fscache: Attach the index key and aux data to the cookie

Attach copies of the index key and auxiliary data to the fscache cookie so
that:

 (1) The callbacks to the netfs for this stuff can be eliminated.  This
     can simplify things in the cache as the information is still
     available, even after the cache has relinquished the cookie.

 (2) Simplifies the locking requirements of accessing the information as we
     don't have to worry about the netfs object going away on us.

 (3) The cache can do lazy updating of the coherency information on disk.
     As long as the cache is flushed before reboot/poweroff, there's no
     need to update the coherency info on disk every time it changes.

 (4) Cookies can be hashed or put in a tree as the index key is easily
     available.  This allows:

     (a) Checks for duplicate cookies can be made at the top fscache layer
     	 rather than down in the bowels of the cache backend.

     (b) Caching can be added to a netfs object that has a cookie if the
     	 cache is brought online after the netfs object is allocated.

A certain amount of space is made in the cookie for inline copies of the
data, but if it won't fit there, extra memory will be allocated for it.

The downside of this is that live cache operation requires more memory.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Anna Schumaker <anna.schumaker@netapp.com>
Tested-by: Steve Dickson <steved@redhat.com>

1 files changed, 65 insertions, 45 deletions

diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index fe0c349684fa..a2d3a2116248 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -83,17 +83,6 @@ struct fscache_cookie_def {
 		const void *parent_netfs_data,
 		const void *cookie_netfs_data);
 
-	/* get an index key
-	 * - should store the key data in the buffer
-	 * - should return the amount of data stored
-	 * - not permitted to return an error
-	 * - the netfs data from the cookie being used as the source is
-	 *   presented
-	 */
-	uint16_t (*get_key)(const void *cookie_netfs_data,
-			    void *buffer,
-			    uint16_t bufmax);
-
 	/* get certain file attributes from the netfs data
 	 * - this function can be absent for an index
 	 * - not permitted to return an error
@@ -102,18 +91,6 @@ struct fscache_cookie_def {
 	 */
 	void (*get_attr)(const void *cookie_netfs_data, uint64_t *size);
 
-	/* get the auxiliary data from netfs data
-	 * - this function can be absent if the index carries no state data
-	 * - should store the auxiliary data in the buffer
-	 * - should return the amount of amount stored
-	 * - not permitted to return an error
-	 * - the netfs data from the cookie being used as the source is
-	 *   presented
-	 */
-	uint16_t (*get_aux)(const void *cookie_netfs_data,
-			    void *buffer,
-			    uint16_t bufmax);
-
 	/* consult the netfs about the state of an object
 	 * - this function can be absent if the index carries no state data
 	 * - the netfs data from the cookie being used as the target is
@@ -186,6 +163,19 @@ struct fscache_cookie {
 #define FSCACHE_COOKIE_RELINQUISHED	4	/* T if cookie has been relinquished */
 #define FSCACHE_COOKIE_ENABLED		5	/* T if cookie is enabled */
 #define FSCACHE_COOKIE_ENABLEMENT_LOCK	6	/* T if cookie is being en/disabled */
+#define FSCACHE_COOKIE_AUX_UPDATED	7	/* T if the auxiliary data was updated */
+
+	u8				type;		/* Type of object */
+	u8				key_len;	/* Length of index key */
+	u8				aux_len;	/* Length of auxiliary data */
+	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 */
+	};
 };
 
 static inline bool fscache_cookie_enabled(struct fscache_cookie *cookie)
@@ -208,10 +198,12 @@ extern void __fscache_release_cache_tag(struct fscache_cache_tag *);
 extern struct fscache_cookie *__fscache_acquire_cookie(
 	struct fscache_cookie *,
 	const struct fscache_cookie_def *,
+	const void *, size_t,
+	const void *, size_t,
 	void *, bool);
-extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool);
-extern int __fscache_check_consistency(struct fscache_cookie *);
-extern void __fscache_update_cookie(struct fscache_cookie *);
+extern void __fscache_relinquish_cookie(struct fscache_cookie *, const void *, bool);
+extern int __fscache_check_consistency(struct fscache_cookie *, const void *);
+extern void __fscache_update_cookie(struct fscache_cookie *, const void *);
 extern int __fscache_attr_changed(struct fscache_cookie *);
 extern void __fscache_invalidate(struct fscache_cookie *);
 extern void __fscache_wait_on_invalidate(struct fscache_cookie *);
@@ -238,8 +230,8 @@ extern void __fscache_uncache_all_inode_pages(struct fscache_cookie *,
 					      struct inode *);
 extern void __fscache_readpages_cancel(struct fscache_cookie *cookie,
 				       struct list_head *pages);
-extern void __fscache_disable_cookie(struct fscache_cookie *, bool);
-extern void __fscache_enable_cookie(struct fscache_cookie *,
+extern void __fscache_disable_cookie(struct fscache_cookie *, const void *, bool);
+extern void __fscache_enable_cookie(struct fscache_cookie *, const void *,
 				    bool (*)(void *), void *);
 
