646 lines
21 KiB
C
646 lines
21 KiB
C
/* General filesystem caching interface
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*
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* Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* NOTE!!! See:
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*
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* Documentation/filesystems/caching/netfs-api.txt
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*
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* for a description of the network filesystem interface declared here.
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*/
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#ifndef _LINUX_FSCACHE_H
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#define _LINUX_FSCACHE_H
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#include <linux/fs.h>
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#include <linux/list.h>
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#include <linux/pagemap.h>
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#include <linux/pagevec.h>
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#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
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#define fscache_available() (1)
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#define fscache_cookie_valid(cookie) (cookie)
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#else
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#define fscache_available() (0)
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#define fscache_cookie_valid(cookie) (0)
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#endif
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/*
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* overload PG_private_2 to give us PG_fscache - this is used to indicate that
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* a page is currently backed by a local disk cache
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*/
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#define PageFsCache(page) PagePrivate2((page))
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#define SetPageFsCache(page) SetPagePrivate2((page))
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#define ClearPageFsCache(page) ClearPagePrivate2((page))
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#define TestSetPageFsCache(page) TestSetPagePrivate2((page))
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#define TestClearPageFsCache(page) TestClearPagePrivate2((page))
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/* pattern used to fill dead space in an index entry */
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#define FSCACHE_INDEX_DEADFILL_PATTERN 0x79
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struct pagevec;
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struct fscache_cache_tag;
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struct fscache_cookie;
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struct fscache_netfs;
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typedef void (*fscache_rw_complete_t)(struct page *page,
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void *context,
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int error);
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/* result of index entry consultation */
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enum fscache_checkaux {
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FSCACHE_CHECKAUX_OKAY, /* entry okay as is */
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FSCACHE_CHECKAUX_NEEDS_UPDATE, /* entry requires update */
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FSCACHE_CHECKAUX_OBSOLETE, /* entry requires deletion */
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};
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/*
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* fscache cookie definition
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*/
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struct fscache_cookie_def {
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/* name of cookie type */
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char name[16];
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/* cookie type */
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uint8_t type;
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#define FSCACHE_COOKIE_TYPE_INDEX 0
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#define FSCACHE_COOKIE_TYPE_DATAFILE 1
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/* select the cache into which to insert an entry in this index
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* - optional
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* - should return a cache identifier or NULL to cause the cache to be
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* inherited from the parent if possible or the first cache picked
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* for a non-index file if not
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*/
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struct fscache_cache_tag *(*select_cache)(
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const void *parent_netfs_data,
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const void *cookie_netfs_data);
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/* get an index key
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* - should store the key data in the buffer
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* - should return the amount of amount stored
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* - not permitted to return an error
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* - the netfs data from the cookie being used as the source is
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* presented
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*/
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uint16_t (*get_key)(const void *cookie_netfs_data,
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void *buffer,
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uint16_t bufmax);
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/* get certain file attributes from the netfs data
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* - this function can be absent for an index
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* - not permitted to return an error
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* - the netfs data from the cookie being used as the source is
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* presented
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*/
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void (*get_attr)(const void *cookie_netfs_data, uint64_t *size);
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/* get the auxilliary data from netfs data
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* - this function can be absent if the index carries no state data
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* - should store the auxilliary data in the buffer
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* - should return the amount of amount stored
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* - not permitted to return an error
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* - the netfs data from the cookie being used as the source is
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* presented
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*/
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uint16_t (*get_aux)(const void *cookie_netfs_data,
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void *buffer,
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uint16_t bufmax);
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/* consult the netfs about the state of an object
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* - this function can be absent if the index carries no state data
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* - the netfs data from the cookie being used as the target is
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* presented, as is the auxilliary data
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*/
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enum fscache_checkaux (*check_aux)(void *cookie_netfs_data,
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const void *data,
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uint16_t datalen);
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/* get an extra reference on a read context
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* - this function can be absent if the completion function doesn't
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* require a context
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*/
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void (*get_context)(void *cookie_netfs_data, void *context);
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/* release an extra reference on a read context
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* - this function can be absent if the completion function doesn't
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* require a context
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*/
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void (*put_context)(void *cookie_netfs_data, void *context);
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/* indicate pages that now have cache metadata retained
