--- /dev/null
+/* General filesystem caching backing cache 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/backend-api.txt
+ *
+ * for a description of the cache backend interface declared here.
+ */
+
+#ifndef _LINUX_FSCACHE_CACHE_H
+#define _LINUX_FSCACHE_CACHE_H
+
+#include <linux/fscache.h>
+#include <linux/sched.h>
+#include <linux/workqueue.h>
+
+#define NR_MAXCACHES BITS_PER_LONG
+
+struct fscache_cache;
+struct fscache_cache_ops;
+struct fscache_object;
+struct fscache_operation;
+
+/*
+ * cache tag definition
+ */
+struct fscache_cache_tag {
+ struct list_head link;
+ struct fscache_cache *cache; /* cache referred to by this tag */
+ unsigned long flags;
+#define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */
+ atomic_t usage;
+ char name[0]; /* tag name */
+};
+
+/*
+ * cache definition
+ */
+struct fscache_cache {
+ const struct fscache_cache_ops *ops;
+ struct fscache_cache_tag *tag; /* tag representing this cache */
+ struct kobject *kobj; /* system representation of this cache */
+ struct list_head link; /* link in list of caches */
+ size_t max_index_size; /* maximum size of index data */
+ char identifier[36]; /* cache label */
+
+ /* node management */
+ struct work_struct op_gc; /* operation garbage collector */
+ struct list_head object_list; /* list of data/index objects */
+ struct list_head op_gc_list; /* list of ops to be deleted */
+ spinlock_t object_list_lock;
+ spinlock_t op_gc_list_lock;
+ atomic_t object_count; /* no. of live objects in this cache */
+ struct fscache_object *fsdef; /* object for the fsdef index */
+ unsigned long flags;
+#define FSCACHE_IOERROR 0 /* cache stopped on I/O error */
+#define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */
+};
+
+extern wait_queue_head_t fscache_cache_cleared_wq;
+
+/*
+ * operation to be applied to a cache object
+ * - retrieval initiation operations are done in the context of the process
+ * that issued them, and not in an async thread pool
+ */
+typedef void (*fscache_operation_release_t)(struct fscache_operation *op);
+typedef void (*fscache_operation_processor_t)(struct fscache_operation *op);
+
+enum fscache_operation_state {
+ FSCACHE_OP_ST_BLANK, /* Op is not yet submitted */
+ FSCACHE_OP_ST_INITIALISED, /* Op is initialised */
+ FSCACHE_OP_ST_PENDING, /* Op is blocked from running */
+ FSCACHE_OP_ST_IN_PROGRESS, /* Op is in progress */
+ FSCACHE_OP_ST_COMPLETE, /* Op is complete */
+ FSCACHE_OP_ST_CANCELLED, /* Op has been cancelled */
+ FSCACHE_OP_ST_DEAD /* Op is now dead */
+};
+
+struct fscache_operation {
+ struct work_struct work; /* record for async ops */
+ struct list_head pend_link; /* link in object->pending_ops */
+ struct fscache_object *object; /* object to be operated upon */
+
+ unsigned long flags;
+#define FSCACHE_OP_TYPE 0x000f /* operation type */
+#define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */
+#define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */
+#define FSCACHE_OP_WAITING 4 /* cleared when op is woken */
+#define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */
+#define FSCACHE_OP_DEC_READ_CNT 6 /* decrement object->n_reads on destruction */
+#define FSCACHE_OP_UNUSE_COOKIE 7 /* call fscache_unuse_cookie() on completion */
+#define FSCACHE_OP_KEEP_FLAGS 0x00f0 /* flags to keep when repurposing an op */
+
+ enum fscache_operation_state state;
+ atomic_t usage;
+ unsigned debug_id; /* debugging ID */
+
+ /* operation processor callback
+ * - can be NULL if FSCACHE_OP_WAITING is going to be used to perform
+ * the op in a non-pool thread */
+ fscache_operation_processor_t processor;
+
+ /* operation releaser */
+ fscache_operation_release_t release;
+};
+
+extern atomic_t fscache_op_debug_id;
+extern void fscache_op_work_func(struct work_struct *work);
+
+extern void fscache_enqueue_operation(struct fscache_operation *);
+extern void fscache_op_complete(struct fscache_operation *, bool);
+extern void fscache_put_operation(struct fscache_operation *);
+
+/**
+ * fscache_operation_init - Do basic initialisation of an operation
+ * @op: The operation to initialise
+ * @release: The release function to assign
+ *
+ * Do basic initialisation of an operation. The caller must still set flags,
+ * object and processor if needed.
