root/include/linux/fscache-cache.h

INCLUDED FROM

DEFINITIONS

1. fscache_get_retrieval
2. fscache_enqueue_retrieval
3. fscache_retrieval_complete
4. fscache_put_retrieval
5. fscache_object_is_live
6. fscache_object_is_dying
7. fscache_object_is_available
8. fscache_cache_is_broken
9. fscache_object_is_active
10. fscache_object_destroyed
11. fscache_object_lookup_error
12. fscache_set_store_limit
13. fscache_end_io
14. __fscache_use_cookie
15. fscache_use_cookie
16. __fscache_unuse_cookie
17. __fscache_wake_unused_cookie
18. fscache_unuse_cookie
19. __printf

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /* General filesystem caching backing cache interface
   3  *
   4  * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  *
   7  * NOTE!!! See:
   8  *
   9  *      Documentation/filesystems/caching/backend-api.txt
  10  *
  11  * for a description of the cache backend interface declared here.
  12  */
  13 
  14 #ifndef _LINUX_FSCACHE_CACHE_H
  15 #define _LINUX_FSCACHE_CACHE_H
  16 
  17 #include <linux/fscache.h>
  18 #include <linux/sched.h>
  19 #include <linux/workqueue.h>
  20 
  21 #define NR_MAXCACHES BITS_PER_LONG
  22 
  23 struct fscache_cache;
  24 struct fscache_cache_ops;
  25 struct fscache_object;
  26 struct fscache_operation;
  27 
  28 enum fscache_obj_ref_trace {
  29         fscache_obj_get_add_to_deps,
  30         fscache_obj_get_queue,
  31         fscache_obj_put_alloc_fail,
  32         fscache_obj_put_attach_fail,
  33         fscache_obj_put_drop_obj,
  34         fscache_obj_put_enq_dep,
  35         fscache_obj_put_queue,
  36         fscache_obj_put_work,
  37         fscache_obj_ref__nr_traces
  38 };
  39 
  40 /*
  41  * cache tag definition
  42  */
  43 struct fscache_cache_tag {
  44         struct list_head        link;
  45         struct fscache_cache    *cache;         /* cache referred to by this tag */
  46         unsigned long           flags;
  47 #define FSCACHE_TAG_RESERVED    0               /* T if tag is reserved for a cache */
  48         atomic_t                usage;
  49         char                    name[0];        /* tag name */
  50 };
  51 
  52 /*
  53  * cache definition
  54  */
  55 struct fscache_cache {
  56         const struct fscache_cache_ops *ops;
  57         struct fscache_cache_tag *tag;          /* tag representing this cache */
  58         struct kobject          *kobj;          /* system representation of this cache */
  59         struct list_head        link;           /* link in list of caches */
  60         size_t                  max_index_size; /* maximum size of index data */
  61         char                    identifier[36]; /* cache label */
  62 
  63         /* node management */
  64         struct work_struct      op_gc;          /* operation garbage collector */
  65         struct list_head        object_list;    /* list of data/index objects */
  66         struct list_head        op_gc_list;     /* list of ops to be deleted */
  67         spinlock_t              object_list_lock;
  68         spinlock_t              op_gc_list_lock;
  69         atomic_t                object_count;   /* no. of live objects in this cache */
  70         struct fscache_object   *fsdef;         /* object for the fsdef index */
  71         unsigned long           flags;
  72 #define FSCACHE_IOERROR         0       /* cache stopped on I/O error */
  73 #define FSCACHE_CACHE_WITHDRAWN 1       /* cache has been withdrawn */
  74 };
  75 
  76 extern wait_queue_head_t fscache_cache_cleared_wq;
  77 
  78 /*
  79  * operation to be applied to a cache object
  80  * - retrieval initiation operations are done in the context of the process
  81  *   that issued them, and not in an async thread pool
  82  */
  83 typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
  84 typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
  85 typedef void (*fscache_operation_cancel_t)(struct fscache_operation *op);
  86 
  87 enum fscache_operation_state {
  88         FSCACHE_OP_ST_BLANK,            /* Op is not yet submitted */
  89         FSCACHE_OP_ST_INITIALISED,      /* Op is initialised */
