X-Git-Url: http://git.onelab.eu/?p=linux-2.6.git;a=blobdiff_plain;f=include%2Flinux%2Ffscache-cache.h;fp=include%2Flinux%2Ffscache-cache.h;h=e229fed0096dcec7ffb7b70f6fef0b2c2aa83c69;hp=0000000000000000000000000000000000000000;hb=f05f9504c50ed069377d37f02f22e7a16b5921de;hpb=16c70f8c1b54b61c3b951b6fb220df250fe09b32

diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
new file mode 100644
index 000000000..e229fed00
--- /dev/null
+++ b/include/linux/fscache-cache.h
@@ -0,0 +1,243 @@
+/* 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 */