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 #ifdef CONFIG_WORKQUEUE_DEBUGFS
 105         struct work_struct put_work;    /* work to delay operation put */
 106         const char *name;               /* operation name */
 107         const char *state;              /* operation state */
 108 #define fscache_set_op_name(OP, N)      do { (OP)->name  = (N); } while(0)
 109 #define fscache_set_op_state(OP, S)     do { (OP)->state = (S); } while(0)
 110 #else
 111 #define fscache_set_op_name(OP, N)      do { } while(0)
 112 #define fscache_set_op_state(OP, S)     do { } while(0)
 113 #endif
 114 };
 115
 116 extern atomic_t fscache_op_debug_id;
 117 extern void fscache_op_work_func(struct work_struct *work);
 118
 119 extern void fscache_enqueue_operation(struct fscache_operation *);
 120 extern void fscache_put_operation(struct fscache_operation *);
 121
 122 /**
 123  * fscache_operation_init - Do basic initialisation of an operation
 124  * @op: The operation to initialise
 125  * @release: The release function to assign
 126  *
 127  * Do basic initialisation of an operation.  The caller must still set flags,
 128  * object and processor if needed.
 129  */
 130 static inline void fscache_operation_init(struct fscache_operation *op,
 131                                         fscache_operation_processor_t processor,
 132                                         fscache_operation_release_t release)
 133 {
 134         INIT_WORK(&op->work, fscache_op_work_func);
 135         atomic_set(&op->usage, 1);
 136         op->debug_id = atomic_inc_return(&fscache_op_debug_id);
 137         op->processor = processor;
 138         op->release = release;
 139         INIT_LIST_HEAD(&op->pend_link);
 140         fscache_set_op_state(op, "Init");
 141 }
 142
 143 /*
 144  * data read operation
 145  */
 146 struct fscache_retrieval {
 147         struct fscache_operation op;
 148         struct address_space    *mapping;       /* netfs pages */
 149         fscache_rw_complete_t   end_io_func;    /* function to call on I/O completion */
 150         void                    *context;       /* netfs read context (pinned) */
 151         struct list_head        to_do;          /* list of things to be done by the backend */
 152         unsigned long           start_time;     /* time at which retrieval started */
 153 };
 154
 155 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
 156                                              struct page *page,
 157                                              gfp_t gfp);
 158
 159 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
 160                                               struct list_head *pages,
 161                                               unsigned *nr_pages,
 162                                               gfp_t gfp);
 163
 164 /**
 165  * fscache_get_retrieval - Get an extra reference on a retrieval operation
 166  * @op: The retrieval operation to get a reference on
 167  *
 168  * Get an extra reference on a retrieval operation.
 169  */
 170 static inline
 171 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
 172 {
 173         atomic_inc(&op->op.usage);
 174         return op;
 175 }
 176
 177 /**
 178  * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
 179  * @op: The retrieval operation affected
 180  *
 181  * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
 182  */
 183 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
 184 {
 185         fscache_enqueue_operation(&op->op);
 186 }
 187
 188 /**
 189  * fscache_put_retrieval - Drop a reference to a retrieval operation
 190  * @op: The retrieval operation affected
 191  *
 192  * Drop a reference to a retrieval operation.
 193  */
 194 static inline void fscache_put_retrieval(struct fscache_retrieval *op)
 195 {
 196         fscache_put_operation(&op->op);
 197 }
 198
 199 /*
 200  * cached page storage work item
 201  * - used to do three things:
 202  *   - batch writes to the cache
 203  *   - do cache writes asynchronously
 204  *   - defer writes until cache object lookup completion
 205  */
 206 struct fscache_storage {
 207         struct fscache_operation op;
 208         pgoff_t                 store_limit;    /* don't write more than this */
 209 };
 210
 211 /*
 212  * cache operations
 213  */
 214 struct fscache_cache_ops {
 215         /* name of cache provider */
 216         const char *name;
 217
 218         /* allocate an object record for a cookie */
 219         struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
 220                                                struct fscache_cookie *cookie);
 221
 222         /* look up the object for a cookie
 223          * - return -ETIMEDOUT to be requeued
 224          */
 225         int (*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         spinlock_t                      stores_lock;    /* lock on page store tree */
 301         struct hlist_head               backing_objects; /* object(s) backing this file/index */
 302         const struct fscache_cookie_def *def;           /* definition */
 303         struct fscache_cookie           *parent;        /* parent of this entry */
 304         void                            *netfs_data;    /* back pointer to netfs */
 305         struct radix_tree_root          stores;         /* pages to be stored on this cookie */
 306 #define FSCACHE_COOKIE_PENDING_TAG      0               /* pages tag: pending write to cache */
 307 #define FSCACHE_COOKIE_STORING_TAG      1               /* pages tag: writing to cache */
 308
 309         unsigned long                   flags;
 310 #define FSCACHE_COOKIE_LOOKING_UP       0       /* T if non-index cookie being looked up still */
 311 #define FSCACHE_COOKIE_CREATING         1       /* T if non-index object being created still */
