include/linux/fscache.h - kernel/msm-4.9 - Gitiles

 /* General filesystem caching 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/netfs-api.txt
  *
  * for a description of the network filesystem interface declared here.
  */

 #ifndef _LINUX_FSCACHE_H
 #define _LINUX_FSCACHE_H

 #include <linux/fs.h>
 #include <linux/list.h>
 #include <linux/pagemap.h>
 #include <linux/pagevec.h>

 #if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
 #define fscache_available() (1)
 #define fscache_cookie_valid(cookie) (cookie)
 #else
 #define fscache_available() (0)
 #define fscache_cookie_valid(cookie) (0)
 #endif


 /*
  * overload PG_private_2 to give us PG_fscache - this is used to indicate that
  * a page is currently backed by a local disk cache
  */
 #define PageFsCache(page)		PagePrivate2((page))
 #define SetPageFsCache(page)		SetPagePrivate2((page))
 #define ClearPageFsCache(page)		ClearPagePrivate2((page))
 #define TestSetPageFsCache(page)	TestSetPagePrivate2((page))
 #define TestClearPageFsCache(page)	TestClearPagePrivate2((page))

 /* pattern used to fill dead space in an index entry */
 #define FSCACHE_INDEX_DEADFILL_PATTERN 0x79

 struct pagevec;
 struct fscache_cache_tag;
 struct fscache_cookie;
 struct fscache_netfs;

 typedef void (*fscache_rw_complete_t)(struct page *page,
 				      void *context,
 				      int error);

 /* result of index entry consultation */
 enum fscache_checkaux {
 	FSCACHE_CHECKAUX_OKAY,		/* entry okay as is */
 	FSCACHE_CHECKAUX_NEEDS_UPDATE,	/* entry requires update */
 	FSCACHE_CHECKAUX_OBSOLETE,	/* entry requires deletion */
 };

 /*
  * fscache cookie definition
  */
 struct fscache_cookie_def {
 	/* name of cookie type */
 	char name[16];

 	/* cookie type */
 	uint8_t type;
 #define FSCACHE_COOKIE_TYPE_INDEX	0
 #define FSCACHE_COOKIE_TYPE_DATAFILE	1

 	/* select the cache into which to insert an entry in this index
 	 * - optional
 	 * - should return a cache identifier or NULL to cause the cache to be
 	 *   inherited from the parent if possible or the first cache picked
 	 *   for a non-index file if not
 	 */
 	struct fscache_cache_tag *(*select_cache)(
 		const void *parent_netfs_data,
 		const void *cookie_netfs_data);

 	/* get an index key
 	 * - should store the key data in the buffer
 	 * - should return the amount of amount stored
 	 * - not permitted to return an error
 	 * - the netfs data from the cookie being used as the source is
 	 *   presented
 	 */
 	uint16_t (*get_key)(const void *cookie_netfs_data,
 			    void *buffer,
 			    uint16_t bufmax);

 	/* get certain file attributes from the netfs data
 	 * - this function can be absent for an index
 	 * - not permitted to return an error
 	 * - the netfs data from the cookie being used as the source is
 	 *   presented
 	 */
 	void (*get_attr)(const void *cookie_netfs_data, uint64_t *size);

 	/* get the auxilliary data from netfs data
 	 * - this function can be absent if the index carries no state data
 	 * - should store the auxilliary data in the buffer
 	 * - should return the amount of amount stored
 	 * - not permitted to return an error
 	 * - the netfs data from the cookie being used as the source is
 	 *   presented
 	 */
 	uint16_t (*get_aux)(const void *cookie_netfs_data,
 			    void *buffer,
 			    uint16_t bufmax);

 	/* consult the netfs about the state of an object
 	 * - this function can be absent if the index carries no state data
 	 * - the netfs data from the cookie being used as the target is
 	 *   presented, as is the auxilliary data
 	 */
 	enum fscache_checkaux (*check_aux)(void *cookie_netfs_data,
 					   const void *data,
 					   uint16_t datalen);

 	/* get an extra reference on a read context
 	 * - this function can be absent if the completion function doesn't
 	 *   require a context
 	 */
 	void (*get_context)(void *cookie_netfs_data, void *context);

 	/* release an extra reference on a read context
 	 * - this function can be absent if the completion function doesn't
 	 *   require a context
 	 */
 	void (*put_context)(void *cookie_netfs_data, void *context);

