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 enum fscache_obj_ref_trace {
  33         fscache_obj_get_add_to_deps,
  34         fscache_obj_get_queue,
  35         fscache_obj_put_alloc_fail,
  36         fscache_obj_put_attach_fail,
  37         fscache_obj_put_drop_obj,
  38         fscache_obj_put_enq_dep,
  39         fscache_obj_put_queue,
  40         fscache_obj_put_work,
  41         fscache_obj_ref__nr_traces
  42 };
  43
  44 /*
  45  * cache tag definition
  46  */
  47 struct fscache_cache_tag {
  48         struct list_head        link;
  49         struct fscache_cache    *cache;         /* cache referred to by this tag */
  50         unsigned long           flags;
  51 #define FSCACHE_TAG_RESERVED    0               /* T if tag is reserved for a cache */
  52         atomic_t                usage;
  53         char                    name[0];        /* tag name */
  54 };
  55
  56 /*
  57  * cache definition
  58  */
  59 struct fscache_cache {
  60         const struct fscache_cache_ops *ops;
  61         struct fscache_cache_tag *tag;          /* tag representing this cache */
  62         struct kobject          *kobj;          /* system representation of this cache */
  63         struct list_head        link;           /* link in list of caches */
  64         size_t                  max_index_size; /* maximum size of index data */
  65         char                    identifier[36]; /* cache label */
  66
  67         /* node management */
  68         struct work_struct      op_gc;          /* operation garbage collector */
  69         struct list_head        object_list;    /* list of data/index objects */
  70         struct list_head        op_gc_list;     /* list of ops to be deleted */
  71         spinlock_t              object_list_lock;
  72         spinlock_t              op_gc_list_lock;
  73         atomic_t                object_count;   /* no. of live objects in this cache */
  74         struct fscache_object   *fsdef;         /* object for the fsdef index */
  75         unsigned long           flags;
  76 #define FSCACHE_IOERROR         0       /* cache stopped on I/O error */
  77 #define FSCACHE_CACHE_WITHDRAWN 1       /* cache has been withdrawn */
  78 };
  79
  80 extern wait_queue_head_t fscache_cache_cleared_wq;
  81
  82 /*
  83  * operation to be applied to a cache object
  84  * - retrieval initiation operations are done in the context of the process
  85  *   that issued them, and not in an async thread pool
  86  */
  87 typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
  88 typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
  89 typedef void (*fscache_operation_cancel_t)(struct fscache_operation *op);
  90
  91 enum fscache_operation_state {
  92         FSCACHE_OP_ST_BLANK,            /* Op is not yet submitted */
  93         FSCACHE_OP_ST_INITIALISED,      /* Op is initialised */
  94         FSCACHE_OP_ST_PENDING,          /* Op is blocked from running */
  95         FSCACHE_OP_ST_IN_PROGRESS,      /* Op is in progress */
  96         FSCACHE_OP_ST_COMPLETE,         /* Op is complete */
  97         FSCACHE_OP_ST_CANCELLED,        /* Op has been cancelled */
  98         FSCACHE_OP_ST_DEAD              /* Op is now dead */
  99 };
 100
 101 struct fscache_operation {
 102         struct work_struct      work;           /* record for async ops */
 103         struct list_head        pend_link;      /* link in object->pending_ops */
 104         struct fscache_object   *object;        /* object to be operated upon */
 105
 106         unsigned long           flags;
 107 #define FSCACHE_OP_TYPE         0x000f  /* operation type */
 108 #define FSCACHE_OP_ASYNC        0x0001  /* - async op, processor may sleep for disk */
 109 #define FSCACHE_OP_MYTHREAD     0x0002  /* - processing is done be issuing thread, not pool */
 110 #define FSCACHE_OP_WAITING      4       /* cleared when op is woken */
 111 #define FSCACHE_OP_EXCLUSIVE    5       /* exclusive op, other ops must wait */
 112 #define FSCACHE_OP_DEC_READ_CNT 6       /* decrement object->n_reads on destruction */
 113 #define FSCACHE_OP_UNUSE_COOKIE 7       /* call fscache_unuse_cookie() on completion */
 114 #define FSCACHE_OP_KEEP_FLAGS   0x00f0  /* flags to keep when repurposing an op */
 115
 116         enum fscache_operation_state state;
 117         atomic_t                usage;
 118         unsigned                debug_id;       /* debugging ID */
 119
