st.c

讲述linux的初始化过程

	    __MOD_DEC_USE_COUNT(STp->device->host->hostt->module);
	return retval;

}


/* Flush the tape buffer before close */
static int st_flush(struct file *filp)
{
	int result = 0, result2;
	unsigned char cmd[MAX_COMMAND_SIZE];
	Scsi_Request *SRpnt;
	Scsi_Tape *STp;
	ST_mode *STm;
	ST_partstat *STps;

	struct inode *inode = filp->f_dentry->d_inode;
	kdev_t devt = inode->i_rdev;
	int dev;

	if (file_count(filp) > 1)
		return 0;

	dev = TAPE_NR(devt);
	read_lock(&st_dev_arr_lock);
	STp = scsi_tapes[dev];
	read_unlock(&st_dev_arr_lock);
	STm = &(STp->modes[STp->current_mode]);
	STps = &(STp->ps[STp->partition]);

	if (STps->rw == ST_WRITING && !(STp->device)->was_reset) {
		result = flush_write_buffer(STp);
		if (result != 0 && result != (-ENOSPC))
			goto out;
	}

	if (STp->can_partitions &&
	    (result2 = update_partition(STp)) < 0) {
                DEBC(printk(ST_DEB_MSG
                               "st%d: update_partition at close failed.\n", dev));
		if (result == 0)
			result = result2;
		goto out;
	}

	if (STps->rw == ST_WRITING && !(STp->device)->was_reset) {

                DEBC(printk(ST_DEB_MSG "st%d: File length %ld bytes.\n",
                            dev, (long) (filp->f_pos));
                     printk(ST_DEB_MSG "st%d: Async write waits %d, finished %d.\n",
                            dev, STp->nbr_waits, STp->nbr_finished);
		)

		memset(cmd, 0, MAX_COMMAND_SIZE);
		cmd[0] = WRITE_FILEMARKS;
		cmd[4] = 1 + STp->two_fm;

		SRpnt = st_do_scsi(NULL, STp, cmd, 0, SCSI_DATA_NONE,
				   STp->timeout, MAX_WRITE_RETRIES, TRUE);
		if (!SRpnt) {
			result = (STp->buffer)->syscall_result;
			goto out;
		}

		if ((STp->buffer)->syscall_result != 0 &&
		    ((SRpnt->sr_sense_buffer[0] & 0x70) != 0x70 ||
		     (SRpnt->sr_sense_buffer[2] & 0x4f) != 0x40 ||
		     ((SRpnt->sr_sense_buffer[0] & 0x80) != 0 &&
		      (SRpnt->sr_sense_buffer[3] | SRpnt->sr_sense_buffer[4] |
		       SRpnt->sr_sense_buffer[5] |
		       SRpnt->sr_sense_buffer[6]) != 0))) {
			/* Filter out successful write at EOM */
			scsi_release_request(SRpnt);
			SRpnt = NULL;
			printk(KERN_ERR "st%d: Error on write filemark.\n", dev);
			if (result == 0)
				result = (-EIO);
		} else {
			scsi_release_request(SRpnt);
			SRpnt = NULL;
			if (STps->drv_file >= 0)
				STps->drv_file++;
			STps->drv_block = 0;
			if (STp->two_fm)
				cross_eof(STp, FALSE);
			STps->eof = ST_FM;
		}

                DEBC(printk(ST_DEB_MSG "st%d: Buffer flushed, %d EOF(s) written\n",
                            dev, cmd[4]));
	} else if (!STp->rew_at_close) {
		STps = &(STp->ps[STp->partition]);
		if (!STm->sysv || STps->rw != ST_READING) {
			if (STp->can_bsr)
				result = flush_buffer(STp, 0);
			else if (STps->eof == ST_FM_HIT) {
				result = cross_eof(STp, FALSE);
				if (result) {
					if (STps->drv_file >= 0)
						STps->drv_file++;
					STps->drv_block = 0;
					STps->eof = ST_FM;
				} else
					STps->eof = ST_NOEOF;
			}
		} else if ((STps->eof == ST_NOEOF &&
			    !(result = cross_eof(STp, TRUE))) ||
			   STps->eof == ST_FM_HIT) {
			if (STps->drv_file >= 0)
				STps->drv_file++;
			STps->drv_block = 0;
			STps->eof = ST_FM;
		}
	}

      out:
	if (STp->rew_at_close) {
		result2 = st_int_ioctl(STp, MTREW, 1);
		if (result == 0)
			result = result2;
	}
	return result;
}


/* Close the device and release it. BKL is not needed: this is the only thread
   accessing this tape. */
static int st_release(struct inode *inode, struct file *filp)
{
	int result = 0;
	Scsi_Tape *STp;
	unsigned long flags;

	kdev_t devt = inode->i_rdev;
	int dev;

	dev = TAPE_NR(devt);
	read_lock(&st_dev_arr_lock);
	STp = scsi_tapes[dev];
	read_unlock(&st_dev_arr_lock);

	if (STp->door_locked == ST_LOCKED_AUTO)
		st_int_ioctl(STp, MTUNLOCK, 0);

	if (STp->buffer != NULL) {
		normalize_buffer(STp->buffer);
		write_lock_irqsave(&st_dev_arr_lock, flags);
		(STp->buffer)->in_use = 0;
		STp->buffer = NULL;
	}
	else {
		write_lock_irqsave(&st_dev_arr_lock, flags);
	}