 	/* indicate pages that now have cache metadata retained
 	 * - this function should mark the specified pages as now being cached
 	 * - the pages will have been marked with PG_fscache before this is
 	 *   called, so this is optional
 	 */
 	void (*mark_pages_cached)(void *cookie_netfs_data,
 				  struct address_space *mapping,
 				  struct pagevec *cached_pvec);

 	/* indicate the cookie is no longer cached
 	 * - this function is called when the backing store currently caching
 	 *   a cookie is removed
 	 * - the netfs should use this to clean up any markers indicating
 	 *   cached pages
 	 * - this is mandatory for any object that may have data
 	 */
 	void (*now_uncached)(void *cookie_netfs_data);
 };

 /*
  * fscache cached network filesystem type
  * - name, version and ops must be filled in before registration
  * - all other fields will be set during registration
  */
 struct fscache_netfs {
 	uint32_t			version;	/* indexing version */
 	const char			*name;		/* filesystem name */
 	struct fscache_cookie		*primary_index;
 	struct list_head		link;		/* internal link */
 };

 /*
  * slow-path functions for when there is actually caching available, and the
  * netfs does actually have a valid token
  * - these are not to be called directly
  * - these are undefined symbols when FS-Cache is not configured and the
  *   optimiser takes care of not using them
  */
 extern int __fscache_register_netfs(struct fscache_netfs *);
 extern void __fscache_unregister_netfs(struct fscache_netfs *);
 extern struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *);
 extern void __fscache_release_cache_tag(struct fscache_cache_tag *);

 extern struct fscache_cookie *__fscache_acquire_cookie(
 	struct fscache_cookie *,
 	const struct fscache_cookie_def *,
 	void *);
 extern void __fscache_relinquish_cookie(struct fscache_cookie *, int);
 extern void __fscache_update_cookie(struct fscache_cookie *);
 extern int __fscache_attr_changed(struct fscache_cookie *);
 extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
 					struct page *,
 					fscache_rw_complete_t,
 					void *,
 					gfp_t);
 extern int __fscache_read_or_alloc_pages(struct fscache_cookie *,
 					 struct address_space *,
 					 struct list_head *,
 					 unsigned *,
 					 fscache_rw_complete_t,
 					 void *,
 					 gfp_t);
 extern int __fscache_alloc_page(struct fscache_cookie *, struct page *, gfp_t);
 extern int __fscache_write_page(struct fscache_cookie *, struct page *, gfp_t);
 extern void __fscache_uncache_page(struct fscache_cookie *, struct page *);
 extern bool __fscache_check_page_write(struct fscache_cookie *, struct page *);
 extern void __fscache_wait_on_page_write(struct fscache_cookie *, struct page *);

 /**
  * fscache_register_netfs - Register a filesystem as desiring caching services
  * @netfs: The description of the filesystem
  *
  * Register a filesystem as desiring caching services if they're available.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 int fscache_register_netfs(struct fscache_netfs *netfs)
 {
 	if (fscache_available())
 		return __fscache_register_netfs(netfs);
 	else
 		return 0;
 }

 /**
  * fscache_unregister_netfs - Indicate that a filesystem no longer desires
  * caching services
  * @netfs: The description of the filesystem
  *
  * Indicate that a filesystem no longer desires caching services for the
  * moment.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 void fscache_unregister_netfs(struct fscache_netfs *netfs)
 {
 	if (fscache_available())
 		__fscache_unregister_netfs(netfs);
 }

 /**
  * fscache_lookup_cache_tag - Look up a cache tag
  * @name: The name of the tag to search for
  *
  * Acquire a specific cache referral tag that can be used to select a specific
  * cache in which to cache an index.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name)
 {
 	if (fscache_available())
 		return __fscache_lookup_cache_tag(name);
 	else
 		return NULL;
 }

 /**
  * fscache_release_cache_tag - Release a cache tag
  * @tag: The tag to release
  *
  * Release a reference to a cache referral tag previously looked up.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 void fscache_release_cache_tag(struct fscache_cache_tag *tag)
 {
 	if (fscache_available())
 		__fscache_release_cache_tag(tag);
 }

