diff --git a/drivers/md/dm-vdo/chapter-index.c b/drivers/md/dm-vdo/chapter-index.c
new file mode 100644
index 000000000000..27a2d95a2bef
--- /dev/null
+++ b/drivers/md/dm-vdo/chapter-index.c
@@ -0,0 +1,291 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "chapter-index.h"
+
+#include "errors.h"
+#include "hash-utils.h"
+#include "logger.h"
+#include "memory-alloc.h"
+#include "permassert.h"
+#include "uds.h"
+
+int uds_make_open_chapter_index(struct open_chapter_index **chapter_index,
+				const struct geometry *geometry, u64 volume_nonce)
+{
+	int result;
+	size_t memory_size;
+	struct open_chapter_index *index;
+
+	result = uds_allocate(1, struct open_chapter_index, "open chapter index",
+			      &index);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	/*
+	 * The delta index will rebalance delta lists when memory gets tight,
+	 * so give the chapter index one extra page.
+	 */
+	memory_size = ((geometry->index_pages_per_chapter + 1) * geometry->bytes_per_page);
+	index->geometry = geometry;
+	index->volume_nonce = volume_nonce;
+	result = uds_initialize_delta_index(&index->delta_index, 1,
+					    geometry->delta_lists_per_chapter,
+					    geometry->chapter_mean_delta,
+					    geometry->chapter_payload_bits,
+					    memory_size, 'm');
+	if (result != UDS_SUCCESS) {
+		uds_free(index);
+		return result;
+	}
+
+	index->memory_size = index->delta_index.memory_size + sizeof(struct open_chapter_index);
+	*chapter_index = index;
+	return UDS_SUCCESS;
+}
+
+void uds_free_open_chapter_index(struct open_chapter_index *chapter_index)
+{
+	if (chapter_index == NULL)
+		return;
+
+	uds_uninitialize_delta_index(&chapter_index->delta_index);
+	uds_free(chapter_index);
+}
+
+/* Re-initialize an open chapter index for a new chapter. */
+void uds_empty_open_chapter_index(struct open_chapter_index *chapter_index,
+				  u64 virtual_chapter_number)
+{
+	uds_reset_delta_index(&chapter_index->delta_index);
+	chapter_index->virtual_chapter_number = virtual_chapter_number;
+}
+
+static inline bool was_entry_found(const struct delta_index_entry *entry, u32 address)
+{
+	return (!entry->at_end) && (entry->key == address);
+}
+
+/* Associate a record name with the record page containing its metadata. */
+int uds_put_open_chapter_index_record(struct open_chapter_index *chapter_index,
+				      const struct uds_record_name *name,
+				      u32 page_number)
+{
+	int result;
+	struct delta_index_entry entry;
+	u32 address;
+	u32 list_number;
+	const u8 *found_name;
+	bool found;
+	const struct geometry *geometry = chapter_index->geometry;
+	u64 chapter_number = chapter_index->virtual_chapter_number;
+	u32 record_pages = geometry->record_pages_per_chapter;
+
+	result = ASSERT(page_number < record_pages,
+			"Page number within chapter (%u) exceeds the maximum value %u",
+			page_number, record_pages);
+	if (result != UDS_SUCCESS)
+		return UDS_INVALID_ARGUMENT;
+
+	address = uds_hash_to_chapter_delta_address(name, geometry);
+	list_number = uds_hash_to_chapter_delta_list(name, geometry);
+	result = uds_get_delta_index_entry(&chapter_index->delta_index, list_number,
+					   address, name->name, &entry);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	found = was_entry_found(&entry, address);
+	result = ASSERT(!(found && entry.is_collision),
+			"Chunk appears more than once in chapter %llu",
+			(unsigned long long) chapter_number);
+	if (result != UDS_SUCCESS)
+		return UDS_BAD_STATE;
+
+	found_name = (found ? name->name : NULL);
+	return uds_put_delta_index_entry(&entry, address, page_number, found_name);
+}
+
+/*
+ * Pack a section of an open chapter index into a chapter index page. A range of delta lists
+ * (starting with a specified list index) is copied from the open chapter index into a memory page.
