new file mode 100644
@@ -0,0 +1,2018 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright Red Hat
+ */
+#include "delta-index.h"
+
+#include <linux/bitops.h>
+#include <linux/bits.h>
+#include <linux/compiler.h>
+#include <linux/limits.h>
+#include <linux/log2.h>
+
+#include "config.h"
+#include "cpu.h"
+#include "errors.h"
+#include "logger.h"
+#include "memory-alloc.h"
+#include "numeric.h"
+#include "permassert.h"
+#include "string-utils.h"
+#include "time-utils.h"
+#include "uds.h"
+
+/*
+ * The entries in a delta index could be stored in a single delta list, but to reduce search times
+ * and update costs it uses multiple delta lists. These lists are stored in a single chunk of
+ * memory managed by the delta_zone structure. The delta_zone can move the data around within its
+ * memory, so the location of each delta list is recorded as a bit offset into the memory. Because
+ * the volume index can contain over a million delta lists, we want to be efficient with the size
+ * of the delta list header information. This information is encoded into 16 bytes per list. The
+ * volume index delta list memory can easily exceed 4 gigabits, so a 64 bit value is needed to
+ * address the memory. The volume index delta lists average around 6 kilobits, so 16 bits are
+ * sufficient to store the size of a delta list.
+ *
+ * Each delta list is stored as a bit stream. Within the delta list encoding, bits and bytes are
+ * numbered in little endian order. Within a byte, bit 0 is the least significant bit (0x1), and
+ * bit 7 is the most significant bit (0x80). Within a bit stream, bit 7 is the most signficant bit
+ * of byte 0, and bit 8 is the least significant bit of byte 1. Within a byte array, a byte's
+ * number corresponds to its index in the array.
+ *
+ * A standard delta list entry is stored as a fixed length payload (the value) followed by a
+ * variable length key (the delta). A collision entry is used when two block names have the same
+ * delta list address. A collision entry always follows a standard entry for the hash with which it
+ * collides, and is encoded with DELTA == 0 with an additional 256 bits field at the end,
+ * containing the full block name. An entry with a delta of 0 at the beginning of a delta list
+ * indicates a normal entry.
+ *
+ * The delta in each entry is encoded with a variable-length Huffman code to minimize the memory
+ * used by small deltas. The Huffman code is specified by three parameters, which can be computed
+ * from the desired mean delta when the index is full. (See compute_coding constants() for
+ * details.)
+ *
+ * The bit field utilities used to read and write delta entries assume that it is possible to read
+ * some bytes beyond the end of the bit field, so a delta_zone memory allocation is guarded by two
+ * invalid delta lists to prevent reading outside the delta_zone memory. The valid delta lists are
+ * numbered 1 to N, and the guard lists are numbered 0 and N+1. The function to decode the bit
+ * stream include a step that skips over bits set to 0 until the first 1 bit is found. A corrupted
+ * delta list could cause this step to run off the end of the delta_zone memory, so as extra
+ * protection against this happening, the tail guard list is set to all ones.
+ *
+ * The delta_index supports two different forms. The mutable form is created by
+ * uds_initialize_delta_index(), and is used for the volume index and for open chapter indexes. The
+ * immutable form is created by uds_initialize_delta_index_page(), and is used for closed (and
+ * cached) chapter index pages. The immutable form does not allocate delta list headers or
+ * temporary offsets, and thus is somewhat more memory efficient.
+ */
+
+/*
+ * This is the largest field size supported by get_field() and set_field(). Any field that is
+ * larger is not guaranteed to fit in a single byte-aligned u32.
+ */
+enum {
+ MAX_FIELD_BITS = (sizeof(u32) - 1) * BITS_PER_BYTE + 1,
+};
+
+/*
+ * This is the largest field size supported by get_big_field() and set_big_field(). Any field that
+ * is larger is not guaranteed to fit in a single byte-aligned u64.
+ */
+enum {
+ MAX_BIG_FIELD_BITS = (sizeof(u64) - 1) * BITS_PER_BYTE + 1,
+};
+
+/*
+ * This is the number of guard bytes needed at the end of the memory byte array when using the bit
+ * utilities. These utilities call get_big_field() and set_big_field(), which can access up to 7
+ * bytes beyond the end of the desired field. The definition is written to make it clear how this
+ * value is derived.
+ */
+enum {
+ POST_FIELD_GUARD_BYTES = sizeof(u64) - 1,
+};
+
+/* The number of guard bits that are needed in the tail guard list */
+enum {
+ GUARD_BITS = POST_FIELD_GUARD_BYTES * BITS_PER_BYTE
+};
+
+/*
+ * The maximum size of a single delta list in bytes. We count guard bytes in this value because a
+ * buffer of this size can be used with move_bits().
+ */
+enum {
+ DELTA_LIST_MAX_BYTE_COUNT =
+ ((U16_MAX + BITS_PER_BYTE) / BITS_PER_BYTE + POST_FIELD_GUARD_BYTES)
+};
+
+/* The number of extra bytes and bits needed to store a collision entry */
+enum {
+ COLLISION_BYTES = UDS_RECORD_NAME_SIZE,
+ COLLISION_BITS = COLLISION_BYTES * BITS_PER_BYTE
+};
+
+/*
+ * Immutable delta lists are packed into pages containing a header that encodes the delta list
+ * information into 19 bits per list (64KB bit offset).
+ */
+
+enum { IMMUTABLE_HEADER_SIZE = 19 };
+
+/*
+ * Constants and structures for the saved delta index. "DI" is for delta_index, and -##### is a
+ * number to increment when the format of the data changes.
+ */
+
+enum {
+ MAGIC_SIZE = 8,
+};
+
+static const char DELTA_INDEX_MAGIC[] = "DI-00002";
+
+struct delta_index_header {
+ char magic[MAGIC_SIZE];
+ u32 zone_number;
+ u32 zone_count;
+ u32 first_list;
+ u32 list_count;
+ u64 record_count;
+ u64 collision_count;
+};
+
+/*
+ * Header data used for immutable delta index pages. This data is followed by the delta list offset
+ * table.
+ */
+struct delta_page_header {
+ /* Externally-defined nonce */
+ u64 nonce;
+ /* The virtual chapter number */
+ u64 virtual_chapter_number;
+ /* Index of the first delta list on the page */
+ u16 first_list;
+ /* Number of delta lists on the page */
+ u16 list_count;
+} __packed;
+
+static inline u64 get_delta_list_byte_start(const struct delta_list *delta_list)
+{
+ return delta_list->start / BITS_PER_BYTE;
+}
+
+static inline u16 get_delta_list_byte_size(const struct delta_list *delta_list)
+{
+ unsigned int bit_offset = delta_list->start % BITS_PER_BYTE;
+
+ return BITS_TO_BYTES(bit_offset + delta_list->size);
+}
+
+static void rebalance_delta_zone(const struct delta_zone *delta_zone, u32 first, u32 last)
+{
+ struct delta_list *delta_list;
+ u64 new_start;
+
+ if (first == last) {
+ /* Only one list is moving, and we know there is space. */
+ delta_list = &delta_zone->delta_lists[first];
+ new_start = delta_zone->new_offsets[first];
+ if (delta_list->start != new_start) {
+ u64 source;
+ u64 destination;
+
+ source = get_delta_list_byte_start(delta_list);
+ delta_list->start = new_start;
+ destination = get_delta_list_byte_start(delta_list);
+ memmove(delta_zone->memory + destination,
+ delta_zone->memory + source,
+ get_delta_list_byte_size(delta_list));
+ }
+ } else {
+ /*
+ * There is more than one list. Divide the problem in half, and use recursive calls
+ * to process each half. Note that after this computation, first <= middle, and
+ * middle < last.
+ */
+ u32 middle = (first + last) / 2;
+
+ delta_list = &delta_zone->delta_lists[middle];
+ new_start = delta_zone->new_offsets[middle];
+
+ /*
+ * The direction that our middle list is moving determines which half of the
+ * problem must be processed first.
+ */
+ if (new_start > delta_list->start) {
+ rebalance_delta_zone(delta_zone, middle + 1, last);
+ rebalance_delta_zone(delta_zone, first, middle);
+ } else {
+ rebalance_delta_zone(delta_zone, first, middle);
+ rebalance_delta_zone(delta_zone, middle + 1, last);
+ }
+ }
+}
+
+static inline size_t get_zone_memory_size(unsigned int zone_count, size_t memory_size)
+{
+ /* Round up so that each zone is a multiple of 64K in size. */
+ enum {
+ ALLOC_BOUNDARY = 64 * 1024,
+ };
+
+ return (memory_size / zone_count + ALLOC_BOUNDARY - 1) & -ALLOC_BOUNDARY;
+}
+
+void uds_reset_delta_index(const struct delta_index *delta_index)
+{
+ unsigned int z;
+
+ /*
+ * Initialize all delta lists to be empty. We keep 2 extra delta list descriptors, one
+ * before the first real entry and one after so that we don't need to bounds check the
+ * array access when calculating preceding and following gap sizes.
