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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 ([email protected])
*
* 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>
#include <linux/writeback.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 */
#define FSCACHE_ADV_WANT_CACHE_SIZE 0x04 /* Retrieve cache size at runtime */
#define FSCACHE_INVAL_DIO_WRITE 0x01 /* Invalidate due to DIO write */
enum fscache_want_state {
FSCACHE_WANT_PARAMS,
FSCACHE_WANT_WRITE,
FSCACHE_WANT_READ,
};
/*
* 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_INVALIDATING, /* The cache is being invalidated */
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FSCACHE_COOKIE_STATE_WITHDRAWING, /* The cookie is being withdrawn */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 */
u8 *key; /* Volume ID, eg. "[email protected]@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 */
u8 coherency_len; /* Length of the coherency data */
u8 coherency[]; /* Coherency data */
};
/*
* 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 */
#define FSCACHE_COOKIE_DO_INVALIDATE 15 /* T if cookie needs invalidation */
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);
extern void __fscache_resize_cookie(struct fscache_cookie *, loff_t);
extern void __fscache_invalidate(struct fscache_cookie *, const void *, loff_t, unsigned int);
extern int __fscache_begin_read_operation(struct netfs_cache_resources *, struct fscache_cookie *);
extern int __fscache_begin_write_operation(struct netfs_cache_resources *, struct fscache_cookie *);
extern void __fscache_write_to_cache(struct fscache_cookie *, struct address_space *,
loff_t, size_t, loff_t, netfs_io_terminated_t, void *,
bool);
extern void __fscache_clear_page_bits(struct address_space *, loff_t, size_t);
/**
* 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
* @cookie: The cookie representing the cache object
* @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
* @cookie: The cookie representing the cache object
* @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);
}
/**
* fscache_update_cookie - Request that a cache object be updated
* @cookie: The cookie representing the cache object
* @aux_data: The updated auxiliary data for the cookie (may be NULL)
* @object_size: The current size of the object (may be NULL)
*
* Request an update of the index data for the cache object associated with the
* cookie. The auxiliary data on the cookie will be updated first if @aux_data
* is set and the object size will be updated and the object possibly trimmed
* if @object_size is set.
*
* See Documentation/filesystems/caching/netfs-api.rst for a complete
* description.
*/
static inline
void fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
const loff_t *object_size)
{
if (fscache_cookie_enabled(cookie))
__fscache_update_cookie(cookie, aux_data, object_size);
}
/**
* fscache_resize_cookie - Request that a cache object be resized
* @cookie: The cookie representing the cache object
* @new_size: The new size of the object (may be NULL)
*
* Request that the size of an object be changed.
*
* See Documentation/filesystems/caching/netfs-api.rst for a complete
* description.
*/
static inline
void fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size)
{
if (fscache_cookie_enabled(cookie))
__fscache_resize_cookie(cookie, new_size);
}
/**
* fscache_invalidate - Notify cache that an object needs invalidation
* @cookie: The cookie representing the cache object
* @aux_data: The updated auxiliary data for the cookie (may be NULL)
* @size: The revised size of the object.
* @flags: Invalidation flags (FSCACHE_INVAL_*)
*
* Notify the cache that an object is needs to be invalidated and that it
* should abort any retrievals or stores it is doing on the cache. This
* increments inval_counter on the cookie which can be used by the caller to
* reconsider I/O requests as they complete.
*
* If @flags has FSCACHE_INVAL_DIO_WRITE set, this indicates that this is due
* to a direct I/O write and will cause caching to be disabled on this cookie
* until it is completely unused.
*
* See Documentation/filesystems/caching/netfs-api.rst for a complete
* description.
*/
static inline
void fscache_invalidate(struct fscache_cookie *cookie,
const void *aux_data, loff_t size, unsigned int flags)
{
if (fscache_cookie_enabled(cookie))
__fscache_invalidate(cookie, aux_data, size, flags);
}
/**
* fscache_operation_valid - Return true if operations resources are usable
* @cres: The resources to check.
