Initial import

1 files changed, 3147 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
new file mode 100644
index 000000000..b1a263137
--- /dev/null
+++ b/drivers/scsi/scsi_lib.c
@@ -0,0 +1,3147 @@
+/*
+ * 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/mempool.h>
+#include <linux/slab.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/ratelimit.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 <trace/events/scsi.h>
+
+#include "scsi_priv.h"
+#include "scsi_logging.h"
+
+
+#define SG_MEMPOOL_NR		ARRAY_SIZE(scsi_sg_pools)
+#define SG_MEMPOOL_SIZE		2
+
+struct scsi_host_sg_pool {
+	size_t		size;
+	char		*name;
+	struct kmem_cache	*slab;
+	mempool_t	*pool;
+};
+
+#define SP(x) { .size = x, "sgpool-" __stringify(x) }
+#if (SCSI_MAX_SG_SEGMENTS < 32)
+#error SCSI_MAX_SG_SEGMENTS is too small (must be 32 or greater)
+#endif
+static struct scsi_host_sg_pool scsi_sg_pools[] = {
+	SP(8),
+	SP(16),
+#if (SCSI_MAX_SG_SEGMENTS > 32)
+	SP(32),
+#if (SCSI_MAX_SG_SEGMENTS > 64)
+	SP(64),
+#if (SCSI_MAX_SG_SEGMENTS > 128)
+	SP(128),
+#if (SCSI_MAX_SG_SEGMENTS > 256)
+#error SCSI_MAX_SG_SEGMENTS is too large (256 MAX)
+#endif
+#endif
+#endif
+#endif
+	SP(SCSI_MAX_SG_SEGMENTS)
+};
+#undef SP
+
+struct kmem_cache *scsi_sdb_cache;
+
+/*
+ * 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 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)
+{
+	struct scsi_device *sdev = cmd->device;
+	struct request_queue *q = cmd->request->q;
+
+	blk_mq_requeue_request(cmd->request);
+	blk_mq_kick_requeue_list(q);
+	put_device(&sdev->sdev_gendev);
+}
+
+/**
+ * __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, int unbusy)
+{
+	struct scsi_device *device = cmd->device;
+	struct request_queue *q = device->request_queue;
+	unsigned long flags;
+
+	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);
+
+	/*
+	 * 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_cleanup_queue() finishes.
+	 */
+	cmd->result = 0;
+	if (q->mq_ops) {
+		scsi_mq_requeue_cmd(cmd);
+		return;
+	}
+	spin_lock_irqsave(q->queue_lock, flags);
+	blk_requeue_request(q, cmd->request);
+	kblockd_schedule_work(&device->requeue_work);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+/*
+ * Function:    scsi_queue_insert()
+ *
+ * Purpose:     Insert a command in the midlevel queue.
+ *
+ * Arguments:   cmd    - command that we are adding to queue.
+ *              reason - why we are inserting command to queue.
+ *
+ * Lock status: Assumed that lock is not held upon entry.
+ *
+ * Returns:     Nothing.
+ *
+ * Notes:       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.
+ * Notes:       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, 1);
+}
+/**
+ * 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
+ * @timeout:	request timeout in seconds
+ * @retries:	number of times to retry request
+ * @flags:	or into request flags;
+ * @resid:	optional residual length
+ *
+ * returns the req->errors value which is the scsi_cmnd result
+ * field.
+ */
+int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
+		 int data_direction, void *buffer, unsigned bufflen,
+		 unsigned char *sense, int timeout, int retries, u64 flags,
+		 int *resid)
+{
+	struct request *req;
+	int write = (data_direction == DMA_TO_DEVICE);
+	int ret = DRIVER_ERROR << 24;
+
+	req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
+	if (IS_ERR(req))
+		return ret;
+	blk_rq_set_block_pc(req);
+
+	if (bufflen &&	blk_rq_map_kern(sdev->request_queue, req,
+					buffer, bufflen, __GFP_WAIT))
+		goto out;
+
+	req->cmd_len = COMMAND_SIZE(cmd[0]);
+	memcpy(req->cmd, cmd, req->cmd_len);
+	req->sense = sense;
+	req->sense_len = 0;
+	req->retries = retries;
+	req->timeout = timeout;
+	req->cmd_flags |= flags | REQ_QUIET | REQ_PREEMPT;
+
+	/*
+	 * head injection *required* here otherwise quiesce won't work
+	 */
+	blk_execute_rq(req->q, NULL, req, 1);
+
+	/*
+	 * 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(req->resid_len > 0 && req->resid_len <= bufflen))
+		memset(buffer + (bufflen - req->resid_len), 0, req->resid_len);
+
+	if (resid)
+		*resid = req->resid_len;
+	ret = req->errors;
+ out:
+	blk_put_request(req);
+
+	return ret;
+}
+EXPORT_SYMBOL(scsi_execute);
+
+int scsi_execute_req_flags(struct scsi_device *sdev, const unsigned char *cmd,
+		     int data_direction, void *buffer, unsigned bufflen,
+		     struct scsi_sense_hdr *sshdr, int timeout, int retries,
+		     int *resid, u64 flags)
+{
+	char *sense = NULL;
+	int result;
+	
+	if (sshdr) {
+		sense = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
+		if (!sense)
+			return DRIVER_ERROR << 24;
+	}
+	result = scsi_execute(sdev, cmd, data_direction, buffer, bufflen,
+			      sense, timeout, retries, flags, resid);
+	if (sshdr)
+		scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, sshdr);
+
+	kfree(sense);
+	return result;
+}
+EXPORT_SYMBOL(scsi_execute_req_flags);
+
+/*
+ * Function:    scsi_init_cmd_errh()
+ *
+ * Purpose:     Initialize cmd fields related to error handling.
+ *
+ * Arguments:   cmd	- command that is ready to be queued.
+ *
+ * Notes:       This function has the job of initializing a number of
+ *              fields related to error handling.   Typically this will
+ *              be called once for each command, as required.
+ */
+static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
+{
+	cmd->serial_number = 0;
+	scsi_set_resid(cmd, 0);
+	memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
+	if (cmd->cmd_len == 0)
+		cmd->cmd_len = scsi_command_size(cmd->cmnd);
+}
+
+void scsi_device_unbusy(struct scsi_device *sdev)
+{
+	struct Scsi_Host *shost = sdev->host;
+	struct scsi_target *starget = scsi_target(sdev);
+	unsigned long flags;
+
+	atomic_dec(&shost->host_busy);
+	if (starget->can_queue > 0)
+		atomic_dec(&starget->target_busy);
+
+	if (unlikely(scsi_host_in_recovery(shost) &&
+		     (shost->host_failed || shost->host_eh_scheduled))) {
+		spin_lock_irqsave(shost->host_lock, flags);
+		scsi_eh_wakeup(shost);
+		spin_unlock_irqrestore(shost->host_lock, flags);
+	}
+
+	atomic_dec(&sdev->device_busy);
+}
+
+static void scsi_kick_queue(struct request_queue *q)
+{
+	if (q->mq_ops)
+		blk_mq_start_hw_queues(q);
+	else
+		blk_run_queue(q);
+}
+
+/*
+ * 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 (atomic_read(&sdev->device_busy) >= 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 (shost->can_queue > 0 &&
+	    atomic_read(&shost->host_busy) >= shost->can_queue)
+		return true;
+	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_cleanup_queue() before the queue is run from this
+		 * function then blk_run_queue() will return immediately since
+		 * blk_cleanup_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);
+}
+
+/*
+ * Function:   scsi_run_queue()
+ *
+ * Purpose:    Select a proper request queue to serve next
+ *
+ * Arguments:  q       - last request's queue
+ *
+ * Returns:     Nothing
+ *
+ * Notes:      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);
+
+	if (q->mq_ops)
+		blk_mq_start_stopped_hw_queues(q, false);
+	else
+		blk_run_queue(q);
+}
+
+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);
+}
+
+/*
+ * Function:	scsi_requeue_command()
+ *
+ * Purpose:	Handle post-processing of completed commands.
