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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 1999 Eric Youngdale
  * Copyright (C) 2014 Christoph Hellwig
  *
  *  SCSI queueing library.
  *      Initial versions: Eric Youngdale (eric@andante.org).
  *                        Based upon conversations with large numbers
  *                        of people at Linux Expo.
  */
 
 #include <linux/bio.h>
 #include <linux/bitops.h>
 #include <linux/blkdev.h>
 #include <linux/completion.h>
 #include <linux/kernel.h>
 #include <linux/export.h>
 #include <linux/init.h>
 #include <linux/pci.h>
 #include <linux/delay.h>
 #include <linux/hardirq.h>
 #include <linux/scatterlist.h>
 #include <linux/blk-mq.h>
 #include <linux/blk-integrity.h>
 #include <linux/ratelimit.h>
 #include <asm/unaligned.h>
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
 #include <scsi/scsi_dbg.h>
 #include <scsi/scsi_device.h>
 #include <scsi/scsi_driver.h>
 #include <scsi/scsi_eh.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_transport.h> /* __scsi_init_queue() */
 #include <scsi/scsi_dh.h>
 
 #include <trace/events/scsi.h>
 
 #include "scsi_debugfs.h"
 #include "scsi_priv.h"
 #include "scsi_logging.h"
 
 /*
  * Size of integrity metadata is usually small, 1 inline sg should
  * cover normal cases.
  */
 #ifdef CONFIG_ARCH_NO_SG_CHAIN
 #define  SCSI_INLINE_PROT_SG_CNT  0
 #define  SCSI_INLINE_SG_CNT  0
 #else
 #define  SCSI_INLINE_PROT_SG_CNT  1
 #define  SCSI_INLINE_SG_CNT  2
 #endif
 
 static struct kmem_cache *scsi_sense_cache;
 static DEFINE_MUTEX(scsi_sense_cache_mutex);
 
 static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd);
 
 int scsi_init_sense_cache(struct Scsi_Host *shost)
 {
     int ret = 0;
 
     mutex_lock(&scsi_sense_cache_mutex);
     if (!scsi_sense_cache) {
         scsi_sense_cache =
             kmem_cache_create_usercopy("scsi_sense_cache",
                 SCSI_SENSE_BUFFERSIZE, 0, SLAB_HWCACHE_ALIGN,
                 0, SCSI_SENSE_BUFFERSIZE, NULL);
         if (!scsi_sense_cache)
             ret = -ENOMEM;
     }
     mutex_unlock(&scsi_sense_cache_mutex);
     return ret;
 }
 
 static void
 scsi_set_blocked(struct scsi_cmnd *cmd, int reason)
 {
     struct Scsi_Host *host = cmd->device->host;
     struct scsi_device *device = cmd->device;
     struct scsi_target *starget = scsi_target(device);
 
     /*
      * Set the appropriate busy bit for the device/host.
      *
      * If the host/device isn't busy, assume that something actually
      * completed, and that we should be able to queue a command now.
      *
      * Note that the prior mid-layer assumption that any host could
      * always queue at least one command is now broken.  The mid-layer
      * will implement a user specifiable stall (see
      * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
      * if a command is requeued with no other commands outstanding
      * either for the device or for the host.
      */
     switch (reason) {
     case SCSI_MLQUEUE_HOST_BUSY:
         atomic_set(&host->host_blocked, host->max_host_blocked);
         break;
     case SCSI_MLQUEUE_DEVICE_BUSY:
     case SCSI_MLQUEUE_EH_RETRY:
         atomic_set(&device->device_blocked,
                device->max_device_blocked);
         break;
     case SCSI_MLQUEUE_TARGET_BUSY:
         atomic_set(&starget->target_blocked,
                starget->max_target_blocked);
         break;
     }
 }
 
 static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd, unsigned long msecs)
 {
     struct request *rq = scsi_cmd_to_rq(cmd);
 
     if (rq->rq_flags & RQF_DONTPREP) {
         rq->rq_flags &= ~RQF_DONTPREP;
         scsi_mq_uninit_cmd(cmd);
     } else {
         WARN_ON_ONCE(true);
     }
 
     if (msecs) {
         blk_mq_requeue_request(rq, false);
         blk_mq_delay_kick_requeue_list(rq->q, msecs);
     } else
         blk_mq_requeue_request(rq, true);
 }
 
 /**
  * __scsi_queue_insert - private queue insertion
  * @cmd: The SCSI command being requeued
  * @reason:  The reason for the requeue
  * @unbusy: Whether the queue should be unbusied
  *
  * This is a private queue insertion.  The public interface
  * scsi_queue_insert() always assumes the queue should be unbusied
  * because it's always called before the completion.  This function is
  * for a requeue after completion, which should only occur in this
  * file.
  */
 static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
 {
     struct scsi_device *device = cmd->device;
 
     SCSI_LOG_MLQUEUE(1, scmd_printk(KERN_INFO, cmd,
         "Inserting command %p into mlqueue\n", cmd));
 
     scsi_set_blocked(cmd, reason);
 
     /*
      * Decrement the counters, since these commands are no longer
      * active on the host/device.
      */
     if (unbusy)
         scsi_device_unbusy(device, cmd);
 
     /*
      * Requeue this command.  It will go before all other commands
      * that are already in the queue. Schedule requeue work under
      * lock such that the kblockd_schedule_work() call happens
      * before blk_mq_destroy_queue() finishes.
      */
     cmd->result = 0;
 
     blk_mq_requeue_request(scsi_cmd_to_rq(cmd), true);
 }
 
 /**
  * scsi_queue_insert - Reinsert a command in the queue.
  * @cmd:    command that we are adding to queue.
  * @reason: why we are inserting command to queue.
  *
  * We do this for one of two cases. Either the host is busy and it cannot accept
  * any more commands for the time being, or the device returned QUEUE_FULL and
  * can accept no more commands.
  *
  * Context: This could be called either from an interrupt context or a normal
  * process context.
  */
 void scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
 {
     __scsi_queue_insert(cmd, reason, true);
 }
 
 
 /**
  * __scsi_execute - insert request and wait for the result
  * @sdev:   scsi device
  * @cmd:    scsi command
  * @data_direction: data direction
  * @buffer: data buffer
  * @bufflen:    len of buffer
  * @sense:  optional sense buffer
  * @sshdr:  optional decoded sense header
  * @timeout:    request timeout in HZ
  * @retries:    number of times to retry request
  * @flags:  flags for ->cmd_flags
  * @rq_flags:   flags for ->rq_flags
  * @resid:  optional residual length
  *
  * Returns the scsi_cmnd result field if a command was executed, or a negative
  * Linux error code if we didn't get that far.
  */
 int __scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
          int data_direction, void *buffer, unsigned bufflen,
          unsigned char *sense, struct scsi_sense_hdr *sshdr,
          int timeout, int retries, blk_opf_t flags,
          req_flags_t rq_flags, int *resid)
 {
     struct request *req;
     struct scsi_cmnd *scmd;
     int ret;
 
     req = scsi_alloc_request(sdev->request_queue,
             data_direction == DMA_TO_DEVICE ?
             REQ_OP_DRV_OUT : REQ_OP_DRV_IN,
             rq_flags & RQF_PM ? BLK_MQ_REQ_PM : 0);
     if (IS_ERR(req))
         return PTR_ERR(req);
 
     if (bufflen) {
         ret = blk_rq_map_kern(sdev->request_queue, req,
                       buffer, bufflen, GFP_NOIO);
         if (ret)
             goto out;
     }
     scmd = blk_mq_rq_to_pdu(req);
     scmd->cmd_len = COMMAND_SIZE(cmd[0]);
     memcpy(scmd->cmnd, cmd, scmd->cmd_len);
     scmd->allowed = retries;
     req->timeout = timeout;
     req->cmd_flags |= flags;
     req->rq_flags |= rq_flags | RQF_QUIET;
 
     /*
      * head injection *required* here otherwise quiesce won't work
      */
     blk_execute_rq(req, true);
 
     /*
      * Some devices (USB mass-storage in particular) may transfer
      * garbage data together with a residue indicating that the data
      * is invalid.  Prevent the garbage from being misinterpreted
      * and prevent security leaks by zeroing out the excess data.
      */
     if (unlikely(scmd->resid_len > 0 && scmd->resid_len <= bufflen))
         memset(buffer + bufflen - scmd->resid_len, 0, scmd->resid_len);
 
     if (resid)
         *resid = scmd->resid_len;
     if (sense && scmd->sense_len)
         memcpy(sense, scmd->sense_buffer, SCSI_SENSE_BUFFERSIZE);
     if (sshdr)
         scsi_normalize_sense(scmd->sense_buffer, scmd->sense_len,
                      sshdr);
     ret = scmd->result;
  out:
     blk_mq_free_request(req);
 
     return ret;
 }
 EXPORT_SYMBOL(__scsi_execute);
 
 /*
  * Wake up the error handler if necessary. Avoid as follows that the error
  * handler is not woken up if host in-flight requests number ==
  * shost->host_failed: use call_rcu() in scsi_eh_scmd_add() in combination
  * with an RCU read lock in this function to ensure that this function in
  * its entirety either finishes before scsi_eh_scmd_add() increases the
  * host_failed counter or that it notices the shost state change made by
  * scsi_eh_scmd_add().
  */
 static void scsi_dec_host_busy(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
 {
     unsigned long flags;
 
     rcu_read_lock();
     __clear_bit(SCMD_STATE_INFLIGHT, &cmd->state);
     if (unlikely(scsi_host_in_recovery(shost))) {
         spin_lock_irqsave(shost->host_lock, flags);
         if (shost->host_failed || shost->host_eh_scheduled)
             scsi_eh_wakeup(shost);
         spin_unlock_irqrestore(shost->host_lock, flags);
     }
     rcu_read_unlock();
 }
 
 void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd)
 {
     struct Scsi_Host *shost = sdev->host;
     struct scsi_target *starget = scsi_target(sdev);
 
     scsi_dec_host_busy(shost, cmd);
 
     if (starget->can_queue > 0)
         atomic_dec(&starget->target_busy);
 
     sbitmap_put(&sdev->budget_map, cmd->budget_token);
     cmd->budget_token = -1;
 }
 
 static void scsi_kick_queue(struct request_queue *q)
 {
     blk_mq_run_hw_queues(q, false);
 }
 
 /*
  * Called for single_lun devices on IO completion. Clear starget_sdev_user,
  * and call blk_run_queue for all the scsi_devices on the target -
  * including current_sdev first.
  *
  * Called with *no* scsi locks held.
  */
 static void scsi_single_lun_run(struct scsi_device *current_sdev)
 {
     struct Scsi_Host *shost = current_sdev->host;
     struct scsi_device *sdev, *tmp;
     struct scsi_target *starget = scsi_target(current_sdev);
     unsigned long flags;
 
     spin_lock_irqsave(shost->host_lock, flags);
     starget->starget_sdev_user = NULL;
     spin_unlock_irqrestore(shost->host_lock, flags);
 
     /*
      * Call blk_run_queue for all LUNs on the target, starting with
      * current_sdev. We race with others (to set starget_sdev_user),
      * but in most cases, we will be first. Ideally, each LU on the
      * target would get some limited time or requests on the target.
      */
     scsi_kick_queue(current_sdev->request_queue);
 
     spin_lock_irqsave(shost->host_lock, flags);
     if (starget->starget_sdev_user)
         goto out;
     list_for_each_entry_safe(sdev, tmp, &starget->devices,
             same_target_siblings) {
         if (sdev == current_sdev)
             continue;
         if (scsi_device_get(sdev))
             continue;
 
         spin_unlock_irqrestore(shost->host_lock, flags);
         scsi_kick_queue(sdev->request_queue);
         spin_lock_irqsave(shost->host_lock, flags);
 
         scsi_device_put(sdev);
     }
  out:
     spin_unlock_irqrestore(shost->host_lock, flags);
 }
 
 static inline bool scsi_device_is_busy(struct scsi_device *sdev)
 {
     if (scsi_device_busy(sdev) >= sdev->queue_depth)
         return true;
     if (atomic_read(&sdev->device_blocked) > 0)
         return true;
     return false;
 }
 
 static inline bool scsi_target_is_busy(struct scsi_target *starget)
 {
     if (starget->can_queue > 0) {
         if (atomic_read(&starget->target_busy) >= starget->can_queue)
             return true;
         if (atomic_read(&starget->target_blocked) > 0)
             return true;
     }
     return false;
 }
 
 static inline bool scsi_host_is_busy(struct Scsi_Host *shost)
 {
     if (atomic_read(&shost->host_blocked) > 0)
         return true;
     if (shost->host_self_blocked)
         return true;
     return false;
 }
 
 static void scsi_starved_list_run(struct Scsi_Host *shost)
 {
     LIST_HEAD(starved_list);
     struct scsi_device *sdev;
     unsigned long flags;
 
     spin_lock_irqsave(shost->host_lock, flags);
     list_splice_init(&shost->starved_list, &starved_list);
 
     while (!list_empty(&starved_list)) {
         struct request_queue *slq;
 
         /*
          * As long as shost is accepting commands and we have
          * starved queues, call blk_run_queue. scsi_request_fn
          * drops the queue_lock and can add us back to the
          * starved_list.
          *
          * host_lock protects the starved_list and starved_entry.
          * scsi_request_fn must get the host_lock before checking
          * or modifying starved_list or starved_entry.
          */
         if (scsi_host_is_busy(shost))
             break;
 
         sdev = list_entry(starved_list.next,
                   struct scsi_device, starved_entry);
         list_del_init(&sdev->starved_entry);
         if (scsi_target_is_busy(scsi_target(sdev))) {
             list_move_tail(&sdev->starved_entry,
                        &shost->starved_list);
             continue;
         }
 