+ * The number of lists copied onto the page is returned to the caller on success.
+ *
+ * @chapter_index: The open chapter index
+ * @memory: The memory page to use
+ * @first_list: The first delta list number to be copied
+ * @last_page: If true, this is the last page of the chapter index and all the remaining lists must
+ *             be packed onto this page
+ * @lists_packed: The number of delta lists that were packed onto this page
+ */
+int uds_pack_open_chapter_index_page(struct open_chapter_index *chapter_index,
+				     u8 *memory, u32 first_list, bool last_page,
+				     u32 *lists_packed)
+{
+	int result;
+	struct delta_index *delta_index = &chapter_index->delta_index;
+	struct delta_index_stats stats;
+	u64 nonce = chapter_index->volume_nonce;
+	u64 chapter_number = chapter_index->virtual_chapter_number;
+	const struct geometry *geometry = chapter_index->geometry;
+	u32 list_count = geometry->delta_lists_per_chapter;
+	unsigned int removals = 0;
+	struct delta_index_entry entry;
+	u32 next_list;
+	s32 list_number;
+
+	for (;;) {
+		result = uds_pack_delta_index_page(delta_index, nonce, memory,
+						   geometry->bytes_per_page,
+						   chapter_number, first_list,
+						   lists_packed);
+		if (result != UDS_SUCCESS)
+			return result;
+
+		if ((first_list + *lists_packed) == list_count) {
+			/* All lists are packed. */
+			break;
+		} else if (*lists_packed == 0) {
+			/*
+			 * The next delta list does not fit on a page. This delta list will be
+			 * removed.
+			 */
+		} else if (last_page) {
+			/*
+			 * This is the last page and there are lists left unpacked, but all of the
+			 * remaining lists must fit on the page. Find a list that contains entries
+			 * and remove the entire list. Try the first list that does not fit. If it
+			 * is empty, we will select the last list that already fits and has any
+			 * entries.
+			 */
+		} else {
+			/* This page is done. */
+			break;
+		}
+
+		if (removals == 0) {
+			uds_get_delta_index_stats(delta_index, &stats);
+			uds_log_warning("The chapter index for chapter %llu contains %llu entries with %llu collisions",
+					(unsigned long long) chapter_number,
+					(unsigned long long) stats.record_count,
+					(unsigned long long) stats.collision_count);
+		}
+
+		list_number = *lists_packed;
+		do {
+			if (list_number < 0)
+				return UDS_OVERFLOW;
+
+			next_list = first_list + list_number--,
+			result = uds_start_delta_index_search(delta_index, next_list, 0,
+							      &entry);
+			if (result != UDS_SUCCESS)
+				return result;
+
+			result = uds_next_delta_index_entry(&entry);
+			if (result != UDS_SUCCESS)
+				return result;
+		} while (entry.at_end);
+
+		do {
+			result = uds_remove_delta_index_entry(&entry);
+			if (result != UDS_SUCCESS)
+				return result;
+
+			removals++;
+		} while (!entry.at_end);
+	}
+
+	if (removals > 0)
+		uds_log_warning("To avoid chapter index page overflow in chapter %llu, %u entries were removed from the chapter index",
+				(unsigned long long) chapter_number, removals);
+
+	return UDS_SUCCESS;
+}
+
+/* Make a new chapter index page, initializing it with the data from a given index_page buffer. */
+int uds_initialize_chapter_index_page(struct delta_index_page *index_page,
+				      const struct geometry *geometry, u8 *page_buffer,
+				      u64 volume_nonce)
+{
+	return uds_initialize_delta_index_page(index_page, volume_nonce,
+					       geometry->chapter_mean_delta,
+					       geometry->chapter_payload_bits,
+					       page_buffer, geometry->bytes_per_page);
+}
+
+/* Validate a chapter index page read during rebuild. */
+int uds_validate_chapter_index_page(const struct delta_index_page *index_page,
+				    const struct geometry *geometry)
+{
+	int result;
+	const struct delta_index *delta_index = &index_page->delta_index;
+	u32 first = index_page->lowest_list_number;
+	u32 last = index_page->highest_list_number;
+	u32 list_number;
+
+	/* We walk every delta list from start to finish. */
+	for (list_number = first; list_number <= last; list_number++) {
+		struct delta_index_entry entry;
+
+		result = uds_start_delta_index_search(delta_index, list_number - first,
+						      0, &entry);
+		if (result != UDS_SUCCESS)
+			return result;
+
+		for (;;) {
+			result = uds_next_delta_index_entry(&entry);
+			if (result != UDS_SUCCESS) {
+				/*
+				 * A random bit stream is highly likely to arrive here when we go
+				 * past the end of the delta list.
