/* 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_resources_valid(cres) ((cres)->cache_priv)
#define fscache_cookie_enabled(cookie) (cookie && !test_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags))
#else
#define __fscache_available (0)
#define fscache_available() (0)
#define fscache_volume_valid(volume) (0)
#define fscache_cookie_valid(cookie) (0)
#define fscache_resources_valid(cres) (false)
#define fscache_cookie_enabled(cookie) (0)
#endif
struct fscache_cookie;
#define FSCACHE_ADV_SINGLE_CHUNK 0x01 /* The object is a single chunk of data */
#define FSCACHE_ADV_WRITE_CACHE 0x00 /* Do cache if written to locally */
#define FSCACHE_ADV_WRITE_NOCACHE 0x02 /* Don't cache if written to locally */
/*
* Data object state.
*/
enum fscache_cookie_state {
FSCACHE_COOKIE_STATE_QUIESCENT, /* The cookie is uncached */
FSCACHE_COOKIE_STATE_LOOKING_UP, /* The cache object is being looked up */
FSCACHE_COOKIE_STATE_CREATING, /* The cache object is being created */
FSCACHE_COOKIE_STATE_ACTIVE, /* The cache is active, readable and writable */
FSCACHE_COOKIE_STATE_FAILED, /* The cache failed, withdraw to clear */
FSCACHE_COOKIE_STATE_LRU_DISCARDING, /* The cookie is being discarded by the LRU */
FSCACHE_COOKIE_STATE_WITHDRAWING, /* The cookie is being withdrawn */
FSCACHE_COOKIE_STATE_RELINQUISHING, /* The cookie is being relinquished */
FSCACHE_COOKIE_STATE_DROPPED, /* The cookie has been dropped */
#define FSCACHE_COOKIE_STATE__NR (FSCACHE_COOKIE_STATE_DROPPED + 1)
} __attribute__((mode(byte)));
/*
* 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 */
};
/*
* Data file representation cookie.
* - a file will only appear in one cache
* - a request to cache a file may or may not be honoured, subject to
* constraints such as disk space
* - indices are created on disk just-in-time
*/
struct fscache_cookie {
refcount_t ref;
atomic_t n_active; /* number of active users of cookie */
atomic_t n_accesses; /* Number of cache accesses in progress */
unsigned int debug_id;
unsigned int inval_counter; /* Number of invalidations made */
spinlock_t lock;
struct fscache_volume *volume; /* Parent volume of this file. */
void *cache_priv; /* Cache-side representation */
struct hlist_bl_node hash_link; /* Link in hash table */
struct list_head proc_link; /* Link in proc list */
struct list_head commit_link; /* Link in commit queue */
struct work_struct work; /* Commit/relinq/withdraw work */
loff_t object_size; /* Size of the netfs object */
unsigned long unused_at; /* Time at which unused (jiffies) */
unsigned long flags;
#define FSCACHE_COOKIE_RELINQUISHED 0 /* T if cookie has been relinquished */
#define FSCACHE_COOKIE_RETIRED 1 /* T if this cookie has retired on relinq */
#define FSCACHE_COOKIE_IS_CACHING 2 /* T if this cookie is cached */
#define FSCACHE_COOKIE_NO_DATA_TO_READ 3 /* T if this cookie has nothing to read */
#define FSCACHE_COOKIE_NEEDS_UPDATE 4 /* T if attrs have been updated */
#define FSCACHE_COOKIE_HAS_BEEN_CACHED 5 /* T if cookie needs withdraw-on-relinq */
#define FSCACHE_COOKIE_DISABLED 6 /* T if cookie has been disabled */
#define FSCACHE_COOKIE_LOCAL_WRITE 7 /* T if cookie has been modified locally */
#define FSCACHE_COOKIE_NO_ACCESS_WAKE 8 /* T if no wake when n_accesses goes 0 */
#define FSCACHE_COOKIE_DO_RELINQUISH 9 /* T if this cookie needs relinquishment */
#define FSCACHE_COOKIE_DO_WITHDRAW 10 /* T if this cookie needs withdrawing */
#define FSCACHE_COOKIE_DO_LRU_DISCARD 11 /* T if this cookie needs LRU discard */
#define FSCACHE_COOKIE_DO_PREP_TO_WRITE 12 /* T if cookie needs write preparation */
#define FSCACHE_COOKIE_HAVE_DATA 13 /* T if this cookie has data stored */
#define FSCACHE_COOKIE_IS_HASHED 14 /* T if this cookie is hashed */
enum fscache_cookie_state state;
u8 advice; /* FSCACHE_ADV_* */
u8 key_len; /* Length of index key */
u8 aux_len; /* Length of auxiliary data */
u32 key_hash; /* Hash of volume, key, len */
union {