         /*
          * Once we drop the host lock, a racing scsi_remove_device()
          * call may remove the sdev from the starved list and destroy
          * it and the queue.  Mitigate by taking a reference to the
          * queue and never touching the sdev again after we drop the
          * host lock.  Note: if __scsi_remove_device() invokes
          * blk_mq_destroy_queue() before the queue is run from this
          * function then blk_run_queue() will return immediately since
          * blk_mq_destroy_queue() marks the queue with QUEUE_FLAG_DYING.
          */
         slq = sdev->request_queue;
         if (!blk_get_queue(slq))
             continue;
         spin_unlock_irqrestore(shost->host_lock, flags);
 
         scsi_kick_queue(slq);
         blk_put_queue(slq);
 
         spin_lock_irqsave(shost->host_lock, flags);
     }
     /* put any unprocessed entries back */
     list_splice(&starved_list, &shost->starved_list);
     spin_unlock_irqrestore(shost->host_lock, flags);
 }
 
 /**
  * scsi_run_queue - Select a proper request queue to serve next.
  * @q:  last request's queue
  *
  * The previous command was completely finished, start a new one if possible.
  */
 static void scsi_run_queue(struct request_queue *q)
 {
     struct scsi_device *sdev = q->queuedata;
 
     if (scsi_target(sdev)->single_lun)
         scsi_single_lun_run(sdev);
     if (!list_empty(&sdev->host->starved_list))
         scsi_starved_list_run(sdev->host);
 
     blk_mq_run_hw_queues(q, false);
 }
 
 void scsi_requeue_run_queue(struct work_struct *work)
 {
     struct scsi_device *sdev;
     struct request_queue *q;
 
     sdev = container_of(work, struct scsi_device, requeue_work);
     q = sdev->request_queue;
     scsi_run_queue(q);
 }
 
 void scsi_run_host_queues(struct Scsi_Host *shost)
 {
     struct scsi_device *sdev;
 
     shost_for_each_device(sdev, shost)
         scsi_run_queue(sdev->request_queue);
 }
 
 static void scsi_uninit_cmd(struct scsi_cmnd *cmd)
 {
     if (!blk_rq_is_passthrough(scsi_cmd_to_rq(cmd))) {
         struct scsi_driver *drv = scsi_cmd_to_driver(cmd);
 
         if (drv->uninit_command)
             drv->uninit_command(cmd);
     }
 }
 
 void scsi_free_sgtables(struct scsi_cmnd *cmd)
 {
     if (cmd->sdb.table.nents)
         sg_free_table_chained(&cmd->sdb.table,
                 SCSI_INLINE_SG_CNT);
     if (scsi_prot_sg_count(cmd))
         sg_free_table_chained(&cmd->prot_sdb->table,
                 SCSI_INLINE_PROT_SG_CNT);
 }
 EXPORT_SYMBOL_GPL(scsi_free_sgtables);
 
 static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
 {
     scsi_free_sgtables(cmd);
     scsi_uninit_cmd(cmd);
 }
 
 static void scsi_run_queue_async(struct scsi_device *sdev)
 {
     if (scsi_target(sdev)->single_lun ||
         !list_empty(&sdev->host->starved_list)) {
         kblockd_schedule_work(&sdev->requeue_work);
     } else {
         /*
          * smp_mb() present in sbitmap_queue_clear() or implied in
          * .end_io is for ordering writing .device_busy in
          * scsi_device_unbusy() and reading sdev->restarts.
          */
         int old = atomic_read(&sdev->restarts);
 
         /*
          * ->restarts has to be kept as non-zero if new budget
          *  contention occurs.
          *
          *  No need to run queue when either another re-run
          *  queue wins in updating ->restarts or a new budget
          *  contention occurs.
          */
         if (old && atomic_cmpxchg(&sdev->restarts, old, 0) == old)
             blk_mq_run_hw_queues(sdev->request_queue, true);
     }
 }
 
 /* Returns false when no more bytes to process, true if there are more */
 static bool scsi_end_request(struct request *req, blk_status_t error,
         unsigned int bytes)
 {
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
     struct scsi_device *sdev = cmd->device;
     struct request_queue *q = sdev->request_queue;
 
     if (blk_update_request(req, error, bytes))
         return true;
 
     // XXX:
     if (blk_queue_add_random(q))
         add_disk_randomness(req->q->disk);
 
     if (!blk_rq_is_passthrough(req)) {
         WARN_ON_ONCE(!(cmd->flags & SCMD_INITIALIZED));
         cmd->flags &= ~SCMD_INITIALIZED;
     }
 
     /*
      * Calling rcu_barrier() is not necessary here because the
      * SCSI error handler guarantees that the function called by
      * call_rcu() has been called before scsi_end_request() is
      * called.
      */
     destroy_rcu_head(&cmd->rcu);
 
     /*
      * In the MQ case the command gets freed by __blk_mq_end_request,
      * so we have to do all cleanup that depends on it earlier.
      *
      * We also can't kick the queues from irq context, so we
      * will have to defer it to a workqueue.
      */
     scsi_mq_uninit_cmd(cmd);
 
     /*
      * queue is still alive, so grab the ref for preventing it
      * from being cleaned up during running queue.
      */
     percpu_ref_get(&q->q_usage_counter);
 
     __blk_mq_end_request(req, error);
 
     scsi_run_queue_async(sdev);
 
     percpu_ref_put(&q->q_usage_counter);
     return false;
 }
 
 /**
  * scsi_result_to_blk_status - translate a SCSI result code into blk_status_t
  * @cmd:    SCSI command
  * @result: scsi error code
  *
  * Translate a SCSI result code into a blk_status_t value. May reset the host
  * byte of @cmd->result.
  */
 static blk_status_t scsi_result_to_blk_status(struct scsi_cmnd *cmd, int result)
 {
     switch (host_byte(result)) {
     case DID_OK:
         if (scsi_status_is_good(result))
             return BLK_STS_OK;
         return BLK_STS_IOERR;
     case DID_TRANSPORT_FAILFAST:
     case DID_TRANSPORT_MARGINAL:
         return BLK_STS_TRANSPORT;
     case DID_TARGET_FAILURE:
         set_host_byte(cmd, DID_OK);
         return BLK_STS_TARGET;
     case DID_NEXUS_FAILURE:
         set_host_byte(cmd, DID_OK);
         return BLK_STS_NEXUS;
     case DID_ALLOC_FAILURE:
         set_host_byte(cmd, DID_OK);
         return BLK_STS_NOSPC;
     case DID_MEDIUM_ERROR:
         set_host_byte(cmd, DID_OK);
         return BLK_STS_MEDIUM;
     default:
         return BLK_STS_IOERR;
     }
 }
 
 /**
  * scsi_rq_err_bytes - determine number of bytes till the next failure boundary
  * @rq: request to examine
  *
  * Description:
  *     A request could be merge of IOs which require different failure
  *     handling.  This function determines the number of bytes which
  *     can be failed from the beginning of the request without
  *     crossing into area which need to be retried further.
  *
  * Return:
  *     The number of bytes to fail.
  */
 static unsigned int scsi_rq_err_bytes(const struct request *rq)
 {
     blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK;
     unsigned int bytes = 0;
     struct bio *bio;
 
     if (!(rq->rq_flags & RQF_MIXED_MERGE))
         return blk_rq_bytes(rq);
 
     /*
      * Currently the only 'mixing' which can happen is between
      * different fastfail types.  We can safely fail portions
      * which have all the failfast bits that the first one has -
      * the ones which are at least as eager to fail as the first
      * one.
      */
     for (bio = rq->bio; bio; bio = bio->bi_next) {
         if ((bio->bi_opf & ff) != ff)
             break;
         bytes += bio->bi_iter.bi_size;
     }
 
     /* this could lead to infinite loop */
     BUG_ON(blk_rq_bytes(rq) && !bytes);
     return bytes;
 }
 
 static bool scsi_cmd_runtime_exceeced(struct scsi_cmnd *cmd)
 {
     struct request *req = scsi_cmd_to_rq(cmd);
     unsigned long wait_for;
 
     if (cmd->allowed == SCSI_CMD_RETRIES_NO_LIMIT)
         return false;
 
     wait_for = (cmd->allowed + 1) * req->timeout;
     if (time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
         scmd_printk(KERN_ERR, cmd, "timing out command, waited %lus\n",
                 wait_for/HZ);
         return true;
     }
     return false;
 }
 
 /*
  * When ALUA transition state is returned, reprep the cmd to
  * use the ALUA handler's transition timeout. Delay the reprep
  * 1 sec to avoid aggressive retries of the target in that
  * state.
  */
 #define ALUA_TRANSITION_REPREP_DELAY    1000
 
 /* Helper for scsi_io_completion() when special action required. */
 static void scsi_io_completion_action(struct scsi_cmnd *cmd, int result)
 {
     struct request *req = scsi_cmd_to_rq(cmd);
     int level = 0;
     enum {ACTION_FAIL, ACTION_REPREP, ACTION_DELAYED_REPREP,
           ACTION_RETRY, ACTION_DELAYED_RETRY} action;
     struct scsi_sense_hdr sshdr;
     bool sense_valid;
     bool sense_current = true;      /* false implies "deferred sense" */
     blk_status_t blk_stat;
 
     sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
     if (sense_valid)
         sense_current = !scsi_sense_is_deferred(&sshdr);
 
     blk_stat = scsi_result_to_blk_status(cmd, result);
 
     if (host_byte(result) == DID_RESET) {
         /* Third party bus reset or reset for error recovery
          * reasons.  Just retry the command and see what
          * happens.
          */
         action = ACTION_RETRY;
     } else if (sense_valid && sense_current) {
         switch (sshdr.sense_key) {
         case UNIT_ATTENTION:
             if (cmd->device->removable) {
                 /* Detected disc change.  Set a bit
                  * and quietly refuse further access.
                  */
                 cmd->device->changed = 1;
                 action = ACTION_FAIL;
             } else {
                 /* Must have been a power glitch, or a
                  * bus reset.  Could not have been a
                  * media change, so we just retry the
                  * command and see what happens.
                  */
                 action = ACTION_RETRY;
             }
             break;
         case ILLEGAL_REQUEST:
             /* If we had an ILLEGAL REQUEST returned, then
              * we may have performed an unsupported
              * command.  The only thing this should be
              * would be a ten byte read where only a six
              * byte read was supported.  Also, on a system
              * where READ CAPACITY failed, we may have
              * read past the end of the disk.
              */
             if ((cmd->device->use_10_for_rw &&
                 sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
                 (cmd->cmnd[0] == READ_10 ||
                  cmd->cmnd[0] == WRITE_10)) {
                 /* This will issue a new 6-byte command. */
                 cmd->device->use_10_for_rw = 0;
                 action = ACTION_REPREP;
             } else if (sshdr.asc == 0x10) /* DIX */ {
                 action = ACTION_FAIL;
                 blk_stat = BLK_STS_PROTECTION;
             /* INVALID COMMAND OPCODE or INVALID FIELD IN CDB */
             } else if (sshdr.asc == 0x20 || sshdr.asc == 0x24) {
                 action = ACTION_FAIL;
                 blk_stat = BLK_STS_TARGET;
             } else
                 action = ACTION_FAIL;
             break;
         case ABORTED_COMMAND:
             action = ACTION_FAIL;
             if (sshdr.asc == 0x10) /* DIF */
                 blk_stat = BLK_STS_PROTECTION;
             break;
         case NOT_READY:
             /* If the device is in the process of becoming
              * ready, or has a temporary blockage, retry.
              */
             if (sshdr.asc == 0x04) {
                 switch (sshdr.ascq) {
                 case 0x01: /* becoming ready */
                 case 0x04: /* format in progress */
                 case 0x05: /* rebuild in progress */
                 case 0x06: /* recalculation in progress */
                 case 0x07: /* operation in progress */
                 case 0x08: /* Long write in progress */
                 case 0x09: /* self test in progress */
                 case 0x11: /* notify (enable spinup) required */
                 case 0x14: /* space allocation in progress */
                 case 0x1a: /* start stop unit in progress */
                 case 0x1b: /* sanitize in progress */
                 case 0x1d: /* configuration in progress */
                 case 0x24: /* depopulation in progress */
                     action = ACTION_DELAYED_RETRY;
                     break;
                 case 0x0a: /* ALUA state transition */
                     action = ACTION_DELAYED_REPREP;
                     break;
                 default:
                     action = ACTION_FAIL;
                     break;
                 }
             } else
                 action = ACTION_FAIL;
             break;
         case VOLUME_OVERFLOW:
             /* See SSC3rXX or current. */
             action = ACTION_FAIL;
             break;
         case DATA_PROTECT:
             action = ACTION_FAIL;
             if ((sshdr.asc == 0x0C && sshdr.ascq == 0x12) ||
                 (sshdr.asc == 0x55 &&
                  (sshdr.ascq == 0x0E || sshdr.ascq == 0x0F))) {
                 /* Insufficient zone resources */
                 blk_stat = BLK_STS_ZONE_OPEN_RESOURCE;
             }
             break;
         default:
             action = ACTION_FAIL;
             break;
         }
     } else
         action = ACTION_FAIL;
 
     if (action != ACTION_FAIL && scsi_cmd_runtime_exceeced(cmd))
         action = ACTION_FAIL;
 
     switch (action) {
     case ACTION_FAIL:
         /* Give up and fail the remainder of the request */
         if (!(req->rq_flags & RQF_QUIET)) {
             static DEFINE_RATELIMIT_STATE(_rs,
                     DEFAULT_RATELIMIT_INTERVAL,
                     DEFAULT_RATELIMIT_BURST);
 
             if (unlikely(scsi_logging_level))
                 level =
                      SCSI_LOG_LEVEL(SCSI_LOG_MLCOMPLETE_SHIFT,
                             SCSI_LOG_MLCOMPLETE_BITS);
 
