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sg.c

/*
 *  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 - 2005 Douglas Gilbert
 *
 *  Modified  19-JAN-1998  Richard Gooch <rgooch@atnf.csiro.au>  Devfs support
 *
 * 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 = 30534;  /* 2 digits for each component */
#define SG_VERSION_STR "3.5.34"

/*
 *  D. P. Gilbert (dgilbert@interlog.com, dougg@triode.net.au), 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/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/smp_lock.h>

#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 = "20061027";

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

#define SG_ALLOW_DIO_DEF 0

#define SG_MAX_DEVS 32768

/*
 * Suppose you want to calculate the formula muldiv(x,m,d)=int(x * m / d)
 * Then when using 32 bit integers x * m may overflow during the calculation.
 * Replacing muldiv(x) by muldiv(x)=((x % d) * m) / d + int(x / d) * m
 * calculates the same, but prevents the overflow when both m and d
 * are "small" numbers (like HZ and USER_HZ).
 * Of course an overflow is inavoidable if the result of muldiv doesn't fit
 * in 32 bits.
 */
#define MULDIV(X,MUL,DIV) ((((X % DIV) * MUL) / DIV) + ((X / DIV) * MUL))

#define SG_DEFAULT_TIMEOUT MULDIV(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(struct device *, struct class_interface *);
static void sg_remove(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,
      .remove_dev = sg_remove,
};

00114 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;

00127 typedef struct sg_request {   /* SG_MAX_QUEUE requests outstanding per file */
      struct sg_request *nextrp;    /* NULL -> tail request (slist) */
      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 */
      volatile char done;     /* 0->before bh, 1->before read, 2->read */
      struct request *rq;
      struct bio *bio;
      struct execute_work ew;
} Sg_request;

00142 typedef struct sg_fd {        /* holds the state of a file descriptor */
      struct list_head sfd_siblings;
      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 */
      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 */
      unsigned save_scat_len; /* original length of trunc. scat. element */
      Sg_request *headrp;     /* head of request slist, NULL->empty */
      struct fasync_struct *async_qp;     /* used by asynchronous notification */
      Sg_request req_arr[SG_MAX_QUEUE];   /* used as singly-linked list */
      char low_dma;           /* as in parent but possibly overridden to 1 */
      char force_packid;      /* 1 -> pack_id input to read(), 0 -> ignored */
      volatile char closed;   /* 1 -> fd closed but request(s) outstanding */
      char cmd_q;       /* 1 -> allow command queuing, 0 -> don't */
      char next_cmd_len;      /* 0 -> automatic (def), >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 */
      struct kref f_ref;
      struct execute_work ew;
} Sg_fd;

00165 typedef struct sg_device { /* holds the state of each scsi generic device */
      struct scsi_device *device;
      wait_queue_head_t o_excl_wait;      /* queue open() when O_EXCL in use */
      int sg_tablesize; /* adapter's max scatter-gather table size */
      u32 index;        /* device index number */
      struct list_head sfds;
      volatile char detached; /* 0->attached, 1->detached pending removal */
      volatile char exclude;  /* opened for exclusive access */
      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, int uptodate);
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_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, int dev);
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 int sg_res_in_use(Sg_fd * sfp);
static Sg_device *sg_get_dev(int dev);
static void sg_put_dev(Sg_device *sdp);

#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)

static int sg_allow_access(struct file *filp, unsigned char *cmd)
{
      struct sg_fd *sfp = (struct sg_fd *)filp->private_data;

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

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

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 res;
      int retval;

      lock_kernel();
      nonseekable_open(inode, filp);
      SCSI_LOG_TIMEOUT(3, printk("sg_open: dev=%d, flags=0x%x\n", dev, flags));
      sdp = sg_get_dev(dev);
      if (IS_ERR(sdp)) {
            retval = PTR_ERR(sdp);
            sdp = NULL;
            goto sg_put;
      }

      /* 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;

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

      if (flags & O_EXCL) {
            if (O_RDONLY == (flags & O_ACCMODE)) {
                  retval = -EPERM; /* Can't lock it with read only access */
                  goto error_out;
            }
            if (!list_empty(&sdp->sfds) && (flags & O_NONBLOCK)) {
                  retval = -EBUSY;
                  goto error_out;
            }
            res = 0;
            __wait_event_interruptible(sdp->o_excl_wait,
                                 ((!list_empty(&sdp->sfds) || sdp->exclude) ? 0 : (sdp->exclude = 1)), res);
            if (res) {
                  retval = res;     /* -ERESTARTSYS because signal hit process */
                  goto error_out;
            }
      } else if (sdp->exclude) {    /* some other fd has an exclusive lock on dev */
            if (flags & O_NONBLOCK) {
                  retval = -EBUSY;
                  goto error_out;
            }
            res = 0;
            __wait_event_interruptible(sdp->o_excl_wait, (!sdp->exclude),
                                 res);
            if (res) {
                  retval = res;     /* -ERESTARTSYS because signal hit process */
                  goto error_out;
            }
      }
      if (sdp->detached) {
            retval = -ENODEV;
            goto error_out;
      }
      if (list_empty(&sdp->sfds)) { /* no existing opens on this device */
            sdp->sgdebug = 0;
            q = sdp->device->request_queue;
            sdp->sg_tablesize = min(queue_max_hw_segments(q),
                              queue_max_phys_segments(q));
      }
      if ((sfp = sg_add_sfp(sdp, dev)))
            filp->private_data = sfp;
      else {
            if (flags & O_EXCL) {
                  sdp->exclude = 0; /* undo if error */
                  wake_up_interruptible(&sdp->o_excl_wait);
            }
            retval = -ENOMEM;
            goto error_out;
      }
      retval = 0;
error_out:
      if (retval)
            scsi_device_put(sdp->device);
sg_put:
      if (sdp)
            sg_put_dev(sdp);
      unlock_kernel();
      return retval;
}

/* Following function was formerly called 'sg_close' */
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, printk("sg_release: %s\n", sdp->disk->disk_name));

      sfp->closed = 1;

      sdp->exclude = 0;
      wake_up_interruptible(&sdp->o_excl_wait);

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

      if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
            return -ENXIO;
      SCSI_LOG_TIMEOUT(3, printk("sg_read: %s, count=%d\n",
                           sdp->disk->disk_name, (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 (sdp->detached) {
                  retval = -ENODEV;
                  goto free_old_hdr;
            }
            if (filp->f_flags & O_NONBLOCK) {
                  retval = -EAGAIN;
                  goto free_old_hdr;
            }
            while (1) {
                  retval = 0; /* following macro beats race condition */
                  __wait_event_interruptible(sfp->read_wait,
                        (sdp->detached ||
                        (srp = sg_get_rq_mark(sfp, req_pack_id))), 
                        retval);
                  if (sdp->detached) {
                        retval = -ENODEV;
                        goto free_old_hdr;
                  }
                  if (0 == retval)
                        break;

