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
  78struct fscache_operation {
  79        struct work_struct      work;           /* record for async ops */
  80        struct list_head        pend_link;      /* link in object->pending_ops */
  81        struct fscache_object   *object;        /* object to be operated upon */
  82
  83        unsigned long           flags;
  84#define FSCACHE_OP_TYPE         0x000f  /* operation type */
  85#define FSCACHE_OP_ASYNC        0x0001  /* - async op, processor may sleep for disk */
  86#define FSCACHE_OP_MYTHREAD     0x0002  /* - processing is done be issuing thread, not pool */
  87#define FSCACHE_OP_WAITING      4       /* cleared when op is woken */
  88#define FSCACHE_OP_EXCLUSIVE    5       /* exclusive op, other ops must wait */
  89#define FSCACHE_OP_DEAD         6       /* op is now dead */
  90#define FSCACHE_OP_DEC_READ_CNT 7       /* decrement object->n_reads on destruction */
  91#define FSCACHE_OP_KEEP_FLAGS   0xc0    /* flags to keep when repurposing an op */
  92
  93        atomic_t                usage;
  94        unsigned                debug_id;       /* debugging ID */
  95
  96        /* operation processor callback
  97         * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
  98         *   the op in a non-pool thread */
  99        fscache_operation_processor_t processor;
 100
 101        /* operation releaser */
 102        fscache_operation_release_t release;
 103};
 104
 105extern atomic_t fscache_op_debug_id;
 106extern void fscache_op_work_func(struct work_struct *work);
 107
 108extern void fscache_enqueue_operation(struct fscache_operation *);
 109extern void fscache_put_operation(struct fscache_operation *);
 110
 111/**
 112 * fscache_operation_init - Do basic initialisation of an operation
 113 * @op: The operation to initialise
 114 * @release: The release function to assign
 115 *
 116 * Do basic initialisation of an operation.  The caller must still set flags,
 117 * object and processor if needed.
 118 */
 119static inline void fscache_operation_init(struct fscache_operation *op,
 120                                        fscache_operation_processor_t processor,
 121                                        fscache_operation_release_t release)
 122{
 123        INIT_WORK(&op->work, fscache_op_work_func);
 124        atomic_set(&op->usage, 1);
 125        op->debug_id = atomic_inc_return(&fscache_op_debug_id);
 126        op->processor = processor;
 127        op->release = release;
 128        INIT_LIST_HEAD(&op->pend_link);
 129}
 130
 131/*
 132 * data read operation
 133 */
 134struct fscache_retrieval {
 135        struct fscache_operation op;
 136        struct address_space    *mapping;       /* netfs pages */
 137        fscache_rw_complete_t   end_io_func;    /* function to call on I/O completion */
 138        void                    *context;       /* netfs read context (pinned) */
 139        struct list_head        to_do;          /* list of things to be done by the backend */
 140        unsigned long           start_time;     /* time at which retrieval started */
 141};
 142
 143typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
 144                                             struct page *page,
 145                                             gfp_t gfp);
 146
 147typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
 148                                              struct list_head *pages,
 149                                              unsigned *nr_pages,
 150                                              gfp_t gfp);
 151
 152/**
 153 * fscache_get_retrieval - Get an extra reference on a retrieval operation
 154 * @op: The retrieval operation to get a reference on
 155 *
 156 * Get an extra reference on a retrieval operation.
 157 */
 158static inline
 159struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
 160{
 161        atomic_inc(&op->op.usage);
 162        return op;
 163}
 164
 165/**
 166 * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
 167 * @op: The retrieval operation affected
 168 *
 169 * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
 170 */
 171static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
 172{
 173        fscache_enqueue_operation(&op->op);
 174}
 175
 176/**
 177 * fscache_put_retrieval - Drop a reference to a retrieval operation
 178 * @op: The retrieval operation affected
 179 *
 180 * Drop a reference to a retrieval operation.