+ */
+ for (z = 0; z < delta_index->zone_count; z++) {
+ u64 list_bits;
+ u64 spacing;
+ u64 offset;
+ unsigned int i;
+ struct delta_zone *zone = &delta_index->delta_zones[z];
+ struct delta_list *delta_lists = zone->delta_lists;
+
+ /* Zeroing the delta list headers initializes the head guard list correctly. */
+ memset(delta_lists, 0, (zone->list_count + 2) * sizeof(struct delta_list));
+
+ /* Set all the bits in the end guard list. */
+ list_bits = (u64) zone->size * BITS_PER_BYTE - GUARD_BITS;
+ delta_lists[zone->list_count + 1].start = list_bits;
+ delta_lists[zone->list_count + 1].size = GUARD_BITS;
+ memset(zone->memory + (list_bits / BITS_PER_BYTE), ~0, POST_FIELD_GUARD_BYTES);
+
+ /* Evenly space out the real delta lists by setting regular offsets. */
+ spacing = list_bits / zone->list_count;
+ offset = spacing / 2;
+ for (i = 1; i <= zone->list_count; i++) {
+ delta_lists[i].start = offset;
+ offset += spacing;
+ }
+
+ /* Update the statistics. */
+ zone->discard_count += zone->record_count;
+ zone->record_count = 0;
+ zone->collision_count = 0;
+ }
+}
+
+/* Compute the Huffman coding parameters for the given mean delta. The Huffman code is specified by
+ * three parameters:
+ *
+ * MINBITS The number of bits in the smallest code
+ * BASE The number of values coded using a code of length MINBITS
+ * INCR The number of values coded by using one additional bit
+ *
+ * These parameters are related by this equation:
+ *
+ * BASE + INCR == 1 << MINBITS
+ *
+ * The math for the Huffman code of an exponential distribution says that
+ *
+ * INCR = log(2) * MEAN_DELTA
+ *
+ * Then use the smallest MINBITS value so that
+ *
+ * (1 << MINBITS) > INCR
+ *
+ * And then
+ *
+ * BASE = (1 << MINBITS) - INCR
+ *
+ * Now the index can generate a code such that
+ * - The first BASE values code using MINBITS bits.
+ * - The next INCR values code using MINBITS+1 bits.
+ * - The next INCR values code using MINBITS+2 bits.
+ * - (and so on).
+ */
+static void compute_coding_constants(u32 mean_delta, u16 *min_bits, u32 *min_keys, u32 *incr_keys)
+{
+ /*
+ * We want to compute the rounded value of log(2) * mean_delta. Since we cannot always use
+ * floating point, use a really good integer approximation.
+ */
+ *incr_keys = (836158UL * mean_delta + 603160UL) / 1206321UL;
+ *min_bits = bits_per(*incr_keys + 1);
+ *min_keys = (1 << *min_bits) - *incr_keys;
+}
+
+void uds_uninitialize_delta_index(struct delta_index *delta_index)
+{
+ unsigned int z;
+
+ if (delta_index->delta_zones == NULL)
+ return;
+
+ for (z = 0; z < delta_index->zone_count; z++) {
+ UDS_FREE(UDS_FORGET(delta_index->delta_zones[z].new_offsets));
+ UDS_FREE(UDS_FORGET(delta_index->delta_zones[z].delta_lists));
+ UDS_FREE(UDS_FORGET(delta_index->delta_zones[z].memory));
+ }
+
+ UDS_FREE(delta_index->delta_zones);
+ memset(delta_index, 0, sizeof(struct delta_index));
+}
+
+static int initialize_delta_zone(struct delta_zone *delta_zone,
+ size_t size,
+ u32 first_list,
+ u32 list_count,
+ u32 mean_delta,
+ u32 payload_bits,
+ u8 tag)
+{
+ int result;
+
+ result = UDS_ALLOCATE(size, u8, "delta list", &delta_zone->memory);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ result = UDS_ALLOCATE(list_count + 2, u64, "delta list temp", &delta_zone->new_offsets);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ /* Allocate the delta lists. */
+ result = UDS_ALLOCATE(list_count + 2,
+ struct delta_list,
+ "delta lists",
+ &delta_zone->delta_lists);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ compute_coding_constants(mean_delta,
+ &delta_zone->min_bits,
+ &delta_zone->min_keys,
+ &delta_zone->incr_keys);
+ delta_zone->value_bits = payload_bits;
+ delta_zone->buffered_writer = NULL;
+ delta_zone->size = size;
+ delta_zone->rebalance_time = 0;
+ delta_zone->rebalance_count = 0;
+ delta_zone->record_count = 0;
+ delta_zone->collision_count = 0;
+ delta_zone->discard_count = 0;
+ delta_zone->overflow_count = 0;
+ delta_zone->first_list = first_list;
+ delta_zone->list_count = list_count;
+ delta_zone->tag = tag;
+
+ return UDS_SUCCESS;
+}
+
+int 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 result;
+ unsigned int z;
+ size_t zone_memory;
+
+ result = UDS_ALLOCATE(zone_count,
+ struct delta_zone,
+ "Delta Index Zones",
+ &delta_index->delta_zones);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ delta_index->zone_count = zone_count;
+ delta_index->list_count = list_count;
+ delta_index->lists_per_zone = DIV_ROUND_UP(list_count, zone_count);
+ delta_index->memory_size = 0;
+ delta_index->mutable = true;
+ delta_index->tag = tag;
+
+ for (z = 0; z < zone_count; z++) {
+ u32 lists_in_zone = delta_index->lists_per_zone;
+ u32 first_list_in_zone = z * lists_in_zone;
+
+ if (z == zone_count - 1) {
+ /*
+ * The last zone gets fewer lists if zone_count doesn't evenly divide
+ * list_count. We'll have an underflow if the assertion below doesn't hold.
+ */
+ if (delta_index->list_count <= first_list_in_zone) {
+ uds_uninitialize_delta_index(delta_index);
+ return uds_log_error_strerror(UDS_INVALID_ARGUMENT,
+ "%u delta lists not enough for %u zones",
+ list_count,
+ zone_count);
+ }
+ lists_in_zone = delta_index->list_count - first_list_in_zone;
+ }
+
+ zone_memory = get_zone_memory_size(zone_count, memory_size);
+ result = initialize_delta_zone(&delta_index->delta_zones[z],
+ zone_memory,
+ first_list_in_zone,
+ lists_in_zone,
+ mean_delta,
+ payload_bits,
+ tag);
+ if (result != UDS_SUCCESS) {
+ uds_uninitialize_delta_index(delta_index);
+ return result;
+ }
+
+ delta_index->memory_size +=
+ (sizeof(struct delta_zone) + zone_memory +
+ (lists_in_zone + 2) * (sizeof(struct delta_list) + sizeof(u64)));
+ }
+
+ uds_reset_delta_index(delta_index);
+ return UDS_SUCCESS;
+}
+
+/* Read a bit field from an arbitrary bit boundary. */
+static inline u32 get_field(const u8 *memory, u64 offset, u8 size)
+{
+ const void *addr = memory + offset / BITS_PER_BYTE;
+
+ return (get_unaligned_le32(addr) >> (offset % BITS_PER_BYTE)) & ((1 << size) - 1);
+}
+
+/* Write a bit field to an arbitrary bit boundary. */
+static inline void set_field(u32 value, u8 *memory, u64 offset, u8 size)
+{
+ void *addr = memory + offset / BITS_PER_BYTE;
+ int shift = offset % BITS_PER_BYTE;
+ u32 data = get_unaligned_le32(addr);
+
+ data &= ~(((1 << size) - 1) << shift);
+ data |= value << shift;
+ put_unaligned_le32(data, addr);
+}
+
+/* Get the bit offset to the immutable delta list header. */
+static inline u32 get_immutable_header_offset(u32 list_number)
+{
+ return sizeof(struct delta_page_header) * BITS_PER_BYTE +
+ list_number * IMMUTABLE_HEADER_SIZE;
+}
+
+/* Get the bit offset to the start of the immutable delta list bit stream. */
+static inline u32 get_immutable_start(const u8 *memory, u32 list_number)
+{
+ return get_field(memory, get_immutable_header_offset(list_number), IMMUTABLE_HEADER_SIZE);
+}
+
+/* Set the bit offset to the start of the immutable delta list bit stream. */
+static inline void set_immutable_start(u8 *memory, u32 list_number, u32 start)
+{
+ set_field(start, memory, get_immutable_header_offset(list_number), IMMUTABLE_HEADER_SIZE);
+}
+
+static bool verify_delta_index_page(u64 nonce,
+ u16 list_count,
+ u64 expected_nonce,
+ u8 *memory,
+ size_t memory_size)
+{
+ unsigned int i;
+
+ /*
+ * Verify the nonce. A mismatch can happen here during rebuild if we haven't written the
+ * entire volume at least once.
+ */
+ if (nonce != expected_nonce)
+ return false;
+
+ /* Verify that the number of delta lists can fit in the page. */
+ if (list_count > ((memory_size - sizeof(struct delta_page_header)) *
+ BITS_PER_BYTE / IMMUTABLE_HEADER_SIZE))
+ return false;
+
+ /*
+ * Verify that the first delta list is immediately after the last delta
+ * list header.
+ */
+ if (get_immutable_start(memory, 0) != get_immutable_header_offset(list_count + 1))
+ return false;
+
+ /* Verify that the lists are in the correct order. */
+ for (i = 0; i < list_count; i++)
+ if (get_immutable_start(memory, i) > get_immutable_start(memory, i + 1))
+ return false;
+
+ /*
+ * Verify that the last list ends on the page, and that there is room
+ * for the post-field guard bits.
