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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  scsi.c Copyright (C) 1992 Drew Eckhardt
  *         Copyright (C) 1993, 1994, 1995, 1999 Eric Youngdale
  *         Copyright (C) 2002, 2003 Christoph Hellwig
  *
  *  generic mid-level SCSI driver
  *      Initial versions: Drew Eckhardt
  *      Subsequent revisions: Eric Youngdale
  *
  *  <drew@colorado.edu>
  *
  *  Bug correction thanks go to :
  *      Rik Faith <faith@cs.unc.edu>
  *      Tommy Thorn <tthorn>
  *      Thomas Wuensche <tw@fgb1.fgb.mw.tu-muenchen.de>
  *
  *  Modified by Eric Youngdale eric@andante.org or ericy@gnu.ai.mit.edu to
  *  add scatter-gather, multiple outstanding request, and other
  *  enhancements.
  *
  *  Native multichannel, wide scsi, /proc/scsi and hot plugging
  *  support added by Michael Neuffer <mike@i-connect.net>
  *
  *  Added request_module("scsi_hostadapter") for kerneld:
  *  (Put an "alias scsi_hostadapter your_hostadapter" in /etc/modprobe.conf)
  *  Bjorn Ekwall  <bj0rn@blox.se>
  *  (changed to kmod)
  *
  *  Major improvements to the timeout, abort, and reset processing,
  *  as well as performance modifications for large queue depths by
  *  Leonard N. Zubkoff <lnz@dandelion.com>
  *
  *  Converted cli() code to spinlocks, Ingo Molnar
  *
  *  Jiffies wrap fixes (host->resetting), 3 Dec 1998 Andrea Arcangeli
  *
  *  out_of_space hacks, D. Gilbert (dpg) 990608
  */
 
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/kernel.h>
 #include <linux/timer.h>
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/blkdev.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/completion.h>
 #include <linux/unistd.h>
 #include <linux/spinlock.h>
 #include <linux/kmod.h>
 #include <linux/interrupt.h>
 #include <linux/notifier.h>
 #include <linux/cpu.h>
 #include <linux/mutex.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_tcq.h>
 
 #include "scsi_priv.h"
 #include "scsi_logging.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/scsi.h>
 
 /*
  * Definitions and constants.
  */
 
 /*
  * Note - the initial logging level can be set here to log events at boot time.
  * After the system is up, you may enable logging via the /proc interface.
  */
 unsigned int scsi_logging_level;
 #if defined(CONFIG_SCSI_LOGGING)
 EXPORT_SYMBOL(scsi_logging_level);
 #endif
 
 #ifdef CONFIG_SCSI_LOGGING
 void scsi_log_send(struct scsi_cmnd *cmd)
 {
     unsigned int level;
 
     /*
      * If ML QUEUE log level is greater than or equal to:
      *
      * 1: nothing (match completion)
      *
      * 2: log opcode + command of all commands + cmd address
      *
      * 3: same as 2
      *
      * 4: same as 3
      */
     if (unlikely(scsi_logging_level)) {
         level = SCSI_LOG_LEVEL(SCSI_LOG_MLQUEUE_SHIFT,
                        SCSI_LOG_MLQUEUE_BITS);
         if (level > 1) {
             scmd_printk(KERN_INFO, cmd,
                     "Send: scmd 0x%p\n", cmd);
             scsi_print_command(cmd);
         }
     }
 }
 
 void scsi_log_completion(struct scsi_cmnd *cmd, int disposition)
 {
     unsigned int level;
 
     /*
      * If ML COMPLETE log level is greater than or equal to:
      *
      * 1: log disposition, result, opcode + command, and conditionally
      * sense data for failures or non SUCCESS dispositions.
      *
      * 2: same as 1 but for all command completions.
      *
      * 3: same as 2
      *
      * 4: same as 3 plus dump extra junk
      */
     if (unlikely(scsi_logging_level)) {
         level = SCSI_LOG_LEVEL(SCSI_LOG_MLCOMPLETE_SHIFT,
                        SCSI_LOG_MLCOMPLETE_BITS);
         if (((level > 0) && (cmd->result || disposition != SUCCESS)) ||
             (level > 1)) {
             scsi_print_result(cmd, "Done", disposition);
             scsi_print_command(cmd);
             if (scsi_status_is_check_condition(cmd->result))
                 scsi_print_sense(cmd);
             if (level > 3)
                 scmd_printk(KERN_INFO, cmd,
                         "scsi host busy %d failed %d\n",
                         scsi_host_busy(cmd->device->host),
                         cmd->device->host->host_failed);
         }
     }
 }
 #endif
 
