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Diffstat (limited to 'include/linux/fscache-cache.h')
| -rw-r--r-- | include/linux/fscache-cache.h | 505 |
1 files changed, 505 insertions, 0 deletions
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h new file mode 100644 index 00000000000..84d3532dd3e --- /dev/null +++ b/include/linux/fscache-cache.h @@ -0,0 +1,505 @@ +/* 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 */ |