 312 #define FSCACHE_COOKIE_NO_DATA_YET      2       /* T if new object with no cached data yet */
 313 #define FSCACHE_COOKIE_PENDING_FILL     3       /* T if pending initial fill on object */
 314 #define FSCACHE_COOKIE_FILLING          4       /* T if filling object incrementally */
 315 #define FSCACHE_COOKIE_UNAVAILABLE      5       /* T if cookie is unavailable (error, etc) */
 316 };
 317
 318 extern struct fscache_cookie fscache_fsdef_index;
 319
 320 /*
 321  * on-disk cache file or index handle
 322  */
 323 struct fscache_object {
 324         enum fscache_object_state {
 325                 FSCACHE_OBJECT_INIT,            /* object in initial unbound state */
 326                 FSCACHE_OBJECT_LOOKING_UP,      /* looking up object */
 327                 FSCACHE_OBJECT_CREATING,        /* creating object */
 328
 329                 /* active states */
 330                 FSCACHE_OBJECT_AVAILABLE,       /* cleaning up object after creation */
 331                 FSCACHE_OBJECT_ACTIVE,          /* object is usable */
 332                 FSCACHE_OBJECT_UPDATING,        /* object is updating */
 333
 334                 /* terminal states */
 335                 FSCACHE_OBJECT_DYING,           /* object waiting for accessors to finish */
 336                 FSCACHE_OBJECT_LC_DYING,        /* object cleaning up after lookup/create */
 337                 FSCACHE_OBJECT_ABORT_INIT,      /* abort the init state */
 338                 FSCACHE_OBJECT_RELEASING,       /* releasing object */
 339                 FSCACHE_OBJECT_RECYCLING,       /* retiring object */
 340                 FSCACHE_OBJECT_WITHDRAWING,     /* withdrawing object */
 341                 FSCACHE_OBJECT_DEAD,            /* object is now dead */
 342                 FSCACHE_OBJECT__NSTATES
 343         } state;
 344
 345         int                     debug_id;       /* debugging ID */
 346         int                     n_children;     /* number of child objects */
 347         int                     n_ops;          /* number of ops outstanding on object */
 348         int                     n_obj_ops;      /* number of object ops outstanding on object */
 349         int                     n_in_progress;  /* number of ops in progress */
 350         int                     n_exclusive;    /* number of exclusive ops queued */
 351         atomic_t                n_reads;        /* number of read ops in progress */
 352         spinlock_t              lock;           /* state and operations lock */
 353
 354         unsigned long           lookup_jif;     /* time at which lookup started */
 355         unsigned long           event_mask;     /* events this object is interested in */
 356         unsigned long           events;         /* events to be processed by this object
 357                                                  * (order is important - using fls) */
 358 #define FSCACHE_OBJECT_EV_REQUEUE       0       /* T if object should be requeued */
 359 #define FSCACHE_OBJECT_EV_UPDATE        1       /* T if object should be updated */
 360 #define FSCACHE_OBJECT_EV_CLEARED       2       /* T if accessors all gone */
 361 #define FSCACHE_OBJECT_EV_ERROR         3       /* T if fatal error occurred during processing */
 362 #define FSCACHE_OBJECT_EV_RELEASE       4       /* T if netfs requested object release */
 363 #define FSCACHE_OBJECT_EV_RETIRE        5       /* T if netfs requested object retirement */
 364 #define FSCACHE_OBJECT_EV_WITHDRAW      6       /* T if cache requested object withdrawal */
 365 #define FSCACHE_OBJECT_EVENTS_MASK      0x7f    /* mask of all events*/
 366
 367         unsigned long           flags;
 368 #define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
 369 #define FSCACHE_OBJECT_PENDING_WRITE    1       /* T if object has pending write */
 370 #define FSCACHE_OBJECT_WAITING          2       /* T if object is waiting on its parent */
 371
 372         struct list_head        cache_link;     /* link in cache->object_list */
 373         struct hlist_node       cookie_link;    /* link in cookie->backing_objects */
 374         struct fscache_cache    *cache;         /* cache that supplied this object */
 375         struct fscache_cookie   *cookie;        /* netfs's file/index object */
 376         struct fscache_object   *parent;        /* parent object */
 377         struct work_struct      work;           /* attention scheduling record */
 378         struct list_head        dependents;     /* FIFO of dependent objects */
 379         struct list_head        dep_link;       /* link in parent's dependents list */
 380         struct list_head        pending_ops;    /* unstarted operations on this object */
 381 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 382         struct rb_node          objlist_link;   /* link in global object list */
 383 #endif
 384         pgoff_t                 store_limit;    /* current storage limit */
 385         loff_t                  store_limit_l;  /* current storage limit */
 386 };
 387
 388 extern const char *fscache_object_states[];
 389
 390 #define fscache_object_is_active(obj)                         \
 391         (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&  \
 392          (obj)->state >= FSCACHE_OBJECT_AVAILABLE &&          \
 393          (obj)->state < FSCACHE_OBJECT_DYING)
 394
 395 #define fscache_object_is_dead(obj)                             \
 396         (test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&     \
 397          (obj)->state >= FSCACHE_OBJECT_DYING)
 398
 399 extern void fscache_object_work_func(struct work_struct *work);
 400
 401 /**
 402  * fscache_object_init - Initialise a cache object description
 403  * @object: Object description
 404  *
 405  * Initialise a cache object description to its basic values.