+ */
+ if (get_immutable_start(memory, list_count) >
+ (memory_size - POST_FIELD_GUARD_BYTES) * BITS_PER_BYTE)
+ return false;
+
+ /* Verify that the guard bytes are correctly set to all ones. */
+ for (i = 0; i < POST_FIELD_GUARD_BYTES; i++) {
+ if (memory[memory_size - POST_FIELD_GUARD_BYTES + i] != (u8) ~0)
+ return false;
+ }
+
+ /* All verifications passed. */
+ return true;
+}
+
+/* Initialize a delta index page to refer to a supplied page. */
+int 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)
+{
+ u64 nonce;
+ u64 vcn;
+ u64 first_list;
+ u64 list_count;
+ struct delta_page_header *header = (struct delta_page_header *) memory;
+ struct delta_zone *delta_zone = &delta_index_page->delta_zone;
+ const u8 *nonce_addr = (const u8 *) &header->nonce;
+ const u8 *vcn_addr = (const u8 *) &header->virtual_chapter_number;
+ const u8 *first_list_addr = (const u8 *) &header->first_list;
+ const u8 *list_count_addr = (const u8 *) &header->list_count;
+
+ /* First assume that the header is little endian. */
+ nonce = get_unaligned_le64(nonce_addr);
+ vcn = get_unaligned_le64(vcn_addr);
+ first_list = get_unaligned_le16(first_list_addr);
+ list_count = get_unaligned_le16(list_count_addr);
+ if (!verify_delta_index_page(nonce, list_count, expected_nonce, memory, memory_size)) {
+ /* If that fails, try big endian. */
+ nonce = get_unaligned_be64(nonce_addr);
+ vcn = get_unaligned_be64(vcn_addr);
+ first_list = get_unaligned_be16(first_list_addr);
+ list_count = get_unaligned_be16(list_count_addr);
+ if (!verify_delta_index_page(nonce,
+ list_count,
+ expected_nonce,
+ memory,
+ memory_size))
+ /*
+ * Both attempts failed. Do not log this as an error, because it can happen
+ * during a rebuild if we haven't written the entire volume at least once.
+ */
+ return UDS_CORRUPT_DATA;
+ }
+
+ delta_index_page->delta_index.delta_zones = delta_zone;
+ delta_index_page->delta_index.zone_count = 1;
+ delta_index_page->delta_index.list_count = list_count;
+ delta_index_page->delta_index.lists_per_zone = list_count;
+ delta_index_page->delta_index.mutable = false;
+ delta_index_page->delta_index.tag = 'p';
+ delta_index_page->virtual_chapter_number = vcn;
+ delta_index_page->lowest_list_number = first_list;
+ delta_index_page->highest_list_number = first_list + list_count - 1;
+
+ compute_coding_constants(mean_delta,
+ &delta_zone->min_bits,
+ &delta_zone->min_keys,
+ &delta_zone->incr_keys);
+ delta_zone->value_bits = payload_bits;
+ delta_zone->memory = memory;
+ delta_zone->delta_lists = NULL;
+ delta_zone->new_offsets = NULL;
+ delta_zone->buffered_writer = NULL;
+ delta_zone->size = memory_size;
+ delta_zone->rebalance_time = 0;
+ delta_zone->rebalance_count = 0;
+ delta_zone->record_count = 0;
+ delta_zone->collision_count = 0;
+ delta_zone->discard_count = 0;
+ delta_zone->overflow_count = 0;
+ delta_zone->first_list = 0;
+ delta_zone->list_count = list_count;
+ delta_zone->tag = 'p';
+
+ return UDS_SUCCESS;
+}
+
+/* Read a large bit field from an arbitrary bit boundary. */
+static inline u64 get_big_field(const u8 *memory, u64 offset, u8 size)
+{
+ const void *addr = memory + offset / BITS_PER_BYTE;
+
+ return (get_unaligned_le64(addr) >> (offset % BITS_PER_BYTE)) & ((1UL << size) - 1);
+}
+
+/* Write a large bit field to an arbitrary bit boundary. */
+static inline void set_big_field(u64 value, u8 *memory, u64 offset, u8 size)
+{
+ void *addr = memory + offset / BITS_PER_BYTE;
+ u8 shift = offset % BITS_PER_BYTE;
+ u64 data = get_unaligned_le64(addr);
+
+ data &= ~(((1UL << size) - 1) << shift);
+ data |= value << shift;
+ put_unaligned_le64(data, addr);
+}
+
+/* Set a sequence of bits to all zeros. */
+static inline void set_zero(u8 *memory, u64 offset, u32 size)
+{
+ if (size > 0) {
+ u8 *addr = memory + offset / BITS_PER_BYTE;
+ u8 shift = offset % BITS_PER_BYTE;
+ u32 count = size + shift > BITS_PER_BYTE ? (u32) BITS_PER_BYTE - shift : size;
+
+ *addr++ &= ~(((1 << count) - 1) << shift);
+ for (size -= count; size > BITS_PER_BYTE; size -= BITS_PER_BYTE)
+ *addr++ = 0;
+
+ if (size > 0)
+ *addr &= 0xFF << size;
+ }
+}
+
+/*
+ * Move several bits from a higher to a lower address, moving the lower addressed bits first. The
+ * size and memory offsets are measured in bits.
+ */
+static void move_bits_down(const u8 *from, u64 from_offset, u8 *to, u64 to_offset, u32 size)
+{
+ const u8 *source;
+ u8 *destination;
+ u8 offset;
+ u8 count;
+ u64 field;
+
+ /* Start by moving one field that ends on a to int boundary. */
+ count = (MAX_BIG_FIELD_BITS - ((to_offset + MAX_BIG_FIELD_BITS) % BITS_PER_TYPE(u32)));
+ field = get_big_field(from, from_offset, count);
+ set_big_field(field, to, to_offset, count);
+ from_offset += count;
+ to_offset += count;
+ size -= count;
+
+ /* Now do the main loop to copy 32 bit chunks that are int-aligned at the destination. */
+ offset = from_offset % BITS_PER_TYPE(u32);
+ source = from + (from_offset - offset) / BITS_PER_BYTE;
+ destination = to + to_offset / BITS_PER_BYTE;
+ while (size > MAX_BIG_FIELD_BITS) {
+ put_unaligned_le32(get_unaligned_le64(source) >> offset, destination);
+ source += sizeof(u32);
+ destination += sizeof(u32);
+ from_offset += BITS_PER_TYPE(u32);
+ to_offset += BITS_PER_TYPE(u32);
+ size -= BITS_PER_TYPE(u32);
+ }
+
+ /* Finish up by moving any remaining bits. */
+ if (size > 0) {
+ field = get_big_field(from, from_offset, size);
+ set_big_field(field, to, to_offset, size);
+ }
+}
+
+/*
+ * Move several bits from a lower to a higher address, moving the higher addressed bits first. The
+ * size and memory offsets are measured in bits.
+ */
+static void move_bits_up(const u8 *from, u64 from_offset, u8 *to, u64 to_offset, u32 size)
+{
+ const u8 *source;
+ u8 *destination;
+ u8 offset;
+ u8 count;
+ u64 field;
+
+ /* Start by moving one field that begins on a destination int boundary. */
+ count = (to_offset + size) % BITS_PER_TYPE(u32);
+ if (count > 0) {
+ size -= count;
+ field = get_big_field(from, from_offset + size, count);
+ set_big_field(field, to, to_offset + size, count);
+ }
+
+ /* Now do the main loop to copy 32 bit chunks that are int-aligned at the destination. */
+ offset = (from_offset + size) % BITS_PER_TYPE(u32);
+ source = from + (from_offset + size - offset) / BITS_PER_BYTE;
+ destination = to + (to_offset + size) / BITS_PER_BYTE;
+ while (size > MAX_BIG_FIELD_BITS) {
+ source -= sizeof(u32);
+ destination -= sizeof(u32);
+ size -= BITS_PER_TYPE(u32);
+ put_unaligned_le32(get_unaligned_le64(source) >> offset, destination);
+ }
+
+ /* Finish up by moving any remaining bits. */
+ if (size > 0) {
+ field = get_big_field(from, from_offset, size);
+ set_big_field(field, to, to_offset, size);
+ }
+}
+
+/*
+ * Move bits from one field to another. When the fields overlap, behave as if we first move all the
+ * bits from the source to a temporary value, and then move all the bits from the temporary value
+ * to the destination. The size and memory offsets are measured in bits.
+ */
+static void move_bits(const u8 *from, u64 from_offset, u8 *to, u64 to_offset, u32 size)
+{
+ u64 field;
+
+ /* A small move doesn't require special handling. */
+ if (size <= MAX_BIG_FIELD_BITS) {
+ if (size > 0) {
+ field = get_big_field(from, from_offset, size);
+ set_big_field(field, to, to_offset, size);
+ }
+
+ return;
+ }
+
+ if (from_offset > to_offset)
+ move_bits_down(from, from_offset, to, to_offset, size);
+ else
+ move_bits_up(from, from_offset, to, to_offset, size);
+}
+
+/*
+ * Pack delta lists from a mutable delta index into an immutable delta index page. A range of delta
+ * lists (starting with a specified list index) is copied from the mutable delta index into a
+ * memory page used in the immutable index. The number of lists copied onto the page is returned in
+ * list_count.
+ */
+int 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)
+{
+ const struct delta_zone *delta_zone;
+ struct delta_list *delta_lists;
+ u32 max_lists;
+ u32 n_lists = 0;
+ u32 offset;
+ u32 i;
+ int free_bits;
+ int bits;
+ struct delta_page_header *header;
+
+ delta_zone = &delta_index->delta_zones[0];
+ delta_lists = &delta_zone->delta_lists[first_list + 1];
+ max_lists = delta_index->list_count - first_list;
+
+ /*
+ * Compute how many lists will fit on the page. Subtract the size of the fixed header, one
+ * delta list offset, and the guard bytes from the page size to determine how much space is
+ * available for delta lists.
