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 #define FSCACHE_OP_DEC_READ_CNT 7       /* decrement object->n_reads on destruction */
  95 #define FSCACHE_OP_KEEP_FLAGS   0xc0    /* flags to keep when repurposing an op */
  96
  97         atomic_t                usage;
  98         unsigned                debug_id;       /* debugging ID */
  99
 100         /* operation processor callback
 101          * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
 102          *   the op in a non-pool thread */
 103         fscache_operation_processor_t processor;
 104
 105         /* operation releaser */
 106         fscache_operation_release_t release;
 107
 108 #ifdef CONFIG_SLOW_WORK_DEBUG
 109         const char *name;               /* operation name */
 110         const char *state;              /* operation state */
 111 #define fscache_set_op_name(OP, N)      do { (OP)->name  = (N); } while(0)
 112 #define fscache_set_op_state(OP, S)     do { (OP)->state = (S); } while(0)
 113 #else
 114 #define fscache_set_op_name(OP, N)      do { } while(0)
 115 #define fscache_set_op_state(OP, S)     do { } while(0)
 116 #endif
 117 };
 118
 119 extern atomic_t fscache_op_debug_id;
 120 extern const struct slow_work_ops fscache_op_slow_work_ops;
 121
 122 extern void fscache_enqueue_operation(struct fscache_operation *);
 123 extern void fscache_put_operation(struct fscache_operation *);
 124
 125 /**
 126  * fscache_operation_init - Do basic initialisation of an operation
 127  * @op: The operation to initialise
 128  * @release: The release function to assign
 129  *
 130  * Do basic initialisation of an operation.  The caller must still set flags,
 131  * object, either fast_work or slow_work if necessary, and processor if needed.
 132  */
 133 static inline void fscache_operation_init(struct fscache_operation *op,
 134                                           fscache_operation_release_t release)
 135 {
 136         atomic_set(&op->usage, 1);
 137         op->debug_id = atomic_inc_return(&fscache_op_debug_id);
 138         op->release = release;
 139         INIT_LIST_HEAD(&op->pend_link);
 140         fscache_set_op_state(op, "Init");
 141 }
 142
 143 /**
 144  * fscache_operation_init_slow - Do additional initialisation of a slow op
 145  * @op: The operation to initialise
 146  * @processor: The processor function to assign
 147  *
 148  * Do additional initialisation of an operation as required for slow work.
 149  */
 150 static inline
 151 void fscache_operation_init_slow(struct fscache_operation *op,
 152                                  fscache_operation_processor_t processor)
 153 {
 154         op->processor = processor;
 155         slow_work_init(&op->slow_work, &fscache_op_slow_work_ops);
 156 }
 157
 158 /*
 159  * data read operation
 160  */
 161 struct fscache_retrieval {
 162         struct fscache_operation op;
 163         struct address_space    *mapping;       /* netfs pages */
 164         fscache_rw_complete_t   end_io_func;    /* function to call on I/O completion */
 165         void                    *context;       /* netfs read context (pinned) */
 166         struct list_head        to_do;          /* list of things to be done by the backend */
 167         unsigned long           start_time;     /* time at which retrieval started */
 168 };
 169
 170 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
 171                                              struct page *page,
 172                                              gfp_t gfp);
 173
 174 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
 175                                               struct list_head *pages,
 176                                               unsigned *nr_pages,
 177                                               gfp_t gfp);
 178
 179 /**
 180  * fscache_get_retrieval - Get an extra reference on a retrieval operation
 181  * @op: The retrieval operation to get a reference on
 182  *
 183  * Get an extra reference on a retrieval operation.
 184  */
 185 static inline
 186 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
 187 {
 188         atomic_inc(&op->op.usage);
 189         return op;
 190 }
 191
 192 /**
 193  * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
 194  * @op: The retrieval operation affected
 195  *
 196  * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
 197  */
 198 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
 199 {
 200         fscache_enqueue_operation(&op->op);
 201 }
 202
 203 /**
 204  * fscache_put_retrieval - Drop a reference to a retrieval operation
 205  * @op: The retrieval operation affected
 206  *
 207  * Drop a reference to a retrieval operation.