+				 */
+				return result;
+			}
+
+			if (entry.at_end)
+				break;
+
+			/* Also make sure that the record page field contains a plausible value. */
+			if (uds_get_delta_entry_value(&entry) >=
+			    geometry->record_pages_per_chapter)
+				/*
+				 * Do not log this as an error. It happens in normal operation when
+				 * we are doing a rebuild but haven't written the entire volume
+				 * once.
+				 */
+				return UDS_CORRUPT_DATA;
+		}
+	}
+	return UDS_SUCCESS;
+}
+
+/*
+ * Search a chapter index page for a record name, returning the record page number that may contain
+ * the name.
+ */
+int uds_search_chapter_index_page(struct delta_index_page *index_page,
+				  const struct geometry *geometry,
+				  const struct uds_record_name *name,
+				  u16 *record_page_ptr)
+{
+	int result;
+	struct delta_index *delta_index = &index_page->delta_index;
+	u32 address = uds_hash_to_chapter_delta_address(name, geometry);
+	u32 delta_list_number = uds_hash_to_chapter_delta_list(name, geometry);
+	u32 sub_list_number = delta_list_number - index_page->lowest_list_number;
+	struct delta_index_entry entry;
+
+	result = uds_get_delta_index_entry(delta_index, sub_list_number, address,
+					   name->name, &entry);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	if (was_entry_found(&entry, address))
+		*record_page_ptr = uds_get_delta_entry_value(&entry);
+	else
+		*record_page_ptr = NO_CHAPTER_INDEX_ENTRY;
+
+	return UDS_SUCCESS;
+}
diff --git a/drivers/md/dm-vdo/chapter-index.h b/drivers/md/dm-vdo/chapter-index.h
new file mode 100644
index 000000000000..ad1f61b6ab9a
--- /dev/null
+++ b/drivers/md/dm-vdo/chapter-index.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#ifndef UDS_CHAPTER_INDEX_H
+#define UDS_CHAPTER_INDEX_H
+
+#include <linux/limits.h>
+
+#include "delta-index.h"
+#include "geometry.h"
+
+/*
+ * A chapter index for an open chapter is a mutable structure that tracks all the records that have
+ * been added to the chapter. A chapter index for a closed chapter is similar except that it is
+ * immutable because the contents of a closed chapter can never change, and the immutable structure
+ * is more efficient. Both types of chapter index are implemented with a delta index.