 181 */
 182static inline void fscache_put_retrieval(struct fscache_retrieval *op)
 183{
 184        fscache_put_operation(&op->op);
 185}
 186
 187/*
 188 * cached page storage work item
 189 * - used to do three things:
 190 *   - batch writes to the cache
 191 *   - do cache writes asynchronously
 192 *   - defer writes until cache object lookup completion
 193 */
 194struct fscache_storage {
 195        struct fscache_operation op;
 196        pgoff_t                 store_limit;    /* don't write more than this */
 197};
 198
 199/*
 200 * cache operations
 201 */
 202struct fscache_cache_ops {
 203        /* name of cache provider */
 204        const char *name;
 205
 206        /* allocate an object record for a cookie */
 207        struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
 208                                               struct fscache_cookie *cookie);
 209
 210        /* look up the object for a cookie
 211         * - return -ETIMEDOUT to be requeued
 212         */
 213        int (*lookup_object)(struct fscache_object *object);
 214
 215        /* finished looking up */
 216        void (*lookup_complete)(struct fscache_object *object);
 217
 218        /* increment the usage count on this object (may fail if unmounting) */
 219        struct fscache_object *(*grab_object)(struct fscache_object *object);
 220
 221        /* pin an object in the cache */
 222        int (*pin_object)(struct fscache_object *object);
 223
 224        /* unpin an object in the cache */
 225        void (*unpin_object)(struct fscache_object *object);
 226
 227        /* store the updated auxiliary data on an object */
 228        void (*update_object)(struct fscache_object *object);
 229
 230        /* discard the resources pinned by an object and effect retirement if
 231         * necessary */
 232        void (*drop_object)(struct fscache_object *object);
 233
 234        /* dispose of a reference to an object */
 235        void (*put_object)(struct fscache_object *object);
 236
 237        /* sync a cache */
 238        void (*sync_cache)(struct fscache_cache *cache);
 239
 240        /* notification that the attributes of a non-index object (such as
 241         * i_size) have changed */
 242        int (*attr_changed)(struct fscache_object *object);
 243
 244        /* reserve space for an object's data and associated metadata */
 245        int (*reserve_space)(struct fscache_object *object, loff_t i_size);
 246
 247        /* request a backing block for a page be read or allocated in the
 248         * cache */
 249        fscache_page_retrieval_func_t read_or_alloc_page;
 250
 251        /* request backing blocks for a list of pages be read or allocated in
 252         * the cache */
 253        fscache_pages_retrieval_func_t read_or_alloc_pages;
 254
 255        /* request a backing block for a page be allocated in the cache so that
 256         * it can be written directly */
 257        fscache_page_retrieval_func_t allocate_page;
 258
 259        /* request backing blocks for pages be allocated in the cache so that
 260         * they can be written directly */
 261        fscache_pages_retrieval_func_t allocate_pages;
 262
 263        /* write a page to its backing block in the cache */
 264        int (*write_page)(struct fscache_storage *op, struct page *page);
 265
 266        /* detach backing block from a page (optional)
 267         * - must release the cookie lock before returning
 268         * - may sleep
 269         */
 270        void (*uncache_page)(struct fscache_object *object,
 271                             struct page *page);
 272
 273        /* dissociate a cache from all the pages it was backing */
 274        void (*dissociate_pages)(struct fscache_cache *cache);
 275};
 276
 277/*
 278 * data file or index object cookie
 279 * - a file will only appear in one cache
 280 * - a request to cache a file may or may not be honoured, subject to
 281 *   constraints such as disk space
 282 * - indices are created on disk just-in-time
 283 */
 284struct fscache_cookie {
 285        atomic_t                        usage;          /* number of users of this cookie */
 286        atomic_t                        n_children;     /* number of children of this cookie */
 287        spinlock_t                      lock;
 288        spinlock_t                      stores_lock;    /* lock on page store tree */
 289        struct hlist_head               backing_objects; /* object(s) backing this file/index */
 290        const struct fscache_cookie_def *def;           /* definition */
 291        struct fscache_cookie           *parent;        /* parent of this entry */
 292        void                            *netfs_data;    /* back pointer to netfs */
 293        struct radix_tree_root          stores;         /* pages to be stored on this cookie */
 294#define FSCACHE_COOKIE_PENDING_TAG      0               /* pages tag: pending write to cache */
 295#define FSCACHE_COOKIE_STORING_TAG      1               /* pages tag: writing to cache */
 296
 297        unsigned long                   flags;
 298#define FSCACHE_COOKIE_LOOKING_UP       0       /* T if non-index cookie being looked up still */
 299#define FSCACHE_COOKIE_CREATING         1       /* T if non-index object being created still */
 300#define FSCACHE_COOKIE_NO_DATA_YET      2       /* T if new object with no cached data yet */
 301#define FSCACHE_COOKIE_PENDING_FILL     3       /* T if pending initial fill on object */