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* - this function should mark the specified pages as now being cached
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* - the pages will have been marked with PG_fscache before this is
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* called, so this is optional
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*/
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void (*mark_pages_cached)(void *cookie_netfs_data,
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struct address_space *mapping,
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struct pagevec *cached_pvec);
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/* indicate the cookie is no longer cached
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* - this function is called when the backing store currently caching
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* a cookie is removed
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* - the netfs should use this to clean up any markers indicating
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* cached pages
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* - this is mandatory for any object that may have data
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*/
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void (*now_uncached)(void *cookie_netfs_data);
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};
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/*
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* fscache cached network filesystem type
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* - name, version and ops must be filled in before registration
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* - all other fields will be set during registration
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*/
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struct fscache_netfs {
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uint32_t version; /* indexing version */
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const char *name; /* filesystem name */
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struct fscache_cookie *primary_index;
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struct list_head link; /* internal link */
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};
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/*
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* slow-path functions for when there is actually caching available, and the
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* netfs does actually have a valid token
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* - these are not to be called directly
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* - these are undefined symbols when FS-Cache is not configured and the
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* optimiser takes care of not using them
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*/
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extern int __fscache_register_netfs(struct fscache_netfs *);
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extern void __fscache_unregister_netfs(struct fscache_netfs *);
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extern struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *);
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extern void __fscache_release_cache_tag(struct fscache_cache_tag *);
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extern struct fscache_cookie *__fscache_acquire_cookie(
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struct fscache_cookie *,
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const struct fscache_cookie_def *,
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void *);
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extern void __fscache_relinquish_cookie(struct fscache_cookie *, int);
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extern void __fscache_update_cookie(struct fscache_cookie *);
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extern int __fscache_attr_changed(struct fscache_cookie *);
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extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
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struct page *,
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fscache_rw_complete_t,
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void *,
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gfp_t);
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extern int __fscache_read_or_alloc_pages(struct fscache_cookie *,
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struct address_space *,
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struct list_head *,
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unsigned *,
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fscache_rw_complete_t,
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void *,
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gfp_t);
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extern int __fscache_alloc_page(struct fscache_cookie *, struct page *, gfp_t);
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extern int __fscache_write_page(struct fscache_cookie *, struct page *, gfp_t);
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extern void __fscache_uncache_page(struct fscache_cookie *, struct page *);
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extern bool __fscache_check_page_write(struct fscache_cookie *, struct page *);
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extern void __fscache_wait_on_page_write(struct fscache_cookie *, struct page *);
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extern bool __fscache_maybe_release_page(struct fscache_cookie *, struct page *,
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gfp_t);
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/**
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* fscache_register_netfs - Register a filesystem as desiring caching services
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* @netfs: The description of the filesystem
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*
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* Register a filesystem as desiring caching services if they're available.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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int fscache_register_netfs(struct fscache_netfs *netfs)
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{
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if (fscache_available())
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return __fscache_register_netfs(netfs);
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else
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return 0;
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}
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/**
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* fscache_unregister_netfs - Indicate that a filesystem no longer desires
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* caching services
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* @netfs: The description of the filesystem
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*
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* Indicate that a filesystem no longer desires caching services for the
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* moment.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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void fscache_unregister_netfs(struct fscache_netfs *netfs)
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{
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if (fscache_available())
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__fscache_unregister_netfs(netfs);
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}
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/**
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* fscache_lookup_cache_tag - Look up a cache tag
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* @name: The name of the tag to search for
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*
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* Acquire a specific cache referral tag that can be used to select a specific
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* cache in which to cache an index.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name)
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{
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if (fscache_available())
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return __fscache_lookup_cache_tag(name);
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else
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return NULL;
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}
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/**
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* fscache_release_cache_tag - Release a cache tag
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* @tag: The tag to release
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*
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* Release a reference to a cache referral tag previously looked up.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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void fscache_release_cache_tag(struct fscache_cache_tag *tag)
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{
