSI command processing on the specified device and wait until all
   2633  * ongoing scsi_request_fn() / scsi_queue_rq() calls have finished. May sleep.
   2634  *
   2635  * Returns zero if successful or a negative error code upon failure.
   2636  *
   2637  * Note:
   2638  * This routine transitions the device to the SDEV_BLOCK state (which must be
   2639  * a legal transition). When the device is in this state, command processing
   2640  * is paused until the device leaves the SDEV_BLOCK state. See also
   2641  * scsi_internal_device_unblock().
   2642  *
   2643  * To do: avoid that scsi_send_eh_cmnd() calls queuecommand() after
   2644  * scsi_internal_device_block() has blocked a SCSI device and also
   2645  * remove the rport mutex lock and unlock calls from srp_queuecommand().
   2646  */
   2647 static int scsi_internal_device_block(struct scsi_device *sdev)
   2648 {
   2649 	struct request_queue *q = sdev->request_queue;
   2650 	int err;
   2651 
   2652 	mutex_lock(&sdev->state_mutex);
   2653 	err = scsi_internal_device_block_nowait(sdev);
   2654 	if (err == 0)
   2655 		blk_mq_quiesce_queue(q);
   2656 	mutex_unlock(&sdev->state_mutex);
   2657 
   2658 	return err;
   2659 }
   2660  
   2661 void scsi_start_queue(struct scsi_device *sdev)
   2662 {
   2663 	struct request_queue *q = sdev->request_queue;
   2664 
   2665 	blk_mq_unquiesce_queue(q);
   2666 }
   2667 
   2668 /**
   2669  * scsi_internal_device_unblock_nowait - resume a device after a block request
   2670  * @sdev:	device to resume
   2671  * @new_state:	state to set the device to after unblocking
   2672  *
   2673  * Restart the device queue for a previously suspended SCSI device. Does not
   2674  * sleep.
   2675  *
   2676  * Returns zero if successful or a negative error code upon failure.
   2677  *
   2678  * Notes:
   2679  * This routine transitions the device to the SDEV_RUNNING state or to one of
   2680  * the offline states (which must be a legal transition) allowing the midlayer
   2681  * to goose the queue for this device.
   2682  */
   2683 int scsi_internal_device_unblock_nowait(struct scsi_device *sdev,
   2684 					enum scsi_device_state new_state)
   2685 {
   2686 	/*
   2687 	 * Try to transition the scsi device to SDEV_RUNNING or one of the
   2688 	 * offlined states and goose the device queue if successful.
   2689 	 */
   2690 	switch (sdev->sdev_state) {
   2691 	case SDEV_BLOCK:
   2692 	case SDEV_TRANSPORT_OFFLINE:
   2693 		sdev->sdev_state = new_state;
   2694 		break;
   2695 	case SDEV_CREATED_BLOCK:
   2696 		if (new_state == SDEV_TRANSPORT_OFFLINE ||
   2697 		    new_state == SDEV_OFFLINE)
   2698 			sdev->sdev_state = new_state;
   2699 		else
   2700 			sdev->sdev_state = SDEV_CREATED;
   2701 		break;
   2702 	case SDEV_CANCEL:
   2703 	case SDEV_OFFLINE:
   2704 		break;
   2705 	default:
   2706 		return -EINVAL;
   2707 	}
   2708 	scsi_start_queue(sdev);
   2709 
   2710 	return 0;
   2711 }
   2712 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock_nowait);
   2713 
   2714 /**
   2715  * scsi_internal_device_unblock - resume a device after a block request
   2716  * @sdev:	device to resume
   2717  * @new_state:	state to set the device to after unblocking
   2718  *
   2719  * Restart the device queue for a previously suspended SCSI device. May sleep.
   2720  *
   2721  * Returns zero if successful or a negative error code upon failure.
   2722  *
   2723  * Notes:
   2724  * This routine transitions the device to the SDEV_RUNNING state or to one of
   2725  * the offline states (which must be a legal transition) allowing the midlayer
   2726  * to goose the queue for this device.