	STp->in_use = 0;
	write_unlock_irqrestore(&st_dev_arr_lock, flags);
	if (STp->device->host->hostt->module)
		__MOD_DEC_USE_COUNT(STp->device->host->hostt->module);

	return result;
}


/* Write command */
static ssize_t
 st_write(struct file *filp, const char *buf, size_t count, loff_t * ppos)
{
	struct inode *inode = filp->f_dentry->d_inode;
	ssize_t total;
	ssize_t i, do_count, blks, transfer;
	ssize_t retval = 0;
	int write_threshold;
	int doing_write = 0;
	unsigned char cmd[MAX_COMMAND_SIZE];
	const char *b_point;
	Scsi_Request *SRpnt = NULL;
	Scsi_Tape *STp;
	ST_mode *STm;
	ST_partstat *STps;
	int dev = TAPE_NR(inode->i_rdev);

	read_lock(&st_dev_arr_lock);
	STp = scsi_tapes[dev];
	read_unlock(&st_dev_arr_lock);

	if (down_interruptible(&STp->lock))
		return -ERESTARTSYS;

	/*
	 * If we are in the middle of error recovery, don't let anyone
	 * else try and use this device.  Also, if error recovery fails, it
	 * may try and take the device offline, in which case all further
	 * access to the device is prohibited.
	 */
	if (!scsi_block_when_processing_errors(STp->device)) {
		retval = (-ENXIO);
		goto out;
	}

	if (ppos != &filp->f_pos) {
		/* "A request was outside the capabilities of the device." */
		retval = (-ENXIO);
		goto out;
	}

	if (STp->ready != ST_READY) {
		if (STp->ready == ST_NO_TAPE)
			retval = (-ENOMEDIUM);
		else
			retval = (-EIO);
		goto out;
	}

	STm = &(STp->modes[STp->current_mode]);
	if (!STm->defined) {
		retval = (-ENXIO);
		goto out;
	}
	if (count == 0)
		goto out;

	/*
	 * If there was a bus reset, block further access
	 * to this device.
	 */
	if (STp->device->was_reset) {
		retval = (-EIO);
		goto out;
	}

        DEB(
	if (!STp->in_use) {
		printk(ST_DEB_MSG "st%d: Incorrect device.\n", dev);
		retval = (-EIO);
		goto out;
	} ) /* end DEB */

	/* Write must be integral number of blocks */
	if (STp->block_size != 0 && (count % STp->block_size) != 0) {
		printk(KERN_WARNING "st%d: Write not multiple of tape block size.\n",
		       dev);
		retval = (-EINVAL);
		goto out;
	}

	if (STp->can_partitions &&
	    (retval = update_partition(STp)) < 0)
		goto out;
	STps = &(STp->ps[STp->partition]);

	if (STp->write_prot) {
		retval = (-EACCES);
		goto out;
	}

	if (STp->block_size == 0) {
		if (STp->max_block > 0 &&
		    (count < STp->min_block || count > STp->max_block)) {
			retval = (-EINVAL);
			goto out;
		}
		if (count > (STp->buffer)->buffer_size &&
		    !enlarge_buffer(STp->buffer, count, STp->restr_dma)) {
			retval = (-EOVERFLOW);
			goto out;
		}
	}
	if ((STp->buffer)->buffer_blocks < 1) {
		/* Fixed block mode with too small buffer */
		if (!enlarge_buffer(STp->buffer, STp->block_size, STp->restr_dma)) {
			retval = (-EOVERFLOW);
			goto out;
		}
		(STp->buffer)->buffer_blocks = 1;
	}

	if (STp->do_auto_lock && STp->door_locked == ST_UNLOCKED &&
	    !st_int_ioctl(STp, MTLOCK, 0))
		STp->door_locked = ST_LOCKED_AUTO;

	if (STps->rw == ST_READING) {
		retval = flush_buffer(STp, 0);
		if (retval)
			goto out;
		STps->rw = ST_WRITING;
	} else if (STps->rw != ST_WRITING &&
		   STps->drv_file == 0 && STps->drv_block == 0) {
		if ((retval = set_mode_densblk(STp, STm)) < 0)
			goto out;
		if (STm->default_compression != ST_DONT_TOUCH &&
		    !(STp->compression_changed)) {
			if (st_compression(STp, (STm->default_compression == ST_YES))) {
				printk(KERN_WARNING "st%d: Can't set default compression.\n",
				       dev);
				if (modes_defined) {
					retval = (-EINVAL);
					goto out;
				}
			}
		}
	}

	if ((STp->buffer)->writing) {
		write_behind_check(STp);
		if ((STp->buffer)->syscall_result) {
                        DEBC(printk(ST_DEB_MSG "st%d: Async write error (write) %x.\n",
                                    dev, (STp->buffer)->midlevel_result));
			if ((STp->buffer)->midlevel_result == INT_MAX)
				STps->eof = ST_EOM_OK;
			else
				STps->eof = ST_EOM_ERROR;
		}
	}

	if (STps->eof == ST_EOM_OK) {
		retval = (-ENOSPC);
		goto out;
	}
	else if (STps->eof == ST_EOM_ERROR) {
		retval = (-EIO);
		goto out;
	}