+ */
+ free_bits = memory_size * BITS_PER_BYTE;
+ free_bits -= get_immutable_header_offset(1);
+ free_bits -= GUARD_BITS;
+ if (free_bits < IMMUTABLE_HEADER_SIZE)
+ /* This page is too small to store any delta lists. */
+ return uds_log_error_strerror(UDS_OVERFLOW,
+ "Chapter Index Page of %zu bytes is too small",
+ memory_size);
+
+ while (n_lists < max_lists) {
+ /* Each list requires a delta list offset and the list data. */
+ bits = IMMUTABLE_HEADER_SIZE + delta_lists[n_lists].size;
+ if (bits > free_bits)
+ break;
+
+ n_lists++;
+ free_bits -= bits;
+ }
+
+ *list_count = n_lists;
+
+ header = (struct delta_page_header *) memory;
+ put_unaligned_le64(header_nonce, (u8 *) &header->nonce);
+ put_unaligned_le64(virtual_chapter_number, (u8 *) &header->virtual_chapter_number);
+ put_unaligned_le16(first_list, (u8 *) &header->first_list);
+ put_unaligned_le16(n_lists, (u8 *) &header->list_count);
+
+ /* Construct the delta list offset table. */
+ offset = get_immutable_header_offset(n_lists + 1);
+ set_immutable_start(memory, 0, offset);
+ for (i = 0; i < n_lists; i++) {
+ offset += delta_lists[i].size;
+ set_immutable_start(memory, i + 1, offset);
+ }
+
+ /* Copy the delta list data onto the memory page. */
+ for (i = 0; i < n_lists; i++)
+ move_bits(delta_zone->memory,
+ delta_lists[i].start,
+ memory,
+ get_immutable_start(memory, i),
+ delta_lists[i].size);
+
+ /* Set all the bits in the guard bytes. */
+ memset(memory + memory_size - POST_FIELD_GUARD_BYTES, ~0, POST_FIELD_GUARD_BYTES);
+ return UDS_SUCCESS;
+}
+
+/* Compute the new offsets of the delta lists. */
+static void compute_new_list_offsets(struct delta_zone *delta_zone,
+ u32 growing_index,
+ size_t growing_size,
+ size_t used_space)
+{
+ size_t spacing;
+ u32 i;
+ struct delta_list *delta_lists = delta_zone->delta_lists;
+ u32 tail_guard_index = delta_zone->list_count + 1;
+
+ spacing = (delta_zone->size - used_space) / delta_zone->list_count;
+ delta_zone->new_offsets[0] = 0;
+ for (i = 0; i <= delta_zone->list_count; i++) {
+ delta_zone->new_offsets[i + 1] =
+ (delta_zone->new_offsets[i] +
+ get_delta_list_byte_size(&delta_lists[i]) + spacing);
+ delta_zone->new_offsets[i] *= BITS_PER_BYTE;
+ delta_zone->new_offsets[i] += delta_lists[i].start % BITS_PER_BYTE;
+ if (i == 0)
+ delta_zone->new_offsets[i + 1] -= spacing / 2;
+ if (i + 1 == growing_index)
+ delta_zone->new_offsets[i + 1] += growing_size;
+ }
+
+ delta_zone->new_offsets[tail_guard_index] =
+ (delta_zone->size * BITS_PER_BYTE - delta_lists[tail_guard_index].size);
+}
+
+static void rebalance_lists(struct delta_zone *delta_zone)
+{
+ struct delta_list *delta_lists;
+ u32 i;
+ size_t used_space = 0;
+
+ /* Extend and balance memory to receive the delta lists */
+ delta_lists = delta_zone->delta_lists;
+ for (i = 0; i <= delta_zone->list_count + 1; i++)
+ used_space += get_delta_list_byte_size(&delta_lists[i]);
+
+ compute_new_list_offsets(delta_zone, 0, 0, used_space);
+ for (i = 1; i <= delta_zone->list_count + 1; i++)
+ delta_lists[i].start = delta_zone->new_offsets[i];
+}
+
+/* Start restoring a delta index from multiple input streams. */
+int uds_start_restoring_delta_index(struct delta_index *delta_index,
+ struct buffered_reader **buffered_readers,
+ unsigned int reader_count)
+{
+ int result;
+ unsigned int zone_count = reader_count;
+ u64 record_count = 0;
+ u64 collision_count = 0;
+ u32 first_list[MAX_ZONES];
+ u32 list_count[MAX_ZONES];
+ unsigned int z;
+ u32 list_next = 0;
+ const struct delta_zone *delta_zone;
+
+ /* Read and validate each header. */
+ for (z = 0; z < zone_count; z++) {
+ struct delta_index_header header;
+ u8 buffer[sizeof(struct delta_index_header)];
+ size_t offset = 0;
+
+ result = uds_read_from_buffered_reader(buffered_readers[z],
+ buffer,
+ sizeof(buffer));
+ if (result != UDS_SUCCESS)
+ return uds_log_warning_strerror(result,
+ "failed to read delta index header");
+
+ memcpy(&header.magic, buffer, MAGIC_SIZE);
+ offset += MAGIC_SIZE;
+ decode_u32_le(buffer, &offset, &header.zone_number);
+ decode_u32_le(buffer, &offset, &header.zone_count);
+ decode_u32_le(buffer, &offset, &header.first_list);
+ decode_u32_le(buffer, &offset, &header.list_count);
+ decode_u64_le(buffer, &offset, &header.record_count);
+ decode_u64_le(buffer, &offset, &header.collision_count);
+
+ result = ASSERT(offset == sizeof(struct delta_index_header),
+ "%zu bytes decoded of %zu expected",
+ offset,
+ sizeof(struct delta_index_header));
+ if (result != UDS_SUCCESS)
+ return uds_log_warning_strerror(result,
+ "failed to read delta index header");
+
+ if (memcmp(header.magic, DELTA_INDEX_MAGIC, MAGIC_SIZE) != 0)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "delta index file has bad magic number");
+
+ if (zone_count != header.zone_count)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "delta index files contain mismatched zone counts (%u,%u)",
+ zone_count,
+ header.zone_count);
+
+ if (header.zone_number != z)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "delta index zone %u found in slot %u",
+ header.zone_number,
+ z);
+
+ first_list[z] = header.first_list;
+ list_count[z] = header.list_count;
+ record_count += header.record_count;
+ collision_count += header.collision_count;
+
+ if (first_list[z] != list_next)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "delta index file for zone %u starts with list %u instead of list %u",
+ z,
+ first_list[z],
+ list_next);
+
+ list_next += list_count[z];
+ }
+
+ if (list_next != delta_index->list_count)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "delta index files contain %u delta lists instead of %u delta lists",
+ list_next,
+ delta_index->list_count);
+
+ if (collision_count > record_count)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "delta index files contain %llu collisions and %llu records",
+ (unsigned long long) collision_count,
+ (unsigned long long) record_count);
+
+ uds_reset_delta_index(delta_index);
+ delta_index->delta_zones[0].record_count = record_count;
+ delta_index->delta_zones[0].collision_count = collision_count;
+
+ /* Read the delta lists and distribute them to the proper zones. */
+ for (z = 0; z < zone_count; z++) {
+ u32 i;
+
+ delta_index->load_lists[z] = 0;
+ for (i = 0; i < list_count[z]; i++) {
+ u16 delta_list_size;
+ u32 list_number;
+ unsigned int zone_number;
+ u8 size_data[sizeof(u16)];
+
+ result = uds_read_from_buffered_reader(buffered_readers[z],
+ size_data,
+ sizeof(size_data));
+ if (result != UDS_SUCCESS)
+ return uds_log_warning_strerror(result,
+ "failed to read delta index size");
+
+ delta_list_size = get_unaligned_le16(size_data);
+ if (delta_list_size > 0)
+ delta_index->load_lists[z] += 1;
+
+ list_number = first_list[z] + i;
+ zone_number = list_number / delta_index->lists_per_zone;
+ delta_zone = &delta_index->delta_zones[zone_number];
+ list_number -= delta_zone->first_list;
+ delta_zone->delta_lists[list_number + 1].size = delta_list_size;
+ }
+ }
+
+ /* Prepare each zone to start receiving the delta list data. */
+ for (z = 0; z < delta_index->zone_count; z++)
+ rebalance_lists(&delta_index->delta_zones[z]);
+ return UDS_SUCCESS;
+}
+
+static int restore_delta_list_to_zone(struct delta_zone *delta_zone,
+ const struct delta_list_save_info *save_info,
+ const u8 *data)
+{
+ struct delta_list *delta_list;
+ u16 bit_count;
+ u16 byte_count;
+ u32 list_number = save_info->index - delta_zone->first_list;
+
+ if (list_number >= delta_zone->list_count)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "invalid delta list number %u not in range [%u,%u)",
+ save_info->index,
+ delta_zone->first_list,
+ delta_zone->first_list +
+ delta_zone->list_count);
+
+ delta_list = &delta_zone->delta_lists[list_number + 1];
+ if (delta_list->size == 0)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "unexpected delta list number %u",
+ save_info->index);
+
+ bit_count = delta_list->size + save_info->bit_offset;
+ byte_count = BITS_TO_BYTES(bit_count);
+ if (save_info->byte_count != byte_count)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "unexpected delta list size %u != %u",
+ save_info->byte_count,
+ byte_count);
+
+ move_bits(data,
+ save_info->bit_offset,
+ delta_zone->memory,
+ delta_list->start,
+ delta_list->size);
+ return UDS_SUCCESS;
+}
+
+static int restore_delta_list_data(struct delta_index *delta_index,
+ unsigned int load_zone,