 /**
  * scsi_finish_command - cleanup and pass command back to upper layer
  * @cmd: the command
  *
  * Description: Pass command off to upper layer for finishing of I/O
  *              request, waking processes that are waiting on results,
  *              etc.
  */
 void scsi_finish_command(struct scsi_cmnd *cmd)
 {
     struct scsi_device *sdev = cmd->device;
     struct scsi_target *starget = scsi_target(sdev);
     struct Scsi_Host *shost = sdev->host;
     struct scsi_driver *drv;
     unsigned int good_bytes;
 
     scsi_device_unbusy(sdev, cmd);
 
     /*
      * Clear the flags that say that the device/target/host is no longer
      * capable of accepting new commands.
      */
     if (atomic_read(&shost->host_blocked))
         atomic_set(&shost->host_blocked, 0);
     if (atomic_read(&starget->target_blocked))
         atomic_set(&starget->target_blocked, 0);
     if (atomic_read(&sdev->device_blocked))
         atomic_set(&sdev->device_blocked, 0);
 
     SCSI_LOG_MLCOMPLETE(4, sdev_printk(KERN_INFO, sdev,
                 "Notifying upper driver of completion "
                 "(result %x)\n", cmd->result));
 
     good_bytes = scsi_bufflen(cmd);
     if (!blk_rq_is_passthrough(scsi_cmd_to_rq(cmd))) {
         int old_good_bytes = good_bytes;
         drv = scsi_cmd_to_driver(cmd);
         if (drv->done)
             good_bytes = drv->done(cmd);
         /*
          * USB may not give sense identifying bad sector and
          * simply return a residue instead, so subtract off the
          * residue if drv->done() error processing indicates no
          * change to the completion length.
          */
         if (good_bytes == old_good_bytes)
             good_bytes -= scsi_get_resid(cmd);
     }
     scsi_io_completion(cmd, good_bytes);
 }
 
 
 /*
  * 4096 is big enough for saturating fast SCSI LUNs.
  */
 int scsi_device_max_queue_depth(struct scsi_device *sdev)
 {
     return min_t(int, sdev->host->can_queue, 4096);
 }
 
 /**
  * scsi_change_queue_depth - change a device's queue depth
  * @sdev: SCSI Device in question
  * @depth: number of commands allowed to be queued to the driver
  *
  * Sets the device queue depth and returns the new value.
  */
 int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
 {
     depth = min_t(int, depth, scsi_device_max_queue_depth(sdev));
 
     if (depth > 0) {
         sdev->queue_depth = depth;
         wmb();
     }
 
     if (sdev->request_queue)
         blk_set_queue_depth(sdev->request_queue, depth);
 
     sbitmap_resize(&sdev->budget_map, sdev->queue_depth);
 
     return sdev->queue_depth;
 }
 EXPORT_SYMBOL(scsi_change_queue_depth);
 
 /**
  * scsi_track_queue_full - track QUEUE_FULL events to adjust queue depth
  * @sdev: SCSI Device in question
  * @depth: Current number of outstanding SCSI commands on this device,
  *         not counting the one returned as QUEUE_FULL.
  *
  * Description: This function will track successive QUEUE_FULL events on a
  *      specific SCSI device to determine if and when there is a
  *      need to adjust the queue depth on the device.
  *
  * Returns: 0 - No change needed, >0 - Adjust queue depth to this new depth,
  *      -1 - Drop back to untagged operation using host->cmd_per_lun
  *          as the untagged command depth
  *
  * Lock Status: None held on entry
  *
  * Notes:   Low level drivers may call this at any time and we will do
  *      "The Right Thing."  We are interrupt context safe.
  */
 int scsi_track_queue_full(struct scsi_device *sdev, int depth)
 {
 