                  /* -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);
      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;
      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:
      err = sg_finish_rem_req(srp);
      return (0 == err) ? count : err;
}

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[MAX_COMMAND_SIZE];

      if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
            return -ENXIO;
      SCSI_LOG_TIMEOUT(3, printk("sg_write: %s, count=%d\n",
                           sdp->disk->disk_name, (int) count));
      if (sdp->detached)
            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, printk("sg_write: queue full\n"));
            return -EDOM;
      }
      buf += SZ_SG_HEADER;
      __get_user(opcode, buf);
      if (sfp->next_cmd_len > 0) {
            if (sfp->next_cmd_len > MAX_COMMAND_SIZE) {
                  SCSI_LOG_TIMEOUT(1, printk("sg_write: command length too long\n"));
                  sfp->next_cmd_len = 0;
                  sg_remove_request(sfp, srp);
                  return -EIO;
            }
            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;
      }
      SCSI_LOG_TIMEOUT(4, printk(
            "sg_write:   scsi opcode=0x%02x, cmd_size=%d\n", (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->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) {
            static char cmd[TASK_COMM_LEN];
            if (strcmp(current->comm, cmd) && printk_ratelimit()) {
                  printk(KERN_WARNING
                         "sg_write: data in/out %d/%d bytes for SCSI command 0x%x--"
                         "guessing data in;\n   "
                         "program %s not setting count and/or reply_len properly\n",
                         old_hdr.reply_len - (int)SZ_SG_HEADER,
                         input_size, (unsigned int) cmnd[0],
                         current->comm);
                  strcpy(cmd, 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[MAX_COMMAND_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, printk("sg_new_write: queue full\n"));
            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 (sg_res_in_use(sfp)) {
                  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, data_dir;
      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, printk("sg_common_write:  scsi opcode=0x%02x, cmd_size=%d\n",
                    (int) cmnd[0], (int) hp->cmd_len));

      k = sg_start_req(srp, cmnd);
      if (k) {
            SCSI_LOG_TIMEOUT(1, printk("sg_common_write: start_req err=%d\n", k));
            sg_finish_rem_req(srp);
            return k;   /* probably out of space --> ENOMEM */
      }
      if (sdp->detached) {
            sg_finish_rem_req(srp);
            return -ENODEV;
      }

      switch (hp->dxfer_direction) {
      case SG_DXFER_TO_FROM_DEV:
      case SG_DXFER_FROM_DEV:
            data_dir = DMA_FROM_DEVICE;
            break;
      case SG_DXFER_TO_DEV:
            data_dir = DMA_TO_DEVICE;
            break;
      case SG_DXFER_UNKNOWN:
            data_dir = DMA_BIDIRECTIONAL;
            break;
      default:
            data_dir = DMA_NONE;
            break;
      }
      hp->duration = jiffies_to_msecs(jiffies);

      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, 1, sg_rq_end_io);
      return 0;
}

static int
sg_ioctl(struct inode *inode, 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, printk("sg_ioctl: %s, cmd=0x%x\n",
                           sdp->disk->disk_name, (int) cmd_in));
      read_only = (O_RDWR != (filp->f_flags & O_ACCMODE));

      switch (cmd_in) {
      case SG_IO:
            {
                  int blocking = 1; /* ignore O_NONBLOCK flag */

                  if (sdp->detached)
                        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,
                               blocking, read_only, 1, &srp);
                  if (result < 0)
                        return result;
                  while (1) {
                        result = 0; /* following macro to beat race condition */
                        __wait_event_interruptible(sfp->read_wait,
                              (srp->done || sdp->detached),
                              result);
                        if (sdp->detached)
                              return -ENODEV;
                        write_lock_irq(&sfp->rq_list_lock);
                        if (srp->done) {
                              srp->done = 2;
                              write_unlock_irq(&sfp->rq_list_lock);
                              break;
                        }
                        srp->orphan = 1;
                        write_unlock_irq(&sfp->rq_list_lock);
                        return result;    /* -ERESTARTSYS because signal hit process */
                  }
                  result = sg_new_read(sfp, p, SZ_SG_IO_HDR, srp);
                  return (result < 0) ? result : 0;
            }
      case SG_SET_TIMEOUT:
            result = get_user(val, ip);
            if (result)
                  return result;
            if (val < 0)
                  return -EIO;
            if (val >= MULDIV (INT_MAX, USER_HZ, HZ))
                val = MULDIV (INT_MAX, USER_HZ, HZ);
            sfp->timeout_user = val;
            sfp->timeout = MULDIV (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:
            result = get_user(val, ip);
            if (result)
                  return result;
            if (val) {
                  sfp->low_dma = 1;
                  if ((0 == sfp->low_dma) && (0 == sg_res_in_use(sfp))) {
                        val = (int) sfp->reserve.bufflen;
                        sg_remove_scat(&sfp->reserve);
                        sg_build_reserve(sfp, val);
                  }
            } else {
                  if (sdp->detached)
                        return -ENODEV;
                  sfp->low_dma = sdp->device->host->unchecked_isa_dma;
            }
            return 0;
      case SG_GET_LOW_DMA:
            return put_user((int) sfp->low_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 (sdp->detached)
                        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);
            for (srp = sfp->headrp; srp; srp = srp->nextrp) {
                  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);
            for (val = 0, srp = sfp->headrp; srp; srp = srp->nextrp) {
                  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,
                      queue_max_sectors(sdp->device->request_queue) * 512);
            if (val != sfp->reserve.bufflen) {
                  if (sg_res_in_use(sfp) || sfp->mmap_called)
                        return -EBUSY;
                  sg_remove_scat(&sfp->reserve);
                  sg_build_reserve(sfp, val);
            }
            return 0;
      case SG_GET_RESERVED_SIZE:
            val = min_t(int, sfp->reserve.bufflen,
                      queue_max_sectors(sdp->device->request_queue) * 512);
            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;
            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;
                  unsigned int ms;