 /**
  * fscache_acquire_cookie - Acquire a cookie to represent a cache object
  * @parent: The cookie that's to be the parent of this one
  * @def: A description of the cache object, including callback operations
  * @netfs_data: An arbitrary piece of data to be kept in the cookie to
  * represent the cache object to the netfs
  *
  * This function is used to inform FS-Cache about part of an index hierarchy
  * that can be used to locate files.  This is done by requesting a cookie for
  * each index in the path to the file.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 struct fscache_cookie *fscache_acquire_cookie(
 	struct fscache_cookie *parent,
 	const struct fscache_cookie_def *def,
 	void *netfs_data)
 {
 	if (fscache_cookie_valid(parent))
 		return __fscache_acquire_cookie(parent, def, netfs_data);
 	else
 		return NULL;
 }

 /**
  * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
  * it
  * @cookie: The cookie being returned
  * @retire: True if the cache object the cookie represents is to be discarded
  *
  * This function returns a cookie to the cache, forcibly discarding the
  * associated cache object if retire is set to true.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 void fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 {
 	if (fscache_cookie_valid(cookie))
 		__fscache_relinquish_cookie(cookie, retire);
 }

 /**
  * fscache_update_cookie - Request that a cache object be updated
  * @cookie: The cookie representing the cache object
  *
  * Request an update of the index data for the cache object associated with the
  * cookie.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 void fscache_update_cookie(struct fscache_cookie *cookie)
 {
 	if (fscache_cookie_valid(cookie))
 		__fscache_update_cookie(cookie);
 }

 /**
  * fscache_pin_cookie - Pin a data-storage cache object in its cache
  * @cookie: The cookie representing the cache object
  *
  * Permit data-storage cache objects to be pinned in the cache.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 int fscache_pin_cookie(struct fscache_cookie *cookie)
 {
 	return -ENOBUFS;
 }

 /**
  * fscache_pin_cookie - Unpin a data-storage cache object in its cache
  * @cookie: The cookie representing the cache object
  *
  * Permit data-storage cache objects to be unpinned from the cache.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 void fscache_unpin_cookie(struct fscache_cookie *cookie)
 {
 }

 /**
  * fscache_attr_changed - Notify cache that an object's attributes changed
  * @cookie: The cookie representing the cache object
  *
  * Send a notification to the cache indicating that an object's attributes have
  * changed.  This includes the data size.  These attributes will be obtained
  * through the get_attr() cookie definition op.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 int fscache_attr_changed(struct fscache_cookie *cookie)
 {
 	if (fscache_cookie_valid(cookie))
 		return __fscache_attr_changed(cookie);
 	else
 		return -ENOBUFS;
 }

 /**
  * fscache_reserve_space - Reserve data space for a cached object
  * @cookie: The cookie representing the cache object
  * @i_size: The amount of space to be reserved
  *
  * Reserve an amount of space in the cache for the cache object attached to a
  * cookie so that a write to that object within the space can always be
  * honoured.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
 {
 	return -ENOBUFS;
 }

 /**
  * fscache_read_or_alloc_page - Read a page from the cache or allocate a block
  * in which to store it
  * @cookie: The cookie representing the cache object
  * @page: The netfs page to fill if possible
  * @end_io_func: The callback to invoke when and if the page is filled
  * @context: An arbitrary piece of data to pass on to end_io_func()
  * @gfp: The conditions under which memory allocation should be made
  *
  * Read a page from the cache, or if that's not possible make a potential
  * one-block reservation in the cache into which the page may be stored once
  * fetched from the server.
  *
  * If the page is not backed by the cache object, or if it there's some reason
  * it can't be, -ENOBUFS will be returned and nothing more will be done for
  * that page.
  *
  * Else, if that page is backed by the cache, a read will be initiated directly
  * to the netfs's page and 0 will be returned by this function.  The
  * end_io_func() callback will be invoked when the operation terminates on a
  * completion or failure.  Note that the callback may be invoked before the
  * return.
  *
  * Else, if the page is unbacked, -ENODATA is returned and a block may have
  * been allocated in the cache.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 			       struct page *page,
 			       fscache_rw_complete_t end_io_func,
 			       void *context,
 			       gfp_t gfp)
 {
 	if (fscache_cookie_valid(cookie))
 		return __fscache_read_or_alloc_page(cookie, page, end_io_func,
 						    context, gfp);
 	else
 		return -ENOBUFS;
 }

