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Diffstat (limited to 'include/linux/fscache.h')
| -rw-r--r-- | include/linux/fscache.h | 548 |
1 files changed, 548 insertions, 0 deletions
diff --git a/include/linux/fscache.h b/include/linux/fscache.h new file mode 100644 index 00000000000..feb3b0e0af4 --- /dev/null +++ b/include/linux/fscache.h @@ -0,0 +1,548 @@ +/* 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 + */ + +/** + * 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) +{ + 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) +{ +} + +/** + * 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) +{ + 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) +{ +} + +/** + * 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) +{ + 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) +{ +} + +/** + * 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) +{ +} + +/** + * 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) +{ + 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) +{ + 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) +{ + 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) +{ + 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) +{ + 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) +{ +} + +/** + * 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) +{ + 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) +{ +} + +#endif /* _LINUX_FSCACHE_H */ |