drivers/md/dm-vdo/indexer/indexer.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Copyright 2023 Red Hat
   4  */
   5
   6 #ifndef INDEXER_H
   7 #define INDEXER_H
   8
   9 #include <linux/mutex.h>
  10 #include <linux/sched.h>
  11 #include <linux/types.h>
  12 #include <linux/wait.h>
  13
  14 #include "funnel-queue.h"
  15
  16 /*
  17  * UDS public API
  18  *
  19  * The Universal Deduplication System (UDS) is an efficient name-value store. When used for
  20  * deduplicating storage, the names are generally hashes of data blocks and the associated data is
  21  * where that block is located on the underlying storage medium. The stored names are expected to
  22  * be randomly distributed among the space of possible names. If this assumption is violated, the
  23  * UDS index will store fewer names than normal but will otherwise continue to work. The data
  24  * associated with each name can be any 16-byte value.
  25  *
  26  * A client must first create an index session to interact with an index. Once created, the session
  27  * can be shared among multiple threads or users. When a session is destroyed, it will also close
  28  * and save any associated index.
  29  *
  30  * To make a request, a client must allocate a uds_request structure and set the required fields
  31  * before launching it. UDS will invoke the provided callback to complete the request. After the
  32  * callback has been called, the uds_request structure can be freed or reused for a new request.
  33  * There are five types of requests:
  34  *
  35  * A UDS_UPDATE request will associate the provided name with the provided data. Any previous data
  36  * associated with that name will be discarded.
  37  *
  38  * A UDS_QUERY request will return the data associated with the provided name, if any. The entry
  39  * for the name will also be marked as most recent, as if the data had been updated.
  40  *
  41  * A UDS_POST request is a combination of UDS_QUERY and UDS_UPDATE. If there is already data
  42  * associated with the provided name, that data is returned. If there is no existing association,
  43  * the name is associated with the newly provided data. This request is equivalent to a UDS_QUERY
  44  * request followed by a UDS_UPDATE request if no data is found, but it is much more efficient.
  45  *
  46  * A UDS_QUERY_NO_UPDATE request will return the data associated with the provided name, but will
  47  * not change the recency of the entry for the name. This request is primarily useful for testing,
  48  * to determine whether an entry exists without changing the internal state of the index.
  49  *
  50  * A UDS_DELETE request removes any data associated with the provided name. This operation is
  51  * generally not necessary, because the index will automatically discard its oldest entries once it
  52  * becomes full.
  53  */
  54
  55 /* General UDS constants and structures */
  56
  57 enum uds_request_type {
  58         /* Create or update the mapping for a name, and make the name most recent. */
  59         UDS_UPDATE,
  60
  61         /* Return any mapped data for a name, and make the name most recent. */
  62         UDS_QUERY,
  63
  64         /*
  65          * Return any mapped data for a name, or map the provided data to the name if there is no
  66          * current data, and make the name most recent.
  67          */
  68         UDS_POST,
  69
  70         /* Return any mapped data for a name without updating its recency. */
  71         UDS_QUERY_NO_UPDATE,
  72
  73         /* Remove any mapping for a name. */
  74         UDS_DELETE,
  75
  76 };
  77
  78 enum uds_open_index_type {
  79         /* Create a new index. */
  80         UDS_CREATE,
  81
  82         /* Load an existing index and try to recover if necessary. */
  83         UDS_LOAD,
  84
  85         /* Load an existing index, but only if it was saved cleanly. */
  86         UDS_NO_REBUILD,
  87 };
  88
  89 enum {
  90         /* The record name size in bytes */
  91         UDS_RECORD_NAME_SIZE = 16,
  92         /* The maximum record data size in bytes */
  93         UDS_RECORD_DATA_SIZE = 16,
  94 };
  95
  96 /*
  97  * A type representing a UDS memory configuration which is either a positive integer number of
  98  * gigabytes or one of the six special constants for configurations smaller than one gigabyte.