 /**
  * fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
  * blocks in which to store them
  * @cookie: The cookie representing the cache object
  * @mapping: The netfs inode mapping to which the pages will be attached
  * @pages: A list of potential netfs pages to be filled
  * @end_io_func: The callback to invoke when and if each page is filled
  * @context: An arbitrary piece of data to pass on to end_io_func()
  * @gfp: The conditions under which memory allocation should be made
  *
  * Read a set of pages from the cache, or if that's not possible, attempt to
  * make a potential one-block reservation for each page in the cache into which
  * that page may be stored once fetched from the server.
  *
  * If some pages are not backed by the cache object, or if it there's some
  * reason they can't be, -ENOBUFS will be returned and nothing more will be
  * done for that pages.
  *
  * Else, if some of the pages are backed by the cache, a read will be initiated
  * directly to the netfs's page and 0 will be returned by this function.  The
  * end_io_func() callback will be invoked when the operation terminates on a
  * completion or failure.  Note that the callback may be invoked before the
  * return.
  *
  * Else, if a page is unbacked, -ENODATA is returned and a block may have
  * been allocated in the cache.
  *
  * Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
  * regard to different pages, the return values are prioritised in that order.
  * Any pages submitted for reading are removed from the pages list.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 				struct address_space *mapping,
 				struct list_head *pages,
 				unsigned *nr_pages,
 				fscache_rw_complete_t end_io_func,
 				void *context,
 				gfp_t gfp)
 {
 	if (fscache_cookie_valid(cookie))
 		return __fscache_read_or_alloc_pages(cookie, mapping, pages,
 						     nr_pages, end_io_func,
 						     context, gfp);
 	else
 		return -ENOBUFS;
 }

 /**
  * fscache_alloc_page - Allocate a block in which to store a page
  * @cookie: The cookie representing the cache object
  * @page: The netfs page to allocate a page for
  * @gfp: The conditions under which memory allocation should be made
  *
  * Request Allocation a block in the cache in which to store a netfs page
  * without retrieving any contents from the cache.
  *
  * If the page is not backed by a file then -ENOBUFS will be returned and
  * nothing more will be done, and no reservation will be made.
  *
  * Else, a block will be allocated if one wasn't already, and 0 will be
  * returned
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 int fscache_alloc_page(struct fscache_cookie *cookie,
 		       struct page *page,
 		       gfp_t gfp)
 {
 	if (fscache_cookie_valid(cookie))
 		return __fscache_alloc_page(cookie, page, gfp);
 	else
 		return -ENOBUFS;
 }

 /**
  * fscache_write_page - Request storage of a page in the cache
  * @cookie: The cookie representing the cache object
  * @page: The netfs page to store
  * @gfp: The conditions under which memory allocation should be made
  *
  * Request the contents of the netfs page be written into the cache.  This
  * request may be ignored if no cache block is currently allocated, in which
  * case it will return -ENOBUFS.
  *
  * If a cache block was already allocated, a write will be initiated and 0 will
  * be returned.  The PG_fscache_write page bit is set immediately and will then
  * be cleared at the completion of the write to indicate the success or failure
  * of the operation.  Note that the completion may happen before the return.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 int fscache_write_page(struct fscache_cookie *cookie,
 		       struct page *page,
 		       gfp_t gfp)
 {
 	if (fscache_cookie_valid(cookie))
 		return __fscache_write_page(cookie, page, gfp);
 	else
 		return -ENOBUFS;
 }

 /**
  * fscache_uncache_page - Indicate that caching is no longer required on a page
  * @cookie: The cookie representing the cache object
  * @page: The netfs page that was being cached.
  *
  * Tell the cache that we no longer want a page to be cached and that it should
  * remove any knowledge of the netfs page it may have.
  *
  * Note that this cannot cancel any outstanding I/O operations between this
  * page and the cache.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 void fscache_uncache_page(struct fscache_cookie *cookie,
 			  struct page *page)
 {
 	if (fscache_cookie_valid(cookie))
 		__fscache_uncache_page(cookie, page);
 }

 /**
  * fscache_check_page_write - Ask if a page is being writing to the cache
  * @cookie: The cookie representing the cache object
  * @page: The netfs page that is being cached.
  *
  * Ask the cache if a page is being written to the cache.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 bool fscache_check_page_write(struct fscache_cookie *cookie,
 			      struct page *page)
 {
 	if (fscache_cookie_valid(cookie))
 		return __fscache_check_page_write(cookie, page);
 	return false;
 }

 /**
  * fscache_wait_on_page_write - Wait for a page to complete writing to the cache
  * @cookie: The cookie representing the cache object
  * @page: The netfs page that is being cached.
  *
  * Ask the cache to wake us up when a page is no longer being written to the
  * cache.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
 void fscache_wait_on_page_write(struct fscache_cookie *cookie,
 				struct page *page)
 {
 	if (fscache_cookie_valid(cookie))
 		__fscache_wait_on_page_write(cookie, page);
 }

