1 files changed, 173 insertions, 0 deletions
diff --git a/drivers/md/dm-vdo/indexer/index-page-map.c b/drivers/md/dm-vdo/indexer/index-page-map.c
new file mode 100644
index 000000000000..00b44e07d0c1
--- /dev/null
+++ b/drivers/md/dm-vdo/indexer/index-page-map.c
@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "index-page-map.h"
+
+#include "errors.h"
+#include "logger.h"
+#include "memory-alloc.h"
+#include "numeric.h"
+#include "permassert.h"
+#include "string-utils.h"
+#include "thread-utils.h"
+
+#include "hash-utils.h"
+#include "indexer.h"
+
+/*
+ * The index page map is conceptually a two-dimensional array indexed by chapter number and index
+ * page number within the chapter. Each entry contains the number of the last delta list on that
+ * index page. In order to save memory, the information for the last page in each chapter is not
+ * recorded, as it is known from the geometry.
+ */
+
+static const u8 PAGE_MAP_MAGIC[] = "ALBIPM02";
+
+#define PAGE_MAP_MAGIC_LENGTH (sizeof(PAGE_MAP_MAGIC) - 1)
+
+static inline u32 get_entry_count(const struct index_geometry *geometry)
+{
+	return geometry->chapters_per_volume * (geometry->index_pages_per_chapter - 1);
+}
+
+int uds_make_index_page_map(const struct index_geometry *geometry,
+			    struct index_page_map **map_ptr)
+{
+	int result;
+	struct index_page_map *map;
+
+	result = vdo_allocate(1, struct index_page_map, "page map", &map);
+	if (result != VDO_SUCCESS)
+		return result;
+
+	map->geometry = geometry;
+	map->entries_per_chapter = geometry->index_pages_per_chapter - 1;
+	result = vdo_allocate(get_entry_count(geometry), u16, "Index Page Map Entries",
+			      &map->entries);
+	if (result != VDO_SUCCESS) {
+		uds_free_index_page_map(map);
+		return result;
+	}
+
+	*map_ptr = map;
+	return UDS_SUCCESS;
+}
+
+void uds_free_index_page_map(struct index_page_map *map)
+{
+	if (map != NULL) {
+		vdo_free(map->entries);
+		vdo_free(map);
+	}
+}
+
+void uds_update_index_page_map(struct index_page_map *map, u64 virtual_chapter_number,
+			       u32 chapter_number, u32 index_page_number,
+			       u32 delta_list_number)
+{
+	size_t slot;
+
+	map->last_update = virtual_chapter_number;
+	if (index_page_number == map->entries_per_chapter)
+		return;
+
+	slot = (chapter_number * map->entries_per_chapter) + index_page_number;
+	map->entries[slot] = delta_list_number;
+}
+
+u32 uds_find_index_page_number(const struct index_page_map *map,
+			       const struct uds_record_name *name, u32 chapter_number)
+{
+	u32 delta_list_number = uds_hash_to_chapter_delta_list(name, map->geometry);
+	u32 slot = chapter_number * map->entries_per_chapter;
+	u32 page;
+
+	for (page = 0; page < map->entries_per_chapter; page++) {
+		if (delta_list_number <= map->entries[slot + page])
+			break;
+	}
+
+	return page;
+}
+
+void uds_get_list_number_bounds(const struct index_page_map *map, u32 chapter_number,
+				u32 index_page_number, u32 *lowest_list,
+				u32 *highest_list)
+{
+	u32 slot = chapter_number * map->entries_per_chapter;
+
+	*lowest_list = ((index_page_number == 0) ?
+			0 : map->entries[slot + index_page_number - 1] + 1);
+	*highest_list = ((index_page_number < map->entries_per_chapter) ?
+			 map->entries[slot + index_page_number] :
+			 map->geometry->delta_lists_per_chapter - 1);
+}
+
+u64 uds_compute_index_page_map_save_size(const struct index_geometry *geometry)
+{
+	return PAGE_MAP_MAGIC_LENGTH + sizeof(u64) + sizeof(u16) * get_entry_count(geometry);
+}
+
+int uds_write_index_page_map(struct index_page_map *map, struct buffered_writer *writer)
+{
+	int result;
+	u8 *buffer;
+	size_t offset = 0;
+	u64 saved_size = uds_compute_index_page_map_save_size(map->geometry);
+	u32 i;
+
+	result = vdo_allocate(saved_size, u8, "page map data", &buffer);
+	if (result != VDO_SUCCESS)
+		return result;
+
+	memcpy(buffer, PAGE_MAP_MAGIC, PAGE_MAP_MAGIC_LENGTH);
+	offset += PAGE_MAP_MAGIC_LENGTH;
+	encode_u64_le(buffer, &offset, map->last_update);
+	for (i = 0; i < get_entry_count(map->geometry); i++)
+		encode_u16_le(buffer, &offset, map->entries[i]);
+
+	result = uds_write_to_buffered_writer(writer, buffer, offset);
+	vdo_free(buffer);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	return uds_flush_buffered_writer(writer);
+}
+
+int uds_read_index_page_map(struct index_page_map *map, struct buffered_reader *reader)
+{
+	int result;
+	u8 magic[PAGE_MAP_MAGIC_LENGTH];
+	u8 *buffer;
+	size_t offset = 0;
+	u64 saved_size = uds_compute_index_page_map_save_size(map->geometry);
+	u32 i;
+
+	result = vdo_allocate(saved_size, u8, "page map data", &buffer);
+	if (result != VDO_SUCCESS)
+		return result;
+
+	result = uds_read_from_buffered_reader(reader, buffer, saved_size);
+	if (result != UDS_SUCCESS) {
+		vdo_free(buffer);
+		return result;
+	}
+
+	memcpy(&magic, buffer, PAGE_MAP_MAGIC_LENGTH);
+	offset += PAGE_MAP_MAGIC_LENGTH;
+	if (memcmp(magic, PAGE_MAP_MAGIC, PAGE_MAP_MAGIC_LENGTH) != 0) {
+		vdo_free(buffer);
+		return UDS_CORRUPT_DATA;
+	}
+
+	decode_u64_le(buffer, &offset, &map->last_update);
+	for (i = 0; i < get_entry_count(map->geometry); i++)
+		decode_u16_le(buffer, &offset, &map->entries[i]);
+
+	vdo_free(buffer);
+	vdo_log_debug("read index page map, last update %llu",
+		      (unsigned long long) map->last_update);
+	return UDS_SUCCESS;
+}