/* 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/workqueue.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#define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */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);
enum fscache_operation_state {
FSCACHE_OP_ST_BLANK, /* Op is not yet submitted */
FSCACHE_OP_ST_INITIALISED, /* Op is initialised */
FSCACHE_OP_ST_PENDING, /* Op is blocked from running */
FSCACHE_OP_ST_IN_PROGRESS, /* Op is in progress */
FSCACHE_OP_ST_COMPLETE, /* Op is complete */
FSCACHE_OP_ST_CANCELLED, /* Op has been cancelled */
FSCACHE_OP_ST_DEAD /* Op is now dead */
};
struct fscache_operation {
struct work_struct work; /* record for async 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_ASYNC 0x0001 /* - async op, processor may sleep for disk */
#define FSCACHE_OP_MYTHREAD 0x0002 /* - 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_DEC_READ_CNT 6 /* decrement object->n_reads on destruction */
#define FSCACHE_OP_UNUSE_COOKIE 7 /* call fscache_unuse_cookie() on completion */
#define FSCACHE_OP_KEEP_FLAGS 0x00f0 /* flags to keep when repurposing an op */
enum fscache_operation_state state;
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 void fscache_op_work_func(struct work_struct *work);
extern void fscache_enqueue_operation(struct fscache_operation *);
extern void fscache_op_complete(struct fscache_operation *, bool);
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 and processor if needed.
*/
static inline void fscache_operation_init(struct fscache_operation *op,
fscache_operation_processor_t processor,
fscache_operation_release_t release)
{
INIT_WORK(&op->work, fscache_op_work_func);
atomic_set(&op->usage, 1);
op->state = FSCACHE_OP_ST_INITIALISED;
op->debug_id = atomic_inc_return(&fscache_op_debug_id);
op->processor = processor;
op->release = release;
INIT_LIST_HEAD(&op->pend_link);
}
/*
* 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 */
atomic_t n_pages; /* number of pages to be retrieved */
};
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_retrieval_complete - Record (partial) completion of a retrieval
* @op: The retrieval operation affected
* @n_pages: The number of pages to account for
*/
static inline void fscache_retrieval_complete(struct fscache_retrieval *op,
int n_pages)
{
atomic_sub(n_pages, &op->n_pages);
if (atomic_read(&op->n_pages) <= 0)
fscache_op_complete(&op->op, true);
}
/**
* 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
* - return -ETIMEDOUT to be requeued
*/
int (*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);
/* check the consistency between the backing cache and the FS-Cache
* cookie */
bool (*check_consistency)(struct fscache_operation *op);
/* store the updated auxiliary data on an object */
void (*update_object)(struct fscache_object *object);
/* Invalidate an object */
void (*invalidate_object)(struct fscache_operation *op);
/* 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 */
atomic_t n_active; /* number of active users of netfs ptrs */
spinlock_t lock;
spinlock_t stores_lock; /* lock on page store tree */
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 */
#define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */
unsigned long flags;
#define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
#define FSCACHE_COOKIE_NO_DATA_YET 1 /* T if new object with no cached data yet */
#define FSCACHE_COOKIE_UNAVAILABLE 2 /* T if cookie is unavailable (error, etc) */
#define FSCACHE_COOKIE_INVALIDATING 3 /* T if cookie is being invalidated */
#define FSCACHE_COOKIE_RELINQUISHED 4 /* T if cookie has been relinquished */
#define FSCACHE_COOKIE_RETIRED 5 /* T if cookie was retired */
};
extern struct fscache_cookie fscache_fsdef_index;
/*
* Event list for fscache_object::{event_mask,events}
*/
enum {
FSCACHE_OBJECT_EV_NEW_CHILD, /* T if object has a new child */
FSCACHE_OBJECT_EV_PARENT_READY, /* T if object's parent is ready */
FSCACHE_OBJECT_EV_UPDATE, /* T if object should be updated */
FSCACHE_OBJECT_EV_INVALIDATE, /* T if cache requested object invalidation */
FSCACHE_OBJECT_EV_CLEARED, /* T if accessors all gone */
FSCACHE_OBJECT_EV_ERROR, /* T if fatal error occurred during processing */
FSCACHE_OBJECT_EV_KILL, /* T if netfs relinquished or cache withdrew object */
NR_FSCACHE_OBJECT_EVENTS
};
#define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
/*
* States for object state machine.