 120         /* operation processor callback
 121          * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
 122          *   the op in a non-pool thread */
 123         fscache_operation_processor_t processor;
 124
 125         /* Operation cancellation cleanup (optional) */
 126         fscache_operation_cancel_t cancel;
 127
 128         /* operation releaser */
 129         fscache_operation_release_t release;
 130 };
 131
 132 extern atomic_t fscache_op_debug_id;
 133 extern void fscache_op_work_func(struct work_struct *work);
 134
 135 extern void fscache_enqueue_operation(struct fscache_operation *);
 136 extern void fscache_op_complete(struct fscache_operation *, bool);
 137 extern void fscache_put_operation(struct fscache_operation *);
 138 extern void fscache_operation_init(struct fscache_cookie *,
 139                                    struct fscache_operation *,
 140                                    fscache_operation_processor_t,
 141                                    fscache_operation_cancel_t,
 142                                    fscache_operation_release_t);
 143
 144 /*
 145  * data read operation
 146  */
 147 struct fscache_retrieval {
 148         struct fscache_operation op;
 149         struct fscache_cookie   *cookie;        /* The netfs cookie */
 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         atomic_t                n_pages;        /* number of pages to be retrieved */
 156 };
 157
 158 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
 159                                              struct page *page,
 160                                              gfp_t gfp);
 161
 162 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
 163                                               struct list_head *pages,
 164                                               unsigned *nr_pages,
 165                                               gfp_t gfp);
 166
 167 /**
 168  * fscache_get_retrieval - Get an extra reference on a retrieval operation
 169  * @op: The retrieval operation to get a reference on
 170  *
 171  * Get an extra reference on a retrieval operation.
 172  */
 173 static inline
 174 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
 175 {
 176         atomic_inc(&op->op.usage);
 177         return op;
 178 }
 179
 180 /**
 181  * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
 182  * @op: The retrieval operation affected
 183  *
 184  * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
 185  */
 186 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
 187 {
 188         fscache_enqueue_operation(&op->op);
 189 }
 190
 191 /**
 192  * fscache_retrieval_complete - Record (partial) completion of a retrieval
 193  * @op: The retrieval operation affected
 194  * @n_pages: The number of pages to account for
 195  */
 196 static inline void fscache_retrieval_complete(struct fscache_retrieval *op,
 197                                               int n_pages)
 198 {
 199         if (atomic_sub_return_relaxed(n_pages, &op->n_pages) <= 0)
 200                 fscache_op_complete(&op->op, false);
 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                                               enum fscache_obj_ref_trace why);
 248
 249         /* pin an object in the cache */
 250         int (*pin_object)(struct fscache_object *object);
 251
 252         /* unpin an object in the cache */
 253         void (*unpin_object)(struct fscache_object *object);
 254
 255         /* check the consistency between the backing cache and the FS-Cache
 256          * cookie */
 257         int (*check_consistency)(struct fscache_operation *op);
 258
 259         /* store the updated auxiliary data on an object */
 260         void (*update_object)(struct fscache_object *object);
 261
 262         /* Invalidate an object */
 263         void (*invalidate_object)(struct fscache_operation *op);
 264
 265         /* discard the resources pinned by an object and effect retirement if
 266          * necessary */
 267         void (*drop_object)(struct fscache_object *object);
 268
 269         /* dispose of a reference to an object */
 270         void (*put_object)(struct fscache_object *object,
 271                            enum fscache_obj_ref_trace why);
 272
 273         /* sync a cache */
 274         void (*sync_cache)(struct fscache_cache *cache);
 275
 276         /* notification that the attributes of a non-index object (such as
 277          * i_size) have changed */
