1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright 2023 Red Hat 4 */ 5 6 #include "geometry.h" 7 8 #include <linux/compiler.h> 9 #include <linux/log2.h> 10 11 #include "errors.h" 12 #include "logger.h" 13 #include "memory-alloc.h" 14 #include "permassert.h" 15 16 #include "delta-index.h" 17 #include "indexer.h" 18 19 /* 20 * An index volume is divided into a fixed number of fixed-size chapters, each consisting of a 21 * fixed number of fixed-size pages. The volume layout is defined by two constants and four 22 * parameters. The constants are that index records are 32 bytes long (16-byte block name plus 23 * 16-byte metadata) and that open chapter index hash slots are one byte long. The four parameters 24 * are the number of bytes in a page, the number of record pages in a chapter, the number of 25 * chapters in a volume, and the number of chapters that are sparse. From these parameters, we can 26 * derive the rest of the layout and other index properties. 27 * 28 * The index volume is sized by its maximum memory footprint. For a dense index, the persistent 29 * storage is about 10 times the size of the memory footprint. For a sparse index, the persistent 30 * storage is about 100 times the size of the memory footprint. 31 * 32 * For a small index with a memory footprint less than 1GB, there are three possible memory 33 * configurations: 0.25GB, 0.5GB and 0.75GB. The default geometry for each is 1024 index records 34 * per 32 KB page, 1024 chapters per volume, and either 64, 128, or 192 record pages per chapter 35 * (resulting in 6, 13, or 20 index pages per chapter) depending on the memory configuration. For 36 * the VDO default of a 0.25 GB index, this yields a deduplication window of 256 GB using about 2.5 37 * GB for the persistent storage and 256 MB of RAM. 38 * 39 * For a larger index with a memory footprint that is a multiple of 1 GB, the geometry is 1024 40 * index records per 32 KB page, 256 record pages per chapter, 26 index pages per chapter, and 1024 41 * chapters for every GB of memory footprint. For a 1 GB volume, this yields a deduplication window 42 * of 1 TB using about 9GB of persistent storage and 1 GB of RAM. 43 * 44 * The above numbers hold for volumes which have no sparse chapters. A sparse volume has 10 times 45 * as many chapters as the corresponding non-sparse volume, which provides 10 times the 46 * deduplication window while using 10 times as much persistent storage as the equivalent 47 * non-sparse volume with the same memory footprint. 48 * 49 * If the volume has been converted from a non-lvm format to an lvm volume, the number of chapters 50 * per volume will have been reduced by one by eliminating physical chapter 0, and the virtual 51 * chapter that formerly mapped to physical chapter 0 may be remapped to another physical chapter. 52 * This remapping is expressed by storing which virtual chapter was remapped, and which physical 53 * chapter it was moved to. 54 */ 55 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)56 int uds_make_index_geometry(size_t bytes_per_page, u32 record_pages_per_chapter, 57 u32 chapters_per_volume, u32 sparse_chapters_per_volume, 58 u64 remapped_virtual, u64 remapped_physical, 59 struct index_geometry **geometry_ptr) 60 { 61 int result; 62 struct index_geometry *geometry; 63 64 result = vdo_allocate(1, struct index_geometry, "geometry", &geometry); 65 if (result != VDO_SUCCESS) 66 return result; 67 68 geometry->bytes_per_page = bytes_per_page; 69 geometry->record_pages_per_chapter = record_pages_per_chapter; 70 geometry->chapters_per_volume = chapters_per_volume; 71 geometry->sparse_chapters_per_volume = sparse_chapters_per_volume; 72 geometry->dense_chapters_per_volume = chapters_per_volume - sparse_chapters_per_volume; 73 geometry->remapped_virtual = remapped_virtual; 74 geometry->remapped_physical = remapped_physical; 75 76 geometry->records_per_page = bytes_per_page / BYTES_PER_RECORD; 77 geometry->records_per_chapter = geometry->records_per_page * record_pages_per_chapter; 78 geometry->records_per_volume = (u64) geometry->records_per_chapter * chapters_per_volume; 79 80 geometry->chapter_mean_delta = 1 << DEFAULT_CHAPTER_MEAN_DELTA_BITS; 81 geometry->chapter_payload_bits = bits_per(record_pages_per_chapter - 1); 82 /* 83 * We want 1 delta list for every 64 records in the chapter. 84 * The "| 077" ensures that the chapter_delta_list_bits computation 85 * does not underflow. 