path: root/drivers/md/persistent-data/dm-array.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */

#include "dm-array.h"
#include "dm-space-map.h"
#include "dm-transaction-manager.h"

#include <linux/export.h>
#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "array"

/*----------------------------------------------------------------*/

/*
 * The array is implemented as a fully populated btree, which points to
 * blocks that contain the packed values.  This is more space efficient
 * than just using a btree since we don't store 1 key per value.
 */
struct array_block {
	__le32 csum;
	__le32 max_entries;
	__le32 nr_entries;
	__le32 value_size;
	__le64 blocknr; /* Block this node is supposed to live in. */
} __packed;

/*----------------------------------------------------------------*/

/*
 * Validator methods.  As usual we calculate a checksum, and also write the
 * block location into the header (paranoia about ssds remapping areas by
 * mistake).
 */
#define CSUM_XOR 595846735

/*
 * Each array block can hold this many values.
 */
static uint32_t calc_max_entries(size_t value_size, size_t size_of_block)
{
	return (size_of_block - sizeof(struct array_block)) / value_size;
}

static void array_block_prepare_for_write(const struct dm_block_validator *v,
					  struct dm_block *b,
					  size_t size_of_block)
{
	struct array_block *bh_le = dm_block_data(b);

	bh_le->blocknr = cpu_to_le64(dm_block_location(b));
	bh_le->csum = cpu_to_le32(dm_bm_checksum(&bh_le->max_entries,
						 size_of_block - sizeof(__le32),
						 CSUM_XOR));
}

static int array_block_check(const struct dm_block_validator *v,
			     struct dm_block *b,
			     size_t size_of_block)
{
	struct array_block *bh_le = dm_block_data(b);
	uint32_t nr_entries, max_entries, value_size;
	__le32 csum_disk;

	if (dm_block_location(b) != le64_to_cpu(bh_le->blocknr)) {
		DMERR_LIMIT("%s failed: blocknr %llu != wanted %llu", __func__,
			    (unsigned long long) le64_to_cpu(bh_le->blocknr),
			    (unsigned long long) dm_block_location(b));
		return -ENOTBLK;
	}

	csum_disk = cpu_to_le32(dm_bm_checksum(&bh_le->max_entries,
					       size_of_block - sizeof(__le32),
					       CSUM_XOR));
	if (csum_disk != bh_le->csum) {
		DMERR_LIMIT("%s failed: csum %u != wanted %u", __func__,
			    (unsigned int) le32_to_cpu(csum_disk),
			    (unsigned int) le32_to_cpu(bh_le->csum));
		return -EILSEQ;
	}

	nr_entries = le32_to_cpu(bh_le->nr_entries);
	max_entries = le32_to_cpu(bh_le->max_entries);
	value_size = le32_to_cpu(bh_le->value_size);

	if (!value_size) {
		DMERR_LIMIT("%s failed: value_size is zero", __func__);
		return -EILSEQ;
	}

	if (max_entries != calc_max_entries(value_size, size_of_block)) {
		DMERR_LIMIT("%s failed: max_entries %u invalid for value_size %u",
			    __func__, max_entries, value_size);
		return -EILSEQ;
	}

	if (nr_entries > max_entries) {
		DMERR_LIMIT("%s failed: too many entries", __func__);
		return -EILSEQ;
	}

	return 0;
}

static const struct dm_block_validator array_validator = {
	.name = "array",
	.prepare_for_write = array_block_prepare_for_write,
	.check = array_block_check
};

/*----------------------------------------------------------------*/

/*
 * Functions for manipulating the array blocks.
 */

/*
 * Returns a pointer to a value within an array block.
 *
 * index - The index into _this_ specific block.
 */
static void *element_at(struct dm_array_info *info, struct array_block *ab,
			unsigned int index)
{
	unsigned char *entry = (unsigned char *) (ab + 1);

	entry += index * info->value_type.size;

	return entry;
}

/*
 * Utility function that calls one of the value_type methods on every value
 * in an array block.
 */
static void on_entries(struct dm_array_info *info, struct array_block *ab,
		       void (*fn)(void *, const void *,