--- /dev/null
+/* fscache-cache.h: general filesystem caching backing cache interface
+ *
+ * Copyright (C) 2004-6 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>
+
+#define NR_MAXCACHES BITS_PER_LONG
+
+struct fscache_cache;
+struct fscache_cache_ops;
+struct fscache_object;
+
+/*
+ * cache tag definition
+ */
+struct fscache_cache_tag {
+ struct list_head link;
+ struct fscache_cache *cache; /* cache referred to by this tag */
+ atomic_t usage;
+ char name[0]; /* tag name */
+};
+
+/*
+ * cache definition
+ */
+struct fscache_cache {
+ struct fscache_cache_ops *ops;
+ struct fscache_cache_tag *tag; /* tag representing this cache */
+ struct list_head link; /* link in list of caches */
+ struct rw_semaphore withdrawal_sem; /* withdrawal control sem */
+ size_t max_index_size; /* maximum size of index data */
+ char identifier[32]; /* cache label */
+
+ /* node management */
+ struct list_head object_list; /* list of data/index objects */
+ spinlock_t object_list_lock;
+ struct fscache_object *fsdef; /* object for the fsdef index */
+ unsigned long flags;
+#define FSCACHE_IOERROR 0 /* cache stopped on I/O error */
+};
+
+extern void fscache_init_cache(struct fscache_cache *cache,
+ struct fscache_cache_ops *ops,
+ const char *idfmt,
+ ...) __attribute__ ((format (printf,3,4)));
+
+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);
+
+/*****************************************************************************/
+/*
+ * cache operations
+ */
+struct fscache_cache_ops {
+ /* name of cache provider */
+ const char *name;
+
+ /* look up the object for a cookie, creating it on disc if necessary */
+ struct fscache_object *(*lookup_object)(struct fscache_cache *cache,
+ struct fscache_object *parent,
+ struct fscache_cookie *cookie);
+
+ /* increment the usage count on this object (may fail if unmounting) */
+ struct fscache_object *(*grab_object)(struct fscache_object *object);
+
+ /* lock a semaphore on an object */
+ void (*lock_object)(struct fscache_object *object);
+
+ /* unlock a semaphore on an object */
+ void (*unlock_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);
+
+ /* store the updated auxilliary data on an object */
+ void (*update_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);
+
+ /* set the data size of an object */
+ int (*set_i_size)(struct fscache_object *object, loff_t i_size);
+
+ /* 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 */
+ int (*read_or_alloc_page)(struct fscache_object *object,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *context,
+ unsigned long gfp);
+
+ /* request backing blocks for a list of pages be read or allocated in
+ * the cache */
+ int (*read_or_alloc_pages)(struct fscache_object *object,
+ struct address_space *mapping,
+ struct list_head *pages,
+ unsigned *nr_pages,
+ fscache_rw_complete_t end_io_func,
+ void *context,
+ unsigned long gfp);
+
+ /* request a backing block for a page be allocated in the cache so that
+ * it can be written directly */
+ int (*allocate_page)(struct fscache_object *object,
+ struct page *page,
+ unsigned long gfp);
+
+ /* write a page to its backing block in the cache */
+ int (*write_page)(struct fscache_object *object,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *context,
+ unsigned long gfp);
+
+ /* write several pages to their backing blocks in the cache */
+ int (*write_pages)(struct fscache_object *object,
+ struct pagevec *pagevec,
+ fscache_rw_complete_t end_io_func,
+ void *context,
+ unsigned long gfp);
+
+ /* detach backing block from a bunch of pages */
+ void (*uncache_pages)(struct fscache_object *object,
+ struct pagevec *pagevec);
+
+ /* dissociate a cache from all the pages it was backing */
+ void (*dissociate_pages)(struct fscache_cache *cache);
+};
+
+/*****************************************************************************/
+/*
+ * data file or index object 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 disc space
+ * - indexes files are created on disc just-in-time
+ */
+struct fscache_cookie {
+ atomic_t usage; /* number of users of this cookie */
+ atomic_t children; /* number of children of this cookie */
+ struct rw_semaphore sem; /* list creation vs scan lock */
+ struct hlist_head backing_objects; /* object(s) backing this file/index */
+ struct fscache_cookie_def *def; /* definition */
+ struct fscache_cookie *parent; /* parent of this entry */
+ struct fscache_netfs *netfs; /* owner network fs definition */
+ void *netfs_data; /* back pointer to netfs */
+};
+
+extern struct fscache_cookie fscache_fsdef_index;
+
+/*****************************************************************************/
+/*
+ * on-disc cache file or index handle
+ */
+struct fscache_object {
+ unsigned long flags;
+#define FSCACHE_OBJECT_RELEASING 0 /* T if object is being released */
+#define FSCACHE_OBJECT_RECYCLING 1 /* T if object is being retired */
+#define FSCACHE_OBJECT_WITHDRAWN 2 /* T if object has been withdrawn */
+
+ 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 */
+};
+
+static inline
+void fscache_object_init(struct fscache_object *object)
+{
+ object->flags = 0;
+ INIT_LIST_HEAD(&object->cache_link);
+ INIT_HLIST_NODE(&object->cookie_link);
+ object->cache = NULL;
+ object->cookie = NULL;
+}
+
+/* find the parent index object for a object */
+static inline
+struct fscache_object *fscache_find_parent_object(struct fscache_object *object)
+{
+ struct fscache_object *parent;
+ struct fscache_cookie *cookie = object->cookie;
+ struct fscache_cache *cache = object->cache;
+ struct hlist_node *_p;
+
+ hlist_for_each_entry(parent, _p,
+ &cookie->parent->backing_objects,
+ cookie_link
+ ) {
+ if (parent->cache == cache)
+ return parent;
+ }
+
+ return NULL;
+}
+
+/* get an extra reference to a context */
+static inline
+void *fscache_get_context(struct fscache_cookie *cookie, void *context)
+{
+ if (cookie->def->get_context)
+ cookie->def->get_context(cookie->netfs_data, context);
+ return context;
+}
+
+/* release an extra reference to a context */
+static inline
+void fscache_put_context(struct fscache_cookie *cookie, void *context)
+{
+ if (cookie->def->put_context)
+ cookie->def->put_context(cookie->netfs_data, context);
+}
+
+#endif /* _LINUX_FSCACHE_CACHE_H */
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