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if (fscache_available())
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__fscache_release_cache_tag(tag);
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}
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/**
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* fscache_acquire_cookie - Acquire a cookie to represent a cache object
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* @parent: The cookie that's to be the parent of this one
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* @def: A description of the cache object, including callback operations
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* @netfs_data: An arbitrary piece of data to be kept in the cookie to
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* represent the cache object to the netfs
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*
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* This function is used to inform FS-Cache about part of an index hierarchy
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* that can be used to locate files. This is done by requesting a cookie for
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* each index in the path to the file.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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struct fscache_cookie *fscache_acquire_cookie(
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struct fscache_cookie *parent,
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const struct fscache_cookie_def *def,
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void *netfs_data)
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{
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if (fscache_cookie_valid(parent))
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return __fscache_acquire_cookie(parent, def, netfs_data);
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else
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return NULL;
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}
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/**
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* fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
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* it
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* @cookie: The cookie being returned
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* @retire: True if the cache object the cookie represents is to be discarded
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*
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* This function returns a cookie to the cache, forcibly discarding the
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* associated cache object if retire is set to true.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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void fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
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{
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if (fscache_cookie_valid(cookie))
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__fscache_relinquish_cookie(cookie, retire);
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}
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/**
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* fscache_update_cookie - Request that a cache object be updated
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* @cookie: The cookie representing the cache object
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*
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* Request an update of the index data for the cache object associated with the
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* cookie.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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void fscache_update_cookie(struct fscache_cookie *cookie)
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{
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if (fscache_cookie_valid(cookie))
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__fscache_update_cookie(cookie);
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}
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/**
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* fscache_pin_cookie - Pin a data-storage cache object in its cache
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* @cookie: The cookie representing the cache object
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*
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* Permit data-storage cache objects to be pinned in the cache.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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int fscache_pin_cookie(struct fscache_cookie *cookie)
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{
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return -ENOBUFS;
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}
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/**
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* fscache_pin_cookie - Unpin a data-storage cache object in its cache
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* @cookie: The cookie representing the cache object
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*
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* Permit data-storage cache objects to be unpinned from the cache.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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void fscache_unpin_cookie(struct fscache_cookie *cookie)
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{
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}
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/**
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* fscache_attr_changed - Notify cache that an object's attributes changed
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* @cookie: The cookie representing the cache object
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*
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* Send a notification to the cache indicating that an object's attributes have
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* changed. This includes the data size. These attributes will be obtained
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* through the get_attr() cookie definition op.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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int fscache_attr_changed(struct fscache_cookie *cookie)
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{
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if (fscache_cookie_valid(cookie))
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return __fscache_attr_changed(cookie);
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else
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return -ENOBUFS;
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}
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/**
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* fscache_reserve_space - Reserve data space for a cached object
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* @cookie: The cookie representing the cache object
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* @i_size: The amount of space to be reserved
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*
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* Reserve an amount of space in the cache for the cache object attached to a
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* cookie so that a write to that object within the space can always be
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* honoured.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
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{
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return -ENOBUFS;
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}
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/**
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* fscache_read_or_alloc_page - Read a page from the cache or allocate a block
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* in which to store it
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* @cookie: The cookie representing the cache object
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* @page: The netfs page to fill if possible
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* @end_io_func: The callback to invoke when and if the page is filled
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* @context: An arbitrary piece of data to pass on to end_io_func()
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* @gfp: The conditions under which memory allocation should be made
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*
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* Read a page from the cache, or if that's not possible make a potential
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* one-block reservation in the cache into which the page may be stored once
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* fetched from the server.
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*
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* If the page is not backed by the cache object, or if it there's some reason
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* it can't be, -ENOBUFS will be returned and nothing more will be done for
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* that page.