+ struct buffered_reader *buffered_reader,
+ u8 *data)
+{
+ int result;
+ struct delta_list_save_info save_info;
+ u8 buffer[sizeof(struct delta_list_save_info)];
+ unsigned int new_zone;
+
+ result = uds_read_from_buffered_reader(buffered_reader, buffer, sizeof(buffer));
+ if (result != UDS_SUCCESS)
+ return uds_log_warning_strerror(result, "failed to read delta list data");
+
+ save_info = (struct delta_list_save_info) {
+ .tag = buffer[0],
+ .bit_offset = buffer[1],
+ .byte_count = get_unaligned_le16(&buffer[2]),
+ .index = get_unaligned_le32(&buffer[4]),
+ };
+
+ if ((save_info.bit_offset >= BITS_PER_BYTE) ||
+ (save_info.byte_count > DELTA_LIST_MAX_BYTE_COUNT))
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA, "corrupt delta list data");
+
+ /* Make sure the data is intended for this delta index. */
+ if (save_info.tag != delta_index->tag)
+ return UDS_CORRUPT_DATA;
+
+ if (save_info.index >= delta_index->list_count)
+ return uds_log_warning_strerror(UDS_CORRUPT_DATA,
+ "invalid delta list number %u of %u",
+ save_info.index,
+ delta_index->list_count);
+
+ result = uds_read_from_buffered_reader(buffered_reader, data, save_info.byte_count);
+ if (result != UDS_SUCCESS)
+ return uds_log_warning_strerror(result,
+ "failed to read delta list data");
+
+ delta_index->load_lists[load_zone] -= 1;
+ new_zone = save_info.index / delta_index->lists_per_zone;
+ return restore_delta_list_to_zone(&delta_index->delta_zones[new_zone], &save_info, data);
+}
+
+/* Restore delta lists from saved data. */
+int uds_finish_restoring_delta_index(struct delta_index *delta_index,
+ struct buffered_reader **buffered_readers,
+ unsigned int reader_count)
+{
+ int result;
+ int saved_result = UDS_SUCCESS;
+ unsigned int z;
+ u8 *data;
+
+ result = UDS_ALLOCATE(DELTA_LIST_MAX_BYTE_COUNT, u8, __func__, &data);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ for (z = 0; z < reader_count; z++) {
+ while (delta_index->load_lists[z] > 0) {
+ result = restore_delta_list_data(delta_index,
+ z,
+ buffered_readers[z],
+ data);
+ if (result != UDS_SUCCESS) {
+ saved_result = result;
+ break;
+ }
+ }
+ }
+
+ UDS_FREE(data);
+ return saved_result;
+}
+
+int uds_check_guard_delta_lists(struct buffered_reader **buffered_readers,
+ unsigned int reader_count)
+{
+ int result;
+ unsigned int z;
+ u8 buffer[sizeof(struct delta_list_save_info)];
+
+ for (z = 0; z < reader_count; z++) {
+ result = uds_read_from_buffered_reader(buffered_readers[z],
+ buffer,
+ sizeof(buffer));
+ if (result != UDS_SUCCESS)
+ return result;
+
+ if (buffer[0] != 'z')
+ return UDS_CORRUPT_DATA;
+ }
+
+ return UDS_SUCCESS;
+}
+
+static int flush_delta_list(struct delta_zone *zone, u32 flush_index)
+{
+ struct delta_list *delta_list;
+ u8 buffer[sizeof(struct delta_list_save_info)];
+ int result;
+
+ delta_list = &zone->delta_lists[flush_index + 1];
+
+ buffer[0] = zone->tag;
+ buffer[1] = delta_list->start % BITS_PER_BYTE;
+ put_unaligned_le16(get_delta_list_byte_size(delta_list), &buffer[2]);
+ put_unaligned_le32(zone->first_list + flush_index, &buffer[4]);
+
+ result = uds_write_to_buffered_writer(zone->buffered_writer, buffer, sizeof(buffer));
+ if (result != UDS_SUCCESS) {
+ uds_log_warning_strerror(result, "failed to write delta list memory");
+ return result;
+ }
+
+ result = uds_write_to_buffered_writer(zone->buffered_writer,
+ zone->memory + get_delta_list_byte_start(delta_list),
+ get_delta_list_byte_size(delta_list));
+ if (result != UDS_SUCCESS)
+ uds_log_warning_strerror(result, "failed to write delta list memory");
+
+ return result;
+}
+
+/* Start saving a delta index zone to a buffered output stream. */
+int uds_start_saving_delta_index(const struct delta_index *delta_index,
+ unsigned int zone_number,
+ struct buffered_writer *buffered_writer)
+{
+ int result;
+ u32 i;
+ struct delta_zone *delta_zone;
+ u8 buffer[sizeof(struct delta_index_header)];
+ size_t offset = 0;
+
+ delta_zone = &delta_index->delta_zones[zone_number];
+ memcpy(buffer, DELTA_INDEX_MAGIC, MAGIC_SIZE);
+ offset += MAGIC_SIZE;
+ encode_u32_le(buffer, &offset, zone_number);
+ encode_u32_le(buffer, &offset, delta_index->zone_count);
+ encode_u32_le(buffer, &offset, delta_zone->first_list);
+ encode_u32_le(buffer, &offset, delta_zone->list_count);
+ encode_u64_le(buffer, &offset, delta_zone->record_count);
+ encode_u64_le(buffer, &offset, delta_zone->collision_count);
+
+ result = ASSERT(offset == sizeof(struct delta_index_header),
+ "%zu bytes encoded of %zu expected",
+ offset,
+ sizeof(struct delta_index_header));
+ if (result != UDS_SUCCESS)
+ return result;
+
+ result = uds_write_to_buffered_writer(buffered_writer, buffer, offset);
+ if (result != UDS_SUCCESS)
+ return uds_log_warning_strerror(result, "failed to write delta index header");
+
+ for (i = 0; i < delta_zone->list_count; i++) {
+ u8 data[sizeof(u16)];
+ struct delta_list *delta_list;
+
+ delta_list = &delta_zone->delta_lists[i + 1];
+ put_unaligned_le16(delta_list->size, data);
+ result = uds_write_to_buffered_writer(buffered_writer, data, sizeof(data));
+ if (result != UDS_SUCCESS)
+ return uds_log_warning_strerror(result, "failed to write delta list size");
+ }
+
+ delta_zone->buffered_writer = buffered_writer;
+ return UDS_SUCCESS;
+}
+
+int uds_finish_saving_delta_index(const struct delta_index *delta_index, unsigned int zone_number)
+{
+ int result;
+ int first_error = UDS_SUCCESS;
+ u32 i;
+ struct delta_zone *delta_zone;
+ struct delta_list *delta_list;
+
+ delta_zone = &delta_index->delta_zones[zone_number];
+ for (i = 0; i < delta_zone->list_count; i++) {
+ delta_list = &delta_zone->delta_lists[i + 1];
+ if (delta_list->size > 0) {
+ result = flush_delta_list(delta_zone, i);
+ if ((result != UDS_SUCCESS) && (first_error == UDS_SUCCESS))
+ first_error = result;
+ }
+ }
+
+ delta_zone->buffered_writer = NULL;
+ return first_error;
+}
+
+int uds_write_guard_delta_list(struct buffered_writer *buffered_writer)
+{
+ int result;
+ u8 buffer[sizeof(struct delta_list_save_info)];
+
+ memset(buffer, 0, sizeof(struct delta_list_save_info));
+ buffer[0] = 'z';
+
+ result = uds_write_to_buffered_writer(buffered_writer, buffer, sizeof(buffer));
+ if (result != UDS_SUCCESS)
+ uds_log_warning_strerror(result, "failed to write guard delta list");
+
+ return UDS_SUCCESS;
+}
+
+size_t uds_compute_delta_index_save_bytes(u32 list_count, size_t memory_size)
+{
+ /* One zone will use at least as much memory as other zone counts. */
+ return (sizeof(struct delta_index_header) +
+ list_count * (sizeof(struct delta_list_save_info) + 1) +
+ get_zone_memory_size(1, memory_size));
+}
+
+static int assert_not_at_end(const struct delta_index_entry *delta_entry)
+{
+ int result = ASSERT(!delta_entry->at_end,
+ "operation is invalid because the list entry is at the end of the delta list");
+ if (result != UDS_SUCCESS)
+ result = UDS_BAD_STATE;
+
+ return result;
+}
+
+/*
+ * Prepare to search for an entry in the specified delta list.
+ *
+ * This is always the first function to be called when dealing with delta index entries. It is
+ * always followed by calls to uds_next_delta_index_entry() to iterate through a delta list. The
+ * fields of the delta_index_entry argument will be set up for iteration, but will not contain an
+ * entry from the list.
+ */
+int uds_start_delta_index_search(const struct delta_index *delta_index,
+ u32 list_number,
+ u32 key,
+ struct delta_index_entry *delta_entry)
+{
+ int result;
+ unsigned int zone_number;
+ struct delta_zone *delta_zone;
+ struct delta_list *delta_list;
+
+ result = ASSERT((list_number < delta_index->list_count),
+ "Delta list number (%u) is out of range (%u)",
+ list_number,
+ delta_index->list_count);
+ if (result != UDS_SUCCESS)
+ return UDS_CORRUPT_DATA;
+
+ zone_number = list_number / delta_index->lists_per_zone;
+ delta_zone = &delta_index->delta_zones[zone_number];
+ list_number -= delta_zone->first_list;
+ result = ASSERT((list_number < delta_zone->list_count),
+ "Delta list number (%u) is out of range (%u) for zone (%u)",
+ list_number,
+ delta_zone->list_count,
+ zone_number);
+ if (result != UDS_SUCCESS)
+ return UDS_CORRUPT_DATA;
+
+ if (delta_index->mutable) {
+ delta_list = &delta_zone->delta_lists[list_number + 1];
+ } else {
+ u32 end_offset;
+
+ /*
+ * Translate the immutable delta list header into a temporary
+ * full delta list header.