86 */ 87 geometry->chapter_delta_list_bits = 88 bits_per((geometry->records_per_chapter - 1) | 077) - 6; 89 geometry->delta_lists_per_chapter = 1 << geometry->chapter_delta_list_bits; 90 /* We need enough address bits to achieve the desired mean delta. */ 91 geometry->chapter_address_bits = 92 (DEFAULT_CHAPTER_MEAN_DELTA_BITS - 93 geometry->chapter_delta_list_bits + 94 bits_per(geometry->records_per_chapter - 1)); 95 geometry->index_pages_per_chapter = 96 uds_get_delta_index_page_count(geometry->records_per_chapter, 97 geometry->delta_lists_per_chapter, 98 geometry->chapter_mean_delta, 99 geometry->chapter_payload_bits, 100 bytes_per_page); 101 102 geometry->pages_per_chapter = geometry->index_pages_per_chapter + record_pages_per_chapter; 103 geometry->pages_per_volume = geometry->pages_per_chapter * chapters_per_volume; 104 geometry->bytes_per_volume = 105 bytes_per_page * (geometry->pages_per_volume + HEADER_PAGES_PER_VOLUME); 106 107 *geometry_ptr = geometry; 108 return UDS_SUCCESS; 109 } 110 uds_copy_index_geometry(struct index_geometry * source,struct index_geometry ** geometry_ptr)111 int uds_copy_index_geometry(struct index_geometry *source, 112 struct index_geometry **geometry_ptr) 113 { 114 return uds_make_index_geometry(source->bytes_per_page, 115 source->record_pages_per_chapter, 116 source->chapters_per_volume, 117 source->sparse_chapters_per_volume, 118 source->remapped_virtual, source->remapped_physical, 119 geometry_ptr); 120 } 121 uds_free_index_geometry(struct index_geometry * geometry)122 void uds_free_index_geometry(struct index_geometry *geometry) 123 { 124 vdo_free(geometry); 125 } 126 uds_map_to_physical_chapter(const struct index_geometry * geometry,u64 virtual_chapter)127 u32 __must_check uds_map_to_physical_chapter(const struct index_geometry *geometry, 128 u64 virtual_chapter) 129 { 130 u64 delta; 131 132 if (!uds_is_reduced_index_geometry(geometry)) 133 return virtual_chapter % geometry->chapters_per_volume; 134 135 if (likely(virtual_chapter > geometry->remapped_virtual)) { 136 delta = virtual_chapter - geometry->remapped_virtual; 137 if (likely(delta > geometry->remapped_physical)) 138 return delta % geometry->chapters_per_volume; 139 else 140 return delta - 1; 141 } 142 143 if (virtual_chapter == geometry->remapped_virtual) 144 return geometry->remapped_physical; 145 146 delta = geometry->remapped_virtual - virtual_chapter; 147 if (delta < geometry->chapters_per_volume) 148 return geometry->chapters_per_volume - delta; 149 150 /* This chapter is so old the answer doesn't matter. */ 151 return 0; 152 } 153 154 /* Check whether any sparse chapters are in use. */ uds_has_sparse_chapters(const struct index_geometry * geometry,u64 oldest_virtual_chapter,u64 newest_virtual_chapter)155 bool uds_has_sparse_chapters(const struct index_geometry *geometry, 156 u64 oldest_virtual_chapter, u64 newest_virtual_chapter) 157 { 158 return uds_is_sparse_index_geometry(geometry) && 159 ((newest_virtual_chapter - oldest_virtual_chapter + 1) > 160 geometry->dense_chapters_per_volume); 161 } 162 uds_is_chapter_sparse(const struct index_geometry * geometry,u64 oldest_virtual_chapter,u64 newest_virtual_chapter,u64 virtual_chapter_number)163 bool uds_is_chapter_sparse(const struct index_geometry *geometry, 164 u64 oldest_virtual_chapter, u64 newest_virtual_chapter, 165 u64 virtual_chapter_number) 166 { 167 return uds_has_sparse_chapters(geometry, oldest_virtual_chapter, 168 newest_virtual_chapter) && 169 ((virtual_chapter_number + geometry->dense_chapters_per_volume) <= 170 newest_virtual_chapter); 171 } 172 173 /* Calculate how many chapters to expire after opening the newest chapter. */ uds_chapters_to_expire(const struct index_geometry * geometry,u64 newest_chapter)174 u32 uds_chapters_to_expire(const struct index_geometry *geometry, u64 newest_chapter) 175 { 176 /* If the index isn't full yet, don't expire anything. */ 177 if (newest_chapter < geometry->chapters_per_volume) 178 return 0; 179 180 /* If a chapter is out of order... */ 181 if (geometry->remapped_physical > 0) { 182 u64 oldest_chapter = newest_chapter - geometry->chapters_per_volume; 183 184 /* 185 * ... expire an extra chapter when expiring the moved chapter to free physical 186 * space for the new chapter ... 187 */ 188 if (oldest_chapter == geometry->remapped_virtual) 189 return 2; 190 191 /* 192 * ... but don't expire anything when the new chapter will use the physical chapter 193 * freed by expiring the moved chapter. 194 */ 195 if (oldest_chapter == (geometry->remapped_virtual + geometry->remapped_physical)) 196 return 0; 197 } 198 199 /* Normally, just expire one. */ 200 return 1; 201 } 202