4.3BSD - /usr/src/sys/h/buf.h

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

Defined variables

Defined struct's

Defined macros

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