/* General filesystem caching backing cache interface * * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * NOTE!!! See: * * Documentation/filesystems/caching/backend-api.txt * * for a description of the cache backend interface declared here. */ #ifndef _LINUX_FSCACHE_CACHE_H #define _LINUX_FSCACHE_CACHE_H #include <linux/fscache.h> #include <linux/sched.h> #include <linux/slow-work.h> #define NR_MAXCACHES BITS_PER_LONG struct fscache_cache; struct fscache_cache_ops; struct fscache_object; struct fscache_operation; /* * cache tag definition */ struct fscache_cache_tag { struct list_head link; struct fscache_cache *cache; /* cache referred to by this tag */ unsigned long flags; #define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */ atomic_t usage; char name[0]; /* tag name */ }; /* * cache definition */ struct fscache_cache { const struct fscache_cache_ops *ops; struct fscache_cache_tag *tag; /* tag representing this cache */ struct kobject *kobj; /* system representation of this cache */ struct list_head link; /* link in list of caches */ size_t max_index_size; /* maximum size of index data */ char identifier[36]; /* cache label */ /* node management */ struct work_struct op_gc; /* operation garbage collector */ struct list_head object_list; /* list of data/index objects */ struct list_head op_gc_list; /* list of ops to be deleted */ spinlock_t object_list_lock; spinlock_t op_gc_list_lock; atomic_t object_count; /* no. of live objects in this cache */ struct fscache_object *fsdef; /* object for the fsdef index */ unsigned long flags; #define FSCACHE_IOERROR 0 /* cache stopped on I/O error */ #define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */ }; extern wait_queue_head_t fscache_cache_cleared_wq; /* * operation to be applied to a cache object * - retrieval initiation operations are done in the context of the process * that issued them, and not in an async thread pool */ typedef void (*fscache_operation_release_t)(struct fscache_operation *op); typedef void (*fscache_operation_processor_t)(struct fscache_operation *op); struct fscache_operation { union { struct work_struct fast_work; /* record for fast ops */ struct slow_work slow_work; /* record for (very) slow ops */ }; struct list_head pend_link; /* link in object->pending_ops */ struct fscache_object *object; /* object to be operated upon */ unsigned long flags; #define FSCACHE_OP_TYPE 0x000f /* operation type */ #define FSCACHE_OP_FAST 0x0001 /* - fast op, processor may not sleep for disk */ #define FSCACHE_OP_SLOW 0x0002 /* - (very) slow op, processor may sleep for disk */ #define FSCACHE_OP_MYTHREAD 0x0003 /* - processing is done be issuing thread, not pool */ #define FSCACHE_OP_WAITING 4 /* cleared when op is woken */ #define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */ #define FSCACHE_OP_DEAD 6 /* op is now dead */ atomic_t usage; unsigned debug_id; /* debugging ID */ /* operation processor callback * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform * the op in a non-pool thread */ fscache_operation_processor_t processor; /* operation releaser */ fscache_operation_release_t release; }; extern atomic_t fscache_op_debug_id; extern const struct slow_work_ops fscache_op_slow_work_ops; extern void fscache_enqueue_operation(struct fscache_operation *); extern void fscache_put_operation(struct fscache_operation *); /** * fscache_operation_init - Do basic initialisation of an operation * @op: The operation to initialise * @release: The release function to assign * * Do basic initialisation of an operation. The caller must still set flags, * object, either fast_work or slow_work if necessary, and processor if needed. */ static inline void fscache_operation_init(struct fscache_operation *op, fscache_operation_release_t release) { atomic_set(&op->usage, 1); op->debug_id = atomic_inc_return(&fscache_op_debug_id); op->release = release; INIT_LIST_HEAD(&op->pend_link); } /** * fscache_operation_init_slow - Do additional initialisation of a slow op * @op: The operation to initialise * @processor: The processor function to assign * * Do additional initialisation of an operation as required for slow work. */ static inline void fscache_operation_init_slow(struct fscache_operation *op, fscache_operation_processor_t processor) { op->processor = processor; slow_work_init(&op->slow_work, &fscache_op_slow_work_ops); } /* * data read operation */ struct fscache_retrieval { struct fscache_operation op; struct address_space *mapping; /* netfs pages */ fscache_rw_complete_t end_io_func; /* function to call on I/O completion */ void *context; /* netfs read context (pinned) */ struct list_head to_do; /* list of things to be done by the backend */ unsigned long start_time; /* time at which retrieval started */ }; typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op, struct page *page, gfp_t gfp); typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op, struct list_head *pages, unsigned *nr_pages, gfp_t gfp); /** * fscache_get_retrieval - Get an extra reference on a retrieval operation * @op: The retrieval operation to get a reference on * * Get an extra reference on a retrieval operation. */ static inline struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op) { atomic_inc(&op->op.usage); return op; } /** * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing * @op: The retrieval operation affected * * Enqueue a retrieval operation for processing