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Annotation of 43BSDTahoe/sys/h/buf.h, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1982, 1986 Regents of the University of California.
        !             3:  * All rights reserved.  The Berkeley software License Agreement
        !             4:  * specifies the terms and conditions for redistribution.
        !             5:  *
        !             6:  *     @(#)buf.h       7.6 (Berkeley) 5/14/88
        !             7:  */
        !             8: 
        !             9: /*
        !            10:  * The header for buffers in the buffer pool and otherwise used
        !            11:  * to describe a block i/o request is given here.
        !            12:  *
        !            13:  * Each buffer in the pool is usually doubly linked into 2 lists:
        !            14:  * hashed into a chain by <dev,blkno> so it can be located in the cache,
        !            15:  * and (usually) on (one of several) queues.  These lists are circular and
        !            16:  * doubly linked for easy removal.
        !            17:  *
        !            18:  * There are currently three queues for buffers:
        !            19:  *     one for buffers which must be kept permanently (super blocks)
        !            20:  *     one for buffers containing ``useful'' information (the cache)
        !            21:  *     one for buffers containing ``non-useful'' information
        !            22:  *             (and empty buffers, pushed onto the front)
        !            23:  * The latter two queues contain the buffers which are available for
        !            24:  * reallocation, are kept in lru order.  When not on one of these queues,
        !            25:  * the buffers are ``checked out'' to drivers which use the available list
        !            26:  * pointers to keep track of them in their i/o active queues.
        !            27:  */
        !            28: 
        !            29: /*
        !            30:  * Bufhd structures used at the head of the hashed buffer queues.
        !            31:  * We only need three words for these, so this abbreviated
        !            32:  * definition saves some space.
        !            33:  */
        !            34: struct bufhd
        !            35: {
        !            36:        long    b_flags;                /* see defines below */
        !            37:        struct  buf *b_forw, *b_back;   /* fwd/bkwd pointer in chain */
        !            38: };
        !            39: struct buf
        !            40: {
        !            41:        long    b_flags;                /* too much goes here to describe */
        !            42:        struct  buf *b_forw, *b_back;   /* hash chain (2 way street) */
        !            43:        struct  buf *av_forw, *av_back; /* position on free list if not BUSY */
        !            44: #define        b_actf  av_forw                 /* alternate names for driver queue */
        !            45: #define        b_actl  av_back                 /*    head - isn't history wonderful */
        !            46:        long    b_bcount;               /* transfer count */
        !            47:        long    b_bufsize;              /* size of allocated buffer */
        !            48: #define        b_active b_bcount               /* driver queue head: drive active */
        !            49:        short   b_error;                /* returned after I/O */
        !            50:        dev_t   b_dev;                  /* major+minor device name */
        !            51:        union {
        !            52:            caddr_t b_addr;             /* low order core address */
        !            53:            int *b_words;               /* words for clearing */
        !            54:            struct fs *b_fs;            /* superblocks */
        !            55:            struct csum *b_cs;          /* superblock summary information */
        !            56:            struct cg *b_cg;            /* cylinder group block */
        !            57:            struct dinode *b_dino;      /* ilist */
        !            58:            daddr_t *b_daddr;           /* indirect block */
        !            59:        } b_un;
        !            60:        daddr_t b_blkno;                /* block # on device */
        !            61:        long    b_resid;                /* words not transferred after error */
        !            62: #define        b_errcnt b_resid                /* while i/o in progress: # retries */
        !            63:        struct  proc *b_proc;           /* proc doing physical or swap I/O */
        !            64:        int     (*b_iodone)();          /* function called by iodone */
        !            65:        int     b_pfcent;               /* center page when swapping cluster */
        !            66: };
        !            67: 
        !            68: #define        BQUEUES         4               /* number of free buffer queues */
        !            69: 
        !            70: #define        BQ_LOCKED       0               /* super-blocks &c */
        !            71: #define        BQ_LRU          1               /* lru, useful buffers */
        !            72: #define        BQ_AGE          2               /* rubbish */
        !            73: #define        BQ_EMPTY        3               /* buffer headers with no memory */
        !            74: 
        !            75: #ifdef KERNEL
        !            76: #define        BUFHSZ  512
        !            77: #define RND    (MAXBSIZE/DEV_BSIZE)
        !            78: #if    ((BUFHSZ&(BUFHSZ-1)) == 0)
        !            79: #define        BUFHASH(dev, dblkno)    \
        !            80:        ((struct buf *)&bufhash[((int)(dev)+(((int)(dblkno))/RND))&(BUFHSZ-1)])
        !            81: #else
        !            82: #define        BUFHASH(dev, dblkno)    \
        !            83:        ((struct buf *)&bufhash[((int)(dev)+(((int)(dblkno))/RND)) % BUFHSZ])
        !            84: #endif
        !            85: 
        !            86: struct buf *buf;               /* the buffer pool itself */
        !            87: char   *buffers;
        !            88: int    nbuf;                   /* number of buffer headers */
        !            89: int    bufpages;               /* number of memory pages in the buffer pool */
        !            90: struct buf *swbuf;             /* swap I/O headers */
        !            91: int    nswbuf;
        !            92: struct bufhd bufhash[BUFHSZ];  /* heads of hash lists */
        !            93: struct buf bfreelist[BQUEUES]; /* heads of available lists */
        !            94: struct buf bswlist;            /* head of free swap header list */
        !            95: struct buf *bclnlist;          /* head of cleaned page list */
        !            96: 
        !            97: struct buf *alloc();
        !            98: struct buf *realloccg();
        !            99: struct buf *baddr();
        !           100: struct buf *getblk();
        !           101: struct buf *geteblk();
        !           102: struct buf *getnewbuf();
        !           103: struct buf *bread();
        !           104: struct buf *breada();
        !           105: 
        !           106: unsigned minphys();
        !           107: #endif
        !           108: 
        !           109: /*
        !           110:  * These flags are kept in b_flags.
