include/linux/fscache-cache.h

   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/slow-work.h>
  24
  25 #define NR_MAXCACHES BITS_PER_LONG
  26
  27 struct fscache_cache;
  28 struct fscache_cache_ops;
  29 struct fscache_object;
  30 struct fscache_operation;
  31
  32 /*
  33  * cache tag definition
  34  */
  35 struct 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  */
  47 struct 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
  68 extern 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  */
  75 typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
  76 typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
  77
  78 struct fscache_operation {
  79         union {
  80                 struct work_struct fast_work;   /* record for fast ops */
  81                 struct slow_work slow_work;     /* record for (very) slow ops */
  82         };
  83         struct list_head        pend_link;      /* link in object->pending_ops */
  84         struct fscache_object   *object;        /* object to be operated upon */
  85
  86         unsigned long           flags;
  87 #define FSCACHE_OP_TYPE         0x000f  /* operation type */
  88 #define FSCACHE_OP_FAST         0x0001  /* - fast op, processor may not sleep for disk */
  89 #define FSCACHE_OP_SLOW         0x0002  /* - (very) slow op, processor may sleep for disk */
  90 #define FSCACHE_OP_MYTHREAD     0x0003  /* - processing is done be issuing thread, not pool */
  91 #define FSCACHE_OP_WAITING      4       /* cleared when op is woken */
  92 #define FSCACHE_OP_EXCLUSIVE    5       /* exclusive op, other ops must wait */
  93 #define FSCACHE_OP_DEAD         6       /* op is now dead */
  94
  95         atomic_t                usage;
  96         unsigned                debug_id;       /* debugging ID */
  97
  98         /* operation processor callback
  99          * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
 100          *   the op in a non-pool thread */
 101         fscache_operation_processor_t processor;
 102
 103         /* operation releaser */
 104         fscache_operation_release_t release;
 105 };
 106
 107 extern atomic_t fscache_op_debug_id;
 108 extern const struct slow_work_ops fscache_op_slow_work_ops;
 109
 110 extern void fscache_enqueue_operation(struct fscache_operation *);
 111 extern void fscache_put_operation(struct fscache_operation *);
 112
 113 /**
 114  * fscache_operation_init - Do basic initialisation of an operation
 115  * @op: The operation to initialise
 116  * @release: The release function to assign
 117  *
 118  * Do basic initialisation of an operation.  The caller must still set flags,
 119  * object, either fast_work or slow_work if necessary, and processor if needed.
 120  */
 121 static inline void fscache_operation_init(struct fscache_operation *op,
 122                                           fscache_operation_release_t release)
 123 {
 124         atomic_set(&op->usage, 1);
 125         op->debug_id = atomic_inc_return(&fscache_op_debug_id);
 126         op->release = release;
 127         INIT_LIST_HEAD(&op->pend_link);
 128 }
 129
 130 /**
 131  * fscache_operation_init_slow - Do additional initialisation of a slow op
 132  * @op: The operation to initialise
 133  * @processor: The processor function to assign
 134  *
 135  * Do additional initialisation of an operation as required for slow work.
 136  */
 137 static inline
 138 void fscache_operation_init_slow(struct fscache_operation *op,
 139                                  fscache_operation_processor_t processor)
 140 {
 141         op->processor = processor;
 142         slow_work_init(&op->slow_work, &fscache_op_slow_work_ops);
 143 }
 144
 145 /*
 146  * data read operation
 147  */
 148 struct fscache_retrieval {
 149         struct fscache_operation op;
 150         struct address_space    *mapping;       /* netfs pages */
 151         fscache_rw_complete_t   end_io_func;    /* function to call on I/O completion */
 152         void                    *context;       /* netfs read context (pinned) */
 153         struct list_head        to_do;          /* list of things to be done by the backend */
 154         unsigned long           start_time;     /* time at which retrieval started */
 155 };
 156
 157 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
 158                                              struct page *page,
 159                                              gfp_t gfp);
 160
 161 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
 162                                               struct list_head *pages,
 163                                               unsigned *nr_pages,
 164                                               gfp_t gfp);
 165
 166 /**
 167  * fscache_get_retrieval - Get an extra reference on a retrieval operation
 168  * @op: The retrieval operation to get a reference on
 169  *
 170  * Get an extra reference on a retrieval operation.
 171  */
 172 static inline
 173 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
 174 {
 175         atomic_inc(&op->op.usage);
 176         return op;
 177 }
 178
 179 /**
 180  * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
 181  * @op: The retrieval operation affected
 182  *
 183  * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
 184  */
 185 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
 186 {
 187         fscache_enqueue_operation(&op->op);
 188 }
 189
 190 /**
 191  * fscache_put_retrieval - Drop a reference to a retrieval operation
 192  * @op: The retrieval operation affected
 193  *
 194  * Drop a reference to a retrieval operation.