                  rinfo = kmalloc(SZ_SG_REQ_INFO * SG_MAX_QUEUE,
                                                GFP_KERNEL);
                  if (!rinfo)
                        return -ENOMEM;
                  read_lock_irqsave(&sfp->rq_list_lock, iflags);
                  for (srp = sfp->headrp, val = 0; val < SG_MAX_QUEUE;
                       ++val, srp = srp ? srp->nextrp : srp) {
                        memset(&rinfo[val], 0, SZ_SG_REQ_INFO);
                        if (srp) {
                              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;
                        }
                  }
                  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 (sdp->detached)
                  return -ENODEV;
            return put_user(sdp->device->host->hostt->emulated, ip);
      case SG_SCSI_RESET:
            if (sdp->detached)
                  return -ENODEV;
            if (filp->f_flags & O_NONBLOCK) {
                  if (scsi_host_in_recovery(sdp->device->host))
                        return -EBUSY;
            } else if (!scsi_block_when_processing_errors(sdp->device))
                  return -EBUSY;
            result = get_user(val, ip);
            if (result)
                  return result;
            if (SG_SCSI_RESET_NOTHING == val)
                  return 0;
            switch (val) {
            case SG_SCSI_RESET_DEVICE:
                  val = SCSI_TRY_RESET_DEVICE;
                  break;
            case SG_SCSI_RESET_TARGET:
                  val = SCSI_TRY_RESET_TARGET;
                  break;
            case SG_SCSI_RESET_BUS:
                  val = SCSI_TRY_RESET_BUS;
                  break;
            case SG_SCSI_RESET_HOST:
                  val = SCSI_TRY_RESET_HOST;
                  break;
            default:
                  return -EINVAL;
            }
            if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                  return -EACCES;
            return (scsi_reset_provider(sdp->device, val) ==
                  SUCCESS) ? 0 : -EIO;
      case SCSI_IOCTL_SEND_COMMAND:
            if (sdp->detached)
                  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 SCSI_IOCTL_GET_IDLUN:
      case SCSI_IOCTL_GET_BUS_NUMBER:
      case SCSI_IOCTL_PROBE_HOST:
      case SG_GET_TRANSFORM:
            if (sdp->detached)
                  return -ENODEV;
            return scsi_ioctl(sdp->device, cmd_in, p);
      case BLKSECTGET:
            return put_user(queue_max_sectors(sdp->device->request_queue) * 512,
                        ip);
      case BLKTRACESETUP:
            return blk_trace_setup(sdp->device->request_queue,
                               sdp->disk->disk_name,
                               MKDEV(SCSI_GENERIC_MAJOR, sdp->index),
                               NULL,
                               (char *)arg);
      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);
      default:
            if (read_only)
                  return -EPERM;    /* don't know so take safe approach */
            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;

      if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp))
          || sfp->closed)
            return POLLERR;
      poll_wait(filp, &sfp->read_wait, wait);
      read_lock_irqsave(&sfp->rq_list_lock, iflags);
      for (srp = sfp->headrp; srp; srp = srp->nextrp) {
            /* 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 (sdp->detached)
            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, printk("sg_poll: %s, res=0x%x\n",
                           sdp->disk->disk_name, (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, printk("sg_fasync: %s, mode=%d\n",
                           sdp->disk->disk_name, mode));

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

static int
sg_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
      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, printk("sg_vma_fault: offset=%lu, scatg=%d\n",
                           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 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;

      if ((!filp) || (!vma) || (!(sfp = (Sg_fd *) filp->private_data)))
            return -ENXIO;
      req_sz = vma->vm_end - vma->vm_start;
      SCSI_LOG_TIMEOUT(3, printk("sg_mmap starting, vm_start=%p, len=%d\n",
                           (void *) vma->vm_start, (int) req_sz));
      if (vma->vm_pgoff)
            return -EINVAL;   /* want no offset */
      rsv_schp = &sfp->reserve;
      if (req_sz > rsv_schp->bufflen)
            return -ENOMEM;   /* cannot map more than reserved buffer */

      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_RESERVED;
      vma->vm_private_data = sfp;
      vma->vm_ops = &sg_mmap_vm_ops;
      return 0;
}

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);
      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, int uptodate)
{
      struct sg_request *srp = rq->end_io_data;
      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(sdp->detached))
            printk(KERN_INFO "sg_rq_end_io: device detached\n");

      sense = rq->sense;
      result = rq->errors;
      resid = rq->resid_len;

      SCSI_LOG_TIMEOUT(4, printk("sg_cmd_done: %s, pack_id=%d, res=0x%x\n",
            sdp->disk->disk_name, 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("sg_cmd_done", 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;
            }
      }
      /* Rely on write phase to clean out srp status values, so no "else" */

      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 struct file_operations sg_fops = {
      .owner = THIS_MODULE,
      .read = sg_read,
      .write = sg_write,
      .poll = sg_poll,
      .ioctl = sg_ioctl,
#ifdef CONFIG_COMPAT
      .compat_ioctl = sg_compat_ioctl,
#endif
      .open = sg_open,
      .mmap = sg_mmap,
      .release = sg_release,
      .fasync = sg_fasync,
};

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) {
            printk(KERN_WARNING "kmalloc Sg_device failure\n");
            return ERR_PTR(-ENOMEM);
      }

      if (!idr_pre_get(&sg_index_idr, GFP_KERNEL)) {
            printk(KERN_WARNING "idr expansion Sg_device failure\n");
            error = -ENOMEM;
            goto out;
      }

      write_lock_irqsave(&sg_index_lock, iflags);

      error = idr_get_new(&sg_index_idr, sdp, &k);
      if (error) {
            write_unlock_irqrestore(&sg_index_lock, iflags);
            printk(KERN_WARNING "idr allocation Sg_device failure: %d\n",
                   error);
            goto out;
      }

      if (unlikely(k >= SG_MAX_DEVS))
            goto overflow;

      SCSI_LOG_TIMEOUT(3, printk("sg_alloc: dev=%d \n", k));
      sprintf(disk->disk_name, "sg%d", k);
      disk->first_minor = k;
      sdp->disk = disk;
      sdp->device = scsidp;
      INIT_LIST_HEAD(&sdp->sfds);
      init_waitqueue_head(&sdp->o_excl_wait);
      sdp->sg_tablesize = min(queue_max_hw_segments(q),
                        queue_max_phys_segments(q));
      sdp->index = k;
      kref_init(&sdp->d_ref);

      write_unlock_irqrestore(&sg_index_lock, iflags);

      error = 0;
 out:
      if (error) {
            kfree(sdp);
            return ERR_PTR(error);
      }
      return sdp;

 overflow:
      idr_remove(&sg_index_idr, k);
      write_unlock_irqrestore(&sg_index_lock, iflags);
      sdev_printk(KERN_WARNING, scsidp,
                "Unable to attach sg device type=%d, minor "
                "number exceeds %d\n", scsidp->type, SG_MAX_DEVS - 1);
      error = -ENODEV;
      goto out;
}

static int
sg_add(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) {
            printk(KERN_WARNING "alloc_disk failed\n");
            return -ENOMEM;
      }
      disk->major = SCSI_GENERIC_MAJOR;

      error = -ENOMEM;
      cdev = cdev_alloc();
      if (!cdev) {
            printk(KERN_WARNING "cdev_alloc failed\n");
            goto out;
      }
      cdev->owner = THIS_MODULE;
      cdev->ops = &sg_fops;

      sdp = sg_alloc(disk, scsidp);
      if (IS_ERR(sdp)) {
            printk(KERN_WARNING "sg_alloc failed\n");
            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)) {
                  printk(KERN_ERR "sg_add: "
                         "device_create failed\n");
                  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)
                  printk(KERN_ERR "sg_add: unable to make symlink "
                              "'generic' back to sg%d\n", sdp->index);
      } else
            printk(KERN_WARNING "sg_add: sg_sys Invalid\n");

      sdev_printk(KERN_NOTICE, scsidp,
                "Attached scsi generic sg%d type %d\n", 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,
            printk("sg_device_destroy: %s\n",
                  sdp->disk->disk_name));

