| /* | |
| * 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__ */ |