// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright 2023 Red Hat
*/
#include "geometry.h"
#include <linux/compiler.h>
#include <linux/log2.h>
#include "errors.h"
#include "logger.h"
#include "memory-alloc.h"
#include "permassert.h"
#include "delta-index.h"
#include "indexer.h"
/*
* An index volume is divided into a fixed number of fixed-size chapters, each consisting of a
* fixed number of fixed-size pages. The volume layout is defined by two constants and four
* parameters. The constants are that index records are 32 bytes long (16-byte block name plus
* 16-byte metadata) and that open chapter index hash slots are one byte long. The four parameters
* are the number of bytes in a page, the number of record pages in a chapter, the number of
* chapters in a volume, and the number of chapters that are sparse. From these parameters, we can
* derive the rest of the layout and other index properties.
*
* The index volume is sized by its maximum memory footprint. For a dense index, the persistent
* storage is about 10 times the size of the memory footprint. For a sparse index, the persistent
* storage is about 100 times the size of the memory footprint.
*
* For a small index with a memory footprint less than 1GB, there are three possible memory
* configurations: 0.25GB, 0.5GB and 0.75GB. The default geometry for each is 1024 index records
* per 32 KB page, 1024 chapters per volume, and either 64, 128, or 192 record pages per chapter
* (resulting in 6, 13, or 20 index pages per chapter) depending on the memory configuration. For
* the VDO default of a 0.25 GB index, this yields a deduplication window of 256 GB using about 2.5
* GB for the persistent storage and 256 MB of RAM.
*
* For a larger index with a memory footprint that is a multiple of 1 GB, the geometry is 1024
* index records per 32 KB page, 256 record pages per chapter, 26 index pages per chapter, and 1024
* chapters for every GB of memory footprint. For a 1 GB volume, this yields a deduplication window
* of 1 TB using about 9GB of persistent storage and 1 GB of RAM.
*
* The above numbers hold for volumes which have no sparse chapters. A sparse volume has 10 times
* as many chapters as the corresponding non-sparse volume, which provides 10 times the
* deduplication window while using 10 times as much persistent storage as the equivalent
* non-sparse volume with the same memory footprint.
*
* If the volume has been converted from a non-lvm format to an lvm volume, the number of chapters
* per volume will have been reduced by one by eliminating physical chapter 0, and the virtual
* chapter that formerly mapped to physical chapter 0 may be remapped to another physical chapter.
* This remapping is expressed by storing which virtual chapter was remapped, and which physical
* chapter it was moved to.
*/
int uds_make_index_geometry(size_t bytes_per_page, u32 record_pages_per_chapter,
u32 chapters_per_volume, u32 sparse_chapters_per_volume,
u64 remapped_virtual, u64 remapped_physical,
struct index_geometry **geometry_ptr)
{
int result;
struct index_geometry *geometry;
result = vdo_allocate(1, struct index_geometry, "geometry", &geometry);
if (result != VDO_SUCCESS)
return result;
geometry->bytes_per_page = bytes_per_page;
geometry->record_pages_per_chapter = record_pages_per_chapter;
geometry->chapters_per_volume = chapters_per_volume;
geometry->sparse_chapters_per_volume = sparse_chapters_per_volume;
geometry->dense_chapters_per_volume = chapters_per_volume - sparse_chapters_per_volume;
geometry->remapped_virtual = remapped_virtual;
geometry->remapped_physical = remapped_physical;
geometry->records_per_page = bytes_per_page / BYTES_PER_RECORD;
geometry->records_per_chapter = geometry->records_per_page * record_pages_per_chapter;
geometry->records_per_volume = (u64) geometry->records_per_chapter * chapters_per_volume;
geometry->chapter_mean_delta = 1 << DEFAULT_CHAPTER_MEAN_DELTA_BITS;
geometry->chapter_payload_bits = bits_per(record_pages_per_chapter - 1);
/*
* We want 1 delta list for every 64 records in the chapter.
* The "| 077" ensures that the chapter_delta_list_bits computation
* does not underflow.