  99  */
 100 typedef int uds_memory_config_size_t;
 101
 102 enum {
 103         /* The maximum configurable amount of memory */
 104         UDS_MEMORY_CONFIG_MAX = 1024,
 105         /* Flag indicating that the index has one less chapter than usual */
 106         UDS_MEMORY_CONFIG_REDUCED = 0x1000,
 107         UDS_MEMORY_CONFIG_REDUCED_MAX = 1024 + UDS_MEMORY_CONFIG_REDUCED,
 108         /* Special values indicating sizes less than 1 GB */
 109         UDS_MEMORY_CONFIG_256MB = -256,
 110         UDS_MEMORY_CONFIG_512MB = -512,
 111         UDS_MEMORY_CONFIG_768MB = -768,
 112         UDS_MEMORY_CONFIG_REDUCED_256MB = -1280,
 113         UDS_MEMORY_CONFIG_REDUCED_512MB = -1536,
 114         UDS_MEMORY_CONFIG_REDUCED_768MB = -1792,
 115 };
 116
 117 struct uds_record_name {
 118         unsigned char name[UDS_RECORD_NAME_SIZE];
 119 };
 120
 121 struct uds_record_data {
 122         unsigned char data[UDS_RECORD_DATA_SIZE];
 123 };
 124
 125 struct uds_volume_record {
 126         struct uds_record_name name;
 127         struct uds_record_data data;
 128 };
 129
 130 struct uds_parameters {
 131         /* The block_device used for storage */
 132         struct block_device *bdev;
 133         /* The maximum allowable size of the index on storage */
 134         size_t size;
 135         /* The offset where the index should start */
 136         off_t offset;
 137         /* The maximum memory allocation, in GB */
 138         uds_memory_config_size_t memory_size;
 139         /* Whether the index should include sparse chapters */
 140         bool sparse;
 141         /* A 64-bit nonce to validate the index */
 142         u64 nonce;
 143         /* The number of threads used to process index requests */
 144         unsigned int zone_count;
 145         /* The number of threads used to read volume pages */
 146         unsigned int read_threads;
 147 };
 148
 149 /*
 150  * These statistics capture characteristics of the current index, including resource usage and
 151  * requests processed since the index was opened.
 152  */
 153 struct uds_index_stats {
 154         /* The total number of records stored in the index */
 155         u64 entries_indexed;
 156         /* An estimate of the index's memory usage, in bytes */
 157         u64 memory_used;
 158         /* The number of collisions recorded in the volume index */
 159         u64 collisions;
 160         /* The number of entries discarded from the index since startup */
 161         u64 entries_discarded;
 162         /* The time at which these statistics were fetched */
 163         s64 current_time;
 164         /* The number of post calls that found an existing entry */
 165         u64 posts_found;
 166         /* The number of post calls that added an entry */
 167         u64 posts_not_found;
 168         /*
 169          * The number of post calls that found an existing entry that is current enough to only
 170          * exist in memory and not have been committed to disk yet
 171          */
 172         u64 in_memory_posts_found;
 173         /*
 174          * The number of post calls that found an existing entry in the dense portion of the index
 175          */
 176         u64 dense_posts_found;
 177         /*
 178          * The number of post calls that found an existing entry in the sparse portion of the index
 179          */
 180         u64 sparse_posts_found;
 181         /* The number of update calls that updated an existing entry */
 182         u64 updates_found;
 183         /* The number of update calls that added a new entry */
 184         u64 updates_not_found;
 185         /* The number of delete requests that deleted an existing entry */
 186         u64 deletions_found;
 187         /* The number of delete requests that did nothing */
 188         u64 deletions_not_found;
 189         /* The number of query calls that found existing entry */
 190         u64 queries_found;
 191         /* The number of query calls that did not find an entry */
 192         u64 queries_not_found;
 193         /* The total number of requests processed */
 194         u64 requests;
 195 };
 196
 197 enum uds_index_region {
 198         /* No location information has been determined */
 199         UDS_LOCATION_UNKNOWN = 0,
 200         /* The index page entry has been found */
 201         UDS_LOCATION_INDEX_PAGE_LOOKUP,
 202         /* The record page entry has been found */
 203         UDS_LOCATION_RECORD_PAGE_LOOKUP,
 204         /* The record is not in the index */
 205         UDS_LOCATION_UNAVAILABLE,
 206         /* The record was found in the open chapter */
 207         UDS_LOCATION_IN_OPEN_CHAPTER,
 208         /* The record was found in the dense part of the index */
 209         UDS_LOCATION_IN_DENSE,
 210         /* The record was found in the sparse part of the index */
 211         UDS_LOCATION_IN_SPARSE,
 212 } __packed;
 213
 214 /* Zone message requests are used to communicate between index zones. */
 215 enum uds_zone_message_type {
 216         /* A standard request with no message */
 217         UDS_MESSAGE_NONE = 0,
 218         /* Add a chapter to the sparse chapter index cache */
 219         UDS_MESSAGE_SPARSE_CACHE_BARRIER,
 220         /* Close a chapter to keep the zone from falling behind */
 221         UDS_MESSAGE_ANNOUNCE_CHAPTER_CLOSED,
 222 } __packed;
 223
 224 struct uds_zone_message {
 225         /* The type of message, determining how it will be processed */
 226         enum uds_zone_message_type type;
 227         /* The virtual chapter number to which the message applies */
 228         u64 virtual_chapter;
 229 };
 230
 231 struct uds_index_session;
 232 struct uds_index;
 233 struct uds_request;
 234
 235 /* Once this callback has been invoked, the uds_request structure can be reused or freed. */
 236 typedef void (*uds_request_callback_fn)(struct uds_request *request);
 237
 238 struct uds_request {
 239         /* These input fields must be set before launching a request. */
 240
 241         /* The name of the record to look up or create */
 242         struct uds_record_name record_name;
 243         /* New data to associate with the record name, if applicable */
 244         struct uds_record_data new_metadata;
 245         /* A callback to invoke when the request is complete */
 246         uds_request_callback_fn callback;
 247         /* The index session that will manage this request */
 248         struct uds_index_session *session;
 249         /* The type of operation to perform, as describe above */
 250         enum uds_request_type type;
 251
 252         /* These output fields are set when a request is complete. */
 253
 254         /* The existing data associated with the request name, if any */
 255         struct uds_record_data old_metadata;
 256         /* Either UDS_SUCCESS or an error code for the request */
 257         int status;
 258         /* True if the record name had an existing entry in the index */
 259         bool found;
 260
 261         /*
 262          * The remaining fields are used internally and should not be altered by clients. The index
 263          * relies on zone_number being the first field in this section.