             /*
              * if logging is enabled the failure will be printed
              * in scsi_log_completion(), so avoid duplicate messages
              */
             if (!level && __ratelimit(&_rs)) {
                 scsi_print_result(cmd, NULL, FAILED);
                 if (sense_valid)
                     scsi_print_sense(cmd);
                 scsi_print_command(cmd);
             }
         }
         if (!scsi_end_request(req, blk_stat, scsi_rq_err_bytes(req)))
             return;
         fallthrough;
     case ACTION_REPREP:
         scsi_mq_requeue_cmd(cmd, 0);
         break;
     case ACTION_DELAYED_REPREP:
         scsi_mq_requeue_cmd(cmd, ALUA_TRANSITION_REPREP_DELAY);
         break;
     case ACTION_RETRY:
         /* Retry the same command immediately */
         __scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, false);
         break;
     case ACTION_DELAYED_RETRY:
         /* Retry the same command after a delay */
         __scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, false);
         break;
     }
 }
 
 /*
  * Helper for scsi_io_completion() when cmd->result is non-zero. Returns a
  * new result that may suppress further error checking. Also modifies
  * *blk_statp in some cases.
  */
 static int scsi_io_completion_nz_result(struct scsi_cmnd *cmd, int result,
                     blk_status_t *blk_statp)
 {
     bool sense_valid;
     bool sense_current = true;  /* false implies "deferred sense" */
     struct request *req = scsi_cmd_to_rq(cmd);
     struct scsi_sense_hdr sshdr;
 
     sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
     if (sense_valid)
         sense_current = !scsi_sense_is_deferred(&sshdr);
 
     if (blk_rq_is_passthrough(req)) {
         if (sense_valid) {
             /*
              * SG_IO wants current and deferred errors
              */
             cmd->sense_len = min(8 + cmd->sense_buffer[7],
                          SCSI_SENSE_BUFFERSIZE);
         }
         if (sense_current)
             *blk_statp = scsi_result_to_blk_status(cmd, result);
     } else if (blk_rq_bytes(req) == 0 && sense_current) {
         /*
          * Flush commands do not transfers any data, and thus cannot use
          * good_bytes != blk_rq_bytes(req) as the signal for an error.
          * This sets *blk_statp explicitly for the problem case.
          */
         *blk_statp = scsi_result_to_blk_status(cmd, result);
     }
     /*
      * Recovered errors need reporting, but they're always treated as
      * success, so fiddle the result code here.  For passthrough requests
      * we already took a copy of the original into sreq->result which
      * is what gets returned to the user
      */
     if (sense_valid && (sshdr.sense_key == RECOVERED_ERROR)) {
         bool do_print = true;
         /*
          * if ATA PASS-THROUGH INFORMATION AVAILABLE [0x0, 0x1d]
          * skip print since caller wants ATA registers. Only occurs
          * on SCSI ATA PASS_THROUGH commands when CK_COND=1
          */
         if ((sshdr.asc == 0x0) && (sshdr.ascq == 0x1d))
             do_print = false;
         else if (req->rq_flags & RQF_QUIET)
             do_print = false;
         if (do_print)
             scsi_print_sense(cmd);
         result = 0;
         /* for passthrough, *blk_statp may be set */
         *blk_statp = BLK_STS_OK;
     }
     /*
      * Another corner case: the SCSI status byte is non-zero but 'good'.
      * Example: PRE-FETCH command returns SAM_STAT_CONDITION_MET when
      * it is able to fit nominated LBs in its cache (and SAM_STAT_GOOD
      * if it can't fit). Treat SAM_STAT_CONDITION_MET and the related
      * intermediate statuses (both obsolete in SAM-4) as good.
      */
     if ((result & 0xff) && scsi_status_is_good(result)) {
         result = 0;
         *blk_statp = BLK_STS_OK;
     }
     return result;
 }
 
 /**
  * scsi_io_completion - Completion processing for SCSI commands.
  * @cmd:    command that is finished.
  * @good_bytes: number of processed bytes.
  *
  * We will finish off the specified number of sectors. If we are done, the
  * command block will be released and the queue function will be goosed. If we
  * are not done then we have to figure out what to do next:
  *
  *   a) We can call scsi_mq_requeue_cmd().  The request will be
  *  unprepared and put back on the queue.  Then a new command will
  *  be created for it.  This should be used if we made forward
  *  progress, or if we want to switch from READ(10) to READ(6) for
  *  example.
  *
  *   b) We can call scsi_io_completion_action().  The request will be
  *  put back on the queue and retried using the same command as
  *  before, possibly after a delay.
  *
  *   c) We can call scsi_end_request() with blk_stat other than
  *  BLK_STS_OK, to fail the remainder of the request.
  */
 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 {
     int result = cmd->result;
     struct request *req = scsi_cmd_to_rq(cmd);
     blk_status_t blk_stat = BLK_STS_OK;
 
     if (unlikely(result))   /* a nz result may or may not be an error */
         result = scsi_io_completion_nz_result(cmd, result, &blk_stat);
 
     /*
      * Next deal with any sectors which we were able to correctly
      * handle.
      */
     SCSI_LOG_HLCOMPLETE(1, scmd_printk(KERN_INFO, cmd,
         "%u sectors total, %d bytes done.\n",
         blk_rq_sectors(req), good_bytes));
 
     /*
      * Failed, zero length commands always need to drop down
      * to retry code. Fast path should return in this block.
      */
     if (likely(blk_rq_bytes(req) > 0 || blk_stat == BLK_STS_OK)) {
         if (likely(!scsi_end_request(req, blk_stat, good_bytes)))
             return; /* no bytes remaining */
     }
 
     /* Kill remainder if no retries. */
     if (unlikely(blk_stat && scsi_noretry_cmd(cmd))) {
         if (scsi_end_request(req, blk_stat, blk_rq_bytes(req)))
             WARN_ONCE(true,
                 "Bytes remaining after failed, no-retry command");
         return;
     }
 
     /*
      * If there had been no error, but we have leftover bytes in the
      * request just queue the command up again.
      */
     if (likely(result == 0))
         scsi_mq_requeue_cmd(cmd, 0);
     else
         scsi_io_completion_action(cmd, result);
 }
 
 static inline bool scsi_cmd_needs_dma_drain(struct scsi_device *sdev,
         struct request *rq)
 {
     return sdev->dma_drain_len && blk_rq_is_passthrough(rq) &&
            !op_is_write(req_op(rq)) &&
            sdev->host->hostt->dma_need_drain(rq);
 }
 
 /**
  * scsi_alloc_sgtables - Allocate and initialize data and integrity scatterlists
  * @cmd: SCSI command data structure to initialize.
  *
  * Initializes @cmd->sdb and also @cmd->prot_sdb if data integrity is enabled
  * for @cmd.
  *
  * Returns:
  * * BLK_STS_OK       - on success
  * * BLK_STS_RESOURCE - if the failure is retryable
  * * BLK_STS_IOERR    - if the failure is fatal
  */
 blk_status_t scsi_alloc_sgtables(struct scsi_cmnd *cmd)
 {
     struct scsi_device *sdev = cmd->device;
     struct request *rq = scsi_cmd_to_rq(cmd);
     unsigned short nr_segs = blk_rq_nr_phys_segments(rq);
     struct scatterlist *last_sg = NULL;
     blk_status_t ret;
     bool need_drain = scsi_cmd_needs_dma_drain(sdev, rq);
     int count;
 
     if (WARN_ON_ONCE(!nr_segs))
         return BLK_STS_IOERR;
 
     /*
      * Make sure there is space for the drain.  The driver must adjust
      * max_hw_segments to be prepared for this.
      */
     if (need_drain)
         nr_segs++;
 
     /*
      * If sg table allocation fails, requeue request later.
      */
     if (unlikely(sg_alloc_table_chained(&cmd->sdb.table, nr_segs,
             cmd->sdb.table.sgl, SCSI_INLINE_SG_CNT)))
         return BLK_STS_RESOURCE;
 
     /*
      * Next, walk the list, and fill in the addresses and sizes of
      * each segment.
      */
     count = __blk_rq_map_sg(rq->q, rq, cmd->sdb.table.sgl, &last_sg);
 
     if (blk_rq_bytes(rq) & rq->q->dma_pad_mask) {
         unsigned int pad_len =
             (rq->q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
 
         last_sg->length += pad_len;
         cmd->extra_len += pad_len;
     }
 
     if (need_drain) {
         sg_unmark_end(last_sg);
         last_sg = sg_next(last_sg);
         sg_set_buf(last_sg, sdev->dma_drain_buf, sdev->dma_drain_len);
         sg_mark_end(last_sg);
 
         cmd->extra_len += sdev->dma_drain_len;
         count++;
     }
 
     BUG_ON(count > cmd->sdb.table.nents);
     cmd->sdb.table.nents = count;
     cmd->sdb.length = blk_rq_payload_bytes(rq);
 
     if (blk_integrity_rq(rq)) {
         struct scsi_data_buffer *prot_sdb = cmd->prot_sdb;
         int ivecs;
 
         if (WARN_ON_ONCE(!prot_sdb)) {
             /*
              * This can happen if someone (e.g. multipath)
              * queues a command to a device on an adapter
              * that does not support DIX.
              */
             ret = BLK_STS_IOERR;
             goto out_free_sgtables;
         }
 
         ivecs = blk_rq_count_integrity_sg(rq->q, rq->bio);
 
         if (sg_alloc_table_chained(&prot_sdb->table, ivecs,
                 prot_sdb->table.sgl,
                 SCSI_INLINE_PROT_SG_CNT)) {
             ret = BLK_STS_RESOURCE;
             goto out_free_sgtables;
         }
 
         count = blk_rq_map_integrity_sg(rq->q, rq->bio,
                         prot_sdb->table.sgl);
         BUG_ON(count > ivecs);
         BUG_ON(count > queue_max_integrity_segments(rq->q));
 
         cmd->prot_sdb = prot_sdb;
         cmd->prot_sdb->table.nents = count;
     }
 
     return BLK_STS_OK;
 out_free_sgtables:
     scsi_free_sgtables(cmd);
     return ret;
 }
 EXPORT_SYMBOL(scsi_alloc_sgtables);
 
 /**
  * scsi_initialize_rq - initialize struct scsi_cmnd partially
  * @rq: Request associated with the SCSI command to be initialized.
  *
  * This function initializes the members of struct scsi_cmnd that must be
  * initialized before request processing starts and that won't be
  * reinitialized if a SCSI command is requeued.
  */
 static void scsi_initialize_rq(struct request *rq)
 {
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
     memset(cmd->cmnd, 0, sizeof(cmd->cmnd));
     cmd->cmd_len = MAX_COMMAND_SIZE;
     cmd->sense_len = 0;
     init_rcu_head(&cmd->rcu);
     cmd->jiffies_at_alloc = jiffies;
     cmd->retries = 0;
 }
 
 struct request *scsi_alloc_request(struct request_queue *q, blk_opf_t opf,
                    blk_mq_req_flags_t flags)
 {
     struct request *rq;
 
     rq = blk_mq_alloc_request(q, opf, flags);
     if (!IS_ERR(rq))
         scsi_initialize_rq(rq);
     return rq;
 }
 EXPORT_SYMBOL_GPL(scsi_alloc_request);
 
 /*
  * Only called when the request isn't completed by SCSI, and not freed by
  * SCSI
  */
 static void scsi_cleanup_rq(struct request *rq)
 {
     if (rq->rq_flags & RQF_DONTPREP) {
         scsi_mq_uninit_cmd(blk_mq_rq_to_pdu(rq));
         rq->rq_flags &= ~RQF_DONTPREP;
     }
 }
 
 /* Called before a request is prepared. See also scsi_mq_prep_fn(). */
 void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 {
     struct request *rq = scsi_cmd_to_rq(cmd);
 
     if (!blk_rq_is_passthrough(rq) && !(cmd->flags & SCMD_INITIALIZED)) {
         cmd->flags |= SCMD_INITIALIZED;
         scsi_initialize_rq(rq);
     }
 
     cmd->device = dev;
     INIT_LIST_HEAD(&cmd->eh_entry);
     INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
 }
 
 static blk_status_t scsi_setup_scsi_cmnd(struct scsi_device *sdev,
         struct request *req)
 {
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
 