+ *
+ * Arguments:	q	- queue to operate on
+ *		cmd	- command that may need to be requeued.
+ *
+ * Returns:	Nothing
+ *
+ * Notes:	After command completion, there may be blocks left
+ *		over which weren't finished by the previous command
+ *		this can be for a number of reasons - the main one is
+ *		I/O errors in the middle of the request, in which case
+ *		we need to request the blocks that come after the bad
+ *		sector.
+ * Notes:	Upon return, cmd is a stale pointer.
+ */
+static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
+{
+	struct scsi_device *sdev = cmd->device;
+	struct request *req = cmd->request;
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	blk_unprep_request(req);
+	req->special = NULL;
+	scsi_put_command(cmd);
+	blk_requeue_request(q, req);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	scsi_run_queue(q);
+
+	put_device(&sdev->sdev_gendev);
+}
+
+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 inline unsigned int scsi_sgtable_index(unsigned short nents)
+{
+	unsigned int index;
+
+	BUG_ON(nents > SCSI_MAX_SG_SEGMENTS);
+
+	if (nents <= 8)
+		index = 0;
+	else
+		index = get_count_order(nents) - 3;
+
+	return index;
+}
+
+static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)
+{
+	struct scsi_host_sg_pool *sgp;
+
+	sgp = scsi_sg_pools + scsi_sgtable_index(nents);
+	mempool_free(sgl, sgp->pool);
+}
+
+static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
+{
+	struct scsi_host_sg_pool *sgp;
+
+	sgp = scsi_sg_pools + scsi_sgtable_index(nents);
+	return mempool_alloc(sgp->pool, gfp_mask);
+}
+
+static void scsi_free_sgtable(struct scsi_data_buffer *sdb, bool mq)
+{
+	if (mq && sdb->table.nents <= SCSI_MAX_SG_SEGMENTS)
+		return;
+	__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, mq, scsi_sg_free);
+}
+
+static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents, bool mq)
+{
+	struct scatterlist *first_chunk = NULL;
+	int ret;
+
+	BUG_ON(!nents);
+
+	if (mq) {
+		if (nents <= SCSI_MAX_SG_SEGMENTS) {
+			sdb->table.nents = nents;
+			sg_init_table(sdb->table.sgl, sdb->table.nents);
+			return 0;
+		}
+		first_chunk = sdb->table.sgl;
+	}
+
+	ret = __sg_alloc_table(&sdb->table, nents, SCSI_MAX_SG_SEGMENTS,
+			       first_chunk, GFP_ATOMIC, scsi_sg_alloc);
+	if (unlikely(ret))
+		scsi_free_sgtable(sdb, mq);
+	return ret;
+}
+
+static void scsi_uninit_cmd(struct scsi_cmnd *cmd)
+{
+	if (cmd->request->cmd_type == REQ_TYPE_FS) {
+		struct scsi_driver *drv = scsi_cmd_to_driver(cmd);
+
+		if (drv->uninit_command)
+			drv->uninit_command(cmd);
+	}
+}
+
+static void scsi_mq_free_sgtables(struct scsi_cmnd *cmd)
+{
+	if (cmd->sdb.table.nents)
+		scsi_free_sgtable(&cmd->sdb, true);
+	if (cmd->request->next_rq && cmd->request->next_rq->special)
+		scsi_free_sgtable(cmd->request->next_rq->special, true);
+	if (scsi_prot_sg_count(cmd))
+		scsi_free_sgtable(cmd->prot_sdb, true);
+}
+
+static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
+{
+	struct scsi_device *sdev = cmd->device;
+	struct Scsi_Host *shost = sdev->host;
+	unsigned long flags;
+
+	scsi_mq_free_sgtables(cmd);
+	scsi_uninit_cmd(cmd);
+
+	if (shost->use_cmd_list) {
+		BUG_ON(list_empty(&cmd->list));
+		spin_lock_irqsave(&sdev->list_lock, flags);
+		list_del_init(&cmd->list);
+		spin_unlock_irqrestore(&sdev->list_lock, flags);
+	}
+}
+
+/*
+ * Function:    scsi_release_buffers()
+ *
+ * Purpose:     Free resources allocate for a scsi_command.
+ *
+ * Arguments:   cmd	- command that we are bailing.
+ *
+ * Lock status: Assumed that no lock is held upon entry.
+ *
+ * Returns:     Nothing
+ *
+ * Notes:       In the event that an upper level driver rejects a
+ *		command, we must release resources allocated during
+ *		the __init_io() function.  Primarily this would involve
+ *		the scatter-gather table.
+ */
+static void scsi_release_buffers(struct scsi_cmnd *cmd)
+{
+	if (cmd->sdb.table.nents)
+		scsi_free_sgtable(&cmd->sdb, false);
+
+	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
+
+	if (scsi_prot_sg_count(cmd))
+		scsi_free_sgtable(cmd->prot_sdb, false);
+}
+
+static void scsi_release_bidi_buffers(struct scsi_cmnd *cmd)
+{
+	struct scsi_data_buffer *bidi_sdb = cmd->request->next_rq->special;
+
+	scsi_free_sgtable(bidi_sdb, false);
+	kmem_cache_free(scsi_sdb_cache, bidi_sdb);
+	cmd->request->next_rq->special = NULL;
+}
+
+static bool scsi_end_request(struct request *req, int error,
+		unsigned int bytes, unsigned int bidi_bytes)
+{
+	struct scsi_cmnd *cmd = req->special;
+	struct scsi_device *sdev = cmd->device;
+	struct request_queue *q = sdev->request_queue;
+
+	if (blk_update_request(req, error, bytes))
+		return true;
+
+	/* Bidi request must be completed as a whole */
+	if (unlikely(bidi_bytes) &&
+	    blk_update_request(req->next_rq, error, bidi_bytes))
+		return true;
+
+	if (blk_queue_add_random(q))
+		add_disk_randomness(req->rq_disk);
+
+	if (req->mq_ctx) {
+		/*
+		 * 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);
+
+		__blk_mq_end_request(req, error);
+
+		if (scsi_target(sdev)->single_lun ||
+		    !list_empty(&sdev->host->starved_list))
+			kblockd_schedule_work(&sdev->requeue_work);
+		else
+			blk_mq_start_stopped_hw_queues(q, true);
+	} else {
+		unsigned long flags;
+
+		if (bidi_bytes)
+			scsi_release_bidi_buffers(cmd);
+
+		spin_lock_irqsave(q->queue_lock, flags);
+		blk_finish_request(req, error);
+		spin_unlock_irqrestore(q->queue_lock, flags);
+
+		scsi_release_buffers(cmd);
+
+		scsi_put_command(cmd);
+		scsi_run_queue(q);
+	}
+
+	put_device(&sdev->sdev_gendev);
+	return false;
+}
+
+/**
+ * __scsi_error_from_host_byte - translate SCSI error code into errno
+ * @cmd:	SCSI command (unused)
+ * @result:	scsi error code
+ *
+ * Translate SCSI error code into standard UNIX errno.
