/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright 2023 Red Hat
*/
#ifndef UDS_DELTA_INDEX_H
#define UDS_DELTA_INDEX_H
#include <linux/cache.h>
#include "numeric.h"
#include "time-utils.h"
#include "config.h"
#include "io-factory.h"
/*
* A delta index is a key-value store, where each entry maps an address (the key) to a payload (the
* value). The entries are sorted by address, and only the delta between successive addresses is
* stored in the entry. The addresses are assumed to be uniformly distributed, and the deltas are
* therefore exponentially distributed.
*
* A delta_index can either be mutable or immutable depending on its expected use. The immutable
* form of a delta index is used for the indexes of closed chapters committed to the volume. The
* mutable form of a delta index is used by the volume index, and also by the chapter index in an
* open chapter. Like the index as a whole, each mutable delta index is divided into a number of
* independent zones.
*/
struct delta_list {
/* The offset of the delta list start, in bits */
u64 start;
/* The number of bits in the delta list */
u16 size;
/* Where the last search "found" the key, in bits */
u16 save_offset;
/* The key for the record just before save_offset */
u32 save_key;
};
struct delta_zone {
/* The delta list memory */
u8 *memory;
/* The delta list headers */
struct delta_list *delta_lists;
/* Temporary starts of delta lists */
u64 *new_offsets;
/* Buffered writer for saving an index */
struct buffered_writer *buffered_writer;
/* The size of delta list memory */
size_t size;
/* Nanoseconds spent rebalancing */
ktime_t rebalance_time;
/* Number of memory rebalances */
u32 rebalance_count;
/* The number of bits in a stored value */
u8 value_bits;
/* The number of bits in the minimal key code */
u16 min_bits;
/* The number of keys used in a minimal code */
u32 min_keys;
/* The number of keys used for another code bit */
u32 incr_keys;
/* The number of records in the index */
u64 record_count;
/* The number of collision records */
u64 collision_count;
/* The number of records removed */
u64 discard_count;
/* The number of UDS_OVERFLOW errors detected */
u64 overflow_count;
/* The index of the first delta list */
u32 first_list;
/* The number of delta lists */
u32 list_count;
/* Tag belonging to this delta index */
u8 tag;
} __aligned(L1_CACHE_BYTES);
struct delta_list_save_info {
/* Tag identifying which delta index this list is in */
u8 tag;
/* Bit offset of the start of the list data */
u8 bit_offset;
/* Number of bytes of list data */
u16 byte_count;
/* The delta list number within the delta index */
u32 index;
} __packed;
struct delta_index {
/* The zones */
struct delta_zone *delta_zones;
/* The number of zones */
unsigned int zone_count;
/* The number of delta lists */
u32 list_count;
/* Maximum lists per zone */
u32 lists_per_zone;
/* Total memory allocated to this index */
size_t memory_size;
/* The number of non-empty lists at load time per zone */
u32 load_lists[MAX_ZONES];
/* True if this index is mutable */
bool mutable;
/* Tag belonging to this delta index */
u8 tag;
};
/*
* A delta_index_page describes a single page of a chapter index. The delta_index field allows the
* page to be treated as an immutable delta_index. We use the delta_zone field to treat the chapter
* index page as a single zone index, and without the need to do an additional memory allocation.
*/
struct delta_index_page {
struct delta_index delta_index;
/* These values are loaded from the delta_page_header */
u32 lowest_list_number;
u32 highest_list_number;
u64 virtual_chapter_number;
/* This structure describes the single zone of a delta index page. */
struct delta_zone delta_zone;
};
/*
* Notes on the delta_index_entries:
*
* The fields documented as "public" can be read by any code that uses a delta_index. The fields
* documented as "private" carry information between delta_index method calls and should not be
* used outside the delta_index module.
*
* (1) The delta_index_entry is used like an iterator when searching a delta list.
*
* (2) It is also the result of a successful search and can be used to refer to the element found
* by the search.
*
* (3) It is also the result of an unsuccessful search and can be used to refer to the insertion
* point for a new record.
*
* (4) If at_end is true, the delta_list entry can only be used as the insertion point for a new
* record at the end of the list.
*
* (5) If at_end is false and is_collision is true, the delta_list entry fields refer to a
* collision entry in the list, and the delta_list entry can be used as a reference to this
* entry.
*
* (6) If at_end is false and is_collision is false, the delta_list entry fields refer to a
* non-collision entry in the list. Such delta_list entries can be used as a reference to a
* found entry, or an insertion point for a non-collision entry before this entry, or an
* insertion point for a collision entry that collides with this entry.
