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.rst
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[]; /* 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73 #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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
fscache_get_retrieval(struct fscache_retrieval * op)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 */
fscache_enqueue_retrieval(struct fscache_retrieval * op)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 */
fscache_retrieval_complete(struct fscache_retrieval * op,int n_pages)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 */
fscache_put_retrieval(struct fscache_retrieval * op)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
fscache_object_is_live(struct fscache_object * object)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
fscache_object_is_dying(struct fscache_object * object)403 static inline bool fscache_object_is_dying(struct fscache_object *object)
404 {
405 return !fscache_object_is_live(object);
406 }
407
fscache_object_is_available(struct fscache_object * object)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
fscache_cache_is_broken(struct fscache_object * object)413 static inline bool fscache_cache_is_broken(struct fscache_object *object)
414 {
415 return test_bit(FSCACHE_IOERROR, &object->cache->flags);
416 }
417
fscache_object_is_active(struct fscache_object * object)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 */
fscache_object_destroyed(struct fscache_cache * cache)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 */
fscache_object_lookup_error(struct fscache_object * object)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.rst for a complete
458 * description.
459 */
460 static inline
fscache_set_store_limit(struct fscache_object * object,loff_t i_size)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 */
fscache_end_io(struct fscache_retrieval * op,struct page * page,int error)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
__fscache_use_cookie(struct fscache_cookie * cookie)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 */
fscache_use_cookie(struct fscache_object * object)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
__fscache_unuse_cookie(struct fscache_cookie * cookie)502 static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie)
503 {
504 return atomic_dec_and_test(&cookie->n_active);
505 }
506
__fscache_wake_unused_cookie(struct fscache_cookie * cookie)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 */
fscache_unuse_cookie(struct fscache_object * object)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 */
566