/* 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  #define FSCACHE_CACHE_WITHDRAWN	1	/* cache has been withdrawn */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);
  
  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_DEAD		6	/* op is now dead */

  #define FSCACHE_OP_DEC_READ_CNT	7	/* decrement object->n_reads on destruction */
  #define FSCACHE_OP_KEEP_FLAGS	0xc0	/* flags to keep when repurposing an op */

  
  	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;

  #ifdef CONFIG_WORKQUEUE_DEBUGFS
  	struct work_struct put_work;	/* work to delay operation put */

  	const char *name;		/* operation name */
  	const char *state;		/* operation state */
  #define fscache_set_op_name(OP, N)	do { (OP)->name  = (N); } while(0)
  #define fscache_set_op_state(OP, S)	do { (OP)->state = (S); } while(0)
  #else
  #define fscache_set_op_name(OP, N)	do { } while(0)
  #define fscache_set_op_state(OP, S)	do { } while(0)
  #endif

  };
  
  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_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->debug_id = atomic_inc_return(&fscache_op_debug_id);

  	op->processor = processor;

  	op->release = release;
  	INIT_LIST_HEAD(&op->pend_link);

  	fscache_set_op_state(op, "Init");

  }

  /*
   * 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
  	 * - 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);
  
  	/* 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;

  	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_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 */

  		FSCACHE_OBJECT__NSTATES

  	} 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 */

  	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		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 */

  #define FSCACHE_OBJECT_EVENTS_MASK	0x7f	/* mask of all events*/

  
  	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 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 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)

  #define fscache_object_is_dead(obj)				\
  	(test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&	\
  	 (obj)->state >= FSCACHE_OBJECT_DYING)

  extern void fscache_object_work_func(struct work_struct *work);

  
  /**
   * 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);

  	INIT_WORK(&object->work, fscache_object_work_func);

  	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->store_limit_l = 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);

  #ifdef CONFIG_FSCACHE_OBJECT_LIST
  extern void fscache_object_destroy(struct fscache_object *object);
  #else
  #define fscache_object_destroy(object) do {} while(0)
  #endif

  /**
   * 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);
  }
  
  /*
   * 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 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 */