     /*
      * Passthrough requests may transfer data, in which case they must
      * a bio attached to them.  Or they might contain a SCSI command
      * that does not transfer data, in which case they may optionally
      * submit a request without an attached bio.
      */
     if (req->bio) {
         blk_status_t ret = scsi_alloc_sgtables(cmd);
         if (unlikely(ret != BLK_STS_OK))
             return ret;
     } else {
         BUG_ON(blk_rq_bytes(req));
 
         memset(&cmd->sdb, 0, sizeof(cmd->sdb));
     }
 
     cmd->transfersize = blk_rq_bytes(req);
     return BLK_STS_OK;
 }
 
 static blk_status_t
 scsi_device_state_check(struct scsi_device *sdev, struct request *req)
 {
     switch (sdev->sdev_state) {
     case SDEV_CREATED:
         return BLK_STS_OK;
     case SDEV_OFFLINE:
     case SDEV_TRANSPORT_OFFLINE:
         /*
          * If the device is offline we refuse to process any
          * commands.  The device must be brought online
          * before trying any recovery commands.
          */
         if (!sdev->offline_already) {
             sdev->offline_already = true;
             sdev_printk(KERN_ERR, sdev,
                     "rejecting I/O to offline device\n");
         }
         return BLK_STS_IOERR;
     case SDEV_DEL:
         /*
          * If the device is fully deleted, we refuse to
          * process any commands as well.
          */
         sdev_printk(KERN_ERR, sdev,
                 "rejecting I/O to dead device\n");
         return BLK_STS_IOERR;
     case SDEV_BLOCK:
     case SDEV_CREATED_BLOCK:
         return BLK_STS_RESOURCE;
     case SDEV_QUIESCE:
         /*
          * If the device is blocked we only accept power management
          * commands.
          */
         if (req && WARN_ON_ONCE(!(req->rq_flags & RQF_PM)))
             return BLK_STS_RESOURCE;
         return BLK_STS_OK;
     default:
         /*
          * For any other not fully online state we only allow
          * power management commands.
          */
         if (req && !(req->rq_flags & RQF_PM))
             return BLK_STS_OFFLINE;
         return BLK_STS_OK;
     }
 }
 
 /*
  * scsi_dev_queue_ready: if we can send requests to sdev, assign one token
  * and return the token else return -1.
  */
 static inline int scsi_dev_queue_ready(struct request_queue *q,
                   struct scsi_device *sdev)
 {
     int token;
 
     token = sbitmap_get(&sdev->budget_map);
     if (atomic_read(&sdev->device_blocked)) {
         if (token < 0)
             goto out;
 
         if (scsi_device_busy(sdev) > 1)
             goto out_dec;
 
         /*
          * unblock after device_blocked iterates to zero
          */
         if (atomic_dec_return(&sdev->device_blocked) > 0)
             goto out_dec;
         SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
                    "unblocking device at zero depth\n"));
     }
 
     return token;
 out_dec:
     if (token >= 0)
         sbitmap_put(&sdev->budget_map, token);
 out:
     return -1;
 }
 
 /*
  * scsi_target_queue_ready: checks if there we can send commands to target
  * @sdev: scsi device on starget to check.
  */
 static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
                        struct scsi_device *sdev)
 {
     struct scsi_target *starget = scsi_target(sdev);
     unsigned int busy;
 
     if (starget->single_lun) {
         spin_lock_irq(shost->host_lock);
         if (starget->starget_sdev_user &&
             starget->starget_sdev_user != sdev) {
             spin_unlock_irq(shost->host_lock);
             return 0;
         }
         starget->starget_sdev_user = sdev;
         spin_unlock_irq(shost->host_lock);
     }
 
     if (starget->can_queue <= 0)
         return 1;
 
     busy = atomic_inc_return(&starget->target_busy) - 1;
     if (atomic_read(&starget->target_blocked) > 0) {
         if (busy)
             goto starved;
 
         /*
          * unblock after target_blocked iterates to zero
          */
         if (atomic_dec_return(&starget->target_blocked) > 0)
             goto out_dec;
 
         SCSI_LOG_MLQUEUE(3, starget_printk(KERN_INFO, starget,
                  "unblocking target at zero depth\n"));
     }
 
     if (busy >= starget->can_queue)
         goto starved;
 
     return 1;
 
 starved:
     spin_lock_irq(shost->host_lock);
     list_move_tail(&sdev->starved_entry, &shost->starved_list);
     spin_unlock_irq(shost->host_lock);
 out_dec:
     if (starget->can_queue > 0)
         atomic_dec(&starget->target_busy);
     return 0;
 }
 
 /*
  * scsi_host_queue_ready: if we can send requests to shost, return 1 else
  * return 0. We must end up running the queue again whenever 0 is
  * returned, else IO can hang.
  */
 static inline int scsi_host_queue_ready(struct request_queue *q,
                    struct Scsi_Host *shost,
                    struct scsi_device *sdev,
                    struct scsi_cmnd *cmd)
 {
     if (scsi_host_in_recovery(shost))
         return 0;
 
     if (atomic_read(&shost->host_blocked) > 0) {
         if (scsi_host_busy(shost) > 0)
             goto starved;
 
         /*
          * unblock after host_blocked iterates to zero
          */
         if (atomic_dec_return(&shost->host_blocked) > 0)
             goto out_dec;
 
         SCSI_LOG_MLQUEUE(3,
             shost_printk(KERN_INFO, shost,
                      "unblocking host at zero depth\n"));
     }
 
     if (shost->host_self_blocked)
         goto starved;
 
     /* We're OK to process the command, so we can't be starved */
     if (!list_empty(&sdev->starved_entry)) {
         spin_lock_irq(shost->host_lock);
         if (!list_empty(&sdev->starved_entry))
             list_del_init(&sdev->starved_entry);
         spin_unlock_irq(shost->host_lock);
     }
 
     __set_bit(SCMD_STATE_INFLIGHT, &cmd->state);
 
     return 1;
 
 starved:
     spin_lock_irq(shost->host_lock);
     if (list_empty(&sdev->starved_entry))
         list_add_tail(&sdev->starved_entry, &shost->starved_list);
     spin_unlock_irq(shost->host_lock);
 out_dec:
     scsi_dec_host_busy(shost, cmd);
     return 0;
 }
 
 /*
  * Busy state exporting function for request stacking drivers.
  *
  * For efficiency, no lock is taken to check the busy state of
  * shost/starget/sdev, since the returned value is not guaranteed and
  * may be changed after request stacking drivers call the function,
  * regardless of taking lock or not.
  *
  * When scsi can't dispatch I/Os anymore and needs to kill I/Os scsi
  * needs to return 'not busy'. Otherwise, request stacking drivers
  * may hold requests forever.
  */
 static bool scsi_mq_lld_busy(struct request_queue *q)
 {
     struct scsi_device *sdev = q->queuedata;
     struct Scsi_Host *shost;
 
     if (blk_queue_dying(q))
         return false;
 
     shost = sdev->host;
 
     /*
      * Ignore host/starget busy state.
      * Since block layer does not have a concept of fairness across
      * multiple queues, congestion of host/starget needs to be handled
      * in SCSI layer.
      */
     if (scsi_host_in_recovery(shost) || scsi_device_is_busy(sdev))
         return true;
 
     return false;
 }
 
 /*
  * Block layer request completion callback. May be called from interrupt
  * context.
  */
 static void scsi_complete(struct request *rq)
 {
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
     enum scsi_disposition disposition;
 
     INIT_LIST_HEAD(&cmd->eh_entry);
 
     atomic_inc(&cmd->device->iodone_cnt);
     if (cmd->result)
         atomic_inc(&cmd->device->ioerr_cnt);
 
     disposition = scsi_decide_disposition(cmd);
     if (disposition != SUCCESS && scsi_cmd_runtime_exceeced(cmd))
         disposition = SUCCESS;
 
     scsi_log_completion(cmd, disposition);
 
     switch (disposition) {
     case SUCCESS:
         scsi_finish_command(cmd);
         break;
     case NEEDS_RETRY:
         scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY);
         break;
     case ADD_TO_MLQUEUE:
         scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
         break;
     default:
         scsi_eh_scmd_add(cmd);
         break;
     }
 }
 
 /**
  * scsi_dispatch_cmd - Dispatch a command to the low-level driver.
  * @cmd: command block we are dispatching.
  *
  * Return: nonzero return request was rejected and device's queue needs to be
  * plugged.
  */
 static int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 {
     struct Scsi_Host *host = cmd->device->host;
     int rtn = 0;
 
     atomic_inc(&cmd->device->iorequest_cnt);
 
     /* check if the device is still usable */
     if (unlikely(cmd->device->sdev_state == SDEV_DEL)) {
         /* in SDEV_DEL we error all commands. DID_NO_CONNECT
          * returns an immediate error upwards, and signals
          * that the device is no longer present */
         cmd->result = DID_NO_CONNECT << 16;
         goto done;
     }
 
     /* Check to see if the scsi lld made this device blocked. */
     if (unlikely(scsi_device_blocked(cmd->device))) {
         /*
          * in blocked state, the command is just put back on
          * the device queue.  The suspend state has already
          * blocked the queue so future requests should not
          * occur until the device transitions out of the
          * suspend state.
          */
         SCSI_LOG_MLQUEUE(3, scmd_printk(KERN_INFO, cmd,
             "queuecommand : device blocked\n"));
         return SCSI_MLQUEUE_DEVICE_BUSY;
     }
 
     /* Store the LUN value in cmnd, if needed. */
     if (cmd->device->lun_in_cdb)
         cmd->cmnd[1] = (cmd->cmnd[1] & 0x1f) |
                    (cmd->device->lun << 5 & 0xe0);
 
     scsi_log_send(cmd);
 
     /*
      * Before we queue this command, check if the command
      * length exceeds what the host adapter can handle.
      */
     if (cmd->cmd_len > cmd->device->host->max_cmd_len) {
         SCSI_LOG_MLQUEUE(3, scmd_printk(KERN_INFO, cmd,
                    "queuecommand : command too long. "
                    "cdb_size=%d host->max_cmd_len=%d\n",
                    cmd->cmd_len, cmd->device->host->max_cmd_len));
         cmd->result = (DID_ABORT << 16);
         goto done;
     }
 
     if (unlikely(host->shost_state == SHOST_DEL)) {
         cmd->result = (DID_NO_CONNECT << 16);
         goto done;
 
     }
 
     trace_scsi_dispatch_cmd_start(cmd);
     rtn = host->hostt->queuecommand(host, cmd);
     if (rtn) {
         trace_scsi_dispatch_cmd_error(cmd, rtn);
         if (rtn != SCSI_MLQUEUE_DEVICE_BUSY &&
             rtn != SCSI_MLQUEUE_TARGET_BUSY)
             rtn = SCSI_MLQUEUE_HOST_BUSY;
 
         SCSI_LOG_MLQUEUE(3, scmd_printk(KERN_INFO, cmd,
             "queuecommand : request rejected\n"));
     }
 
     return rtn;
  done:
     scsi_done(cmd);
     return 0;
 }
 
 /* Size in bytes of the sg-list stored in the scsi-mq command-private data. */
 static unsigned int scsi_mq_inline_sgl_size(struct Scsi_Host *shost)
 {
     return min_t(unsigned int, shost->sg_tablesize, SCSI_INLINE_SG_CNT) *
         sizeof(struct scatterlist);
 }
 
 static blk_status_t scsi_prepare_cmd(struct request *req)
 {
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
     struct scsi_device *sdev = req->q->queuedata;
     struct Scsi_Host *shost = sdev->host;
     bool in_flight = test_bit(SCMD_STATE_INFLIGHT, &cmd->state);
     struct scatterlist *sg;
 
     scsi_init_command(sdev, cmd);
 
     cmd->eh_eflags = 0;
     cmd->prot_type = 0;
     cmd->prot_flags = 0;
     cmd->submitter = 0;
     memset(&cmd->sdb, 0, sizeof(cmd->sdb));
     cmd->underflow = 0;
     cmd->transfersize = 0;
     cmd->host_scribble = NULL;
     cmd->result = 0;
     cmd->extra_len = 0;
     cmd->state = 0;
     if (in_flight)
         __set_bit(SCMD_STATE_INFLIGHT, &cmd->state);
 
     /*
      * Only clear the driver-private command data if the LLD does not supply
      * a function to initialize that data.
      */
     if (!shost->hostt->init_cmd_priv)
         memset(cmd + 1, 0, shost->hostt->cmd_size);
 
     cmd->prot_op = SCSI_PROT_NORMAL;
     if (blk_rq_bytes(req))
         cmd->sc_data_direction = rq_dma_dir(req);
     else
         cmd->sc_data_direction = DMA_NONE;
 
     sg = (void *)cmd + sizeof(struct scsi_cmnd) + shost->hostt->cmd_size;
     cmd->sdb.table.sgl = sg;
 
     if (scsi_host_get_prot(shost)) {
         memset(cmd->prot_sdb, 0, sizeof(struct scsi_data_buffer));
 
         cmd->prot_sdb->table.sgl =
             (struct scatterlist *)(cmd->prot_sdb + 1);
     }
 