by the FS-Cache thread pool. */ static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op) { fscache_enqueue_operation(&op->op); } /** * fscache_put_retrieval - Drop a reference to a retrieval operation * @op: The retrieval operation affected * * Drop a reference to a retrieval operation. */ static inline void fscache_put_retrieval(struct fscache_retrieval *op) { fscache_put_operation(&op->op); } /* * cached page storage work item * - used to do three things: * - batch writes to the cache * - do cache writes asynchronously * - defer writes until cache object lookup completion */ struct fscache_storage { struct fscache_operation op; pgoff_t store_limit; /* don't write more than this */ }; /* * cache operations */ struct fscache_cache_ops { /* name of cache provider */ const char *name; /* allocate an object record for a cookie */ struct fscache_object *(*alloc_object)(struct fscache_cache *cache, struct fscache_cookie *cookie); /* look up the object for a cookie */ void (*lookup_object)(struct fscache_object *object); /* finished looking up */ void (*lookup_complete)(struct fscache_object *object); /* increment the usage count on this object (may fail if unmounting) */ struct fscache_object *(*grab_object)(struct fscache_object *object); /* pin an object in the cache */ int (*pin_object)(struct fscache_object *object); /* unpin an object in the cache */ void (*unpin_object)(struct fscache_object *object); /* store the updated auxilliary data on an object */ void (*update_object)(struct fscache_object *object); /* discard the resources pinned by an object and effect retirement if * necessary */ void (*drop_object)(struct fscache_object *object); /* dispose of a reference to an object */ void (*put_object)(struct fscache_object *object); /* sync a cache */ void (*sync_cache)(struct fscache_cache *cache); /* notification that the attributes of a non-index object (such as * i_size) have changed */ int (*attr_changed)(struct fscache_object *object); /* reserve space for an object's data and associated metadata */ int (*reserve_space)(struct fscache_object *object, loff_t i_size); /* request a backing block for a page be read or allocated in the * cache */ fscache_page_retrieval_func_t read_or_alloc_page; /* request backing blocks for a list of pages be read or allocated in * the cache */ fscache_pages_retrieval_func_t read_or_alloc_pages; /* request a backing block for a page be allocated in the cache so that * it can be written directly */ fscache_page_retrieval_func_t allocate_page; /* request backing blocks for pages be allocated in the cache so that * they can be written directly */ fscache_pages_retrieval_func_t allocate_pages; /* write a page to its backing block in the cache */ int (*write_page)(struct fscache_storage *op, struct page *page); /* detach backing block from a page (optional) * - must release the cookie lock before returning * - may sleep */ void (*uncache_page)(struct fscache_object *object, struct page *page); /* dissociate a cache from all the pages it was backing */ void (*dissociate_pages)(struct fscache_cache *cache); }; /* * data file or index object cookie * - a file will only appear in one cache * - a request to cache a file may or may not be honoured, subject to * constraints such as disk space * - indices are created on disk just-in-time */ struct fscache_cookie { atomic_t usage; /* number of users of this cookie */ atomic_t n_children; /* number of children of this cookie */ spinlock_t lock; struct hlist_head backing_objects; /* object(s) backing this file/index */ const struct fscache_cookie_def *def; /* definition */ struct fscache_cookie *parent; /* parent of this entry */ void *netfs_data; /* back pointer to netfs */ struct radix_tree_root stores; /* pages to be stored on this cookie */ #define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */ unsigned long flags; #define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */ #define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */ #define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */ #define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */ #define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */ #define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */ }; extern struct fscache_cookie fscache_fsdef_index; /* * on-disk cache file or index handle */ struct fscache_object { enum fscache_object_state { FSCACHE_OBJECT_INIT, /* object in initial unbound state */ FSCACHE_OBJECT_LOOKING_UP, /* looking up object */ FSCACHE_OBJECT_CREATING, /* creating object */ /* active states */ FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */ FSCACHE_OBJECT_ACTIVE, /* object is usable */ FSCACHE_OBJECT_UPDATING, /* object is updating */ /* terminal states */ FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */ FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */ FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */ FSCACHE_OBJECT_RELEASING, /* releasing object */ FSCACHE_OBJECT_RECYCLING, /* retiring object */ FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */ FSCACHE_OBJECT_DEAD, /* object is now dead */ } state; int debug_id; /* debugging ID */ int n_children; /* number of child objects */ int n_ops; /* number of ops outstanding on object */ int n_obj_ops; /* number of object ops outstanding on object */ int n_in_progress; /* number of ops in progress */ int n_exclusive; /* number of exclusive ops queued */ spinlock_t lock; /* state and operations lock */ unsigned long lookup_jif; /* time at which lookup started */ unsigned long event_mask; /* events this object is interested in */ unsigned long events; /* events to be processed by this object * (order is important - using fls) */ #define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */ #define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */ #define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */ #define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */ #define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */ #define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */ #define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */ unsigned long flags; #define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */ #define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */ #define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */ struct list_head cache_link; /* link in cache->object_list */ struct hlist_node cookie_link; /* link in cookie->backing_objects */ struct fscache_cache *cache; /* cache that supplied this object */ struct fscache_cookie *cookie; /* netfs's file/index object */ struct fscache_object *parent; /* parent object */ struct slow_work work; /* attention scheduling record */ struct list_head dependents; /* FIFO of dependent objects */ struct list_head dep_link; /* link in parent's dependents list */ struct list_head pending_ops; /* unstarted operations on this object */ pgoff_t store_limit; /* current storage limit */ }; extern const char *fscache_object_states[]; #define fscache_object_is_active(obj) \ (!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \ (obj)->state >= FSCACHE_OBJECT_AVAILABLE && \ (obj)->state < FSCACHE_OBJECT_DYING) extern const struct slow_work_ops fscache_object_slow_work_ops; /** * fscache_object_init - Initialise a cache object description * @object: Object description * * Initialise a cache object description to its basic values. * * See Documentation/filesystems/caching/backend-api.txt for a complete * description. */ static inline void fscache_object_init(struct fscache_object *object, struct fscache_cookie *cookie, struct fscache_cache *cache) { atomic_inc(&cache->object_count); object->state = FSCACHE_OBJECT_INIT; spin_lock_init(&object->lock); INIT_LIST_HEAD(&object->cache_link); INIT_HLIST_NODE(&object->cookie_link); vslow_work_init(&object->work, &fscache_object_slow_work_ops); INIT_LIST_HEAD(&object->dependents); INIT_LIST_HEAD(&object->dep_link); INIT_LIST_HEAD(&object->pending_ops); object->n_children = 0; object->n_ops = object->n_in_progress = object->n_exclusive = 0; object->events = object->event_mask = 0; object->flags = 0; object->store_limit = 0; object->cache = cache; object->cookie = cookie; object->parent = NULL; } extern void fscache_object_lookup_negative(struct fscache_object *object); extern void fscache_obtained_object(struct fscache_object *object); /** * fscache_object_destroyed - Note destruction of an object in a cache * @cache: The cache from which the object came * * Note the destruction and deallocation of an object record in a cache. */ static inline void fscache_object_destroyed(struct fscache_cache *cache) { if (atomic_dec_and_test(&cache->object_count)) wake_up_all(&fscache_cache_cleared_wq); } /** * fscache_object_lookup_error - Note an object encountered an error * @object: The object on which the error was encountered * * Note that an object encountered a fatal error (usually an I/O error) and * that it should be withdrawn as soon as possible. */ static inline void fscache_object_lookup_error(struct fscache_object *object) { set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events); } /** * fscache_set_store_limit - Set the maximum size to be stored in an object * @object: The object to set the maximum on * @i_size: The limit to set in bytes * * Set the maximum size an object is permitted to reach, implying the highest * byte that may be written. Intended to be called by the attr_changed() op. * * See Documentation/filesystems/caching/backend-api.txt for a complete * description. */ static inline void fscache_set_store_limit(struct fscache_object *object, loff_t i_size) { object->store_limit = i_size >> PAGE_SHIFT; if (i_size & ~PAGE_MASK) object->store_limit++; } /** * fscache_end_io - End a retrieval operation on a page * @op: The FS-Cache operation covering the retrieval * @page: The page that was to be fetched * @error: The error code (0 if successful) * * Note the end of an operation to retrieve a page, as covered by a particular * operation record. */ static inline void fscache_end_io(struct fscache_retrieval *op, struct page *page, int error) { op->end_io_func(page, op->context, error); } /* * out-of-line cache backend functions */ extern void fscache_init_cache(struct fscache_cache *cache, const struct fscache_cache_ops *ops, const char *idfmt, ...) __attribute__ ((format (printf, 3, 4))); extern int fscache_add_cache(struct fscache_cache *cache, struct fscache_object *fsdef, const char *tagname); extern void fscache_withdraw_cache(struct fscache_cache *cache); extern void fscache_io_error(struct fscache_cache *cache); extern void fscache_mark_pages_cached(struct fscache_retrieval *op, struct pagevec *pagevec); extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object, const void *data, uint16_t datalen); #endif /* _LINUX_FSCACHE_CACHE_H */