 264          */
 265
 266         /* The number of the zone which will process this request*/
 267         unsigned int zone_number;
 268         /* A link for adding a request to a lock-free queue */
 269         struct funnel_queue_entry queue_link;
 270         /* A link for adding a request to a standard linked list */
 271         struct uds_request *next_request;
 272         /* A pointer to the index processing this request */
 273         struct uds_index *index;
 274         /* Control message for coordinating between zones */
 275         struct uds_zone_message zone_message;
 276         /* If true, process request immediately by waking the worker thread */
 277         bool unbatched;
 278         /* If true, continue this request before processing newer requests */
 279         bool requeued;
 280         /* The virtual chapter containing the record name, if known */
 281         u64 virtual_chapter;
 282         /* The region of the index containing the record name */
 283         enum uds_index_region location;
 284 };
 285
 286 /* A session is required for most index operations. */
 287 int __must_check uds_create_index_session(struct uds_index_session **session);
 288
 289 /* Destroying an index session also closes and saves the associated index. */
 290 int uds_destroy_index_session(struct uds_index_session *session);
 291
 292 /*
 293  * Create or open an index with an existing session. This operation fails if the index session is
 294  * suspended, or if there is already an open index.
 295  */
 296 int __must_check uds_open_index(enum uds_open_index_type open_type,
 297                                 const struct uds_parameters *parameters,
 298                                 struct uds_index_session *session);
 299
 300 /*
 301  * Wait until all callbacks for index operations are complete, and prevent new index operations
 302  * from starting. New index operations will fail with EBUSY until the session is resumed. Also
 303  * optionally saves the index.
 304  */
 305 int __must_check uds_suspend_index_session(struct uds_index_session *session, bool save);
 306
 307 /*
 308  * Allow new index operations for an index, whether it was suspended or not. If the index is
 309  * suspended and the supplied block device differs from the current backing store, the index will
 310  * start using the new backing store instead.
 311  */
 312 int __must_check uds_resume_index_session(struct uds_index_session *session,
 313                                           struct block_device *bdev);
 314
 315 /* Wait until all outstanding index operations are complete. */
 316 int __must_check uds_flush_index_session(struct uds_index_session *session);
 317
 318 /* Close an index. This operation fails if the index session is suspended. */
 319 int __must_check uds_close_index(struct uds_index_session *session);
 320
 321 /* Get index statistics since the last time the index was opened. */
 322 int __must_check uds_get_index_session_stats(struct uds_index_session *session,
 323                                              struct uds_index_stats *stats);
 324
 325 /* This function will fail if any required field of the request is not set. */
 326 int __must_check uds_launch_request(struct uds_request *request);
 327
 328 struct cond_var {
 329         wait_queue_head_t wait_queue;
 330 };
 331
 332 static inline void uds_init_cond(struct cond_var *cv)
 333 {
 334         init_waitqueue_head(&cv->wait_queue);
 335 }
 336
 337 static inline void uds_signal_cond(struct cond_var *cv)
 338 {
 339         wake_up(&cv->wait_queue);
 340 }
 341
 342 static inline void uds_broadcast_cond(struct cond_var *cv)
 343 {
 344         wake_up_all(&cv->wait_queue);
 345 }
 346
 347 void uds_wait_cond(struct cond_var *cv, struct mutex *mutex);
 348
 349 #endif /* INDEXER_H */