 406  *
 407  * See Documentation/filesystems/caching/backend-api.txt for a complete
 408  * description.
 409  */
 410 static inline
 411 void fscache_object_init(struct fscache_object *object,
 412                          struct fscache_cookie *cookie,
 413                          struct fscache_cache *cache)
 414 {
 415         atomic_inc(&cache->object_count);
 416
 417         object->state = FSCACHE_OBJECT_INIT;
 418         spin_lock_init(&object->lock);
 419         INIT_LIST_HEAD(&object->cache_link);
 420         INIT_HLIST_NODE(&object->cookie_link);
 421         INIT_WORK(&object->work, fscache_object_work_func);
 422         INIT_LIST_HEAD(&object->dependents);
 423         INIT_LIST_HEAD(&object->dep_link);
 424         INIT_LIST_HEAD(&object->pending_ops);
 425         object->n_children = 0;
 426         object->n_ops = object->n_in_progress = object->n_exclusive = 0;
 427         object->events = object->event_mask = 0;
 428         object->flags = 0;
 429         object->store_limit = 0;
 430         object->store_limit_l = 0;
 431         object->cache = cache;
 432         object->cookie = cookie;
 433         object->parent = NULL;
 434 }
 435
 436 extern void fscache_object_lookup_negative(struct fscache_object *object);
 437 extern void fscache_obtained_object(struct fscache_object *object);
 438
 439 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 440 extern void fscache_object_destroy(struct fscache_object *object);
 441 #else
 442 #define fscache_object_destroy(object) do {} while(0)
 443 #endif
 444
 445 /**
 446  * fscache_object_destroyed - Note destruction of an object in a cache
 447  * @cache: The cache from which the object came
 448  *
 449  * Note the destruction and deallocation of an object record in a cache.
 450  */
 451 static inline void fscache_object_destroyed(struct fscache_cache *cache)
 452 {
 453         if (atomic_dec_and_test(&cache->object_count))
 454                 wake_up_all(&fscache_cache_cleared_wq);
 455 }
 456
 457 /**
 458  * fscache_object_lookup_error - Note an object encountered an error
 459  * @object: The object on which the error was encountered
 460  *
 461  * Note that an object encountered a fatal error (usually an I/O error) and
 462  * that it should be withdrawn as soon as possible.
 463  */
 464 static inline void fscache_object_lookup_error(struct fscache_object *object)
 465 {
 466         set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
 467 }
 468
 469 /**
 470  * fscache_set_store_limit - Set the maximum size to be stored in an object
 471  * @object: The object to set the maximum on
 472  * @i_size: The limit to set in bytes
 473  *
 474  * Set the maximum size an object is permitted to reach, implying the highest
 475  * byte that may be written.  Intended to be called by the attr_changed() op.
 476  *
 477  * See Documentation/filesystems/caching/backend-api.txt for a complete
 478  * description.
 479  */
 480 static inline
 481 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
 482 {
 483         object->store_limit_l = i_size;
 484         object->store_limit = i_size >> PAGE_SHIFT;
 485         if (i_size & ~PAGE_MASK)
 486                 object->store_limit++;
 487 }
 488
 489 /**
 490  * fscache_end_io - End a retrieval operation on a page
 491  * @op: The FS-Cache operation covering the retrieval
 492  * @page: The page that was to be fetched
 493  * @error: The error code (0 if successful)
 494  *
 495  * Note the end of an operation to retrieve a page, as covered by a particular
 496  * operation record.
 497  */
 498 static inline void fscache_end_io(struct fscache_retrieval *op,
 499                                   struct page *page, int error)
 500 {
 501         op->end_io_func(page, op->context, error);
 502 }
 503
 504 /*
 505  * out-of-line cache backend functions
 506  */
 507 extern void fscache_init_cache(struct fscache_cache *cache,
 508                                const struct fscache_cache_ops *ops,
 509                                const char *idfmt,
 510                                ...) __attribute__ ((format (printf, 3, 4)));
 511
 512 extern int fscache_add_cache(struct fscache_cache *cache,
 513                              struct fscache_object *fsdef,
 514                              const char *tagname);
 515 extern void fscache_withdraw_cache(struct fscache_cache *cache);
 516
 517 extern void fscache_io_error(struct fscache_cache *cache);
 518
 519 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
 520                                       struct pagevec *pagevec);
 521
 522 extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
 523
 524 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 525                                                const void *data,
 526                                                uint16_t datalen);
 527
 528 #endif /* _LINUX_FSCACHE_CACHE_H */