linux/include/linux/fscache-cache.h
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   1/* General filesystem caching backing cache interface
   2 *
   3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the License, or (at your option) any later version.
  10 *
  11 * NOTE!!! See:
  12 *
  13 *      Documentation/filesystems/caching/backend-api.txt
  14 *
  15 * for a description of the cache backend interface declared here.
  16 */
  17
  18#ifndef _LINUX_FSCACHE_CACHE_H
  19#define _LINUX_FSCACHE_CACHE_H
  20
  21#include <linux/fscache.h>
  22#include <linux/sched.h>
  23#include <linux/workqueue.h>
  24
  25#define NR_MAXCACHES BITS_PER_LONG
  26
  27struct fscache_cache;
  28struct fscache_cache_ops;
  29struct fscache_object;
  30struct fscache_operation;
  31
  32/*
  33 * cache tag definition
  34 */
  35struct fscache_cache_tag {
  36        struct list_head        link;
  37        struct fscache_cache    *cache;         /* cache referred to by this tag */
  38        unsigned long           flags;
  39#define FSCACHE_TAG_RESERVED    0               /* T if tag is reserved for a cache */
  40        atomic_t                usage;
  41        char                    name[0];        /* tag name */
  42};
  43
  44/*
  45 * cache definition
  46 */
  47struct fscache_cache {
  48        const struct fscache_cache_ops *ops;
  49        struct fscache_cache_tag *tag;          /* tag representing this cache */
  50        struct kobject          *kobj;          /* system representation of this cache */
  51        struct list_head        link;           /* link in list of caches */
  52        size_t                  max_index_size; /* maximum size of index data */
  53        char                    identifier[36]; /* cache label */
  54
  55        /* node management */
  56        struct work_struct      op_gc;          /* operation garbage collector */
  57        struct list_head        object_list;    /* list of data/index objects */
  58        struct list_head        op_gc_list;     /* list of ops to be deleted */
  59        spinlock_t              object_list_lock;
  60        spinlock_t              op_gc_list_lock;
  61        atomic_t                object_count;   /* no. of live objects in this cache */
  62        struct fscache_object   *fsdef;         /* object for the fsdef index */
  63        unsigned long           flags;
  64#define FSCACHE_IOERROR         0       /* cache stopped on I/O error */
  65#define FSCACHE_CACHE_WITHDRAWN 1       /* cache has been withdrawn */
  66};
  67
  68extern wait_queue_head_t fscache_cache_cleared_wq;
  69
  70/*
  71 * operation to be applied to a cache object
  72 * - retrieval initiation operations are done in the context of the process
  73 *   that issued them, and not in an async thread pool
  74 */
  75typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
  76typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
  77
  78enum fscache_operation_state {
  79        FSCACHE_OP_ST_BLANK,            /* Op is not yet submitted */
  80        FSCACHE_OP_ST_INITIALISED,      /* Op is initialised */
  81        FSCACHE_OP_ST_PENDING,          /* Op is blocked from running */
  82        FSCACHE_OP_ST_IN_PROGRESS,      /* Op is in progress */
  83        FSCACHE_OP_ST_COMPLETE,         /* Op is complete */
  84        FSCACHE_OP_ST_CANCELLED,        /* Op has been cancelled */
  85        FSCACHE_OP_ST_DEAD              /* Op is now dead */
  86};
  87
  88struct fscache_operation {
  89        struct work_struct      work;           /* record for async ops */
  90        struct list_head        pend_link;      /* link in object->pending_ops */
  91        struct fscache_object   *object;        /* object to be operated upon */
  92
  93        unsigned long           flags;
  94#define FSCACHE_OP_TYPE         0x000f  /* operation type */
  95#define FSCACHE_OP_ASYNC        0x0001  /* - async op, processor may sleep for disk */
  96#define FSCACHE_OP_MYTHREAD     0x0002  /* - processing is done be issuing thread, not pool */
  97#define FSCACHE_OP_WAITING      4       /* cleared when op is woken */
  98#define FSCACHE_OP_EXCLUSIVE    5       /* exclusive op, other ops must wait */
  99#define FSCACHE_OP_DEC_READ_CNT 6       /* decrement object->n_reads on destruction */
 100#define FSCACHE_OP_KEEP_FLAGS   0x0070  /* flags to keep when repurposing an op */
 101
 102        enum fscache_operation_state state;
 103        atomic_t                usage;
 104        unsigned                debug_id;       /* debugging ID */
 105
 106        /* operation processor callback
 107         * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
 108         *   the op in a non-pool thread */
 109        fscache_operation_processor_t processor;
 110
 111        /* operation releaser */
 112        fscache_operation_release_t release;
 113};
 114
 115extern atomic_t fscache_op_debug_id;
 116extern void fscache_op_work_func(struct work_struct *work);
 117
 118extern void fscache_enqueue_operation(struct fscache_operation *);
 119extern void fscache_op_complete(struct fscache_operation *, bool);
 120extern void fscache_put_operation(struct fscache_operation *);
 121
 122/**
 123 * fscache_operation_init - Do basic initialisation of an operation
 124 * @op: The operation to initialise
 125 * @release: The release function to assign
 126 *
 127 * Do basic initialisation of an operation.  The caller must still set flags,
 128 * object and processor if needed.
