/*
   *  History:
   *  Started: Aug 9 by Lawrence Foard (entropy@world.std.com),
   *           to allow user process control of SCSI devices.
   *  Development Sponsored by Killy Corp. NY NY
   *
   * Original driver (sg.c):
   *        Copyright (C) 1992 Lawrence Foard
   * Version 2 and 3 extensions to driver:

   *        Copyright (C) 1998 - 2014 Douglas Gilbert

   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2, or (at your option)
   * any later version.
   *
   */

  static int sg_version_num = 30536;	/* 2 digits for each component */
  #define SG_VERSION_STR "3.5.36"

  
  /*

   *  D. P. Gilbert (dgilbert@interlog.com), notes:

   *      - scsi logging is available via SCSI_LOG_TIMEOUT macros. First
   *        the kernel/module needs to be built with CONFIG_SCSI_LOGGING
   *        (otherwise the macros compile to empty statements).
   *
   */

  #include <linux/module.h>
  
  #include <linux/fs.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/string.h>
  #include <linux/mm.h>
  #include <linux/errno.h>
  #include <linux/mtio.h>
  #include <linux/ioctl.h>

  #include <linux/slab.h>

  #include <linux/fcntl.h>
  #include <linux/init.h>
  #include <linux/poll.h>

  #include <linux/moduleparam.h>

  #include <linux/cdev.h>

  #include <linux/idr.h>

  #include <linux/seq_file.h>
  #include <linux/blkdev.h>
  #include <linux/delay.h>

  #include <linux/blktrace_api.h>

  #include <linux/mutex.h>

  #include <linux/atomic.h>

  #include <linux/ratelimit.h>

  #include <linux/uio.h>

  #include <linux/cred.h> /* for sg_check_file_access() */

  
  #include "scsi.h"

  #include <scsi/scsi_dbg.h>

  #include <scsi/scsi_host.h>
  #include <scsi/scsi_driver.h>
  #include <scsi/scsi_ioctl.h>
  #include <scsi/sg.h>
  
  #include "scsi_logging.h"
  
  #ifdef CONFIG_SCSI_PROC_FS
  #include <linux/proc_fs.h>

  static char *sg_version_date = "20140603";

  
  static int sg_proc_init(void);
  static void sg_proc_cleanup(void);
  #endif

  #define SG_ALLOW_DIO_DEF 0

  
  #define SG_MAX_DEVS 32768

  /* SG_MAX_CDB_SIZE should be 260 (spc4r37 section 3.1.30) however the type
   * of sg_io_hdr::cmd_len can only represent 255. All SCSI commands greater
   * than 16 bytes are "variable length" whose length is a multiple of 4
   */
  #define SG_MAX_CDB_SIZE 252

  #define SG_DEFAULT_TIMEOUT mult_frac(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ)

  
  int sg_big_buff = SG_DEF_RESERVED_SIZE;
  /* N.B. This variable is readable and writeable via
     /proc/scsi/sg/def_reserved_size . Each time sg_open() is called a buffer
     of this size (or less if there is not enough memory) will be reserved
     for use by this file descriptor. [Deprecated usage: this variable is also
     readable via /proc/sys/kernel/sg-big-buff if the sg driver is built into
     the kernel (i.e. it is not a module).] */
  static int def_reserved_size = -1;	/* picks up init parameter */
  static int sg_allow_dio = SG_ALLOW_DIO_DEF;

  static int scatter_elem_sz = SG_SCATTER_SZ;
  static int scatter_elem_sz_prev = SG_SCATTER_SZ;

  #define SG_SECTOR_SZ 512

  static int sg_add_device(struct device *, struct class_interface *);
  static void sg_remove_device(struct device *, struct class_interface *);

  static DEFINE_IDR(sg_index_idr);

  static DEFINE_RWLOCK(sg_index_lock);	/* Also used to lock
  							   file descriptor list for device */

  
  static struct class_interface sg_interface = {

  	.add_dev        = sg_add_device,
  	.remove_dev     = sg_remove_device,

  };
  
  typedef struct sg_scatter_hold { /* holding area for scsi scatter gather info */
  	unsigned short k_use_sg; /* Count of kernel scatter-gather pieces */

  	unsigned sglist_len; /* size of malloc'd scatter-gather list ++ */

  	unsigned bufflen;	/* Size of (aggregate) data buffer */

  	struct page **pages;
  	int page_order;

  	char dio_in_use;	/* 0->indirect IO (or mmap), 1->dio */
  	unsigned char cmd_opcode; /* first byte of command */
  } Sg_scatter_hold;
  
  struct sg_device;		/* forward declarations */
  struct sg_fd;
  
  typedef struct sg_request {	/* SG_MAX_QUEUE requests outstanding per file */

  	struct list_head entry;	/* list entry */

  	struct sg_fd *parentfp;	/* NULL -> not in use */
  	Sg_scatter_hold data;	/* hold buffer, perhaps scatter list */
  	sg_io_hdr_t header;	/* scsi command+info, see <scsi/sg.h> */

  	unsigned char sense_b[SCSI_SENSE_BUFFERSIZE];

  	char res_used;		/* 1 -> using reserve buffer, 0 -> not ... */
  	char orphan;		/* 1 -> drop on sight, 0 -> normal */
  	char sg_io_owned;	/* 1 -> packet belongs to SG_IO */

  	/* done protected by rq_list_lock */
  	char done;		/* 0->before bh, 1->before read, 2->read */

  	struct request *rq;

  	struct bio *bio;

  	struct execute_work ew;

  } Sg_request;
  
  typedef struct sg_fd {		/* holds the state of a file descriptor */

  	struct list_head sfd_siblings;  /* protected by device's sfd_lock */

  	struct sg_device *parentdp;	/* owning device */
  	wait_queue_head_t read_wait;	/* queue read until command done */
  	rwlock_t rq_list_lock;	/* protect access to list in req_arr */

  	struct mutex f_mutex;	/* protect against changes in this fd */

  	int timeout;		/* defaults to SG_DEFAULT_TIMEOUT      */
  	int timeout_user;	/* defaults to SG_DEFAULT_TIMEOUT_USER */
  	Sg_scatter_hold reserve;	/* buffer held for this file descriptor */

  	struct list_head rq_list; /* head of request list */

  	struct fasync_struct *async_qp;	/* used by asynchronous notification */
  	Sg_request req_arr[SG_MAX_QUEUE];	/* used as singly-linked list */

  	char force_packid;	/* 1 -> pack_id input to read(), 0 -> ignored */

  	char cmd_q;		/* 1 -> allow command queuing, 0 -> don't */

  	unsigned char next_cmd_len; /* 0: automatic, >0: use on next write() */

  	char keep_orphan;	/* 0 -> drop orphan (def), 1 -> keep for read() */
  	char mmap_called;	/* 0 -> mmap() never called on this fd */

  	char res_in_use;	/* 1 -> 'reserve' array in use */

  	struct kref f_ref;
  	struct execute_work ew;

  } Sg_fd;
  
  typedef struct sg_device { /* holds the state of each scsi generic device */
  	struct scsi_device *device;

  	wait_queue_head_t open_wait;    /* queue open() when O_EXCL present */
  	struct mutex open_rel_lock;     /* held when in open() or release() */

  	int sg_tablesize;	/* adapter's max scatter-gather table size */

  	u32 index;		/* device index number */

  	struct list_head sfds;

  	rwlock_t sfd_lock;      /* protect access to sfd list */
  	atomic_t detaching;     /* 0->device usable, 1->device detaching */
  	bool exclude;		/* 1->open(O_EXCL) succeeded and is active */
  	int open_cnt;		/* count of opens (perhaps < num(sfds) ) */

  	char sgdebug;		/* 0->off, 1->sense, 9->dump dev, 10-> all devs */
  	struct gendisk *disk;
  	struct cdev * cdev;	/* char_dev [sysfs: /sys/cdev/major/sg<n>] */

  	struct kref d_ref;

  } Sg_device;