 #endif /* _LINUX_FSCACHE_H */
	/* General filesystem caching 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/netfs-api.txt
	*
	* for a description of the network filesystem interface declared here.
	*/

	#ifndef _LINUX_FSCACHE_H
	#define _LINUX_FSCACHE_H

	#include <linux/fs.h>
	#include <linux/list.h>
	#include <linux/pagemap.h>
	#include <linux/pagevec.h>

	#if defined(CONFIG_FSCACHE) \|\| defined(CONFIG_FSCACHE_MODULE)
	#define fscache_available() (1)
	#define fscache_cookie_valid(cookie) (cookie)
	#else
	#define fscache_available() (0)
	#define fscache_cookie_valid(cookie) (0)
	#endif


	/*
	* overload PG_private_2 to give us PG_fscache - this is used to indicate that
	* a page is currently backed by a local disk cache
	*/
	#define PageFsCache(page) PagePrivate2((page))
	#define SetPageFsCache(page) SetPagePrivate2((page))
	#define ClearPageFsCache(page) ClearPagePrivate2((page))
	#define TestSetPageFsCache(page) TestSetPagePrivate2((page))
	#define TestClearPageFsCache(page) TestClearPagePrivate2((page))

	/* pattern used to fill dead space in an index entry */
	#define FSCACHE_INDEX_DEADFILL_PATTERN 0x79

	struct pagevec;
	struct fscache_cache_tag;
	struct fscache_cookie;
	struct fscache_netfs;

	typedef void (fscache_rw_complete_t)(struct page page,
	void *context,
	int error);

	/* result of index entry consultation */
	enum fscache_checkaux {
	FSCACHE_CHECKAUX_OKAY, /* entry okay as is */
	FSCACHE_CHECKAUX_NEEDS_UPDATE, /* entry requires update */
	FSCACHE_CHECKAUX_OBSOLETE, /* entry requires deletion */
	};

	/*
	* fscache cookie definition
	*/
	struct fscache_cookie_def {
	/* name of cookie type */
	char name[16];

	/* cookie type */
	uint8_t type;
	#define FSCACHE_COOKIE_TYPE_INDEX 0
	#define FSCACHE_COOKIE_TYPE_DATAFILE 1

	/* select the cache into which to insert an entry in this index
	* - optional
	* - should return a cache identifier or NULL to cause the cache to be
	* inherited from the parent if possible or the first cache picked
	* for a non-index file if not
	*/
	struct fscache_cache_tag (select_cache)(
	const void *parent_netfs_data,
	const void *cookie_netfs_data);

	/* get an index key
	* - should store the key data in the buffer
	* - should return the amount of amount stored
	* - not permitted to return an error
	* - the netfs data from the cookie being used as the source is
	* presented
	*/
	uint16_t (get_key)(const void cookie_netfs_data,
	void *buffer,
	uint16_t bufmax);

	/* get certain file attributes from the netfs data
	* - this function can be absent for an index
	* - not permitted to return an error
	* - the netfs data from the cookie being used as the source is
	* presented
	*/
	void (get_attr)(const void cookie_netfs_data, uint64_t *size);

	/* get the auxilliary data from netfs data
	* - this function can be absent if the index carries no state data
	* - should store the auxilliary data in the buffer
	* - should return the amount of amount stored
	* - not permitted to return an error
	* - the netfs data from the cookie being used as the source is
	* presented
	*/
	uint16_t (get_aux)(const void cookie_netfs_data,
	void *buffer,
	uint16_t bufmax);

	/* consult the netfs about the state of an object
	* - this function can be absent if the index carries no state data
	* - the netfs data from the cookie being used as the target is
	* presented, as is the auxilliary data
	*/
	enum fscache_checkaux (check_aux)(void cookie_netfs_data,
	const void *data,
	uint16_t datalen);

	/* get an extra reference on a read context
	* - this function can be absent if the completion function doesn't
	* require a context
	*/
	void (get_context)(void cookie_netfs_data, void *context);

	/* release an extra reference on a read context
	* - this function can be absent if the completion function doesn't
	* require a context
	*/
	void (put_context)(void cookie_netfs_data, void *context);