     /*
      * Special handling for passthrough commands, which don't go to the ULP
      * at all:
      */
     if (blk_rq_is_passthrough(req))
         return scsi_setup_scsi_cmnd(sdev, req);
 
     if (sdev->handler && sdev->handler->prep_fn) {
         blk_status_t ret = sdev->handler->prep_fn(sdev, req);
 
         if (ret != BLK_STS_OK)
             return ret;
     }
 
     /* Usually overridden by the ULP */
     cmd->allowed = 0;
     memset(cmd->cmnd, 0, sizeof(cmd->cmnd));
     return scsi_cmd_to_driver(cmd)->init_command(cmd);
 }
 
 static void scsi_done_internal(struct scsi_cmnd *cmd, bool complete_directly)
 {
     struct request *req = scsi_cmd_to_rq(cmd);
 
     switch (cmd->submitter) {
     case SUBMITTED_BY_BLOCK_LAYER:
         break;
     case SUBMITTED_BY_SCSI_ERROR_HANDLER:
         return scsi_eh_done(cmd);
     case SUBMITTED_BY_SCSI_RESET_IOCTL:
         return;
     }
 
     if (unlikely(blk_should_fake_timeout(scsi_cmd_to_rq(cmd)->q)))
         return;
     if (unlikely(test_and_set_bit(SCMD_STATE_COMPLETE, &cmd->state)))
         return;
     trace_scsi_dispatch_cmd_done(cmd);
 
     if (complete_directly)
         blk_mq_complete_request_direct(req, scsi_complete);
     else
         blk_mq_complete_request(req);
 }
 
 void scsi_done(struct scsi_cmnd *cmd)
 {
     scsi_done_internal(cmd, false);
 }
 EXPORT_SYMBOL(scsi_done);
 
 void scsi_done_direct(struct scsi_cmnd *cmd)
 {
     scsi_done_internal(cmd, true);
 }
 EXPORT_SYMBOL(scsi_done_direct);
 
 static void scsi_mq_put_budget(struct request_queue *q, int budget_token)
 {
     struct scsi_device *sdev = q->queuedata;
 
     sbitmap_put(&sdev->budget_map, budget_token);
 }
 
 /*
  * When to reinvoke queueing after a resource shortage. It's 3 msecs to
  * not change behaviour from the previous unplug mechanism, experimentation
  * may prove this needs changing.
  */
 #define SCSI_QUEUE_DELAY 3
 
 static int scsi_mq_get_budget(struct request_queue *q)
 {
     struct scsi_device *sdev = q->queuedata;
     int token = scsi_dev_queue_ready(q, sdev);
 
     if (token >= 0)
         return token;
 
     atomic_inc(&sdev->restarts);
 
     /*
      * Orders atomic_inc(&sdev->restarts) and atomic_read(&sdev->device_busy).
      * .restarts must be incremented before .device_busy is read because the
      * code in scsi_run_queue_async() depends on the order of these operations.
      */
     smp_mb__after_atomic();
 
     /*
      * If all in-flight requests originated from this LUN are completed
      * before reading .device_busy, sdev->device_busy will be observed as
      * zero, then blk_mq_delay_run_hw_queues() will dispatch this request
      * soon. Otherwise, completion of one of these requests will observe
      * the .restarts flag, and the request queue will be run for handling
      * this request, see scsi_end_request().
      */
     if (unlikely(scsi_device_busy(sdev) == 0 &&
                 !scsi_device_blocked(sdev)))
         blk_mq_delay_run_hw_queues(sdev->request_queue, SCSI_QUEUE_DELAY);
     return -1;
 }
 
 static void scsi_mq_set_rq_budget_token(struct request *req, int token)
 {
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
 
     cmd->budget_token = token;
 }
 
 static int scsi_mq_get_rq_budget_token(struct request *req)
 {
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
 
     return cmd->budget_token;
 }
 
 static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
              const struct blk_mq_queue_data *bd)
 {
     struct request *req = bd->rq;
     struct request_queue *q = req->q;
     struct scsi_device *sdev = q->queuedata;
     struct Scsi_Host *shost = sdev->host;
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
     blk_status_t ret;
     int reason;
 
     WARN_ON_ONCE(cmd->budget_token < 0);
 
     /*
      * If the device is not in running state we will reject some or all
      * commands.
      */
     if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
         ret = scsi_device_state_check(sdev, req);
         if (ret != BLK_STS_OK)
             goto out_put_budget;
     }
 
     ret = BLK_STS_RESOURCE;
     if (!scsi_target_queue_ready(shost, sdev))
         goto out_put_budget;
     if (!scsi_host_queue_ready(q, shost, sdev, cmd))
         goto out_dec_target_busy;
 
     if (!(req->rq_flags & RQF_DONTPREP)) {
         ret = scsi_prepare_cmd(req);
         if (ret != BLK_STS_OK)
             goto out_dec_host_busy;
         req->rq_flags |= RQF_DONTPREP;
     } else {
         clear_bit(SCMD_STATE_COMPLETE, &cmd->state);
     }
 
     cmd->flags &= SCMD_PRESERVED_FLAGS;
     if (sdev->simple_tags)
         cmd->flags |= SCMD_TAGGED;
     if (bd->last)
         cmd->flags |= SCMD_LAST;
 
     scsi_set_resid(cmd, 0);
     memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
     cmd->submitter = SUBMITTED_BY_BLOCK_LAYER;
 
     blk_mq_start_request(req);
     reason = scsi_dispatch_cmd(cmd);
     if (reason) {
         scsi_set_blocked(cmd, reason);
         ret = BLK_STS_RESOURCE;
         goto out_dec_host_busy;
     }
 
     return BLK_STS_OK;
 
 out_dec_host_busy:
     scsi_dec_host_busy(shost, cmd);
 out_dec_target_busy:
     if (scsi_target(sdev)->can_queue > 0)
         atomic_dec(&scsi_target(sdev)->target_busy);
 out_put_budget:
     scsi_mq_put_budget(q, cmd->budget_token);
     cmd->budget_token = -1;
     switch (ret) {
     case BLK_STS_OK:
         break;
     case BLK_STS_RESOURCE:
     case BLK_STS_ZONE_RESOURCE:
         if (scsi_device_blocked(sdev))
             ret = BLK_STS_DEV_RESOURCE;
         break;
     case BLK_STS_AGAIN:
         cmd->result = DID_BUS_BUSY << 16;
         if (req->rq_flags & RQF_DONTPREP)
             scsi_mq_uninit_cmd(cmd);
         break;
     default:
         if (unlikely(!scsi_device_online(sdev)))
             cmd->result = DID_NO_CONNECT << 16;
         else
             cmd->result = DID_ERROR << 16;
         /*
          * Make sure to release all allocated resources when
          * we hit an error, as we will never see this command
          * again.
          */
         if (req->rq_flags & RQF_DONTPREP)
             scsi_mq_uninit_cmd(cmd);
         scsi_run_queue_async(sdev);
         break;
     }
     return ret;
 }
 
 static int scsi_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
                 unsigned int hctx_idx, unsigned int numa_node)
 {
     struct Scsi_Host *shost = set->driver_data;
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
     struct scatterlist *sg;
     int ret = 0;
 
     cmd->sense_buffer =
         kmem_cache_alloc_node(scsi_sense_cache, GFP_KERNEL, numa_node);
     if (!cmd->sense_buffer)
         return -ENOMEM;
 
     if (scsi_host_get_prot(shost)) {
         sg = (void *)cmd + sizeof(struct scsi_cmnd) +
             shost->hostt->cmd_size;
         cmd->prot_sdb = (void *)sg + scsi_mq_inline_sgl_size(shost);
     }
 
     if (shost->hostt->init_cmd_priv) {
         ret = shost->hostt->init_cmd_priv(shost, cmd);
         if (ret < 0)
             kmem_cache_free(scsi_sense_cache, cmd->sense_buffer);
     }
 
     return ret;
 }
 
 static void scsi_mq_exit_request(struct blk_mq_tag_set *set, struct request *rq,
                  unsigned int hctx_idx)
 {
     struct Scsi_Host *shost = set->driver_data;
     struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
     if (shost->hostt->exit_cmd_priv)
         shost->hostt->exit_cmd_priv(shost, cmd);
     kmem_cache_free(scsi_sense_cache, cmd->sense_buffer);
 }
 
 
 static int scsi_mq_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob)
 {
     struct Scsi_Host *shost = hctx->driver_data;
 
     if (shost->hostt->mq_poll)
         return shost->hostt->mq_poll(shost, hctx->queue_num);
 
     return 0;
 }
 
 static int scsi_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
               unsigned int hctx_idx)
 {
     struct Scsi_Host *shost = data;
 
     hctx->driver_data = shost;
     return 0;
 }
 
 static int scsi_map_queues(struct blk_mq_tag_set *set)
 {
     struct Scsi_Host *shost = container_of(set, struct Scsi_Host, tag_set);
 
     if (shost->hostt->map_queues)
         return shost->hostt->map_queues(shost);
     return blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
 }
 
 void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
 {
     struct device *dev = shost->dma_dev;
 
     /*
      * this limit is imposed by hardware restrictions
      */
     blk_queue_max_segments(q, min_t(unsigned short, shost->sg_tablesize,
                     SG_MAX_SEGMENTS));
 
     if (scsi_host_prot_dma(shost)) {
         shost->sg_prot_tablesize =
             min_not_zero(shost->sg_prot_tablesize,
                      (unsigned short)SCSI_MAX_PROT_SG_SEGMENTS);
         BUG_ON(shost->sg_prot_tablesize < shost->sg_tablesize);
         blk_queue_max_integrity_segments(q, shost->sg_prot_tablesize);
     }
 
     blk_queue_max_hw_sectors(q, shost->max_sectors);
     blk_queue_segment_boundary(q, shost->dma_boundary);
     dma_set_seg_boundary(dev, shost->dma_boundary);
 
     blk_queue_max_segment_size(q, shost->max_segment_size);
     blk_queue_virt_boundary(q, shost->virt_boundary_mask);
     dma_set_max_seg_size(dev, queue_max_segment_size(q));
 
     /*
      * Set a reasonable default alignment:  The larger of 32-byte (dword),
      * which is a common minimum for HBAs, and the minimum DMA alignment,
      * which is set by the platform.
      *
      * Devices that require a bigger alignment can increase it later.
      */
     blk_queue_dma_alignment(q, max(4, dma_get_cache_alignment()) - 1);
 }
 EXPORT_SYMBOL_GPL(__scsi_init_queue);
 
 static const struct blk_mq_ops scsi_mq_ops_no_commit = {
     .get_budget = scsi_mq_get_budget,
     .put_budget = scsi_mq_put_budget,
     .queue_rq   = scsi_queue_rq,
     .complete   = scsi_complete,
     .timeout    = scsi_timeout,
 #ifdef CONFIG_BLK_DEBUG_FS
     .show_rq    = scsi_show_rq,
 #endif
     .init_request   = scsi_mq_init_request,
     .exit_request   = scsi_mq_exit_request,
     .cleanup_rq = scsi_cleanup_rq,
     .busy       = scsi_mq_lld_busy,
     .map_queues = scsi_map_queues,
     .init_hctx  = scsi_init_hctx,
     .poll       = scsi_mq_poll,
     .set_rq_budget_token = scsi_mq_set_rq_budget_token,
     .get_rq_budget_token = scsi_mq_get_rq_budget_token,
 };
 
 
 static void scsi_commit_rqs(struct blk_mq_hw_ctx *hctx)
 {
     struct Scsi_Host *shost = hctx->driver_data;
 
     shost->hostt->commit_rqs(shost, hctx->queue_num);
 }
 
 static const struct blk_mq_ops scsi_mq_ops = {
     .get_budget = scsi_mq_get_budget,
     .put_budget = scsi_mq_put_budget,
     .queue_rq   = scsi_queue_rq,
     .commit_rqs = scsi_commit_rqs,
     .complete   = scsi_complete,
     .timeout    = scsi_timeout,
 #ifdef CONFIG_BLK_DEBUG_FS
     .show_rq    = scsi_show_rq,
 #endif
     .init_request   = scsi_mq_init_request,
     .exit_request   = scsi_mq_exit_request,
     .cleanup_rq = scsi_cleanup_rq,
     .busy       = scsi_mq_lld_busy,
     .map_queues = scsi_map_queues,
     .init_hctx  = scsi_init_hctx,
     .poll       = scsi_mq_poll,
     .set_rq_budget_token = scsi_mq_set_rq_budget_token,
     .get_rq_budget_token = scsi_mq_get_rq_budget_token,
 };
 
 int scsi_mq_setup_tags(struct Scsi_Host *shost)
 {
     unsigned int cmd_size, sgl_size;
     struct blk_mq_tag_set *tag_set = &shost->tag_set;
 
     sgl_size = max_t(unsigned int, sizeof(struct scatterlist),
                 scsi_mq_inline_sgl_size(shost));
     cmd_size = sizeof(struct scsi_cmnd) + shost->hostt->cmd_size + sgl_size;
     if (scsi_host_get_prot(shost))
         cmd_size += sizeof(struct scsi_data_buffer) +
             sizeof(struct scatterlist) * SCSI_INLINE_PROT_SG_CNT;
 
     memset(tag_set, 0, sizeof(*tag_set));
     if (shost->hostt->commit_rqs)
         tag_set->ops = &scsi_mq_ops;
     else
         tag_set->ops = &scsi_mq_ops_no_commit;
     tag_set->nr_hw_queues = shost->nr_hw_queues ? : 1;
     tag_set->nr_maps = shost->nr_maps ? : 1;
     tag_set->queue_depth = shost->can_queue;
     tag_set->cmd_size = cmd_size;
     tag_set->numa_node = dev_to_node(shost->dma_dev);
     tag_set->flags = BLK_MQ_F_SHOULD_MERGE;
     tag_set->flags |=
         BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
     tag_set->driver_data = shost;
     if (shost->host_tagset)
         tag_set->flags |= BLK_MQ_F_TAG_HCTX_SHARED;
 
     return blk_mq_alloc_tag_set(tag_set);
 }
 
 void scsi_mq_free_tags(struct kref *kref)
 {
     struct Scsi_Host *shost = container_of(kref, typeof(*shost),
                            tagset_refcnt);
 
     blk_mq_free_tag_set(&shost->tag_set);
     complete(&shost->tagset_freed);
 }
 
 /**
  * scsi_device_from_queue - return sdev associated with a request_queue
  * @q: The request queue to return the sdev from
  *
  * Return the sdev associated with a request queue or NULL if the
  * request_queue does not reference a SCSI device.
  */
 struct scsi_device *scsi_device_from_queue(struct request_queue *q)
 {
     struct scsi_device *sdev = NULL;
 
     if (q->mq_ops == &scsi_mq_ops_no_commit ||
         q->mq_ops == &scsi_mq_ops)
         sdev = q->queuedata;
     if (!sdev || !get_device(&sdev->sdev_gendev))
         sdev = NULL;
 
     return sdev;
 }
 /*
  * pktcdvd should have been integrated into the SCSI layers, but for historical
  * reasons like the old IDE driver it isn't.  This export allows it to safely
  * probe if a given device is a SCSI one and only attach to that.
  */
 #ifdef CONFIG_CDROM_PKTCDVD_MODULE
 EXPORT_SYMBOL_GPL(scsi_device_from_queue);
 #endif
 