  90         FSCACHE_OP_ST_PENDING,          /* Op is blocked from running */
  91         FSCACHE_OP_ST_IN_PROGRESS,      /* Op is in progress */
  92         FSCACHE_OP_ST_COMPLETE,         /* Op is complete */
  93         FSCACHE_OP_ST_CANCELLED,        /* Op has been cancelled */
  94         FSCACHE_OP_ST_DEAD              /* Op is now dead */
  95 };
  96 
  97 struct fscache_operation {
  98         struct work_struct      work;           /* record for async ops */
  99         struct list_head        pend_link;      /* link in object->pending_ops */
 100         struct fscache_object   *object;        /* object to be operated upon */
 101 
 102         unsigned long           flags;
 103 #define FSCACHE_OP_TYPE         0x000f  /* operation type */
 104 #define FSCACHE_OP_ASYNC        0x0001  /* - async op, processor may sleep for disk */
 105 #define FSCACHE_OP_MYTHREAD     0x0002  /* - processing is done be issuing thread, not pool */
 106 #define FSCACHE_OP_WAITING      4       /* cleared when op is woken */
 107 #define FSCACHE_OP_EXCLUSIVE    5       /* exclusive op, other ops must wait */
 108 #define FSCACHE_OP_DEC_READ_CNT 6       /* decrement object->n_reads on destruction */
 109 #define FSCACHE_OP_UNUSE_COOKIE 7       /* call fscache_unuse_cookie() on completion */
 110 #define FSCACHE_OP_KEEP_FLAGS   0x00f0  /* flags to keep when repurposing an op */
 111 
 112         enum fscache_operation_state state;
 113         atomic_t                usage;
 114         unsigned                debug_id;       /* debugging ID */
 115 
 116         /* operation processor callback
 117          * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
 118          *   the op in a non-pool thread */
 119         fscache_operation_processor_t processor;
 120 
 121         /* Operation cancellation cleanup (optional) */
 122         fscache_operation_cancel_t cancel;
 123 
 124         /* operation releaser */
 125         fscache_operation_release_t release;
 126 };
 127 
 128 extern atomic_t fscache_op_debug_id;
 129 extern void fscache_op_work_func(struct work_struct *work);
 130 
 131 extern void fscache_enqueue_operation(struct fscache_operation *);
 132 extern void fscache_op_complete(struct fscache_operation *, bool);
 133 extern void fscache_put_operation(struct fscache_operation *);
 134 extern void fscache_operation_init(struct fscache_cookie *,
 135                                    struct fscache_operation *,
 136                                    fscache_operation_processor_t,
 137                                    fscache_operation_cancel_t,
 138                                    fscache_operation_release_t);
 139 
 140 /*
 141  * data read operation
 142  */
 143 struct fscache_retrieval {
 144         struct fscache_operation op;
 145         struct fscache_cookie   *cookie;        /* The netfs cookie */
 146         struct address_space    *mapping;       /* netfs pages */
 147         fscache_rw_complete_t   end_io_func;    /* function to call on I/O completion */
 148         void                    *context;       /* netfs read context (pinned) */
 149         struct list_head        to_do;          /* list of things to be done by the backend */
 150         unsigned long           start_time;     /* time at which retrieval started */
 151         atomic_t                n_pages;        /* number of pages to be retrieved */
 152 };
 153 
 154 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
 155                                              struct page *page,
 156                                              gfp_t gfp);
 157 
 158 typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
 159                                               struct list_head *pages,
 160                                               unsigned *nr_pages,
 161                                               gfp_t gfp);
 162 
 163 /**
 164  * fscache_get_retrieval - Get an extra reference on a retrieval operation
 165  * @op: The retrieval operation to get a reference on
 166  *
 167  * Get an extra reference on a retrieval operation.