+ */
+
+enum {
+	/* The value returned when no entry is found in the chapter index. */
+	NO_CHAPTER_INDEX_ENTRY = U16_MAX,
+};
+
+struct open_chapter_index {
+	const struct geometry *geometry;
+	struct delta_index delta_index;
+	u64 virtual_chapter_number;
+	u64 volume_nonce;
+	size_t memory_size;
+};
+
+int __must_check uds_make_open_chapter_index(struct open_chapter_index **chapter_index,
+					     const struct geometry *geometry,
+					     u64 volume_nonce);
+
+void uds_free_open_chapter_index(struct open_chapter_index *chapter_index);
+
+void uds_empty_open_chapter_index(struct open_chapter_index *chapter_index,
+				  u64 virtual_chapter_number);
+
+int __must_check uds_put_open_chapter_index_record(struct open_chapter_index *chapter_index,
+						   const struct uds_record_name *name,
+						   u32 page_number);
+
+int __must_check uds_pack_open_chapter_index_page(struct open_chapter_index *chapter_index,
+						  u8 *memory, u32 first_list,
+						  bool last_page, u32 *lists_packed);
+
+int __must_check uds_initialize_chapter_index_page(struct delta_index_page *index_page,
+						   const struct geometry *geometry,
+						   u8 *page_buffer, u64 volume_nonce);
+
+int __must_check uds_validate_chapter_index_page(const struct delta_index_page *index_page,
+						 const struct geometry *geometry);
+
+int __must_check uds_search_chapter_index_page(struct delta_index_page *index_page,
+					       const struct geometry *geometry,
+					       const struct uds_record_name *name,
+					       u16 *record_page_ptr);
+
+#endif /* UDS_CHAPTER_INDEX_H */
diff --git a/drivers/md/dm-vdo/open-chapter.c b/drivers/md/dm-vdo/open-chapter.c
new file mode 100644
index 000000000000..45cec2c3edb2
--- /dev/null
+++ b/drivers/md/dm-vdo/open-chapter.c
@@ -0,0 +1,427 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "open-chapter.h"
+
+#include <linux/log2.h>
+
+#include "config.h"
+#include "hash-utils.h"
+#include "logger.h"
+#include "memory-alloc.h"
+#include "numeric.h"
+#include "permassert.h"
+
+/*
+ * Each index zone has a dedicated open chapter zone structure which gets an equal share of the
+ * open chapter space. Records are assigned to zones based on their record name. Within each zone,
+ * records are stored in an array in the order they arrive. Additionally, a reference to each
+ * record is stored in a hash table to help determine if a new record duplicates an existing one.
+ * If new metadata for an existing name arrives, the record is altered in place. The array of
+ * records is 1-based so that record number 0 can be used to indicate an unused hash slot.
+ *
+ * Deleted records are marked with a flag rather than actually removed to simplify hash table
+ * management. The array of deleted flags overlays the array of hash slots, but the flags are
+ * indexed by record number instead of by record name. The number of hash slots will always be a
+ * power of two that is greater than the number of records to be indexed, guaranteeing that hash
+ * insertion cannot fail, and that there are sufficient flags for all records.
+ *
+ * Once any open chapter zone fills its available space, the chapter is closed. The records from
+ * each zone are interleaved to attempt to preserve temporal locality and assigned to record pages.
+ * Empty or deleted records are replaced by copies of a valid record so that the record pages only
+ * contain valid records. The chapter then constructs a delta index which maps each record name to
+ * the record page on which that record can be found, which is split into index pages. These
+ * structures are then passed to the volume to be recorded on storage.
+ *
+ * When the index is saved, the open chapter records are saved in a single array, once again
+ * interleaved to attempt to preserve temporal locality. When the index is reloaded, there may be a
+ * different number of zones than previously, so the records must be parcelled out to their new
+ * zones. In addition, depending on the distribution of record names, a new zone may have more
+ * records than it has space. In this case, the latest records for that zone will be discarded.