*
* Returns a pointer to the operations table if usable or NULL if not.
*/
static inline
const struct netfs_cache_ops *fscache_operation_valid(const struct netfs_cache_resources *cres)
{
return fscache_resources_valid(cres) ? cres->ops : NULL;
}
/**
* fscache_begin_read_operation - Begin a read operation for the netfs lib
* @cres: The cache resources for the read being performed
* @cookie: The cookie representing the cache object
*
* Begin a read operation on behalf of the netfs helper library. @cres
* indicates the cache resources to which the operation state should be
* attached; @cookie indicates the cache object that will be accessed.
*
* @cres->inval_counter is set from @cookie->inval_counter for comparison at
* the end of the operation. This allows invalidation during the operation to
* be detected by the caller.
*
* Returns:
* * 0 - Success
* * -ENOBUFS - No caching available
* * Other error code from the cache, such as -ENOMEM.
*/
static inline
int fscache_begin_read_operation(struct netfs_cache_resources *cres,
struct fscache_cookie *cookie)
{
if (fscache_cookie_enabled(cookie))
return __fscache_begin_read_operation(cres, cookie);
return -ENOBUFS;
}
/**
* fscache_end_operation - End the read operation for the netfs lib
* @cres: The cache resources for the read operation
*
* Clean up the resources at the end of the read request.
*/
static inline void fscache_end_operation(struct netfs_cache_resources *cres)
{
const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
if (ops)
ops->end_operation(cres);
}
/**
* fscache_read - Start a read from the cache.
* @cres: The cache resources to use
* @start_pos: The beginning file offset in the cache file
* @iter: The buffer to fill - and also the length
* @read_hole: How to handle a hole in the data.
* @term_func: The function to call upon completion
* @term_func_priv: The private data for @term_func
*
* Start a read from the cache. @cres indicates the cache object to read from
* and must be obtained by a call to fscache_begin_operation() beforehand.
*
* The data is read into the iterator, @iter, and that also indicates the size
* of the operation. @start_pos is the start position in the file, though if
* @seek_data is set appropriately, the cache can use SEEK_DATA to find the
* next piece of data, writing zeros for the hole into the iterator.
*
* Upon termination of the operation, @term_func will be called and supplied
* with @term_func_priv plus the amount of data written, if successful, or the
* error code otherwise.
*
* @read_hole indicates how a partially populated region in the cache should be
* handled. It can be one of a number of settings:
*
* NETFS_READ_HOLE_IGNORE - Just try to read (may return a short read).
*
* NETFS_READ_HOLE_CLEAR - Seek for data, clearing the part of the buffer
* skipped over, then do as for IGNORE.
*
* NETFS_READ_HOLE_FAIL - Give ENODATA if we encounter a hole.
*/
static inline
int fscache_read(struct netfs_cache_resources *cres,
loff_t start_pos,
struct iov_iter *iter,
enum netfs_read_from_hole read_hole,
netfs_io_terminated_t term_func,
void *term_func_priv)
{
const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
return ops->read(cres, start_pos, iter, read_hole,
term_func, term_func_priv);
}
/**
* fscache_begin_write_operation - Begin a write operation for the netfs lib
* @cres: The cache resources for the write being performed
* @cookie: The cookie representing the cache object
*
* Begin a write operation on behalf of the netfs helper library. @cres
* indicates the cache resources to which the operation state should be
* attached; @cookie indicates the cache object that will be accessed.
*
* @cres->inval_counter is set from @cookie->inval_counter for comparison at
* the end of the operation. This allows invalidation during the operation to
* be detected by the caller.
*
* Returns:
* * 0 - Success
* * -ENOBUFS - No caching available
* * Other error code from the cache, such as -ENOMEM.