 129 */
 130static inline void fscache_operation_init(struct fscache_operation *op,
 131                                        fscache_operation_processor_t processor,
 132                                        fscache_operation_release_t release)
 133{
 134        INIT_WORK(&op->work, fscache_op_work_func);
 135        atomic_set(&op->usage, 1);
 136        op->state = FSCACHE_OP_ST_INITIALISED;
 137        op->debug_id = atomic_inc_return(&fscache_op_debug_id);
 138        op->processor = processor;
 139        op->release = release;
 140        INIT_LIST_HEAD(&op->pend_link);
 141}
 142
 143/*
 144 * data read operation
 145 */
 146struct fscache_retrieval {
 147        struct fscache_operation op;
 148        struct address_space    *mapping;       /* netfs pages */
 149        fscache_rw_complete_t   end_io_func;    /* function to call on I/O completion */
 150        void                    *context;       /* netfs read context (pinned) */
 151        struct list_head        to_do;          /* list of things to be done by the backend */
 152        unsigned long           start_time;     /* time at which retrieval started */
 153        unsigned                n_pages;        /* number of pages to be retrieved */
 154};
 155
 156typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
 157                                             struct page *page,
 158                                             gfp_t gfp);
 159
 160typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
 161                                              struct list_head *pages,
 162                                              unsigned *nr_pages,
 163                                              gfp_t gfp);
 164
 165/**
 166 * fscache_get_retrieval - Get an extra reference on a retrieval operation
 167 * @op: The retrieval operation to get a reference on
 168 *
 169 * Get an extra reference on a retrieval operation.
 170 */
 171static inline
 172struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
 173{
 174        atomic_inc(&op->op.usage);
 175        return op;
 176}
 177
 178/**
 179 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
 180 * @op: The retrieval operation affected
 181 *
 182 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
 183 */
 184static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
 185{
 186        fscache_enqueue_operation(&op->op);
 187}
 188
 189/**
 190 * fscache_retrieval_complete - Record (partial) completion of a retrieval
 191 * @op: The retrieval operation affected
 192 * @n_pages: The number of pages to account for
 193 */
 194static inline void fscache_retrieval_complete(struct fscache_retrieval *op,
 195                                              int n_pages)
 196{
 197        op->n_pages -= n_pages;
 198        if (op->n_pages <= 0)
 199                fscache_op_complete(&op->op, true);
 200}
 201
 202/**
 203 * fscache_put_retrieval - Drop a reference to a retrieval operation
 204 * @op: The retrieval operation affected
 205 * @n_pages: The number of pages to account for
 206 *
 207 * Drop a reference to a retrieval operation.