+ * Return values:
+ * -ENOLINK	temporary transport failure
+ * -EREMOTEIO	permanent target failure, do not retry
+ * -EBADE	permanent nexus failure, retry on other path
+ * -ENOSPC	No write space available
+ * -ENODATA	Medium error
+ * -EIO		unspecified I/O error
+ */
+static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
+{
+	int error = 0;
+
+	switch(host_byte(result)) {
+	case DID_TRANSPORT_FAILFAST:
+		error = -ENOLINK;
+		break;
+	case DID_TARGET_FAILURE:
+		set_host_byte(cmd, DID_OK);
+		error = -EREMOTEIO;
+		break;
+	case DID_NEXUS_FAILURE:
+		set_host_byte(cmd, DID_OK);
+		error = -EBADE;
+		break;
+	case DID_ALLOC_FAILURE:
+		set_host_byte(cmd, DID_OK);
+		error = -ENOSPC;
+		break;
+	case DID_MEDIUM_ERROR:
+		set_host_byte(cmd, DID_OK);
+		error = -ENODATA;
+		break;
+	default:
+		error = -EIO;
+		break;
+	}
+
+	return error;
+}
+
+/*
+ * Function:    scsi_io_completion()
+ *
+ * Purpose:     Completion processing for block device I/O requests.
+ *
+ * Arguments:   cmd   - command that is finished.
+ *
+ * Lock status: Assumed that no lock is held upon entry.
+ *
+ * Returns:     Nothing
+ *
+ * Notes:       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_requeue_command().  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_queue_insert().  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 -EIO 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_queue *q = cmd->device->request_queue;
+	struct request *req = cmd->request;
+	int error = 0;
+	struct scsi_sense_hdr sshdr;
+	bool sense_valid = false;
+	int sense_deferred = 0, level = 0;
+	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
+	      ACTION_DELAYED_RETRY} action;
+	unsigned long wait_for = (cmd->allowed + 1) * req->timeout;
+
+	if (result) {
+		sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
+		if (sense_valid)
+			sense_deferred = scsi_sense_is_deferred(&sshdr);
+	}
+
+	if (req->cmd_type == REQ_TYPE_BLOCK_PC) { /* SG_IO ioctl from block level */
+		if (result) {
+			if (sense_valid && req->sense) {
+				/*
+				 * SG_IO wants current and deferred errors
+				 */
+				int len = 8 + cmd->sense_buffer[7];
+
+				if (len > SCSI_SENSE_BUFFERSIZE)
+					len = SCSI_SENSE_BUFFERSIZE;
+				memcpy(req->sense, cmd->sense_buffer,  len);
+				req->sense_len = len;
+			}
+			if (!sense_deferred)
+				error = __scsi_error_from_host_byte(cmd, result);
+		}
+		/*
+		 * __scsi_error_from_host_byte may have reset the host_byte
+		 */
+		req->errors = cmd->result;
+
+		req->resid_len = scsi_get_resid(cmd);
+
+		if (scsi_bidi_cmnd(cmd)) {
+			/*
+			 * Bidi commands Must be complete as a whole,
+			 * both sides at once.
+			 */
+			req->next_rq->resid_len = scsi_in(cmd)->resid;
+			if (scsi_end_request(req, 0, blk_rq_bytes(req),
+					blk_rq_bytes(req->next_rq)))
+				BUG();
+			return;
+		}
+	} else if (blk_rq_bytes(req) == 0 && result && !sense_deferred) {
+		/*
+		 * Certain non BLOCK_PC requests are commands that don't
+		 * actually transfer anything (FLUSH), so cannot use
+		 * good_bytes != blk_rq_bytes(req) as the signal for an error.
+		 * This sets the error explicitly for the problem case.
+		 */
+		error = __scsi_error_from_host_byte(cmd, result);
+	}
+
+	/* no bidi support for !REQ_TYPE_BLOCK_PC yet */
+	BUG_ON(blk_bidi_rq(req));
+
+	/*
+	 * 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));
+
+	/*
+	 * Recovered errors need reporting, but they're always treated
+	 * as success, so fiddle the result code here.  For BLOCK_PC
+	 * we already took a copy of the original into rq->errors which
+	 * is what gets returned to the user
+	 */
+	if (sense_valid && (sshdr.sense_key == RECOVERED_ERROR)) {
+		/* if ATA PASS-THROUGH INFORMATION AVAILABLE 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))
+			;
+		else if (!(req->cmd_flags & REQ_QUIET))
+			scsi_print_sense(cmd);
+		result = 0;
+		/* BLOCK_PC may have set error */
+		error = 0;
+	}
+
+	/*
+	 * If we finished all bytes in the request we are done now.
+	 */
+	if (!scsi_end_request(req, error, good_bytes, 0))
+		return;
+
+	/*
+	 * Kill remainder if no retrys.
+	 */
+	if (error && scsi_noretry_cmd(cmd)) {
+		if (scsi_end_request(req, error, blk_rq_bytes(req), 0))
+			BUG();
+		return;
+	}
+
+	/*
+	 * If there had been no error, but we have leftover bytes in the
+	 * requeues just queue the command up again.
+	 */
+	if (result == 0)
+		goto requeue;
+
+	error = __scsi_error_from_host_byte(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_deferred) {
+		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;
+				error = -EILSEQ;
+			/* INVALID COMMAND OPCODE or INVALID FIELD IN CDB */
+			} else if (sshdr.asc == 0x20 || sshdr.asc == 0x24) {
+				action = ACTION_FAIL;
+				error = -EREMOTEIO;
+			} else
+				action = ACTION_FAIL;
+			break;
+		case ABORTED_COMMAND:
+			action = ACTION_FAIL;
+			if (sshdr.asc == 0x10) /* DIF */
+				error = -EILSEQ;
+			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 0x14: /* space allocation in progress */
+					action = ACTION_DELAYED_RETRY;
+					break;
+				default:
+					action = ACTION_FAIL;
+					break;
+				}
+			} else
+				action = ACTION_FAIL;
+			break;
+		case VOLUME_OVERFLOW:
+			/* See SSC3rXX or current. */
+			action = ACTION_FAIL;
+			break;
+		default:
+			action = ACTION_FAIL;
+			break;
+		}
+	} else
+		action = ACTION_FAIL;
+
+	if (action != ACTION_FAIL &&
+	    time_before(cmd->jiffies_at_alloc + wait_for, jiffies))
+		action = ACTION_FAIL;
+
+	switch (action) {
+	case ACTION_FAIL:
+		/* Give up and fail the remainder of the request */
+		if (!(req->cmd_flags & REQ_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 (driver_byte(result) & DRIVER_SENSE)
+					scsi_print_sense(cmd);
+				scsi_print_command(cmd);
+			}
+		}
+		if (!scsi_end_request(req, error, blk_rq_err_bytes(req), 0))
+			return;
+		/*FALLTHRU*/
+	case ACTION_REPREP:
+	requeue:
+		/* Unprep the request and put it back at the head of the queue.
+		 * A new command will be prepared and issued.
+		 */
+		if (q->mq_ops) {
+			cmd->request->cmd_flags &= ~REQ_DONTPREP;
+			scsi_mq_uninit_cmd(cmd);
+			scsi_mq_requeue_cmd(cmd);
+		} else {
+			scsi_release_buffers(cmd);
+			scsi_requeue_command(q, cmd);
+		}
+		break;
+	case ACTION_RETRY:
+		/* Retry the same command immediately */
+		__scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, 0);
+		break;
+	case ACTION_DELAYED_RETRY:
+		/* Retry the same command after a delay */
+		__scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, 0);
+		break;
+	}
+}
+
+static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb)
+{
+	int count;
+
+	/*
+	 * If sg table allocation fails, requeue request later.