void *key; /* Index key */
u8 inline_key[16]; /* - If the key is short enough */
};
union {
void *aux; /* Auxiliary data */
u8 inline_aux[8]; /* - If the aux data is short enough */
};
};
/*
* 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);
extern struct fscache_cookie *__fscache_acquire_cookie(
struct fscache_volume *,
u8,
const void *, size_t,
const void *, size_t,
loff_t);
extern void __fscache_use_cookie(struct fscache_cookie *, bool);
extern void __fscache_unuse_cookie(struct fscache_cookie *, const void *, const loff_t *);
extern void __fscache_relinquish_cookie(struct fscache_cookie *, 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);
}
/**
* fscache_acquire_cookie - Acquire a cookie to represent a cache object
* @volume: The volume in which to locate/create this cookie
* @advice: Advice flags (FSCACHE_COOKIE_ADV_*)
* @index_key: The index key for this cookie
* @index_key_len: Size of the index key
* @aux_data: The auxiliary data for the cookie (may be NULL)
* @aux_data_len: Size of the auxiliary data buffer
* @object_size: The initial size of object
*
* Acquire a cookie to represent a data file within the given cache volume.
*
* See Documentation/filesystems/caching/netfs-api.rst for a complete
* description.
*/
static inline
struct fscache_cookie *fscache_acquire_cookie(struct fscache_volume *volume,
u8 advice,
const void *index_key,
size_t index_key_len,
const void *aux_data,
size_t aux_data_len,
loff_t object_size)
{
if (!fscache_volume_valid(volume))
return NULL;
return __fscache_acquire_cookie(volume, advice,
index_key, index_key_len,
aux_data, aux_data_len,
object_size);
}
/**
* fscache_use_cookie - Request usage of cookie attached to an object
* @object: Object description
* @will_modify: If cache is expected to be modified locally
*
* Request usage of the cookie attached to an object. The caller should tell
* the cache if the object's contents are about to be modified locally and then
* the cache can apply the policy that has been set to handle this case.
*/
static inline void fscache_use_cookie(struct fscache_cookie *cookie,
bool will_modify)
{
if (fscache_cookie_valid(cookie))
__fscache_use_cookie(cookie, will_modify);
}
/**
* fscache_unuse_cookie - Cease usage of cookie attached to an object
* @object: Object description
* @aux_data: Updated auxiliary data (or NULL)
* @object_size: Revised size of the object (or NULL)
*
* Cease usage of the cookie attached to an object. When the users count
* reaches zero then the cookie relinquishment will be permitted to proceed.
*/
static inline void fscache_unuse_cookie(struct fscache_cookie *cookie,
const void *aux_data,
const loff_t *object_size)
{
if (fscache_cookie_valid(cookie))
__fscache_unuse_cookie(cookie, aux_data, object_size);
}
/**
* 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.rst for a complete
* description.
*/
static inline
void fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
{
if (fscache_cookie_valid(cookie))
__fscache_relinquish_cookie(cookie, retire);
}
/*
* Find the auxiliary data on a cookie.
*/
static inline void *fscache_get_aux(struct fscache_cookie *cookie)
{
if (cookie->aux_len <= sizeof(cookie->inline_aux))
return cookie->inline_aux;
else
return cookie->aux;
}
/*
* Update the auxiliary data on a cookie.
*/
static inline
void fscache_update_aux(struct fscache_cookie *cookie,
const void *aux_data, const loff_t *object_size)
{
void *p = fscache_get_aux(cookie);
if (aux_data && p)
memcpy(p, aux_data, cookie->aux_len);
if (object_size)
cookie->object_size = *object_size;
}
#ifdef CONFIG_FSCACHE_STATS
extern atomic_t fscache_n_updates;
#endif
static inline
void __fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
const loff_t *object_size)
{
#ifdef CONFIG_FSCACHE_STATS
atomic_inc(&fscache_n_updates);
#endif
fscache_update_aux(cookie, aux_data, object_size);
smp_wmb();
set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
}
#endif /* _LINUX_FSCACHE_H */
