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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* General filesystem caching interface
*
* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* NOTE!!! See:
*
* Documentation/filesystems/caching/netfs-api.rst
*
* for a description of the network filesystem interface declared here.
*/
#ifndef _LINUX_FSCACHE_H
#define _LINUX_FSCACHE_H
#include <linux/fs.h>
#include <linux/netfs.h>
#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
#define __fscache_available (1)
#define fscache_available() (1)
#define fscache_volume_valid(volume) (volume)
#define fscache_cookie_valid(cookie) (cookie)
#define fscache_cookie_enabled(cookie) (cookie)
#else
#define __fscache_available (0)
#define fscache_available() (0)
#define fscache_volume_valid(volume) (0)
#define fscache_cookie_valid(cookie) (0)
#define fscache_cookie_enabled(cookie) (0)
#endif
/*
* Volume representation cookie.
*/
struct fscache_volume {
refcount_t ref;
atomic_t n_cookies; /* Number of data cookies in volume */
atomic_t n_accesses; /* Number of cache accesses in progress */
unsigned int debug_id;
unsigned int key_hash; /* Hash of key string */
char *key; /* Volume ID, eg. "afs@example.com@1234" */
struct list_head proc_link; /* Link in /proc/fs/fscache/volumes */
struct hlist_bl_node hash_link; /* Link in hash table */
struct work_struct work;
struct fscache_cache *cache; /* The cache in which this resides */
void *cache_priv; /* Cache private data */
spinlock_t lock;
unsigned long flags;
#define FSCACHE_VOLUME_RELINQUISHED 0 /* Volume is being cleaned up */
#define FSCACHE_VOLUME_INVALIDATE 1 /* Volume was invalidated */
#define FSCACHE_VOLUME_COLLIDED_WITH 2 /* Volume was collided with */
#define FSCACHE_VOLUME_ACQUIRE_PENDING 3 /* Volume is waiting to complete acquisition */
#define FSCACHE_VOLUME_CREATING 4 /* Volume is being created on disk */
};
/*
* 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 struct fscache_volume *__fscache_acquire_volume(const char *, const char *,
const void *, size_t);
extern void __fscache_relinquish_volume(struct fscache_volume *, const void *, bool);
/**
* fscache_acquire_volume - Register a volume as desiring caching services
* @volume_key: An identification string for the volume
* @cache_name: The name of the cache to use (or NULL for the default)
* @coherency_data: Piece of arbitrary coherency data to check (or NULL)
* @coherency_len: The size of the coherency data
*
* Register a volume as desiring caching services if they're available. The
* caller must provide an identifier for the volume and may also indicate which
* cache it should be in. If a preexisting volume entry is found in the cache,
* the coherency data must match otherwise the entry will be invalidated.
*
* Returns a cookie pointer on success, -ENOMEM if out of memory or -EBUSY if a
* cache volume of that name is already acquired. Note that "NULL" is a valid
* cookie pointer and can be returned if caching is refused.
*/
static inline
struct fscache_volume *fscache_acquire_volume(const char *volume_key,
const char *cache_name,
const void *coherency_data,
size_t coherency_len)
{
if (!fscache_available())
return NULL;
return __fscache_acquire_volume(volume_key, cache_name,
coherency_data, coherency_len);
}
/**
* fscache_relinquish_volume - Cease caching a volume
* @volume: The volume cookie
* @coherency_data: Piece of arbitrary coherency data to set (or NULL)
* @invalidate: True if the volume should be invalidated
*
* Indicate that a filesystem no longer desires caching services for a volume.
* The caller must have relinquished all file cookies prior to calling this.
* The stored coherency data is updated.
*/
static inline
void fscache_relinquish_volume(struct fscache_volume *volume,
const void *coherency_data,
bool invalidate)
{
if (fscache_volume_valid(volume))
__fscache_relinquish_volume(volume, coherency_data, invalidate);
}
#endif /* _LINUX_FSCACHE_H */
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