 168  */
 169 static inline
 170 struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
 171 {
 172         atomic_inc(&op->op.usage);
 173         return op;
 174 }
 175 
 176 /**
 177  * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
 178  * @op: The retrieval operation affected
 179  *
 180  * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
 181  */
 182 static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
 183 {
 184         fscache_enqueue_operation(&op->op);
 185 }
 186 
 187 /**
 188  * fscache_retrieval_complete - Record (partial) completion of a retrieval
 189  * @op: The retrieval operation affected
 190  * @n_pages: The number of pages to account for
 191  */
 192 static inline void fscache_retrieval_complete(struct fscache_retrieval *op,
 193                                               int n_pages)
 194 {
 195         if (atomic_sub_return_relaxed(n_pages, &op->n_pages) <= 0)
 196                 fscache_op_complete(&op->op, false);
 197 }
 198 
 199 /**
 200  * fscache_put_retrieval - Drop a reference to a retrieval operation
 201  * @op: The retrieval operation affected
 202  *
 203  * Drop a reference to a retrieval operation.
 204  */
 205 static inline void fscache_put_retrieval(struct fscache_retrieval *op)
 206 {
 207         fscache_put_operation(&op->op);
 208 }
 209 
 210 /*
 211  * cached page storage work item
 212  * - used to do three things:
 213  *   - batch writes to the cache
 214  *   - do cache writes asynchronously
 215  *   - defer writes until cache object lookup completion
 216  */
 217 struct fscache_storage {
 218         struct fscache_operation op;
 219         pgoff_t                 store_limit;    /* don't write more than this */
 220 };
 221 
 222 /*
 223  * cache operations
 224  */
 225 struct fscache_cache_ops {
 226         /* name of cache provider */
 227         const char *name;
 228 
 229         /* allocate an object record for a cookie */
 230         struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
 231                                                struct fscache_cookie *cookie);
 232 
 233         /* look up the object for a cookie
 234          * - return -ETIMEDOUT to be requeued
 235          */
 236         int (*lookup_object)(struct fscache_object *object);
 237 
 238         /* finished looking up */
 239         void (*lookup_complete)(struct fscache_object *object);
 240 
 241         /* increment the usage count on this object (may fail if unmounting) */
 242         struct fscache_object *(*grab_object)(struct fscache_object *object,
 243                                               enum fscache_obj_ref_trace why);
 244 
 245         /* pin an object in the cache */
 246         int (*pin_object)(struct fscache_object *object);
 247 
 248         /* unpin an object in the cache */
 249         void (*unpin_object)(struct fscache_object *object);
 250 
 251         /* check the consistency between the backing cache and the FS-Cache
 252          * cookie */
 253         int (*check_consistency)(struct fscache_operation *op);
 254 
 255         /* store the updated auxiliary data on an object */
 256         void (*update_object)(struct fscache_object *object);
 257 
 258         /* Invalidate an object */
 259         void (*invalidate_object)(struct fscache_operation *op);
 260 
 261         /* discard the resources pinned by an object and effect retirement if
 262          * necessary */
 263         void (*drop_object)(struct fscache_object *object);
 264 
 265         /* dispose of a reference to an object */
 266         void (*put_object)(struct fscache_object *object,
 267                            enum fscache_obj_ref_trace why);
 268 
 269         /* sync a cache */
 270         void (*sync_cache)(struct fscache_cache *cache);
 271 
 272         /* notification that the attributes of a non-index object (such as
 273          * i_size) have changed */
 274         int (*attr_changed)(struct fscache_object *object);
 275 
 276         /* reserve space for an object's data and associated metadata */
 277         int (*reserve_space)(struct fscache_object *object, loff_t i_size);
 278 
 279         /* request a backing block for a page be read or allocated in the
 280          * cache */