+ */
+static inline void fscache_operation_init(struct fscache_operation *op,
+ fscache_operation_processor_t processor,
+ fscache_operation_release_t release)
+{
+ INIT_WORK(&op->work, fscache_op_work_func);
+ atomic_set(&op->usage, 1);
+ op->state = FSCACHE_OP_ST_INITIALISED;
+ op->debug_id = atomic_inc_return(&fscache_op_debug_id);
+ op->processor = processor;
+ op->release = release;
+ INIT_LIST_HEAD(&op->pend_link);
+}
+
+/*
+ * data read operation
+ */
+struct fscache_retrieval {
+ struct fscache_operation op;
+ struct address_space *mapping; /* netfs pages */
+ fscache_rw_complete_t end_io_func; /* function to call on I/O completion */
+ void *context; /* netfs read context (pinned) */
+ struct list_head to_do; /* list of things to be done by the backend */
+ unsigned long start_time; /* time at which retrieval started */
+ atomic_t n_pages; /* number of pages to be retrieved */
+};
+
+typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
+ struct page *page,
+ gfp_t gfp);
+
+typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op,
+ struct list_head *pages,
+ unsigned *nr_pages,
+ gfp_t gfp);
+
+/**
+ * fscache_get_retrieval - Get an extra reference on a retrieval operation
+ * @op: The retrieval operation to get a reference on
+ *
+ * Get an extra reference on a retrieval operation.
+ */
+static inline
+struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op)
+{
+ atomic_inc(&op->op.usage);
+ return op;
+}
+
+/**
+ * fscache_enqueue_retrieval - Enqueue a retrieval operation for processing
+ * @op: The retrieval operation affected
+ *
+ * Enqueue a retrieval operation for processing by the FS-Cache thread pool.
+ */
+static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
+{
+ fscache_enqueue_operation(&op->op);
+}
+
+/**
+ * fscache_retrieval_complete - Record (partial) completion of a retrieval
+ * @op: The retrieval operation affected
+ * @n_pages: The number of pages to account for
+ */
+static inline void fscache_retrieval_complete(struct fscache_retrieval *op,
+ int n_pages)
+{
+ atomic_sub(n_pages, &op->n_pages);
+ if (atomic_read(&op->n_pages) <= 0)
+ fscache_op_complete(&op->op, true);
+}
+
+/**
+ * fscache_put_retrieval - Drop a reference to a retrieval operation
+ * @op: The retrieval operation affected
+ *
+ * Drop a reference to a retrieval operation.
+ */
+static inline void fscache_put_retrieval(struct fscache_retrieval *op)
+{
+ fscache_put_operation(&op->op);
+}
+
+/*
+ * cached page storage work item
+ * - used to do three things:
+ * - batch writes to the cache
+ * - do cache writes asynchronously
+ * - defer writes until cache object lookup completion
+ */
+struct fscache_storage {
+ struct fscache_operation op;
+ pgoff_t store_limit; /* don't write more than this */
+};
+
+/*
+ * cache operations
+ */
+struct fscache_cache_ops {
+ /* name of cache provider */
+ const char *name;
+
+ /* allocate an object record for a cookie */
+ struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
+ struct fscache_cookie *cookie);
+
+ /* look up the object for a cookie
+ * - return -ETIMEDOUT to be requeued
+ */
+ int (*lookup_object)(struct fscache_object *object);
+
+ /* finished looking up */
+ void (*lookup_complete)(struct fscache_object *object);
+
+ /* increment the usage count on this object (may fail if unmounting) */
+ struct fscache_object *(*grab_object)(struct fscache_object *object);
+
+ /* pin an object in the cache */
+ int (*pin_object)(struct fscache_object *object);
+
+ /* unpin an object in the cache */
+ void (*unpin_object)(struct fscache_object *object);
+
+ /* check the consistency between the backing cache and the FS-Cache
+ * cookie */
+ bool (*check_consistency)(struct fscache_operation *op);
+
+ /* store the updated auxiliary data on an object */
+ void (*update_object)(struct fscache_object *object);
+
+ /* Invalidate an object */
+ void (*invalidate_object)(struct fscache_operation *op);
+
+ /* discard the resources pinned by an object and effect retirement if
+ * necessary */
+ void (*drop_object)(struct fscache_object *object);
+
+ /* dispose of a reference to an object */
+ void (*put_object)(struct fscache_object *object);
+
+ /* sync a cache */
+ void (*sync_cache)(struct fscache_cache *cache);
+
+ /* notification that the attributes of a non-index object (such as
+ * i_size) have changed */
+ int (*attr_changed)(struct fscache_object *object);
+
+ /* reserve space for an object's data and associated metadata */
+ int (*reserve_space)(struct fscache_object *object, loff_t i_size);
+
+ /* request a backing block for a page be read or allocated in the
+ * cache */
+ fscache_page_retrieval_func_t read_or_alloc_page;
+
+ /* request backing blocks for a list of pages be read or allocated in
+ * the cache */
+ fscache_pages_retrieval_func_t read_or_alloc_pages;
+
+ /* request a backing block for a page be allocated in the cache so that
+ * it can be written directly */
+ fscache_page_retrieval_func_t allocate_page;
+
+ /* request backing blocks for pages be allocated in the cache so that
+ * they can be written directly */
+ fscache_pages_retrieval_func_t allocate_pages;
+
