static int __nd_label_validate()

in label.c [94:238]

• 103 lines of code
• 18 McCabe index (conditional complexity)

static int __nd_label_validate(struct nvdimm_drvdata *ndd)
{
	/*
	 * On media label format consists of two index blocks followed
	 * by an array of labels.  None of these structures are ever
	 * updated in place.  A sequence number tracks the current
	 * active index and the next one to write, while labels are
	 * written to free slots.
	 *
	 *     +------------+
	 *     |            |
	 *     |  nsindex0  |
	 *     |            |
	 *     +------------+
	 *     |            |
	 *     |  nsindex1  |
	 *     |            |
	 *     +------------+
	 *     |   label0   |
	 *     +------------+
	 *     |   label1   |
	 *     +------------+
	 *     |            |
	 *      ....nslot...
	 *     |            |
	 *     +------------+
	 *     |   labelN   |
	 *     +------------+
	 */
	struct nd_namespace_index *nsindex[] = {
		to_namespace_index(ndd, 0),
		to_namespace_index(ndd, 1),
	};
	const int num_index = ARRAY_SIZE(nsindex);
	struct device *dev = ndd->dev;
	bool valid[2] = { 0 };
	int i, num_valid = 0;
	u32 seq;

	for (i = 0; i < num_index; i++) {
		u32 nslot;
		u8 sig[NSINDEX_SIG_LEN];
		u64 sum_save, sum, size;
		unsigned int version, labelsize;

		memcpy(sig, nsindex[i]->sig, NSINDEX_SIG_LEN);
		if (memcmp(sig, NSINDEX_SIGNATURE, NSINDEX_SIG_LEN) != 0) {
			dev_dbg(dev, "nsindex%d signature invalid\n", i);
			continue;
		}

		/* label sizes larger than 128 arrived with v1.2 */
		version = __le16_to_cpu(nsindex[i]->major) * 100
			+ __le16_to_cpu(nsindex[i]->minor);
		if (version >= 102)
			labelsize = 1 << (7 + nsindex[i]->labelsize);
		else
			labelsize = 128;

		if (labelsize != sizeof_namespace_label(ndd)) {
			dev_dbg(dev, "nsindex%d labelsize %d invalid\n",
					i, nsindex[i]->labelsize);
			continue;
		}

		sum_save = __le64_to_cpu(nsindex[i]->checksum);
		nsindex[i]->checksum = __cpu_to_le64(0);
		sum = nd_fletcher64(nsindex[i], sizeof_namespace_index(ndd), 1);
		nsindex[i]->checksum = __cpu_to_le64(sum_save);
		if (sum != sum_save) {
			dev_dbg(dev, "nsindex%d checksum invalid\n", i);
			continue;
		}

		seq = __le32_to_cpu(nsindex[i]->seq);
		if ((seq & NSINDEX_SEQ_MASK) == 0) {
			dev_dbg(dev, "nsindex%d sequence: %#x invalid\n", i, seq);
			continue;
		}

		/* sanity check the index against expected values */
		if (__le64_to_cpu(nsindex[i]->myoff)
				!= i * sizeof_namespace_index(ndd)) {
			dev_dbg(dev, "nsindex%d myoff: %#llx invalid\n",
					i, (unsigned long long)
					__le64_to_cpu(nsindex[i]->myoff));
			continue;
		}
		if (__le64_to_cpu(nsindex[i]->otheroff)
				!= (!i) * sizeof_namespace_index(ndd)) {
			dev_dbg(dev, "nsindex%d otheroff: %#llx invalid\n",
					i, (unsigned long long)
					__le64_to_cpu(nsindex[i]->otheroff));
			continue;
		}
		if (__le64_to_cpu(nsindex[i]->labeloff)
				!= 2 * sizeof_namespace_index(ndd)) {
			dev_dbg(dev, "nsindex%d labeloff: %#llx invalid\n",
					i, (unsigned long long)
					__le64_to_cpu(nsindex[i]->labeloff));
			continue;
		}

		size = __le64_to_cpu(nsindex[i]->mysize);
		if (size > sizeof_namespace_index(ndd)
				|| size < sizeof(struct nd_namespace_index)) {
			dev_dbg(dev, "nsindex%d mysize: %#llx invalid\n", i, size);
			continue;
		}

		nslot = __le32_to_cpu(nsindex[i]->nslot);
		if (nslot * sizeof_namespace_label(ndd)
				+ 2 * sizeof_namespace_index(ndd)
				> ndd->nsarea.config_size) {
			dev_dbg(dev, "nsindex%d nslot: %u invalid, config_size: %#x\n",
					i, nslot, ndd->nsarea.config_size);
			continue;
		}
		valid[i] = true;
		num_valid++;
	}

	switch (num_valid) {
	case 0:
		break;
	case 1:
		for (i = 0; i < num_index; i++)
			if (valid[i])
				return i;
		/* can't have num_valid > 0 but valid[] = { false, false } */
		WARN_ON(1);
		break;
	default:
		/* pick the best index... */
		seq = best_seq(__le32_to_cpu(nsindex[0]->seq),
				__le32_to_cpu(nsindex[1]->seq));
		if (seq == (__le32_to_cpu(nsindex[1]->seq) & NSINDEX_SEQ_MASK))
			return 1;
		else
			return 0;
		break;
	}

	return -1;
}