	/* indicate pages that now have cache metadata retained
	* - this function should mark the specified pages as now being cached
	* - the pages will have been marked with PG_fscache before this is
	* called, so this is optional
	*/
	void (mark_pages_cached)(void cookie_netfs_data,
	struct address_space *mapping,
	struct pagevec *cached_pvec);

	/* indicate the cookie is no longer cached
	* - this function is called when the backing store currently caching
	* a cookie is removed
	* - the netfs should use this to clean up any markers indicating
	* cached pages
	* - this is mandatory for any object that may have data
	*/
	void (now_uncached)(void cookie_netfs_data);
	};

	/*
	* fscache cached network filesystem type
	* - name, version and ops must be filled in before registration
	* - all other fields will be set during registration
	*/
	struct fscache_netfs {
	uint32_t version; /* indexing version */
	const char name; / filesystem name */
	struct fscache_cookie *primary_index;
	struct list_head link; /* internal link */
	};

	/*
	* slow-path functions for when there is actually caching available, and the
	* netfs does actually have a valid token
	* - these are not to be called directly
	* - these are undefined symbols when FS-Cache is not configured and the
	* optimiser takes care of not using them
	*/
	extern int __fscache_register_netfs(struct fscache_netfs *);
	extern void __fscache_unregister_netfs(struct fscache_netfs *);
	extern struct fscache_cache_tag __fscache_lookup_cache_tag(const char );
	extern void __fscache_release_cache_tag(struct fscache_cache_tag *);

	extern struct fscache_cookie *__fscache_acquire_cookie(
	struct fscache_cookie *,
	const struct fscache_cookie_def *,
	void *);
	extern void __fscache_relinquish_cookie(struct fscache_cookie *, int);
	extern void __fscache_update_cookie(struct fscache_cookie *);
	extern int __fscache_attr_changed(struct fscache_cookie *);
	extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
	struct page *,
	fscache_rw_complete_t,
	void *,
	gfp_t);
	extern int __fscache_read_or_alloc_pages(struct fscache_cookie *,
	struct address_space *,
	struct list_head *,
	unsigned *,
	fscache_rw_complete_t,
	void *,
	gfp_t);
	extern int __fscache_alloc_page(struct fscache_cookie , struct page , gfp_t);
	extern int __fscache_write_page(struct fscache_cookie , struct page , gfp_t);
	extern void __fscache_uncache_page(struct fscache_cookie , struct page );
	extern bool __fscache_check_page_write(struct fscache_cookie , struct page );
	extern void __fscache_wait_on_page_write(struct fscache_cookie , struct page );

	/**
	* fscache_register_netfs - Register a filesystem as desiring caching services
	* @netfs: The description of the filesystem
	*
	* Register a filesystem as desiring caching services if they're available.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	int fscache_register_netfs(struct fscache_netfs *netfs)
	{
	if (fscache_available())
	return __fscache_register_netfs(netfs);
	else
	return 0;
	}

	/**
	* fscache_unregister_netfs - Indicate that a filesystem no longer desires
	* caching services
	* @netfs: The description of the filesystem
	*
	* Indicate that a filesystem no longer desires caching services for the
	* moment.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	void fscache_unregister_netfs(struct fscache_netfs *netfs)
	{
	if (fscache_available())
	__fscache_unregister_netfs(netfs);
	}

	/**
	* fscache_lookup_cache_tag - Look up a cache tag
	* @name: The name of the tag to search for
	*
	* Acquire a specific cache referral tag that can be used to select a specific
	* cache in which to cache an index.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	struct fscache_cache_tag fscache_lookup_cache_tag(const char name)
	{
	if (fscache_available())
	return __fscache_lookup_cache_tag(name);
	else
	return NULL;
	}

	/**
	* fscache_release_cache_tag - Release a cache tag
	* @tag: The tag to release
	*
	* Release a reference to a cache referral tag previously looked up.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	void fscache_release_cache_tag(struct fscache_cache_tag *tag)
	{
	if (fscache_available())
	__fscache_release_cache_tag(tag);
	}

	/**
	* fscache_acquire_cookie - Acquire a cookie to represent a cache object
	* @parent: The cookie that's to be the parent of this one
	* @def: A description of the cache object, including callback operations
	* @netfs_data: An arbitrary piece of data to be kept in the cookie to
	* represent the cache object to the netfs
	*
	* This function is used to inform FS-Cache about part of an index hierarchy
	* that can be used to locate files. This is done by requesting a cookie for
	* each index in the path to the file.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	struct fscache_cookie *fscache_acquire_cookie(
	struct fscache_cookie *parent,
	const struct fscache_cookie_def *def,
	void *netfs_data)
	{
	if (fscache_cookie_valid(parent))
	return __fscache_acquire_cookie(parent, def, netfs_data);
	else
	return NULL;
	}