 302#define FSCACHE_COOKIE_FILLING          4       /* T if filling object incrementally */
 303#define FSCACHE_COOKIE_UNAVAILABLE      5       /* T if cookie is unavailable (error, etc) */
 304};
 305
 306extern struct fscache_cookie fscache_fsdef_index;
 307
 308/*
 309 * on-disk cache file or index handle
 310 */
 311struct fscache_object {
 312        enum fscache_object_state {
 313                FSCACHE_OBJECT_INIT,            /* object in initial unbound state */
 314                FSCACHE_OBJECT_LOOKING_UP,      /* looking up object */
 315                FSCACHE_OBJECT_CREATING,        /* creating object */
 316
 317                /* active states */
 318                FSCACHE_OBJECT_AVAILABLE,       /* cleaning up object after creation */
 319                FSCACHE_OBJECT_ACTIVE,          /* object is usable */
 320                FSCACHE_OBJECT_UPDATING,        /* object is updating */
 321
 322                /* terminal states */
 323                FSCACHE_OBJECT_DYING,           /* object waiting for accessors to finish */
 324                FSCACHE_OBJECT_LC_DYING,        /* object cleaning up after lookup/create */
 325                FSCACHE_OBJECT_ABORT_INIT,      /* abort the init state */
 326                FSCACHE_OBJECT_RELEASING,       /* releasing object */
 327                FSCACHE_OBJECT_RECYCLING,       /* retiring object */
 328                FSCACHE_OBJECT_WITHDRAWING,     /* withdrawing object */
 329                FSCACHE_OBJECT_DEAD,            /* object is now dead */
 330                FSCACHE_OBJECT__NSTATES
 331        } state;
 332
 333        int                     debug_id;       /* debugging ID */
 334        int                     n_children;     /* number of child objects */
 335        int                     n_ops;          /* number of ops outstanding on object */
 336        int                     n_obj_ops;      /* number of object ops outstanding on object */
 337        int                     n_in_progress;  /* number of ops in progress */
 338        int                     n_exclusive;    /* number of exclusive ops queued */
 339        atomic_t                n_reads;        /* number of read ops in progress */
 340        spinlock_t              lock;           /* state and operations lock */
 341
 342        unsigned long           lookup_jif;     /* time at which lookup started */
 343        unsigned long           event_mask;     /* events this object is interested in */
 344        unsigned long           events;         /* events to be processed by this object
 345                                                 * (order is important - using fls) */
 346#define FSCACHE_OBJECT_EV_REQUEUE       0       /* T if object should be requeued */
 347#define FSCACHE_OBJECT_EV_UPDATE        1       /* T if object should be updated */
 348#define FSCACHE_OBJECT_EV_CLEARED       2       /* T if accessors all gone */
 349#define FSCACHE_OBJECT_EV_ERROR         3       /* T if fatal error occurred during processing */
 350#define FSCACHE_OBJECT_EV_RELEASE       4       /* T if netfs requested object release */
 351#define FSCACHE_OBJECT_EV_RETIRE        5       /* T if netfs requested object retirement */
 352#define FSCACHE_OBJECT_EV_WITHDRAW      6       /* T if cache requested object withdrawal */
 353#define FSCACHE_OBJECT_EVENTS_MASK      0x7f    /* mask of all events*/
 354
 355        unsigned long           flags;
 356#define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
 357#define FSCACHE_OBJECT_PENDING_WRITE    1       /* T if object has pending write */
 358#define FSCACHE_OBJECT_WAITING          2       /* T if object is waiting on its parent */
 359
 360        struct list_head        cache_link;     /* link in cache->object_list */
 361        struct hlist_node       cookie_link;    /* link in cookie->backing_objects */
 362        struct fscache_cache    *cache;         /* cache that supplied this object */
 363        struct fscache_cookie   *cookie;        /* netfs's file/index object */
 364        struct fscache_object   *parent;        /* parent object */
 365        struct work_struct      work;           /* attention scheduling record */
 366        struct list_head        dependents;     /* FIFO of dependent objects */
 367        struct list_head        dep_link;       /* link in parent's dependents list */
 368        struct list_head        pending_ops;    /* unstarted operations on this object */
 369#ifdef CONFIG_FSCACHE_OBJECT_LIST
 370        struct rb_node          objlist_link;   /* link in global object list */
 371#endif
 372        pgoff_t                 store_limit;    /* current storage limit */
 373        loff_t                  store_limit_l;  /* current storage limit */
 374};
 375
 376extern const char *fscache_object_states[];
 377
 378#define fscache_object_is_active(obj)                         \
 379        (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&  \
 380         (obj)->state >= FSCACHE_OBJECT_AVAILABLE &&          \
 381         (obj)->state < FSCACHE_OBJECT_DYING)
 382
 383#define fscache_object_is_dead(obj)                             \
 384        (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&     \
 385         (obj)->state >= FSCACHE_OBJECT_DYING)
 386
 387extern void fscache_object_work_func(struct work_struct *work);
 388
 389/**
 390 * fscache_object_init - Initialise a cache object description
 391 * @object: Object description
 392 *
 393 * Initialise a cache object description to its basic values.