+ */
+
+static const u8 OPEN_CHAPTER_MAGIC[] = "ALBOC";
+static const u8 OPEN_CHAPTER_VERSION[] = "02.00";
+
+enum {
+	OPEN_CHAPTER_MAGIC_LENGTH = sizeof(OPEN_CHAPTER_MAGIC) - 1,
+	OPEN_CHAPTER_VERSION_LENGTH = sizeof(OPEN_CHAPTER_VERSION) - 1,
+	LOAD_RATIO = 2,
+};
+
+static inline size_t records_size(const struct open_chapter_zone *open_chapter)
+{
+	return sizeof(struct uds_volume_record) * (1 + open_chapter->capacity);
+}
+
+static inline size_t slots_size(size_t slot_count)
+{
+	return sizeof(struct open_chapter_zone_slot) * slot_count;
+}
+
+int uds_make_open_chapter(const struct geometry *geometry, unsigned int zone_count,
+			  struct open_chapter_zone **open_chapter_ptr)
+{
+	int result;
+	struct open_chapter_zone *open_chapter;
+	size_t capacity = geometry->records_per_chapter / zone_count;
+	size_t slot_count = (1 << bits_per(capacity * LOAD_RATIO));
+
+	result = uds_allocate_extended(struct open_chapter_zone, slot_count,
+				       struct open_chapter_zone_slot, "open chapter",
+				       &open_chapter);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	open_chapter->slot_count = slot_count;
+	open_chapter->capacity = capacity;
+	result = uds_allocate_cache_aligned(records_size(open_chapter), "record pages",
+					    &open_chapter->records);
+	if (result != UDS_SUCCESS) {
+		uds_free_open_chapter(open_chapter);
+		return result;
+	}
+
+	*open_chapter_ptr = open_chapter;
+	return UDS_SUCCESS;
+}
+
+void uds_reset_open_chapter(struct open_chapter_zone *open_chapter)
+{
+	open_chapter->size = 0;
+	open_chapter->deletions = 0;
+
+	memset(open_chapter->records, 0, records_size(open_chapter));
+	memset(open_chapter->slots, 0, slots_size(open_chapter->slot_count));
+}
+
+static unsigned int probe_chapter_slots(struct open_chapter_zone *open_chapter,
+					const struct uds_record_name *name)
+{
+	struct uds_volume_record *record;
+	unsigned int slot_count = open_chapter->slot_count;
+	unsigned int slot = uds_name_to_hash_slot(name, slot_count);
+	unsigned int record_number;
+	unsigned int attempts = 1;
+
+	while (true) {
+		record_number = open_chapter->slots[slot].record_number;
+
+		/*
+		 * If the hash slot is empty, we've reached the end of a chain without finding the
+		 * record and should terminate the search.
+		 */
+		if (record_number == 0)
+			return slot;
+
+		/*
+		 * If the name of the record referenced by the slot matches and has not been
+		 * deleted, then we've found the requested name.
+		 */
+		record = &open_chapter->records[record_number];
+		if ((memcmp(&record->name, name, UDS_RECORD_NAME_SIZE) == 0) &&
+		    !open_chapter->slots[record_number].deleted)
+			return slot;
+
+		/*
+		 * Quadratic probing: advance the probe by 1, 2, 3, etc. and try again. This
+		 * performs better than linear probing and works best for 2^N slots.