+	 */
+	if (unlikely(scsi_alloc_sgtable(sdb, req->nr_phys_segments,
+					req->mq_ctx != NULL)))
+		return BLKPREP_DEFER;
+
+	/* 
+	 * Next, walk the list, and fill in the addresses and sizes of
+	 * each segment.
+	 */
+	count = blk_rq_map_sg(req->q, req, sdb->table.sgl);
+	BUG_ON(count > sdb->table.nents);
+	sdb->table.nents = count;
+	sdb->length = blk_rq_bytes(req);
+	return BLKPREP_OK;
+}
+
+/*
+ * Function:    scsi_init_io()
+ *
+ * Purpose:     SCSI I/O initialize function.
+ *
+ * Arguments:   cmd   - Command descriptor we wish to initialize
+ *
+ * Returns:     0 on success
+ *		BLKPREP_DEFER if the failure is retryable
+ *		BLKPREP_KILL if the failure is fatal
+ */
+int scsi_init_io(struct scsi_cmnd *cmd)
+{
+	struct scsi_device *sdev = cmd->device;
+	struct request *rq = cmd->request;
+	bool is_mq = (rq->mq_ctx != NULL);
+	int error;
+
+	BUG_ON(!rq->nr_phys_segments);
+
+	error = scsi_init_sgtable(rq, &cmd->sdb);
+	if (error)
+		goto err_exit;
+
+	if (blk_bidi_rq(rq)) {
+		if (!rq->q->mq_ops) {
+			struct scsi_data_buffer *bidi_sdb =
+				kmem_cache_zalloc(scsi_sdb_cache, GFP_ATOMIC);
+			if (!bidi_sdb) {
+				error = BLKPREP_DEFER;
+				goto err_exit;
+			}
+
+			rq->next_rq->special = bidi_sdb;
+		}
+
+		error = scsi_init_sgtable(rq->next_rq, rq->next_rq->special);
+		if (error)
+			goto err_exit;
+	}
+
+	if (blk_integrity_rq(rq)) {
+		struct scsi_data_buffer *prot_sdb = cmd->prot_sdb;
+		int ivecs, count;
+
+		if (prot_sdb == NULL) {
+			/*
+			 * This can happen if someone (e.g. multipath)
+			 * queues a command to a device on an adapter
+			 * that does not support DIX.
+			 */
+			WARN_ON_ONCE(1);
+			error = BLKPREP_KILL;
+			goto err_exit;
+		}
+
+		ivecs = blk_rq_count_integrity_sg(rq->q, rq->bio);
+
+		if (scsi_alloc_sgtable(prot_sdb, ivecs, is_mq)) {
+			error = BLKPREP_DEFER;
+			goto err_exit;
+		}
+
+		count = blk_rq_map_integrity_sg(rq->q, rq->bio,
+						prot_sdb->table.sgl);
+		BUG_ON(unlikely(count > ivecs));
+		BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
+
+		cmd->prot_sdb = prot_sdb;
+		cmd->prot_sdb->table.nents = count;
+	}
+
+	return BLKPREP_OK;
+err_exit:
+	if (is_mq) {
+		scsi_mq_free_sgtables(cmd);
+	} else {
+		scsi_release_buffers(cmd);
+		cmd->request->special = NULL;
+		scsi_put_command(cmd);
+		put_device(&sdev->sdev_gendev);
+	}
+	return error;
+}
+EXPORT_SYMBOL(scsi_init_io);
+
+static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
+		struct request *req)
+{
+	struct scsi_cmnd *cmd;
+
+	if (!req->special) {
+		/* Bail if we can't get a reference to the device */
+		if (!get_device(&sdev->sdev_gendev))
+			return NULL;
+
+		cmd = scsi_get_command(sdev, GFP_ATOMIC);
+		if (unlikely(!cmd)) {
+			put_device(&sdev->sdev_gendev);
+			return NULL;
+		}
+		req->special = cmd;
+	} else {
+		cmd = req->special;
+	}
+
+	/* pull a tag out of the request if we have one */
+	cmd->tag = req->tag;
+	cmd->request = req;
+
+	cmd->cmnd = req->cmd;
+	cmd->prot_op = SCSI_PROT_NORMAL;
+
+	return cmd;
+}
+
+static int scsi_setup_blk_pc_cmnd(struct scsi_device *sdev, struct request *req)
+{
+	struct scsi_cmnd *cmd = req->special;
+
+	/*
+	 * BLOCK_PC 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) {
+		int ret = scsi_init_io(cmd);
+		if (unlikely(ret))
+			return ret;
+	} else {
+		BUG_ON(blk_rq_bytes(req));
+
+		memset(&cmd->sdb, 0, sizeof(cmd->sdb));
+	}
+
+	cmd->cmd_len = req->cmd_len;
+	cmd->transfersize = blk_rq_bytes(req);
+	cmd->allowed = req->retries;
+	return BLKPREP_OK;
+}
+
+/*
+ * Setup a REQ_TYPE_FS command.  These are simple request from filesystems
+ * that still need to be translated to SCSI CDBs from the ULD.
+ */
+static int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
+{
+	struct scsi_cmnd *cmd = req->special;
+
+	if (unlikely(sdev->scsi_dh_data && sdev->scsi_dh_data->scsi_dh
+			 && sdev->scsi_dh_data->scsi_dh->prep_fn)) {
+		int ret = sdev->scsi_dh_data->scsi_dh->prep_fn(sdev, req);
+		if (ret != BLKPREP_OK)
+			return ret;
+	}
+
+	memset(cmd->cmnd, 0, BLK_MAX_CDB);
+	return scsi_cmd_to_driver(cmd)->init_command(cmd);
+}
+
+static int scsi_setup_cmnd(struct scsi_device *sdev, struct request *req)
+{
+	struct scsi_cmnd *cmd = req->special;
+
+	if (!blk_rq_bytes(req))
+		cmd->sc_data_direction = DMA_NONE;
+	else if (rq_data_dir(req) == WRITE)
+		cmd->sc_data_direction = DMA_TO_DEVICE;
+	else
+		cmd->sc_data_direction = DMA_FROM_DEVICE;
+
+	switch (req->cmd_type) {
+	case REQ_TYPE_FS:
+		return scsi_setup_fs_cmnd(sdev, req);
+	case REQ_TYPE_BLOCK_PC:
+		return scsi_setup_blk_pc_cmnd(sdev, req);
+	default:
+		return BLKPREP_KILL;
+	}
+}
+
+static int
+scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
+{
+	int ret = BLKPREP_OK;
+
+	/*
+	 * If the device is not in running state we will reject some
+	 * or all commands.
+	 */
+	if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
+		switch (sdev->sdev_state) {
+		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.
+			 */
+			sdev_printk(KERN_ERR, sdev,
+				    "rejecting I/O to offline device\n");
+			ret = BLKPREP_KILL;
+			break;
+		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");
+			ret = BLKPREP_KILL;
+			break;
+		case SDEV_BLOCK:
+		case SDEV_CREATED_BLOCK:
+			ret = BLKPREP_DEFER;
+			break;
+		case SDEV_QUIESCE:
+			/*
+			 * If the devices is blocked we defer normal commands.
+			 */
+			if (!(req->cmd_flags & REQ_PREEMPT))
+				ret = BLKPREP_DEFER;
+			break;
+		default:
+			/*
+			 * For any other not fully online state we only allow
+			 * special commands.  In particular any user initiated
+			 * command is not allowed.