 195  */
 196 static inline void fscache_put_retrieval(struct fscache_retrieval *op)
 197 {
 198         fscache_put_operation(&op->op);
 199 }
 200
 201 /*
 202  * cached page storage work item
 203  * - used to do three things:
 204  *   - batch writes to the cache
 205  *   - do cache writes asynchronously
 206  *   - defer writes until cache object lookup completion
 207  */
 208 struct fscache_storage {
 209         struct fscache_operation op;
 210         pgoff_t                 store_limit;    /* don't write more than this */
 211 };
 212
 213 /*
 214  * cache operations
 215  */
 216 struct fscache_cache_ops {
 217         /* name of cache provider */
 218         const char *name;
 219
 220         /* allocate an object record for a cookie */
 221         struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
 222                                                struct fscache_cookie *cookie);
 223
 224         /* look up the object for a cookie */
 225         void (*lookup_object)(struct fscache_object *object);
 226
 227         /* finished looking up */
 228         void (*lookup_complete)(struct fscache_object *object);
 229
 230         /* increment the usage count on this object (may fail if unmounting) */
 231         struct fscache_object *(*grab_object)(struct fscache_object *object);
 232
 233         /* pin an object in the cache */
 234         int (*pin_object)(struct fscache_object *object);
 235
 236         /* unpin an object in the cache */
 237         void (*unpin_object)(struct fscache_object *object);
 238
 239         /* store the updated auxilliary data on an object */
 240         void (*update_object)(struct fscache_object *object);
 241
 242         /* discard the resources pinned by an object and effect retirement if
 243          * necessary */
 244         void (*drop_object)(struct fscache_object *object);
 245
 246         /* dispose of a reference to an object */
 247         void (*put_object)(struct fscache_object *object);
 248
 249         /* sync a cache */
 250         void (*sync_cache)(struct fscache_cache *cache);
 251
 252         /* notification that the attributes of a non-index object (such as
 253          * i_size) have changed */
 254         int (*attr_changed)(struct fscache_object *object);
 255
 256         /* reserve space for an object's data and associated metadata */
 257         int (*reserve_space)(struct fscache_object *object, loff_t i_size);
 258
 259         /* request a backing block for a page be read or allocated in the
 260          * cache */
 261         fscache_page_retrieval_func_t read_or_alloc_page;
 262
 263         /* request backing blocks for a list of pages be read or allocated in
 264          * the cache */
 265         fscache_pages_retrieval_func_t read_or_alloc_pages;
 266
 267         /* request a backing block for a page be allocated in the cache so that
 268          * it can be written directly */
 269         fscache_page_retrieval_func_t allocate_page;
 270
 271         /* request backing blocks for pages be allocated in the cache so that
 272          * they can be written directly */
 273         fscache_pages_retrieval_func_t allocate_pages;
 274
 275         /* write a page to its backing block in the cache */
 276         int (*write_page)(struct fscache_storage *op, struct page *page);
 277
 278         /* detach backing block from a page (optional)
 279          * - must release the cookie lock before returning
 280          * - may sleep
 281          */
 282         void (*uncache_page)(struct fscache_object *object,
 283                              struct page *page);
 284
 285         /* dissociate a cache from all the pages it was backing */
 286         void (*dissociate_pages)(struct fscache_cache *cache);
 287 };
 288
 289 /*
 290  * data file or index object cookie
 291  * - a file will only appear in one cache
 292  * - a request to cache a file may or may not be honoured, subject to
 293  *   constraints such as disk space
 294  * - indices are created on disk just-in-time
 295  */
 296 struct fscache_cookie {
 297         atomic_t                        usage;          /* number of users of this cookie */
 298         atomic_t                        n_children;     /* number of children of this cookie */
 299         spinlock_t                      lock;
 300         struct hlist_head               backing_objects; /* object(s) backing this file/index */
 301         const struct fscache_cookie_def *def;           /* definition */
 302         struct fscache_cookie           *parent;        /* parent of this entry */
 303         void                            *netfs_data;    /* back pointer to netfs */
 304         struct radix_tree_root          stores;         /* pages to be stored on this cookie */
 305 #define FSCACHE_COOKIE_PENDING_TAG      0               /* pages tag: pending write to cache */
 306
 307         unsigned long                   flags;
 308 #define FSCACHE_COOKIE_LOOKING_UP       0       /* T if non-index cookie being looked up still */
 309 #define FSCACHE_COOKIE_CREATING         1       /* T if non-index object being created still */