  /* tasklet or soft irq callback */

  static void sg_rq_end_io(struct request *rq, blk_status_t status);

  static int sg_start_req(Sg_request *srp, unsigned char *cmd);

  static int sg_finish_rem_req(Sg_request * srp);

  static int sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size);

  static ssize_t sg_new_read(Sg_fd * sfp, char __user *buf, size_t count,
  			   Sg_request * srp);

  static ssize_t sg_new_write(Sg_fd *sfp, struct file *file,
  			const char __user *buf, size_t count, int blocking,

  			int read_only, int sg_io_owned, Sg_request **o_srp);

  static int sg_common_write(Sg_fd * sfp, Sg_request * srp,
  			   unsigned char *cmnd, int timeout, int blocking);

  static int sg_read_oxfer(Sg_request * srp, char __user *outp, int num_read_xfer);

  static void sg_remove_scat(Sg_fd * sfp, Sg_scatter_hold * schp);

  static void sg_build_reserve(Sg_fd * sfp, int req_size);
  static void sg_link_reserve(Sg_fd * sfp, Sg_request * srp, int size);
  static void sg_unlink_reserve(Sg_fd * sfp, Sg_request * srp);

  static Sg_fd *sg_add_sfp(Sg_device * sdp);

  static void sg_remove_sfp(struct kref *);

  static Sg_request *sg_get_rq_mark(Sg_fd * sfp, int pack_id);
  static Sg_request *sg_add_request(Sg_fd * sfp);
  static int sg_remove_request(Sg_fd * sfp, Sg_request * srp);

  static Sg_device *sg_get_dev(int dev);

  static void sg_device_destroy(struct kref *kref);

  #define SZ_SG_HEADER sizeof(struct sg_header)
  #define SZ_SG_IO_HDR sizeof(sg_io_hdr_t)
  #define SZ_SG_IOVEC sizeof(sg_iovec_t)
  #define SZ_SG_REQ_INFO sizeof(sg_req_info_t)

  #define sg_printk(prefix, sdp, fmt, a...) \

  	sdev_prefix_printk(prefix, (sdp)->device,		\
  			   (sdp)->disk->disk_name, fmt, ##a)

  /*
   * The SCSI interfaces that use read() and write() as an asynchronous variant of
   * ioctl(..., SG_IO, ...) are fundamentally unsafe, since there are lots of ways
   * to trigger read() and write() calls from various contexts with elevated
   * privileges. This can lead to kernel memory corruption (e.g. if these
   * interfaces are called through splice()) and privilege escalation inside
   * userspace (e.g. if a process with access to such a device passes a file
   * descriptor to a SUID binary as stdin/stdout/stderr).
   *
   * This function provides protection for the legacy API by restricting the
   * calling context.
   */
  static int sg_check_file_access(struct file *filp, const char *caller)
  {
  	if (filp->f_cred != current_real_cred()) {
  		pr_err_once("%s: process %d (%s) changed security contexts after opening file descriptor, this is not allowed.
  ",
  			caller, task_tgid_vnr(current), current->comm);
  		return -EPERM;
  	}
  	if (uaccess_kernel()) {
  		pr_err_once("%s: process %d (%s) called from kernel context, this is not allowed.
  ",
  			caller, task_tgid_vnr(current), current->comm);
  		return -EACCES;
  	}
  	return 0;
  }

  static int sg_allow_access(struct file *filp, unsigned char *cmd)
  {

  	struct sg_fd *sfp = filp->private_data;

  
  	if (sfp->parentdp->device->type == TYPE_SCANNER)
  		return 0;

  	return blk_verify_command(cmd, filp->f_mode & FMODE_WRITE);

  }

  static int
  open_wait(Sg_device *sdp, int flags)

  {

  	int retval = 0;

  	if (flags & O_EXCL) {
  		while (sdp->open_cnt > 0) {
  			mutex_unlock(&sdp->open_rel_lock);
  			retval = wait_event_interruptible(sdp->open_wait,
  					(atomic_read(&sdp->detaching) ||
  					 !sdp->open_cnt));
  			mutex_lock(&sdp->open_rel_lock);
  
  			if (retval) /* -ERESTARTSYS */
  				return retval;
  			if (atomic_read(&sdp->detaching))
  				return -ENODEV;
  		}
  	} else {
  		while (sdp->exclude) {
  			mutex_unlock(&sdp->open_rel_lock);
  			retval = wait_event_interruptible(sdp->open_wait,
  					(atomic_read(&sdp->detaching) ||
  					 !sdp->exclude));
  			mutex_lock(&sdp->open_rel_lock);
  
  			if (retval) /* -ERESTARTSYS */
  				return retval;
  			if (atomic_read(&sdp->detaching))
  				return -ENODEV;
  		}
  	}

  	return retval;

  }

  /* Returns 0 on success, else a negated errno value */

  static int
  sg_open(struct inode *inode, struct file *filp)
  {
  	int dev = iminor(inode);
  	int flags = filp->f_flags;

  	struct request_queue *q;

  	Sg_device *sdp;
  	Sg_fd *sfp;

  	int retval;
  
  	nonseekable_open(inode, filp);

  	if ((flags & O_EXCL) && (O_RDONLY == (flags & O_ACCMODE)))
  		return -EPERM; /* Can't lock it with read only access */

  	sdp = sg_get_dev(dev);

  	if (IS_ERR(sdp))
  		return PTR_ERR(sdp);

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
  				      "sg_open: flags=0x%x
  ", flags));

  	/* This driver's module count bumped by fops_get in <linux/fs.h> */
  	/* Prevent the device driver from vanishing while we sleep */
  	retval = scsi_device_get(sdp->device);

  	if (retval)
  		goto sg_put;

  	retval = scsi_autopm_get_device(sdp->device);
  	if (retval)
  		goto sdp_put;

  	/* scsi_block_when_processing_errors() may block so bypass
  	 * check if O_NONBLOCK. Permits SCSI commands to be issued
  	 * during error recovery. Tread carefully. */

  	if (!((flags & O_NONBLOCK) ||
  	      scsi_block_when_processing_errors(sdp->device))) {
  		retval = -ENXIO;
  		/* we are in error recovery for this device */
  		goto error_out;
  	}

  	mutex_lock(&sdp->open_rel_lock);
  	if (flags & O_NONBLOCK) {
  		if (flags & O_EXCL) {
  			if (sdp->open_cnt > 0) {
  				retval = -EBUSY;
  				goto error_mutex_locked;
  			}
  		} else {
  			if (sdp->exclude) {
  				retval = -EBUSY;
  				goto error_mutex_locked;
  			}

  		}

  	} else {
  		retval = open_wait(sdp, flags);
  		if (retval) /* -ERESTARTSYS or -ENODEV */
  			goto error_mutex_locked;

  	}

  
  	/* N.B. at this point we are holding the open_rel_lock */
  	if (flags & O_EXCL)
  		sdp->exclude = true;
  
  	if (sdp->open_cnt < 1) {  /* no existing opens */

  		sdp->sgdebug = 0;

  		q = sdp->device->request_queue;

  		sdp->sg_tablesize = queue_max_segments(q);

  	}

  	sfp = sg_add_sfp(sdp);

  	if (IS_ERR(sfp)) {
  		retval = PTR_ERR(sfp);
  		goto out_undo;

  	}

  
  	filp->private_data = sfp;
  	sdp->open_cnt++;
  	mutex_unlock(&sdp->open_rel_lock);

  	retval = 0;

  sg_put:

  	kref_put(&sdp->d_ref, sg_device_destroy);

  	return retval;

  
  out_undo:
  	if (flags & O_EXCL) {
  		sdp->exclude = false;   /* undo if error */
  		wake_up_interruptible(&sdp->open_wait);
  	}
  error_mutex_locked:
  	mutex_unlock(&sdp->open_rel_lock);
  error_out:
  	scsi_autopm_put_device(sdp->device);
  sdp_put:
  	scsi_device_put(sdp->device);
  	goto sg_put;

  }

  /* Release resources associated with a successful sg_open()
   * Returns 0 on success, else a negated errno value */

  static int
  sg_release(struct inode *inode, struct file *filp)
  {
  	Sg_device *sdp;
  	Sg_fd *sfp;
  
  	if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
  		return -ENXIO;

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp, "sg_release
  "));

  	mutex_lock(&sdp->open_rel_lock);

  	scsi_autopm_put_device(sdp->device);

  	kref_put(&sfp->f_ref, sg_remove_sfp);

  	sdp->open_cnt--;
  
  	/* possibly many open()s waiting on exlude clearing, start many;
  	 * only open(O_EXCL)s wait on 0==open_cnt so only start one */
  	if (sdp->exclude) {
  		sdp->exclude = false;
  		wake_up_interruptible_all(&sdp->open_wait);
  	} else if (0 == sdp->open_cnt) {
  		wake_up_interruptible(&sdp->open_wait);
  	}
  	mutex_unlock(&sdp->open_rel_lock);

  	return 0;
  }
  
  static ssize_t
  sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
  {

  	Sg_device *sdp;
  	Sg_fd *sfp;
  	Sg_request *srp;
  	int req_pack_id = -1;

  	sg_io_hdr_t *hp;

  	struct sg_header *old_hdr = NULL;
  	int retval = 0;

  	/*
  	 * This could cause a response to be stranded. Close the associated
  	 * file descriptor to free up any resources being held.
  	 */
  	retval = sg_check_file_access(filp, __func__);
  	if (retval)
  		return retval;

  	if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
  		return -ENXIO;