 /**
  * scsi_block_requests - Utility function used by low-level drivers to prevent
  * further commands from being queued to the device.
  * @shost:  host in question
  *
  * There is no timer nor any other means by which the requests get unblocked
  * other than the low-level driver calling scsi_unblock_requests().
  */
 void scsi_block_requests(struct Scsi_Host *shost)
 {
     shost->host_self_blocked = 1;
 }
 EXPORT_SYMBOL(scsi_block_requests);
 
 /**
  * scsi_unblock_requests - Utility function used by low-level drivers to allow
  * further commands to be queued to the device.
  * @shost:  host in question
  *
  * There is no timer nor any other means by which the requests get unblocked
  * other than the low-level driver calling scsi_unblock_requests(). This is done
  * as an API function so that changes to the internals of the scsi mid-layer
  * won't require wholesale changes to drivers that use this feature.
  */
 void scsi_unblock_requests(struct Scsi_Host *shost)
 {
     shost->host_self_blocked = 0;
     scsi_run_host_queues(shost);
 }
 EXPORT_SYMBOL(scsi_unblock_requests);
 
 void scsi_exit_queue(void)
 {
     kmem_cache_destroy(scsi_sense_cache);
 }
 
 /**
  *  scsi_mode_select - issue a mode select
  *  @sdev:  SCSI device to be queried
  *  @pf:    Page format bit (1 == standard, 0 == vendor specific)
  *  @sp:    Save page bit (0 == don't save, 1 == save)
  *  @buffer: request buffer (may not be smaller than eight bytes)
  *  @len:   length of request buffer.
  *  @timeout: command timeout
  *  @retries: number of retries before failing
  *  @data: returns a structure abstracting the mode header data
  *  @sshdr: place to put sense data (or NULL if no sense to be collected).
  *      must be SCSI_SENSE_BUFFERSIZE big.
  *
  *  Returns zero if successful; negative error number or scsi
  *  status on error
  *
  */
 int scsi_mode_select(struct scsi_device *sdev, int pf, int sp,
              unsigned char *buffer, int len, int timeout, int retries,
              struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
 {
     unsigned char cmd[10];
     unsigned char *real_buffer;
     int ret;
 
     memset(cmd, 0, sizeof(cmd));
     cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
 
     /*
      * Use MODE SELECT(10) if the device asked for it or if the mode page
      * and the mode select header cannot fit within the maximumm 255 bytes
      * of the MODE SELECT(6) command.
      */
     if (sdev->use_10_for_ms ||
         len + 4 > 255 ||
         data->block_descriptor_length > 255) {
         if (len > 65535 - 8)
             return -EINVAL;
         real_buffer = kmalloc(8 + len, GFP_KERNEL);
         if (!real_buffer)
             return -ENOMEM;
         memcpy(real_buffer + 8, buffer, len);
         len += 8;
         real_buffer[0] = 0;
         real_buffer[1] = 0;
         real_buffer[2] = data->medium_type;
         real_buffer[3] = data->device_specific;
         real_buffer[4] = data->longlba ? 0x01 : 0;
         real_buffer[5] = 0;
         put_unaligned_be16(data->block_descriptor_length,
                    &real_buffer[6]);
 
         cmd[0] = MODE_SELECT_10;
         put_unaligned_be16(len, &cmd[7]);
     } else {
         if (data->longlba)
             return -EINVAL;
 
         real_buffer = kmalloc(4 + len, GFP_KERNEL);
         if (!real_buffer)
             return -ENOMEM;
         memcpy(real_buffer + 4, buffer, len);
         len += 4;
         real_buffer[0] = 0;
         real_buffer[1] = data->medium_type;
         real_buffer[2] = data->device_specific;
         real_buffer[3] = data->block_descriptor_length;
 
         cmd[0] = MODE_SELECT;
         cmd[4] = len;
     }
 
     ret = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, real_buffer, len,
                    sshdr, timeout, retries, NULL);
     kfree(real_buffer);
     return ret;
 }
 EXPORT_SYMBOL_GPL(scsi_mode_select);
 
 /**
  *  scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
  *  @sdev:  SCSI device to be queried
  *  @dbd:   set to prevent mode sense from returning block descriptors
  *  @modepage: mode page being requested
  *  @buffer: request buffer (may not be smaller than eight bytes)
  *  @len:   length of request buffer.
  *  @timeout: command timeout
  *  @retries: number of retries before failing
  *  @data: returns a structure abstracting the mode header data
  *  @sshdr: place to put sense data (or NULL if no sense to be collected).
  *      must be SCSI_SENSE_BUFFERSIZE big.
  *
  *  Returns zero if successful, or a negative error number on failure
  */
 int
 scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
           unsigned char *buffer, int len, int timeout, int retries,
           struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
 {
     unsigned char cmd[12];
     int use_10_for_ms;
     int header_length;
     int result, retry_count = retries;
     struct scsi_sense_hdr my_sshdr;
 
     memset(data, 0, sizeof(*data));
     memset(&cmd[0], 0, 12);
 
     dbd = sdev->set_dbd_for_ms ? 8 : dbd;
     cmd[1] = dbd & 0x18;    /* allows DBD and LLBA bits */
     cmd[2] = modepage;
 
     /* caller might not be interested in sense, but we need it */
     if (!sshdr)
         sshdr = &my_sshdr;
 
  retry:
     use_10_for_ms = sdev->use_10_for_ms || len > 255;
 
     if (use_10_for_ms) {
         if (len < 8 || len > 65535)
             return -EINVAL;
 
         cmd[0] = MODE_SENSE_10;
         put_unaligned_be16(len, &cmd[7]);
         header_length = 8;
     } else {
         if (len < 4)
             return -EINVAL;
 
         cmd[0] = MODE_SENSE;
         cmd[4] = len;
         header_length = 4;
     }
 
     memset(buffer, 0, len);
 
     result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
                   sshdr, timeout, retries, NULL);
     if (result < 0)
         return result;
 
     /* This code looks awful: what it's doing is making sure an
      * ILLEGAL REQUEST sense return identifies the actual command
      * byte as the problem.  MODE_SENSE commands can return
      * ILLEGAL REQUEST if the code page isn't supported */
 
     if (!scsi_status_is_good(result)) {
         if (scsi_sense_valid(sshdr)) {
             if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
                 (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
                 /*
                  * Invalid command operation code: retry using
                  * MODE SENSE(6) if this was a MODE SENSE(10)
                  * request, except if the request mode page is
                  * too large for MODE SENSE single byte
                  * allocation length field.
                  */
                 if (use_10_for_ms) {
                     if (len > 255)
                         return -EIO;
                     sdev->use_10_for_ms = 0;
                     goto retry;
                 }
             }
             if (scsi_status_is_check_condition(result) &&
                 sshdr->sense_key == UNIT_ATTENTION &&
                 retry_count) {
                 retry_count--;
                 goto retry;
             }
         }
         return -EIO;
     }
     if (unlikely(buffer[0] == 0x86 && buffer[1] == 0x0b &&
              (modepage == 6 || modepage == 8))) {
         /* Initio breakage? */
         header_length = 0;
         data->length = 13;
         data->medium_type = 0;
         data->device_specific = 0;
         data->longlba = 0;
         data->block_descriptor_length = 0;
     } else if (use_10_for_ms) {
         data->length = get_unaligned_be16(&buffer[0]) + 2;
         data->medium_type = buffer[2];
         data->device_specific = buffer[3];
         data->longlba = buffer[4] & 0x01;
         data->block_descriptor_length = get_unaligned_be16(&buffer[6]);
     } else {
         data->length = buffer[0] + 1;
         data->medium_type = buffer[1];
         data->device_specific = buffer[2];
         data->block_descriptor_length = buffer[3];
     }
     data->header_length = header_length;
 
     return 0;
 }
 EXPORT_SYMBOL(scsi_mode_sense);
 
 /**
  *  scsi_test_unit_ready - test if unit is ready
  *  @sdev:  scsi device to change the state of.
  *  @timeout: command timeout
  *  @retries: number of retries before failing
  *  @sshdr: outpout pointer for decoded sense information.
  *
  *  Returns zero if unsuccessful or an error if TUR failed.  For
  *  removable media, UNIT_ATTENTION sets ->changed flag.
  **/
 int
 scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries,
              struct scsi_sense_hdr *sshdr)
 {
     char cmd[] = {
         TEST_UNIT_READY, 0, 0, 0, 0, 0,
     };
     int result;
 
     /* try to eat the UNIT_ATTENTION if there are enough retries */
     do {
         result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
                       timeout, 1, NULL);
         if (sdev->removable && scsi_sense_valid(sshdr) &&
             sshdr->sense_key == UNIT_ATTENTION)
             sdev->changed = 1;
     } while (scsi_sense_valid(sshdr) &&
          sshdr->sense_key == UNIT_ATTENTION && --retries);
 
     return result;
 }
 EXPORT_SYMBOL(scsi_test_unit_ready);
 
 /**
  *  scsi_device_set_state - Take the given device through the device state model.
  *  @sdev:  scsi device to change the state of.
  *  @state: state to change to.
  *
  *  Returns zero if successful or an error if the requested
  *  transition is illegal.
  */
 int
 scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
 {
     enum scsi_device_state oldstate = sdev->sdev_state;
 
     if (state == oldstate)
         return 0;
 
     switch (state) {
     case SDEV_CREATED:
         switch (oldstate) {
         case SDEV_CREATED_BLOCK:
             break;
         default:
             goto illegal;
         }
         break;
 
     case SDEV_RUNNING:
         switch (oldstate) {
         case SDEV_CREATED:
         case SDEV_OFFLINE:
         case SDEV_TRANSPORT_OFFLINE:
         case SDEV_QUIESCE:
         case SDEV_BLOCK:
             break;
         default:
             goto illegal;
         }
         break;
 
     case SDEV_QUIESCE:
         switch (oldstate) {
         case SDEV_RUNNING:
         case SDEV_OFFLINE:
         case SDEV_TRANSPORT_OFFLINE:
             break;
         default:
             goto illegal;
         }
         break;
 
     case SDEV_OFFLINE:
     case SDEV_TRANSPORT_OFFLINE:
         switch (oldstate) {
         case SDEV_CREATED:
         case SDEV_RUNNING:
         case SDEV_QUIESCE:
         case SDEV_BLOCK:
             break;
         default:
             goto illegal;
         }
         break;
 
     case SDEV_BLOCK:
         switch (oldstate) {
         case SDEV_RUNNING:
         case SDEV_CREATED_BLOCK:
         case SDEV_QUIESCE:
         case SDEV_OFFLINE:
             break;
         default:
             goto illegal;
         }
         break;
 
     case SDEV_CREATED_BLOCK:
         switch (oldstate) {
         case SDEV_CREATED:
             break;
         default:
             goto illegal;
         }
         break;
 
     case SDEV_CANCEL:
         switch (oldstate) {
         case SDEV_CREATED:
         case SDEV_RUNNING:
         case SDEV_QUIESCE:
         case SDEV_OFFLINE:
         case SDEV_TRANSPORT_OFFLINE:
             break;
         default:
             goto illegal;
         }
         break;
 
     case SDEV_DEL:
         switch (oldstate) {
         case SDEV_CREATED:
         case SDEV_RUNNING:
         case SDEV_OFFLINE:
         case SDEV_TRANSPORT_OFFLINE:
         case SDEV_CANCEL:
         case SDEV_BLOCK:
         case SDEV_CREATED_BLOCK:
             break;
         default:
             goto illegal;
         }
         break;
 
     }
     sdev->offline_already = false;
     sdev->sdev_state = state;
     return 0;
 
  illegal:
     SCSI_LOG_ERROR_RECOVERY(1,
                 sdev_printk(KERN_ERR, sdev,
                         "Illegal state transition %s->%s",
                         scsi_device_state_name(oldstate),
                         scsi_device_state_name(state))
                 );
     return -EINVAL;
 }
 EXPORT_SYMBOL(scsi_device_set_state);
 