 310 #define FSCACHE_COOKIE_NO_DATA_YET      2       /* T if new object with no cached data yet */
 311 #define FSCACHE_COOKIE_PENDING_FILL     3       /* T if pending initial fill on object */
 312 #define FSCACHE_COOKIE_FILLING          4       /* T if filling object incrementally */
 313 #define FSCACHE_COOKIE_UNAVAILABLE      5       /* T if cookie is unavailable (error, etc) */
 314 };
 315
 316 extern struct fscache_cookie fscache_fsdef_index;
 317
 318 /*
 319  * on-disk cache file or index handle
 320  */
 321 struct fscache_object {
 322         enum fscache_object_state {
 323                 FSCACHE_OBJECT_INIT,            /* object in initial unbound state */
 324                 FSCACHE_OBJECT_LOOKING_UP,      /* looking up object */
 325                 FSCACHE_OBJECT_CREATING,        /* creating object */
 326
 327                 /* active states */
 328                 FSCACHE_OBJECT_AVAILABLE,       /* cleaning up object after creation */
 329                 FSCACHE_OBJECT_ACTIVE,          /* object is usable */
 330                 FSCACHE_OBJECT_UPDATING,        /* object is updating */
 331
 332                 /* terminal states */
 333                 FSCACHE_OBJECT_DYING,           /* object waiting for accessors to finish */
 334                 FSCACHE_OBJECT_LC_DYING,        /* object cleaning up after lookup/create */
 335                 FSCACHE_OBJECT_ABORT_INIT,      /* abort the init state */
 336                 FSCACHE_OBJECT_RELEASING,       /* releasing object */
 337                 FSCACHE_OBJECT_RECYCLING,       /* retiring object */
 338                 FSCACHE_OBJECT_WITHDRAWING,     /* withdrawing object */
 339                 FSCACHE_OBJECT_DEAD,            /* object is now dead */
 340         } state;
 341
 342         int                     debug_id;       /* debugging ID */
 343         int                     n_children;     /* number of child objects */
 344         int                     n_ops;          /* number of ops outstanding on object */
 345         int                     n_obj_ops;      /* number of object ops outstanding on object */
 346         int                     n_in_progress;  /* number of ops in progress */
 347         int                     n_exclusive;    /* number of exclusive ops queued */
 348         spinlock_t              lock;           /* state and operations lock */
 349
 350         unsigned long           lookup_jif;     /* time at which lookup started */
 351         unsigned long           event_mask;     /* events this object is interested in */
 352         unsigned long           events;         /* events to be processed by this object
 353                                                  * (order is important - using fls) */
 354 #define FSCACHE_OBJECT_EV_REQUEUE       0       /* T if object should be requeued */
 355 #define FSCACHE_OBJECT_EV_UPDATE        1       /* T if object should be updated */
 356 #define FSCACHE_OBJECT_EV_CLEARED       2       /* T if accessors all gone */
 357 #define FSCACHE_OBJECT_EV_ERROR         3       /* T if fatal error occurred during processing */
 358 #define FSCACHE_OBJECT_EV_RELEASE       4       /* T if netfs requested object release */
 359 #define FSCACHE_OBJECT_EV_RETIRE        5       /* T if netfs requested object retirement */
 360 #define FSCACHE_OBJECT_EV_WITHDRAW      6       /* T if cache requested object withdrawal */
 361
 362         unsigned long           flags;
 363 #define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
 364 #define FSCACHE_OBJECT_PENDING_WRITE    1       /* T if object has pending write */
 365 #define FSCACHE_OBJECT_WAITING          2       /* T if object is waiting on its parent */
 366
 367         struct list_head        cache_link;     /* link in cache->object_list */
 368         struct hlist_node       cookie_link;    /* link in cookie->backing_objects */
 369         struct fscache_cache    *cache;         /* cache that supplied this object */
 370         struct fscache_cookie   *cookie;        /* netfs's file/index object */
 371         struct fscache_object   *parent;        /* parent object */
 372         struct slow_work        work;           /* attention scheduling record */
 373         struct list_head        dependents;     /* FIFO of dependent objects */
 374         struct list_head        dep_link;       /* link in parent's dependents list */
 375         struct list_head        pending_ops;    /* unstarted operations on this object */
 376         pgoff_t                 store_limit;    /* current storage limit */
 377 };
 378
 379 extern const char *fscache_object_states[];
 380
 381 #define fscache_object_is_active(obj)                         \
 382         (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&  \
 383          (obj)->state >= FSCACHE_OBJECT_AVAILABLE &&          \
 384          (obj)->state < FSCACHE_OBJECT_DYING)
 385
 386 extern const struct slow_work_ops fscache_object_slow_work_ops;
 387
 388 /**
 389  * fscache_object_init - Initialise a cache object description
 390  * @object: Object description
 391  *
 392  * Initialise a cache object description to its basic values.
