int nd_label_data_init()

in label.c [438:558]

• 67 lines of code
• 16 McCabe index (conditional complexity)

int nd_label_data_init(struct nvdimm_drvdata *ndd)
{
	size_t config_size, read_size, max_xfer, offset;
	struct nd_namespace_index *nsindex;
	unsigned int i;
	int rc = 0;
	u32 nslot;

	if (ndd->data)
		return 0;

	if (ndd->nsarea.status || ndd->nsarea.max_xfer == 0) {
		dev_dbg(ndd->dev, "failed to init config data area: (%u:%u)\n",
			ndd->nsarea.max_xfer, ndd->nsarea.config_size);
		return -ENXIO;
	}

	/*
	 * We need to determine the maximum index area as this is the section
	 * we must read and validate before we can start processing labels.
	 *
	 * If the area is too small to contain the two indexes and 2 labels
	 * then we abort.
	 *
	 * Start at a label size of 128 as this should result in the largest
	 * possible namespace index size.
	 */
	ndd->nslabel_size = 128;
	read_size = sizeof_namespace_index(ndd) * 2;
	if (!read_size)
		return -ENXIO;

	/* Allocate config data */
	config_size = ndd->nsarea.config_size;
	ndd->data = kvzalloc(config_size, GFP_KERNEL);
	if (!ndd->data)
		return -ENOMEM;

	/*
	 * We want to guarantee as few reads as possible while conserving
	 * memory. To do that we figure out how much unused space will be left
	 * in the last read, divide that by the total number of reads it is
	 * going to take given our maximum transfer size, and then reduce our
	 * maximum transfer size based on that result.
	 */
	max_xfer = min_t(size_t, ndd->nsarea.max_xfer, config_size);
	if (read_size < max_xfer) {
		/* trim waste */
		max_xfer -= ((max_xfer - 1) - (config_size - 1) % max_xfer) /
			    DIV_ROUND_UP(config_size, max_xfer);
		/* make certain we read indexes in exactly 1 read */
		if (max_xfer < read_size)
			max_xfer = read_size;
	}

	/* Make our initial read size a multiple of max_xfer size */
	read_size = min(DIV_ROUND_UP(read_size, max_xfer) * max_xfer,
			config_size);

	/* Read the index data */
	rc = nvdimm_get_config_data(ndd, ndd->data, 0, read_size);
	if (rc)
		goto out_err;

	/* Validate index data, if not valid assume all labels are invalid */
	ndd->ns_current = nd_label_validate(ndd);
	if (ndd->ns_current < 0)
		return 0;

	/* Record our index values */
	ndd->ns_next = nd_label_next_nsindex(ndd->ns_current);

	/* Copy "current" index on top of the "next" index */
	nsindex = to_current_namespace_index(ndd);
	nd_label_copy(ndd, to_next_namespace_index(ndd), nsindex);

	/* Determine starting offset for label data */
	offset = __le64_to_cpu(nsindex->labeloff);
	nslot = __le32_to_cpu(nsindex->nslot);

	/* Loop through the free list pulling in any active labels */
	for (i = 0; i < nslot; i++, offset += ndd->nslabel_size) {
		size_t label_read_size;

		/* zero out the unused labels */
		if (test_bit_le(i, nsindex->free)) {
			memset(ndd->data + offset, 0, ndd->nslabel_size);
			continue;
		}

		/* if we already read past here then just continue */
		if (offset + ndd->nslabel_size <= read_size)
			continue;

		/* if we haven't read in a while reset our read_size offset */
		if (read_size < offset)
			read_size = offset;

		/* determine how much more will be read after this next call. */
		label_read_size = offset + ndd->nslabel_size - read_size;
		label_read_size = DIV_ROUND_UP(label_read_size, max_xfer) *
				  max_xfer;

		/* truncate last read if needed */
		if (read_size + label_read_size > config_size)
			label_read_size = config_size - read_size;

		/* Read the label data */
		rc = nvdimm_get_config_data(ndd, ndd->data + read_size,
					    read_size, label_read_size);
		if (rc)
			goto out_err;

		/* push read_size to next read offset */
		read_size += label_read_size;
	}

	dev_dbg(ndd->dev, "len: %zu rc: %d\n", offset, rc);
out_err:
	return rc;
}