+ */
+ delta_list = &delta_entry->temp_delta_list;
+ delta_list->start = get_immutable_start(delta_zone->memory, list_number);
+ end_offset = get_immutable_start(delta_zone->memory, list_number + 1);
+ delta_list->size = end_offset - delta_list->start;
+ delta_list->save_key = 0;
+ delta_list->save_offset = 0;
+ }
+
+ if (key > delta_list->save_key) {
+ delta_entry->key = delta_list->save_key;
+ delta_entry->offset = delta_list->save_offset;
+ } else {
+ delta_entry->key = 0;
+ delta_entry->offset = 0;
+ if (key == 0)
+ /*
+ * This usually means we're about to walk the entire delta list, so get all
+ * of it into the CPU cache.
+ */
+ uds_prefetch_range(&delta_zone->memory[delta_list->start / BITS_PER_BYTE],
+ delta_list->size / BITS_PER_BYTE,
+ false);
+ }
+
+ delta_entry->at_end = false;
+ delta_entry->delta_zone = delta_zone;
+ delta_entry->delta_list = delta_list;
+ delta_entry->entry_bits = 0;
+ delta_entry->is_collision = false;
+ delta_entry->list_number = list_number;
+ delta_entry->list_overflow = false;
+ delta_entry->value_bits = delta_zone->value_bits;
+ return UDS_SUCCESS;
+}
+
+static inline u64 get_delta_entry_offset(const struct delta_index_entry *delta_entry)
+{
+ return delta_entry->delta_list->start + delta_entry->offset;
+}
+
+/*
+ * Decode a delta index entry delta value. The delta_index_entry basically describes the previous
+ * list entry, and has had its offset field changed to point to the subsequent entry. We decode the
+ * bit stream and update the delta_list_entry to describe the entry.
+ */
+static inline void decode_delta(struct delta_index_entry *delta_entry)
+{
+ int key_bits;
+ u32 delta;
+ const struct delta_zone *delta_zone = delta_entry->delta_zone;
+ const u8 *memory = delta_zone->memory;
+ u64 delta_offset = get_delta_entry_offset(delta_entry) + delta_entry->value_bits;
+ const u8 *addr = memory + delta_offset / BITS_PER_BYTE;
+ int offset = delta_offset % BITS_PER_BYTE;
+ u32 data = get_unaligned_le32(addr) >> offset;
+
+ addr += sizeof(u32);
+ key_bits = delta_zone->min_bits;
+ delta = data & ((1 << key_bits) - 1);
+ if (delta >= delta_zone->min_keys) {
+ data >>= key_bits;
+ if (data == 0) {
+ key_bits = sizeof(u32) * BITS_PER_BYTE - offset;
+ while ((data = get_unaligned_le32(addr)) == 0) {
+ addr += sizeof(u32);
+ key_bits += sizeof(u32) * BITS_PER_BYTE;
+ }
+ }
+ key_bits += ffs(data);
+ delta += ((key_bits - delta_zone->min_bits - 1) * delta_zone->incr_keys);
+ }
+ delta_entry->delta = delta;
+ delta_entry->key += delta;
+
+ /* Check for a collision, a delta of zero after the start. */
+ if (unlikely((delta == 0) && (delta_entry->offset > 0))) {
+ delta_entry->is_collision = true;
+ delta_entry->entry_bits = delta_entry->value_bits + key_bits + COLLISION_BITS;
+ } else {
+ delta_entry->is_collision = false;
+ delta_entry->entry_bits = delta_entry->value_bits + key_bits;
+ }
+}
+
+noinline int uds_next_delta_index_entry(struct delta_index_entry *delta_entry)
+{
+ int result;
+ const struct delta_list *delta_list;
+ u32 next_offset;
+ u16 size;
+
+ result = assert_not_at_end(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ delta_list = delta_entry->delta_list;
+ delta_entry->offset += delta_entry->entry_bits;
+ size = delta_list->size;
+ if (unlikely(delta_entry->offset >= size)) {
+ delta_entry->at_end = true;
+ delta_entry->delta = 0;
+ delta_entry->is_collision = false;
+ result = ASSERT((delta_entry->offset == size),
+ "next offset past end of delta list");
+ if (result != UDS_SUCCESS)
+ result = UDS_CORRUPT_DATA;
+
+ return result;
+ }
+
+ decode_delta(delta_entry);
+
+ next_offset = delta_entry->offset + delta_entry->entry_bits;
+ if (next_offset > size) {
+ /*
+ * This is not an assertion because uds_validate_chapter_index_page() wants to
+ * handle this error.
+ */
+ uds_log_warning("Decoded past the end of the delta list");
+ return UDS_CORRUPT_DATA;
+ }
+
+ return UDS_SUCCESS;
+}
+
+int uds_remember_delta_index_offset(const struct delta_index_entry *delta_entry)
+{
+ int result;
+ struct delta_list *delta_list = delta_entry->delta_list;
+
+ result = ASSERT(!delta_entry->is_collision, "entry is not a collision");
+ if (result != UDS_SUCCESS)
+ return result;
+
+ delta_list->save_key = delta_entry->key - delta_entry->delta;
+ delta_list->save_offset = delta_entry->offset;
+ return UDS_SUCCESS;
+}
+
+static void set_delta(struct delta_index_entry *delta_entry, u32 delta)
+{
+ const struct delta_zone *delta_zone = delta_entry->delta_zone;
+ u32 key_bits = (delta_zone->min_bits +
+ ((delta_zone->incr_keys -
+ delta_zone->min_keys + delta) /
+ delta_zone->incr_keys));
+
+ delta_entry->delta = delta;
+ delta_entry->entry_bits = delta_entry->value_bits + key_bits;
+}
+
+static void get_collision_name(const struct delta_index_entry *entry, u8 *name)
+{
+ u64 offset = get_delta_entry_offset(entry) + entry->entry_bits - COLLISION_BITS;
+ const u8 *addr = entry->delta_zone->memory + offset / BITS_PER_BYTE;
+ int size = COLLISION_BYTES;
+ int shift = offset % BITS_PER_BYTE;
+
+ while (--size >= 0)
+ *name++ = get_unaligned_le16(addr++) >> shift;
+}
+
+static void set_collision_name(const struct delta_index_entry *entry, const u8 *name)
+{
+ u64 offset = get_delta_entry_offset(entry) + entry->entry_bits - COLLISION_BITS;
+ u8 *addr = entry->delta_zone->memory + offset / BITS_PER_BYTE;
+ int size = COLLISION_BYTES;
+ int shift = offset % BITS_PER_BYTE;
+ u16 mask = ~((u16) 0xFF << shift);
+ u16 data;
+
+ while (--size >= 0) {
+ data = (get_unaligned_le16(addr) & mask) | (*name++ << shift);
+ put_unaligned_le16(data, addr++);
+ }
+}
+
+int 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 result;
+
+ result = uds_start_delta_index_search(delta_index, list_number, key, delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ do {
+ result = uds_next_delta_index_entry(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+ } while (!delta_entry->at_end && (key > delta_entry->key));
+
+ result = uds_remember_delta_index_offset(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ if (!delta_entry->at_end && (key == delta_entry->key)) {
+ struct delta_index_entry collision_entry = *delta_entry;
+
+ for (;;) {
+ u8 full_name[COLLISION_BYTES];
+
+ result = uds_next_delta_index_entry(&collision_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ if (collision_entry.at_end || !collision_entry.is_collision)
+ break;
+
+ get_collision_name(&collision_entry, full_name);
+ if (memcmp(full_name, name, COLLISION_BYTES) == 0) {
+ *delta_entry = collision_entry;
+ break;
+ }
+ }
+ }
+
+ return UDS_SUCCESS;
+}
+
+int uds_get_delta_entry_collision(const struct delta_index_entry *delta_entry, u8 *name)
+{
+ int result;
+
+ result = assert_not_at_end(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ result = ASSERT(delta_entry->is_collision,
+ "Cannot get full block name from a non-collision delta index entry");
+ if (result != UDS_SUCCESS)
+ return UDS_BAD_STATE;
+
+ get_collision_name(delta_entry, name);
+ return UDS_SUCCESS;
+}
+
+u32 uds_get_delta_entry_value(const struct delta_index_entry *delta_entry)
+{
+ return get_field(delta_entry->delta_zone->memory,
+ get_delta_entry_offset(delta_entry),
+ delta_entry->value_bits);
+}
+
+static int assert_mutable_entry(const struct delta_index_entry *delta_entry)
+{
+ int result = ASSERT((delta_entry->delta_list != &delta_entry->temp_delta_list),
+ "delta index is mutable");
+ if (result != UDS_SUCCESS)
+ result = UDS_BAD_STATE;
+
+ return result;
+}
+
+int uds_set_delta_entry_value(const struct delta_index_entry *delta_entry, u32 value)
+{
+ int result;
+ u32 value_mask = (1 << delta_entry->value_bits) - 1;
+
+ result = assert_mutable_entry(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ result = assert_not_at_end(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ result = ASSERT((value & value_mask) == value,
+ "Value (%u) being set in a delta index is too large (must fit in %u bits)",
+ value,
+ delta_entry->value_bits);
+ if (result != UDS_SUCCESS)
+ return UDS_INVALID_ARGUMENT;
+
+ set_field(value,
+ delta_entry->delta_zone->memory,
+ get_delta_entry_offset(delta_entry),
+ delta_entry->value_bits);
+ return UDS_SUCCESS;
+}
+
+/*
+ * Extend the memory used by the delta lists by adding growing_size bytes before the list indicated
+ * by growing_index, then rebalancing the lists in the new chunk.
