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/*
* Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
* All Rights Reserved.
*
* 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.
*
* 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. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#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 "interposition" 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 dynamically 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
*
*/
/*
* 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 */
} 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_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_base_unlocked bhv_base
#endif /* __XFS_BEHAVIOR_H__ */
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