   2727  */
   2728 static int scsi_internal_device_unblock(struct scsi_device *sdev,
   2729 					enum scsi_device_state new_state)
   2730 {
   2731 	int ret;
   2732 
   2733 	mutex_lock(&sdev->state_mutex);
   2734 	ret = scsi_internal_device_unblock_nowait(sdev, new_state);
   2735 	mutex_unlock(&sdev->state_mutex);
   2736 
   2737 	return ret;
   2738 }
   2739 
   2740 static void
   2741 device_block(struct scsi_device *sdev, void *data)
   2742 {
   2743 	scsi_internal_device_block(sdev);
   2744 }
   2745 
   2746 static int
   2747 target_block(struct device *dev, void *data)
   2748 {
   2749 	if (scsi_is_target_device(dev))
   2750 		starget_for_each_device(to_scsi_target(dev), NULL,
   2751 					device_block);
   2752 	return 0;
   2753 }
   2754 
   2755 void
   2756 scsi_target_block(struct device *dev)
   2757 {
   2758 	if (scsi_is_target_device(dev))
   2759 		starget_for_each_device(to_scsi_target(dev), NULL,
   2760 					device_block);
   2761 	else
   2762 		device_for_each_child(dev, NULL, target_block);
   2763 }
   2764 EXPORT_SYMBOL_GPL(scsi_target_block);
   2765 
   2766 static void
   2767 device_unblock(struct scsi_device *sdev, void *data)
   2768 {
   2769 	scsi_internal_device_unblock(sdev, *(enum scsi_device_state *)data);
   2770 }
   2771 
   2772 static int
   2773 target_unblock(struct device *dev, void *data)
   2774 {
   2775 	if (scsi_is_target_device(dev))
   2776 		starget_for_each_device(to_scsi_target(dev), data,
   2777 					device_unblock);
   2778 	return 0;
   2779 }
   2780 
   2781 void
   2782 scsi_target_unblock(struct device *dev, enum scsi_device_state new_state)
   2783 {
   2784 	if (scsi_is_target_device(dev))
   2785 		starget_for_each_device(to_scsi_target(dev), &new_state,
   2786 					device_unblock);
   2787 	else
   2788 		device_for_each_child(dev, &new_state, target_unblock);
   2789 }
   2790 EXPORT_SYMBOL_GPL(scsi_target_unblock);
   2791 
   2792 /**
   2793  * scsi_kmap_atomic_sg - find and atomically map an sg-elemnt
   2794  * @sgl:	scatter-gather list
   2795  * @sg_count:	number of segments in sg
   2796  * @offset:	offset in bytes into sg, on return offset into the mapped area
   2797  * @len:	bytes to map, on return number of bytes mapped
   2798  *
   2799  * Returns virtual address of the start of the mapped page
   2800  */
   2801 void *scsi_kmap_atomic_sg(struct scatterlist *sgl, int sg_count,
   2802 			  size_t *offset, size_t *len)
   2803 {
   2804 	int i;
   2805 	size_t sg_len = 0, len_complete = 0;
   2806 	struct scatterlist *sg;
   2807 	struct page *page;
   2808 
   2809 	WARN_ON(!irqs_disabled());
   2810 
   2811 	for_each_sg(sgl, sg, sg_count, i) {
   2812 		len_complete = sg_len; /* Complete sg-entries */
   2813 		sg_len += sg->length;
   2814 		if (sg_len > *offset)
   2815 			break;
   2816 	}
   2817 
   2818 	if (unlikely(i == sg_count)) {
   2819 		printk(KERN_ERR "%s: Bytes in sg: %zu, requested offset %zu, "
   2820 			"elements %d\n",
   2821 		       __func__, sg_len, *offset, sg_count);
   2822 		WARN_ON(1);
   2823 		return NULL;
   2824 	}
   2825 
   2826 	/* Offset starting from the beginning of first page in this sg-entry */
   2827 	*offset = *offset - len_complete + sg->offset;
   2828 
   2829 	/* Assumption: contiguous pages can be accessed as "page + i" */
   2830 	page = nth_page(sg_page(sg), (*offset >> PAGE_SHIFT));
   2831 	*offset &= ~PAGE_MASK;
   2832 
   2833 	/* Bytes in this sg-entry from *offset to the end of the page */
   2834 	sg_len = PAGE_SIZE - *offset;
   2835 	if (*len > sg_len)
   2836 		*len = sg_len;
   2837 
   2838 	return kmap_atomic(page);
   2839 }
   2840 EXPORT_SYMBOL(scsi_kmap_atomic_sg);
   2841 
   2842 /**
   2843  * scsi_kunmap_atomic_sg - atomically unmap a virtual address, previously mapped with scsi_kmap_atomic_sg
   2844  * @virt:	virtual address to be unmapped
   2845  */
   2846 void scsi_kunmap_atomic_sg(void *virt)
   2847 {
   2848 	kunmap_atomic(virt);
   2849 }
   2850 EXPORT_SYMBOL(scsi_kunmap_atomic_sg);
   2851 
   2852 void sdev_disable_disk_events(struct scsi_device *sdev)
   2853 {
   2854 	atomic_inc(&sdev->disk_events_disable_depth);
   2855 }
   2856 EXPORT_SYMBOL(sdev_disable_disk_events);
   2857 
   2858 void sdev_enable_disk_events(struct scsi_device *sdev)
   2859 {
   2860 	if (WARN_ON_ONCE(atomic_read(&sdev->disk_events_disable_depth) <= 0))
   2861 		return;
   2862 	atomic_dec(&sdev->disk_events_disable_depth);
   2863 }
   2864 EXPORT_SYMBOL(sdev_enable_disk_events);
   2865 
   2866 /**
   2867  * scsi_vpd_lun_id - return a unique device identification
   2868  * @sdev: SCSI device
   2869  * @id:   buffer for the identification
   2870  * @id_len:  length of the buffer
   2871  *
   2872  * Copies a unique device identification into @id based
   2873  * on the information in the VPD page 0x83 of the device.
