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185 lines
6.8 KiB
185 lines
6.8 KiB
/*
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* Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
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* All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef __XFS_BEHAVIOR_H__
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#define __XFS_BEHAVIOR_H__
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/*
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* Header file used to associate behaviors with virtualized objects.
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*
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* A virtualized object is an internal, virtualized representation of
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* OS entities such as persistent files, processes, or sockets. Examples
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* of virtualized objects include vnodes, vprocs, and vsockets. Often
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* a virtualized object is referred to simply as an "object."
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*
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* A behavior is essentially an implementation layer associated with
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* an object. Multiple behaviors for an object are chained together,
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* the order of chaining determining the order of invocation. Each
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* behavior of a given object implements the same set of interfaces
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* (e.g., the VOP interfaces).
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*
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* Behaviors may be dynamically inserted into an object's behavior chain,
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* such that the addition is transparent to consumers that already have
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* references to the object. Typically, a given behavior will be inserted
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* at a particular location in the behavior chain. Insertion of new
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* behaviors is synchronized with operations-in-progress (oip's) so that
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* the oip's always see a consistent view of the chain.
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*
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* The term "interposition" is used to refer to the act of inserting
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* a behavior such that it interposes on (i.e., is inserted in front
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* of) a particular other behavior. A key example of this is when a
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* system implementing distributed single system image wishes to
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* interpose a distribution layer (providing distributed coherency)
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* in front of an object that is otherwise only accessed locally.
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*
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* Note that the traditional vnode/inode combination is simply a virtualized
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* object that has exactly one associated behavior.
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*
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* Behavior synchronization is logic which is necessary under certain
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* circumstances that there is no conflict between ongoing operations
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* traversing the behavior chain and those dynamically modifying the
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* behavior chain. Because behavior synchronization adds extra overhead
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* to virtual operation invocation, we want to restrict, as much as
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* we can, the requirement for this extra code, to those situations
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* in which it is truly necessary.
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*
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* Behavior synchronization is needed whenever there's at least one class
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* of object in the system for which:
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* 1) multiple behaviors for a given object are supported,
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* -- AND --
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* 2a) insertion of a new behavior can happen dynamically at any time during
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* the life of an active object,
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* -- AND --
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* 3a) insertion of a new behavior needs to synchronize with existing
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* ops-in-progress.
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* -- OR --
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* 3b) multiple different behaviors can be dynamically inserted at
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* any time during the life of an active object
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* -- OR --
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* 3c) removal of a behavior can occur at any time during the life of
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* an active object.
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* -- OR --
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* 2b) removal of a behavior can occur at any time during the life of an
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* active object
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*
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*/
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/*
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* Behavior head. Head of the chain of behaviors.
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* Contained within each virtualized object data structure.
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*/
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typedef struct bhv_head {
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struct bhv_desc *bh_first; /* first behavior in chain */
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} bhv_head_t;
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/*
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* Behavior descriptor. Descriptor associated with each behavior.
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* Contained within the behavior's private data structure.
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*/
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typedef struct bhv_desc {
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void *bd_pdata; /* private data for this behavior */
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void *bd_vobj; /* virtual object associated with */
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void *bd_ops; /* ops for this behavior */
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struct bhv_desc *bd_next; /* next behavior in chain */
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} bhv_desc_t;
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/*
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* Behavior identity field. A behavior's identity determines the position
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* where it lives within a behavior chain, and it's always the first field
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* of the behavior's ops vector. The optional id field further identifies the
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* subsystem responsible for the behavior.
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*/
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typedef struct bhv_identity {
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__u16 bi_id; /* owning subsystem id */
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__u16 bi_position; /* position in chain */
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} bhv_identity_t;
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typedef bhv_identity_t bhv_position_t;
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#define BHV_IDENTITY_INIT(id,pos) {id, pos}
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#define BHV_IDENTITY_INIT_POSITION(pos) BHV_IDENTITY_INIT(0, pos)
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/*
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* Define boundaries of position values.
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*/
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#define BHV_POSITION_INVALID 0 /* invalid position number */
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#define BHV_POSITION_BASE 1 /* base (last) implementation layer */
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#define BHV_POSITION_TOP 63 /* top (first) implementation layer */
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/*
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* Plumbing macros.
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*/
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#define BHV_HEAD_FIRST(bhp) (ASSERT((bhp)->bh_first), (bhp)->bh_first)
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#define BHV_NEXT(bdp) (ASSERT((bdp)->bd_next), (bdp)->bd_next)
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#define BHV_NEXTNULL(bdp) ((bdp)->bd_next)
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#define BHV_VOBJ(bdp) (ASSERT((bdp)->bd_vobj), (bdp)->bd_vobj)
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#define BHV_VOBJNULL(bdp) ((bdp)->bd_vobj)
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#define BHV_PDATA(bdp) (bdp)->bd_pdata
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#define BHV_OPS(bdp) (bdp)->bd_ops
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#define BHV_IDENTITY(bdp) ((bhv_identity_t *)(bdp)->bd_ops)
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#define BHV_POSITION(bdp) (BHV_IDENTITY(bdp)->bi_position)
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extern void bhv_head_init(bhv_head_t *, char *);
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extern void bhv_head_destroy(bhv_head_t *);
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extern int bhv_insert(bhv_head_t *, bhv_desc_t *);
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extern void bhv_insert_initial(bhv_head_t *, bhv_desc_t *);
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/*
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* Initialize a new behavior descriptor.
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* Arguments:
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* bdp - pointer to behavior descriptor
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* pdata - pointer to behavior's private data
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* vobj - pointer to associated virtual object
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* ops - pointer to ops for this behavior
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*/
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#define bhv_desc_init(bdp, pdata, vobj, ops) \
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{ \
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(bdp)->bd_pdata = pdata; \
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(bdp)->bd_vobj = vobj; \
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(bdp)->bd_ops = ops; \
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(bdp)->bd_next = NULL; \
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}
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/*
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* Remove a behavior descriptor from a behavior chain.
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*/
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#define bhv_remove(bhp, bdp) \
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{ \
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if ((bhp)->bh_first == (bdp)) { \
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/* \
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* Remove from front of chain. \
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* Atomic wrt oip's. \
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*/ \
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(bhp)->bh_first = (bdp)->bd_next; \
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} else { \
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/* remove from non-front of chain */ \
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bhv_remove_not_first(bhp, bdp); \
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} \
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(bdp)->bd_vobj = NULL; \
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}
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/*
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* Behavior module prototypes.
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*/
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extern void bhv_remove_not_first(bhv_head_t *bhp, bhv_desc_t *bdp);
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extern bhv_desc_t * bhv_lookup_range(bhv_head_t *bhp, int low, int high);
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extern bhv_desc_t * bhv_base(bhv_head_t *bhp);
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/* No bhv locking on Linux */
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#define bhv_base_unlocked bhv_base
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#endif /* __XFS_BEHAVIOR_H__ */
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