	/**
	* fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
	* it
	* @cookie: The cookie being returned
	* @retire: True if the cache object the cookie represents is to be discarded
	*
	* This function returns a cookie to the cache, forcibly discarding the
	* associated cache object if retire is set to true.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	void fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
	{
	if (fscache_cookie_valid(cookie))
	__fscache_relinquish_cookie(cookie, retire);
	}

	/**
	* fscache_update_cookie - Request that a cache object be updated
	* @cookie: The cookie representing the cache object
	*
	* Request an update of the index data for the cache object associated with the
	* cookie.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	void fscache_update_cookie(struct fscache_cookie *cookie)
	{
	if (fscache_cookie_valid(cookie))
	__fscache_update_cookie(cookie);
	}

	/**
	* fscache_pin_cookie - Pin a data-storage cache object in its cache
	* @cookie: The cookie representing the cache object
	*
	* Permit data-storage cache objects to be pinned in the cache.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	int fscache_pin_cookie(struct fscache_cookie *cookie)
	{
	return -ENOBUFS;
	}

	/**
	* fscache_pin_cookie - Unpin a data-storage cache object in its cache
	* @cookie: The cookie representing the cache object
	*
	* Permit data-storage cache objects to be unpinned from the cache.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	void fscache_unpin_cookie(struct fscache_cookie *cookie)
	{
	}

	/**
	* fscache_attr_changed - Notify cache that an object's attributes changed
	* @cookie: The cookie representing the cache object
	*
	* Send a notification to the cache indicating that an object's attributes have
	* changed. This includes the data size. These attributes will be obtained
	* through the get_attr() cookie definition op.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	int fscache_attr_changed(struct fscache_cookie *cookie)
	{
	if (fscache_cookie_valid(cookie))
	return __fscache_attr_changed(cookie);
	else
	return -ENOBUFS;
	}

	/**
	* fscache_reserve_space - Reserve data space for a cached object
	* @cookie: The cookie representing the cache object
	* @i_size: The amount of space to be reserved
	*
	* Reserve an amount of space in the cache for the cache object attached to a
	* cookie so that a write to that object within the space can always be
	* honoured.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
	{
	return -ENOBUFS;
	}

	/**
	* fscache_read_or_alloc_page - Read a page from the cache or allocate a block
	* in which to store it
	* @cookie: The cookie representing the cache object
	* @page: The netfs page to fill if possible
	* @end_io_func: The callback to invoke when and if the page is filled
	* @context: An arbitrary piece of data to pass on to end_io_func()
	* @gfp: The conditions under which memory allocation should be made
	*
	* Read a page from the cache, or if that's not possible make a potential
	* one-block reservation in the cache into which the page may be stored once
	* fetched from the server.
	*
	* If the page is not backed by the cache object, or if it there's some reason
	* it can't be, -ENOBUFS will be returned and nothing more will be done for
	* that page.
	*
	* Else, if that page is backed by the cache, a read will be initiated directly
	* to the netfs's page and 0 will be returned by this function. The
	* end_io_func() callback will be invoked when the operation terminates on a
	* completion or failure. Note that the callback may be invoked before the
	* return.
	*
	* Else, if the page is unbacked, -ENODATA is returned and a block may have
	* been allocated in the cache.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
	struct page *page,
	fscache_rw_complete_t end_io_func,
	void *context,
	gfp_t gfp)
	{
	if (fscache_cookie_valid(cookie))
	return __fscache_read_or_alloc_page(cookie, page, end_io_func,
	context, gfp);
	else
	return -ENOBUFS;
	}