     /*
      * Don't let QUEUE_FULLs on the same
      * jiffies count, they could all be from
      * same event.
      */
     if ((jiffies >> 4) == (sdev->last_queue_full_time >> 4))
         return 0;
 
     sdev->last_queue_full_time = jiffies;
     if (sdev->last_queue_full_depth != depth) {
         sdev->last_queue_full_count = 1;
         sdev->last_queue_full_depth = depth;
     } else {
         sdev->last_queue_full_count++;
     }
 
     if (sdev->last_queue_full_count <= 10)
         return 0;
 
     return scsi_change_queue_depth(sdev, depth);
 }
 EXPORT_SYMBOL(scsi_track_queue_full);
 
 /**
  * scsi_vpd_inquiry - Request a device provide us with a VPD page
  * @sdev: The device to ask
  * @buffer: Where to put the result
  * @page: Which Vital Product Data to return
  * @len: The length of the buffer
  *
  * This is an internal helper function.  You probably want to use
  * scsi_get_vpd_page instead.
  *
  * Returns size of the vpd page on success or a negative error number.
  */
 static int scsi_vpd_inquiry(struct scsi_device *sdev, unsigned char *buffer,
                             u8 page, unsigned len)
 {
     int result;
     unsigned char cmd[16];
 
     if (len < 4)
         return -EINVAL;
 
     cmd[0] = INQUIRY;
     cmd[1] = 1;     /* EVPD */
     cmd[2] = page;
     cmd[3] = len >> 8;
     cmd[4] = len & 0xff;
     cmd[5] = 0;     /* Control byte */
 
     /*
      * I'm not convinced we need to try quite this hard to get VPD, but
      * all the existing users tried this hard.
      */
     result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer,
                   len, NULL, 30 * HZ, 3, NULL);
     if (result)
         return -EIO;
 
     /* Sanity check that we got the page back that we asked for */
     if (buffer[1] != page)
         return -EIO;
 
     return get_unaligned_be16(&buffer[2]) + 4;
 }
 
 static int scsi_get_vpd_size(struct scsi_device *sdev, u8 page)
 {
     unsigned char vpd_header[SCSI_VPD_HEADER_SIZE] __aligned(4);
     int result;
 
     /*
      * Fetch the VPD page header to find out how big the page
      * is. This is done to prevent problems on legacy devices
      * which can not handle allocation lengths as large as
      * potentially requested by the caller.
      */
     result = scsi_vpd_inquiry(sdev, vpd_header, page, sizeof(vpd_header));
     if (result < 0)
         return 0;
 
     if (result < SCSI_VPD_HEADER_SIZE) {
         dev_warn_once(&sdev->sdev_gendev,
                   "%s: short VPD page 0x%02x length: %d bytes\n",
                   __func__, page, result);
         return 0;
     }
 
     return result;
 }
 
 /**
  * scsi_get_vpd_page - Get Vital Product Data from a SCSI device
  * @sdev: The device to ask
  * @page: Which Vital Product Data to return
  * @buf: where to store the VPD
  * @buf_len: number of bytes in the VPD buffer area
  *
  * SCSI devices may optionally supply Vital Product Data.  Each 'page'
  * of VPD is defined in the appropriate SCSI document (eg SPC, SBC).
  * If the device supports this VPD page, this routine fills @buf
  * with the data from that page and return 0. If the VPD page is not
  * supported or its content cannot be retrieved, -EINVAL is returned.
  */
 int scsi_get_vpd_page(struct scsi_device *sdev, u8 page, unsigned char *buf,
               int buf_len)
 {
     int result, vpd_len;
 
     if (!scsi_device_supports_vpd(sdev))
         return -EINVAL;
 
     vpd_len = scsi_get_vpd_size(sdev, page);
     if (vpd_len <= 0)
         return -EINVAL;
 
     vpd_len = min(vpd_len, buf_len);
 