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
  				      "sg_read: count=%d
  ", (int) count));

  	if (!access_ok(VERIFY_WRITE, buf, count))
  		return -EFAULT;
  	if (sfp->force_packid && (count >= SZ_SG_HEADER)) {

  		old_hdr = kmalloc(SZ_SG_HEADER, GFP_KERNEL);
  		if (!old_hdr)
  			return -ENOMEM;
  		if (__copy_from_user(old_hdr, buf, SZ_SG_HEADER)) {
  			retval = -EFAULT;
  			goto free_old_hdr;
  		}
  		if (old_hdr->reply_len < 0) {

  			if (count >= SZ_SG_IO_HDR) {

  				sg_io_hdr_t *new_hdr;
  				new_hdr = kmalloc(SZ_SG_IO_HDR, GFP_KERNEL);
  				if (!new_hdr) {
  					retval = -ENOMEM;
  					goto free_old_hdr;
  				}
  				retval =__copy_from_user
  				    (new_hdr, buf, SZ_SG_IO_HDR);
  				req_pack_id = new_hdr->pack_id;
  				kfree(new_hdr);
  				if (retval) {
  					retval = -EFAULT;
  					goto free_old_hdr;
  				}

  			}
  		} else

  			req_pack_id = old_hdr->pack_id;

  	}
  	srp = sg_get_rq_mark(sfp, req_pack_id);
  	if (!srp) {		/* now wait on packet to arrive */

  		if (atomic_read(&sdp->detaching)) {

  			retval = -ENODEV;
  			goto free_old_hdr;
  		}
  		if (filp->f_flags & O_NONBLOCK) {
  			retval = -EAGAIN;
  			goto free_old_hdr;
  		}

  		retval = wait_event_interruptible(sfp->read_wait,

  			(atomic_read(&sdp->detaching) ||

  			(srp = sg_get_rq_mark(sfp, req_pack_id))));

  		if (atomic_read(&sdp->detaching)) {

  			retval = -ENODEV;
  			goto free_old_hdr;
  		}
  		if (retval) {

  			/* -ERESTARTSYS as signal hit process */
  			goto free_old_hdr;

  		}
  	}

  	if (srp->header.interface_id != '\0') {
  		retval = sg_new_read(sfp, buf, count, srp);
  		goto free_old_hdr;
  	}

  
  	hp = &srp->header;

  	if (old_hdr == NULL) {
  		old_hdr = kmalloc(SZ_SG_HEADER, GFP_KERNEL);
  		if (! old_hdr) {
  			retval = -ENOMEM;
  			goto free_old_hdr;
  		}
  	}
  	memset(old_hdr, 0, SZ_SG_HEADER);
  	old_hdr->reply_len = (int) hp->timeout;
  	old_hdr->pack_len = old_hdr->reply_len; /* old, strange behaviour */
  	old_hdr->pack_id = hp->pack_id;
  	old_hdr->twelve_byte =

  	    ((srp->data.cmd_opcode >= 0xc0) && (12 == hp->cmd_len)) ? 1 : 0;

  	old_hdr->target_status = hp->masked_status;
  	old_hdr->host_status = hp->host_status;
  	old_hdr->driver_status = hp->driver_status;

  	if ((CHECK_CONDITION & hp->masked_status) ||
  	    (DRIVER_SENSE & hp->driver_status))

  		memcpy(old_hdr->sense_buffer, srp->sense_b,
  		       sizeof (old_hdr->sense_buffer));

  	switch (hp->host_status) {
  	/* This setup of 'result' is for backward compatibility and is best
  	   ignored by the user who should use target, host + driver status */
  	case DID_OK:
  	case DID_PASSTHROUGH:
  	case DID_SOFT_ERROR:

  		old_hdr->result = 0;

  		break;
  	case DID_NO_CONNECT:
  	case DID_BUS_BUSY:
  	case DID_TIME_OUT:

  		old_hdr->result = EBUSY;

  		break;
  	case DID_BAD_TARGET:
  	case DID_ABORT:
  	case DID_PARITY:
  	case DID_RESET:
  	case DID_BAD_INTR:

  		old_hdr->result = EIO;

  		break;
  	case DID_ERROR:

  		old_hdr->result = (srp->sense_b[0] == 0 && 

  				  hp->masked_status == GOOD) ? 0 : EIO;
  		break;
  	default:

  		old_hdr->result = EIO;

  		break;
  	}
  
  	/* Now copy the result back to the user buffer.  */
  	if (count >= SZ_SG_HEADER) {

  		if (__copy_to_user(buf, old_hdr, SZ_SG_HEADER)) {
  			retval = -EFAULT;
  			goto free_old_hdr;
  		}

  		buf += SZ_SG_HEADER;

  		if (count > old_hdr->reply_len)
  			count = old_hdr->reply_len;

  		if (count > SZ_SG_HEADER) {

  			if (sg_read_oxfer(srp, buf, count - SZ_SG_HEADER)) {
  				retval = -EFAULT;
  				goto free_old_hdr;
  			}

  		}
  	} else

  		count = (old_hdr->result == 0) ? 0 : -EIO;

  	sg_finish_rem_req(srp);

  	sg_remove_request(sfp, srp);

  	retval = count;
  free_old_hdr:

  	kfree(old_hdr);

  	return retval;

  }
  
  static ssize_t
  sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
  {
  	sg_io_hdr_t *hp = &srp->header;

  	int err = 0, err2;

  	int len;
  
  	if (count < SZ_SG_IO_HDR) {
  		err = -EINVAL;
  		goto err_out;
  	}
  	hp->sb_len_wr = 0;
  	if ((hp->mx_sb_len > 0) && hp->sbp) {
  		if ((CHECK_CONDITION & hp->masked_status) ||
  		    (DRIVER_SENSE & hp->driver_status)) {

  			int sb_len = SCSI_SENSE_BUFFERSIZE;

  			sb_len = (hp->mx_sb_len > sb_len) ? sb_len : hp->mx_sb_len;
  			len = 8 + (int) srp->sense_b[7];	/* Additional sense length field */
  			len = (len > sb_len) ? sb_len : len;
  			if (copy_to_user(hp->sbp, srp->sense_b, len)) {
  				err = -EFAULT;
  				goto err_out;
  			}
  			hp->sb_len_wr = len;
  		}
  	}
  	if (hp->masked_status || hp->host_status || hp->driver_status)
  		hp->info |= SG_INFO_CHECK;
  	if (copy_to_user(buf, hp, SZ_SG_IO_HDR)) {
  		err = -EFAULT;
  		goto err_out;
  	}

  err_out:

  	err2 = sg_finish_rem_req(srp);

  	sg_remove_request(sfp, srp);

  	return err ? : err2 ? : count;

  }
  
  static ssize_t
  sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
  {
  	int mxsize, cmd_size, k;
  	int input_size, blocking;
  	unsigned char opcode;
  	Sg_device *sdp;
  	Sg_fd *sfp;
  	Sg_request *srp;
  	struct sg_header old_hdr;
  	sg_io_hdr_t *hp;

  	unsigned char cmnd[SG_MAX_CDB_SIZE];

  	int retval;

  	retval = sg_check_file_access(filp, __func__);
  	if (retval)
  		return retval;

  	if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
  		return -ENXIO;

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
  				      "sg_write: count=%d
  ", (int) count));

  	if (atomic_read(&sdp->detaching))

  		return -ENODEV;
  	if (!((filp->f_flags & O_NONBLOCK) ||
  	      scsi_block_when_processing_errors(sdp->device)))
  		return -ENXIO;
  
  	if (!access_ok(VERIFY_READ, buf, count))
  		return -EFAULT;	/* protects following copy_from_user()s + get_user()s */
  	if (count < SZ_SG_HEADER)
  		return -EIO;
  	if (__copy_from_user(&old_hdr, buf, SZ_SG_HEADER))
  		return -EFAULT;
  	blocking = !(filp->f_flags & O_NONBLOCK);
  	if (old_hdr.reply_len < 0)

  		return sg_new_write(sfp, filp, buf, count,
  				    blocking, 0, 0, NULL);

  	if (count < (SZ_SG_HEADER + 6))
  		return -EIO;	/* The minimum scsi command length is 6 bytes. */
  
  	if (!(srp = sg_add_request(sfp))) {

  		SCSI_LOG_TIMEOUT(1, sg_printk(KERN_INFO, sdp,
  					      "sg_write: queue full
  "));

  		return -EDOM;
  	}
  	buf += SZ_SG_HEADER;
  	__get_user(opcode, buf);

  	mutex_lock(&sfp->f_mutex);

  	if (sfp->next_cmd_len > 0) {

  		cmd_size = sfp->next_cmd_len;
  		sfp->next_cmd_len = 0;	/* reset so only this write() effected */
  	} else {
  		cmd_size = COMMAND_SIZE(opcode);	/* based on SCSI command group */
  		if ((opcode >= 0xc0) && old_hdr.twelve_byte)
  			cmd_size = 12;
  	}

  	mutex_unlock(&sfp->f_mutex);