 278         int (*attr_changed)(struct fscache_object *object);
 279
 280         /* reserve space for an object's data and associated metadata */
 281         int (*reserve_space)(struct fscache_object *object, loff_t i_size);
 282
 283         /* request a backing block for a page be read or allocated in the
 284          * cache */
 285         fscache_page_retrieval_func_t read_or_alloc_page;
 286
 287         /* request backing blocks for a list of pages be read or allocated in
 288          * the cache */
 289         fscache_pages_retrieval_func_t read_or_alloc_pages;
 290
 291         /* request a backing block for a page be allocated in the cache so that
 292          * it can be written directly */
 293         fscache_page_retrieval_func_t allocate_page;
 294
 295         /* request backing blocks for pages be allocated in the cache so that
 296          * they can be written directly */
 297         fscache_pages_retrieval_func_t allocate_pages;
 298
 299         /* write a page to its backing block in the cache */
 300         int (*write_page)(struct fscache_storage *op, struct page *page);
 301
 302         /* detach backing block from a page (optional)
 303          * - must release the cookie lock before returning
 304          * - may sleep
 305          */
 306         void (*uncache_page)(struct fscache_object *object,
 307                              struct page *page);
 308
 309         /* dissociate a cache from all the pages it was backing */
 310         void (*dissociate_pages)(struct fscache_cache *cache);
 311 };
 312
 313 extern struct fscache_cookie fscache_fsdef_index;
 314
 315 /*
 316  * Event list for fscache_object::{event_mask,events}
 317  */
 318 enum {
 319         FSCACHE_OBJECT_EV_NEW_CHILD,    /* T if object has a new child */
 320         FSCACHE_OBJECT_EV_PARENT_READY, /* T if object's parent is ready */
 321         FSCACHE_OBJECT_EV_UPDATE,       /* T if object should be updated */
 322         FSCACHE_OBJECT_EV_INVALIDATE,   /* T if cache requested object invalidation */
 323         FSCACHE_OBJECT_EV_CLEARED,      /* T if accessors all gone */
 324         FSCACHE_OBJECT_EV_ERROR,        /* T if fatal error occurred during processing */
 325         FSCACHE_OBJECT_EV_KILL,         /* T if netfs relinquished or cache withdrew object */
 326         NR_FSCACHE_OBJECT_EVENTS
 327 };
 328
 329 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
 330
 331 /*
 332  * States for object state machine.
 333  */
 334 struct fscache_transition {
 335         unsigned long events;
 336         const struct fscache_state *transit_to;
 337 };
 338
 339 struct fscache_state {
 340         char name[24];
 341         char short_name[8];
 342         const struct fscache_state *(*work)(struct fscache_object *object,
 343                                             int event);
 344         const struct fscache_transition transitions[];
 345 };
 346
 347 /*
 348  * on-disk cache file or index handle
 349  */
 350 struct fscache_object {
 351         const struct fscache_state *state;      /* Object state machine state */
 352         const struct fscache_transition *oob_table; /* OOB state transition table */
 353         int                     debug_id;       /* debugging ID */
 354         int                     n_children;     /* number of child objects */
 355         int                     n_ops;          /* number of extant ops on object */
 356         int                     n_obj_ops;      /* number of object ops outstanding on object */
 357         int                     n_in_progress;  /* number of ops in progress */
 358         int                     n_exclusive;    /* number of exclusive ops queued or in progress */
 359         atomic_t                n_reads;        /* number of read ops in progress */
 360         spinlock_t              lock;           /* state and operations lock */
 361
 362         unsigned long           lookup_jif;     /* time at which lookup started */
 363         unsigned long           oob_event_mask; /* OOB events this object is interested in */
 364         unsigned long           event_mask;     /* events this object is interested in */
 365         unsigned long           events;         /* events to be processed by this object
 366                                                  * (order is important - using fls) */
 367
 368         unsigned long           flags;
 369 #define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
