patch-2.4.25 linux-2.4.25/fs/xfs/xfs_behavior.h

• Lines: 205
• Date: 2004-02-18 05:36:32.000000000 -0800
• Orig file: linux-2.4.24/fs/xfs/xfs_behavior.h
• Orig date: 1969-12-31 16:00:00.000000000 -0800

diff -urN linux-2.4.24/fs/xfs/xfs_behavior.h linux-2.4.25/fs/xfs/xfs_behavior.h
@@ -0,0 +1,204 @@
+/*
+ * Copyright (c) 2000-2003 Silicon Graphics, Inc.  All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * Further, this software is distributed without any warranty that it is
+ * free of the rightful claim of any third person regarding infringement
+ * or the like.  Any license provided herein, whether implied or
+ * otherwise, applies only to this software file.  Patent licenses, if
+ * any, provided herein do not apply to combinations of this program with
+ * other software, or any other product whatsoever.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write the Free Software Foundation, Inc., 59
+ * Temple Place - Suite 330, Boston MA 02111-1307, USA.
+ *
+ * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
+ * Mountain View, CA  94043, or:
+ *
+ * http://www.sgi.com
+ *
+ * For further information regarding this notice, see:
+ *
+ * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
+ */
+#ifndef __XFS_BEHAVIOR_H__
+#define __XFS_BEHAVIOR_H__
+
+/*
+ * Header file used to associate behaviors with virtualized objects.
+ *
+ * A virtualized object is an internal, virtualized representation of
+ * OS entities such as persistent files, processes, or sockets.  Examples
+ * of virtualized objects include vnodes, vprocs, and vsockets.  Often
+ * a virtualized object is referred to simply as an "object."
+ *
+ * A behavior is essentially an implementation layer associated with
+ * an object.  Multiple behaviors for an object are chained together,
+ * the order of chaining determining the order of invocation.  Each
+ * behavior of a given object implements the same set of interfaces
+ * (e.g., the VOP interfaces).
+ *
+ * Behaviors may be dynamically inserted into an object's behavior chain,
+ * such that the addition is transparent to consumers that already have
+ * references to the object.  Typically, a given behavior will be inserted
+ * at a particular location in the behavior chain.  Insertion of new
+ * behaviors is synchronized with operations-in-progress (oip's) so that
+ * the oip's always see a consistent view of the chain.
+ *
+ * The term "interpostion" is used to refer to the act of inserting
+ * a behavior such that it interposes on (i.e., is inserted in front
+ * of) a particular other behavior.  A key example of this is when a
+ * system implementing distributed single system image wishes to
+ * interpose a distribution layer (providing distributed coherency)
+ * in front of an object that is otherwise only accessed locally.
+ *
+ * Note that the traditional vnode/inode combination is simply a virtualized
+ * object that has exactly one associated behavior.
+ *
+ * Behavior synchronization is logic which is necessary under certain
+ * circumstances that there is no conflict between ongoing operations
+ * traversing the behavior chain and those dunamically modifying the
+ * behavior chain.  Because behavior synchronization adds extra overhead
+ * to virtual operation invocation, we want to restrict, as much as
+ * we can, the requirement for this extra code, to those situations
+ * in which it is truly necessary.
+ *
+ * Behavior synchronization is needed whenever there's at least one class
+ * of object in the system for which:
+ * 1) multiple behaviors for a given object are supported,
+ * -- AND --
+ * 2a) insertion of a new behavior can happen dynamically at any time during
+ *     the life of an active object,
+ *	-- AND --
+ *	3a) insertion of a new behavior needs to synchronize with existing
+ *	    ops-in-progress.
+ *	-- OR --
+ *	3b) multiple different behaviors can be dynamically inserted at
+ *	    any time during the life of an active object
+ *	-- OR --
+ *	3c) removal of a behavior can occur at any time during the life of
+ *	    an active object.
+ * -- OR --
+ * 2b) removal of a behavior can occur at any time during the life of an
+ *     active object
+ *
+ */
+
+struct bhv_head_lock;
+
+/*
+ * Behavior head.  Head of the chain of behaviors.
+ * Contained within each virtualized object data structure.
+ */
+typedef struct bhv_head {
+	struct bhv_desc *bh_first;	/* first behavior in chain */
+	struct bhv_head_lock *bh_lockp;	/* pointer to lock info struct */
+} bhv_head_t;
+
+/*
+ * Behavior descriptor.	 Descriptor associated with each behavior.