+		 */
+		slot = (slot + attempts++) % slot_count;
+	}
+}
+
+void uds_search_open_chapter(struct open_chapter_zone *open_chapter,
+			     const struct uds_record_name *name,
+			     struct uds_record_data *metadata, bool *found)
+{
+	unsigned int slot;
+	unsigned int record_number;
+
+	slot = probe_chapter_slots(open_chapter, name);
+	record_number = open_chapter->slots[slot].record_number;
+	if (record_number == 0) {
+		*found = false;
+	} else {
+		*found = true;
+		*metadata = open_chapter->records[record_number].data;
+	}
+}
+
+/* Add a record to the open chapter zone and return the remaining space. */
+int uds_put_open_chapter(struct open_chapter_zone *open_chapter,
+			 const struct uds_record_name *name,
+			 const struct uds_record_data *metadata)
+{
+	unsigned int slot;
+	unsigned int record_number;
+	struct uds_volume_record *record;
+
+	if (open_chapter->size >= open_chapter->capacity)
+		return 0;
+
+	slot = probe_chapter_slots(open_chapter, name);
+	record_number = open_chapter->slots[slot].record_number;
+
+	if (record_number == 0) {
+		record_number = ++open_chapter->size;
+		open_chapter->slots[slot].record_number = record_number;
+	}
+
+	record = &open_chapter->records[record_number];
+	record->name = *name;
+	record->data = *metadata;
+
+	return open_chapter->capacity - open_chapter->size;
+}
+
+void uds_remove_from_open_chapter(struct open_chapter_zone *open_chapter,
+				  const struct uds_record_name *name)
+{
+	unsigned int slot;
+	unsigned int record_number;
+
+	slot = probe_chapter_slots(open_chapter, name);
+	record_number = open_chapter->slots[slot].record_number;
+
+	if (record_number > 0) {
+		open_chapter->slots[record_number].deleted = true;
+		open_chapter->deletions += 1;
+	}
+}
+
+void uds_free_open_chapter(struct open_chapter_zone *open_chapter)
+{
+	if (open_chapter != NULL) {
+		uds_free(open_chapter->records);
+		uds_free(open_chapter);
+	}
+}
+
+/* Map each record name to its record page number in the delta chapter index. */
+static int fill_delta_chapter_index(struct open_chapter_zone **chapter_zones,
+				    unsigned int zone_count,
+				    struct open_chapter_index *index,
+				    struct uds_volume_record *collated_records)
+{
+	int result;
+	unsigned int records_per_chapter;
+	unsigned int records_per_page;
+	unsigned int record_index;
+	unsigned int records = 0;
+	u32 page_number;
+	unsigned int z;
+	int overflow_count = 0;
+	struct uds_volume_record *fill_record = NULL;
+
+	/*
+	 * The record pages should not have any empty space, so find a record with which to fill
+	 * the chapter zone if it was closed early, and also to replace any deleted records. The
+	 * last record in any filled zone is guaranteed to not have been deleted, so use one of
+	 * those.
+	 */
+	for (z = 0; z < zone_count; z++) {
+		struct open_chapter_zone *zone = chapter_zones[z];
+
+		if (zone->size == zone->capacity) {
+			fill_record = &zone->records[zone->size];
+			break;
+		}
+	}
+
+	records_per_chapter = index->geometry->records_per_chapter;
+	records_per_page = index->geometry->records_per_page;
+
+	for (records = 0; records < records_per_chapter; records++) {
+		struct uds_volume_record *record = &collated_records[records];
+		struct open_chapter_zone *open_chapter;
+
+		/* The record arrays in the zones are 1-based. */
+		record_index = 1 + (records / zone_count);
+		page_number = records / records_per_page;
+		open_chapter = chapter_zones[records % zone_count];
+
+		/* Use the fill record in place of an unused record. */
+		if (record_index > open_chapter->size ||
+		    open_chapter->slots[record_index].deleted) {
+			*record = *fill_record;
+			continue;
+		}
+
+		*record = open_chapter->records[record_index];
+		result = uds_put_open_chapter_index_record(index, &record->name,
+							   page_number);
+		switch (result) {
+		case UDS_SUCCESS:
+			break;
+		case UDS_OVERFLOW:
+			overflow_count++;
+			break;
+		default:
+			uds_log_error_strerror(result,
+					       "failed to build open chapter index");
+			return result;
+		}
+	}
+
+	if (overflow_count > 0)
+		uds_log_warning("Failed to add %d entries to chapter index",
+				overflow_count);
+
+	return UDS_SUCCESS;
+}
+
+int uds_close_open_chapter(struct open_chapter_zone **chapter_zones,
+			   unsigned int zone_count, struct volume *volume,
+			   struct open_chapter_index *chapter_index,
+			   struct uds_volume_record *collated_records,
+			   u64 virtual_chapter_number)
+{
+	int result;
+
+	uds_empty_open_chapter_index(chapter_index, virtual_chapter_number);
+	result = fill_delta_chapter_index(chapter_zones, zone_count, chapter_index,
+					  collated_records);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	return uds_write_chapter(volume, chapter_index, collated_records);
+}
+
+int uds_save_open_chapter(struct uds_index *index, struct buffered_writer *writer)
+{
+	int result;
+	struct open_chapter_zone *open_chapter;
+	struct uds_volume_record *record;
+	u8 record_count_data[sizeof(u32)];
+	u32 record_count = 0;
+	unsigned int record_index;
+	unsigned int z;
+
+	result = uds_write_to_buffered_writer(writer, OPEN_CHAPTER_MAGIC,
+					      OPEN_CHAPTER_MAGIC_LENGTH);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	result = uds_write_to_buffered_writer(writer, OPEN_CHAPTER_VERSION,
+					      OPEN_CHAPTER_VERSION_LENGTH);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	for (z = 0; z < index->zone_count; z++) {
+		open_chapter = index->zones[z]->open_chapter;
+		record_count += open_chapter->size - open_chapter->deletions;
+	}
+
+	put_unaligned_le32(record_count, record_count_data);
+	result = uds_write_to_buffered_writer(writer, record_count_data,
+					      sizeof(record_count_data));
+	if (result != UDS_SUCCESS)
+		return result;
+
+	record_index = 1;
+	while (record_count > 0) {
+		for (z = 0; z < index->zone_count; z++) {
+			open_chapter = index->zones[z]->open_chapter;
+			if (record_index > open_chapter->size)
+				continue;
+
+			if (open_chapter->slots[record_index].deleted)
+				continue;
+
+			record = &open_chapter->records[record_index];
+			result = uds_write_to_buffered_writer(writer, (u8 *) record,
+							      sizeof(*record));
+			if (result != UDS_SUCCESS)
+				return result;
+
+			record_count--;
+		}
+
+		record_index++;
+	}
+
+	return uds_flush_buffered_writer(writer);
+}
+
+u64 uds_compute_saved_open_chapter_size(struct geometry *geometry)
+{
+	unsigned int records_per_chapter = geometry->records_per_chapter;
+
+	return OPEN_CHAPTER_MAGIC_LENGTH + OPEN_CHAPTER_VERSION_LENGTH + sizeof(u32) +
+		records_per_chapter * sizeof(struct uds_volume_record);
+}
+
+static int load_version20(struct uds_index *index, struct buffered_reader *reader)
+{
+	int result;
+	u32 record_count;
+	u8 record_count_data[sizeof(u32)];
+	struct uds_volume_record record;
+
+	/*
+	 * Track which zones cannot accept any more records. If the open chapter had a different
+	 * number of zones previously, some new zones may have more records than they have space
+	 * for. These overflow records will be discarded.
+	 */
+	bool full_flags[MAX_ZONES] = {
+		false,
+	};
+
+	result = uds_read_from_buffered_reader(reader, (u8 *) &record_count_data,
+					       sizeof(record_count_data));
+	if (result != UDS_SUCCESS)
+		return result;
+
+	record_count = get_unaligned_le32(record_count_data);
+	while (record_count-- > 0) {
+		unsigned int zone = 0;
+
+		result = uds_read_from_buffered_reader(reader, (u8 *) &record,
+						       sizeof(record));
+		if (result != UDS_SUCCESS)
+			return result;
+
+		if (index->zone_count > 1)
+			zone = uds_get_volume_index_zone(index->volume_index,
+							 &record.name);
+
+		if (!full_flags[zone]) {