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

static void sg_remove(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;

      if (!sdp || sdp->detached)
            return;

      SCSI_LOG_TIMEOUT(3, printk("sg_remove: %s\n", sdp->disk->disk_name));

      /* Need a write lock to set sdp->detached. */
      write_lock_irqsave(&sg_index_lock, iflags);
      sdp->detached = 1;
      list_for_each_entry(sfp, &sdp->sfds, sfd_siblings) {
            wake_up_interruptible(&sfp->read_wait);
            kill_fasync(&sfp->async_qp, SIGPOLL, POLL_HUP);
      }
      write_unlock_irqrestore(&sg_index_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;

      sg_put_dev(sdp);
}

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;
      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;

      SCSI_LOG_TIMEOUT(4, printk(KERN_INFO "sg_start_req: dxfer_len=%d\n",
                           dxfer_len));

      rq = blk_get_request(q, rw, GFP_ATOMIC);
      if (!rq)
            return -ENOMEM;

      memcpy(rq->cmd, cmd, hp->cmd_len);

      rq->cmd_len = hp->cmd_len;
      rq->cmd_type = REQ_TYPE_BLOCK_PC;

      srp->rq = rq;
      rq->end_io_data = srp;
      rq->sense = srp->sense_b;
      rq->retries = SG_DEFAULT_RETRIES;

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

      if (sg_allow_dio && hp->flags & SG_FLAG_DIRECT_IO &&
          dxfer_dir != SG_DXFER_UNKNOWN && !iov_count &&
          !sfp->parentdp->device->host->unchecked_isa_dma &&
          blk_rq_aligned(q, hp->dxferp, dxfer_len))
            md = NULL;
      else
            md = &map_data;

      if (md) {
            if (!sg_res_in_use(sfp) && dxfer_len <= rsv_schp->bufflen)
                  sg_link_reserve(sfp, srp, dxfer_len);
            else {
                  res = sg_build_indirect(req_schp, sfp, dxfer_len);
                  if (res)
                        return res;
            }

            md->pages = req_schp->pages;
            md->page_order = req_schp->page_order;
            md->nr_entries = req_schp->k_use_sg;
            md->offset = 0;
            md->null_mapped = hp->dxferp ? 0 : 1;
            if (dxfer_dir == SG_DXFER_TO_FROM_DEV)
                  md->from_user = 1;
            else
                  md->from_user = 0;
      }

      if (iov_count) {
            int len, size = sizeof(struct sg_iovec) * iov_count;
            struct iovec *iov;

            iov = kmalloc(size, GFP_ATOMIC);
            if (!iov)
                  return -ENOMEM;

            if (copy_from_user(iov, hp->dxferp, size)) {
                  kfree(iov);
                  return -EFAULT;
            }

            len = iov_length(iov, iov_count);
            if (hp->dxfer_len < len) {
                  iov_count = iov_shorten(iov, iov_count, hp->dxfer_len);
                  len = hp->dxfer_len;
            }

            res = blk_rq_map_user_iov(q, rq, md, (struct sg_iovec *)iov,
                                iov_count,
                                len, GFP_ATOMIC);
            kfree(iov);
      } else
            res = blk_rq_map_user(q, rq, md, hp->dxferp,
                              hp->dxfer_len, GFP_ATOMIC);

      if (!res) {
            srp->bio = rq->bio;

            if (!md) {
                  req_schp->dio_in_use = 1;
                  hp->info |= SG_INFO_DIRECT_IO;
            }
      }
      return res;
}

static int sg_finish_rem_req(Sg_request * srp)
{
      int ret = 0;

      Sg_fd *sfp = srp->parentfp;
      Sg_scatter_hold *req_schp = &srp->data;

      SCSI_LOG_TIMEOUT(4, printk("sg_finish_rem_req: res_used=%d\n", (int) srp->res_used));
      if (srp->res_used)
            sg_unlink_reserve(sfp, srp);
      else
            sg_remove_scat(req_schp);

      if (srp->rq) {
            if (srp->bio)
                  ret = blk_rq_unmap_user(srp->bio);

            blk_put_request(srp->rq);
      }

      sg_remove_request(sfp, srp);

      return ret;
}

static int
sg_build_sgat(Sg_scatter_hold * schp, const Sg_fd * sfp, int tablesize)
{
      int sg_bufflen = tablesize * sizeof(struct page *);
      gfp_t gfp_flags = GFP_ATOMIC | __GFP_NOWARN;

      schp->pages = kzalloc(sg_bufflen, gfp_flags);
      if (!schp->pages)
            return -ENOMEM;
      schp->sglist_len = sg_bufflen;
      return tablesize; /* number of scat_gath elements allocated */
}

static int
sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size)
{
      int ret_sz = 0, i, k, rem_sz, num, mx_sc_elems;
      int sg_tablesize = sfp->parentdp->sg_tablesize;
      int blk_size = buff_size, order;
      gfp_t gfp_mask = GFP_ATOMIC | __GFP_COMP | __GFP_NOWARN;

      if (blk_size < 0)
            return -EFAULT;
      if (0 == blk_size)
            ++blk_size; /* don't know why */
      /* round request up to next highest SG_SECTOR_SZ byte boundary */
      blk_size = ALIGN(blk_size, SG_SECTOR_SZ);
      SCSI_LOG_TIMEOUT(4, printk("sg_build_indirect: buff_size=%d, blk_size=%d\n",
                           buff_size, blk_size));

      /* N.B. ret_sz carried into this block ... */
      mx_sc_elems = sg_build_sgat(schp, sfp, sg_tablesize);
      if (mx_sc_elems < 0)
            return mx_sc_elems;     /* most likely -ENOMEM */

      num = scatter_elem_sz;
      if (unlikely(num != scatter_elem_sz_prev)) {
            if (num < PAGE_SIZE) {
                  scatter_elem_sz = PAGE_SIZE;
                  scatter_elem_sz_prev = PAGE_SIZE;
            } else
                  scatter_elem_sz_prev = num;
      }

      if (sfp->low_dma)
            gfp_mask |= GFP_DMA;

      if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
            gfp_mask |= __GFP_ZERO;

      order = get_order(num);
retry:
      ret_sz = 1 << (PAGE_SHIFT + order);

      for (k = 0, rem_sz = blk_size; rem_sz > 0 && k < mx_sc_elems;
           k++, rem_sz -= ret_sz) {

            num = (rem_sz > scatter_elem_sz_prev) ?
                  scatter_elem_sz_prev : rem_sz;

            schp->pages[k] = alloc_pages(gfp_mask, order);
            if (!schp->pages[k])
                  goto out;

            if (num == scatter_elem_sz_prev) {
                  if (unlikely(ret_sz > scatter_elem_sz_prev)) {
                        scatter_elem_sz = ret_sz;
                        scatter_elem_sz_prev = ret_sz;
                  }
            }

