st.c

linux 内核源代码

			   size_t count, int is_read)
{
	int i, bufsize, retval = 0;
	struct st_buffer *STbp = STp->buffer;

	if (is_read)
		i = STp->try_dio_now && try_rdio;
	else
		i = STp->try_dio_now && try_wdio;

	if (i && ((unsigned long)buf & queue_dma_alignment(
					STp->device->request_queue)) == 0) {
		i = sgl_map_user_pages(&(STbp->sg[0]), STbp->use_sg,
				      (unsigned long)buf, count, (is_read ? READ : WRITE));
		if (i > 0) {
			STbp->do_dio = i;
			STbp->buffer_bytes = 0;   /* can be used as transfer counter */
		}
		else
			STbp->do_dio = 0;  /* fall back to buffering with any error */
		STbp->sg_segs = STbp->do_dio;
		STbp->frp_sg_current = 0;
		DEB(
		     if (STbp->do_dio) {
			STp->nbr_dio++;
			STp->nbr_pages += STbp->do_dio;
			for (i=1; i < STbp->do_dio; i++)
				if (page_to_pfn(STbp->sg[i].page) == page_to_pfn(STbp->sg[i-1].page) + 1)
					STp->nbr_combinable++;
		     }
		)
	} else
		STbp->do_dio = 0;
	DEB( STp->nbr_requests++; )

	if (!STbp->do_dio) {
		if (STp->block_size)
			bufsize = STp->block_size > st_fixed_buffer_size ?
				STp->block_size : st_fixed_buffer_size;
		else
			bufsize = count;
		if (bufsize > STbp->buffer_size &&
		    !enlarge_buffer(STbp, bufsize, STp->restr_dma)) {
			printk(KERN_WARNING "%s: Can't allocate %d byte tape buffer.\n",
			       tape_name(STp), bufsize);
			retval = (-EOVERFLOW);
			goto out;
		}
		if (STp->block_size)
			STbp->buffer_blocks = bufsize / STp->block_size;
	}

 out:
	return retval;
}


/* Can be called more than once after each setup_buffer() */
static void release_buffering(struct scsi_tape *STp, int is_read)
{
	struct st_buffer *STbp;

	STbp = STp->buffer;
	if (STbp->do_dio) {
		sgl_unmap_user_pages(&(STbp->sg[0]), STbp->do_dio, is_read);
		STbp->do_dio = 0;
		STbp->sg_segs = 0;
	}
}


/* Write command */
static ssize_t
st_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
{
	ssize_t total;
	ssize_t i, do_count, blks, transfer;
	ssize_t retval;
	int undone, retry_eot = 0, scode;
	int async_write;
	unsigned char cmd[MAX_COMMAND_SIZE];
	const char __user *b_point;
	struct st_request *SRpnt = NULL;
	struct scsi_tape *STp = filp->private_data;
	struct st_modedef *STm;
	struct st_partstat *STps;
	struct st_buffer *STbp;
	char *name = tape_name(STp);

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

	retval = rw_checks(STp, filp, count);
	if (retval || count == 0)
		goto out;

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

	STm = &(STp->modes[STp->current_mode]);
	STps = &(STp->ps[STp->partition]);

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


	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 "%s: Can't set default compression.\n",
				       name);
				if (modes_defined) {
					retval = (-EINVAL);
					goto out;
				}
			}
		}
	}

	STbp = STp->buffer;
	i = write_behind_check(STp);
	if (i) {
		if (i == -ENOSPC)
			STps->eof = ST_EOM_OK;
		else
			STps->eof = ST_EOM_ERROR;
	}

	if (STps->eof == ST_EOM_OK) {
		STps->eof = ST_EOD_1;  /* allow next write */
		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 &&
	    !STbp->do_dio &&
	    (copy_from_user(&i, buf, 1) != 0 ||
	     copy_from_user(&i, buf + count - 1, 1) != 0)) {
		retval = (-EFAULT);
		goto out;
	}

	retval = setup_buffering(STp, buf, count, 0);
	if (retval)
		goto out;