     /*
      * Fetch the actual page. Since the appropriate size was reported
      * by the device it is now safe to ask for something bigger.
      */
     memset(buf, 0, buf_len);
     result = scsi_vpd_inquiry(sdev, buf, page, vpd_len);
     if (result < 0)
         return -EINVAL;
     else if (result > vpd_len)
         dev_warn_once(&sdev->sdev_gendev,
                   "%s: VPD page 0x%02x result %d > %d bytes\n",
                   __func__, page, result, vpd_len);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(scsi_get_vpd_page);
 
 /**
  * scsi_get_vpd_buf - Get Vital Product Data from a SCSI device
  * @sdev: The device to ask
  * @page: Which Vital Product Data to return
  *
  * Returns %NULL upon failure.
  */
 static struct scsi_vpd *scsi_get_vpd_buf(struct scsi_device *sdev, u8 page)
 {
     struct scsi_vpd *vpd_buf;
     int vpd_len, result;
 
     vpd_len = scsi_get_vpd_size(sdev, page);
     if (vpd_len <= 0)
         return NULL;
 
 retry_pg:
     /*
      * Fetch the actual page. Since the appropriate size was reported
      * by the device it is now safe to ask for something bigger.
      */
     vpd_buf = kmalloc(sizeof(*vpd_buf) + vpd_len, GFP_KERNEL);
     if (!vpd_buf)
         return NULL;
 
     result = scsi_vpd_inquiry(sdev, vpd_buf->data, page, vpd_len);
     if (result < 0) {
         kfree(vpd_buf);
         return NULL;
     }
     if (result > vpd_len) {
         dev_warn_once(&sdev->sdev_gendev,
                   "%s: VPD page 0x%02x result %d > %d bytes\n",
                   __func__, page, result, vpd_len);
         vpd_len = result;
         kfree(vpd_buf);
         goto retry_pg;
     }
 
     vpd_buf->len = result;
 
     return vpd_buf;
 }
 
 static void scsi_update_vpd_page(struct scsi_device *sdev, u8 page,
                  struct scsi_vpd __rcu **sdev_vpd_buf)
 {
     struct scsi_vpd *vpd_buf;
 
     vpd_buf = scsi_get_vpd_buf(sdev, page);
     if (!vpd_buf)
         return;
 
     mutex_lock(&sdev->inquiry_mutex);
     vpd_buf = rcu_replace_pointer(*sdev_vpd_buf, vpd_buf,
                       lockdep_is_held(&sdev->inquiry_mutex));
     mutex_unlock(&sdev->inquiry_mutex);
 
     if (vpd_buf)
         kfree_rcu(vpd_buf, rcu);
 }
 
 /**
  * scsi_attach_vpd - Attach Vital Product Data to a SCSI device structure
  * @sdev: The device to ask
  *
  * Attach the 'Device Identification' VPD page (0x83) and the
  * 'Unit Serial Number' VPD page (0x80) to a SCSI device
  * structure. This information can be used to identify the device
  * uniquely.
  */
 void scsi_attach_vpd(struct scsi_device *sdev)
 {
     int i;
     struct scsi_vpd *vpd_buf;
 
     if (!scsi_device_supports_vpd(sdev))
         return;
 
     /* Ask for all the pages supported by this device */
     vpd_buf = scsi_get_vpd_buf(sdev, 0);
     if (!vpd_buf)
         return;
 
     for (i = 4; i < vpd_buf->len; i++) {
         if (vpd_buf->data[i] == 0x0)
             scsi_update_vpd_page(sdev, 0x0, &sdev->vpd_pg0);
         if (vpd_buf->data[i] == 0x80)
             scsi_update_vpd_page(sdev, 0x80, &sdev->vpd_pg80);
         if (vpd_buf->data[i] == 0x83)
             scsi_update_vpd_page(sdev, 0x83, &sdev->vpd_pg83);
         if (vpd_buf->data[i] == 0x89)
             scsi_update_vpd_page(sdev, 0x89, &sdev->vpd_pg89);
         if (vpd_buf->data[i] == 0xb0)
             scsi_update_vpd_page(sdev, 0xb0, &sdev->vpd_pgb0);
         if (vpd_buf->data[i] == 0xb1)
             scsi_update_vpd_page(sdev, 0xb1, &sdev->vpd_pgb1);
         if (vpd_buf->data[i] == 0xb2)
             scsi_update_vpd_page(sdev, 0xb2, &sdev->vpd_pgb2);
     }
     kfree(vpd_buf);
 }
 