+ */
+static int
+extend_delta_zone(struct delta_zone *delta_zone, u32 growing_index, size_t growing_size)
+{
+ ktime_t start_time;
+ ktime_t end_time;
+ struct delta_list *delta_lists;
+ u32 i;
+ size_t used_space;
+
+
+ /* Calculate the amount of space that is or will be in use. */
+ start_time = current_time_ns(CLOCK_MONOTONIC);
+ delta_lists = delta_zone->delta_lists;
+ used_space = growing_size;
+ for (i = 0; i <= delta_zone->list_count + 1; i++)
+ used_space += get_delta_list_byte_size(&delta_lists[i]);
+
+ if (delta_zone->size < used_space)
+ return UDS_OVERFLOW;
+
+ /* Compute the new offsets of the delta lists. */
+ compute_new_list_offsets(delta_zone, growing_index, growing_size, used_space);
+
+ /*
+ * When we rebalance the delta list, we will include the end guard list in the rebalancing.
+ * It contains the end guard data, which must be copied.
+ */
+ rebalance_delta_zone(delta_zone, 1, delta_zone->list_count + 1);
+ end_time = current_time_ns(CLOCK_MONOTONIC);
+ delta_zone->rebalance_count++;
+ delta_zone->rebalance_time += ktime_sub(end_time, start_time);
+ return UDS_SUCCESS;
+}
+
+static int insert_bits(struct delta_index_entry *delta_entry, u16 size)
+{
+ u64 free_before;
+ u64 free_after;
+ u64 source;
+ u64 destination;
+ u32 count;
+ bool before_flag;
+ u8 *memory;
+ struct delta_zone *delta_zone = delta_entry->delta_zone;
+ struct delta_list *delta_list = delta_entry->delta_list;
+ /* Compute bits in use before and after the inserted bits. */
+ u32 total_size = delta_list->size;
+ u32 before_size = delta_entry->offset;
+ u32 after_size = total_size - delta_entry->offset;
+
+ if (total_size + size > U16_MAX) {
+ delta_entry->list_overflow = true;
+ delta_zone->overflow_count++;
+ return UDS_OVERFLOW;
+ }
+
+ /* Compute bits available before and after the delta list. */
+ free_before = (delta_list[0].start - (delta_list[-1].start + delta_list[-1].size));
+ free_after = (delta_list[1].start - (delta_list[0].start + delta_list[0].size));
+
+ if ((size <= free_before) && (size <= free_after)) {
+ /*
+ * We have enough space to use either before or after the list. Select the smaller
+ * amount of data. If it is exactly the same, try to take from the larger amount of
+ * free space.
+ */
+ if (before_size < after_size)
+ before_flag = true;
+ else if (after_size < before_size)
+ before_flag = false;
+ else
+ before_flag = free_before > free_after;
+ } else if (size <= free_before) {
+ /* There is space before but not after. */
+ before_flag = true;
+ } else if (size <= free_after) {
+ /* There is space after but not before. */
+ before_flag = false;
+ } else {
+ /*
+ * Neither of the surrounding spaces is large enough for this request. Extend
+ * and/or rebalance the delta list memory choosing to move the least amount of
+ * data.
+ */
+ int result;
+ u32 growing_index = delta_entry->list_number + 1;
+
+ before_flag = before_size < after_size;
+ if (!before_flag)
+ growing_index++;
+ result = extend_delta_zone(delta_zone, growing_index, BITS_TO_BYTES(size));
+ if (result != UDS_SUCCESS)
+ return result;
+ }
+
+ delta_list->size += size;
+ if (before_flag) {
+ source = delta_list->start;
+ destination = source - size;
+ delta_list->start -= size;
+ count = before_size;
+ } else {
+ source = delta_list->start + delta_entry->offset;
+ destination = source + size;
+ count = after_size;
+ }
+
+ memory = delta_zone->memory;
+ move_bits(memory, source, memory, destination, count);
+ return UDS_SUCCESS;
+}
+
+static void encode_delta(const struct delta_index_entry *delta_entry)
+{
+ u32 temp;
+ u32 t1;
+ u32 t2;
+ u64 offset;
+ const struct delta_zone *delta_zone = delta_entry->delta_zone;
+ u8 *memory = delta_zone->memory;
+
+ offset = get_delta_entry_offset(delta_entry) + delta_entry->value_bits;
+ if (delta_entry->delta < delta_zone->min_keys) {
+ set_field(delta_entry->delta, memory, offset, delta_zone->min_bits);
+ return;
+ }
+
+ temp = delta_entry->delta - delta_zone->min_keys;
+ t1 = (temp % delta_zone->incr_keys) + delta_zone->min_keys;
+ t2 = temp / delta_zone->incr_keys;
+ set_field(t1, memory, offset, delta_zone->min_bits);
+ set_zero(memory, offset + delta_zone->min_bits, t2);
+ set_field(1, memory, offset + delta_zone->min_bits + t2, 1);
+}
+
+static void encode_entry(const struct delta_index_entry *delta_entry, u32 value, const u8 *name)
+{
+ u8 *memory = delta_entry->delta_zone->memory;
+ u64 offset = get_delta_entry_offset(delta_entry);
+
+ set_field(value, memory, offset, delta_entry->value_bits);
+ encode_delta(delta_entry);
+ if (name != NULL)
+ set_collision_name(delta_entry, name);
+}
+
+/*
+ * Create a new entry in the delta index. If the entry is a collision, the full 256 bit name must
+ * be provided.
+ */
+int uds_put_delta_index_entry(struct delta_index_entry *delta_entry,
+ u32 key,
+ u32 value,
+ const u8 *name)
+{
+ int result;
+ struct delta_zone *delta_zone;
+
+ result = assert_mutable_entry(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ if (delta_entry->is_collision)
+ /*
+ * The caller wants us to insert a collision entry onto a collision entry. This
+ * happens when we find a collision and attempt to add the name again to the index.
+ * This is normally a fatal error unless we are replaying a closed chapter while we
+ * are rebuilding a volume index.
+ */
+ return UDS_DUPLICATE_NAME;
+
+ if (delta_entry->offset < delta_entry->delta_list->save_offset) {
+ /*
+ * The saved entry offset is after the new entry and will no longer be valid, so
+ * replace it with the insertion point.
+ */
+ result = uds_remember_delta_index_offset(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+ }
+
+ if (name != NULL) {
+ /* Insert a collision entry which is placed after this entry. */
+ result = assert_not_at_end(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ result = ASSERT((key == delta_entry->key), "incorrect key for collision entry");
+ if (result != UDS_SUCCESS)
+ return result;
+
+ delta_entry->offset += delta_entry->entry_bits;
+ set_delta(delta_entry, 0);
+ delta_entry->is_collision = true;
+ delta_entry->entry_bits += COLLISION_BITS;
+ result = insert_bits(delta_entry, delta_entry->entry_bits);
+ } else if (delta_entry->at_end) {
+ /* Insert a new entry at the end of the delta list. */
+ result = ASSERT((key >= delta_entry->key), "key past end of list");
+ if (result != UDS_SUCCESS)
+ return result;
+
+ set_delta(delta_entry, key - delta_entry->key);
+ delta_entry->key = key;
+ delta_entry->at_end = false;
+ result = insert_bits(delta_entry, delta_entry->entry_bits);
+ } else {
+ u16 old_entry_size;
+ u16 additional_size;
+ struct delta_index_entry next_entry;
+ u32 next_value;
+
+ /*
+ * Insert a new entry which requires the delta in the following entry to be
+ * updated.
+ */
+ result = ASSERT((key < delta_entry->key), "key precedes following entry");
+ if (result != UDS_SUCCESS)
+ return result;
+
+ result = ASSERT((key >= delta_entry->key - delta_entry->delta),
+ "key effects following entry's delta");
+ if (result != UDS_SUCCESS)
+ return result;
+
+ old_entry_size = delta_entry->entry_bits;
+ next_entry = *delta_entry;
+ next_value = uds_get_delta_entry_value(&next_entry);
+ set_delta(delta_entry, key - (delta_entry->key - delta_entry->delta));
+ delta_entry->key = key;
+ set_delta(&next_entry, next_entry.key - key);
+ next_entry.offset += delta_entry->entry_bits;
+ /* The two new entries are always bigger than the single entry being replaced. */
+ additional_size = (delta_entry->entry_bits +
+ next_entry.entry_bits - old_entry_size);
+ result = insert_bits(delta_entry, additional_size);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ encode_entry(&next_entry, next_value, NULL);
+ }
+
+ if (result != UDS_SUCCESS)
+ return result;
+
+ encode_entry(delta_entry, value, name);
+ delta_zone = delta_entry->delta_zone;
+ delta_zone->record_count++;
+ delta_zone->collision_count += delta_entry->is_collision ? 1 : 0;
+ return UDS_SUCCESS;
+}
+
+static void delete_bits(const struct delta_index_entry *delta_entry, int size)
+{
+ u64 source;
+ u64 destination;
+ u32 count;
+ bool before_flag;
+ struct delta_list *delta_list = delta_entry->delta_list;
+ u8 *memory = delta_entry->delta_zone->memory;
+ /* Compute bits retained before and after the deleted bits. */
+ u32 total_size = delta_list->size;
+ u32 before_size = delta_entry->offset;
+ u32 after_size = total_size - delta_entry->offset - size;
+
+ /*
+ * Determine whether to add to the available space either before or after the delta list.
+ * We prefer to move the least amount of data. If it is exactly the same, try to add to the
+ * smaller amount of free space.