 208  */
 209 static 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  */
 221 struct 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  */
 229 struct 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 auxilliary data on an object */
 255         void (*update_object)(struct fscache_object *object);
 256
 257         /* discard the resources pinned by an object and effect retirement if
 258          * necessary */
 259         void (*drop_object)(struct fscache_object *object);
 260
 261         /* dispose of a reference to an object */
 262         void (*put_object)(struct fscache_object *object);
 263
 264         /* sync a cache */
 265         void (*sync_cache)(struct fscache_cache *cache);
 266
 267         /* notification that the attributes of a non-index object (such as
 268          * i_size) have changed */
 269         int (*attr_changed)(struct fscache_object *object);
 270
 271         /* reserve space for an object's data and associated metadata */
 272         int (*reserve_space)(struct fscache_object *object, loff_t i_size);
 273
 274         /* request a backing block for a page be read or allocated in the
 275          * cache */
 276         fscache_page_retrieval_func_t read_or_alloc_page;
 277
 278         /* request backing blocks for a list of pages be read or allocated in
 279          * the cache */
 280         fscache_pages_retrieval_func_t read_or_alloc_pages;
 281
 282         /* request a backing block for a page be allocated in the cache so that
 283          * it can be written directly */
 284         fscache_page_retrieval_func_t allocate_page;
 285
 286         /* request backing blocks for pages be allocated in the cache so that
 287          * they can be written directly */
 288         fscache_pages_retrieval_func_t allocate_pages;
 289
 290         /* write a page to its backing block in the cache */
 291         int (*write_page)(struct fscache_storage *op, struct page *page);
 292
 293         /* detach backing block from a page (optional)
 294          * - must release the cookie lock before returning
 295          * - may sleep
 296          */
 297         void (*uncache_page)(struct fscache_object *object,
 298                              struct page *page);
 299
 300         /* dissociate a cache from all the pages it was backing */
 301         void (*dissociate_pages)(struct fscache_cache *cache);
 302 };
 303
 304 /*
 305  * data file or index object cookie
 306  * - a file will only appear in one cache
 307  * - a request to cache a file may or may not be honoured, subject to
 308  *   constraints such as disk space
 309  * - indices are created on disk just-in-time
 310  */
 311 struct fscache_cookie {
 312         atomic_t                        usage;          /* number of users of this cookie */
 313         atomic_t                        n_children;     /* number of children of this cookie */
 314         spinlock_t                      lock;
 315         spinlock_t                      stores_lock;    /* lock on page store tree */
 316         struct hlist_head               backing_objects; /* object(s) backing this file/index */
 317         const struct fscache_cookie_def *def;           /* definition */
 318         struct fscache_cookie           *parent;        /* parent of this entry */
 319         void                            *netfs_data;    /* back pointer to netfs */
 320         struct radix_tree_root          stores;         /* pages to be stored on this cookie */
 321 #define FSCACHE_COOKIE_PENDING_TAG      0               /* pages tag: pending write to cache */
 322 #define FSCACHE_COOKIE_STORING_TAG      1               /* pages tag: writing to cache */
 323
 324         unsigned long                   flags;
 325 #define FSCACHE_COOKIE_LOOKING_UP       0       /* T if non-index cookie being looked up still */
 326 #define FSCACHE_COOKIE_CREATING         1       /* T if non-index object being created still */
 327 #define FSCACHE_COOKIE_NO_DATA_YET      2       /* T if new object with no cached data yet */
 328 #define FSCACHE_COOKIE_PENDING_FILL     3       /* T if pending initial fill on object */
 329 #define FSCACHE_COOKIE_FILLING          4       /* T if filling object incrementally */
 330 #define FSCACHE_COOKIE_UNAVAILABLE      5       /* T if cookie is unavailable (error, etc) */
 331 };
 332
 333 extern struct fscache_cookie fscache_fsdef_index;
 334
 335 /*
 336  * on-disk cache file or index handle
 337  */
 338 struct fscache_object {
 339         enum fscache_object_state {
 340                 FSCACHE_OBJECT_INIT,            /* object in initial unbound state */
 341                 FSCACHE_OBJECT_LOOKING_UP,      /* looking up object */
 342                 FSCACHE_OBJECT_CREATING,        /* creating object */
 343
 344                 /* active states */
 345                 FSCACHE_OBJECT_AVAILABLE,       /* cleaning up object after creation */