 393  *
 394  * See Documentation/filesystems/caching/backend-api.txt for a complete
 395  * description.
 396  */
 397 static inline
 398 void fscache_object_init(struct fscache_object *object,
 399                          struct fscache_cookie *cookie,
 400                          struct fscache_cache *cache)
 401 {
 402         atomic_inc(&cache->object_count);
 403
 404         object->state = FSCACHE_OBJECT_INIT;
 405         spin_lock_init(&object->lock);
 406         INIT_LIST_HEAD(&object->cache_link);
 407         INIT_HLIST_NODE(&object->cookie_link);
 408         vslow_work_init(&object->work, &fscache_object_slow_work_ops);
 409         INIT_LIST_HEAD(&object->dependents);
 410         INIT_LIST_HEAD(&object->dep_link);
 411         INIT_LIST_HEAD(&object->pending_ops);
 412         object->n_children = 0;
 413         object->n_ops = object->n_in_progress = object->n_exclusive = 0;
 414         object->events = object->event_mask = 0;
 415         object->flags = 0;
 416         object->store_limit = 0;
 417         object->cache = cache;
 418         object->cookie = cookie;
 419         object->parent = NULL;
 420 }
 421
 422 extern void fscache_object_lookup_negative(struct fscache_object *object);
 423 extern void fscache_obtained_object(struct fscache_object *object);
 424
 425 /**
 426  * fscache_object_destroyed - Note destruction of an object in a cache
 427  * @cache: The cache from which the object came
 428  *
 429  * Note the destruction and deallocation of an object record in a cache.
 430  */
 431 static inline void fscache_object_destroyed(struct fscache_cache *cache)
 432 {
 433         if (atomic_dec_and_test(&cache->object_count))
 434                 wake_up_all(&fscache_cache_cleared_wq);
 435 }
 436
 437 /**
 438  * fscache_object_lookup_error - Note an object encountered an error
 439  * @object: The object on which the error was encountered
 440  *
 441  * Note that an object encountered a fatal error (usually an I/O error) and
 442  * that it should be withdrawn as soon as possible.
 443  */
 444 static inline void fscache_object_lookup_error(struct fscache_object *object)
 445 {
 446         set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
 447 }
 448
 449 /**
 450  * fscache_set_store_limit - Set the maximum size to be stored in an object
 451  * @object: The object to set the maximum on
 452  * @i_size: The limit to set in bytes
 453  *
 454  * Set the maximum size an object is permitted to reach, implying the highest
 455  * byte that may be written.  Intended to be called by the attr_changed() op.
 456  *
 457  * See Documentation/filesystems/caching/backend-api.txt for a complete
 458  * description.
 459  */
 460 static inline
 461 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
 462 {
 463         object->store_limit = i_size >> PAGE_SHIFT;
 464         if (i_size & ~PAGE_MASK)
 465                 object->store_limit++;
 466 }
 467
 468 /**
 469  * fscache_end_io - End a retrieval operation on a page
 470  * @op: The FS-Cache operation covering the retrieval
 471  * @page: The page that was to be fetched
 472  * @error: The error code (0 if successful)
 473  *
 474  * Note the end of an operation to retrieve a page, as covered by a particular
 475  * operation record.
 476  */
 477 static inline void fscache_end_io(struct fscache_retrieval *op,
 478                                   struct page *page, int error)
 479 {
 480         op->end_io_func(page, op->context, error);
 481 }
 482
 483 /*
 484  * out-of-line cache backend functions
 485  */
 486 extern void fscache_init_cache(struct fscache_cache *cache,
 487                                const struct fscache_cache_ops *ops,
 488                                const char *idfmt,
 489                                ...) __attribute__ ((format (printf, 3, 4)));
 490
 491 extern int fscache_add_cache(struct fscache_cache *cache,
 492                              struct fscache_object *fsdef,
 493                              const char *tagname);
 494 extern void fscache_withdraw_cache(struct fscache_cache *cache);
 495
 496 extern void fscache_io_error(struct fscache_cache *cache);
 497
 498 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
 499                                       struct pagevec *pagevec);
 500
 501 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 502                                                const void *data,
 503                                                uint16_t datalen);
 504
 505 #endif /* _LINUX_FSCACHE_CACHE_H */