 394 *
 395 * See Documentation/filesystems/caching/backend-api.txt for a complete
 396 * description.
 397 */
 398static inline
 399void fscache_object_init(struct fscache_object *object,
 400                         struct fscache_cookie *cookie,
 401                         struct fscache_cache *cache)
 402{
 403        atomic_inc(&cache->object_count);
 404
 405        object->state = FSCACHE_OBJECT_INIT;
 406        spin_lock_init(&object->lock);
 407        INIT_LIST_HEAD(&object->cache_link);
 408        INIT_HLIST_NODE(&object->cookie_link);
 409        INIT_WORK(&object->work, fscache_object_work_func);
 410        INIT_LIST_HEAD(&object->dependents);
 411        INIT_LIST_HEAD(&object->dep_link);
 412        INIT_LIST_HEAD(&object->pending_ops);
 413        object->n_children = 0;
 414        object->n_ops = object->n_in_progress = object->n_exclusive = 0;
 415        object->events = object->event_mask = 0;
 416        object->flags = 0;
 417        object->store_limit = 0;
 418        object->store_limit_l = 0;
 419        object->cache = cache;
 420        object->cookie = cookie;
 421        object->parent = NULL;
 422}
 423
 424extern void fscache_object_lookup_negative(struct fscache_object *object);
 425extern void fscache_obtained_object(struct fscache_object *object);
 426
 427#ifdef CONFIG_FSCACHE_OBJECT_LIST
 428extern void fscache_object_destroy(struct fscache_object *object);
 429#else
 430#define fscache_object_destroy(object) do {} while(0)
 431#endif
 432
 433/**
 434 * fscache_object_destroyed - Note destruction of an object in a cache
 435 * @cache: The cache from which the object came
 436 *
 437 * Note the destruction and deallocation of an object record in a cache.
 438 */
 439static inline void fscache_object_destroyed(struct fscache_cache *cache)
 440{
 441        if (atomic_dec_and_test(&cache->object_count))
 442                wake_up_all(&fscache_cache_cleared_wq);
 443}
 444
 445/**
 446 * fscache_object_lookup_error - Note an object encountered an error
 447 * @object: The object on which the error was encountered
 448 *
 449 * Note that an object encountered a fatal error (usually an I/O error) and
 450 * that it should be withdrawn as soon as possible.
 451 */
 452static inline void fscache_object_lookup_error(struct fscache_object *object)
 453{
 454        set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
 455}
 456
 457/**
 458 * fscache_set_store_limit - Set the maximum size to be stored in an object
 459 * @object: The object to set the maximum on
 460 * @i_size: The limit to set in bytes
 461 *
 462 * Set the maximum size an object is permitted to reach, implying the highest
 463 * byte that may be written.  Intended to be called by the attr_changed() op.
 464 *
 465 * See Documentation/filesystems/caching/backend-api.txt for a complete
 466 * description.
 467 */
 468static inline
 469void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
 470{
 471        object->store_limit_l = i_size;
 472        object->store_limit = i_size >> PAGE_SHIFT;
 473        if (i_size & ~PAGE_MASK)
 474                object->store_limit++;
 475}
 476
 477/**
 478 * fscache_end_io - End a retrieval operation on a page
 479 * @op: The FS-Cache operation covering the retrieval
 480 * @page: The page that was to be fetched
 481 * @error: The error code (0 if successful)
 482 *
 483 * Note the end of an operation to retrieve a page, as covered by a particular
 484 * operation record.
 485 */
 486static inline void fscache_end_io(struct fscache_retrieval *op,
 487                                  struct page *page, int error)
 488{
 489        op->end_io_func(page, op->context, error);
 490}
 491
 492/*
 493 * out-of-line cache backend functions
 494 */
 495extern __printf(3, 4)
 496void fscache_init_cache(struct fscache_cache *cache,
 497                        const struct fscache_cache_ops *ops,
 498                        const char *idfmt, ...);
 499
 500extern int fscache_add_cache(struct fscache_cache *cache,
 501                             struct fscache_object *fsdef,
 502                             const char *tagname);
 503extern void fscache_withdraw_cache(struct fscache_cache *cache);
 504
 505extern void fscache_io_error(struct fscache_cache *cache);
 506
 507extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
 508                                      struct pagevec *pagevec);
 509
 510extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
 511
 512extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 513                                               const void *data,
 514                                               uint16_t datalen);
 515
 516#endif /* _LINUX_FSCACHE_CACHE_H */
 517
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