 /**
  *  scsi_evt_emit - emit a single SCSI device uevent
  *  @sdev: associated SCSI device
  *  @evt: event to emit
  *
  *  Send a single uevent (scsi_event) to the associated scsi_device.
  */
 static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
 {
     int idx = 0;
     char *envp[3];
 
     switch (evt->evt_type) {
     case SDEV_EVT_MEDIA_CHANGE:
         envp[idx++] = "SDEV_MEDIA_CHANGE=1";
         break;
     case SDEV_EVT_INQUIRY_CHANGE_REPORTED:
         scsi_rescan_device(&sdev->sdev_gendev);
         envp[idx++] = "SDEV_UA=INQUIRY_DATA_HAS_CHANGED";
         break;
     case SDEV_EVT_CAPACITY_CHANGE_REPORTED:
         envp[idx++] = "SDEV_UA=CAPACITY_DATA_HAS_CHANGED";
         break;
     case SDEV_EVT_SOFT_THRESHOLD_REACHED_REPORTED:
            envp[idx++] = "SDEV_UA=THIN_PROVISIONING_SOFT_THRESHOLD_REACHED";
         break;
     case SDEV_EVT_MODE_PARAMETER_CHANGE_REPORTED:
         envp[idx++] = "SDEV_UA=MODE_PARAMETERS_CHANGED";
         break;
     case SDEV_EVT_LUN_CHANGE_REPORTED:
         envp[idx++] = "SDEV_UA=REPORTED_LUNS_DATA_HAS_CHANGED";
         break;
     case SDEV_EVT_ALUA_STATE_CHANGE_REPORTED:
         envp[idx++] = "SDEV_UA=ASYMMETRIC_ACCESS_STATE_CHANGED";
         break;
     case SDEV_EVT_POWER_ON_RESET_OCCURRED:
         envp[idx++] = "SDEV_UA=POWER_ON_RESET_OCCURRED";
         break;
     default:
         /* do nothing */
         break;
     }
 
     envp[idx++] = NULL;
 
     kobject_uevent_env(&sdev->sdev_gendev.kobj, KOBJ_CHANGE, envp);
 }
 
 /**
  *  scsi_evt_thread - send a uevent for each scsi event
  *  @work: work struct for scsi_device
  *
  *  Dispatch queued events to their associated scsi_device kobjects
  *  as uevents.
  */
 void scsi_evt_thread(struct work_struct *work)
 {
     struct scsi_device *sdev;
     enum scsi_device_event evt_type;
     LIST_HEAD(event_list);
 
     sdev = container_of(work, struct scsi_device, event_work);
 
     for (evt_type = SDEV_EVT_FIRST; evt_type <= SDEV_EVT_LAST; evt_type++)
         if (test_and_clear_bit(evt_type, sdev->pending_events))
             sdev_evt_send_simple(sdev, evt_type, GFP_KERNEL);
 
     while (1) {
         struct scsi_event *evt;
         struct list_head *this, *tmp;
         unsigned long flags;
 
         spin_lock_irqsave(&sdev->list_lock, flags);
         list_splice_init(&sdev->event_list, &event_list);
         spin_unlock_irqrestore(&sdev->list_lock, flags);
 
         if (list_empty(&event_list))
             break;
 
         list_for_each_safe(this, tmp, &event_list) {
             evt = list_entry(this, struct scsi_event, node);
             list_del(&evt->node);
             scsi_evt_emit(sdev, evt);
             kfree(evt);
         }
     }
 }
 
 /**
  *  sdev_evt_send - send asserted event to uevent thread
  *  @sdev: scsi_device event occurred on
  *  @evt: event to send
  *
  *  Assert scsi device event asynchronously.
  */
 void sdev_evt_send(struct scsi_device *sdev, struct scsi_event *evt)
 {
     unsigned long flags;
 
 #if 0
     /* FIXME: currently this check eliminates all media change events
      * for polled devices.  Need to update to discriminate between AN
      * and polled events */
     if (!test_bit(evt->evt_type, sdev->supported_events)) {
         kfree(evt);
         return;
     }
 #endif
 
     spin_lock_irqsave(&sdev->list_lock, flags);
     list_add_tail(&evt->node, &sdev->event_list);
     schedule_work(&sdev->event_work);
     spin_unlock_irqrestore(&sdev->list_lock, flags);
 }
 EXPORT_SYMBOL_GPL(sdev_evt_send);
 
 /**
  *  sdev_evt_alloc - allocate a new scsi event
  *  @evt_type: type of event to allocate
  *  @gfpflags: GFP flags for allocation
  *
  *  Allocates and returns a new scsi_event.
  */
 struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
                   gfp_t gfpflags)
 {
     struct scsi_event *evt = kzalloc(sizeof(struct scsi_event), gfpflags);
     if (!evt)
         return NULL;
 
     evt->evt_type = evt_type;
     INIT_LIST_HEAD(&evt->node);
 
     /* evt_type-specific initialization, if any */
     switch (evt_type) {
     case SDEV_EVT_MEDIA_CHANGE:
     case SDEV_EVT_INQUIRY_CHANGE_REPORTED:
     case SDEV_EVT_CAPACITY_CHANGE_REPORTED:
     case SDEV_EVT_SOFT_THRESHOLD_REACHED_REPORTED:
     case SDEV_EVT_MODE_PARAMETER_CHANGE_REPORTED:
     case SDEV_EVT_LUN_CHANGE_REPORTED:
     case SDEV_EVT_ALUA_STATE_CHANGE_REPORTED:
     case SDEV_EVT_POWER_ON_RESET_OCCURRED:
     default:
         /* do nothing */
         break;
     }
 
     return evt;
 }
 EXPORT_SYMBOL_GPL(sdev_evt_alloc);
 
 /**
  *  sdev_evt_send_simple - send asserted event to uevent thread
  *  @sdev: scsi_device event occurred on
  *  @evt_type: type of event to send
  *  @gfpflags: GFP flags for allocation
  *
  *  Assert scsi device event asynchronously, given an event type.
  */
 void sdev_evt_send_simple(struct scsi_device *sdev,
               enum scsi_device_event evt_type, gfp_t gfpflags)
 {
     struct scsi_event *evt = sdev_evt_alloc(evt_type, gfpflags);
     if (!evt) {
         sdev_printk(KERN_ERR, sdev, "event %d eaten due to OOM\n",
                 evt_type);
         return;
     }
 
     sdev_evt_send(sdev, evt);
 }
 EXPORT_SYMBOL_GPL(sdev_evt_send_simple);
 
 /**
  *  scsi_device_quiesce - Block all commands except power management.
  *  @sdev:  scsi device to quiesce.
  *
  *  This works by trying to transition to the SDEV_QUIESCE state
  *  (which must be a legal transition).  When the device is in this
  *  state, only power management requests will be accepted, all others will
  *  be deferred.
  *
  *  Must be called with user context, may sleep.
  *
  *  Returns zero if unsuccessful or an error if not.
  */
 int
 scsi_device_quiesce(struct scsi_device *sdev)
 {
     struct request_queue *q = sdev->request_queue;
     int err;
 
     /*
      * It is allowed to call scsi_device_quiesce() multiple times from
      * the same context but concurrent scsi_device_quiesce() calls are
      * not allowed.
      */
     WARN_ON_ONCE(sdev->quiesced_by && sdev->quiesced_by != current);
 
     if (sdev->quiesced_by == current)
         return 0;
 
     blk_set_pm_only(q);
 
     blk_mq_freeze_queue(q);
     /*
      * Ensure that the effect of blk_set_pm_only() will be visible
      * for percpu_ref_tryget() callers that occur after the queue
      * unfreeze even if the queue was already frozen before this function
      * was called. See also https://lwn.net/Articles/573497/.
      */
     synchronize_rcu();
     blk_mq_unfreeze_queue(q);
 
     mutex_lock(&sdev->state_mutex);
     err = scsi_device_set_state(sdev, SDEV_QUIESCE);
     if (err == 0)
         sdev->quiesced_by = current;
     else
         blk_clear_pm_only(q);
     mutex_unlock(&sdev->state_mutex);
 
     return err;
 }
 EXPORT_SYMBOL(scsi_device_quiesce);
 
 /**
  *  scsi_device_resume - Restart user issued commands to a quiesced device.
  *  @sdev:  scsi device to resume.
  *
  *  Moves the device from quiesced back to running and restarts the
  *  queues.
  *
  *  Must be called with user context, may sleep.
  */
 void scsi_device_resume(struct scsi_device *sdev)
 {
     /* check if the device state was mutated prior to resume, and if
      * so assume the state is being managed elsewhere (for example
      * device deleted during suspend)
      */
     mutex_lock(&sdev->state_mutex);
     if (sdev->sdev_state == SDEV_QUIESCE)
         scsi_device_set_state(sdev, SDEV_RUNNING);
     if (sdev->quiesced_by) {
         sdev->quiesced_by = NULL;
         blk_clear_pm_only(sdev->request_queue);
     }
     mutex_unlock(&sdev->state_mutex);
 }
 EXPORT_SYMBOL(scsi_device_resume);
 
 static void
 device_quiesce_fn(struct scsi_device *sdev, void *data)
 {
     scsi_device_quiesce(sdev);
 }
 
 void
 scsi_target_quiesce(struct scsi_target *starget)
 {
     starget_for_each_device(starget, NULL, device_quiesce_fn);
 }
 EXPORT_SYMBOL(scsi_target_quiesce);
 
 static void
 device_resume_fn(struct scsi_device *sdev, void *data)
 {
     scsi_device_resume(sdev);
 }
 
 void
 scsi_target_resume(struct scsi_target *starget)
 {
     starget_for_each_device(starget, NULL, device_resume_fn);
 }
 EXPORT_SYMBOL(scsi_target_resume);
 
 static int __scsi_internal_device_block_nowait(struct scsi_device *sdev)
 {
     if (scsi_device_set_state(sdev, SDEV_BLOCK))
         return scsi_device_set_state(sdev, SDEV_CREATED_BLOCK);
 
     return 0;
 }
 
 void scsi_start_queue(struct scsi_device *sdev)
 {
     if (cmpxchg(&sdev->queue_stopped, 1, 0))
         blk_mq_unquiesce_queue(sdev->request_queue);
 }
 
 static void scsi_stop_queue(struct scsi_device *sdev, bool nowait)
 {
     /*
      * The atomic variable of ->queue_stopped covers that
      * blk_mq_quiesce_queue* is balanced with blk_mq_unquiesce_queue.
      *
      * However, we still need to wait until quiesce is done
      * in case that queue has been stopped.
      */
     if (!cmpxchg(&sdev->queue_stopped, 0, 1)) {
         if (nowait)
             blk_mq_quiesce_queue_nowait(sdev->request_queue);
         else
             blk_mq_quiesce_queue(sdev->request_queue);
     } else {
         if (!nowait)
             blk_mq_wait_quiesce_done(sdev->request_queue);
     }
 }
 
 /**
  * scsi_internal_device_block_nowait - try to transition to the SDEV_BLOCK state
  * @sdev: device to block
  *
  * Pause SCSI command processing on the specified device. Does not sleep.
  *
  * Returns zero if successful or a negative error code upon failure.
  *
  * Notes:
  * This routine transitions the device to the SDEV_BLOCK state (which must be
  * a legal transition). When the device is in this state, command processing
  * is paused until the device leaves the SDEV_BLOCK state. See also
  * scsi_internal_device_unblock_nowait().
  */
 int scsi_internal_device_block_nowait(struct scsi_device *sdev)
 {
     int ret = __scsi_internal_device_block_nowait(sdev);
 
     /*
      * The device has transitioned to SDEV_BLOCK.  Stop the
      * block layer from calling the midlayer with this device's
      * request queue.
      */
     if (!ret)
         scsi_stop_queue(sdev, true);
     return ret;
 }
 EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
 
 /**
  * scsi_internal_device_block - try to transition to the SDEV_BLOCK state
  * @sdev: device to block
  *
  * Pause SCSI command processing on the specified device and wait until all
  * ongoing scsi_request_fn() / scsi_queue_rq() calls have finished. May sleep.
  *
  * Returns zero if successful or a negative error code upon failure.
  *
  * Note:
  * This routine transitions the device to the SDEV_BLOCK state (which must be
  * a legal transition). When the device is in this state, command processing
  * is paused until the device leaves the SDEV_BLOCK state. See also
  * scsi_internal_device_unblock().
  */
 static int scsi_internal_device_block(struct scsi_device *sdev)
 {
     int err;
 
     mutex_lock(&sdev->state_mutex);
     err = __scsi_internal_device_block_nowait(sdev);
     if (err == 0)
         scsi_stop_queue(sdev, false);
     mutex_unlock(&sdev->state_mutex);
 
     return err;
 }
 
 /**
  * scsi_internal_device_unblock_nowait - resume a device after a block request
  * @sdev:   device to resume
  * @new_state:  state to set the device to after unblocking
  *
  * Restart the device queue for a previously suspended SCSI device. Does not
  * sleep.
  *
  * Returns zero if successful or a negative error code upon failure.
  *
  * Notes:
  * This routine transitions the device to the SDEV_RUNNING state or to one of
  * the offline states (which must be a legal transition) allowing the midlayer
  * to goose the queue for this device.
  */
 int scsi_internal_device_unblock_nowait(struct scsi_device *sdev,
                     enum scsi_device_state new_state)
 {
     switch (new_state) {
     case SDEV_RUNNING:
     case SDEV_TRANSPORT_OFFLINE:
         break;
     default:
         return -EINVAL;
     }
 
     /*
      * Try to transition the scsi device to SDEV_RUNNING or one of the
      * offlined states and goose the device queue if successful.
      */
     switch (sdev->sdev_state) {
     case SDEV_BLOCK:
     case SDEV_TRANSPORT_OFFLINE:
         sdev->sdev_state = new_state;
         break;
     case SDEV_CREATED_BLOCK:
         if (new_state == SDEV_TRANSPORT_OFFLINE ||
             new_state == SDEV_OFFLINE)
             sdev->sdev_state = new_state;
         else
             sdev->sdev_state = SDEV_CREATED;
         break;
     case SDEV_CANCEL:
     case SDEV_OFFLINE:
         break;
     default:
         return -EINVAL;
     }
     scsi_start_queue(sdev);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(scsi_internal_device_unblock_nowait);
 
