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/workqueue.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         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
 105 extern atomic_t fscache_op_debug_id;
 106 extern void fscache_op_work_func(struct work_struct *work);
 107
 108 extern void fscache_enqueue_operation(struct fscache_operation *);
 109 extern 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  */
 119 static 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  */
 134 struct 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
 143 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
 144                                              struct page *page,
 145                                              gfp_t gfp);
 146
 147 typedef 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  */
 158 static inline
 159 struct 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  */
 171 static 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  */
 182 static 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  */
 194 struct 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  */
 202 struct 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  */
 284 struct 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
 306 extern struct fscache_cookie fscache_fsdef_index;
 307
 308 /*
 309  * on-disk cache file or index handle
 310  */
 311 struct 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
 376 extern 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
 387 extern 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  */
 398 static inline
 399 void 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
 424 extern void fscache_object_lookup_negative(struct fscache_object *object);
 425 extern void fscache_obtained_object(struct fscache_object *object);
 426
 427 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 428 extern 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  */
 439 static 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  */
 452 static 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  */
 468 static inline
 469 void 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  */
 486 static 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  */
 495 extern void fscache_init_cache(struct fscache_cache *cache,
 496                                const struct fscache_cache_ops *ops,
 497                                const char *idfmt,
 498                                ...) __attribute__ ((format (printf, 3, 4)));
 499
 500 extern int fscache_add_cache(struct fscache_cache *cache,
 501                              struct fscache_object *fsdef,
 502                              const char *tagname);
 503 extern void fscache_withdraw_cache(struct fscache_cache *cache);
 504
 505 extern void fscache_io_error(struct fscache_cache *cache);
 506
 507 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
 508                                       struct pagevec *pagevec);
 509
 510 extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
 511
 512 extern 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 */