  	SCSI_LOG_TIMEOUT(4, sg_printk(KERN_INFO, sdp,

  		"sg_write:   scsi opcode=0x%02x, cmd_size=%d
  ", (int) opcode, cmd_size));
  /* Determine buffer size.  */
  	input_size = count - cmd_size;
  	mxsize = (input_size > old_hdr.reply_len) ? input_size : old_hdr.reply_len;
  	mxsize -= SZ_SG_HEADER;
  	input_size -= SZ_SG_HEADER;
  	if (input_size < 0) {
  		sg_remove_request(sfp, srp);
  		return -EIO;	/* User did not pass enough bytes for this command. */
  	}
  	hp = &srp->header;
  	hp->interface_id = '\0';	/* indicator of old interface tunnelled */
  	hp->cmd_len = (unsigned char) cmd_size;
  	hp->iovec_count = 0;
  	hp->mx_sb_len = 0;
  	if (input_size > 0)
  		hp->dxfer_direction = (old_hdr.reply_len > SZ_SG_HEADER) ?
  		    SG_DXFER_TO_FROM_DEV : SG_DXFER_TO_DEV;
  	else
  		hp->dxfer_direction = (mxsize > 0) ? SG_DXFER_FROM_DEV : SG_DXFER_NONE;
  	hp->dxfer_len = mxsize;

  	if ((hp->dxfer_direction == SG_DXFER_TO_DEV) ||
  	    (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV))

  		hp->dxferp = (char __user *)buf + cmd_size;
  	else
  		hp->dxferp = NULL;

  	hp->sbp = NULL;
  	hp->timeout = old_hdr.reply_len;	/* structure abuse ... */
  	hp->flags = input_size;	/* structure abuse ... */
  	hp->pack_id = old_hdr.pack_id;
  	hp->usr_ptr = NULL;
  	if (__copy_from_user(cmnd, buf, cmd_size))
  		return -EFAULT;
  	/*
  	 * SG_DXFER_TO_FROM_DEV is functionally equivalent to SG_DXFER_FROM_DEV,
  	 * but is is possible that the app intended SG_DXFER_TO_DEV, because there
  	 * is a non-zero input_size, so emit a warning.
  	 */

  	if (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV) {

  		printk_ratelimited(KERN_WARNING
  				   "sg_write: data in/out %d/%d bytes "
  				   "for SCSI command 0x%x-- guessing "
  				   "data in;
     program %s not setting "
  				   "count and/or reply_len properly
  ",
  				   old_hdr.reply_len - (int)SZ_SG_HEADER,
  				   input_size, (unsigned int) cmnd[0],
  				   current->comm);

  	}

  	k = sg_common_write(sfp, srp, cmnd, sfp->timeout, blocking);
  	return (k < 0) ? k : count;
  }
  
  static ssize_t

  sg_new_write(Sg_fd *sfp, struct file *file, const char __user *buf,

  		 size_t count, int blocking, int read_only, int sg_io_owned,

  		 Sg_request **o_srp)

  {
  	int k;
  	Sg_request *srp;
  	sg_io_hdr_t *hp;

  	unsigned char cmnd[SG_MAX_CDB_SIZE];

  	int timeout;
  	unsigned long ul_timeout;
  
  	if (count < SZ_SG_IO_HDR)
  		return -EINVAL;
  	if (!access_ok(VERIFY_READ, buf, count))
  		return -EFAULT; /* protects following copy_from_user()s + get_user()s */
  
  	sfp->cmd_q = 1;	/* when sg_io_hdr seen, set command queuing on */
  	if (!(srp = sg_add_request(sfp))) {

  		SCSI_LOG_TIMEOUT(1, sg_printk(KERN_INFO, sfp->parentdp,
  					      "sg_new_write: queue full
  "));

  		return -EDOM;
  	}

  	srp->sg_io_owned = sg_io_owned;

  	hp = &srp->header;
  	if (__copy_from_user(hp, buf, SZ_SG_IO_HDR)) {
  		sg_remove_request(sfp, srp);
  		return -EFAULT;
  	}
  	if (hp->interface_id != 'S') {
  		sg_remove_request(sfp, srp);
  		return -ENOSYS;
  	}
  	if (hp->flags & SG_FLAG_MMAP_IO) {
  		if (hp->dxfer_len > sfp->reserve.bufflen) {
  			sg_remove_request(sfp, srp);
  			return -ENOMEM;	/* MMAP_IO size must fit in reserve buffer */
  		}
  		if (hp->flags & SG_FLAG_DIRECT_IO) {
  			sg_remove_request(sfp, srp);
  			return -EINVAL;	/* either MMAP_IO or DIRECT_IO (not both) */
  		}

  		if (sfp->res_in_use) {

  			sg_remove_request(sfp, srp);
  			return -EBUSY;	/* reserve buffer already being used */
  		}
  	}
  	ul_timeout = msecs_to_jiffies(srp->header.timeout);
  	timeout = (ul_timeout < INT_MAX) ? ul_timeout : INT_MAX;
  	if ((!hp->cmdp) || (hp->cmd_len < 6) || (hp->cmd_len > sizeof (cmnd))) {
  		sg_remove_request(sfp, srp);
  		return -EMSGSIZE;
  	}
  	if (!access_ok(VERIFY_READ, hp->cmdp, hp->cmd_len)) {
  		sg_remove_request(sfp, srp);
  		return -EFAULT;	/* protects following copy_from_user()s + get_user()s */
  	}
  	if (__copy_from_user(cmnd, hp->cmdp, hp->cmd_len)) {
  		sg_remove_request(sfp, srp);
  		return -EFAULT;
  	}

  	if (read_only && sg_allow_access(file, cmnd)) {

  		sg_remove_request(sfp, srp);
  		return -EPERM;
  	}
  	k = sg_common_write(sfp, srp, cmnd, timeout, blocking);
  	if (k < 0)
  		return k;
  	if (o_srp)
  		*o_srp = srp;
  	return count;
  }
  
  static int
  sg_common_write(Sg_fd * sfp, Sg_request * srp,
  		unsigned char *cmnd, int timeout, int blocking)
  {

  	int k, at_head;

  	Sg_device *sdp = sfp->parentdp;
  	sg_io_hdr_t *hp = &srp->header;

  
  	srp->data.cmd_opcode = cmnd[0];	/* hold opcode of command */
  	hp->status = 0;
  	hp->masked_status = 0;
  	hp->msg_status = 0;
  	hp->info = 0;
  	hp->host_status = 0;
  	hp->driver_status = 0;
  	hp->resid = 0;

  	SCSI_LOG_TIMEOUT(4, sg_printk(KERN_INFO, sfp->parentdp,
  			"sg_common_write:  scsi opcode=0x%02x, cmd_size=%d
  ",
  			(int) cmnd[0], (int) hp->cmd_len));

  	if (hp->dxfer_len >= SZ_256M)

  		return -EINVAL;

  	k = sg_start_req(srp, cmnd);
  	if (k) {

  		SCSI_LOG_TIMEOUT(1, sg_printk(KERN_INFO, sfp->parentdp,
  			"sg_common_write: start_req err=%d
  ", k));

  		sg_finish_rem_req(srp);

  		sg_remove_request(sfp, srp);

  		return k;	/* probably out of space --> ENOMEM */
  	}

  	if (atomic_read(&sdp->detaching)) {

  		if (srp->bio) {

  			scsi_req_free_cmd(scsi_req(srp->rq));

  			blk_end_request_all(srp->rq, BLK_STS_IOERR);

  			srp->rq = NULL;
  		}

  		sg_finish_rem_req(srp);

  		sg_remove_request(sfp, srp);

  		return -ENODEV;
  	}

  	hp->duration = jiffies_to_msecs(jiffies);

  	if (hp->interface_id != '\0' &&	/* v3 (or later) interface */
  	    (SG_FLAG_Q_AT_TAIL & hp->flags))
  		at_head = 0;
  	else
  		at_head = 1;

  
  	srp->rq->timeout = timeout;

  	kref_get(&sfp->f_ref); /* sg_rq_end_io() does kref_put(). */

  	blk_execute_rq_nowait(sdp->device->request_queue, sdp->disk,

  			      srp->rq, at_head, sg_rq_end_io);

  	return 0;