	/* Check the buffer readability in cases where copy_user might catch
	   the problems after some tape movement. */
	if (STp->block_size != 0 &&
	    (copy_from_user(&i, buf, 1) != 0 ||
	     copy_from_user(&i, buf + count - 1, 1) != 0)) {
		retval = (-EFAULT);
		goto out;
	}

	if (!STm->do_buffer_writes) {
#if 0
		if (STp->block_size != 0 && (count % STp->block_size) != 0) {
			retval = (-EINVAL);	/* Write must be integral number of blocks */
			goto out;
		}
#endif
		write_threshold = 1;
	} else
		write_threshold = (STp->buffer)->buffer_blocks * STp->block_size;
	if (!STm->do_async_writes)
		write_threshold--;

	total = count;

	memset(cmd, 0, MAX_COMMAND_SIZE);
	cmd[0] = WRITE_6;
	cmd[1] = (STp->block_size != 0);

	STps->rw = ST_WRITING;

	b_point = buf;
	while ((STp->block_size == 0 && !STm->do_async_writes && count > 0) ||
	       (STp->block_size != 0 &&
		(STp->buffer)->buffer_bytes + count > write_threshold)) {
		doing_write = 1;
		if (STp->block_size == 0)
			do_count = count;
		else {
			do_count = (STp->buffer)->buffer_blocks * STp->block_size -
			    (STp->buffer)->buffer_bytes;
			if (do_count > count)
				do_count = count;
		}

		i = append_to_buffer(b_point, STp->buffer, do_count);
		if (i) {
			retval = i;
			goto out;
		}

		if (STp->block_size == 0)
			blks = transfer = do_count;
		else {
			blks = (STp->buffer)->buffer_bytes /
			    STp->block_size;
			transfer = blks * STp->block_size;
		}
		cmd[2] = blks >> 16;
		cmd[3] = blks >> 8;
		cmd[4] = blks;

		SRpnt = st_do_scsi(SRpnt, STp, cmd, transfer, SCSI_DATA_WRITE,
				   STp->timeout, MAX_WRITE_RETRIES, TRUE);
		if (!SRpnt) {
			retval = (STp->buffer)->syscall_result;
			goto out;
		}

		if ((STp->buffer)->syscall_result != 0) {
                        DEBC(printk(ST_DEB_MSG "st%d: Error on write:\n", dev));
			if ((SRpnt->sr_sense_buffer[0] & 0x70) == 0x70 &&
			    (SRpnt->sr_sense_buffer[2] & 0x40)) {
				if (STp->block_size != 0 &&
                                    (SRpnt->sr_sense_buffer[0] & 0x80) != 0)
					transfer = (SRpnt->sr_sense_buffer[3] << 24) |
					    (SRpnt->sr_sense_buffer[4] << 16) |
					    (SRpnt->sr_sense_buffer[5] << 8) |
                                                SRpnt->sr_sense_buffer[6];
				else if (STp->block_size == 0 &&
					 (SRpnt->sr_sense_buffer[2] & 0x0f) ==
                                         VOLUME_OVERFLOW)
					transfer = do_count;
				else
					transfer = 0;
				if (STp->block_size != 0)
					transfer *= STp->block_size;
				if (transfer <= do_count) {
					filp->f_pos += do_count - transfer;
					count -= do_count - transfer;
					if (STps->drv_block >= 0) {
						if (STp->block_size == 0 &&
                                                    transfer < do_count)
							STps->drv_block++;
						else if (STp->block_size != 0)
							STps->drv_block +=
                                                                (do_count - transfer) /
                                                                STp->block_size;
					}
					STps->eof = ST_EOM_OK;
					retval = (-ENOSPC); /* EOM within current request */
                                        DEBC(printk(ST_DEB_MSG
                                                       "st%d: EOM with %d bytes unwritten.\n",
						       dev, transfer));
				} else {
					STps->eof = ST_EOM_ERROR;
					STps->drv_block = (-1); /* Too cautious? */
					retval = (-EIO);	/* EOM for old data */
					DEBC(printk(ST_DEB_MSG
                                                       "st%d: EOM with lost data.\n",
                                                       dev));
				}
			} else {
				STps->drv_block = (-1);		/* Too cautious? */
				retval = (-EIO);
			}

			scsi_release_request(SRpnt);
			SRpnt = NULL;
			(STp->buffer)->buffer_bytes = 0;
			STp->dirty = 0;
			if (count < total)
				retval = total - count;
			goto out;
		}
		filp->f_pos += do_count;
		b_point += do_count;
		count -= do_count;
		if (STps->drv_block >= 0) {
			if (STp->block_size == 0)
				STps->drv_block++;
			else