 /**
  * scsi_internal_device_unblock - resume a device after a block request
  * @sdev:   device to resume
  * @new_state:  state to set the device to after unblocking
  *
  * Restart the device queue for a previously suspended SCSI device. May sleep.
  *
  * Returns zero if successful or a negative error code upon failure.
  *
  * Notes:
  * This routine transitions the device to the SDEV_RUNNING state or to one of
  * the offline states (which must be a legal transition) allowing the midlayer
  * to goose the queue for this device.
  */
 static int scsi_internal_device_unblock(struct scsi_device *sdev,
                     enum scsi_device_state new_state)
 {
     int ret;
 
     mutex_lock(&sdev->state_mutex);
     ret = scsi_internal_device_unblock_nowait(sdev, new_state);
     mutex_unlock(&sdev->state_mutex);
 
     return ret;
 }
 
 static void
 device_block(struct scsi_device *sdev, void *data)
 {
     int ret;
 
     ret = scsi_internal_device_block(sdev);
 
     WARN_ONCE(ret, "scsi_internal_device_block(%s) failed: ret = %d\n",
           dev_name(&sdev->sdev_gendev), ret);
 }
 
 static int
 target_block(struct device *dev, void *data)
 {
     if (scsi_is_target_device(dev))
         starget_for_each_device(to_scsi_target(dev), NULL,
                     device_block);
     return 0;
 }
 
 void
 scsi_target_block(struct device *dev)
 {
     if (scsi_is_target_device(dev))
         starget_for_each_device(to_scsi_target(dev), NULL,
                     device_block);
     else
         device_for_each_child(dev, NULL, target_block);
 }
 EXPORT_SYMBOL_GPL(scsi_target_block);
 
 static void
 device_unblock(struct scsi_device *sdev, void *data)
 {
     scsi_internal_device_unblock(sdev, *(enum scsi_device_state *)data);
 }
 
 static int
 target_unblock(struct device *dev, void *data)
 {
     if (scsi_is_target_device(dev))
         starget_for_each_device(to_scsi_target(dev), data,
                     device_unblock);
     return 0;
 }
 
 void
 scsi_target_unblock(struct device *dev, enum scsi_device_state new_state)
 {
     if (scsi_is_target_device(dev))
         starget_for_each_device(to_scsi_target(dev), &new_state,
                     device_unblock);
     else
         device_for_each_child(dev, &new_state, target_unblock);
 }
 EXPORT_SYMBOL_GPL(scsi_target_unblock);
 
 int
 scsi_host_block(struct Scsi_Host *shost)
 {
     struct scsi_device *sdev;
     int ret = 0;
 
     /*
      * Call scsi_internal_device_block_nowait so we can avoid
      * calling synchronize_rcu() for each LUN.
      */
     shost_for_each_device(sdev, shost) {
         mutex_lock(&sdev->state_mutex);
         ret = scsi_internal_device_block_nowait(sdev);
         mutex_unlock(&sdev->state_mutex);
         if (ret) {
             scsi_device_put(sdev);
             break;
         }
     }
 
     /*
      * SCSI never enables blk-mq's BLK_MQ_F_BLOCKING flag so
      * calling synchronize_rcu() once is enough.
      */
     WARN_ON_ONCE(shost->tag_set.flags & BLK_MQ_F_BLOCKING);
 
     if (!ret)
         synchronize_rcu();
 
     return ret;
 }
 EXPORT_SYMBOL_GPL(scsi_host_block);
 
 int
 scsi_host_unblock(struct Scsi_Host *shost, int new_state)
 {
     struct scsi_device *sdev;
     int ret = 0;
 
     shost_for_each_device(sdev, shost) {
         ret = scsi_internal_device_unblock(sdev, new_state);
         if (ret) {
             scsi_device_put(sdev);
             break;
         }
     }
     return ret;
 }
 EXPORT_SYMBOL_GPL(scsi_host_unblock);
 
 /**
  * scsi_kmap_atomic_sg - find and atomically map an sg-elemnt
  * @sgl:    scatter-gather list
  * @sg_count:   number of segments in sg
  * @offset: offset in bytes into sg, on return offset into the mapped area
  * @len:    bytes to map, on return number of bytes mapped
  *
  * Returns virtual address of the start of the mapped page
  */
 void *scsi_kmap_atomic_sg(struct scatterlist *sgl, int sg_count,
               size_t *offset, size_t *len)
 {
     int i;
     size_t sg_len = 0, len_complete = 0;
     struct scatterlist *sg;
     struct page *page;
 
     WARN_ON(!irqs_disabled());
 
     for_each_sg(sgl, sg, sg_count, i) {
         len_complete = sg_len; /* Complete sg-entries */
         sg_len += sg->length;
         if (sg_len > *offset)
             break;
     }
 
     if (unlikely(i == sg_count)) {
         printk(KERN_ERR "%s: Bytes in sg: %zu, requested offset %zu, "
             "elements %d\n",
                __func__, sg_len, *offset, sg_count);
         WARN_ON(1);
         return NULL;
     }
 
     /* Offset starting from the beginning of first page in this sg-entry */
     *offset = *offset - len_complete + sg->offset;
 
     /* Assumption: contiguous pages can be accessed as "page + i" */
     page = nth_page(sg_page(sg), (*offset >> PAGE_SHIFT));
     *offset &= ~PAGE_MASK;
 
     /* Bytes in this sg-entry from *offset to the end of the page */
     sg_len = PAGE_SIZE - *offset;
     if (*len > sg_len)
         *len = sg_len;
 
     return kmap_atomic(page);
 }
 EXPORT_SYMBOL(scsi_kmap_atomic_sg);
 
 /**
  * scsi_kunmap_atomic_sg - atomically unmap a virtual address, previously mapped with scsi_kmap_atomic_sg
  * @virt:   virtual address to be unmapped
  */
 void scsi_kunmap_atomic_sg(void *virt)
 {
     kunmap_atomic(virt);
 }
 EXPORT_SYMBOL(scsi_kunmap_atomic_sg);
 
 void sdev_disable_disk_events(struct scsi_device *sdev)
 {
     atomic_inc(&sdev->disk_events_disable_depth);
 }
 EXPORT_SYMBOL(sdev_disable_disk_events);
 
 void sdev_enable_disk_events(struct scsi_device *sdev)
 {
     if (WARN_ON_ONCE(atomic_read(&sdev->disk_events_disable_depth) <= 0))
         return;
     atomic_dec(&sdev->disk_events_disable_depth);
 }
 EXPORT_SYMBOL(sdev_enable_disk_events);
 
 static unsigned char designator_prio(const unsigned char *d)
 {
     if (d[1] & 0x30)
         /* not associated with LUN */
         return 0;
 
     if (d[3] == 0)
         /* invalid length */
         return 0;
 
     /*
      * Order of preference for lun descriptor:
      * - SCSI name string
      * - NAA IEEE Registered Extended
      * - EUI-64 based 16-byte
      * - EUI-64 based 12-byte
      * - NAA IEEE Registered
      * - NAA IEEE Extended
      * - EUI-64 based 8-byte
      * - SCSI name string (truncated)
      * - T10 Vendor ID
      * as longer descriptors reduce the likelyhood
      * of identification clashes.
      */
 
     switch (d[1] & 0xf) {
     case 8:
         /* SCSI name string, variable-length UTF-8 */
         return 9;
     case 3:
         switch (d[4] >> 4) {
         case 6:
             /* NAA registered extended */
             return 8;
         case 5:
             /* NAA registered */
             return 5;
         case 4:
             /* NAA extended */
             return 4;
         case 3:
             /* NAA locally assigned */
             return 1;
         default:
             break;
         }
         break;
     case 2:
         switch (d[3]) {
         case 16:
             /* EUI64-based, 16 byte */
             return 7;
         case 12:
             /* EUI64-based, 12 byte */
             return 6;
         case 8:
             /* EUI64-based, 8 byte */
             return 3;
         default:
             break;
         }
         break;
     case 1:
         /* T10 vendor ID */
         return 1;
     default:
         break;
     }
 
     return 0;
 }
 
 /**
  * scsi_vpd_lun_id - return a unique device identification
  * @sdev: SCSI device
  * @id:   buffer for the identification
  * @id_len:  length of the buffer
  *
  * Copies a unique device identification into @id based
  * on the information in the VPD page 0x83 of the device.
  * The string will be formatted as a SCSI name string.
  *
  * Returns the length of the identification or error on failure.
  * If the identifier is longer than the supplied buffer the actual
  * identifier length is returned and the buffer is not zero-padded.
  */
 int scsi_vpd_lun_id(struct scsi_device *sdev, char *id, size_t id_len)
 {
     u8 cur_id_prio = 0;
     u8 cur_id_size = 0;
     const unsigned char *d, *cur_id_str;
     const struct scsi_vpd *vpd_pg83;
     int id_size = -EINVAL;
 
     rcu_read_lock();
     vpd_pg83 = rcu_dereference(sdev->vpd_pg83);
     if (!vpd_pg83) {
         rcu_read_unlock();
         return -ENXIO;
     }
 
     /* The id string must be at least 20 bytes + terminating NULL byte */
     if (id_len < 21) {
         rcu_read_unlock();
         return -EINVAL;
     }
 
     memset(id, 0, id_len);
     for (d = vpd_pg83->data + 4;
          d < vpd_pg83->data + vpd_pg83->len;
          d += d[3] + 4) {
         u8 prio = designator_prio(d);
 
         if (prio == 0 || cur_id_prio > prio)
             continue;
 
         switch (d[1] & 0xf) {
         case 0x1:
             /* T10 Vendor ID */
             if (cur_id_size > d[3])
                 break;
             cur_id_prio = prio;
             cur_id_size = d[3];
             if (cur_id_size + 4 > id_len)
                 cur_id_size = id_len - 4;
             cur_id_str = d + 4;
             id_size = snprintf(id, id_len, "t10.%*pE",
                        cur_id_size, cur_id_str);
             break;
         case 0x2:
             /* EUI-64 */
             cur_id_prio = prio;
             cur_id_size = d[3];
             cur_id_str = d + 4;
             switch (cur_id_size) {
             case 8:
                 id_size = snprintf(id, id_len,
                            "eui.%8phN",
                            cur_id_str);
                 break;
             case 12:
                 id_size = snprintf(id, id_len,
                            "eui.%12phN",
                            cur_id_str);
                 break;
             case 16:
                 id_size = snprintf(id, id_len,
                            "eui.%16phN",
                            cur_id_str);
                 break;
             default:
                 break;
             }
             break;
         case 0x3:
             /* NAA */
             cur_id_prio = prio;
             cur_id_size = d[3];
             cur_id_str = d + 4;
             switch (cur_id_size) {
             case 8:
                 id_size = snprintf(id, id_len,
                            "naa.%8phN",
                            cur_id_str);
                 break;
             case 16:
                 id_size = snprintf(id, id_len,
                            "naa.%16phN",
                            cur_id_str);
                 break;
             default:
                 break;
             }
             break;
         case 0x8:
             /* SCSI name string */
             if (cur_id_size > d[3])
                 break;
             /* Prefer others for truncated descriptor */
             if (d[3] > id_len) {
                 prio = 2;
                 if (cur_id_prio > prio)
                     break;
             }
             cur_id_prio = prio;
             cur_id_size = id_size = d[3];
             cur_id_str = d + 4;
             if (cur_id_size >= id_len)
                 cur_id_size = id_len - 1;
             memcpy(id, cur_id_str, cur_id_size);
             break;
         default:
             break;
         }
     }
     rcu_read_unlock();
 
     return id_size;
 }
 EXPORT_SYMBOL(scsi_vpd_lun_id);
 
 /*
  * scsi_vpd_tpg_id - return a target port group identifier
  * @sdev: SCSI device
  *
  * Returns the Target Port Group identifier from the information
  * froom VPD page 0x83 of the device.
  *
  * Returns the identifier or error on failure.
  */
 int scsi_vpd_tpg_id(struct scsi_device *sdev, int *rel_id)
 {
     const unsigned char *d;
     const struct scsi_vpd *vpd_pg83;
     int group_id = -EAGAIN, rel_port = -1;
 
     rcu_read_lock();
     vpd_pg83 = rcu_dereference(sdev->vpd_pg83);
     if (!vpd_pg83) {
         rcu_read_unlock();
         return -ENXIO;
     }
 
     d = vpd_pg83->data + 4;
     while (d < vpd_pg83->data + vpd_pg83->len) {
         switch (d[1] & 0xf) {
         case 0x4:
             /* Relative target port */
             rel_port = get_unaligned_be16(&d[6]);
             break;
         case 0x5:
             /* Target port group */
             group_id = get_unaligned_be16(&d[6]);
             break;
         default:
             break;
         }
         d += d[3] + 4;
     }
     rcu_read_unlock();
 
     if (group_id >= 0 && rel_id && rel_port != -1)
         *rel_id = rel_port;
 
     return group_id;
 }
 EXPORT_SYMBOL(scsi_vpd_tpg_id);
 
 /**
  * scsi_build_sense - build sense data for a command
  * @scmd:   scsi command for which the sense should be formatted
  * @desc:   Sense format (non-zero == descriptor format,
  *              0 == fixed format)
  * @key:    Sense key
  * @asc:    Additional sense code
  * @ascq:   Additional sense code qualifier
  *
  **/
 void scsi_build_sense(struct scsi_cmnd *scmd, int desc, u8 key, u8 asc, u8 ascq)
 {
     scsi_build_sense_buffer(desc, scmd->sense_buffer, key, asc, ascq);
     scmd->result = SAM_STAT_CHECK_CONDITION;
 }
 EXPORT_SYMBOL_GPL(scsi_build_sense);