 281         fscache_page_retrieval_func_t read_or_alloc_page;
 282 
 283         /* request backing blocks for a list of pages be read or allocated in
 284          * the cache */
 285         fscache_pages_retrieval_func_t read_or_alloc_pages;
 286 
 287         /* request a backing block for a page be allocated in the cache so that
 288          * it can be written directly */
 289         fscache_page_retrieval_func_t allocate_page;
 290 
 291         /* request backing blocks for pages be allocated in the cache so that
 292          * they can be written directly */
 293         fscache_pages_retrieval_func_t allocate_pages;
 294 
 295         /* write a page to its backing block in the cache */
 296         int (*write_page)(struct fscache_storage *op, struct page *page);
 297 
 298         /* detach backing block from a page (optional)
 299          * - must release the cookie lock before returning
 300          * - may sleep
 301          */
 302         void (*uncache_page)(struct fscache_object *object,
 303                              struct page *page);
 304 
 305         /* dissociate a cache from all the pages it was backing */
 306         void (*dissociate_pages)(struct fscache_cache *cache);
 307 };
 308 
 309 extern struct fscache_cookie fscache_fsdef_index;
 310 
 311 /*
 312  * Event list for fscache_object::{event_mask,events}
 313  */
 314 enum {
 315         FSCACHE_OBJECT_EV_NEW_CHILD,    /* T if object has a new child */
 316         FSCACHE_OBJECT_EV_PARENT_READY, /* T if object's parent is ready */
 317         FSCACHE_OBJECT_EV_UPDATE,       /* T if object should be updated */
 318         FSCACHE_OBJECT_EV_INVALIDATE,   /* T if cache requested object invalidation */
 319         FSCACHE_OBJECT_EV_CLEARED,      /* T if accessors all gone */
 320         FSCACHE_OBJECT_EV_ERROR,        /* T if fatal error occurred during processing */
 321         FSCACHE_OBJECT_EV_KILL,         /* T if netfs relinquished or cache withdrew object */
 322         NR_FSCACHE_OBJECT_EVENTS
 323 };
 324 
 325 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
 326 
 327 /*
 328  * States for object state machine.
 329  */
 330 struct fscache_transition {
 331         unsigned long events;
 332         const struct fscache_state *transit_to;
 333 };
 334 
 335 struct fscache_state {
 336         char name[24];
 337         char short_name[8];
 338         const struct fscache_state *(*work)(struct fscache_object *object,
 339                                             int event);
 340         const struct fscache_transition transitions[];
 341 };
 342 
 343 /*
 344  * on-disk cache file or index handle
 345  */
 346 struct fscache_object {
 347         const struct fscache_state *state;      /* Object state machine state */
 348         const struct fscache_transition *oob_table; /* OOB state transition table */
 349         int                     debug_id;       /* debugging ID */
 350         int                     n_children;     /* number of child objects */
 351         int                     n_ops;          /* number of extant ops on object */
 352         int                     n_obj_ops;      /* number of object ops outstanding on object */
 353         int                     n_in_progress;  /* number of ops in progress */
 354         int                     n_exclusive;    /* number of exclusive ops queued or in progress */
 355         atomic_t                n_reads;        /* number of read ops in progress */
 356         spinlock_t              lock;           /* state and operations lock */
 357 
 358         unsigned long           lookup_jif;     /* time at which lookup started */
 359         unsigned long           oob_event_mask; /* OOB events this object is interested in */
 360         unsigned long           event_mask;     /* events this object is interested in */
 361         unsigned long           events;         /* events to be processed by this object
 362                                                  * (order is important - using fls) */
 363 
 364         unsigned long           flags;
 365 #define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
 366 #define FSCACHE_OBJECT_PENDING_WRITE    1       /* T if object has pending write */
 367 #define FSCACHE_OBJECT_WAITING          2       /* T if object is waiting on its parent */
