Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3337 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
new file mode 100644
index 0000000000..c2f647a7c1
--- /dev/null
+++ b/drivers/scsi/scsi_lib.c
@@ -0,0 +1,3337 @@
+// 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);
+	}
+
+	blk_mq_requeue_request(rq, false);
+	if (!scsi_host_in_recovery(cmd->device->host))
+		blk_mq_delay_kick_requeue_list(rq->q, msecs);
+}
+
+/**
+ * __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),
+			       !scsi_host_in_recovery(cmd->device->host));
+}
+
+/**
+ * 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_cmd - insert request and wait for the result
+ * @sdev:	scsi_device
+ * @cmd:	scsi command
+ * @opf:	block layer request cmd_flags
+ * @buffer:	data buffer
+ * @bufflen:	len of buffer
+ * @timeout:	request timeout in HZ
+ * @retries:	number of times to retry request
+ * @args:	Optional args. See struct definition for field descriptions
+ *
+ * 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_cmd(struct scsi_device *sdev, const unsigned char *cmd,
+		     blk_opf_t opf, void *buffer, unsigned int bufflen,
+		     int timeout, int retries,
+		     const struct scsi_exec_args *args)
+{
+	static const struct scsi_exec_args default_args;
+	struct request *req;
+	struct scsi_cmnd *scmd;
+	int ret;
+
+	if (!args)
+		args = &default_args;
+	else if (WARN_ON_ONCE(args->sense &&
+			      args->sense_len != SCSI_SENSE_BUFFERSIZE))
+		return -EINVAL;
+
+	req = scsi_alloc_request(sdev->request_queue, opf, args->req_flags);
+	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;
+	scmd->flags |= args->scmd_flags;
+	req->timeout = timeout;
+	req->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 (args->resid)
+		*args->resid = scmd->resid_len;
+	if (args->sense)
+		memcpy(args->sense, scmd->sense_buffer, SCSI_SENSE_BUFFERSIZE);
+	if (args->sshdr)
+		scsi_normalize_sense(scmd->sense_buffer, scmd->sense_len,
+				     args->sshdr);
+
+	ret = scmd->result;
+ out:
+	blk_mq_free_request(req);
+
+	return ret;
+}
+EXPORT_SYMBOL(scsi_execute_cmd);
+
+/*
+ * 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;
+}
+
+/*
+ * Kick the queue of SCSI device @sdev if @sdev != current_sdev. Called with
+ * interrupts disabled.
+ */
+static void scsi_kick_sdev_queue(struct scsi_device *sdev, void *data)
+{
+	struct scsi_device *current_sdev = data;
+
+	if (sdev != current_sdev)
+		blk_mq_run_hw_queues(sdev->request_queue, true);
+}
+
+/*
+ * 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_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.
+	 */
+	blk_mq_run_hw_queues(current_sdev->request_queue,
+			     shost->queuecommand_may_block);
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	if (!starget->starget_sdev_user)
+		__starget_for_each_device(starget, current_sdev,
+					  scsi_kick_sdev_queue);
+	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);
+
+		blk_mq_run_hw_queues(slq, false);
+		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);
+
+	/* Note: blk_mq_kick_requeue_list() runs the queue asynchronously. */
+	blk_mq_kick_requeue_list(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);
+}
+
+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_host_in_recovery(sdev->host))
+		return;
+
+	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
+ * @result:	scsi error code
+ *
+ * Translate a SCSI result code into a blk_status_t value.
+ */
+static blk_status_t scsi_result_to_blk_status(int result)
+{
+	/*
+	 * Check the scsi-ml byte first in case we converted a host or status
+	 * byte.