+			 */
+			if (!(req->cmd_flags & REQ_PREEMPT))
+				ret = BLKPREP_KILL;
+			break;
+		}
+	}
+	return ret;
+}
+
+static int
+scsi_prep_return(struct request_queue *q, struct request *req, int ret)
+{
+	struct scsi_device *sdev = q->queuedata;
+
+	switch (ret) {
+	case BLKPREP_KILL:
+		req->errors = DID_NO_CONNECT << 16;
+		/* release the command and kill it */
+		if (req->special) {
+			struct scsi_cmnd *cmd = req->special;
+			scsi_release_buffers(cmd);
+			scsi_put_command(cmd);
+			put_device(&sdev->sdev_gendev);
+			req->special = NULL;
+		}
+		break;
+	case BLKPREP_DEFER:
+		/*
+		 * If we defer, the blk_peek_request() returns NULL, but the
+		 * queue must be restarted, so we schedule a callback to happen
+		 * shortly.
+		 */
+		if (atomic_read(&sdev->device_busy) == 0)
+			blk_delay_queue(q, SCSI_QUEUE_DELAY);
+		break;
+	default:
+		req->cmd_flags |= REQ_DONTPREP;
+	}
+
+	return ret;
+}
+
+static int scsi_prep_fn(struct request_queue *q, struct request *req)
+{
+	struct scsi_device *sdev = q->queuedata;
+	struct scsi_cmnd *cmd;
+	int ret;
+
+	ret = scsi_prep_state_check(sdev, req);
+	if (ret != BLKPREP_OK)
+		goto out;
+
+	cmd = scsi_get_cmd_from_req(sdev, req);
+	if (unlikely(!cmd)) {
+		ret = BLKPREP_DEFER;
+		goto out;
+	}
+
+	ret = scsi_setup_cmnd(sdev, req);
+out:
+	return scsi_prep_return(q, req, ret);
+}
+
+static void scsi_unprep_fn(struct request_queue *q, struct request *req)
+{
+	scsi_uninit_cmd(req->special);
+}
+
+/*
+ * scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
+ * return 0.
+ *
+ * Called with the queue_lock held.
+ */
+static inline int scsi_dev_queue_ready(struct request_queue *q,
+				  struct scsi_device *sdev)
+{
+	unsigned int busy;
+
+	busy = atomic_inc_return(&sdev->device_busy) - 1;
+	if (atomic_read(&sdev->device_blocked)) {
+		if (busy)
+			goto out_dec;
+
+		/*
+		 * unblock after device_blocked iterates to zero
+		 */
+		if (atomic_dec_return(&sdev->device_blocked) > 0) {
+			/*
+			 * For the MQ case we take care of this in the caller.
+			 */
+			if (!q->mq_ops)
+				blk_delay_queue(q, SCSI_QUEUE_DELAY);
+			goto out_dec;
+		}
+		SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
+				   "unblocking device at zero depth\n"));
+	}
+
+	if (busy >= sdev->queue_depth)
+		goto out_dec;
+
+	return 1;
+out_dec:
+	atomic_dec(&sdev->device_busy);
+	return 0;
+}
+
+/*
+ * 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)
+{
+	unsigned int busy;
+
+	if (scsi_host_in_recovery(shost))
+		return 0;
+
+	busy = atomic_inc_return(&shost->host_busy) - 1;
+	if (atomic_read(&shost->host_blocked) > 0) {
+		if (busy)
+			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->can_queue > 0 && busy >= shost->can_queue)
+		goto starved;
+	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);
+	}
+
+	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:
+	atomic_dec(&shost->host_busy);
+	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 int scsi_lld_busy(struct request_queue *q)
+{
+	struct scsi_device *sdev = q->queuedata;
+	struct Scsi_Host *shost;
+
+	if (blk_queue_dying(q))
+		return 0;
+
+	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 1;
+
+	return 0;
+}
+
+/*
+ * Kill a request for a dead device
+ */
+static void scsi_kill_request(struct request *req, struct request_queue *q)
+{
+	struct scsi_cmnd *cmd = req->special;
+	struct scsi_device *sdev;
+	struct scsi_target *starget;
+	struct Scsi_Host *shost;
+
+	blk_start_request(req);
+
+	scmd_printk(KERN_INFO, cmd, "killing request\n");
+
+	sdev = cmd->device;
+	starget = scsi_target(sdev);
+	shost = sdev->host;
+	scsi_init_cmd_errh(cmd);
+	cmd->result = DID_NO_CONNECT << 16;
+	atomic_inc(&cmd->device->iorequest_cnt);
+
+	/*
+	 * SCSI request completion path will do scsi_device_unbusy(),
+	 * bump busy counts.  To bump the counters, we need to dance
+	 * with the locks as normal issue path does.
+	 */
+	atomic_inc(&sdev->device_busy);
+	atomic_inc(&shost->host_busy);
+	if (starget->can_queue > 0)
+		atomic_inc(&starget->target_busy);
+
+	blk_complete_request(req);
+}
+
+static void scsi_softirq_done(struct request *rq)
+{
+	struct scsi_cmnd *cmd = rq->special;
+	unsigned long wait_for = (cmd->allowed + 1) * rq->timeout;
+	int 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 &&
+	    time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
+		sdev_printk(KERN_ERR, cmd->device,
+			    "timing out command, waited %lus\n",
+			    wait_for/HZ);
+		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:
+			if (!scsi_eh_scmd_add(cmd, 0))
+				scsi_finish_command(cmd);
+	}
+}
+
+/**
+ * scsi_dispatch_command - 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:
+	cmd->scsi_done(cmd);
+	return 0;
+}
+
+/**
+ * scsi_done - Invoke completion on finished SCSI command.
+ * @cmd: The SCSI Command for which a low-level device driver (LLDD) gives
+ * ownership back to SCSI Core -- i.e. the LLDD has finished with it.
+ *
+ * Description: This function is the mid-level's (SCSI Core) interrupt routine,
+ * which regains ownership of the SCSI command (de facto) from a LLDD, and
+ * calls blk_complete_request() for further processing.
+ *
+ * This function is interrupt context safe.
+ */
+static void scsi_done(struct scsi_cmnd *cmd)
+{
+	trace_scsi_dispatch_cmd_done(cmd);
+	blk_complete_request(cmd->request);
+}
+
+/*
+ * Function:    scsi_request_fn()
+ *
+ * Purpose:     Main strategy routine for SCSI.
+ *
+ * Arguments:   q       - Pointer to actual queue.
+ *
+ * Returns:     Nothing
+ *
+ * Lock status: IO request lock assumed to be held when called.
+ */
+static void scsi_request_fn(struct request_queue *q)
+	__releases(q->queue_lock)
+	__acquires(q->queue_lock)
+{
+	struct scsi_device *sdev = q->queuedata;
+	struct Scsi_Host *shost;
+	struct scsi_cmnd *cmd;
+	struct request *req;
+
+	/*
+	 * To start with, we keep looping until the queue is empty, or until
+	 * the host is no longer able to accept any more requests.
+	 */
+	shost = sdev->host;
+	for (;;) {
+		int rtn;
+		/*
+		 * get next queueable request.  We do this early to make sure
+		 * that the request is fully prepared even if we cannot
+		 * accept it.
+		 */
+		req = blk_peek_request(q);
+		if (!req)
+			break;
+
+		if (unlikely(!scsi_device_online(sdev))) {
+			sdev_printk(KERN_ERR, sdev,
+				    "rejecting I/O to offline device\n");
+			scsi_kill_request(req, q);
+			continue;
+		}
+
+		if (!scsi_dev_queue_ready(q, sdev))
+			break;
+
+		/*
+		 * Remove the request from the request list.