 208 */
 209static inline void fscache_put_retrieval(struct fscache_retrieval *op)
 210{
 211        fscache_put_operation(&op->op);
 212}
 213
 214/*
 215 * cached page storage work item
 216 * - used to do three things:
 217 *   - batch writes to the cache
 218 *   - do cache writes asynchronously
 219 *   - defer writes until cache object lookup completion
 220 */
 221struct fscache_storage {
 222        struct fscache_operation op;
 223        pgoff_t                 store_limit;    /* don't write more than this */
 224};
 225
 226/*
 227 * cache operations
 228 */
 229struct fscache_cache_ops {
 230        /* name of cache provider */
 231        const char *name;
 232
 233        /* allocate an object record for a cookie */
 234        struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
 235                                               struct fscache_cookie *cookie);
 236
 237        /* look up the object for a cookie
 238         * - return -ETIMEDOUT to be requeued
 239         */
 240        int (*lookup_object)(struct fscache_object *object);
 241
 242        /* finished looking up */
 243        void (*lookup_complete)(struct fscache_object *object);
 244
 245        /* increment the usage count on this object (may fail if unmounting) */
 246        struct fscache_object *(*grab_object)(struct fscache_object *object);
 247
 248        /* pin an object in the cache */
 249        int (*pin_object)(struct fscache_object *object);
 250
 251        /* unpin an object in the cache */
 252        void (*unpin_object)(struct fscache_object *object);
 253
 254        /* store the updated auxiliary data on an object */
 255        void (*update_object)(struct fscache_object *object);
 256
 257        /* Invalidate an object */
 258        void (*invalidate_object)(struct fscache_operation *op);
 259
 260        /* discard the resources pinned by an object and effect retirement if
 261         * necessary */
 262        void (*drop_object)(struct fscache_object *object);
 263
 264        /* dispose of a reference to an object */
 265        void (*put_object)(struct fscache_object *object);
 266
 267        /* sync a cache */
 268        void (*sync_cache)(struct fscache_cache *cache);
 269
 270        /* notification that the attributes of a non-index object (such as
 271         * i_size) have changed */
 272        int (*attr_changed)(struct fscache_object *object);
 273
 274        /* reserve space for an object's data and associated metadata */
 275        int (*reserve_space)(struct fscache_object *object, loff_t i_size);
 276
 277        /* request a backing block for a page be read or allocated in the
 278         * cache */
 279        fscache_page_retrieval_func_t read_or_alloc_page;
 280
 281        /* request backing blocks for a list of pages be read or allocated in
 282         * the cache */
 283        fscache_pages_retrieval_func_t read_or_alloc_pages;
 284
 285        /* request a backing block for a page be allocated in the cache so that
 286         * it can be written directly */
 287        fscache_page_retrieval_func_t allocate_page;
 288
 289        /* request backing blocks for pages be allocated in the cache so that
 290         * they can be written directly */
 291        fscache_pages_retrieval_func_t allocate_pages;
 292
 293        /* write a page to its backing block in the cache */
 294        int (*write_page)(struct fscache_storage *op, struct page *page);
 295
 296        /* detach backing block from a page (optional)
 297         * - must release the cookie lock before returning
 298         * - may sleep
 299         */
 300        void (*uncache_page)(struct fscache_object *object,
 301                             struct page *page);
 302
 303        /* dissociate a cache from all the pages it was backing */
 304        void (*dissociate_pages)(struct fscache_cache *cache);
 305};
 306
 307/*
 308 * data file or index object cookie
 309 * - a file will only appear in one cache
 310 * - a request to cache a file may or may not be honoured, subject to
 311 *   constraints such as disk space
 312 * - indices are created on disk just-in-time
 313 */
 314struct fscache_cookie {
 315        atomic_t                        usage;          /* number of users of this cookie */
 316        atomic_t                        n_children;     /* number of children of this cookie */
 317        spinlock_t                      lock;
 318        spinlock_t                      stores_lock;    /* lock on page store tree */
 319        struct hlist_head               backing_objects; /* object(s) backing this file/index */
 320        const struct fscache_cookie_def *def;           /* definition */
 321        struct fscache_cookie           *parent;        /* parent of this entry */
 322        void                            *netfs_data;    /* back pointer to netfs */
 323        struct radix_tree_root          stores;         /* pages to be stored on this cookie */
 324#define FSCACHE_COOKIE_PENDING_TAG      0               /* pages tag: pending write to cache */
 325#define FSCACHE_COOKIE_STORING_TAG      1               /* pages tag: writing to cache */
 326
 327        unsigned long                   flags;
 328#define FSCACHE_COOKIE_LOOKING_UP       0       /* T if non-index cookie being looked up still */
 329#define FSCACHE_COOKIE_CREATING         1       /* T if non-index object being created still */
 330#define FSCACHE_COOKIE_NO_DATA_YET      2       /* T if new object with no cached data yet */
 331#define FSCACHE_COOKIE_PENDING_FILL     3       /* T if pending initial fill on object */
 332#define FSCACHE_COOKIE_FILLING          4       /* T if filling object incrementally */
 333#define FSCACHE_COOKIE_UNAVAILABLE      5       /* T if cookie is unavailable (error, etc) */