+ /* write a page to its backing block in the cache */
+ int (*write_page)(struct fscache_storage *op, struct page *page);
+
+ /* detach backing block from a page (optional)
+ * - must release the cookie lock before returning
+ * - may sleep
+ */
+ void (*uncache_page)(struct fscache_object *object,
+ struct page *page);
+
+ /* dissociate a cache from all the pages it was backing */
+ void (*dissociate_pages)(struct fscache_cache *cache);
+};
+
+extern struct fscache_cookie fscache_fsdef_index;
+
+/*
+ * Event list for fscache_object::{event_mask,events}
+ */
+enum {
+ FSCACHE_OBJECT_EV_NEW_CHILD, /* T if object has a new child */
+ FSCACHE_OBJECT_EV_PARENT_READY, /* T if object's parent is ready */
+ FSCACHE_OBJECT_EV_UPDATE, /* T if object should be updated */
+ FSCACHE_OBJECT_EV_INVALIDATE, /* T if cache requested object invalidation */
+ FSCACHE_OBJECT_EV_CLEARED, /* T if accessors all gone */
+ FSCACHE_OBJECT_EV_ERROR, /* T if fatal error occurred during processing */
+ FSCACHE_OBJECT_EV_KILL, /* T if netfs relinquished or cache withdrew object */
+ NR_FSCACHE_OBJECT_EVENTS
+};
+
+#define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
+
+/*
+ * States for object state machine.
+ */
+struct fscache_transition {
+ unsigned long events;
+ const struct fscache_state *transit_to;
+};
+
+struct fscache_state {
+ char name[24];
+ char short_name[8];
+ const struct fscache_state *(*work)(struct fscache_object *object,
+ int event);
+ const struct fscache_transition transitions[];
+};
+
+/*
+ * on-disk cache file or index handle
+ */
+struct fscache_object {
+ const struct fscache_state *state; /* Object state machine state */
+ const struct fscache_transition *oob_table; /* OOB state transition table */
+ int debug_id; /* debugging ID */
+ int n_children; /* number of child objects */
+ int n_ops; /* number of extant ops on object */
+ int n_obj_ops; /* number of object ops outstanding on object */
+ int n_in_progress; /* number of ops in progress */
+ int n_exclusive; /* number of exclusive ops queued or in progress */
+ atomic_t n_reads; /* number of read ops in progress */
+ spinlock_t lock; /* state and operations lock */
+
+ unsigned long lookup_jif; /* time at which lookup started */
+ unsigned long oob_event_mask; /* OOB events this object is interested in */
+ unsigned long event_mask; /* events this object is interested in */
+ unsigned long events; /* events to be processed by this object
+ * (order is important - using fls) */
+
+ unsigned long flags;
+#define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */
+#define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */
+#define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */
+#define FSCACHE_OBJECT_IS_LIVE 3 /* T if object is not withdrawn or relinquished */
+#define FSCACHE_OBJECT_IS_LOOKED_UP 4 /* T if object has been looked up */
+#define FSCACHE_OBJECT_IS_AVAILABLE 5 /* T if object has become active */
+#define FSCACHE_OBJECT_RETIRED 6 /* T if object was retired on relinquishment */
+
+ struct list_head cache_link; /* link in cache->object_list */
+ struct hlist_node cookie_link; /* link in cookie->backing_objects */
+ struct fscache_cache *cache; /* cache that supplied this object */
+ struct fscache_cookie *cookie; /* netfs's file/index object */
+ struct fscache_object *parent; /* parent object */
+ struct work_struct work; /* attention scheduling record */
+ struct list_head dependents; /* FIFO of dependent objects */
+ struct list_head dep_link; /* link in parent's dependents list */
+ struct list_head pending_ops; /* unstarted operations on this object */
+#ifdef CONFIG_FSCACHE_OBJECT_LIST
+ struct rb_node objlist_link; /* link in global object list */
+#endif
+ pgoff_t store_limit; /* current storage limit */
+ loff_t store_limit_l; /* current storage limit */
+};
+
+extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *,
+ struct fscache_cache *);
+extern void fscache_object_destroy(struct fscache_object *);
+
+extern void fscache_object_lookup_negative(struct fscache_object *object);
+extern void fscache_obtained_object(struct fscache_object *object);
+
+static inline bool fscache_object_is_live(struct fscache_object *object)
+{
+ return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
+}
+
+static inline bool fscache_object_is_dying(struct fscache_object *object)
+{
+ return !fscache_object_is_live(object);
+}
+
+static inline bool fscache_object_is_available(struct fscache_object *object)
+{
+ return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
+}
+
+static inline bool fscache_object_is_active(struct fscache_object *object)
+{
+ return fscache_object_is_available(object) &&
+ fscache_object_is_live(object) &&
+ !test_bit(FSCACHE_IOERROR, &object->cache->flags);
+}
+
+static inline bool fscache_object_is_dead(struct fscache_object *object)
+{
+ return fscache_object_is_dying(object) &&
+ test_bit(FSCACHE_IOERROR, &object->cache->flags);
+}
+
+/**
+ * fscache_object_destroyed - Note destruction of an object in a cache
+ * @cache: The cache from which the object came
+ *
+ * Note the destruction and deallocation of an object record in a cache.