  }

  static int srp_done(Sg_fd *sfp, Sg_request *srp)
  {
  	unsigned long flags;
  	int ret;
  
  	read_lock_irqsave(&sfp->rq_list_lock, flags);
  	ret = srp->done;
  	read_unlock_irqrestore(&sfp->rq_list_lock, flags);
  	return ret;
  }

  static int max_sectors_bytes(struct request_queue *q)
  {
  	unsigned int max_sectors = queue_max_sectors(q);
  
  	max_sectors = min_t(unsigned int, max_sectors, INT_MAX >> 9);
  
  	return max_sectors << 9;
  }

  static void
  sg_fill_request_table(Sg_fd *sfp, sg_req_info_t *rinfo)
  {
  	Sg_request *srp;
  	int val;
  	unsigned int ms;
  
  	val = 0;
  	list_for_each_entry(srp, &sfp->rq_list, entry) {

  		if (val >= SG_MAX_QUEUE)

  			break;

  		rinfo[val].req_state = srp->done + 1;
  		rinfo[val].problem =
  			srp->header.masked_status &
  			srp->header.host_status &
  			srp->header.driver_status;
  		if (srp->done)
  			rinfo[val].duration =
  				srp->header.duration;
  		else {
  			ms = jiffies_to_msecs(jiffies);
  			rinfo[val].duration =
  				(ms > srp->header.duration) ?
  				(ms - srp->header.duration) : 0;
  		}
  		rinfo[val].orphan = srp->orphan;
  		rinfo[val].sg_io_owned = srp->sg_io_owned;
  		rinfo[val].pack_id = srp->header.pack_id;
  		rinfo[val].usr_ptr = srp->header.usr_ptr;
  		val++;
  	}
  }

  static long

  sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)

  {
  	void __user *p = (void __user *)arg;
  	int __user *ip = p;

  	int result, val, read_only;

  	Sg_device *sdp;
  	Sg_fd *sfp;
  	Sg_request *srp;
  	unsigned long iflags;
  
  	if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
  		return -ENXIO;

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
  				   "sg_ioctl: cmd=0x%x
  ", (int) cmd_in));

  	read_only = (O_RDWR != (filp->f_flags & O_ACCMODE));
  
  	switch (cmd_in) {
  	case SG_IO:

  		if (atomic_read(&sdp->detaching))

  			return -ENODEV;
  		if (!scsi_block_when_processing_errors(sdp->device))
  			return -ENXIO;
  		if (!access_ok(VERIFY_WRITE, p, SZ_SG_IO_HDR))
  			return -EFAULT;
  		result = sg_new_write(sfp, filp, p, SZ_SG_IO_HDR,
  				 1, read_only, 1, &srp);
  		if (result < 0)
  			return result;

  		result = wait_event_interruptible(sfp->read_wait,

  			(srp_done(sfp, srp) || atomic_read(&sdp->detaching)));
  		if (atomic_read(&sdp->detaching))

  			return -ENODEV;
  		write_lock_irq(&sfp->rq_list_lock);
  		if (srp->done) {
  			srp->done = 2;

  			write_unlock_irq(&sfp->rq_list_lock);

  			result = sg_new_read(sfp, p, SZ_SG_IO_HDR, srp);
  			return (result < 0) ? result : 0;

  		}

  		srp->orphan = 1;
  		write_unlock_irq(&sfp->rq_list_lock);
  		return result;	/* -ERESTARTSYS because signal hit process */

  	case SG_SET_TIMEOUT:
  		result = get_user(val, ip);
  		if (result)
  			return result;
  		if (val < 0)
  			return -EIO;

  		if (val >= mult_frac((s64)INT_MAX, USER_HZ, HZ))
  			val = min_t(s64, mult_frac((s64)INT_MAX, USER_HZ, HZ),

  				    INT_MAX);

  		sfp->timeout_user = val;

  		sfp->timeout = mult_frac(val, HZ, USER_HZ);

  
  		return 0;
  	case SG_GET_TIMEOUT:	/* N.B. User receives timeout as return value */
  				/* strange ..., for backward compatibility */
  		return sfp->timeout_user;
  	case SG_SET_FORCE_LOW_DMA:

  		/*
  		 * N.B. This ioctl never worked properly, but failed to
  		 * return an error value. So returning '0' to keep compability
  		 * with legacy applications.
  		 */

  		return 0;
  	case SG_GET_LOW_DMA:

  		return put_user((int) sdp->device->host->unchecked_isa_dma, ip);

  	case SG_GET_SCSI_ID:
  		if (!access_ok(VERIFY_WRITE, p, sizeof (sg_scsi_id_t)))
  			return -EFAULT;
  		else {
  			sg_scsi_id_t __user *sg_idp = p;

  			if (atomic_read(&sdp->detaching))

  				return -ENODEV;
  			__put_user((int) sdp->device->host->host_no,
  				   &sg_idp->host_no);
  			__put_user((int) sdp->device->channel,
  				   &sg_idp->channel);
  			__put_user((int) sdp->device->id, &sg_idp->scsi_id);
  			__put_user((int) sdp->device->lun, &sg_idp->lun);
  			__put_user((int) sdp->device->type, &sg_idp->scsi_type);
  			__put_user((short) sdp->device->host->cmd_per_lun,
  				   &sg_idp->h_cmd_per_lun);
  			__put_user((short) sdp->device->queue_depth,
  				   &sg_idp->d_queue_depth);
  			__put_user(0, &sg_idp->unused[0]);
  			__put_user(0, &sg_idp->unused[1]);
  			return 0;
  		}
  	case SG_SET_FORCE_PACK_ID:
  		result = get_user(val, ip);
  		if (result)
  			return result;
  		sfp->force_packid = val ? 1 : 0;
  		return 0;
  	case SG_GET_PACK_ID:
  		if (!access_ok(VERIFY_WRITE, ip, sizeof (int)))
  			return -EFAULT;
  		read_lock_irqsave(&sfp->rq_list_lock, iflags);

  		list_for_each_entry(srp, &sfp->rq_list, entry) {

  			if ((1 == srp->done) && (!srp->sg_io_owned)) {
  				read_unlock_irqrestore(&sfp->rq_list_lock,
  						       iflags);
  				__put_user(srp->header.pack_id, ip);
  				return 0;
  			}
  		}
  		read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
  		__put_user(-1, ip);
  		return 0;
  	case SG_GET_NUM_WAITING:
  		read_lock_irqsave(&sfp->rq_list_lock, iflags);

  		val = 0;
  		list_for_each_entry(srp, &sfp->rq_list, entry) {

  			if ((1 == srp->done) && (!srp->sg_io_owned))
  				++val;
  		}
  		read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
  		return put_user(val, ip);
  	case SG_GET_SG_TABLESIZE:
  		return put_user(sdp->sg_tablesize, ip);
  	case SG_SET_RESERVED_SIZE:
  		result = get_user(val, ip);
  		if (result)
  			return result;
                  if (val < 0)
                          return -EINVAL;

  		val = min_t(int, val,

  			    max_sectors_bytes(sdp->device->request_queue));

  		mutex_lock(&sfp->f_mutex);

  		if (val != sfp->reserve.bufflen) {

  			if (sfp->mmap_called ||
  			    sfp->res_in_use) {
  				mutex_unlock(&sfp->f_mutex);

  				return -EBUSY;

  			}

  			sg_remove_scat(sfp, &sfp->reserve);

  			sg_build_reserve(sfp, val);
  		}

  		mutex_unlock(&sfp->f_mutex);

  		return 0;
  	case SG_GET_RESERVED_SIZE:

  		val = min_t(int, sfp->reserve.bufflen,

  			    max_sectors_bytes(sdp->device->request_queue));

  		return put_user(val, ip);
  	case SG_SET_COMMAND_Q:
  		result = get_user(val, ip);
  		if (result)
  			return result;
  		sfp->cmd_q = val ? 1 : 0;
  		return 0;
  	case SG_GET_COMMAND_Q:
  		return put_user((int) sfp->cmd_q, ip);
  	case SG_SET_KEEP_ORPHAN:
  		result = get_user(val, ip);
  		if (result)
  			return result;
  		sfp->keep_orphan = val;
  		return 0;
  	case SG_GET_KEEP_ORPHAN:
  		return put_user((int) sfp->keep_orphan, ip);
  	case SG_NEXT_CMD_LEN:
  		result = get_user(val, ip);
  		if (result)
  			return result;

  		if (val > SG_MAX_CDB_SIZE)
  			return -ENOMEM;

  		sfp->next_cmd_len = (val > 0) ? val : 0;
  		return 0;
  	case SG_GET_VERSION_NUM:
  		return put_user(sg_version_num, ip);
  	case SG_GET_ACCESS_COUNT:
  		/* faked - we don't have a real access count anymore */
  		val = (sdp->device ? 1 : 0);
  		return put_user(val, ip);
  	case SG_GET_REQUEST_TABLE:
  		if (!access_ok(VERIFY_WRITE, p, SZ_SG_REQ_INFO * SG_MAX_QUEUE))
  			return -EFAULT;
  		else {

  			sg_req_info_t *rinfo;

  			rinfo = kzalloc(SZ_SG_REQ_INFO * SG_MAX_QUEUE,
  					GFP_KERNEL);

  			if (!rinfo)
  				return -ENOMEM;

  			read_lock_irqsave(&sfp->rq_list_lock, iflags);

  			sg_fill_request_table(sfp, rinfo);

  			read_unlock_irqrestore(&sfp->rq_list_lock, iflags);

  			result = __copy_to_user(p, rinfo,

  						SZ_SG_REQ_INFO * SG_MAX_QUEUE);
  			result = result ? -EFAULT : 0;
  			kfree(rinfo);
  			return result;

