2.11BSD#431 - /usr/src/sys/h/buf.h

   1: /*
   2:  * Copyright (c) 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	1.4 (2.11BSD GTE) 1996/9/13
   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 two queues for buffers:
  19:  * 	one for buffers containing ``useful'' information (the cache)
  20:  *	one for buffers containing ``non-useful'' information
  21:  *		(and empty buffers, pushed onto the front)
  22:  * These queues contain the buffers which are available for
  23:  * reallocation, are kept in lru order.  When not on one of these queues,
  24:  * the buffers are ``checked out'' to drivers which use the available list
  25:  * pointers to keep track of them in their i/o active queues.
  26:  */
  27: 
  28: /*
  29:  * Bufhd structures used at the head of the hashed buffer queues.
  30:  * We only need three words for these, so this abbreviated
  31:  * definition saves some space.
  32:  */
  33: struct bufhd
  34: {
  35:     short   b_flags;        /* see defines below */
  36:     struct  buf *b_forw, *b_back;   /* fwd/bkwd pointer in chain */
  37: };
  38: struct buf
  39: {
  40:     short   b_flags;        /* see defines below */
  41:     struct  buf *b_forw, *b_back;   /* hash chain (2 way street) */
  42:     struct  buf *av_forw, *av_back; /* position on free list if not BUSY */
  43: #define b_actf  av_forw         /* alternate names for driver queue */
  44: #define b_actl  av_back         /*    head - isn't history wonderful */
  45:     u_short b_bcount;       /* transfer count */
  46: #define b_active b_bcount       /* driver queue head: drive active */
  47:     char    b_error;        /* returned after I/O */
  48:     char    b_xmem;         /* high order core address */
  49:     dev_t   b_dev;          /* major+minor device name */
  50:     union {
  51:         caddr_t b_addr;     /* low order core address */
  52:     } b_un;
  53:     daddr_t b_blkno;        /* block # on device */
  54:     u_short b_resid;        /* words not transferred after error */
  55: #define b_cylin b_resid         /* disksort */
  56: #define b_errcnt b_resid        /* while i/o in progress: # retries */
  57: };
  58: 
  59: /*
  60:  * We never use BQ_LOCKED or BQ_EMPTY, but if you want the 4.X block I/O
  61:  * code to drop in, you have to have BQ_AGE and BQ_LRU *after* the first
  62:  * queue, and it only costs 6 bytes of data space.
  63:  */
  64: #define BQUEUES     3       /* number of free buffer queues */
  65: 
  66: #define BQ_LOCKED   0       /* super-blocks &c */
  67: #define BQ_LRU      1       /* lru, useful buffers */
  68: #define BQ_AGE      2       /* rubbish */
  69: #define BQ_EMPTY    3       /* buffer headers with no memory */
  70: 
  71: /* Flags to low-level allocation routines. */
  72: #define B_CLRBUF    0x01    /* Request allocated buffer be cleared. */
  73: #define B_SYNC      0x02    /* Do all allocations synchronously. */
  74: 
  75: #define bawrite(bp) {(bp)->b_flags |= B_ASYNC; bwrite(bp);}
  76: #define bfree(bp)   (bp)->b_bcount = 0
  77: #define bftopaddr(bp)   ((u_int)(bp)->b_un.b_addr >> 6 | (bp)->b_xmem << 10)
  78: 
  79: #if defined(KERNEL) && !defined(SUPERVISOR)
  80: #define BUFHSZ  16  /* must be power of 2 */
  81: #define BUFHASH(dev,blkno)  ((struct buf *)&bufhash[((long)(dev) + blkno) & ((long)(BUFHSZ - 1))])
  82: extern struct   buf buf[];      /* the buffer pool itself */
  83: extern int  nbuf;           /* number of buffer headers */
  84: extern struct   bufhd bufhash[];    /* heads of hash lists */
  85: extern struct   buf bfreelist[];    /* heads of available lists */
  86: 
  87: struct  buf *balloc();
  88: struct  buf *getblk();
  89: struct  buf *geteblk();
  90: struct  buf *getnewbuf();
  91: struct  buf *bread();
  92: struct  buf *breada();
  93: #endif
  94: 
  95: /*
  96:  * These flags are kept in b_flags.
  97:  */
  98: #define B_WRITE     0x00000     /* non-read pseudo-flag */
  99: #define B_READ      0x00001     /* read when I/O occurs */
 100: #define B_DONE      0x00002     /* transaction finished */
 101: #define B_ERROR     0x00004     /* transaction aborted */
 102: #define B_BUSY      0x00008     /* not on av_forw/back list */
 103: #define B_PHYS      0x00010     /* physical IO */
 104: #define B_MAP       0x00020     /* alloc UNIBUS */
 105: #define B_WANTED    0x00040     /* issue wakeup when BUSY goes off */
 106: #define B_AGE       0x00080     /* delayed write for correct aging */
 107: #define B_ASYNC     0x00100     /* don't wait for I/O completion */
 108: #define B_DELWRI    0x00200     /* write at exit of avail list */
 109: #define B_TAPE      0x00400     /* this is a magtape (no bdwrite) */
 110: #define B_INVAL     0x00800     /* does not contain valid info */
 111: #define B_BAD       0x01000     /* bad block revectoring in progress */
 112: #define B_LOCKED    0x02000     /* locked in core (not reusable) */
 113: #define B_UBAREMAP  0x04000     /* addr UNIBUS virtual, not physical */
 114: #define B_RAMREMAP  0x08000     /* remapped into ramdisk */
 115: 
 116: /*
 117:  * Insq/Remq for the buffer hash lists.
 118:  */
 119: #define bremhash(bp) { \
 120:     (bp)->b_back->b_forw = (bp)->b_forw; \
 121:     (bp)->b_forw->b_back = (bp)->b_back; \
 122: }
 123: #define binshash(bp, dp) { \
 124:     (bp)->b_forw = (dp)->b_forw; \
 125:     (bp)->b_back = (dp); \
 126:     (dp)->b_forw->b_back = (bp); \
 127:     (dp)->b_forw = (bp); \
 128: }
 129: 
 130: /*
 131:  * Insq/Remq for the buffer free lists.
 132:  */
 133: #define bremfree(bp) { \
 134:     (bp)->av_back->av_forw = (bp)->av_forw; \
 135:     (bp)->av_forw->av_back = (bp)->av_back; \
 136: }
 137: #define binsheadfree(bp, dp) { \
 138:     (dp)->av_forw->av_back = (bp); \
 139:     (bp)->av_forw = (dp)->av_forw; \
 140:     (dp)->av_forw = (bp); \
 141:     (bp)->av_back = (dp); \
 142: }
 143: #define binstailfree(bp, dp) { \
 144:     (dp)->av_back->av_forw = (bp); \
 145:     (bp)->av_back = (dp)->av_back; \
 146:     (dp)->av_back = (bp); \
 147:     (bp)->av_forw = (dp); \
 148: }
 149: 
 150: /*
 151:  * Take a buffer off the free list it's on and
 152:  * mark it as being use (B_BUSY) by a device.
 153:  */
 154: #define notavail(bp) { \
 155:     register int x = splbio(); \
 156:     bremfree(bp); \
 157:     (bp)->b_flags |= B_BUSY; \
 158:     splx(x); \
 159: }
 160: 
 161: #define iodone  biodone
 162: #define iowait  biowait

Defined struct's

Defined macros

Usage of this include