+			struct open_chapter_zone *open_chapter;
+			unsigned int remaining;
+
+			open_chapter = index->zones[zone]->open_chapter;
+			remaining = uds_put_open_chapter(open_chapter, &record.name,
+							 &record.data);
+			/* Do not allow any zone to fill completely. */
+			full_flags[zone] = (remaining <= 1);
+		}
+	}
+
+	return UDS_SUCCESS;
+}
+
+int uds_load_open_chapter(struct uds_index *index, struct buffered_reader *reader)
+{
+	u8 version[OPEN_CHAPTER_VERSION_LENGTH];
+	int result;
+
+	result = uds_verify_buffered_data(reader, OPEN_CHAPTER_MAGIC,
+					  OPEN_CHAPTER_MAGIC_LENGTH);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	result = uds_read_from_buffered_reader(reader, version, sizeof(version));
+	if (result != UDS_SUCCESS)
+		return result;
+
+	if (memcmp(OPEN_CHAPTER_VERSION, version, sizeof(version)) != 0) {
+		return uds_log_error_strerror(UDS_CORRUPT_DATA,
+					      "Invalid open chapter version: %.*s",
+					      (int) sizeof(version), version);
+	}
+
+	return load_version20(index, reader);
+}
diff --git a/drivers/md/dm-vdo/open-chapter.h b/drivers/md/dm-vdo/open-chapter.h
new file mode 100644
index 000000000000..eb11d897f20a
--- /dev/null
+++ b/drivers/md/dm-vdo/open-chapter.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#ifndef UDS_OPEN_CHAPTER_H
+#define UDS_OPEN_CHAPTER_H
+
+#include "chapter-index.h"
+#include "geometry.h"
+#include "index.h"
+#include "volume.h"
+
+/*
+ * The open chapter tracks the newest records in memory. Like the index as a whole, each open
+ * chapter is divided into a number of independent zones which are interleaved when the chapter is
+ * committed to the volume.
+ */
+
+enum {
+	OPEN_CHAPTER_RECORD_NUMBER_BITS = 23,
+};
+
+struct open_chapter_zone_slot {
+	/* If non-zero, the record number addressed by this hash slot */
+	unsigned int record_number : OPEN_CHAPTER_RECORD_NUMBER_BITS;
+	/* If true, the record at the index of this hash slot was deleted */
+	bool deleted : 1;
+} __packed;
+
+struct open_chapter_zone {
+	/* The maximum number of records that can be stored */
+	unsigned int capacity;
+	/* The number of records stored */
+	unsigned int size;
+	/* The number of deleted records */
+	unsigned int deletions;
+	/* Array of chunk records, 1-based */
+	struct uds_volume_record *records;
+	/* The number of slots in the hash table */
+	unsigned int slot_count;
+	/* The hash table slots, referencing virtual record numbers */
+	struct open_chapter_zone_slot slots[];
+};
+
+int __must_check uds_make_open_chapter(const struct geometry *geometry,
+				       unsigned int zone_count,
+				       struct open_chapter_zone **open_chapter_ptr);
+
+void uds_reset_open_chapter(struct open_chapter_zone *open_chapter);
+
+void uds_search_open_chapter(struct open_chapter_zone *open_chapter,
+			     const struct uds_record_name *name,
+			     struct uds_record_data *metadata, bool *found);
+
+int __must_check uds_put_open_chapter(struct open_chapter_zone *open_chapter,
+				      const struct uds_record_name *name,
+				      const struct uds_record_data *metadata);
+
+void uds_remove_from_open_chapter(struct open_chapter_zone *open_chapter,
+				  const struct uds_record_name *name);
+
+void uds_free_open_chapter(struct open_chapter_zone *open_chapter);
+
+int __must_check uds_close_open_chapter(struct open_chapter_zone **chapter_zones,
+					unsigned int zone_count, struct volume *volume,
+					struct open_chapter_index *chapter_index,
+					struct uds_volume_record *collated_records,
+					u64 virtual_chapter_number);
+
+int __must_check uds_save_open_chapter(struct uds_index *index,
+				       struct buffered_writer *writer);
+
+int __must_check uds_load_open_chapter(struct uds_index *index,
+				       struct buffered_reader *reader);
+
+u64 uds_compute_saved_open_chapter_size(struct geometry *geometry);
+
+#endif /* UDS_OPEN_CHAPTER_H */