 /**
  * scsi_report_opcode - Find out if a given command opcode is supported
  * @sdev:   scsi device to query
  * @buffer: scratch buffer (must be at least 20 bytes long)
  * @len:    length of buffer
  * @opcode: opcode for command to look up
  *
  * Uses the REPORT SUPPORTED OPERATION CODES to look up the given
  * opcode. Returns -EINVAL if RSOC fails, 0 if the command opcode is
  * unsupported and 1 if the device claims to support the command.
  */
 int scsi_report_opcode(struct scsi_device *sdev, unsigned char *buffer,
                unsigned int len, unsigned char opcode)
 {
     unsigned char cmd[16];
     struct scsi_sense_hdr sshdr;
     int result, request_len;
 
     if (sdev->no_report_opcodes || sdev->scsi_level < SCSI_SPC_3)
         return -EINVAL;
 
     /* RSOC header + size of command we are asking about */
     request_len = 4 + COMMAND_SIZE(opcode);
     if (request_len > len) {
         dev_warn_once(&sdev->sdev_gendev,
                   "%s: len %u bytes, opcode 0x%02x needs %u\n",
                   __func__, len, opcode, request_len);
         return -EINVAL;
     }
 
     memset(cmd, 0, 16);
     cmd[0] = MAINTENANCE_IN;
     cmd[1] = MI_REPORT_SUPPORTED_OPERATION_CODES;
     cmd[2] = 1;     /* One command format */
     cmd[3] = opcode;
     put_unaligned_be32(request_len, &cmd[6]);
     memset(buffer, 0, len);
 
     result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer,
                   request_len, &sshdr, 30 * HZ, 3, NULL);
 
     if (result < 0)
         return result;
     if (result && scsi_sense_valid(&sshdr) &&
         sshdr.sense_key == ILLEGAL_REQUEST &&
         (sshdr.asc == 0x20 || sshdr.asc == 0x24) && sshdr.ascq == 0x00)
         return -EINVAL;
 
     if ((buffer[1] & 3) == 3) /* Command supported */
         return 1;
 
     return 0;
 }
 EXPORT_SYMBOL(scsi_report_opcode);
 
 /**
  * scsi_device_get  -  get an additional reference to a scsi_device
  * @sdev:   device to get a reference to
  *
  * Description: Gets a reference to the scsi_device and increments the use count
  * of the underlying LLDD module.  You must hold host_lock of the
  * parent Scsi_Host or already have a reference when calling this.
  *
  * This will fail if a device is deleted or cancelled, or when the LLD module
  * is in the process of being unloaded.
  */
 int scsi_device_get(struct scsi_device *sdev)
 {
     if (sdev->sdev_state == SDEV_DEL || sdev->sdev_state == SDEV_CANCEL)
         goto fail;
     if (!get_device(&sdev->sdev_gendev))
         goto fail;
     if (!try_module_get(sdev->host->hostt->module))
         goto fail_put_device;
     return 0;
 
 fail_put_device:
     put_device(&sdev->sdev_gendev);
 fail:
     return -ENXIO;
 }
 EXPORT_SYMBOL(scsi_device_get);
 
 /**
  * scsi_device_put  -  release a reference to a scsi_device
  * @sdev:   device to release a reference on.
  *
  * Description: Release a reference to the scsi_device and decrements the use
  * count of the underlying LLDD module.  The device is freed once the last
  * user vanishes.
  */
 void scsi_device_put(struct scsi_device *sdev)
 {
     struct module *mod = sdev->host->hostt->module;
 
     put_device(&sdev->sdev_gendev);
     module_put(mod);
 }
 EXPORT_SYMBOL(scsi_device_put);
 