+		 */
+		if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
+			blk_start_request(req);
+
+		spin_unlock_irq(q->queue_lock);
+		cmd = req->special;
+		if (unlikely(cmd == NULL)) {
+			printk(KERN_CRIT "impossible request in %s.\n"
+					 "please mail a stack trace to "
+					 "linux-scsi@vger.kernel.org\n",
+					 __func__);
+			blk_dump_rq_flags(req, "foo");
+			BUG();
+		}
+
+		/*
+		 * We hit this when the driver is using a host wide
+		 * tag map. For device level tag maps the queue_depth check
+		 * in the device ready fn would prevent us from trying
+		 * to allocate a tag. Since the map is a shared host resource
+		 * we add the dev to the starved list so it eventually gets
+		 * a run when a tag is freed.
+		 */
+		if (blk_queue_tagged(q) && !(req->cmd_flags & REQ_QUEUED)) {
+			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);
+			goto not_ready;
+		}
+
+		if (!scsi_target_queue_ready(shost, sdev))
+			goto not_ready;
+
+		if (!scsi_host_queue_ready(q, shost, sdev))
+			goto host_not_ready;
+	
+		if (sdev->simple_tags)
+			cmd->flags |= SCMD_TAGGED;
+		else
+			cmd->flags &= ~SCMD_TAGGED;
+
+		/*
+		 * Finally, initialize any error handling parameters, and set up
+		 * the timers for timeouts.
+		 */
+		scsi_init_cmd_errh(cmd);
+
+		/*
+		 * Dispatch the command to the low-level driver.
+		 */
+		cmd->scsi_done = scsi_done;
+		rtn = scsi_dispatch_cmd(cmd);
+		if (rtn) {
+			scsi_queue_insert(cmd, rtn);
+			spin_lock_irq(q->queue_lock);
+			goto out_delay;
+		}
+		spin_lock_irq(q->queue_lock);
+	}
+
+	return;
+
+ host_not_ready:
+	if (scsi_target(sdev)->can_queue > 0)
+		atomic_dec(&scsi_target(sdev)->target_busy);
+ not_ready:
+	/*
+	 * lock q, handle tag, requeue req, and decrement device_busy. We
+	 * must return with queue_lock held.
+	 *
+	 * Decrementing device_busy without checking it is OK, as all such
+	 * cases (host limits or settings) should run the queue at some
+	 * later time.
+	 */
+	spin_lock_irq(q->queue_lock);
+	blk_requeue_request(q, req);
+	atomic_dec(&sdev->device_busy);
+out_delay:
+	if (!atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev))
+		blk_delay_queue(q, SCSI_QUEUE_DELAY);
+}
+
+static inline int prep_to_mq(int ret)
+{
+	switch (ret) {
+	case BLKPREP_OK:
+		return 0;
+	case BLKPREP_DEFER:
+		return BLK_MQ_RQ_QUEUE_BUSY;
+	default:
+		return BLK_MQ_RQ_QUEUE_ERROR;
+	}
+}
+
+static int scsi_mq_prep_fn(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;
+	unsigned char *sense_buf = cmd->sense_buffer;
+	struct scatterlist *sg;
+
+	memset(cmd, 0, sizeof(struct scsi_cmnd));
+
+	req->special = cmd;
+
+	cmd->request = req;
+	cmd->device = sdev;
+	cmd->sense_buffer = sense_buf;
+
+	cmd->tag = req->tag;
+
+	cmd->cmnd = req->cmd;
+	cmd->prot_op = SCSI_PROT_NORMAL;
+
+	INIT_LIST_HEAD(&cmd->list);
+	INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
+	cmd->jiffies_at_alloc = jiffies;
+
+	if (shost->use_cmd_list) {
+		spin_lock_irq(&sdev->list_lock);
+		list_add_tail(&cmd->list, &sdev->cmd_list);
+		spin_unlock_irq(&sdev->list_lock);
+	}
+
+	sg = (void *)cmd + sizeof(struct scsi_cmnd) + shost->hostt->cmd_size;
+	cmd->sdb.table.sgl = sg;
+
+	if (scsi_host_get_prot(shost)) {
+		cmd->prot_sdb = (void *)sg +
+			min_t(unsigned int,
+			      shost->sg_tablesize, SCSI_MAX_SG_SEGMENTS) *
+			sizeof(struct scatterlist);
+		memset(cmd->prot_sdb, 0, sizeof(struct scsi_data_buffer));
+
+		cmd->prot_sdb->table.sgl =
+			(struct scatterlist *)(cmd->prot_sdb + 1);
+	}
+
+	if (blk_bidi_rq(req)) {
+		struct request *next_rq = req->next_rq;
+		struct scsi_data_buffer *bidi_sdb = blk_mq_rq_to_pdu(next_rq);
+
+		memset(bidi_sdb, 0, sizeof(struct scsi_data_buffer));
+		bidi_sdb->table.sgl =
+			(struct scatterlist *)(bidi_sdb + 1);
+
+		next_rq->special = bidi_sdb;
+	}
+
+	blk_mq_start_request(req);
+
+	return scsi_setup_cmnd(sdev, req);
+}
+
+static void scsi_mq_done(struct scsi_cmnd *cmd)
+{
+	trace_scsi_dispatch_cmd_done(cmd);
+	blk_mq_complete_request(cmd->request);
+}
+
+static int 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);
+	int ret;
+	int reason;
+
+	ret = prep_to_mq(scsi_prep_state_check(sdev, req));
+	if (ret)
+		goto out;
+
+	ret = BLK_MQ_RQ_QUEUE_BUSY;
+	if (!get_device(&sdev->sdev_gendev))
+		goto out;
+
+	if (!scsi_dev_queue_ready(q, sdev))
+		goto out_put_device;
+	if (!scsi_target_queue_ready(shost, sdev))
+		goto out_dec_device_busy;
+	if (!scsi_host_queue_ready(q, shost, sdev))
+		goto out_dec_target_busy;
+
+
+	if (!(req->cmd_flags & REQ_DONTPREP)) {
+		ret = prep_to_mq(scsi_mq_prep_fn(req));
+		if (ret)
+			goto out_dec_host_busy;
+		req->cmd_flags |= REQ_DONTPREP;
+	} else {
+		blk_mq_start_request(req);
+	}
+
+	if (sdev->simple_tags)
+		cmd->flags |= SCMD_TAGGED;
+	else
+		cmd->flags &= ~SCMD_TAGGED;
+
+	scsi_init_cmd_errh(cmd);
+	cmd->scsi_done = scsi_mq_done;
+
+	reason = scsi_dispatch_cmd(cmd);
+	if (reason) {
+		scsi_set_blocked(cmd, reason);
+		ret = BLK_MQ_RQ_QUEUE_BUSY;
+		goto out_dec_host_busy;
+	}
+
+	return BLK_MQ_RQ_QUEUE_OK;
+
+out_dec_host_busy:
+	atomic_dec(&shost->host_busy);
+out_dec_target_busy:
+	if (scsi_target(sdev)->can_queue > 0)
+		atomic_dec(&scsi_target(sdev)->target_busy);
+out_dec_device_busy:
+	atomic_dec(&sdev->device_busy);
+out_put_device:
+	put_device(&sdev->sdev_gendev);
+out:
+	switch (ret) {
+	case BLK_MQ_RQ_QUEUE_BUSY:
+		blk_mq_stop_hw_queue(hctx);
+		if (atomic_read(&sdev->device_busy) == 0 &&
+		    !scsi_device_blocked(sdev))
+			blk_mq_delay_queue(hctx, SCSI_QUEUE_DELAY);
+		break;
+	case BLK_MQ_RQ_QUEUE_ERROR:
+		/*
+		 * Make sure to release all allocated ressources when
+		 * we hit an error, as we will never see this command
+		 * again.
