static sense_reason_t compare_and_write_callback()

in target_core_sbc.c [499:618]

• 77 lines of code
• 12 McCabe index (conditional complexity)

static sense_reason_t compare_and_write_callback(struct se_cmd *cmd, bool success,
						 int *post_ret)
{
	struct se_device *dev = cmd->se_dev;
	struct sg_table write_tbl = { };
	struct scatterlist *write_sg;
	struct sg_mapping_iter m;
	unsigned int len;
	unsigned int block_size = dev->dev_attrib.block_size;
	unsigned int compare_len = (cmd->t_task_nolb * block_size);
	unsigned int miscmp_off = 0;
	sense_reason_t ret = TCM_NO_SENSE;
	int i;

	/*
	 * Handle early failure in transport_generic_request_failure(),
	 * which will not have taken ->caw_sem yet..
	 */
	if (!success && (!cmd->t_data_sg || !cmd->t_bidi_data_sg))
		return TCM_NO_SENSE;
	/*
	 * Handle special case for zero-length COMPARE_AND_WRITE
	 */
	if (!cmd->data_length)
		goto out;
	/*
	 * Immediately exit + release dev->caw_sem if command has already
	 * been failed with a non-zero SCSI status.
	 */
	if (cmd->scsi_status) {
		pr_debug("compare_and_write_callback: non zero scsi_status:"
			" 0x%02x\n", cmd->scsi_status);
		*post_ret = 1;
		if (cmd->scsi_status == SAM_STAT_CHECK_CONDITION)
			ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
		goto out;
	}

	ret = compare_and_write_do_cmp(cmd->t_bidi_data_sg,
				       cmd->t_bidi_data_nents,
				       cmd->t_data_sg,
				       cmd->t_data_nents,
				       compare_len,
				       &miscmp_off);
	if (ret == TCM_MISCOMPARE_VERIFY) {
		/*
		 * SBC-4 r15: 5.3 COMPARE AND WRITE command
		 * In the sense data (see 4.18 and SPC-5) the offset from the
		 * start of the Data-Out Buffer to the first byte of data that
		 * was not equal shall be reported in the INFORMATION field.
		 */
		cmd->sense_info = miscmp_off;
		goto out;
	} else if (ret)
		goto out;

	if (sg_alloc_table(&write_tbl, cmd->t_data_nents, GFP_KERNEL) < 0) {
		pr_err("Unable to allocate compare_and_write sg\n");
		ret = TCM_OUT_OF_RESOURCES;
		goto out;
	}
	write_sg = write_tbl.sgl;

	i = 0;
	len = compare_len;
	sg_miter_start(&m, cmd->t_data_sg, cmd->t_data_nents, SG_MITER_TO_SG);
	/*
	 * Currently assumes NoLB=1 and SGLs are PAGE_SIZE..
	 */
	while (len) {
		sg_miter_next(&m);

		if (block_size < PAGE_SIZE) {
			sg_set_page(&write_sg[i], m.page, block_size,
				    m.piter.sg->offset + block_size);
		} else {
			sg_miter_next(&m);
			sg_set_page(&write_sg[i], m.page, block_size,
				    m.piter.sg->offset);
		}
		len -= block_size;
		i++;
	}
	sg_miter_stop(&m);
	/*
	 * Save the original SGL + nents values before updating to new
	 * assignments, to be released in transport_free_pages() ->
	 * transport_reset_sgl_orig()
	 */
	cmd->t_data_sg_orig = cmd->t_data_sg;
	cmd->t_data_sg = write_sg;
	cmd->t_data_nents_orig = cmd->t_data_nents;
	cmd->t_data_nents = 1;

	cmd->sam_task_attr = TCM_HEAD_TAG;
	cmd->transport_complete_callback = compare_and_write_post;
	/*
	 * Now reset ->execute_cmd() to the normal sbc_execute_rw() handler
	 * for submitting the adjusted SGL to write instance user-data.
	 */
	cmd->execute_cmd = sbc_execute_rw;

	spin_lock_irq(&cmd->t_state_lock);
	cmd->t_state = TRANSPORT_PROCESSING;
	cmd->transport_state |= CMD_T_ACTIVE | CMD_T_SENT;
	spin_unlock_irq(&cmd->t_state_lock);

	__target_execute_cmd(cmd, false);

	return ret;

out:
	/*
	 * In the MISCOMPARE or failure case, unlock ->caw_sem obtained in
	 * sbc_compare_and_write() before the original READ I/O submission.
	 */
	up(&dev->caw_sem);
	sg_free_table(&write_tbl);
	return ret;
}