FreeBSD/Linux Kernel Cross Reference
sys/sys/bufobj.h

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2004 Poul-Henning Kamp
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD: releng/12.0/sys/sys/bufobj.h 329612 2018-02-20 00:06:07Z jeff $
     */
    
    /*
     * Architectural notes:
     *
     * bufobj is a new object which is what buffers hang from in the buffer
     * cache.
     *
     * This used to be vnodes, but we need non-vnode code to be able
     * to use the buffer cache as well, specifically geom classes like gbde,
     * raid3 and raid5.
     *
     * All vnodes will contain a bufobj initially, but down the road we may
     * want to only allocate bufobjs when they are needed.  There could be a
     * large number of vnodes in the system which wouldn't need a bufobj during
     * their lifetime.
     *
     * The exact relationship to the vmobject is not determined at this point,
     * it may in fact be that we find them to be two sides of the same object 
     * once things starts to crystalize.
     */
    
    #ifndef _SYS_BUFOBJ_H_
    #define _SYS_BUFOBJ_H_
    
    #if defined(_KERNEL) || defined(_KVM_VNODE)
    
    #include <sys/queue.h>
    #include <sys/_lock.h>
    #include <sys/_rwlock.h>
    #include <sys/_pctrie.h>
    
    struct bufobj;
    struct buf_ops;
    
    extern struct buf_ops buf_ops_bio;
    
    TAILQ_HEAD(buflists, buf);
    
    /* A Buffer list & trie */
    struct bufv {
            struct buflists bv_hd;          /* Sorted blocklist */
            struct pctrie   bv_root;        /* Buf trie */
            int             bv_cnt;         /* Number of buffers */
    };
    
    typedef void b_strategy_t(struct bufobj *, struct buf *);
    typedef int b_write_t(struct buf *);
    typedef int b_sync_t(struct bufobj *, int waitfor);
    typedef void b_bdflush_t(struct bufobj *, struct buf *);
    
    struct buf_ops {
            char            *bop_name;
            b_write_t       *bop_write;
            b_strategy_t    *bop_strategy;
            b_sync_t        *bop_sync;
            b_bdflush_t     *bop_bdflush;
    };
    
    #define BO_STRATEGY(bo, bp)     ((bo)->bo_ops->bop_strategy((bo), (bp)))
    #define BO_SYNC(bo, w)          ((bo)->bo_ops->bop_sync((bo), (w)))
    #define BO_WRITE(bo, bp)        ((bo)->bo_ops->bop_write((bp)))
    #define BO_BDFLUSH(bo, bp)      ((bo)->bo_ops->bop_bdflush((bo), (bp)))
    
    /*
     * Locking notes:
     * 'S' is sync_mtx
     * 'v' is the vnode lock which embeds the bufobj.
     * '-' Constant and unchanging after initialization.
     */
    struct bufobj {
           struct rwlock   bo_lock;        /* Lock which protects "i" things */
           struct buf_ops  *bo_ops;        /* - Buffer operations */
           struct vm_object *bo_object;    /* v Place to store VM object */
           LIST_ENTRY(bufobj) bo_synclist; /* S dirty vnode list */
           void            *bo_private;    /* private pointer */
           struct bufv     bo_clean;       /* i Clean buffers */
           struct bufv     bo_dirty;       /* i Dirty buffers */
           long            bo_numoutput;   /* i Writes in progress */
           u_int           bo_flag;        /* i Flags */
           int             bo_domain;      /* - Clean queue affinity */
           int             bo_bsize;       /* - Block size for i/o */
   };
   
   /*
    * XXX BO_ONWORKLST could be replaced with a check for NULL list elements
    * in v_synclist.
    */
   #define BO_ONWORKLST    (1 << 0)        /* On syncer work-list */
   #define BO_WWAIT        (1 << 1)        /* Wait for output to complete */
   #define BO_DEAD         (1 << 2)        /* Dead; only with INVARIANTS */
   
   #define BO_LOCKPTR(bo)          (&(bo)->bo_lock)
   #define BO_LOCK(bo)             rw_wlock(BO_LOCKPTR((bo)))
   #define BO_UNLOCK(bo)           rw_wunlock(BO_LOCKPTR((bo)))
   #define BO_RLOCK(bo)            rw_rlock(BO_LOCKPTR((bo)))
   #define BO_RUNLOCK(bo)          rw_runlock(BO_LOCKPTR((bo)))
   #define ASSERT_BO_WLOCKED(bo)   rw_assert(BO_LOCKPTR((bo)), RA_WLOCKED)
   #define ASSERT_BO_LOCKED(bo)    rw_assert(BO_LOCKPTR((bo)), RA_LOCKED)
   #define ASSERT_BO_UNLOCKED(bo)  rw_assert(BO_LOCKPTR((bo)), RA_UNLOCKED)
   
   void bufobj_init(struct bufobj *bo, void *private);
   void bufobj_wdrop(struct bufobj *bo);
   void bufobj_wref(struct bufobj *bo);
   void bufobj_wrefl(struct bufobj *bo);
   int bufobj_invalbuf(struct bufobj *bo, int flags, int slpflag, int slptimeo);
   int bufobj_wwait(struct bufobj *bo, int slpflag, int timeo);
   int bufsync(struct bufobj *bo, int waitfor);
   void bufbdflush(struct bufobj *bo, struct buf *bp);
   
   #endif /* defined(_KERNEL) || defined(_KVM_VNODE) */
   #endif /* _SYS_BUFOBJ_H_ */

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