 370 #define FSCACHE_OBJECT_PENDING_WRITE    1       /* T if object has pending write */
 371 #define FSCACHE_OBJECT_WAITING          2       /* T if object is waiting on its parent */
 372 #define FSCACHE_OBJECT_IS_LIVE          3       /* T if object is not withdrawn or relinquished */
 373 #define FSCACHE_OBJECT_IS_LOOKED_UP     4       /* T if object has been looked up */
 374 #define FSCACHE_OBJECT_IS_AVAILABLE     5       /* T if object has become active */
 375 #define FSCACHE_OBJECT_RETIRED          6       /* T if object was retired on relinquishment */
 376 #define FSCACHE_OBJECT_KILLED_BY_CACHE  7       /* T if object was killed by the cache */
 377 #define FSCACHE_OBJECT_RUN_AFTER_DEAD   8       /* T if object has been dispatched after death */
 378
 379         struct list_head        cache_link;     /* link in cache->object_list */
 380         struct hlist_node       cookie_link;    /* link in cookie->backing_objects */
 381         struct fscache_cache    *cache;         /* cache that supplied this object */
 382         struct fscache_cookie   *cookie;        /* netfs's file/index object */
 383         struct fscache_object   *parent;        /* parent object */
 384         struct work_struct      work;           /* attention scheduling record */
 385         struct list_head        dependents;     /* FIFO of dependent objects */
 386         struct list_head        dep_link;       /* link in parent's dependents list */
 387         struct list_head        pending_ops;    /* unstarted operations on this object */
 388 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 389         struct rb_node          objlist_link;   /* link in global object list */
 390 #endif
 391         pgoff_t                 store_limit;    /* current storage limit */
 392         loff_t                  store_limit_l;  /* current storage limit */
 393 };
 394
 395 extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *,
 396                                 struct fscache_cache *);
 397 extern void fscache_object_destroy(struct fscache_object *);
 398
 399 extern void fscache_object_lookup_negative(struct fscache_object *object);
 400 extern void fscache_obtained_object(struct fscache_object *object);
 401
 402 static inline bool fscache_object_is_live(struct fscache_object *object)
 403 {
 404         return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 405 }
 406
 407 static inline bool fscache_object_is_dying(struct fscache_object *object)
 408 {
 409         return !fscache_object_is_live(object);
 410 }
 411
 412 static inline bool fscache_object_is_available(struct fscache_object *object)
 413 {
 414         return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 415 }
 416
 417 static inline bool fscache_cache_is_broken(struct fscache_object *object)
 418 {
 419         return test_bit(FSCACHE_IOERROR, &object->cache->flags);
 420 }
 421
 422 static inline bool fscache_object_is_active(struct fscache_object *object)
 423 {
 424         return fscache_object_is_available(object) &&
 425                 fscache_object_is_live(object) &&
 426                 !fscache_cache_is_broken(object);
 427 }
 428
 429 /**
 430  * fscache_object_destroyed - Note destruction of an object in a cache
 431  * @cache: The cache from which the object came
 432  *
 433  * Note the destruction and deallocation of an object record in a cache.
 434  */
 435 static inline void fscache_object_destroyed(struct fscache_cache *cache)
 436 {
 437         if (atomic_dec_and_test(&cache->object_count))
 438                 wake_up_all(&fscache_cache_cleared_wq);
 439 }
 440
 441 /**
 442  * fscache_object_lookup_error - Note an object encountered an error
 443  * @object: The object on which the error was encountered
 444  *
 445  * Note that an object encountered a fatal error (usually an I/O error) and
 446  * that it should be withdrawn as soon as possible.
 447  */
 448 static inline void fscache_object_lookup_error(struct fscache_object *object)
 449 {
 450         set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
 451 }
 452
 453 /**
 454  * fscache_set_store_limit - Set the maximum size to be stored in an object
 455  * @object: The object to set the maximum on
 456  * @i_size: The limit to set in bytes
 457  *
 458  * Set the maximum size an object is permitted to reach, implying the highest
 459  * byte that may be written.  Intended to be called by the attr_changed() op.