+		 */
+		if (req->cmd_flags & REQ_DONTPREP)
+			scsi_mq_uninit_cmd(cmd);
+		break;
+	default:
+		break;
+	}
+	return ret;
+}
+
+static enum blk_eh_timer_return scsi_timeout(struct request *req,
+		bool reserved)
+{
+	if (reserved)
+		return BLK_EH_RESET_TIMER;
+	return scsi_times_out(req);
+}
+
+static int scsi_init_request(void *data, struct request *rq,
+		unsigned int hctx_idx, unsigned int request_idx,
+		unsigned int numa_node)
+{
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
+
+	cmd->sense_buffer = kzalloc_node(SCSI_SENSE_BUFFERSIZE, GFP_KERNEL,
+			numa_node);
+	if (!cmd->sense_buffer)
+		return -ENOMEM;
+	return 0;
+}
+
+static void scsi_exit_request(void *data, struct request *rq,
+		unsigned int hctx_idx, unsigned int request_idx)
+{
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
+
+	kfree(cmd->sense_buffer);
+}
+
+static u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
+{
+	struct device *host_dev;
+	u64 bounce_limit = 0xffffffff;
+
+	if (shost->unchecked_isa_dma)
+		return BLK_BOUNCE_ISA;
+	/*
+	 * Platforms with virtual-DMA translation
+	 * hardware have no practical limit.
+	 */
+	if (!PCI_DMA_BUS_IS_PHYS)
+		return BLK_BOUNCE_ANY;
+
+	host_dev = scsi_get_device(shost);
+	if (host_dev && host_dev->dma_mask)
+		bounce_limit = (u64)dma_max_pfn(host_dev) << PAGE_SHIFT;
+
+	return bounce_limit;
+}
+
+static 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,
+					SCSI_MAX_SG_CHAIN_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_bounce_limit(q, scsi_calculate_bounce_limit(shost));
+	blk_queue_segment_boundary(q, shost->dma_boundary);
+	dma_set_seg_boundary(dev, shost->dma_boundary);
+
+	blk_queue_max_segment_size(q, dma_get_max_seg_size(dev));
+
+	if (!shost->use_clustering)
+		q->limits.cluster = 0;
+
+	/*
+	 * set a reasonable default alignment on word boundaries: the
+	 * host and device may alter it using
+	 * blk_queue_update_dma_alignment() later.
+	 */
+	blk_queue_dma_alignment(q, 0x03);
+}
+
+struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
+					 request_fn_proc *request_fn)
+{
+	struct request_queue *q;
+
+	q = blk_init_queue(request_fn, NULL);
+	if (!q)
+		return NULL;
+	__scsi_init_queue(shost, q);
+	return q;
+}
+EXPORT_SYMBOL(__scsi_alloc_queue);
+
+struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
+{
+	struct request_queue *q;
+
+	q = __scsi_alloc_queue(sdev->host, scsi_request_fn);
+	if (!q)
+		return NULL;
+
+	blk_queue_prep_rq(q, scsi_prep_fn);
+	blk_queue_unprep_rq(q, scsi_unprep_fn);
+	blk_queue_softirq_done(q, scsi_softirq_done);
+	blk_queue_rq_timed_out(q, scsi_times_out);
+	blk_queue_lld_busy(q, scsi_lld_busy);
+	return q;
+}
+
+static struct blk_mq_ops scsi_mq_ops = {
+	.map_queue	= blk_mq_map_queue,
+	.queue_rq	= scsi_queue_rq,
+	.complete	= scsi_softirq_done,
+	.timeout	= scsi_timeout,
+	.init_request	= scsi_init_request,
+	.exit_request	= scsi_exit_request,
+};
+
+struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev)
+{
+	sdev->request_queue = blk_mq_init_queue(&sdev->host->tag_set);
+	if (IS_ERR(sdev->request_queue))
+		return NULL;
+
+	sdev->request_queue->queuedata = sdev;
+	__scsi_init_queue(sdev->host, sdev->request_queue);
+	return sdev->request_queue;
+}
+
+int scsi_mq_setup_tags(struct Scsi_Host *shost)
+{
+	unsigned int cmd_size, sgl_size, tbl_size;
+
+	tbl_size = shost->sg_tablesize;
+	if (tbl_size > SCSI_MAX_SG_SEGMENTS)
+		tbl_size = SCSI_MAX_SG_SEGMENTS;
+	sgl_size = tbl_size * sizeof(struct scatterlist);
+	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) + sgl_size;
+
+	memset(&shost->tag_set, 0, sizeof(shost->tag_set));
+	shost->tag_set.ops = &scsi_mq_ops;
+	shost->tag_set.nr_hw_queues = shost->nr_hw_queues ? : 1;
+	shost->tag_set.queue_depth = shost->can_queue;
+	shost->tag_set.cmd_size = cmd_size;
+	shost->tag_set.numa_node = NUMA_NO_NODE;
+	shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;
+	shost->tag_set.flags |=
+		BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
+	shost->tag_set.driver_data = shost;
+
+	return blk_mq_alloc_tag_set(&shost->tag_set);
+}
+
+void scsi_mq_destroy_tags(struct Scsi_Host *shost)
+{
+	blk_mq_free_tag_set(&shost->tag_set);
+}
+
+/*
+ * Function:    scsi_block_requests()
+ *
+ * Purpose:     Utility function used by low-level drivers to prevent further
+ *		commands from being queued to the device.
+ *
+ * Arguments:   shost       - Host in question
+ *
+ * Returns:     Nothing
+ *
+ * Lock status: No locks are assumed held.
+ *
+ * Notes:       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);
+
+/*
+ * Function:    scsi_unblock_requests()
+ *
+ * Purpose:     Utility function used by low-level drivers to allow further
+ *		commands from being queued to the device.
+ *
+ * Arguments:   shost       - Host in question
+ *
+ * Returns:     Nothing
+ *
+ * Lock status: No locks are assumed held.
+ *
+ * Notes:       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);
+
+int __init scsi_init_queue(void)
+{
+	int i;
+
+	scsi_sdb_cache = kmem_cache_create("scsi_data_buffer",
+					   sizeof(struct scsi_data_buffer),
+					   0, 0, NULL);
+	if (!scsi_sdb_cache) {
+		printk(KERN_ERR "SCSI: can't init scsi sdb cache\n");
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < SG_MEMPOOL_NR; i++) {
+		struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
+		int size = sgp->size * sizeof(struct scatterlist);
+
+		sgp->slab = kmem_cache_create(sgp->name, size, 0,
+				SLAB_HWCACHE_ALIGN, NULL);
+		if (!sgp->slab) {
+			printk(KERN_ERR "SCSI: can't init sg slab %s\n",
+					sgp->name);
+			goto cleanup_sdb;
+		}
+
+		sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
+						     sgp->slab);
+		if (!sgp->pool) {
+			printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
+					sgp->name);
+			goto cleanup_sdb;
+		}
+	}
+
+	return 0;
+
+cleanup_sdb:
+	for (i = 0; i < SG_MEMPOOL_NR; i++) {
+		struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
+		if (sgp->pool)
+			mempool_destroy(sgp->pool);
+		if (sgp->slab)
+			kmem_cache_destroy(sgp->slab);
+	}
+	kmem_cache_destroy(scsi_sdb_cache);
+
+	return -ENOMEM;
+}
+
+void scsi_exit_queue(void)
+{
+	int i;
+
+	kmem_cache_destroy(scsi_sdb_cache);
+
+	for (i = 0; i < SG_MEMPOOL_NR; i++) {
+		struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
+		mempool_destroy(sgp->pool);
+		kmem_cache_destroy(sgp->slab);
+	}
+}
+
+/**
+ *	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)
+ *	@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; negative error number or scsi
+ *	status on error
+ *
+ */
+int
+scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
+		 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);
+
+	if (sdev->use_10_for_ms) {
+		if (len > 65535)
+			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;
+		real_buffer[6] = data->block_descriptor_length >> 8;
+		real_buffer[7] = data->block_descriptor_length;
+
+		cmd[0] = MODE_SELECT_10;
+		cmd[7] = len >> 8;
+		cmd[8] = len;
+	} else {
+		if (len > 255 || data->block_descriptor_length > 255 ||
+		    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 if mode sense will allow block descriptors to be returned
+ *	@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 unsuccessful, or the header offset (either 4
+ *	or 8 depending on whether a six or ten byte command was
+ *	issued) if successful.