   2874  * The string will be formatted as a SCSI name string.
   2875  *
   2876  * Returns the length of the identification or error on failure.
   2877  * If the identifier is longer than the supplied buffer the actual
   2878  * identifier length is returned and the buffer is not zero-padded.
   2879  */
   2880 int scsi_vpd_lun_id(struct scsi_device *sdev, char *id, size_t id_len)
   2881 {
   2882 	u8 cur_id_type = 0xff;
   2883 	u8 cur_id_size = 0;
   2884 	const unsigned char *d, *cur_id_str;
   2885 	const struct scsi_vpd *vpd_pg83;
   2886 	int id_size = -EINVAL;
   2887 
   2888 	rcu_read_lock();
   2889 	vpd_pg83 = rcu_dereference(sdev->vpd_pg83);
   2890 	if (!vpd_pg83) {
   2891 		rcu_read_unlock();
   2892 		return -ENXIO;
   2893 	}
   2894 
   2895 	/*
   2896 	 * Look for the correct descriptor.
   2897 	 * Order of preference for lun descriptor:
   2898 	 * - SCSI name string
   2899 	 * - NAA IEEE Registered Extended
   2900 	 * - EUI-64 based 16-byte
   2901 	 * - EUI-64 based 12-byte
   2902 	 * - NAA IEEE Registered
   2903 	 * - NAA IEEE Extended
   2904 	 * - T10 Vendor ID
   2905 	 * as longer descriptors reduce the likelyhood
   2906 	 * of identification clashes.
   2907 	 */
   2908 
   2909 	/* The id string must be at least 20 bytes + terminating NULL byte */
   2910 	if (id_len < 21) {
   2911 		rcu_read_unlock();
   2912 		return -EINVAL;
   2913 	}
   2914 
   2915 	memset(id, 0, id_len);
   2916 	d = vpd_pg83->data + 4;
   2917 	while (d < vpd_pg83->data + vpd_pg83->len) {
   2918 		/* Skip designators not referring to the LUN */
   2919 		if ((d[1] & 0x30) != 0x00)
   2920 			goto next_desig;
   2921 
   2922 		switch (d[1] & 0xf) {
   2923 		case 0x1:
   2924 			/* T10 Vendor ID */
   2925 			if (cur_id_size > d[3])
   2926 				break;
   2927 			/* Prefer anything */
   2928 			if (cur_id_type > 0x01 && cur_id_type != 0xff)
   2929 				break;
   2930 			cur_id_size = d[3];
   2931 			if (cur_id_size + 4 > id_len)
   2932 				cur_id_size = id_len - 4;
   2933 			cur_id_str = d + 4;
   2934 			cur_id_type = d[1] & 0xf;
   2935 			id_size = snprintf(id, id_len, "t10.%*pE",
   2936 					   cur_id_size, cur_id_str);
   2937 			break;
   2938 		case 0x2:
   2939 			/* EUI-64 */
   2940 			if (cur_id_size > d[3])
   2941 				break;
   2942 			/* Prefer NAA IEEE Registered Extended */
   2943 			if (cur_id_type == 0x3 &&
   2944 			    cur_id_size == d[3])
   2945 				break;
   2946 			cur_id_size = d[3];
   2947 			cur_id_str = d + 4;
   2948 			cur_id_type = d[1] & 0xf;
   2949 			switch (cur_id_size) {
   2950 			case 8:
   2951 				id_size = snprintf(id, id_len,
   2952 						   "eui.%8phN",
   2953 						   cur_id_str);
   2954 				break;
   2955 			case 12:
   2956 				id_size = snprintf(id, id_len,
   2957 						   "eui.%12phN",
   2958 						   cur_id_str);
   2959 				break;
   2960 			case 16:
   2961 				id_size = snprintf(id, id_len,
   2962 						   "eui.%16phN",