 460  *
 461  * See Documentation/filesystems/caching/backend-api.txt for a complete
 462  * description.
 463  */
 464 static inline
 465 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
 466 {
 467         object->store_limit_l = i_size;
 468         object->store_limit = i_size >> PAGE_SHIFT;
 469         if (i_size & ~PAGE_MASK)
 470                 object->store_limit++;
 471 }
 472
 473 /**
 474  * fscache_end_io - End a retrieval operation on a page
 475  * @op: The FS-Cache operation covering the retrieval
 476  * @page: The page that was to be fetched
 477  * @error: The error code (0 if successful)
 478  *
 479  * Note the end of an operation to retrieve a page, as covered by a particular
 480  * operation record.
 481  */
 482 static inline void fscache_end_io(struct fscache_retrieval *op,
 483                                   struct page *page, int error)
 484 {
 485         op->end_io_func(page, op->context, error);
 486 }
 487
 488 static inline void __fscache_use_cookie(struct fscache_cookie *cookie)
 489 {
 490         atomic_inc(&cookie->n_active);
 491 }
 492
 493 /**
 494  * fscache_use_cookie - Request usage of cookie attached to an object
 495  * @object: Object description
 496  *
 497  * Request usage of the cookie attached to an object.  NULL is returned if the
 498  * relinquishment had reduced the cookie usage count to 0.
 499  */
 500 static inline bool fscache_use_cookie(struct fscache_object *object)
 501 {
 502         struct fscache_cookie *cookie = object->cookie;
 503         return atomic_inc_not_zero(&cookie->n_active) != 0;
 504 }
 505
 506 static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie)
 507 {
 508         return atomic_dec_and_test(&cookie->n_active);
 509 }
 510
 511 static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie)
 512 {
 513         wake_up_var(&cookie->n_active);
 514 }
 515
 516 /**
 517  * fscache_unuse_cookie - Cease usage of cookie attached to an object
 518  * @object: Object description
 519  *
 520  * Cease usage of the cookie attached to an object.  When the users count
 521  * reaches zero then the cookie relinquishment will be permitted to proceed.
 522  */
 523 static inline void fscache_unuse_cookie(struct fscache_object *object)
 524 {
 525         struct fscache_cookie *cookie = object->cookie;
 526         if (__fscache_unuse_cookie(cookie))
 527                 __fscache_wake_unused_cookie(cookie);
 528 }
 529
 530 /*
 531  * out-of-line cache backend functions
 532  */
 533 extern __printf(3, 4)
 534 void fscache_init_cache(struct fscache_cache *cache,
 535                         const struct fscache_cache_ops *ops,
 536                         const char *idfmt, ...);
 537
 538 extern int fscache_add_cache(struct fscache_cache *cache,
 539                              struct fscache_object *fsdef,
 540                              const char *tagname);
 541 extern void fscache_withdraw_cache(struct fscache_cache *cache);
 542
 543 extern void fscache_io_error(struct fscache_cache *cache);
 544
 545 extern void fscache_mark_page_cached(struct fscache_retrieval *op,
 546                                      struct page *page);
 547
 548 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
 549                                       struct pagevec *pagevec);
 550
 551 extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
 552
 553 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 554                                                const void *data,
 555                                                uint16_t datalen,
 556                                                loff_t object_size);
 557
 558 extern void fscache_object_retrying_stale(struct fscache_object *object);
 559
 560 enum fscache_why_object_killed {
 561         FSCACHE_OBJECT_IS_STALE,
 562         FSCACHE_OBJECT_NO_SPACE,
 563         FSCACHE_OBJECT_WAS_RETIRED,
 564         FSCACHE_OBJECT_WAS_CULLED,
 565 };
 566 extern void fscache_object_mark_killed(struct fscache_object *object,
 567                                        enum fscache_why_object_killed why);
 568
 569 #endif /* _LINUX_FSCACHE_CACHE_H */