 334#define FSCACHE_COOKIE_WAITING_ON_READS 6       /* T if cookie is waiting on reads */
 335#define FSCACHE_COOKIE_INVALIDATING     7       /* T if cookie is being invalidated */
 336};
 337
 338extern struct fscache_cookie fscache_fsdef_index;
 339
 340/*
 341 * Event list for fscache_object::{event_mask,events}
 342 */
 343enum {
 344        FSCACHE_OBJECT_EV_REQUEUE,      /* T if object should be requeued */
 345        FSCACHE_OBJECT_EV_UPDATE,       /* T if object should be updated */
 346        FSCACHE_OBJECT_EV_INVALIDATE,   /* T if cache requested object invalidation */
 347        FSCACHE_OBJECT_EV_CLEARED,      /* T if accessors all gone */
 348        FSCACHE_OBJECT_EV_ERROR,        /* T if fatal error occurred during processing */
 349        FSCACHE_OBJECT_EV_RELEASE,      /* T if netfs requested object release */
 350        FSCACHE_OBJECT_EV_RETIRE,       /* T if netfs requested object retirement */
 351        FSCACHE_OBJECT_EV_WITHDRAW,     /* T if cache requested object withdrawal */
 352        NR_FSCACHE_OBJECT_EVENTS
 353};
 354
 355#define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
 356
 357/*
 358 * on-disk cache file or index handle
 359 */
 360struct fscache_object {
 361        enum fscache_object_state {
 362                FSCACHE_OBJECT_INIT,            /* object in initial unbound state */
 363                FSCACHE_OBJECT_LOOKING_UP,      /* looking up object */
 364                FSCACHE_OBJECT_CREATING,        /* creating object */
 365
 366                /* active states */
 367                FSCACHE_OBJECT_AVAILABLE,       /* cleaning up object after creation */
 368                FSCACHE_OBJECT_ACTIVE,          /* object is usable */
 369                FSCACHE_OBJECT_INVALIDATING,    /* object is invalidating */
 370                FSCACHE_OBJECT_UPDATING,        /* object is updating */
 371
 372                /* terminal states */
 373                FSCACHE_OBJECT_DYING,           /* object waiting for accessors to finish */
 374                FSCACHE_OBJECT_LC_DYING,        /* object cleaning up after lookup/create */
 375                FSCACHE_OBJECT_ABORT_INIT,      /* abort the init state */
 376                FSCACHE_OBJECT_RELEASING,       /* releasing object */
 377                FSCACHE_OBJECT_RECYCLING,       /* retiring object */
 378                FSCACHE_OBJECT_WITHDRAWING,     /* withdrawing object */
 379                FSCACHE_OBJECT_DEAD,            /* object is now dead */
 380                FSCACHE_OBJECT__NSTATES
 381        } state;
 382
 383        int                     debug_id;       /* debugging ID */
 384        int                     n_children;     /* number of child objects */
 385        int                     n_ops;          /* number of extant ops on object */
 386        int                     n_obj_ops;      /* number of object ops outstanding on object */
 387        int                     n_in_progress;  /* number of ops in progress */
 388        int                     n_exclusive;    /* number of exclusive ops queued or in progress */
 389        atomic_t                n_reads;        /* number of read ops in progress */
 390        spinlock_t              lock;           /* state and operations lock */
 391
 392        unsigned long           lookup_jif;     /* time at which lookup started */
 393        unsigned long           event_mask;     /* events this object is interested in */
 394        unsigned long           events;         /* events to be processed by this object
 395                                                 * (order is important - using fls) */
 396
 397        unsigned long           flags;
 398#define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
 399#define FSCACHE_OBJECT_PENDING_WRITE    1       /* T if object has pending write */
 400#define FSCACHE_OBJECT_WAITING          2       /* T if object is waiting on its parent */
 401
 402        struct list_head        cache_link;     /* link in cache->object_list */
 403        struct hlist_node       cookie_link;    /* link in cookie->backing_objects */
 404        struct fscache_cache    *cache;         /* cache that supplied this object */
 405        struct fscache_cookie   *cookie;        /* netfs's file/index object */
 406        struct fscache_object   *parent;        /* parent object */
 407        struct work_struct      work;           /* attention scheduling record */
 408        struct list_head        dependents;     /* FIFO of dependent objects */
 409        struct list_head        dep_link;       /* link in parent's dependents list */
 410        struct list_head        pending_ops;    /* unstarted operations on this object */
 411#ifdef CONFIG_FSCACHE_OBJECT_LIST
 412        struct rb_node          objlist_link;   /* link in global object list */
 413#endif
 414        pgoff_t                 store_limit;    /* current storage limit */
 415        loff_t                  store_limit_l;  /* current storage limit */
 416};
 417
 418extern const char *fscache_object_states[];
 419
 420#define fscache_object_is_active(obj)                         \
 421        (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&  \
 422         (obj)->state >= FSCACHE_OBJECT_AVAILABLE &&          \
 423         (obj)->state < FSCACHE_OBJECT_DYING)
 424
 425#define fscache_object_is_dead(obj)                             \
 426        (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&     \
 427         (obj)->state >= FSCACHE_OBJECT_DYING)
 428
 429extern void fscache_object_work_func(struct work_struct *work);
 430
 431/**
 432 * fscache_object_init - Initialise a cache object description
 433 * @object: Object description
 434 *
 435 * Initialise a cache object description to its basic values.