   2963 						   cur_id_str);
   2964 				break;
   2965 			default:
   2966 				cur_id_size = 0;
   2967 				break;
   2968 			}
   2969 			break;
   2970 		case 0x3:
   2971 			/* NAA */
   2972 			if (cur_id_size > d[3])
   2973 				break;
   2974 			cur_id_size = d[3];
   2975 			cur_id_str = d + 4;
   2976 			cur_id_type = d[1] & 0xf;
   2977 			switch (cur_id_size) {
   2978 			case 8:
   2979 				id_size = snprintf(id, id_len,
   2980 						   "naa.%8phN",
   2981 						   cur_id_str);
   2982 				break;
   2983 			case 16:
   2984 				id_size = snprintf(id, id_len,
   2985 						   "naa.%16phN",
   2986 						   cur_id_str);
   2987 				break;
   2988 			default:
   2989 				cur_id_size = 0;
   2990 				break;
   2991 			}
   2992 			break;
   2993 		case 0x8:
   2994 			/* SCSI name string */
   2995 			if (cur_id_size + 4 > d[3])
   2996 				break;
   2997 			/* Prefer others for truncated descriptor */
   2998 			if (cur_id_size && d[3] > id_len)
   2999 				break;
   3000 			cur_id_size = id_size = d[3];
   3001 			cur_id_str = d + 4;
   3002 			cur_id_type = d[1] & 0xf;
   3003 			if (cur_id_size >= id_len)
   3004 				cur_id_size = id_len - 1;
   3005 			memcpy(id, cur_id_str, cur_id_size);
   3006 			/* Decrease priority for truncated descriptor */
   3007 			if (cur_id_size != id_size)
   3008 				cur_id_size = 6;
   3009 			break;
   3010 		default:
   3011 			break;
   3012 		}
   3013 next_desig:
   3014 		d += d[3] + 4;
   3015 	}
   3016 	rcu_read_unlock();
   3017 
   3018 	return id_size;
   3019 }
   3020 EXPORT_SYMBOL(scsi_vpd_lun_id);
   3021 
   3022 /*
   3023  * scsi_vpd_tpg_id - return a target port group identifier
   3024  * @sdev: SCSI device
   3025  *
   3026  * Returns the Target Port Group identifier from the information
   3027  * froom VPD page 0x83 of the device.
   3028  *
   3029  * Returns the identifier or error on failure.
   3030  */
   3031 int scsi_vpd_tpg_id(struct scsi_device *sdev, int *rel_id)
   3032 {
   3033 	const unsigned char *d;
   3034 	const struct scsi_vpd *vpd_pg83;
   3035 	int group_id = -EAGAIN, rel_port = -1;
   3036 
   3037 	rcu_read_lock();
   3038 	vpd_pg83 = rcu_dereference(sdev->vpd_pg83);
   3039 	if (!vpd_pg83) {
   3040 		rcu_read_unlock();
   3041 		return -ENXIO;
   3042 	}
   3043 
   3044 	d = vpd_pg83->data + 4;
   3045 	while (d < vpd_pg83->data + vpd_pg83->len) {
   3046 		switch (d[1] & 0xf) {
   3047 		case 0x4:
   3048 			/* Relative target port */
   3049 			rel_port = get_unaligned_be16(&d[6]);
   3050 			break;
   3051 		case 0x5:
   3052 			/* Target port group */
   3053 			group_id = get_unaligned_be16(&d[6]);
   3054 			break;
   3055 		default:
   3056 			break;
   3057 		}
   3058 		d += d[3] + 4;
   3059 	}
   3060 	rcu_read_unlock();
   3061 
   3062 	if (group_id >= 0 && rel_id && rel_port != -1)
   3063 		*rel_id = rel_port;
   3064 
   3065 	return group_id;
   3066 }
   3067 EXPORT_SYMBOL(scsi_vpd_tpg_id);