            SCSI_LOG_TIMEOUT(5, printk("sg_build_indirect: k=%d, num=%d, "
                         "ret_sz=%d\n", k, num, ret_sz));
      }           /* end of for loop */

      schp->page_order = order;
      schp->k_use_sg = k;
      SCSI_LOG_TIMEOUT(5, printk("sg_build_indirect: k_use_sg=%d, "
                   "rem_sz=%d\n", k, rem_sz));

      schp->bufflen = blk_size;
      if (rem_sz > 0)   /* must have failed */
            return -ENOMEM;
      return 0;
out:
      for (i = 0; i < k; i++)
            __free_pages(schp->pages[k], order);

      if (--order >= 0)
            goto retry;

      return -ENOMEM;
}

static void
sg_remove_scat(Sg_scatter_hold * schp)
{
      SCSI_LOG_TIMEOUT(4, printk("sg_remove_scat: k_use_sg=%d\n", schp->k_use_sg));
      if (schp->pages && schp->sglist_len > 0) {
            if (!schp->dio_in_use) {
                  int k;

                  for (k = 0; k < schp->k_use_sg && schp->pages[k]; k++) {
                        SCSI_LOG_TIMEOUT(5, printk(
                            "sg_remove_scat: k=%d, pg=0x%p\n",
                            k, schp->pages[k]));
                        __free_pages(schp->pages[k], schp->page_order);
                  }

                  kfree(schp->pages);
            }
      }
      memset(schp, 0, sizeof (*schp));
}

static int
sg_read_oxfer(Sg_request * srp, char __user *outp, int num_read_xfer)
{
      Sg_scatter_hold *schp = &srp->data;
      int k, num;

      SCSI_LOG_TIMEOUT(4, printk("sg_read_oxfer: num_read_xfer=%d\n",
                           num_read_xfer));
      if ((!outp) || (num_read_xfer <= 0))
            return 0;

      num = 1 << (PAGE_SHIFT + schp->page_order);
      for (k = 0; k < schp->k_use_sg && schp->pages[k]; k++) {
            if (num > num_read_xfer) {
                  if (__copy_to_user(outp, page_address(schp->pages[k]),
                                 num_read_xfer))
                        return -EFAULT;
                  break;
            } else {
                  if (__copy_to_user(outp, page_address(schp->pages[k]),
                                 num))
                        return -EFAULT;
                  num_read_xfer -= num;
                  if (num_read_xfer <= 0)
                        break;
                  outp += num;
            }
      }

      return 0;
}

static void
sg_build_reserve(Sg_fd * sfp, int req_size)
{
      Sg_scatter_hold *schp = &sfp->reserve;

      SCSI_LOG_TIMEOUT(4, printk("sg_build_reserve: req_size=%d\n", req_size));
      do {
            if (req_size < PAGE_SIZE)
                  req_size = PAGE_SIZE;
            if (0 == sg_build_indirect(schp, sfp, req_size))
                  return;
            else
                  sg_remove_scat(schp);
            req_size >>= 1;   /* divide by 2 */
      } while (req_size > (PAGE_SIZE / 2));
}

static void
sg_link_reserve(Sg_fd * sfp, Sg_request * srp, int size)
{
      Sg_scatter_hold *req_schp = &srp->data;
      Sg_scatter_hold *rsv_schp = &sfp->reserve;
      int k, num, rem;

      srp->res_used = 1;
      SCSI_LOG_TIMEOUT(4, printk("sg_link_reserve: size=%d\n", size));
      rem = size;

      num = 1 << (PAGE_SHIFT + rsv_schp->page_order);
      for (k = 0; k < rsv_schp->k_use_sg; k++) {
            if (rem <= num) {
                  req_schp->k_use_sg = k + 1;
                  req_schp->sglist_len = rsv_schp->sglist_len;
                  req_schp->pages = rsv_schp->pages;

                  req_schp->bufflen = size;
                  req_schp->page_order = rsv_schp->page_order;
                  break;
            } else
                  rem -= num;
      }

      if (k >= rsv_schp->k_use_sg)
            SCSI_LOG_TIMEOUT(1, printk("sg_link_reserve: BAD size\n"));
}

static void
sg_unlink_reserve(Sg_fd * sfp, Sg_request * srp)
{
      Sg_scatter_hold *req_schp = &srp->data;

      SCSI_LOG_TIMEOUT(4, printk("sg_unlink_reserve: req->k_use_sg=%d\n",
                           (int) req_schp->k_use_sg));
      req_schp->k_use_sg = 0;
      req_schp->bufflen = 0;
      req_schp->pages = NULL;
      req_schp->page_order = 0;
      req_schp->sglist_len = 0;
      sfp->save_scat_len = 0;
      srp->res_used = 0;
}

static Sg_request *
sg_get_rq_mark(Sg_fd * sfp, int pack_id)
{
      Sg_request *resp;
      unsigned long iflags;

      write_lock_irqsave(&sfp->rq_list_lock, iflags);
      for (resp = sfp->headrp; resp; resp = resp->nextrp) {
            /* look for requests that are ready + not SG_IO owned */
            if ((1 == resp->done) && (!resp->sg_io_owned) &&
                ((-1 == pack_id) || (resp->header.pack_id == pack_id))) {
                  resp->done = 2;   /* guard against other readers */
                  break;
            }
      }
      write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
      return resp;
}

/* always adds to end of list */
static Sg_request *
sg_add_request(Sg_fd * sfp)
{
      int k;
      unsigned long iflags;
      Sg_request *resp;
      Sg_request *rp = sfp->req_arr;

      write_lock_irqsave(&sfp->rq_list_lock, iflags);
      resp = sfp->headrp;
      if (!resp) {
            memset(rp, 0, sizeof (Sg_request));
            rp->parentfp = sfp;
            resp = rp;
            sfp->headrp = resp;
      } else {
            if (0 == sfp->cmd_q)
                  resp = NULL;      /* command queuing disallowed */
            else {
                  for (k = 0; k < SG_MAX_QUEUE; ++k, ++rp) {
                        if (!rp->parentfp)
                              break;
                  }
                  if (k < SG_MAX_QUEUE) {
                        memset(rp, 0, sizeof (Sg_request));
                        rp->parentfp = sfp;
                        while (resp->nextrp)
                              resp = resp->nextrp;
                        resp->nextrp = rp;
                        resp = rp;
                  } else
                        resp = NULL;
            }
      }
      if (resp) {
            resp->nextrp = NULL;
            resp->header.duration = jiffies_to_msecs(jiffies);
      }
      write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
      return resp;
}