 346                 FSCACHE_OBJECT_ACTIVE,          /* object is usable */
 347                 FSCACHE_OBJECT_UPDATING,        /* object is updating */
 348
 349                 /* terminal states */
 350                 FSCACHE_OBJECT_DYING,           /* object waiting for accessors to finish */
 351                 FSCACHE_OBJECT_LC_DYING,        /* object cleaning up after lookup/create */
 352                 FSCACHE_OBJECT_ABORT_INIT,      /* abort the init state */
 353                 FSCACHE_OBJECT_RELEASING,       /* releasing object */
 354                 FSCACHE_OBJECT_RECYCLING,       /* retiring object */
 355                 FSCACHE_OBJECT_WITHDRAWING,     /* withdrawing object */
 356                 FSCACHE_OBJECT_DEAD,            /* object is now dead */
 357                 FSCACHE_OBJECT__NSTATES
 358         } state;
 359
 360         int                     debug_id;       /* debugging ID */
 361         int                     n_children;     /* number of child objects */
 362         int                     n_ops;          /* number of ops outstanding on object */
 363         int                     n_obj_ops;      /* number of object ops outstanding on object */
 364         int                     n_in_progress;  /* number of ops in progress */
 365         int                     n_exclusive;    /* number of exclusive ops queued */
 366         atomic_t                n_reads;        /* number of read ops in progress */
 367         spinlock_t              lock;           /* state and operations lock */
 368
 369         unsigned long           lookup_jif;     /* time at which lookup started */
 370         unsigned long           event_mask;     /* events this object is interested in */
 371         unsigned long           events;         /* events to be processed by this object
 372                                                  * (order is important - using fls) */
 373 #define FSCACHE_OBJECT_EV_REQUEUE       0       /* T if object should be requeued */
 374 #define FSCACHE_OBJECT_EV_UPDATE        1       /* T if object should be updated */
 375 #define FSCACHE_OBJECT_EV_CLEARED       2       /* T if accessors all gone */
 376 #define FSCACHE_OBJECT_EV_ERROR         3       /* T if fatal error occurred during processing */
 377 #define FSCACHE_OBJECT_EV_RELEASE       4       /* T if netfs requested object release */
 378 #define FSCACHE_OBJECT_EV_RETIRE        5       /* T if netfs requested object retirement */
 379 #define FSCACHE_OBJECT_EV_WITHDRAW      6       /* T if cache requested object withdrawal */
 380 #define FSCACHE_OBJECT_EVENTS_MASK      0x7f    /* mask of all events*/
 381
 382         unsigned long           flags;
 383 #define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
 384 #define FSCACHE_OBJECT_PENDING_WRITE    1       /* T if object has pending write */
 385 #define FSCACHE_OBJECT_WAITING          2       /* T if object is waiting on its parent */
 386
 387         struct list_head        cache_link;     /* link in cache->object_list */
 388         struct hlist_node       cookie_link;    /* link in cookie->backing_objects */
 389         struct fscache_cache    *cache;         /* cache that supplied this object */
 390         struct fscache_cookie   *cookie;        /* netfs's file/index object */
 391         struct fscache_object   *parent;        /* parent object */
 392         struct slow_work        work;           /* attention scheduling record */
 393         struct list_head        dependents;     /* FIFO of dependent objects */
 394         struct list_head        dep_link;       /* link in parent's dependents list */
 395         struct list_head        pending_ops;    /* unstarted operations on this object */
 396 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 397         struct rb_node          objlist_link;   /* link in global object list */
 398 #endif
 399         pgoff_t                 store_limit;    /* current storage limit */
 400         loff_t                  store_limit_l;  /* current storage limit */
 401 };
 402
 403 extern const char *fscache_object_states[];
 404
 405 #define fscache_object_is_active(obj)                         \
 406         (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&  \
 407          (obj)->state >= FSCACHE_OBJECT_AVAILABLE &&          \
 408          (obj)->state < FSCACHE_OBJECT_DYING)
 409
 410 #define fscache_object_is_dead(obj)                             \
 411         (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&     \
 412          (obj)->state >= FSCACHE_OBJECT_DYING)
 413
 414 extern const struct slow_work_ops fscache_object_slow_work_ops;
 415
 416 /**
 417  * fscache_object_init - Initialise a cache object description
 418  * @object: Object description
 419  *
 420  * Initialise a cache object description to its basic values.
 421  *
 422  * See Documentation/filesystems/caching/backend-api.txt for a complete
 423  * description.