 /* helper for shost_for_each_device, see that for documentation */
 struct scsi_device *__scsi_iterate_devices(struct Scsi_Host *shost,
                        struct scsi_device *prev)
 {
     struct list_head *list = (prev ? &prev->siblings : &shost->__devices);
     struct scsi_device *next = NULL;
     unsigned long flags;
 
     spin_lock_irqsave(shost->host_lock, flags);
     while (list->next != &shost->__devices) {
         next = list_entry(list->next, struct scsi_device, siblings);
         /* skip devices that we can't get a reference to */
         if (!scsi_device_get(next))
             break;
         next = NULL;
         list = list->next;
     }
     spin_unlock_irqrestore(shost->host_lock, flags);
 
     if (prev)
         scsi_device_put(prev);
     return next;
 }
 EXPORT_SYMBOL(__scsi_iterate_devices);
 
 /**
  * starget_for_each_device  -  helper to walk all devices of a target
  * @starget:    target whose devices we want to iterate over.
  * @data:   Opaque passed to each function call.
  * @fn:     Function to call on each device
  *
  * This traverses over each device of @starget.  The devices have
  * a reference that must be released by scsi_host_put when breaking
  * out of the loop.
  */
 void starget_for_each_device(struct scsi_target *starget, void *data,
              void (*fn)(struct scsi_device *, void *))
 {
     struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
     struct scsi_device *sdev;
 
     shost_for_each_device(sdev, shost) {
         if ((sdev->channel == starget->channel) &&
             (sdev->id == starget->id))
             fn(sdev, data);
     }
 }
 EXPORT_SYMBOL(starget_for_each_device);
 
 /**
  * __starget_for_each_device - helper to walk all devices of a target (UNLOCKED)
  * @starget:    target whose devices we want to iterate over.
  * @data:   parameter for callback @fn()
  * @fn:     callback function that is invoked for each device
  *
  * This traverses over each device of @starget.  It does _not_
  * take a reference on the scsi_device, so the whole loop must be
  * protected by shost->host_lock.
  *
  * Note:  The only reason why drivers would want to use this is because
  * they need to access the device list in irq context.  Otherwise you
  * really want to use starget_for_each_device instead.
  **/
 void __starget_for_each_device(struct scsi_target *starget, void *data,
                    void (*fn)(struct scsi_device *, void *))
 {
     struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
     struct scsi_device *sdev;
 
     __shost_for_each_device(sdev, shost) {
         if ((sdev->channel == starget->channel) &&
             (sdev->id == starget->id))
             fn(sdev, data);
     }
 }
 EXPORT_SYMBOL(__starget_for_each_device);
 
 /**
  * __scsi_device_lookup_by_target - find a device given the target (UNLOCKED)
  * @starget:    SCSI target pointer
  * @lun:    SCSI Logical Unit Number
  *
  * Description: Looks up the scsi_device with the specified @lun for a given
  * @starget.  The returned scsi_device does not have an additional
  * reference.  You must hold the host's host_lock over this call and
  * any access to the returned scsi_device. A scsi_device in state
  * SDEV_DEL is skipped.
  *
  * Note:  The only reason why drivers should use this is because
  * they need to access the device list in irq context.  Otherwise you
  * really want to use scsi_device_lookup_by_target instead.
  **/
 struct scsi_device *__scsi_device_lookup_by_target(struct scsi_target *starget,
                            u64 lun)
 {
     struct scsi_device *sdev;
 
     list_for_each_entry(sdev, &starget->devices, same_target_siblings) {
         if (sdev->sdev_state == SDEV_DEL)
             continue;
         if (sdev->lun ==lun)
             return sdev;
     }
 
     return NULL;
 }
 EXPORT_SYMBOL(__scsi_device_lookup_by_target);
 
 /**
  * scsi_device_lookup_by_target - find a device given the target
  * @starget:    SCSI target pointer
  * @lun:    SCSI Logical Unit Number
  *
  * Description: Looks up the scsi_device with the specified @lun for a given
  * @starget.  The returned scsi_device has an additional reference that
  * needs to be released with scsi_device_put once you're done with it.
  **/
 struct scsi_device *scsi_device_lookup_by_target(struct scsi_target *starget,
                          u64 lun)
 {
     struct scsi_device *sdev;
     struct Scsi_Host *shost = dev_to_shost(starget->dev.parent);
     unsigned long flags;
 
     spin_lock_irqsave(shost->host_lock, flags);
     sdev = __scsi_device_lookup_by_target(starget, lun);
     if (sdev && scsi_device_get(sdev))
         sdev = NULL;
     spin_unlock_irqrestore(shost->host_lock, flags);
 
     return sdev;
 }
 EXPORT_SYMBOL(scsi_device_lookup_by_target);
 