/* Return of 1 for found; 0 for not found */
static int
sg_remove_request(Sg_fd * sfp, Sg_request * srp)
{
      Sg_request *prev_rp;
      Sg_request *rp;
      unsigned long iflags;
      int res = 0;

      if ((!sfp) || (!srp) || (!sfp->headrp))
            return res;
      write_lock_irqsave(&sfp->rq_list_lock, iflags);
      prev_rp = sfp->headrp;
      if (srp == prev_rp) {
            sfp->headrp = prev_rp->nextrp;
            prev_rp->parentfp = NULL;
            res = 1;
      } else {
            while ((rp = prev_rp->nextrp)) {
                  if (srp == rp) {
                        prev_rp->nextrp = rp->nextrp;
                        rp->parentfp = NULL;
                        res = 1;
                        break;
                  }
                  prev_rp = rp;
            }
      }
      write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
      return res;
}

static Sg_fd *
sg_add_sfp(Sg_device * sdp, int dev)
{
      Sg_fd *sfp;
      unsigned long iflags;
      int bufflen;

      sfp = kzalloc(sizeof(*sfp), GFP_ATOMIC | __GFP_NOWARN);
      if (!sfp)
            return NULL;

      init_waitqueue_head(&sfp->read_wait);
      rwlock_init(&sfp->rq_list_lock);

      kref_init(&sfp->f_ref);
      sfp->timeout = SG_DEFAULT_TIMEOUT;
      sfp->timeout_user = SG_DEFAULT_TIMEOUT_USER;
      sfp->force_packid = SG_DEF_FORCE_PACK_ID;
      sfp->low_dma = (SG_DEF_FORCE_LOW_DMA == 0) ?
          sdp->device->host->unchecked_isa_dma : 1;
      sfp->cmd_q = SG_DEF_COMMAND_Q;
      sfp->keep_orphan = SG_DEF_KEEP_ORPHAN;
      sfp->parentdp = sdp;
      write_lock_irqsave(&sg_index_lock, iflags);
      list_add_tail(&sfp->sfd_siblings, &sdp->sfds);
      write_unlock_irqrestore(&sg_index_lock, iflags);
      SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: sfp=0x%p\n", sfp));
      if (unlikely(sg_big_buff != def_reserved_size))
            sg_big_buff = def_reserved_size;

      bufflen = min_t(int, sg_big_buff,
                  queue_max_sectors(sdp->device->request_queue) * 512);
      sg_build_reserve(sfp, bufflen);
      SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp:   bufflen=%d, k_use_sg=%d\n",
                     sfp->reserve.bufflen, sfp->reserve.k_use_sg));

      kref_get(&sdp->d_ref);
      __module_get(THIS_MODULE);
      return sfp;
}

static void sg_remove_sfp_usercontext(struct work_struct *work)
{
      struct sg_fd *sfp = container_of(work, struct sg_fd, ew.work);
      struct sg_device *sdp = sfp->parentdp;

      /* Cleanup any responses which were never read(). */
      while (sfp->headrp)
            sg_finish_rem_req(sfp->headrp);

      if (sfp->reserve.bufflen > 0) {
            SCSI_LOG_TIMEOUT(6,
                  printk("sg_remove_sfp:    bufflen=%d, k_use_sg=%d\n",
                        (int) sfp->reserve.bufflen,
                        (int) sfp->reserve.k_use_sg));
            sg_remove_scat(&sfp->reserve);
      }

      SCSI_LOG_TIMEOUT(6,
            printk("sg_remove_sfp: %s, sfp=0x%p\n",
                  sdp->disk->disk_name,
                  sfp));
      kfree(sfp);

      scsi_device_put(sdp->device);
      sg_put_dev(sdp);
      module_put(THIS_MODULE);
}

static void sg_remove_sfp(struct kref *kref)
{
      struct sg_fd *sfp = container_of(kref, struct sg_fd, f_ref);
      struct sg_device *sdp = sfp->parentdp;
      unsigned long iflags;

      write_lock_irqsave(&sg_index_lock, iflags);
      list_del(&sfp->sfd_siblings);
      write_unlock_irqrestore(&sg_index_lock, iflags);
      wake_up_interruptible(&sdp->o_excl_wait);

      INIT_WORK(&sfp->ew.work, sg_remove_sfp_usercontext);
      schedule_work(&sfp->ew.work);
}

static int
sg_res_in_use(Sg_fd * sfp)
{
      const Sg_request *srp;
      unsigned long iflags;

      read_lock_irqsave(&sfp->rq_list_lock, iflags);
      for (srp = sfp->headrp; srp; srp = srp->nextrp)
            if (srp->res_used)
                  break;
      read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
      return srp ? 1 : 0;
}

#ifdef CONFIG_SCSI_PROC_FS
static int
sg_idr_max_id(int id, void *p, void *data)
{
      int *k = data;

      if (*k < id)
            *k = id;

      return 0;
}

static int
sg_last_dev(void)
{
      int k = -1;
      unsigned long iflags;

      read_lock_irqsave(&sg_index_lock, iflags);
      idr_for_each(&sg_index_idr, sg_idr_max_id, &k);
      read_unlock_irqrestore(&sg_index_lock, iflags);
      return k + 1;           /* origin 1 */
}
#endif

/* must be called with sg_index_lock held */
static Sg_device *sg_lookup_dev(int dev)
{
      return idr_find(&sg_index_idr, dev);
}

static Sg_device *sg_get_dev(int dev)
{
      struct sg_device *sdp;
      unsigned long flags;

      read_lock_irqsave(&sg_index_lock, flags);
      sdp = sg_lookup_dev(dev);
      if (!sdp)
            sdp = ERR_PTR(-ENXIO);
      else if (sdp->detached) {
            /* If sdp->detached, then the refcount may already be 0, in
             * which case it would be a bug to do kref_get().
             */
            sdp = ERR_PTR(-ENODEV);
      } else
            kref_get(&sdp->d_ref);
      read_unlock_irqrestore(&sg_index_lock, flags);

      return sdp;
}

static void sg_put_dev(struct sg_device *sdp)
{
      kref_put(&sdp->d_ref, sg_device_destroy);
}