	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 (count > 0 && !retry_eot) {

		if (STbp->do_dio) {
			do_count = count;
		}
		else {
			if (STp->block_size == 0)
				do_count = count;
			else {
				do_count = STbp->buffer_blocks * STp->block_size -
					STbp->buffer_bytes;
				if (do_count > count)
					do_count = count;
			}

			i = append_to_buffer(b_point, STbp, do_count);
			if (i) {
				retval = i;
				goto out;
			}
		}
		count -= do_count;
		b_point += do_count;

		async_write = STp->block_size == 0 && !STbp->do_dio &&
			STm->do_async_writes && STps->eof < ST_EOM_OK;

		if (STp->block_size != 0 && STm->do_buffer_writes &&
		    !(STp->try_dio_now && try_wdio) && STps->eof < ST_EOM_OK &&
		    STbp->buffer_bytes < STbp->buffer_size) {
			STp->dirty = 1;
			/* Don't write a buffer that is not full enough. */
			if (!async_write && count == 0)
				break;
		}

	retry_write:
		if (STp->block_size == 0)
			blks = transfer = do_count;
		else {
			if (!STbp->do_dio)
				blks = STbp->buffer_bytes;
			else
				blks = do_count;
			blks /= 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, DMA_TO_DEVICE,
				   STp->device->timeout, MAX_WRITE_RETRIES, !async_write);
		if (!SRpnt) {
			retval = STbp->syscall_result;
			goto out;
		}
		if (async_write && !STbp->syscall_result) {
			STbp->writing = transfer;
			STp->dirty = !(STbp->writing ==
				       STbp->buffer_bytes);
			SRpnt = NULL;  /* Prevent releasing this request! */
			DEB( STp->write_pending = 1; )
			break;
		}

		if (STbp->syscall_result != 0) {
			struct st_cmdstatus *cmdstatp = &STp->buffer->cmdstat;

                        DEBC(printk(ST_DEB_MSG "%s: Error on write:\n", name));
			if (cmdstatp->have_sense && (cmdstatp->flags & SENSE_EOM)) {
				scode = cmdstatp->sense_hdr.sense_key;
				if (cmdstatp->remainder_valid)
					undone = (int)cmdstatp->uremainder64;
				else if (STp->block_size == 0 &&
					 scode == VOLUME_OVERFLOW)
					undone = transfer;
				else
					undone = 0;
				if (STp->block_size != 0)
					undone *= STp->block_size;
				if (undone <= do_count) {
					/* Only data from this write is not written */
					count += undone;
					do_count -= undone;
					if (STp->block_size)
						blks = (transfer - undone) / STp->block_size;
					STps->eof = ST_EOM_OK;
					/* Continue in fixed block mode if all written
					   in this request but still something left to write
					   (retval left to zero)
					*/
					if (STp->block_size == 0 ||
					    undone > 0 || count == 0)
						retval = (-ENOSPC); /* EOM within current request */
                                        DEBC(printk(ST_DEB_MSG
                                                       "%s: EOM with %d bytes unwritten.\n",
						       name, (int)count));
				} else {
					/* EOT within data buffered earlier (possible only
					   in fixed block mode without direct i/o) */
					if (!retry_eot && !cmdstatp->deferred &&
					    (scode == NO_SENSE || scode == RECOVERED_ERROR)) {
						move_buffer_data(STp->buffer, transfer - undone);
						retry_eot = 1;
						if (STps->drv_block >= 0) {
							STps->drv_block += (transfer - undone) /
								STp->block_size;
						}
						STps->eof = ST_EOM_OK;
						DEBC(printk(ST_DEB_MSG
							    "%s: Retry write of %d bytes at EOM.\n",
							    name, STp->buffer->buffer_bytes));
						goto retry_write;
					}
					else {
						/* Either error within data buffered by driver or
						   failed retry */
						count -= do_count;
						blks = do_count = 0;
						STps->eof = ST_EOM_ERROR;
						STps->drv_block = (-1); /* Too cautious? */
						retval = (-EIO);	/* EOM for old data */
						DEBC(printk(ST_DEB_MSG
							    "%s: EOM with lost data.\n",
							    name));
					}
				}
			} else {
				count += do_count;
				STps->drv_block = (-1);		/* Too cautious? */
				retval = STbp->syscall_result;
			}

		}

		if (STps->drv_block >= 0) {
			if (STp->block_size == 0)
				STps->drv_block += (do_count > 0);
			else
				STps->drv_block += blks;
		}

		STbp->buffer_bytes = 0;
		STp->dirty = 0;

		if (retval || retry_eot) {
			if (count < total)
				retval = total - count;
			goto out;
		}
	}

	if (STps->eof == ST_EOD_1)
		STps->eof = ST_EOM_OK;
	else if (STps->eof != ST_EOM_OK)
		STps->eof = ST_NOEOF;
	retval = total - count;

 out:
	if (SRpnt != NULL)
		st_release_request(SRpnt);
	release_buffering(STp, 0);
	mutex_unlock(&STp->lock);

	return retval;
}

/* Read data from the tape. Returns zero in the normal case, one if the
   eof status has changed, and the negative error code in case of a
   fatal error. Otherwise updates the buffer and the eof state.