        !           111:  */
        !           112: #define        B_WRITE         0x000000        /* non-read pseudo-flag */
        !           113: #define        B_READ          0x000001        /* read when I/O occurs */
        !           114: #define        B_DONE          0x000002        /* transaction finished */
        !           115: #define        B_ERROR         0x000004        /* transaction aborted */
        !           116: #define        B_BUSY          0x000008        /* not on av_forw/back list */
        !           117: #define        B_PHYS          0x000010        /* physical IO */
        !           118: #define        B_XXX           0x000020        /* was B_MAP, alloc UNIBUS on pdp-11 */
        !           119: #define        B_WANTED        0x000040        /* issue wakeup when BUSY goes off */
        !           120: #define        B_AGE           0x000080        /* delayed write for correct aging */
        !           121: #define        B_ASYNC         0x000100        /* don't wait for I/O completion */
        !           122: #define        B_DELWRI        0x000200        /* write at exit of avail list */
        !           123: #define        B_TAPE          0x000400        /* this is a magtape (no bdwrite) */
        !           124: #define        B_UAREA         0x000800        /* add u-area to a swap operation */
        !           125: #define        B_PAGET         0x001000        /* page in/out of page table space */
        !           126: #define        B_DIRTY         0x002000        /* dirty page to be pushed out async */
        !           127: #define        B_PGIN          0x004000        /* pagein op, so swap() can count it */
        !           128: #define        B_CACHE         0x008000        /* did bread find us in the cache ? */
        !           129: #define        B_INVAL         0x010000        /* does not contain valid info  */
        !           130: #define        B_LOCKED        0x020000        /* locked in core (not reusable) */
        !           131: #define        B_HEAD          0x040000        /* a buffer header, not a buffer */
        !           132: #define        B_BAD           0x100000        /* bad block revectoring in progress */
        !           133: #define        B_CALL          0x200000        /* call b_iodone from iodone */
        !           134: #define        B_RAW           0x400000        /* set by physio for raw transfers */
        !           135: 
        !           136: /*
        !           137:  * Insq/Remq for the buffer hash lists.
        !           138:  */
        !           139: #define        bremhash(bp) { \
        !           140:        (bp)->b_back->b_forw = (bp)->b_forw; \
        !           141:        (bp)->b_forw->b_back = (bp)->b_back; \
        !           142: }
        !           143: #define        binshash(bp, dp) { \
        !           144:        (bp)->b_forw = (dp)->b_forw; \
        !           145:        (bp)->b_back = (dp); \
        !           146:        (dp)->b_forw->b_back = (bp); \
        !           147:        (dp)->b_forw = (bp); \
        !           148: }
        !           149: 
        !           150: /*
        !           151:  * Insq/Remq for the buffer free lists.
        !           152:  */
        !           153: #define        bremfree(bp) { \
        !           154:        (bp)->av_back->av_forw = (bp)->av_forw; \
        !           155:        (bp)->av_forw->av_back = (bp)->av_back; \
        !           156: }
        !           157: #define        binsheadfree(bp, dp) { \
        !           158:        (dp)->av_forw->av_back = (bp); \
        !           159:        (bp)->av_forw = (dp)->av_forw; \
        !           160:        (dp)->av_forw = (bp); \
        !           161:        (bp)->av_back = (dp); \
        !           162: }
        !           163: #define        binstailfree(bp, dp) { \
        !           164:        (dp)->av_back->av_forw = (bp); \
        !           165:        (bp)->av_back = (dp)->av_back; \
        !           166:        (dp)->av_back = (bp); \
        !           167:        (bp)->av_forw = (dp); \
        !           168: }
        !           169: 
        !           170: /*
        !           171:  * Take a buffer off the free list it's on and
        !           172:  * mark it as being use (B_BUSY) by a device.
        !           173:  */
        !           174: #define        notavail(bp) { \
        !           175:        int x = splbio(); \
        !           176:        bremfree(bp); \
        !           177:        (bp)->b_flags |= B_BUSY; \
        !           178:        splx(x); \
        !           179: }
        !           180: 
        !           181: #define        iodone  biodone
        !           182: #define        iowait  biowait
        !           183: 
        !           184: /*
        !           185:  * Zero out a buffer's data portion.
        !           186:  */
        !           187: #define        clrbuf(bp) { \
        !           188:        blkclr((bp)->b_un.b_addr, (unsigned)(bp)->b_bcount); \
        !           189:        (bp)->b_resid = 0; \
        !           190: }

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