*/
struct fscache_transition {
unsigned long events;
const struct fscache_state *transit_to;
};
struct fscache_state {
char name[24];
char short_name[8];
const struct fscache_state *(*work)(struct fscache_object *object,
int event);
const struct fscache_transition transitions[];
};
/*
* on-disk cache file or index handle
*/
struct fscache_object {
const struct fscache_state *state; /* Object state machine state */
const struct fscache_transition *oob_table; /* OOB state transition table */
int debug_id; /* debugging ID */
int n_children; /* number of child objects */
int n_ops; /* number of extant ops 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 or in progress */
atomic_t n_reads; /* number of read ops in progress */
spinlock_t lock; /* state and operations lock */
unsigned long lookup_jif; /* time at which lookup started */
unsigned long oob_event_mask; /* OOB events this object is interested in */
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) */
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 */
#define FSCACHE_OBJECT_IS_LIVE 3 /* T if object is not withdrawn or relinquished */
#define FSCACHE_OBJECT_IS_LOOKED_UP 4 /* T if object has been looked up */
#define FSCACHE_OBJECT_IS_AVAILABLE 5 /* T if object has become active */
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 work_struct 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 */
#ifdef CONFIG_FSCACHE_OBJECT_LIST
struct rb_node objlist_link; /* link in global object list */
#endif
pgoff_t store_limit; /* current storage limit */
loff_t store_limit_l; /* current storage limit */
};
extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *,
struct fscache_cache *);
extern void fscache_object_destroy(struct fscache_object *);
extern void fscache_object_lookup_negative(struct fscache_object *object);
extern void fscache_obtained_object(struct fscache_object *object);
static inline bool fscache_object_is_live(struct fscache_object *object)
{
return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
}
static inline bool fscache_object_is_dying(struct fscache_object *object)
{
return !fscache_object_is_live(object);
}
static inline bool fscache_object_is_available(struct fscache_object *object)
{
return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
}
static inline bool fscache_object_is_active(struct fscache_object *object)
{
return fscache_object_is_available(object) &&
fscache_object_is_live(object) &&
!test_bit(FSCACHE_IOERROR, &object->cache->flags);
}
static inline bool fscache_object_is_dead(struct fscache_object *object)
{
return fscache_object_is_dying(object) &&
test_bit(FSCACHE_IOERROR, &object->cache->flags);
}
/**
* 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_l = 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);
}
/**
* fscache_use_cookie - Request usage of cookie attached to an object
* @object: Object description
*
* Request usage of the cookie attached to an object. NULL is returned if the
* relinquishment had reduced the cookie usage count to 0.
*/
static inline bool fscache_use_cookie(struct fscache_object *object)
{
struct fscache_cookie *cookie = object->cookie;
return atomic_inc_not_zero(&cookie->n_active) != 0;
}
/**
* fscache_unuse_cookie - Cease usage of cookie attached to an object
* @object: Object description
*
* Cease usage of the cookie attached to an object. When the users count
* reaches zero then the cookie relinquishment will be permitted to proceed.
*/
static inline void fscache_unuse_cookie(struct fscache_object *object)
{
struct fscache_cookie *cookie = object->cookie;
if (atomic_dec_and_test(&cookie->n_active))
wake_up_atomic_t(&cookie->n_active);
}
/*
* out-of-line cache backend functions
*/
extern __printf(3, 4)
void fscache_init_cache(struct fscache_cache *cache,
const struct fscache_cache_ops *ops,
const char *idfmt, ...);
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_page_cached(struct fscache_retrieval *op,
struct page *page);
extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
struct pagevec *pagevec);
extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
const void *data,
uint16_t datalen);
#endif /* _LINUX_FSCACHE_CACHE_H */