 /**
@@ -317,6 +309,10 @@ void fscache_release_cache_tag(struct fscache_cache_tag *tag)
  * fscache_acquire_cookie - Acquire a cookie to represent a cache object
  * @parent: The cookie that's to be the parent of this one
  * @def: A description of the cache object, including callback operations
+ * @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
  * @netfs_data: An arbitrary piece of data to be kept in the cookie to
  * represent the cache object to the netfs
  * @enable: Whether or not to enable a data cookie immediately
@@ -332,12 +328,18 @@ static inline
 struct fscache_cookie *fscache_acquire_cookie(
 	struct fscache_cookie *parent,
 	const struct fscache_cookie_def *def,
+	const void *index_key,
+	size_t index_key_len,
+	const void *aux_data,
+	size_t aux_data_len,
 	void *netfs_data,
 	bool enable)
 {
 	if (fscache_cookie_valid(parent) && fscache_cookie_enabled(parent))
-		return __fscache_acquire_cookie(parent, def, netfs_data,
-						enable);
+		return __fscache_acquire_cookie(parent, def,
+						index_key, index_key_len,
+						aux_data, aux_data_len,
+						netfs_data, enable);
 	else
 		return NULL;
 }
@@ -346,36 +348,44 @@ struct fscache_cookie *fscache_acquire_cookie(
  * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding
  * it
  * @cookie: The cookie being returned
+ * @aux_data: The updated auxiliary data for the cookie (may be NULL)
  * @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.
+ * associated cache object if retire is set to true.  The opportunity is
+ * provided to update the auxiliary data in the cache before the object is
+ * disconnected.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
-void fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
+void fscache_relinquish_cookie(struct fscache_cookie *cookie,
+			       const void *aux_data,
+			       bool retire)
 {
 	if (fscache_cookie_valid(cookie))
-		__fscache_relinquish_cookie(cookie, retire);
+		__fscache_relinquish_cookie(cookie, aux_data, retire);
 }
 
 /**
- * fscache_check_consistency - Request that if the cache is updated
+ * fscache_check_consistency - Request validation of a cache's auxiliary data
  * @cookie: The cookie representing the cache object
+ * @aux_data: The updated auxiliary data for the cookie (may be NULL)
  *
- * Request an consistency check from fscache, which passes the request
- * to the backing cache.
+ * Request an consistency check from fscache, which passes the request to the
+ * backing cache.  The auxiliary data on the cookie will be updated first if
+ * @aux_data is set.
  *
  * Returns 0 if consistent and -ESTALE if inconsistent.  May also
  * return -ENOMEM and -ERESTARTSYS.
  */
 static inline
-int fscache_check_consistency(struct fscache_cookie *cookie)
+int fscache_check_consistency(struct fscache_cookie *cookie,
+			      const void *aux_data)
 {
 	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
-		return __fscache_check_consistency(cookie);
+		return __fscache_check_consistency(cookie, aux_data);
 	else
 		return 0;
 }
@@ -383,18 +393,20 @@ int fscache_check_consistency(struct fscache_cookie *cookie)
 /**
  * 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)
  *
  * Request an update of the index data for the cache object associated with the
- * cookie.
+ * cookie.  The auxiliary data on the cookie will be updated first if @aux_data
+ * is set.
  *
  * See Documentation/filesystems/caching/netfs-api.txt for a complete
  * description.
  */
 static inline
-void fscache_update_cookie(struct fscache_cookie *cookie)
+void fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data)
 {
 	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
-		__fscache_update_cookie(cookie);
+		__fscache_update_cookie(cookie, aux_data);
 }
 
 /**
@@ -780,6 +792,7 @@ void fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
 /**
  * fscache_disable_cookie - Disable a cookie
  * @cookie: The cookie representing the cache object
+ * @aux_data: The updated auxiliary data for the cookie (may be NULL)
  * @invalidate: Invalidate the backing object
  *
  * Disable a cookie from accepting further alloc, read, write, invalidate,
@@ -790,34 +803,41 @@ void fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
  *
  * If @invalidate is set, then the backing object will be invalidated and
  * detached, otherwise it will just be detached.
+ *
+ * If @aux_data is set, then auxiliary data will be updated from that.
  */
 static inline
-void fscache_disable_cookie(struct fscache_cookie *cookie, bool invalidate)
+void fscache_disable_cookie(struct fscache_cookie *cookie,
+			    const void *aux_data,
+			    bool invalidate)
 {
 	if (fscache_cookie_valid(cookie) && fscache_cookie_enabled(cookie))
-		__fscache_disable_cookie(cookie, invalidate);
+		__fscache_disable_cookie(cookie, aux_data, invalidate);
 }
 
 /**
  * fscache_enable_cookie - Reenable a cookie
  * @cookie: The cookie representing the cache object
+ * @aux_data: The updated auxiliary data for the cookie (may be NULL)
  * @can_enable: A function to permit enablement once lock is held
  * @data: Data for can_enable()
  *
  * Reenable a previously disabled cookie, allowing it to accept further alloc,
  * read, write, invalidate, update or acquire operations.  An attempt will be
- * made to immediately reattach the cookie to a backing object.
+ * made to immediately reattach the cookie to a backing object.  If @aux_data
+ * is set, the auxiliary data attached to the cookie will be updated.
  *
  * The can_enable() function is called (if not NULL) once the enablement lock
  * is held to rule on whether enablement is still permitted to go ahead.
  */
 static inline
 void fscache_enable_cookie(struct fscache_cookie *cookie,
+			   const void *aux_data,
 			   bool (*can_enable)(void *data),
 			   void *data)
 {
 	if (fscache_cookie_valid(cookie) && !fscache_cookie_enabled(cookie))
-		__fscache_enable_cookie(cookie, can_enable, data);
+		__fscache_enable_cookie(cookie, aux_data, can_enable, data);
 }
 
 #endif /* _LINUX_FSCACHE_H */