+	 */
+	switch (scsi_ml_byte(result)) {
+	case SCSIML_STAT_OK:
+		break;
+	case SCSIML_STAT_RESV_CONFLICT:
+		return BLK_STS_RESV_CONFLICT;
+	case SCSIML_STAT_NOSPC:
+		return BLK_STS_NOSPC;
+	case SCSIML_STAT_MED_ERROR:
+		return BLK_STS_MEDIUM;
+	case SCSIML_STAT_TGT_FAILURE:
+		return BLK_STS_TARGET;
+	case SCSIML_STAT_DL_TIMEOUT:
+		return BLK_STS_DURATION_LIMIT;
+	}
+
+	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;
+	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(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;
+		case COMPLETED:
+			fallthrough;
+		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(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(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 (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"));
+		atomic_dec(&cmd->device->iorequest_cnt);
+		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) {
+		atomic_dec(&cmd->device->iorequest_cnt);
+		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 (unlikely(scsi_host_in_recovery(shost))) {
+		if (cmd->flags & SCMD_FAIL_IF_RECOVERING)
+			ret = BLK_STS_OFFLINE;
+		goto out_dec_target_busy;
+	}
+	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 void 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);
+	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);
+	if (shost->queuecommand_may_block)
+		tag_set->flags |= BLK_MQ_F_BLOCKING;
+	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;
+	const struct scsi_exec_args exec_args = {
+		.sshdr = sshdr,
+	};
+	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_cmd(sdev, cmd, REQ_OP_DRV_OUT, real_buffer, len,
+			       timeout, retries, &exec_args);
+	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
+ *	@subpage: sub-page of the 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, int subpage,
+		  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;
+	const struct scsi_exec_args exec_args = {
+		/* caller might not be interested in sense, but we need it */
+		.sshdr = sshdr ? : &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;
+	cmd[3] = subpage;
+
+	sshdr = exec_args.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_cmd(sdev, cmd, REQ_OP_DRV_IN, buffer, len,
+				  timeout, retries, &exec_args);
+	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,
+	};
+	const struct scsi_exec_args exec_args = {
+		.sshdr = sshdr,
+	};
+	int result;
+
+	/* try to eat the UNIT_ATTENTION if there are enough retries */
+	do {
+		result = scsi_execute_cmd(sdev, cmd, REQ_OP_DRV_IN, NULL, 0,
+					  timeout, 1, &exec_args);
+		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);
+		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)
+{
+	/*
+	 * The atomic variable of ->queue_stopped covers that
+	 * blk_mq_quiesce_queue* is balanced with blk_mq_unquiesce_queue.
+	 *
+	 * The caller needs to wait until quiesce is done.
+	 */
+	if (!cmpxchg(&sdev->queue_stopped, 0, 1))
+		blk_mq_quiesce_queue_nowait(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);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
+
+/**
+ * scsi_device_block - try to transition to the SDEV_BLOCK state
+ * @sdev: device to block
+ * @data: dummy argument, ignored
+ *
+ * Pause SCSI command processing on the specified device. Callers must wait
+ * until all ongoing scsi_queue_rq() calls have finished after this function
+ * returns.
+ *
+ * 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 void scsi_device_block(struct scsi_device *sdev, void *data)
+{
+	int err;
+	enum scsi_device_state state;
+
+	mutex_lock(&sdev->state_mutex);
+	err = __scsi_internal_device_block_nowait(sdev);
+	state = sdev->sdev_state;
+	if (err == 0)
+		/*
+		 * scsi_stop_queue() must be called with the state_mutex
+		 * held. Otherwise a simultaneous scsi_start_queue() call
+		 * might unquiesce the queue before we quiesce it.
+		 */
+		scsi_stop_queue(sdev);
+
+	mutex_unlock(&sdev->state_mutex);
+
+	WARN_ONCE(err, "%s: failed to block %s in state %d\n",
+		  __func__, dev_name(&sdev->sdev_gendev), state);
+}
+
+/**
+ * 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 int
+target_block(struct device *dev, void *data)
+{
+	if (scsi_is_target_device(dev))
+		starget_for_each_device(to_scsi_target(dev), NULL,
+					scsi_device_block);
+	return 0;
+}
+
+/**
+ * scsi_block_targets - transition all SCSI child devices to SDEV_BLOCK state
+ * @dev: a parent device of one or more scsi_target devices
+ * @shost: the Scsi_Host to which this device belongs
+ *
+ * Iterate over all children of @dev, which should be scsi_target devices,
+ * and switch all subordinate scsi devices to SDEV_BLOCK state. Wait for
+ * ongoing scsi_queue_rq() calls to finish. May sleep.
+ *
+ * Note:
+ * @dev must not itself be a scsi_target device.
+ */
+void
+scsi_block_targets(struct Scsi_Host *shost, struct device *dev)
+{
+	WARN_ON_ONCE(scsi_is_target_device(dev));
+	device_for_each_child(dev, NULL, target_block);
+	blk_mq_wait_quiesce_done(&shost->tag_set);
+}
+EXPORT_SYMBOL_GPL(scsi_block_targets);
+
+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_host_block - Try to transition all logical units to the SDEV_BLOCK state
+ * @shost: device to block
+ *
+ * Pause SCSI command processing for all logical units associated with the SCSI
+ * host and wait until pending scsi_queue_rq() calls have finished.
+ *
+ * Returns zero if successful or a negative error code upon failure.
+ */
+int
+scsi_host_block(struct Scsi_Host *shost)
+{
+	struct scsi_device *sdev;
+	int ret;
+
+	/*
+	 * 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);
+			return ret;
+		}
+	}
+
+	/* Wait for ongoing scsi_queue_rq() calls to finish. */
+	blk_mq_wait_quiesce_done(&shost->tag_set);
+
+	return 0;
+}
+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);