+ */
+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;
+	struct scsi_sense_hdr my_sshdr;
+
+	memset(data, 0, sizeof(*data));
+	memset(&cmd[0], 0, 12);
+	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;
+
+	if (use_10_for_ms) {
+		if (len < 8)
+			len = 8;
+
+		cmd[0] = MODE_SENSE_10;
+		cmd[8] = len;
+		header_length = 8;
+	} else {
+		if (len < 4)
+			len = 4;
+
+		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);
+
+	/* 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 (use_10_for_ms && !scsi_status_is_good(result) &&
+	    (driver_byte(result) & DRIVER_SENSE)) {
+		if (scsi_sense_valid(sshdr)) {
+			if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
+			    (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
+				/* 
+				 * Invalid command operation code
+				 */
+				sdev->use_10_for_ms = 0;
+				goto retry;
+			}
+		}
+	}
+
+	if(scsi_status_is_good(result)) {
+		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 = buffer[0]*256 + buffer[1] + 2;
+			data->medium_type = buffer[2];
+			data->device_specific = buffer[3];
+			data->longlba = buffer[4] & 0x01;
+			data->block_descriptor_length = buffer[6]*256
+				+ buffer[7];
+		} 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 result;
+}
+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_external: Optional pointer to struct scsi_sense_hdr for
+ *		returning sense. Make sure that this is cleared before passing
+ *		in.
+ *
+ *	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_external)
+{
+	char cmd[] = {
+		TEST_UNIT_READY, 0, 0, 0, 0, 0,
+	};
+	struct scsi_sense_hdr *sshdr;
+	int result;
+
+	if (!sshdr_external)
+		sshdr = kzalloc(sizeof(*sshdr), GFP_KERNEL);
+	else
+		sshdr = sshdr_external;
+
+	/* try to eat the UNIT_ATTENTION if there are enough retries */
+	do {
+		result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
+					  timeout, retries, 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);
+
+	if (!sshdr_external)
+		kfree(sshdr);
+	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 unsuccessful 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:
+			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:
+		case SDEV_BLOCK:
+			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_CREATED_BLOCK:
+			break;
+		default:
+			goto illegal;
+		}
+		break;
+
+	}
+	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);
+
+/**
+ * 	sdev_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:
+		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;
+	default:
+		/* do nothing */
+		break;
+	}
+
+	envp[idx++] = NULL;
+
+	kobject_uevent_env(&sdev->sdev_gendev.kobj, KOBJ_CHANGE, envp);
+}
+
+/**
+ * 	sdev_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:
+	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 user issued commands.
+ *	@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 special requests will be accepted, all others will
+ *	be deferred.  Since special requests may also be requeued requests,
+ *	a successful return doesn't guarantee the device will be 
+ *	totally quiescent.
+ *
+ *	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)
+{
+	int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
+	if (err)
+		return err;
+
+	scsi_run_queue(sdev->request_queue);
+	while (atomic_read(&sdev->device_busy)) {
+		msleep_interruptible(200);
+		scsi_run_queue(sdev->request_queue);
+	}
+	return 0;
+}
+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)
+	 */
+	if (sdev->sdev_state != SDEV_QUIESCE ||
+	    scsi_device_set_state(sdev, SDEV_RUNNING))
+		return;
+	scsi_run_queue(sdev->request_queue);
+}
+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);
+
+/**
+ * scsi_internal_device_block - internal function to put a device temporarily into the SDEV_BLOCK state
+ * @sdev:	device to block
+ *
+ * Block request made by scsi lld's to temporarily stop all
+ * scsi commands on the specified device.  Called from interrupt
+ * or normal process context.
+ *
+ * Returns zero if successful or error if not
+ *
+ * Notes:       
+ *	This routine transitions the device to the SDEV_BLOCK state
+ *	(which must be a legal transition).  When the device is in this
+ *	state, all commands are deferred until the scsi lld reenables
+ *	the device with scsi_device_unblock or device_block_tmo fires.
+ */
+int
+scsi_internal_device_block(struct scsi_device *sdev)
+{
+	struct request_queue *q = sdev->request_queue;
+	unsigned long flags;
+	int err = 0;
+
+	err = scsi_device_set_state(sdev, SDEV_BLOCK);
+	if (err) {
+		err = scsi_device_set_state(sdev, SDEV_CREATED_BLOCK);
+
+		if (err)
+			return err;
+	}
+
+	/* 
+	 * The device has transitioned to SDEV_BLOCK.  Stop the
+	 * block layer from calling the midlayer with this device's
+	 * request queue. 
+	 */
+	if (q->mq_ops) {
+		blk_mq_stop_hw_queues(q);
+	} else {
+		spin_lock_irqsave(q->queue_lock, flags);
+		blk_stop_queue(q);
+		spin_unlock_irqrestore(q->queue_lock, flags);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(scsi_internal_device_block);
+ 
+/**
+ * scsi_internal_device_unblock - resume a device after a block request
+ * @sdev:	device to resume
+ * @new_state:	state to set devices to after unblocking
+ *
+ * Called by scsi lld's or the midlayer to restart the device queue
+ * for the previously suspended scsi device.  Called from interrupt or
+ * normal process context.
+ *
+ * Returns zero if successful or error if not.
+ *
+ * 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(struct scsi_device *sdev,
+			     enum scsi_device_state new_state)
+{
+	struct request_queue *q = sdev->request_queue; 
+	unsigned long flags;
+
+	/*
+	 * Try to transition the scsi device to SDEV_RUNNING or one of the
+	 * offlined states and goose the device queue if successful.
+	 */
+	if ((sdev->sdev_state == SDEV_BLOCK) ||
+	    (sdev->sdev_state == SDEV_TRANSPORT_OFFLINE))
+		sdev->sdev_state = new_state;
+	else if (sdev->sdev_state == SDEV_CREATED_BLOCK) {
+		if (new_state == SDEV_TRANSPORT_OFFLINE ||
+		    new_state == SDEV_OFFLINE)
+			sdev->sdev_state = new_state;
+		else
+			sdev->sdev_state = SDEV_CREATED;
+	} else if (sdev->sdev_state != SDEV_CANCEL &&
+		 sdev->sdev_state != SDEV_OFFLINE)
+		return -EINVAL;
+
+	if (q->mq_ops) {
+		blk_mq_start_stopped_hw_queues(q, false);
+	} else {
+		spin_lock_irqsave(q->queue_lock, flags);
+		blk_start_queue(q);
+		spin_unlock_irqrestore(q->queue_lock, flags);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
+
+static void
+device_block(struct scsi_device *sdev, void *data)
+{
+	scsi_internal_device_block(sdev);
+}
+
+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);
+
+/**
+ * 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);