	/**
	* fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
	* blocks in which to store them
	* @cookie: The cookie representing the cache object
	* @mapping: The netfs inode mapping to which the pages will be attached
	* @pages: A list of potential netfs pages to be filled
	* @end_io_func: The callback to invoke when and if each page is filled
	* @context: An arbitrary piece of data to pass on to end_io_func()
	* @gfp: The conditions under which memory allocation should be made
	*
	* Read a set of pages from the cache, or if that's not possible, attempt to
	* make a potential one-block reservation for each page in the cache into which
	* that page may be stored once fetched from the server.
	*
	* If some pages are not backed by the cache object, or if it there's some
	* reason they can't be, -ENOBUFS will be returned and nothing more will be
	* done for that pages.
	*
	* Else, if some of the pages are backed by the cache, a read will be initiated
	* directly to the netfs's page and 0 will be returned by this function. The
	* end_io_func() callback will be invoked when the operation terminates on a
	* completion or failure. Note that the callback may be invoked before the
	* return.
	*
	* Else, if a page is unbacked, -ENODATA is returned and a block may have
	* been allocated in the cache.
	*
	* Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
	* regard to different pages, the return values are prioritised in that order.
	* Any pages submitted for reading are removed from the pages list.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
	struct address_space *mapping,
	struct list_head *pages,
	unsigned *nr_pages,
	fscache_rw_complete_t end_io_func,
	void *context,
	gfp_t gfp)
	{
	if (fscache_cookie_valid(cookie))
	return __fscache_read_or_alloc_pages(cookie, mapping, pages,
	nr_pages, end_io_func,
	context, gfp);
	else
	return -ENOBUFS;
	}

	/**
	* fscache_alloc_page - Allocate a block in which to store a page
	* @cookie: The cookie representing the cache object
	* @page: The netfs page to allocate a page for
	* @gfp: The conditions under which memory allocation should be made
	*
	* Request Allocation a block in the cache in which to store a netfs page
	* without retrieving any contents from the cache.
	*
	* If the page is not backed by a file then -ENOBUFS will be returned and
	* nothing more will be done, and no reservation will be made.
	*
	* Else, a block will be allocated if one wasn't already, and 0 will be
	* returned
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	int fscache_alloc_page(struct fscache_cookie *cookie,
	struct page *page,
	gfp_t gfp)
	{
	if (fscache_cookie_valid(cookie))
	return __fscache_alloc_page(cookie, page, gfp);
	else
	return -ENOBUFS;
	}

	/**
	* fscache_write_page - Request storage of a page in the cache
	* @cookie: The cookie representing the cache object
	* @page: The netfs page to store
	* @gfp: The conditions under which memory allocation should be made
	*
	* Request the contents of the netfs page be written into the cache. This
	* request may be ignored if no cache block is currently allocated, in which
	* case it will return -ENOBUFS.
	*
	* If a cache block was already allocated, a write will be initiated and 0 will
	* be returned. The PG_fscache_write page bit is set immediately and will then
	* be cleared at the completion of the write to indicate the success or failure
	* of the operation. Note that the completion may happen before the return.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	int fscache_write_page(struct fscache_cookie *cookie,
	struct page *page,
	gfp_t gfp)
	{
	if (fscache_cookie_valid(cookie))
	return __fscache_write_page(cookie, page, gfp);
	else
	return -ENOBUFS;
	}

	/**
	* fscache_uncache_page - Indicate that caching is no longer required on a page
	* @cookie: The cookie representing the cache object
	* @page: The netfs page that was being cached.
	*
	* Tell the cache that we no longer want a page to be cached and that it should
	* remove any knowledge of the netfs page it may have.
	*
	* Note that this cannot cancel any outstanding I/O operations between this
	* page and the cache.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	void fscache_uncache_page(struct fscache_cookie *cookie,
	struct page *page)
	{
	if (fscache_cookie_valid(cookie))
	__fscache_uncache_page(cookie, page);
	}

	/**
	* fscache_check_page_write - Ask if a page is being writing to the cache
	* @cookie: The cookie representing the cache object
	* @page: The netfs page that is being cached.
	*
	* Ask the cache if a page is being written to the cache.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	bool fscache_check_page_write(struct fscache_cookie *cookie,
	struct page *page)
	{
	if (fscache_cookie_valid(cookie))
	return __fscache_check_page_write(cookie, page);
	return false;
	}

	/**
	* fscache_wait_on_page_write - Wait for a page to complete writing to the cache
	* @cookie: The cookie representing the cache object
	* @page: The netfs page that is being cached.
	*
	* Ask the cache to wake us up when a page is no longer being written to the
	* cache.
	*
	* See Documentation/filesystems/caching/netfs-api.txt for a complete
	* description.
	*/
	static inline
	void fscache_wait_on_page_write(struct fscache_cookie *cookie,
	struct page *page)
	{
	if (fscache_cookie_valid(cookie))
	__fscache_wait_on_page_write(cookie, page);
	}

	#endif /* _LINUX_FSCACHE_H */