  		}
  	case SG_EMULATED_HOST:

  		if (atomic_read(&sdp->detaching))

  			return -ENODEV;
  		return put_user(sdp->device->host->hostt->emulated, ip);

  	case SCSI_IOCTL_SEND_COMMAND:

  		if (atomic_read(&sdp->detaching))

  			return -ENODEV;
  		if (read_only) {
  			unsigned char opcode = WRITE_6;
  			Scsi_Ioctl_Command __user *siocp = p;
  
  			if (copy_from_user(&opcode, siocp->data, 1))
  				return -EFAULT;

  			if (sg_allow_access(filp, &opcode))

  				return -EPERM;
  		}

  		return sg_scsi_ioctl(sdp->device->request_queue, NULL, filp->f_mode, p);

  	case SG_SET_DEBUG:
  		result = get_user(val, ip);
  		if (result)
  			return result;
  		sdp->sgdebug = (char) val;
  		return 0;

  	case BLKSECTGET:

  		return put_user(max_sectors_bytes(sdp->device->request_queue),

  				ip);

  	case BLKTRACESETUP:
  		return blk_trace_setup(sdp->device->request_queue,
  				       sdp->disk->disk_name,

  				       MKDEV(SCSI_GENERIC_MAJOR, sdp->index),

  				       NULL, p);

  	case BLKTRACESTART:
  		return blk_trace_startstop(sdp->device->request_queue, 1);
  	case BLKTRACESTOP:
  		return blk_trace_startstop(sdp->device->request_queue, 0);
  	case BLKTRACETEARDOWN:
  		return blk_trace_remove(sdp->device->request_queue);

  	case SCSI_IOCTL_GET_IDLUN:
  	case SCSI_IOCTL_GET_BUS_NUMBER:
  	case SCSI_IOCTL_PROBE_HOST:
  	case SG_GET_TRANSFORM:
  	case SG_SCSI_RESET:
  		if (atomic_read(&sdp->detaching))
  			return -ENODEV;
  		break;

  	default:
  		if (read_only)
  			return -EPERM;	/* don't know so take safe approach */

  		break;

  	}

  
  	result = scsi_ioctl_block_when_processing_errors(sdp->device,
  			cmd_in, filp->f_flags & O_NDELAY);
  	if (result)
  		return result;
  	return scsi_ioctl(sdp->device, cmd_in, p);

  }
  
  #ifdef CONFIG_COMPAT
  static long sg_compat_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
  {
  	Sg_device *sdp;
  	Sg_fd *sfp;
  	struct scsi_device *sdev;
  
  	if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
  		return -ENXIO;
  
  	sdev = sdp->device;
  	if (sdev->host->hostt->compat_ioctl) { 
  		int ret;
  
  		ret = sdev->host->hostt->compat_ioctl(sdev, cmd_in, (void __user *)arg);
  
  		return ret;
  	}
  	
  	return -ENOIOCTLCMD;
  }
  #endif
  
  static unsigned int
  sg_poll(struct file *filp, poll_table * wait)
  {
  	unsigned int res = 0;
  	Sg_device *sdp;
  	Sg_fd *sfp;
  	Sg_request *srp;
  	int count = 0;
  	unsigned long iflags;

  	sfp = filp->private_data;
  	if (!sfp)
  		return POLLERR;
  	sdp = sfp->parentdp;
  	if (!sdp)

  		return POLLERR;
  	poll_wait(filp, &sfp->read_wait, wait);
  	read_lock_irqsave(&sfp->rq_list_lock, iflags);

  	list_for_each_entry(srp, &sfp->rq_list, entry) {

  		/* if any read waiting, flag it */
  		if ((0 == res) && (1 == srp->done) && (!srp->sg_io_owned))
  			res = POLLIN | POLLRDNORM;
  		++count;
  	}
  	read_unlock_irqrestore(&sfp->rq_list_lock, iflags);

  	if (atomic_read(&sdp->detaching))

  		res |= POLLHUP;
  	else if (!sfp->cmd_q) {
  		if (0 == count)
  			res |= POLLOUT | POLLWRNORM;
  	} else if (count < SG_MAX_QUEUE)
  		res |= POLLOUT | POLLWRNORM;

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
  				      "sg_poll: res=0x%x
  ", (int) res));

  	return res;
  }
  
  static int
  sg_fasync(int fd, struct file *filp, int mode)
  {

  	Sg_device *sdp;
  	Sg_fd *sfp;
  
  	if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
  		return -ENXIO;

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
  				      "sg_fasync: mode=%d
  ", mode));

  	return fasync_helper(fd, filp, mode, &sfp->async_qp);

  }

  static int

  sg_vma_fault(struct vm_fault *vmf)

  {

  	struct vm_area_struct *vma = vmf->vma;

  	Sg_fd *sfp;

  	unsigned long offset, len, sa;

  	Sg_scatter_hold *rsv_schp;

  	int k, length;

  
  	if ((NULL == vma) || (!(sfp = (Sg_fd *) vma->vm_private_data)))

  		return VM_FAULT_SIGBUS;

  	rsv_schp = &sfp->reserve;

  	offset = vmf->pgoff << PAGE_SHIFT;

  	if (offset >= rsv_schp->bufflen)

  		return VM_FAULT_SIGBUS;

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sfp->parentdp,
  				      "sg_vma_fault: offset=%lu, scatg=%d
  ",
  				      offset, rsv_schp->k_use_sg));

  	sa = vma->vm_start;

  	length = 1 << (PAGE_SHIFT + rsv_schp->page_order);
  	for (k = 0; k < rsv_schp->k_use_sg && sa < vma->vm_end; k++) {

  		len = vma->vm_end - sa;

  		len = (len < length) ? len : length;

  		if (offset < len) {

  			struct page *page = nth_page(rsv_schp->pages[k],
  						     offset >> PAGE_SHIFT);

  			get_page(page);	/* increment page count */

  			vmf->page = page;
  			return 0; /* success */

  		}

  		sa += len;
  		offset -= len;

  	}

  	return VM_FAULT_SIGBUS;

  }

  static const struct vm_operations_struct sg_mmap_vm_ops = {

  	.fault = sg_vma_fault,

  };
  
  static int
  sg_mmap(struct file *filp, struct vm_area_struct *vma)
  {
  	Sg_fd *sfp;

  	unsigned long req_sz, len, sa;

  	Sg_scatter_hold *rsv_schp;

  	int k, length;

  	int ret = 0;

  
  	if ((!filp) || (!vma) || (!(sfp = (Sg_fd *) filp->private_data)))
  		return -ENXIO;

  	req_sz = vma->vm_end - vma->vm_start;

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sfp->parentdp,
  				      "sg_mmap starting, vm_start=%p, len=%d
  ",
  				      (void *) vma->vm_start, (int) req_sz));

  	if (vma->vm_pgoff)
  		return -EINVAL;	/* want no offset */
  	rsv_schp = &sfp->reserve;

  	mutex_lock(&sfp->f_mutex);
  	if (req_sz > rsv_schp->bufflen) {
  		ret = -ENOMEM;	/* cannot map more than reserved buffer */
  		goto out;
  	}

  	sa = vma->vm_start;

  	length = 1 << (PAGE_SHIFT + rsv_schp->page_order);
  	for (k = 0; k < rsv_schp->k_use_sg && sa < vma->vm_end; k++) {

  		len = vma->vm_end - sa;

  		len = (len < length) ? len : length;

  		sa += len;

  	}

  	sfp->mmap_called = 1;

  	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;

  	vma->vm_private_data = sfp;
  	vma->vm_ops = &sg_mmap_vm_ops;

  out:
  	mutex_unlock(&sfp->f_mutex);
  	return ret;

  }

  static void
  sg_rq_end_io_usercontext(struct work_struct *work)