+ */
+ if (before_size < after_size) {
+ before_flag = true;
+ } else if (after_size < before_size) {
+ before_flag = false;
+ } else {
+ u64 free_before =
+ (delta_list[0].start - (delta_list[-1].start + delta_list[-1].size));
+ u64 free_after =
+ (delta_list[1].start - (delta_list[0].start + delta_list[0].size));
+
+ before_flag = (free_before < free_after);
+ }
+
+ delta_list->size -= size;
+ if (before_flag) {
+ source = delta_list->start;
+ destination = source + size;
+ delta_list->start += size;
+ count = before_size;
+ } else {
+ destination = delta_list->start + delta_entry->offset;
+ source = destination + size;
+ count = after_size;
+ }
+
+ move_bits(memory, source, memory, destination, count);
+}
+
+int uds_remove_delta_index_entry(struct delta_index_entry *delta_entry)
+{
+ int result;
+ struct delta_index_entry next_entry;
+ struct delta_zone *delta_zone;
+ struct delta_list *delta_list;
+
+ result = assert_mutable_entry(delta_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ next_entry = *delta_entry;
+ result = uds_next_delta_index_entry(&next_entry);
+ if (result != UDS_SUCCESS)
+ return result;
+
+ delta_zone = delta_entry->delta_zone;
+
+ if (delta_entry->is_collision) {
+ /* This is a collision entry, so just remove it. */
+ delete_bits(delta_entry, delta_entry->entry_bits);
+ next_entry.offset = delta_entry->offset;
+ delta_zone->collision_count -= 1;
+ } else if (next_entry.at_end) {
+ /* This entry is at the end of the list, so just remove it. */
+ delete_bits(delta_entry, delta_entry->entry_bits);
+ next_entry.key -= delta_entry->delta;
+ next_entry.offset = delta_entry->offset;
+ } else {
+ /* The delta in the next entry needs to be updated. */
+ u32 next_value = uds_get_delta_entry_value(&next_entry);
+ u16 old_size = delta_entry->entry_bits + next_entry.entry_bits;
+
+ if (next_entry.is_collision) {
+ next_entry.is_collision = false;
+ delta_zone->collision_count -= 1;
+ }
+
+ set_delta(&next_entry, delta_entry->delta + next_entry.delta);
+ next_entry.offset = delta_entry->offset;
+ /* The one new entry is always smaller than the two entries being replaced. */
+ delete_bits(delta_entry, old_size - next_entry.entry_bits);
+ encode_entry(&next_entry, next_value, NULL);
+ }
+
+ delta_zone->record_count--;
+ delta_zone->discard_count++;
+ *delta_entry = next_entry;
+
+ delta_list = delta_entry->delta_list;
+ if (delta_entry->offset < delta_list->save_offset) {
+ /* The saved entry offset is no longer valid. */
+ delta_list->save_key = 0;
+ delta_list->save_offset = 0;
+ }
+
+ return UDS_SUCCESS;
+}
+
+void uds_get_delta_index_stats(const struct delta_index *delta_index,
+ struct delta_index_stats *stats)
+{
+ unsigned int z;
+ const struct delta_zone *delta_zone;
+
+ memset(stats, 0, sizeof(struct delta_index_stats));
+ for (z = 0; z < delta_index->zone_count; z++) {
+ delta_zone = &delta_index->delta_zones[z];
+ stats->rebalance_time += delta_zone->rebalance_time;
+ stats->rebalance_count += delta_zone->rebalance_count;
+ stats->record_count += delta_zone->record_count;
+ stats->collision_count += delta_zone->collision_count;
+ stats->discard_count += delta_zone->discard_count;
+ stats->overflow_count += delta_zone->overflow_count;
+ stats->list_count += delta_zone->list_count;
+ }
+}
+
+size_t uds_compute_delta_index_size(u32 entry_count, u32 mean_delta, u32 payload_bits)
+{
+ u16 min_bits;
+ u32 incr_keys;
+ u32 min_keys;
+
+ compute_coding_constants(mean_delta, &min_bits, &min_keys, &incr_keys);
+ /* On average, each delta is encoded into about min_bits + 1.5 bits. */
+ return entry_count * (payload_bits + min_bits + 1) + entry_count / 2;
+}
+
+u32 uds_get_delta_index_page_count(u32 entry_count,
+ u32 list_count,
+ u32 mean_delta,
+ u32 payload_bits,
+ size_t bytes_per_page)
+{
+ unsigned int bits_per_delta_list;
+ unsigned int bits_per_page;
+ size_t bits_per_index;
+
+ /* Compute the expected number of bits needed for all the entries. */
+ bits_per_index = uds_compute_delta_index_size(entry_count, mean_delta, payload_bits);
+ bits_per_delta_list = bits_per_index / list_count;
+
+ /* Add in the immutable delta list headers. */
+ bits_per_index += list_count * IMMUTABLE_HEADER_SIZE;
+ /* Compute the number of usable bits on an immutable index page. */
+ bits_per_page = ((bytes_per_page - sizeof(struct delta_page_header)) * BITS_PER_BYTE);
+ /*
+ * Reduce the bits per page by one immutable delta list header and one delta list to
+ * account for internal fragmentation.
+ */
+ bits_per_page -= IMMUTABLE_HEADER_SIZE + bits_per_delta_list;
+ /* Now compute the number of pages needed. */
+ return DIV_ROUND_UP(bits_per_index, bits_per_page);
+}
+
+void uds_log_delta_index_entry(struct delta_index_entry *delta_entry)
+{
+ uds_log_ratelimit(uds_log_info,
+ "List 0x%X Key 0x%X Offset 0x%X%s%s List_size 0x%X%s",
+ delta_entry->list_number,
+ delta_entry->key,
+ delta_entry->offset,
+ delta_entry->at_end ? " end" : "",
+ delta_entry->is_collision ? " collision" : "",
+ delta_entry->delta_list->size,
+ delta_entry->list_overflow ? " overflow" : "");
+ delta_entry->list_overflow = false;
+}
new file mode 100644
@@ -0,0 +1,292 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright Red Hat
+ */
+
+#ifndef UDS_DELTA_INDEX_H
+#define UDS_DELTA_INDEX_H
+
+#include <linux/cache.h>
+
+#include "config.h"
+#include "io-factory.h"
+#include "numeric.h"
+#include "time-utils.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 DeltaPageHeader */
+ 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 a 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 */
new file mode 100644
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright Red Hat
+ */
+
+#ifndef UDS_HASH_UTILS_H
+#define UDS_HASH_UTILS_H
+
+#include "geometry.h"
+#include "numeric.h"
+#include "uds.h"
+
+/* Utilities for extracting portions of a request name for various uses. */
+
+/* How various portions of a record name are apportioned. */
+enum {
+ VOLUME_INDEX_BYTES_OFFSET = 0,
+ VOLUME_INDEX_BYTES_COUNT = 8,
+ CHAPTER_INDEX_BYTES_OFFSET = 8,
+ CHAPTER_INDEX_BYTES_COUNT = 6,
+ SAMPLE_BYTES_OFFSET = 14,
+ SAMPLE_BYTES_COUNT = 2,
+};
+
+static inline u64 uds_extract_chapter_index_bytes(const struct uds_record_name *name)
+{
+ const u8 *chapter_bits = &name->name[CHAPTER_INDEX_BYTES_OFFSET];
+ u64 bytes = (u64) get_unaligned_be16(chapter_bits) << 32;
+
+ bytes |= get_unaligned_be32(chapter_bits + 2);
+ return bytes;
+}
+
+static inline u64 uds_extract_volume_index_bytes(const struct uds_record_name *name)
+{
+ return get_unaligned_be64(&name->name[VOLUME_INDEX_BYTES_OFFSET]);
+}
+
+static inline u32 uds_extract_sampling_bytes(const struct uds_record_name *name)
+{
+ return get_unaligned_be16(&name->name[SAMPLE_BYTES_OFFSET]);
+}
+
+/* Compute the chapter delta list for a given name. */
+static inline u32
+uds_hash_to_chapter_delta_list(const struct uds_record_name *name, const struct geometry *geometry)
+{
+ return ((uds_extract_chapter_index_bytes(name) >> geometry->chapter_address_bits) &
+ ((1 << geometry->chapter_delta_list_bits) - 1));
+}
+
+/* Compute the chapter delta address for a given name. */
+static inline u32
+uds_hash_to_chapter_delta_address(const struct uds_record_name *name,
+ const struct geometry *geometry)
+{
+ return uds_extract_chapter_index_bytes(name) & ((1 << geometry->chapter_address_bits) - 1);
+}
+
+static inline unsigned int
+uds_name_to_hash_slot(const struct uds_record_name *name, unsigned int slot_count)
+{
+ return (unsigned int) (uds_extract_chapter_index_bytes(name) % slot_count);
+}
+
+#endif /* UDS_HASH_UTILS_H */
The delta index is a space and memory efficient alternative to a hashtable. Instead of storing the entire key for each entry, the entries are sorted by key and only the difference between adjacent keys (the delta) is stored. If the keys are evenly distributed, the size of the deltas follows an exponential distribution, and the deltas can use a Huffman code to take up even less space. This structure allows the index to use many fewer bytes per entry than a traditional hash table, but it is slightly more expensive to look up entries, because a request must read and sum every entry in a list of deltas in order to find a given record. The delta index reduces this lookup cost by splitting its key space into many sub-lists, each starting at a fixed key value, so that each individual list is short. Signed-off-by: J. corwin Coburn <corwin@redhat.com> --- drivers/md/dm-vdo/delta-index.c | 2018 +++++++++++++++++++++++++++++++ drivers/md/dm-vdo/delta-index.h | 292 +++++ drivers/md/dm-vdo/hash-utils.h | 66 + 3 files changed, 2376 insertions(+) create mode 100644 drivers/md/dm-vdo/delta-index.c create mode 100644 drivers/md/dm-vdo/delta-index.h create mode 100644 drivers/md/dm-vdo/hash-utils.h