   Does release user buffer mapping if it is set.
*/
static long read_tape(struct scsi_tape *STp, long count,
		      struct st_request ** aSRpnt)
{
	int transfer, blks, bytes;
	unsigned char cmd[MAX_COMMAND_SIZE];
	struct st_request *SRpnt;
	struct st_modedef *STm;
	struct st_partstat *STps;
	struct st_buffer *STbp;
	int retval = 0;
	char *name = tape_name(STp);

	if (count == 0)
		return 0;

	STm = &(STp->modes[STp->current_mode]);
	STps = &(STp->ps[STp->partition]);
	if (STps->eof == ST_FM_HIT)
		return 1;
	STbp = STp->buffer;

	if (STp->block_size == 0)
		blks = bytes = count;
	else {
		if (!(STp->try_dio_now && try_rdio) && STm->do_read_ahead) {
			blks = (STp->buffer)->buffer_blocks;
			bytes = blks * STp->block_size;
		} else {
			bytes = count;
			if (!STbp->do_dio && bytes > (STp->buffer)->buffer_size)
				bytes = (STp->buffer)->buffer_size;
			blks = bytes / STp->block_size;
			bytes = blks * STp->block_size;
		}
	}

	memset(cmd, 0, MAX_COMMAND_SIZE);
	cmd[0] = READ_6;
	cmd[1] = (STp->block_size != 0);
	cmd[2] = blks >> 16;
	cmd[3] = blks >> 8;
	cmd[4] = blks;

	SRpnt = *aSRpnt;
	SRpnt = st_do_scsi(SRpnt, STp, cmd, bytes, DMA_FROM_DEVICE,
			   STp->device->timeout, MAX_RETRIES, 1);
	release_buffering(STp, 1);
	*aSRpnt = SRpnt;
	if (!SRpnt)
		return STbp->syscall_result;

	STbp->read_pointer = 0;
	STps->at_sm = 0;

	/* Something to check */
	if (STbp->syscall_result) {
		struct st_cmdstatus *cmdstatp = &STp->buffer->cmdstat;

		retval = 1;
		DEBC(printk(ST_DEB_MSG "%s: Sense: %2x %2x %2x %2x %2x %2x %2x %2x\n",
                            name,
                            SRpnt->sense[0], SRpnt->sense[1],
                            SRpnt->sense[2], SRpnt->sense[3],
                            SRpnt->sense[4], SRpnt->sense[5],
                            SRpnt->sense[6], SRpnt->sense[7]));
		if (cmdstatp->have_sense) {

			if (cmdstatp->sense_hdr.sense_key == BLANK_CHECK)
				cmdstatp->flags &= 0xcf;	/* No need for EOM in this case */

			if (cmdstatp->flags != 0) { /* EOF, EOM, or ILI */
				/* Compute the residual count */
				if (cmdstatp->remainder_valid)
					transfer = (int)cmdstatp->uremainder64;
				else
					transfer = 0;
				if (STp->block_size == 0 &&
				    cmdstatp->sense_hdr.sense_key == MEDIUM_ERROR)
					transfer = bytes;

				if (cmdstatp->flags & SENSE_ILI) {	/* ILI */
					if (STp->block_size == 0) {
						if (transfer <= 0) {
							if (transfer < 0)
								printk(KERN_NOTICE
								       "%s: Failed to read %d byte block with %d byte transfer.\n",
								       name, bytes - transfer, bytes);
							if (STps->drv_block >= 0)
								STps->drv_block += 1;
							STbp->buffer_bytes = 0;
							return (-ENOMEM);
						}
						STbp->buffer_bytes = bytes - transfer;
					} else {
						st_release_request(SRpnt);
						SRpnt = *aSRpnt = NULL;
						if (transfer == blks) {	/* We did not get anything, error */
							printk(KERN_NOTICE "%s: Incorrect block size.\n", name);
							if (STps->drv_block >= 0)
								STps->drv_block += blks - transfer + 1;
							st_int_ioctl(STp, MTBSR, 1);
							return (-EIO);
						}
						/* We have some data, deliver it */
						STbp->buffer_bytes = (blks - transfer) *
						    STp->block_size;
                                                DEBC(printk(ST_DEB_MSG
                                                            "%s: ILI but enough data received %ld %d.\n",
                                                            name, count, STbp->buffer_bytes));
						if (STps->drv_block >= 0)
							STps->drv_block += 1;
						if (st_int_ioctl(STp, MTBSR, 1))
							return (-EIO);
					}
				} else if (cmdstatp->flags & SENSE_FMK) {	/* FM overrides EOM */