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TOMOYO Linux Cross Reference
Linux/include/linux/fscache-cache.h

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

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