*/
geometry->chapter_delta_list_bits =
bits_per((geometry->records_per_chapter - 1) | 077) - 6;
geometry->delta_lists_per_chapter = 1 << geometry->chapter_delta_list_bits;
/* We need enough address bits to achieve the desired mean delta. */
geometry->chapter_address_bits =
(DEFAULT_CHAPTER_MEAN_DELTA_BITS -
geometry->chapter_delta_list_bits +
bits_per(geometry->records_per_chapter - 1));
geometry->index_pages_per_chapter =
uds_get_delta_index_page_count(geometry->records_per_chapter,
geometry->delta_lists_per_chapter,
geometry->chapter_mean_delta,
geometry->chapter_payload_bits,
bytes_per_page);
geometry->pages_per_chapter = geometry->index_pages_per_chapter + record_pages_per_chapter;
geometry->pages_per_volume = geometry->pages_per_chapter * chapters_per_volume;
geometry->bytes_per_volume =
bytes_per_page * (geometry->pages_per_volume + HEADER_PAGES_PER_VOLUME);
*geometry_ptr = geometry;
return UDS_SUCCESS;
}
int uds_copy_index_geometry(struct index_geometry *source,
struct index_geometry **geometry_ptr)
{
return uds_make_index_geometry(source->bytes_per_page,
source->record_pages_per_chapter,
source->chapters_per_volume,
source->sparse_chapters_per_volume,
source->remapped_virtual, source->remapped_physical,
geometry_ptr);
}
void uds_free_index_geometry(struct index_geometry *geometry)
{
vdo_free(geometry);
}
u32 __must_check uds_map_to_physical_chapter(const struct index_geometry *geometry,
u64 virtual_chapter)
{
u64 delta;
if (!uds_is_reduced_index_geometry(geometry))
return virtual_chapter % geometry->chapters_per_volume;
if (likely(virtual_chapter > geometry->remapped_virtual)) {
delta = virtual_chapter - geometry->remapped_virtual;
if (likely(delta > geometry->remapped_physical))
return delta % geometry->chapters_per_volume;
else
return delta - 1;
}
if (virtual_chapter == geometry->remapped_virtual)
return geometry->remapped_physical;
delta = geometry->remapped_virtual - virtual_chapter;
if (delta < geometry->chapters_per_volume)
return geometry->chapters_per_volume - delta;
/* This chapter is so old the answer doesn't matter. */
return 0;
}
/* Check whether any sparse chapters are in use. */
bool uds_has_sparse_chapters(const struct index_geometry *geometry,
u64 oldest_virtual_chapter, u64 newest_virtual_chapter)
{
return uds_is_sparse_index_geometry(geometry) &&
((newest_virtual_chapter - oldest_virtual_chapter + 1) >
geometry->dense_chapters_per_volume);
}
bool uds_is_chapter_sparse(const struct index_geometry *geometry,
u64 oldest_virtual_chapter, u64 newest_virtual_chapter,
u64 virtual_chapter_number)
{
return uds_has_sparse_chapters(geometry, oldest_virtual_chapter,
newest_virtual_chapter) &&
((virtual_chapter_number + geometry->dense_chapters_per_volume) <=
newest_virtual_chapter);
}
/* Calculate how many chapters to expire after opening the newest chapter. */
u32 uds_chapters_to_expire(const struct index_geometry *geometry, u64 newest_chapter)
{
/* If the index isn't full yet, don't expire anything. */
if (newest_chapter < geometry->chapters_per_volume)
return 0;
/* If a chapter is out of order... */
if (geometry->remapped_physical > 0) {
u64 oldest_chapter = newest_chapter - geometry->chapters_per_volume;
/*
* ... expire an extra chapter when expiring the moved chapter to free physical
* space for the new chapter ...
*/
if (oldest_chapter == geometry->remapped_virtual)
return 2;
/*
* ... but don't expire anything when the new chapter will use the physical chapter
* freed by expiring the moved chapter.
*/
if (oldest_chapter == (geometry->remapped_virtual + geometry->remapped_physical))
return 0;
}
/* Normally, just expire one. */
return 1;
}
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