#ifdef CONFIG_SCSI_PROC_FS

static struct proc_dir_entry *sg_proc_sgp = NULL;

static char sg_proc_sg_dirname[] = "scsi/sg";

static int sg_proc_seq_show_int(struct seq_file *s, void *v);

static int sg_proc_single_open_adio(struct inode *inode, struct file *file);
static ssize_t sg_proc_write_adio(struct file *filp, const char __user *buffer,
                            size_t count, loff_t *off);
static struct file_operations adio_fops = {
      /* .owner, .read and .llseek added in sg_proc_init() */
      .open = sg_proc_single_open_adio,
      .write = sg_proc_write_adio,
      .release = single_release,
};

static int sg_proc_single_open_dressz(struct inode *inode, struct file *file);
static ssize_t sg_proc_write_dressz(struct file *filp, 
            const char __user *buffer, size_t count, loff_t *off);
static struct file_operations dressz_fops = {
      .open = sg_proc_single_open_dressz,
      .write = sg_proc_write_dressz,
      .release = single_release,
};

static int sg_proc_seq_show_version(struct seq_file *s, void *v);
static int sg_proc_single_open_version(struct inode *inode, struct file *file);
static struct file_operations version_fops = {
      .open = sg_proc_single_open_version,
      .release = single_release,
};

static int sg_proc_seq_show_devhdr(struct seq_file *s, void *v);
static int sg_proc_single_open_devhdr(struct inode *inode, struct file *file);
static struct file_operations devhdr_fops = {
      .open = sg_proc_single_open_devhdr,
      .release = single_release,
};

static int sg_proc_seq_show_dev(struct seq_file *s, void *v);
static int sg_proc_open_dev(struct inode *inode, struct file *file);
static void * dev_seq_start(struct seq_file *s, loff_t *pos);
static void * dev_seq_next(struct seq_file *s, void *v, loff_t *pos);
static void dev_seq_stop(struct seq_file *s, void *v);
static struct file_operations dev_fops = {
      .open = sg_proc_open_dev,
      .release = seq_release,
};
static struct seq_operations dev_seq_ops = {
      .start = dev_seq_start,
      .next  = dev_seq_next,
      .stop  = dev_seq_stop,
      .show  = sg_proc_seq_show_dev,
};

static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v);
static int sg_proc_open_devstrs(struct inode *inode, struct file *file);
static struct file_operations devstrs_fops = {
      .open = sg_proc_open_devstrs,
      .release = seq_release,
};
static struct seq_operations devstrs_seq_ops = {
      .start = dev_seq_start,
      .next  = dev_seq_next,
      .stop  = dev_seq_stop,
      .show  = sg_proc_seq_show_devstrs,
};

static int sg_proc_seq_show_debug(struct seq_file *s, void *v);
static int sg_proc_open_debug(struct inode *inode, struct file *file);
static struct file_operations debug_fops = {
      .open = sg_proc_open_debug,
      .release = seq_release,
};
static struct seq_operations debug_seq_ops = {
      .start = dev_seq_start,
      .next  = dev_seq_next,
      .stop  = dev_seq_stop,
      .show  = sg_proc_seq_show_debug,
};


struct sg_proc_leaf {
      const char * name;
      struct file_operations * fops;
};

static struct sg_proc_leaf sg_proc_leaf_arr[] = {
      {"allow_dio", &adio_fops},
      {"debug", &debug_fops},
      {"def_reserved_size", &dressz_fops},
      {"device_hdr", &devhdr_fops},
      {"devices", &dev_fops},
      {"device_strs", &devstrs_fops},
      {"version", &version_fops}
};

static int
sg_proc_init(void)
{
      int k, mask;
      int num_leaves = ARRAY_SIZE(sg_proc_leaf_arr);
      struct sg_proc_leaf * leaf;

      sg_proc_sgp = proc_mkdir(sg_proc_sg_dirname, NULL);
      if (!sg_proc_sgp)
            return 1;
      for (k = 0; k < num_leaves; ++k) {
            leaf = &sg_proc_leaf_arr[k];
            mask = leaf->fops->write ? S_IRUGO | S_IWUSR : S_IRUGO;
            leaf->fops->owner = THIS_MODULE;
            leaf->fops->read = seq_read;
            leaf->fops->llseek = seq_lseek;
            proc_create(leaf->name, mask, sg_proc_sgp, leaf->fops);
      }
      return 0;
}

static void
sg_proc_cleanup(void)
{
      int k;
      int num_leaves = ARRAY_SIZE(sg_proc_leaf_arr);

      if (!sg_proc_sgp)
            return;
      for (k = 0; k < num_leaves; ++k)
            remove_proc_entry(sg_proc_leaf_arr[k].name, sg_proc_sgp);
      remove_proc_entry(sg_proc_sg_dirname, NULL);
}


static int sg_proc_seq_show_int(struct seq_file *s, void *v)
{
      seq_printf(s, "%d\n", *((int *)s->private));
      return 0;
}

static int sg_proc_single_open_adio(struct inode *inode, struct file *file)
{
      return single_open(file, sg_proc_seq_show_int, &sg_allow_dio);
}

static ssize_t 
sg_proc_write_adio(struct file *filp, const char __user *buffer,
               size_t count, loff_t *off)
{
      int num;
      char buff[11];

      if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
            return -EACCES;
      num = (count < 10) ? count : 10;
      if (copy_from_user(buff, buffer, num))
            return -EFAULT;
      buff[num] = '\0';
      sg_allow_dio = simple_strtoul(buff, NULL, 10) ? 1 : 0;
      return count;
}

static int sg_proc_single_open_dressz(struct inode *inode, struct file *file)
{
      return single_open(file, sg_proc_seq_show_int, &sg_big_buff);
}

static ssize_t 
sg_proc_write_dressz(struct file *filp, const char __user *buffer,
                 size_t count, loff_t *off)
{
      int num;
      unsigned long k = ULONG_MAX;
      char buff[11];

      if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
            return -EACCES;
      num = (count < 10) ? count : 10;
      if (copy_from_user(buff, buffer, num))
            return -EFAULT;
      buff[num] = '\0';
      k = simple_strtoul(buff, NULL, 10);
      if (k <= 1048576) {     /* limit "big buff" to 1 MB */
            sg_big_buff = k;
            return count;
      }
      return -ERANGE;
}

static int sg_proc_seq_show_version(struct seq_file *s, void *v)
{
      seq_printf(s, "%d\t%s [%s]\n", sg_version_num, SG_VERSION_STR,
               sg_version_date);
      return 0;
}

static int sg_proc_single_open_version(struct inode *inode, struct file *file)
{
      return single_open(file, sg_proc_seq_show_version, NULL);
}

static int sg_proc_seq_show_devhdr(struct seq_file *s, void *v)
{
      seq_printf(s, "host\tchan\tid\tlun\ttype\topens\tqdepth\tbusy\t"
               "online\n");
      return 0;
}

static int sg_proc_single_open_devhdr(struct inode *inode, struct file *file)
{
      return single_open(file, sg_proc_seq_show_devhdr, NULL);
}

struct sg_proc_deviter {
      loff_t      index;
      size_t      max;
};

static void * dev_seq_start(struct seq_file *s, loff_t *pos)
{
      struct sg_proc_deviter * it = kmalloc(sizeof(*it), GFP_KERNEL);

      s->private = it;
      if (! it)
            return NULL;

      it->index = *pos;
      it->max = sg_last_dev();
      if (it->index >= it->max)
            return NULL;
      return it;
}

static void * dev_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
      struct sg_proc_deviter * it = s->private;