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*
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* Else, if that page is backed by the cache, a read will be initiated directly
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* to the netfs's page and 0 will be returned by this function. The
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* end_io_func() callback will be invoked when the operation terminates on a
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* completion or failure. Note that the callback may be invoked before the
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* return.
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*
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* Else, if the page is unbacked, -ENODATA is returned and a block may have
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* been allocated in the cache.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
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struct page *page,
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fscache_rw_complete_t end_io_func,
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void *context,
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gfp_t gfp)
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{
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if (fscache_cookie_valid(cookie))
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return __fscache_read_or_alloc_page(cookie, page, end_io_func,
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context, gfp);
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else
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return -ENOBUFS;
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}
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/**
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* fscache_read_or_alloc_pages - Read pages from the cache and/or allocate
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* blocks in which to store them
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* @cookie: The cookie representing the cache object
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* @mapping: The netfs inode mapping to which the pages will be attached
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* @pages: A list of potential netfs pages to be filled
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* @end_io_func: The callback to invoke when and if each page is filled
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* @context: An arbitrary piece of data to pass on to end_io_func()
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* @gfp: The conditions under which memory allocation should be made
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*
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* Read a set of pages from the cache, or if that's not possible, attempt to
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* make a potential one-block reservation for each page in the cache into which
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* that page may be stored once fetched from the server.
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*
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* If some pages are not backed by the cache object, or if it there's some
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* reason they can't be, -ENOBUFS will be returned and nothing more will be
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* done for that pages.
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*
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* Else, if some of the pages are backed by the cache, a read will be initiated
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* directly to the netfs's page and 0 will be returned by this function. The
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* end_io_func() callback will be invoked when the operation terminates on a
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* completion or failure. Note that the callback may be invoked before the
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* return.
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*
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* Else, if a page is unbacked, -ENODATA is returned and a block may have
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* been allocated in the cache.
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*
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* Because the function may want to return all of -ENOBUFS, -ENODATA and 0 in
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* regard to different pages, the return values are prioritised in that order.
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* Any pages submitted for reading are removed from the pages list.
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*
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* See Documentation/filesystems/caching/netfs-api.txt for a complete
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* description.
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*/
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static inline
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int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
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struct address_space *mapping,
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struct list_head *pages,
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unsigned *nr_pages,
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fscache_rw_complete_t end_io_func,
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void *context,
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gfp_t gfp)
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{
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if (fscache_cookie_valid(cookie))
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return __fscache_read_or_alloc_pages(cookie, mapping, pages,
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nr_pages, end_io_func,
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context, gfp);
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else
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return -ENOBUFS;
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|
}
|
|
|
|
/**
|
|
* 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);
|
|
}
|
|
|
|
/**
|
|
* fscache_maybe_release_page - Consider releasing a page, cancelling a store
|
|
* @cookie: The cookie representing the cache object
|
|
* @page: The netfs page that is being cached.
|
|
* @gfp: The gfp flags passed to releasepage()
|
|
*
|
|
* Consider releasing a page for the vmscan algorithm, on behalf of the netfs's
|
|
* releasepage() call. A storage request on the page may cancelled if it is
|
|
* not currently being processed.
|
|
*
|
|
* The function returns true if the page no longer has a storage request on it,
|
|
* and false if a storage request is left in place. If true is returned, the
|
|
* page will have been passed to fscache_uncache_page(). If false is returned
|
|
* the page cannot be freed yet.
|
|
*/
|
|
static inline
|
|
bool fscache_maybe_release_page(struct fscache_cookie *cookie,
|
|
struct page *page,
|
|
gfp_t gfp)
|
|
{
|
|
if (fscache_cookie_valid(cookie) && PageFsCache(page))
|
|
return __fscache_maybe_release_page(cookie, page, gfp);
|
|
return false;
|
|
}
|
|
|
|
#endif /* _LINUX_FSCACHE_H */
|