 /**
  * __scsi_device_lookup - find a device given the host (UNLOCKED)
  * @shost:  SCSI host pointer
  * @channel:    SCSI channel (zero if only one channel)
  * @id:     SCSI target number (physical unit number)
  * @lun:    SCSI Logical Unit Number
  *
  * Description: Looks up the scsi_device with the specified @channel, @id, @lun
  * for a given host. The returned scsi_device does not have an additional
  * reference.  You must hold the host's host_lock over this call and any access
  * to the returned scsi_device.
  *
  * Note:  The only reason why drivers would want to use this is because
  * they need to access the device list in irq context.  Otherwise you
  * really want to use scsi_device_lookup instead.
  **/
 struct scsi_device *__scsi_device_lookup(struct Scsi_Host *shost,
         uint channel, uint id, u64 lun)
 {
     struct scsi_device *sdev;
 
     list_for_each_entry(sdev, &shost->__devices, siblings) {
         if (sdev->sdev_state == SDEV_DEL)
             continue;
         if (sdev->channel == channel && sdev->id == id &&
                 sdev->lun ==lun)
             return sdev;
     }
 
     return NULL;
 }
 EXPORT_SYMBOL(__scsi_device_lookup);
 
 /**
  * scsi_device_lookup - find a device given the host
  * @shost:  SCSI host pointer
  * @channel:    SCSI channel (zero if only one channel)
  * @id:     SCSI target number (physical unit number)
  * @lun:    SCSI Logical Unit Number
  *
  * Description: Looks up the scsi_device with the specified @channel, @id, @lun
  * for a given host.  The returned scsi_device has an additional reference that
  * needs to be released with scsi_device_put once you're done with it.
  **/
 struct scsi_device *scsi_device_lookup(struct Scsi_Host *shost,
         uint channel, uint id, u64 lun)
 {
     struct scsi_device *sdev;
     unsigned long flags;
 
     spin_lock_irqsave(shost->host_lock, flags);
     sdev = __scsi_device_lookup(shost, channel, id, lun);
     if (sdev && scsi_device_get(sdev))
         sdev = NULL;
     spin_unlock_irqrestore(shost->host_lock, flags);
 
     return sdev;
 }
 EXPORT_SYMBOL(scsi_device_lookup);
 
 MODULE_DESCRIPTION("SCSI core");
 MODULE_LICENSE("GPL");
 
 module_param(scsi_logging_level, int, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(scsi_logging_level, "a bit mask of logging levels");
 
 static int __init init_scsi(void)
 {
     int error;
 
     error = scsi_init_procfs();
     if (error)
         goto cleanup_queue;
     error = scsi_init_devinfo();
     if (error)
         goto cleanup_procfs;
     error = scsi_init_hosts();
     if (error)
         goto cleanup_devlist;
     error = scsi_init_sysctl();
     if (error)
         goto cleanup_hosts;
     error = scsi_sysfs_register();
     if (error)
         goto cleanup_sysctl;
 
     scsi_netlink_init();
 
     printk(KERN_NOTICE "SCSI subsystem initialized\n");
     return 0;
 
 cleanup_sysctl:
     scsi_exit_sysctl();
 cleanup_hosts:
     scsi_exit_hosts();
 cleanup_devlist:
     scsi_exit_devinfo();
 cleanup_procfs:
     scsi_exit_procfs();
 cleanup_queue:
     scsi_exit_queue();
     printk(KERN_ERR "SCSI subsystem failed to initialize, error = %d\n",
            -error);
     return error;
 }
 
 static void __exit exit_scsi(void)
 {
     scsi_netlink_exit();
     scsi_sysfs_unregister();
     scsi_exit_sysctl();
     scsi_exit_hosts();
     scsi_exit_devinfo();
     scsi_exit_procfs();
     scsi_exit_queue();
 }
 
 subsys_initcall(init_scsi);
 module_exit(exit_scsi);

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