  {
  	struct sg_request *srp = container_of(work, struct sg_request, ew.work);
  	struct sg_fd *sfp = srp->parentfp;
  
  	sg_finish_rem_req(srp);

  	sg_remove_request(sfp, srp);

  	kref_put(&sfp->f_ref, sg_remove_sfp);
  }

  /*
   * This function is a "bottom half" handler that is called by the mid
   * level when a command is completed (or has failed).
   */

  static void

  sg_rq_end_io(struct request *rq, blk_status_t status)

  {

  	struct sg_request *srp = rq->end_io_data;

  	struct scsi_request *req = scsi_req(rq);

  	Sg_device *sdp;

  	Sg_fd *sfp;

  	unsigned long iflags;

  	unsigned int ms;

  	char *sense;

  	int result, resid, done = 1;

  	if (WARN_ON(srp->done != 0))

  		return;

  	sfp = srp->parentfp;

  	if (WARN_ON(sfp == NULL))

  		return;

  
  	sdp = sfp->parentdp;

  	if (unlikely(atomic_read(&sdp->detaching)))
  		pr_info("%s: device detaching
  ", __func__);

  	sense = req->sense;

  	result = req->result;

  	resid = req->resid_len;

  	SCSI_LOG_TIMEOUT(4, sg_printk(KERN_INFO, sdp,
  				      "sg_cmd_done: pack_id=%d, res=0x%x
  ",
  				      srp->header.pack_id, result));

  	srp->header.resid = resid;

  	ms = jiffies_to_msecs(jiffies);
  	srp->header.duration = (ms > srp->header.duration) ?
  				(ms - srp->header.duration) : 0;

  	if (0 != result) {

  		struct scsi_sense_hdr sshdr;

  		srp->header.status = 0xff & result;
  		srp->header.masked_status = status_byte(result);
  		srp->header.msg_status = msg_byte(result);
  		srp->header.host_status = host_byte(result);
  		srp->header.driver_status = driver_byte(result);

  		if ((sdp->sgdebug > 0) &&
  		    ((CHECK_CONDITION == srp->header.masked_status) ||
  		     (COMMAND_TERMINATED == srp->header.masked_status)))

  			__scsi_print_sense(sdp->device, __func__, sense,

  					   SCSI_SENSE_BUFFERSIZE);

  
  		/* Following if statement is a patch supplied by Eric Youngdale */

  		if (driver_byte(result) != 0
  		    && scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, &sshdr)

  		    && !scsi_sense_is_deferred(&sshdr)
  		    && sshdr.sense_key == UNIT_ATTENTION
  		    && sdp->device->removable) {
  			/* Detected possible disc change. Set the bit - this */
  			/* may be used if there are filesystems using this device */
  			sdp->device->changed = 1;
  		}
  	}

  
  	if (req->sense_len)
  		memcpy(srp->sense_b, req->sense, SCSI_SENSE_BUFFERSIZE);

  	/* Rely on write phase to clean out srp status values, so no "else" */

  	/*
  	 * Free the request as soon as it is complete so that its resources
  	 * can be reused without waiting for userspace to read() the
  	 * result.  But keep the associated bio (if any) around until
  	 * blk_rq_unmap_user() can be called from user context.
  	 */
  	srp->rq = NULL;

  	scsi_req_free_cmd(scsi_req(rq));

  	__blk_put_request(rq->q, rq);

  	write_lock_irqsave(&sfp->rq_list_lock, iflags);
  	if (unlikely(srp->orphan)) {

  		if (sfp->keep_orphan)
  			srp->sg_io_owned = 0;

  		else
  			done = 0;

  	}

  	srp->done = done;
  	write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
  
  	if (likely(done)) {
  		/* Now wake up any sg_read() that is waiting for this
  		 * packet.
  		 */

  		wake_up_interruptible(&sfp->read_wait);

  		kill_fasync(&sfp->async_qp, SIGPOLL, POLL_IN);

  		kref_put(&sfp->f_ref, sg_remove_sfp);

  	} else {
  		INIT_WORK(&srp->ew.work, sg_rq_end_io_usercontext);
  		schedule_work(&srp->ew.work);
  	}

  }

  static const struct file_operations sg_fops = {

  	.owner = THIS_MODULE,
  	.read = sg_read,
  	.write = sg_write,
  	.poll = sg_poll,

  	.unlocked_ioctl = sg_ioctl,

  #ifdef CONFIG_COMPAT
  	.compat_ioctl = sg_compat_ioctl,
  #endif
  	.open = sg_open,
  	.mmap = sg_mmap,
  	.release = sg_release,
  	.fasync = sg_fasync,

  	.llseek = no_llseek,

  };

  static struct class *sg_sysfs_class;

  
  static int sg_sysfs_valid = 0;

  static Sg_device *
  sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)

  {

  	struct request_queue *q = scsidp->request_queue;

  	Sg_device *sdp;
  	unsigned long iflags;

  	int error;
  	u32 k;

  	sdp = kzalloc(sizeof(Sg_device), GFP_KERNEL);

  	if (!sdp) {

  		sdev_printk(KERN_WARNING, scsidp, "%s: kmalloc Sg_device "
  			    "failure
  ", __func__);

  		return ERR_PTR(-ENOMEM);
  	}

  	idr_preload(GFP_KERNEL);

  	write_lock_irqsave(&sg_index_lock, iflags);

  	error = idr_alloc(&sg_index_idr, sdp, 0, SG_MAX_DEVS, GFP_NOWAIT);
  	if (error < 0) {
  		if (error == -ENOSPC) {
  			sdev_printk(KERN_WARNING, scsidp,
  				    "Unable to attach sg device type=%d, minor number exceeds %d
  ",
  				    scsidp->type, SG_MAX_DEVS - 1);
  			error = -ENODEV;
  		} else {

  			sdev_printk(KERN_WARNING, scsidp, "%s: idr "
  				    "allocation Sg_device failure: %d
  ",
  				    __func__, error);

  		}
  		goto out_unlock;

  	}

  	k = error;

  	SCSI_LOG_TIMEOUT(3, sdev_printk(KERN_INFO, scsidp,
  					"sg_alloc: dev=%d 
  ", k));

  	sprintf(disk->disk_name, "sg%d", k);
  	disk->first_minor = k;
  	sdp->disk = disk;
  	sdp->device = scsidp;

  	mutex_init(&sdp->open_rel_lock);

  	INIT_LIST_HEAD(&sdp->sfds);

  	init_waitqueue_head(&sdp->open_wait);
  	atomic_set(&sdp->detaching, 0);
  	rwlock_init(&sdp->sfd_lock);

  	sdp->sg_tablesize = queue_max_segments(q);

  	sdp->index = k;

  	kref_init(&sdp->d_ref);

  	error = 0;

  out_unlock:

  	write_unlock_irqrestore(&sg_index_lock, iflags);

  	idr_preload_end();

  	if (error) {

  		kfree(sdp);

  		return ERR_PTR(error);
  	}
  	return sdp;

  }
  
  static int

  sg_add_device(struct device *cl_dev, struct class_interface *cl_intf)

  {

  	struct scsi_device *scsidp = to_scsi_device(cl_dev->parent);

  	struct gendisk *disk;
  	Sg_device *sdp = NULL;
  	struct cdev * cdev = NULL;

  	int error;

  	unsigned long iflags;

  
  	disk = alloc_disk(1);
  	if (!disk) {

  		pr_warn("%s: alloc_disk failed
  ", __func__);

  		return -ENOMEM;
  	}
  	disk->major = SCSI_GENERIC_MAJOR;
  
  	error = -ENOMEM;
  	cdev = cdev_alloc();
  	if (!cdev) {

  		pr_warn("%s: cdev_alloc failed
  ", __func__);

  		goto out;
  	}
  	cdev->owner = THIS_MODULE;
  	cdev->ops = &sg_fops;

  	sdp = sg_alloc(disk, scsidp);
  	if (IS_ERR(sdp)) {

  		pr_warn("%s: sg_alloc failed
  ", __func__);

  		error = PTR_ERR(sdp);

  		goto out;
  	}

  	error = cdev_add(cdev, MKDEV(SCSI_GENERIC_MAJOR, sdp->index), 1);

  	if (error)

  		goto cdev_add_err;

  	sdp->cdev = cdev;
  	if (sg_sysfs_valid) {

  		struct device *sg_class_member;

  		sg_class_member = device_create(sg_sysfs_class, cl_dev->parent,
  						MKDEV(SCSI_GENERIC_MAJOR,
  						      sdp->index),
  						sdp, "%s", disk->disk_name);

  		if (IS_ERR(sg_class_member)) {

  			pr_err("%s: device_create failed
  ", __func__);

  			error = PTR_ERR(sg_class_member);
  			goto cdev_add_err;
  		}

  		error = sysfs_create_link(&scsidp->sdev_gendev.kobj,

  					  &sg_class_member->kobj, "generic");
  		if (error)

  			pr_err("%s: unable to make symlink 'generic' back "
  			       "to sg%d
  ", __func__, sdp->index);