*/
struct delta_index_entry {
/* Public fields */
/* The key for this entry */
u32 key;
/* We are after the last list entry */
bool at_end;
/* This record is a collision */
bool is_collision;
/* Private fields */
/* This delta list overflowed */
bool list_overflow;
/* The number of bits used for the value */
u8 value_bits;
/* The number of bits used for the entire entry */
u16 entry_bits;
/* The delta index zone */
struct delta_zone *delta_zone;
/* The delta list containing the entry */
struct delta_list *delta_list;
/* The delta list number */
u32 list_number;
/* Bit offset of this entry within the list */
u16 offset;
/* The delta between this and previous entry */
u32 delta;
/* Temporary delta list for immutable indices */
struct delta_list temp_delta_list;
};
struct delta_index_stats {
/* Number of bytes allocated */
size_t memory_allocated;
/* Nanoseconds spent rebalancing */
ktime_t rebalance_time;
/* Number of memory rebalances */
u32 rebalance_count;
/* The number of records in the index */
u64 record_count;
/* The number of collision records */
u64 collision_count;
/* The number of records removed */
u64 discard_count;
/* The number of UDS_OVERFLOW errors detected */
u64 overflow_count;
/* The number of delta lists */
u32 list_count;
};
int __must_check uds_initialize_delta_index(struct delta_index *delta_index,
unsigned int zone_count, u32 list_count,
u32 mean_delta, u32 payload_bits,
size_t memory_size, u8 tag);
int __must_check uds_initialize_delta_index_page(struct delta_index_page *delta_index_page,
u64 expected_nonce, u32 mean_delta,
u32 payload_bits, u8 *memory,
size_t memory_size);
void uds_uninitialize_delta_index(struct delta_index *delta_index);
void uds_reset_delta_index(const struct delta_index *delta_index);
int __must_check uds_pack_delta_index_page(const struct delta_index *delta_index,
u64 header_nonce, u8 *memory,
size_t memory_size,
u64 virtual_chapter_number, u32 first_list,
u32 *list_count);
int __must_check uds_start_restoring_delta_index(struct delta_index *delta_index,
struct buffered_reader **buffered_readers,
unsigned int reader_count);
int __must_check uds_finish_restoring_delta_index(struct delta_index *delta_index,
struct buffered_reader **buffered_readers,
unsigned int reader_count);
int __must_check uds_check_guard_delta_lists(struct buffered_reader **buffered_readers,
unsigned int reader_count);
int __must_check uds_start_saving_delta_index(const struct delta_index *delta_index,
unsigned int zone_number,
struct buffered_writer *buffered_writer);
int __must_check uds_finish_saving_delta_index(const struct delta_index *delta_index,
unsigned int zone_number);
int __must_check uds_write_guard_delta_list(struct buffered_writer *buffered_writer);
size_t __must_check uds_compute_delta_index_save_bytes(u32 list_count,
size_t memory_size);
int __must_check uds_start_delta_index_search(const struct delta_index *delta_index,
u32 list_number, u32 key,
struct delta_index_entry *iterator);
int __must_check uds_next_delta_index_entry(struct delta_index_entry *delta_entry);
int __must_check uds_remember_delta_index_offset(const struct delta_index_entry *delta_entry);
int __must_check uds_get_delta_index_entry(const struct delta_index *delta_index,
u32 list_number, u32 key, const u8 *name,
struct delta_index_entry *delta_entry);
int __must_check uds_get_delta_entry_collision(const struct delta_index_entry *delta_entry,
u8 *name);
u32 __must_check uds_get_delta_entry_value(const struct delta_index_entry *delta_entry);
int __must_check uds_set_delta_entry_value(const struct delta_index_entry *delta_entry, u32 value);
int __must_check uds_put_delta_index_entry(struct delta_index_entry *delta_entry, u32 key,
u32 value, const u8 *name);
int __must_check uds_remove_delta_index_entry(struct delta_index_entry *delta_entry);
void uds_get_delta_index_stats(const struct delta_index *delta_index,
struct delta_index_stats *stats);
size_t __must_check uds_compute_delta_index_size(u32 entry_count, u32 mean_delta,
u32 payload_bits);
u32 uds_get_delta_index_page_count(u32 entry_count, u32 list_count, u32 mean_delta,
u32 payload_bits, size_t bytes_per_page);
void uds_log_delta_index_entry(struct delta_index_entry *delta_entry);
#endif /* UDS_DELTA_INDEX_H */
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