+ * Contained within the behavior's private data structure.
+ */
+typedef struct bhv_desc {
+	void		*bd_pdata;	/* private data for this behavior */
+	void		*bd_vobj;	/* virtual object associated with */
+	void		*bd_ops;	/* ops for this behavior */
+	struct bhv_desc *bd_next;	/* next behavior in chain */
+} bhv_desc_t;
+
+/*
+ * Behavior identity field.  A behavior's identity determines the position
+ * where it lives within a behavior chain, and it's always the first field
+ * of the behavior's ops vector. The optional id field further identifies the
+ * subsystem responsible for the behavior.
+ */
+typedef struct bhv_identity {
+	__u16	bi_id;		/* owning subsystem id */
+	__u16	bi_position;	/* position in chain */
+} bhv_identity_t;
+
+typedef bhv_identity_t bhv_position_t;
+
+#define BHV_IDENTITY_INIT(id,pos)	{id, pos}
+#define BHV_IDENTITY_INIT_POSITION(pos) BHV_IDENTITY_INIT(0, pos)
+
+/*
+ * Define boundaries of position values.
+ */
+#define BHV_POSITION_INVALID	0	/* invalid position number */
+#define BHV_POSITION_BASE	1	/* base (last) implementation layer */
+#define BHV_POSITION_TOP	63	/* top (first) implementation layer */
+
+/*
+ * Plumbing macros.
+ */
+#define BHV_HEAD_FIRST(bhp)	(ASSERT((bhp)->bh_first), (bhp)->bh_first)
+#define BHV_NEXT(bdp)		(ASSERT((bdp)->bd_next), (bdp)->bd_next)
+#define BHV_NEXTNULL(bdp)	((bdp)->bd_next)
+#define BHV_VOBJ(bdp)		(ASSERT((bdp)->bd_vobj), (bdp)->bd_vobj)
+#define BHV_VOBJNULL(bdp)	((bdp)->bd_vobj)
+#define BHV_PDATA(bdp)		(bdp)->bd_pdata
+#define BHV_OPS(bdp)		(bdp)->bd_ops
+#define BHV_IDENTITY(bdp)	((bhv_identity_t *)(bdp)->bd_ops)
+#define BHV_POSITION(bdp)	(BHV_IDENTITY(bdp)->bi_position)
+
+extern void bhv_head_init(bhv_head_t *, char *);
+extern void bhv_head_destroy(bhv_head_t *);
+extern int  bhv_insert(bhv_head_t *, bhv_desc_t *);
+extern void bhv_insert_initial(bhv_head_t *, bhv_desc_t *);
+
+/*
+ * Initialize a new behavior descriptor.
+ * Arguments:
+ *   bdp - pointer to behavior descriptor
+ *   pdata - pointer to behavior's private data
+ *   vobj - pointer to associated virtual object
+ *   ops - pointer to ops for this behavior
+ */
+#define bhv_desc_init(bdp, pdata, vobj, ops)		\
+ {							\
+	(bdp)->bd_pdata = pdata;			\
+	(bdp)->bd_vobj = vobj;				\
+	(bdp)->bd_ops = ops;				\
+	(bdp)->bd_next = NULL;				\
+ }
+
+/*
+ * Remove a behavior descriptor from a behavior chain.
+ */
+#define bhv_remove(bhp, bdp)				\
+ {							\
+	if ((bhp)->bh_first == (bdp)) {			\
+		/*					\
+		* Remove from front of chain.		\
+		* Atomic wrt oip's.			\
+		*/					\
+	       (bhp)->bh_first = (bdp)->bd_next;	\
+	} else {					\
+	       /* remove from non-front of chain */	\
+	       bhv_remove_not_first(bhp, bdp);		\
+	}						\
+	(bdp)->bd_vobj = NULL;				\
+ }
+
+/*
+ * Behavior module prototypes.
+ */
+extern void		bhv_remove_not_first(bhv_head_t *bhp, bhv_desc_t *bdp);
+extern bhv_desc_t *	bhv_lookup(bhv_head_t *bhp, void *ops);
+extern bhv_desc_t *	bhv_lookup_range(bhv_head_t *bhp, int low, int high);
+extern bhv_desc_t *	bhv_base(bhv_head_t *bhp);
+
+/* No bhv locking on Linux */
+#define bhv_lookup_unlocked	bhv_lookup
+#define bhv_base_unlocked	bhv_base
+
+#endif /* __XFS_BEHAVIOR_H__ */