  	} else

  		pr_warn("%s: sg_sys Invalid
  ", __func__);

  	sdev_printk(KERN_NOTICE, scsidp, "Attached scsi generic sg%d "
  		    "type %d
  ", sdp->index, scsidp->type);

  	dev_set_drvdata(cl_dev, sdp);

  	return 0;

  cdev_add_err:

  	write_lock_irqsave(&sg_index_lock, iflags);
  	idr_remove(&sg_index_idr, sdp->index);
  	write_unlock_irqrestore(&sg_index_lock, iflags);
  	kfree(sdp);

  out:
  	put_disk(disk);
  	if (cdev)
  		cdev_del(cdev);
  	return error;
  }

  static void
  sg_device_destroy(struct kref *kref)

  {
  	struct sg_device *sdp = container_of(kref, struct sg_device, d_ref);
  	unsigned long flags;
  
  	/* CAUTION!  Note that the device can still be found via idr_find()
  	 * even though the refcount is 0.  Therefore, do idr_remove() BEFORE
  	 * any other cleanup.
  	 */
  
  	write_lock_irqsave(&sg_index_lock, flags);
  	idr_remove(&sg_index_idr, sdp->index);
  	write_unlock_irqrestore(&sg_index_lock, flags);
  
  	SCSI_LOG_TIMEOUT(3,

  		sg_printk(KERN_INFO, sdp, "sg_device_destroy
  "));

  
  	put_disk(sdp->disk);
  	kfree(sdp);
  }

  static void
  sg_remove_device(struct device *cl_dev, struct class_interface *cl_intf)

  {

  	struct scsi_device *scsidp = to_scsi_device(cl_dev->parent);
  	Sg_device *sdp = dev_get_drvdata(cl_dev);

  	unsigned long iflags;
  	Sg_fd *sfp;

  	int val;

  	if (!sdp)

  		return;

  	/* want sdp->detaching non-zero as soon as possible */
  	val = atomic_inc_return(&sdp->detaching);
  	if (val > 1)
  		return; /* only want to do following once per device */

  	SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,
  				      "%s
  ", __func__));

  	read_lock_irqsave(&sdp->sfd_lock, iflags);

  	list_for_each_entry(sfp, &sdp->sfds, sfd_siblings) {

  		wake_up_interruptible_all(&sfp->read_wait);

  		kill_fasync(&sfp->async_qp, SIGPOLL, POLL_HUP);

  	}

  	wake_up_interruptible_all(&sdp->open_wait);
  	read_unlock_irqrestore(&sdp->sfd_lock, iflags);

  
  	sysfs_remove_link(&scsidp->sdev_gendev.kobj, "generic");

  	device_destroy(sg_sysfs_class, MKDEV(SCSI_GENERIC_MAJOR, sdp->index));

  	cdev_del(sdp->cdev);
  	sdp->cdev = NULL;

  	kref_put(&sdp->d_ref, sg_device_destroy);

  }

  module_param_named(scatter_elem_sz, scatter_elem_sz, int, S_IRUGO | S_IWUSR);
  module_param_named(def_reserved_size, def_reserved_size, int,
  		   S_IRUGO | S_IWUSR);

  module_param_named(allow_dio, sg_allow_dio, int, S_IRUGO | S_IWUSR);
  
  MODULE_AUTHOR("Douglas Gilbert");
  MODULE_DESCRIPTION("SCSI generic (sg) driver");
  MODULE_LICENSE("GPL");
  MODULE_VERSION(SG_VERSION_STR);

  MODULE_ALIAS_CHARDEV_MAJOR(SCSI_GENERIC_MAJOR);

  MODULE_PARM_DESC(scatter_elem_sz, "scatter gather element "
                  "size (default: max(SG_SCATTER_SZ, PAGE_SIZE))");

  MODULE_PARM_DESC(def_reserved_size, "size of buffer reserved for each fd");
  MODULE_PARM_DESC(allow_dio, "allow direct I/O (default: 0 (disallow))");
  
  static int __init
  init_sg(void)
  {
  	int rc;

  	if (scatter_elem_sz < PAGE_SIZE) {
  		scatter_elem_sz = PAGE_SIZE;
  		scatter_elem_sz_prev = scatter_elem_sz;
  	}

  	if (def_reserved_size >= 0)
  		sg_big_buff = def_reserved_size;

  	else
  		def_reserved_size = sg_big_buff;

  
  	rc = register_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0), 
  				    SG_MAX_DEVS, "sg");
  	if (rc)
  		return rc;

          sg_sysfs_class = class_create(THIS_MODULE, "scsi_generic");

          if ( IS_ERR(sg_sysfs_class) ) {
  		rc = PTR_ERR(sg_sysfs_class);
  		goto err_out;
          }
  	sg_sysfs_valid = 1;
  	rc = scsi_register_interface(&sg_interface);
  	if (0 == rc) {
  #ifdef CONFIG_SCSI_PROC_FS
  		sg_proc_init();
  #endif				/* CONFIG_SCSI_PROC_FS */
  		return 0;
  	}

  	class_destroy(sg_sysfs_class);

  err_out:
  	unregister_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0), SG_MAX_DEVS);
  	return rc;
  }
  
  static void __exit
  exit_sg(void)
  {
  #ifdef CONFIG_SCSI_PROC_FS
  	sg_proc_cleanup();
  #endif				/* CONFIG_SCSI_PROC_FS */
  	scsi_unregister_interface(&sg_interface);

  	class_destroy(sg_sysfs_class);

  	sg_sysfs_valid = 0;
  	unregister_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0),
  				 SG_MAX_DEVS);

  	idr_destroy(&sg_index_idr);

  }

  static int
  sg_start_req(Sg_request *srp, unsigned char *cmd)

  {

  	int res;

  	struct request *rq;

  	struct scsi_request *req;

  	Sg_fd *sfp = srp->parentfp;
  	sg_io_hdr_t *hp = &srp->header;
  	int dxfer_len = (int) hp->dxfer_len;
  	int dxfer_dir = hp->dxfer_direction;

  	unsigned int iov_count = hp->iovec_count;

  	Sg_scatter_hold *req_schp = &srp->data;
  	Sg_scatter_hold *rsv_schp = &sfp->reserve;
  	struct request_queue *q = sfp->parentdp->device->request_queue;

  	struct rq_map_data *md, map_data;

  	int rw = hp->dxfer_direction == SG_DXFER_TO_DEV ? WRITE : READ;

  	unsigned char *long_cmdp = NULL;

  	SCSI_LOG_TIMEOUT(4, sg_printk(KERN_INFO, sfp->parentdp,
  				      "sg_start_req: dxfer_len=%d
  ",
  				      dxfer_len));

  	if (hp->cmd_len > BLK_MAX_CDB) {
  		long_cmdp = kzalloc(hp->cmd_len, GFP_KERNEL);
  		if (!long_cmdp)
  			return -ENOMEM;
  	}

  	/*
  	 * NOTE
  	 *
  	 * With scsi-mq enabled, there are a fixed number of preallocated
  	 * requests equal in number to shost->can_queue.  If all of the
  	 * preallocated requests are already in use, then using GFP_ATOMIC with
  	 * blk_get_request() will return -EWOULDBLOCK, whereas using GFP_KERNEL
  	 * will cause blk_get_request() to sleep until an active command
  	 * completes, freeing up a request.  Neither option is ideal, but
  	 * GFP_KERNEL is the better choice to prevent userspace from getting an
  	 * unexpected EWOULDBLOCK.
  	 *
  	 * With scsi-mq disabled, blk_get_request() with GFP_KERNEL usually
  	 * does not sleep except under memory pressure.
  	 */

  	rq = blk_get_request(q, hp->dxfer_direction == SG_DXFER_TO_DEV ?
  			REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN, GFP_KERNEL);

  	if (IS_ERR(rq)) {

  		kfree(long_cmdp);

  		return PTR_ERR(rq);

  	}

  	req = scsi_req(rq);

  	if (hp->cmd_len > BLK_MAX_CDB)

  		req->cmd = long_cmdp;
  	memcpy(req->cmd, cmd, hp->cmd_len);
  	req->cmd_len = hp->cmd_len;

  
  	srp->rq = rq;
  	rq->end_io_data = srp;

  	req->retries = SG_DEFAULT_RETRIES;

  	if ((dxfer_len <= 0) || (dxfer_dir == SG_DXFER_NONE))

  		return 0;