+ */
+static inline void fscache_object_destroyed(struct fscache_cache *cache)
+{
+ if (atomic_dec_and_test(&cache->object_count))
+ wake_up_all(&fscache_cache_cleared_wq);
+}
+
+/**
+ * fscache_object_lookup_error - Note an object encountered an error
+ * @object: The object on which the error was encountered
+ *
+ * Note that an object encountered a fatal error (usually an I/O error) and
+ * that it should be withdrawn as soon as possible.
+ */
+static inline void fscache_object_lookup_error(struct fscache_object *object)
+{
+ set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
+}
+
+/**
+ * fscache_set_store_limit - Set the maximum size to be stored in an object
+ * @object: The object to set the maximum on
+ * @i_size: The limit to set in bytes
+ *
+ * Set the maximum size an object is permitted to reach, implying the highest
+ * byte that may be written. Intended to be called by the attr_changed() op.
+ *
+ * See Documentation/filesystems/caching/backend-api.txt for a complete
+ * description.
+ */
+static inline
+void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
+{
+ object->store_limit_l = i_size;
+ object->store_limit = i_size >> PAGE_SHIFT;
+ if (i_size & ~PAGE_MASK)
+ object->store_limit++;
+}
+
+/**
+ * fscache_end_io - End a retrieval operation on a page
+ * @op: The FS-Cache operation covering the retrieval
+ * @page: The page that was to be fetched
+ * @error: The error code (0 if successful)
+ *
+ * Note the end of an operation to retrieve a page, as covered by a particular
+ * operation record.
+ */
+static inline void fscache_end_io(struct fscache_retrieval *op,
+ struct page *page, int error)
+{
+ op->end_io_func(page, op->context, error);
+}
+
+static inline void __fscache_use_cookie(struct fscache_cookie *cookie)
+{
+ atomic_inc(&cookie->n_active);
+}
+
+/**
+ * fscache_use_cookie - Request usage of cookie attached to an object
+ * @object: Object description
+ *
+ * Request usage of the cookie attached to an object. NULL is returned if the
+ * relinquishment had reduced the cookie usage count to 0.
+ */
+static inline bool fscache_use_cookie(struct fscache_object *object)
+{
+ struct fscache_cookie *cookie = object->cookie;
+ return atomic_inc_not_zero(&cookie->n_active) != 0;
+}
+
+static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie)
+{
+ return atomic_dec_and_test(&cookie->n_active);
+}
+
+static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie)
+{
+ wake_up_atomic_t(&cookie->n_active);
+}
+
+/**
+ * fscache_unuse_cookie - Cease usage of cookie attached to an object
+ * @object: Object description
+ *
+ * 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_object *object)
+{
+ struct fscache_cookie *cookie = object->cookie;
+ if (__fscache_unuse_cookie(cookie))
+ __fscache_wake_unused_cookie(cookie);
+}
+
+/*
+ * out-of-line cache backend functions
+ */
+extern __printf(3, 4)
+void fscache_init_cache(struct fscache_cache *cache,
+ const struct fscache_cache_ops *ops,
+ const char *idfmt, ...);
+
+extern int fscache_add_cache(struct fscache_cache *cache,
+ struct fscache_object *fsdef,
+ const char *tagname);
+extern void fscache_withdraw_cache(struct fscache_cache *cache);
+
+extern void fscache_io_error(struct fscache_cache *cache);
+
+extern void fscache_mark_page_cached(struct fscache_retrieval *op,
+ struct page *page);
+
+extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
+ struct pagevec *pagevec);
+
+extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
+
+extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
+ const void *data,
+ uint16_t datalen);
+
+#endif /* _LINUX_FSCACHE_CACHE_H */
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