      *pos = ++it->index;
      return (it->index < it->max) ? it : NULL;
}

static void dev_seq_stop(struct seq_file *s, void *v)
{
      kfree(s->private);
}

static int sg_proc_open_dev(struct inode *inode, struct file *file)
{
        return seq_open(file, &dev_seq_ops);
}

static int sg_proc_seq_show_dev(struct seq_file *s, void *v)
{
      struct sg_proc_deviter * it = (struct sg_proc_deviter *) v;
      Sg_device *sdp;
      struct scsi_device *scsidp;
      unsigned long iflags;

      read_lock_irqsave(&sg_index_lock, iflags);
      sdp = it ? sg_lookup_dev(it->index) : NULL;
      if (sdp && (scsidp = sdp->device) && (!sdp->detached))
            seq_printf(s, "%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\n",
                        scsidp->host->host_no, scsidp->channel,
                        scsidp->id, scsidp->lun, (int) scsidp->type,
                        1,
                        (int) scsidp->queue_depth,
                        (int) scsidp->device_busy,
                        (int) scsi_device_online(scsidp));
      else
            seq_printf(s, "-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\n");
      read_unlock_irqrestore(&sg_index_lock, iflags);
      return 0;
}

static int sg_proc_open_devstrs(struct inode *inode, struct file *file)
{
        return seq_open(file, &devstrs_seq_ops);
}

static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v)
{
      struct sg_proc_deviter * it = (struct sg_proc_deviter *) v;
      Sg_device *sdp;
      struct scsi_device *scsidp;
      unsigned long iflags;

      read_lock_irqsave(&sg_index_lock, iflags);
      sdp = it ? sg_lookup_dev(it->index) : NULL;
      if (sdp && (scsidp = sdp->device) && (!sdp->detached))
            seq_printf(s, "%8.8s\t%16.16s\t%4.4s\n",
                     scsidp->vendor, scsidp->model, scsidp->rev);
      else
            seq_printf(s, "<no active device>\n");
      read_unlock_irqrestore(&sg_index_lock, iflags);
      return 0;
}

/* must be called while holding sg_index_lock */
static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
{
      int k, m, new_interface, blen, usg;
      Sg_request *srp;
      Sg_fd *fp;
      const sg_io_hdr_t *hp;
      const char * cp;
      unsigned int ms;

      k = 0;
      list_for_each_entry(fp, &sdp->sfds, sfd_siblings) {
            k++;
            read_lock(&fp->rq_list_lock); /* irqs already disabled */
            seq_printf(s, "   FD(%d): timeout=%dms bufflen=%d "
                     "(res)sgat=%d low_dma=%d\n", k,
                     jiffies_to_msecs(fp->timeout),
                     fp->reserve.bufflen,
                     (int) fp->reserve.k_use_sg,
                     (int) fp->low_dma);
            seq_printf(s, "   cmd_q=%d f_packid=%d k_orphan=%d closed=%d\n",
                     (int) fp->cmd_q, (int) fp->force_packid,
                     (int) fp->keep_orphan, (int) fp->closed);
            for (m = 0, srp = fp->headrp;
                        srp != NULL;
                        ++m, srp = srp->nextrp) {
                  hp = &srp->header;
                  new_interface = (hp->interface_id == '\0') ? 0 : 1;
                  if (srp->res_used) {
                        if (new_interface && 
                            (SG_FLAG_MMAP_IO & hp->flags))
                              cp = "     mmap>> ";
                        else
                              cp = "     rb>> ";
                  } else {
                        if (SG_INFO_DIRECT_IO_MASK & hp->info)
                              cp = "     dio>> ";
                        else
                              cp = "     ";
                  }
                  seq_printf(s, cp);
                  blen = srp->data.bufflen;
                  usg = srp->data.k_use_sg;
                  seq_printf(s, srp->done ? 
                           ((1 == srp->done) ?  "rcv:" : "fin:")
                           : "act:");
                  seq_printf(s, " id=%d blen=%d",
                           srp->header.pack_id, blen);
                  if (srp->done)
                        seq_printf(s, " dur=%d", hp->duration);
                  else {
                        ms = jiffies_to_msecs(jiffies);
                        seq_printf(s, " t_o/elap=%d/%d",
                              (new_interface ? hp->timeout :
                                      jiffies_to_msecs(fp->timeout)),
                              (ms > hp->duration ? ms - hp->duration : 0));
                  }
                  seq_printf(s, "ms sgat=%d op=0x%02x\n", usg,
                           (int) srp->data.cmd_opcode);
            }
            if (0 == m)
                  seq_printf(s, "     No requests active\n");
            read_unlock(&fp->rq_list_lock);
      }
}

static int sg_proc_open_debug(struct inode *inode, struct file *file)
{
        return seq_open(file, &debug_seq_ops);
}

static int sg_proc_seq_show_debug(struct seq_file *s, void *v)
{
      struct sg_proc_deviter * it = (struct sg_proc_deviter *) v;
      Sg_device *sdp;
      unsigned long iflags;

      if (it && (0 == it->index)) {
            seq_printf(s, "max_active_device=%d(origin 1)\n",
                     (int)it->max);
            seq_printf(s, " def_reserved_size=%d\n", sg_big_buff);
      }

      read_lock_irqsave(&sg_index_lock, iflags);
      sdp = it ? sg_lookup_dev(it->index) : NULL;
      if (sdp && !list_empty(&sdp->sfds)) {
            struct scsi_device *scsidp = sdp->device;

            seq_printf(s, " >>> device=%s ", sdp->disk->disk_name);
            if (sdp->detached)
                  seq_printf(s, "detached pending close ");
            else
                  seq_printf
                      (s, "scsi%d chan=%d id=%d lun=%d   em=%d",
                       scsidp->host->host_no,
                       scsidp->channel, scsidp->id,
                       scsidp->lun,
                       scsidp->host->hostt->emulated);
            seq_printf(s, " sg_tablesize=%d excl=%d\n",
                     sdp->sg_tablesize, sdp->exclude);
            sg_proc_debug_helper(s, sdp);
      }
      read_unlock_irqrestore(&sg_index_lock, iflags);
      return 0;
}

#endif                        /* CONFIG_SCSI_PROC_FS */

module_init(init_sg);
module_exit(exit_sg);

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