// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright 2023 Red Hat
*/
#include "open-chapter.h"
#include <linux/log2.h>
#include "logger.h"
#include "memory-alloc.h"
#include "numeric.h"
#include "permassert.h"
#include "config.h"
#include "hash-utils.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";
#define OPEN_CHAPTER_MAGIC_LENGTH (sizeof(OPEN_CHAPTER_MAGIC) - 1)
#define OPEN_CHAPTER_VERSION_LENGTH (sizeof(OPEN_CHAPTER_VERSION) - 1)
#define 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 index_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 = vdo_allocate_extended(struct open_chapter_zone, slot_count,
struct open_chapter_zone_slot, "open chapter",
&open_chapter);
if (result != VDO_SUCCESS)
return result;
open_chapter->slot_count = slot_count;
open_chapter->capacity = capacity;
result = vdo_allocate_cache_aligned(records_size(open_chapter), "record pages",
&open_chapter->records);
if (result != VDO_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) {
vdo_free(open_chapter->records);
vdo_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:
vdo_log_error_strerror(result,
"failed to build open chapter index");
return result;
}
}
if (overflow_count > 0)
vdo_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 index_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 vdo_log_error_strerror(UDS_CORRUPT_DATA,
"Invalid open chapter version: %.*s",
(int) sizeof(version), version);
}
return load_version20(index, reader);
}
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