 368 #define FSCACHE_OBJECT_IS_LIVE          3       /* T if object is not withdrawn or relinquished */
 369 #define FSCACHE_OBJECT_IS_LOOKED_UP     4       /* T if object has been looked up */
 370 #define FSCACHE_OBJECT_IS_AVAILABLE     5       /* T if object has become active */
 371 #define FSCACHE_OBJECT_RETIRED          6       /* T if object was retired on relinquishment */
 372 #define FSCACHE_OBJECT_KILLED_BY_CACHE  7       /* T if object was killed by the cache */
 373 #define FSCACHE_OBJECT_RUN_AFTER_DEAD   8       /* T if object has been dispatched after death */
 374 
 375         struct list_head        cache_link;     /* link in cache->object_list */
 376         struct hlist_node       cookie_link;    /* link in cookie->backing_objects */
 377         struct fscache_cache    *cache;         /* cache that supplied this object */
 378         struct fscache_cookie   *cookie;        /* netfs's file/index object */
 379         struct fscache_object   *parent;        /* parent object */
 380         struct work_struct      work;           /* attention scheduling record */
 381         struct list_head        dependents;     /* FIFO of dependent objects */
 382         struct list_head        dep_link;       /* link in parent's dependents list */
 383         struct list_head        pending_ops;    /* unstarted operations on this object */
 384 #ifdef CONFIG_FSCACHE_OBJECT_LIST
 385         struct rb_node          objlist_link;   /* link in global object list */
 386 #endif
 387         pgoff_t                 store_limit;    /* current storage limit */
 388         loff_t                  store_limit_l;  /* current storage limit */
 389 };
 390 
 391 extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *,
 392                                 struct fscache_cache *);
 393 extern void fscache_object_destroy(struct fscache_object *);
 394 
 395 extern void fscache_object_lookup_negative(struct fscache_object *object);
 396 extern void fscache_obtained_object(struct fscache_object *object);
 397 
 398 static inline bool fscache_object_is_live(struct fscache_object *object)
 399 {
 400         return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 401 }
 402 
 403 static inline bool fscache_object_is_dying(struct fscache_object *object)
 404 {
 405         return !fscache_object_is_live(object);
 406 }
 407 
 408 static inline bool fscache_object_is_available(struct fscache_object *object)
 409 {
 410         return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 411 }
 412 
 413 static inline bool fscache_cache_is_broken(struct fscache_object *object)
 414 {
 415         return test_bit(FSCACHE_IOERROR, &object->cache->flags);
 416 }
 417 
 418 static inline bool fscache_object_is_active(struct fscache_object *object)
 419 {
 420         return fscache_object_is_available(object) &&
 421                 fscache_object_is_live(object) &&
 422                 !fscache_cache_is_broken(object);
 423 }
 424 
 425 /**
 426  * fscache_object_destroyed - Note destruction of an object in a cache
 427  * @cache: The cache from which the object came
 428  *
 429  * Note the destruction and deallocation of an object record in a cache.
 430  */
 431 static inline void fscache_object_destroyed(struct fscache_cache *cache)
 432 {
 433         if (atomic_dec_and_test(&cache->object_count))
 434                 wake_up_all(&fscache_cache_cleared_wq);
 435 }
 436 
 437 /**
 438  * fscache_object_lookup_error - Note an object encountered an error
 439  * @object: The object on which the error was encountered
 440  *
 441  * Note that an object encountered a fatal error (usually an I/O error) and
 442  * that it should be withdrawn as soon as possible.
 443  */
 444 static inline void fscache_object_lookup_error(struct fscache_object *object)
 445 {
 446         set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
 447 }
 448 
 449 /**
 450  * fscache_set_store_limit - Set the maximum size to be stored in an object
 451  * @object: The object to set the maximum on
 452  * @i_size: The limit to set in bytes
 453  *
 454  * Set the maximum size an object is permitted to reach, implying the highest
 455  * byte that may be written.  Intended to be called by the attr_changed() op.