*/
static inline
int fscache_begin_write_operation(struct netfs_cache_resources *cres,
struct fscache_cookie *cookie)
{
if (fscache_cookie_enabled(cookie))
return __fscache_begin_write_operation(cres, cookie);
return -ENOBUFS;
}
/**
* fscache_write - Start a write to the cache.
* @cres: The cache resources to use
* @start_pos: The beginning file offset in the cache file
* @iter: The data to write - and also the length
* @term_func: The function to call upon completion
* @term_func_priv: The private data for @term_func
*
* Start a write to the cache. @cres indicates the cache object to write to and
* must be obtained by a call to fscache_begin_operation() beforehand.
*
* The data to be written is obtained from the iterator, @iter, and that also
* indicates the size of the operation. @start_pos is the start position in
* the file.
*
* Upon termination of the operation, @term_func will be called and supplied
* with @term_func_priv plus the amount of data written, if successful, or the
* error code otherwise.
*/
static inline
int fscache_write(struct netfs_cache_resources *cres,
loff_t start_pos,
struct iov_iter *iter,
netfs_io_terminated_t term_func,
void *term_func_priv)
{
const struct netfs_cache_ops *ops = fscache_operation_valid(cres);
return ops->write(cres, start_pos, iter, term_func, term_func_priv);
}
/**
* fscache_clear_page_bits - Clear the PG_fscache bits from a set of pages
* @mapping: The netfs inode to use as the source
* @start: The start position in @mapping
* @len: The amount of data to unlock
* @caching: If PG_fscache has been set
*
* Clear the PG_fscache flag from a sequence of pages and wake up anyone who's
* waiting.
*/
static inline void fscache_clear_page_bits(struct address_space *mapping,
loff_t start, size_t len,
bool caching)
{
if (caching)
__fscache_clear_page_bits(mapping, start, len);
}
/**
* fscache_write_to_cache - Save a write to the cache and clear PG_fscache
* @cookie: The cookie representing the cache object
* @mapping: The netfs inode to use as the source
* @start: The start position in @mapping
* @len: The amount of data to write back
* @i_size: The new size of the inode
* @term_func: The function to call upon completion
* @term_func_priv: The private data for @term_func
* @caching: If PG_fscache has been set
*
* Helper function for a netfs to write dirty data from an inode into the cache
* object that's backing it.
*
* @start and @len describe the range of the data. This does not need to be
* page-aligned, but to satisfy DIO requirements, the cache may expand it up to
* the page boundaries on either end. All the pages covering the range must be
* marked with PG_fscache.
*
* If given, @term_func will be called upon completion and supplied with
* @term_func_priv. Note that the PG_fscache flags will have been cleared by
* this point, so the netfs must retain its own pin on the mapping.
*/
static inline void fscache_write_to_cache(struct fscache_cookie *cookie,
struct address_space *mapping,
loff_t start, size_t len, loff_t i_size,
netfs_io_terminated_t term_func,
void *term_func_priv,
bool caching)
{
if (caching)
__fscache_write_to_cache(cookie, mapping, start, len, i_size,
term_func, term_func_priv, caching);
else if (term_func)
term_func(term_func_priv, -ENOBUFS, false);
}
/**
* fscache_note_page_release - Note that a netfs page got released
* @cookie: The cookie corresponding to the file
*
* Note that a page that has been copied to the cache has been released. This
* means that future reads will need to look in the cache to see if it's there.
*/
static inline
void fscache_note_page_release(struct fscache_cookie *cookie)
{
/* If we've written data to the cache (HAVE_DATA) and there wasn't any
* data in the cache when we started (NO_DATA_TO_READ), it may no
* longer be true that we can skip reading from the cache - so clear
* the flag that causes reads to be skipped.
*/
if (cookie &&
test_bit(FSCACHE_COOKIE_HAVE_DATA, &cookie->flags) &&
test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags))
clear_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
}
#endif /* _LINUX_FSCACHE_H */
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