 436 *
 437 * See Documentation/filesystems/caching/backend-api.txt for a complete
 438 * description.
 439 */
 440static inline
 441void fscache_object_init(struct fscache_object *object,
 442                         struct fscache_cookie *cookie,
 443                         struct fscache_cache *cache)
 444{
 445        atomic_inc(&cache->object_count);
 446
 447        object->state = FSCACHE_OBJECT_INIT;
 448        spin_lock_init(&object->lock);
 449        INIT_LIST_HEAD(&object->cache_link);
 450        INIT_HLIST_NODE(&object->cookie_link);
 451        INIT_WORK(&object->work, fscache_object_work_func);
 452        INIT_LIST_HEAD(&object->dependents);
 453        INIT_LIST_HEAD(&object->dep_link);
 454        INIT_LIST_HEAD(&object->pending_ops);
 455        object->n_children = 0;
 456        object->n_ops = object->n_in_progress = object->n_exclusive = 0;
 457        object->events = object->event_mask = 0;
 458        object->flags = 0;
 459        object->store_limit = 0;
 460        object->store_limit_l = 0;
 461        object->cache = cache;
 462        object->cookie = cookie;
 463        object->parent = NULL;
 464}
 465
 466extern void fscache_object_lookup_negative(struct fscache_object *object);
 467extern void fscache_obtained_object(struct fscache_object *object);
 468
 469#ifdef CONFIG_FSCACHE_OBJECT_LIST
 470extern void fscache_object_destroy(struct fscache_object *object);
 471#else
 472#define fscache_object_destroy(object) do {} while(0)
 473#endif
 474
 475/**
 476 * fscache_object_destroyed - Note destruction of an object in a cache
 477 * @cache: The cache from which the object came
 478 *
 479 * Note the destruction and deallocation of an object record in a cache.
 480 */
 481static inline void fscache_object_destroyed(struct fscache_cache *cache)
 482{
 483        if (atomic_dec_and_test(&cache->object_count))
 484                wake_up_all(&fscache_cache_cleared_wq);
 485}
 486
 487/**
 488 * fscache_object_lookup_error - Note an object encountered an error
 489 * @object: The object on which the error was encountered
 490 *
 491 * Note that an object encountered a fatal error (usually an I/O error) and
 492 * that it should be withdrawn as soon as possible.
 493 */
 494static inline void fscache_object_lookup_error(struct fscache_object *object)
 495{
 496        set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
 497}
 498
 499/**
 500 * fscache_set_store_limit - Set the maximum size to be stored in an object
 501 * @object: The object to set the maximum on
 502 * @i_size: The limit to set in bytes
 503 *
 504 * Set the maximum size an object is permitted to reach, implying the highest
 505 * byte that may be written.  Intended to be called by the attr_changed() op.
 506 *
 507 * See Documentation/filesystems/caching/backend-api.txt for a complete
 508 * description.
 509 */
 510static inline
 511void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
 512{
 513        object->store_limit_l = i_size;
 514        object->store_limit = i_size >> PAGE_SHIFT;
 515        if (i_size & ~PAGE_MASK)
 516                object->store_limit++;
 517}
 518
 519/**
 520 * fscache_end_io - End a retrieval operation on a page
 521 * @op: The FS-Cache operation covering the retrieval
 522 * @page: The page that was to be fetched
 523 * @error: The error code (0 if successful)
 524 *
 525 * Note the end of an operation to retrieve a page, as covered by a particular
 526 * operation record.
 527 */
 528static inline void fscache_end_io(struct fscache_retrieval *op,
 529                                  struct page *page, int error)
 530{
 531        op->end_io_func(page, op->context, error);
 532}
 533
 534/*
 535 * out-of-line cache backend functions
 536 */
 537extern __printf(3, 4)
 538void fscache_init_cache(struct fscache_cache *cache,
 539                        const struct fscache_cache_ops *ops,
 540                        const char *idfmt, ...);
 541
 542extern int fscache_add_cache(struct fscache_cache *cache,
 543                             struct fscache_object *fsdef,
 544                             const char *tagname);
 545extern void fscache_withdraw_cache(struct fscache_cache *cache);
 546
 547extern void fscache_io_error(struct fscache_cache *cache);
 548
 549extern void fscache_mark_page_cached(struct fscache_retrieval *op,
 550                                     struct page *page);
 551
 552extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
 553                                      struct pagevec *pagevec);
 554
 555extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
 556
 557extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 558                                               const void *data,
 559                                               uint16_t datalen);
 560
 561#endif /* _LINUX_FSCACHE_CACHE_H */
 562
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