 456  *
 457  * See Documentation/filesystems/caching/backend-api.txt for a complete
 458  * description.
 459  */
 460 static inline
 461 void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
 462 {
 463         object->store_limit_l = i_size;
 464         object->store_limit = i_size >> PAGE_SHIFT;
 465         if (i_size & ~PAGE_MASK)
 466                 object->store_limit++;
 467 }
 468 
 469 /**
 470  * fscache_end_io - End a retrieval operation on a page
 471  * @op: The FS-Cache operation covering the retrieval
 472  * @page: The page that was to be fetched
 473  * @error: The error code (0 if successful)
 474  *
 475  * Note the end of an operation to retrieve a page, as covered by a particular
 476  * operation record.
 477  */
 478 static inline void fscache_end_io(struct fscache_retrieval *op,
 479                                   struct page *page, int error)
 480 {
 481         op->end_io_func(page, op->context, error);
 482 }
 483 
 484 static inline void __fscache_use_cookie(struct fscache_cookie *cookie)
 485 {
 486         atomic_inc(&cookie->n_active);
 487 }
 488 
 489 /**
 490  * fscache_use_cookie - Request usage of cookie attached to an object
 491  * @object: Object description
 492  * 
 493  * Request usage of the cookie attached to an object.  NULL is returned if the
 494  * relinquishment had reduced the cookie usage count to 0.
 495  */
 496 static inline bool fscache_use_cookie(struct fscache_object *object)
 497 {
 498         struct fscache_cookie *cookie = object->cookie;
 499         return atomic_inc_not_zero(&cookie->n_active) != 0;
 500 }
 501 
 502 static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie)
 503 {
 504         return atomic_dec_and_test(&cookie->n_active);
 505 }
 506 
 507 static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie)
 508 {
 509         wake_up_var(&cookie->n_active);
 510 }
 511 
 512 /**
 513  * fscache_unuse_cookie - Cease usage of cookie attached to an object
 514  * @object: Object description
 515  * 
 516  * Cease usage of the cookie attached to an object.  When the users count
 517  * reaches zero then the cookie relinquishment will be permitted to proceed.
 518  */
 519 static inline void fscache_unuse_cookie(struct fscache_object *object)
 520 {
 521         struct fscache_cookie *cookie = object->cookie;
 522         if (__fscache_unuse_cookie(cookie))
 523                 __fscache_wake_unused_cookie(cookie);
 524 }
 525 
 526 /*
 527  * out-of-line cache backend functions
 528  */
 529 extern __printf(3, 4)
 530 void fscache_init_cache(struct fscache_cache *cache,
 531                         const struct fscache_cache_ops *ops,
 532                         const char *idfmt, ...);
 533 
 534 extern int fscache_add_cache(struct fscache_cache *cache,
 535                              struct fscache_object *fsdef,
 536                              const char *tagname);
 537 extern void fscache_withdraw_cache(struct fscache_cache *cache);
 538 
 539 extern void fscache_io_error(struct fscache_cache *cache);
 540 
 541 extern void fscache_mark_page_cached(struct fscache_retrieval *op,
 542                                      struct page *page);
 543 
 544 extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
 545                                       struct pagevec *pagevec);
 546 
 547 extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
 548 
 549 extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 550                                                const void *data,
 551                                                uint16_t datalen,
 552                                                loff_t object_size);
 553 
 554 extern void fscache_object_retrying_stale(struct fscache_object *object);
 555 
 556 enum fscache_why_object_killed {
 557         FSCACHE_OBJECT_IS_STALE,
 558         FSCACHE_OBJECT_NO_SPACE,
 559         FSCACHE_OBJECT_WAS_RETIRED,
 560         FSCACHE_OBJECT_WAS_CULLED,
 561 };
 562 extern void fscache_object_mark_killed(struct fscache_object *object,
 563                                        enum fscache_why_object_killed why);
 564 
 565 #endif /* _LINUX_FSCACHE_CACHE_H */