 424  */
 425 static inline
 426 void fscache_object_init(struct fscache_object *object,
 427                          struct fscache_cookie *cookie,
 428                          struct fscache_cache *cache)
 429 {
 430         atomic_inc(&cache->object_count);
 431
 432         object->state = FSCACHE_OBJECT_INIT;
 433         spin_lock_init(&object->lock);
 434         INIT_LIST_HEAD(&object->cache_link);
 435         INIT_HLIST_NODE(&object->cookie_link);
 436         vslow_work_init(&object->work, &fscache_object_slow_work_ops);
 437         INIT_LIST_HEAD(&object->dependents);
 438         INIT_LIST_HEAD(&object->dep_link);
 439         INIT_LIST_HEAD(&object->pending_ops);
 440         object->n_children = 0;
 441         object->n_ops = object->n_in_progress = object->n_exclusive = 0;
 442         object->events = object->event_mask = 0;
 443         object->flags = 0;
 444         object->store_limit = 0;
 445         object->store_limit_l = 0;
 446         object->cache = cache;
 447         object->cookie = cookie;
 448         object->parent = NULL;
 449 }
 450
 451 extern void fscache_object_lookup_negative(struct fscache_object *object);
 452 extern void fscache_obtained_object(struct fscache_object *object);
 453
 454 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 455 extern void fscache_object_destroy(struct fscache_object *object);
 456 #else
 457 #define fscache_object_destroy(object) do {} while(0)
 458 #endif
 459
 460 /**
 461  * fscache_object_destroyed - Note destruction of an object in a cache
 462  * @cache: The cache from which the object came
 463  *
 464  * Note the destruction and deallocation of an object record in a cache.
 465  */
 466 static inline void fscache_object_destroyed(struct fscache_cache *cache)
 467 {
 468         if (atomic_dec_and_test(&cache->object_count))
 469                 wake_up_all(&fscache_cache_cleared_wq);
 470 }
 471
 472 /**
 473  * fscache_object_lookup_error - Note an object encountered an error
 474  * @object: The object on which the error was encountered
 475  *
 476  * Note that an object encountered a fatal error (usually an I/O error) and
 477  * that it should be withdrawn as soon as possible.
 478  */
 479 static inline void fscache_object_lookup_error(struct fscache_object *object)
 480 {
 481         set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
 482 }
 483
 484 /**
 485  * fscache_set_store_limit - Set the maximum size to be stored in an object
 486  * @object: The object to set the maximum on
 487  * @i_size: The limit to set in bytes
 488  *
 489  * Set the maximum size an object is permitted to reach, implying the highest
 490  * byte that may be written.  Intended to be called by the attr_changed() op.
 491  *
 492  * See Documentation/filesystems/caching/backend-api.txt for a complete
 493  * description.
 494  */
 495 static inline
 496 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
 497 {
 498         object->store_limit_l = i_size;
 499         object->store_limit = i_size >> PAGE_SHIFT;
 500         if (i_size & ~PAGE_MASK)
 501                 object->store_limit++;
 502 }
 503
 504 /**
 505  * fscache_end_io - End a retrieval operation on a page
 506  * @op: The FS-Cache operation covering the retrieval
 507  * @page: The page that was to be fetched
 508  * @error: The error code (0 if successful)
 509  *
 510  * Note the end of an operation to retrieve a page, as covered by a particular
 511  * operation record.
 512  */
 513 static inline void fscache_end_io(struct fscache_retrieval *op,
 514                                   struct page *page, int error)
 515 {
 516         op->end_io_func(page, op->context, error);
 517 }
 518
 519 /*
 520  * out-of-line cache backend functions
 521  */
 522 extern void fscache_init_cache(struct fscache_cache *cache,
 523                                const struct fscache_cache_ops *ops,
 524                                const char *idfmt,
 525                                ...) __attribute__ ((format (printf, 3, 4)));
 526
 527 extern int fscache_add_cache(struct fscache_cache *cache,
 528                              struct fscache_object *fsdef,
 529                              const char *tagname);
 530 extern void fscache_withdraw_cache(struct fscache_cache *cache);
 531
 532 extern void fscache_io_error(struct fscache_cache *cache);
 533
 534 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
 535                                       struct pagevec *pagevec);
 536
 537 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 538                                                const void *data,
 539                                                uint16_t datalen);
 540
 541 #endif /* _LINUX_FSCACHE_CACHE_H */