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1.1 root 1: /* buf.h 6.1 83/07/29 */
2:
3: /*
4: * The header for buffers in the buffer pool and otherwise used
5: * to describe a block i/o request is given here. The routines
6: * which manipulate these things are given in bio.c.
7: *
8: * Each buffer in the pool is usually doubly linked into 2 lists:
9: * hashed into a chain by <dev,blkno> so it can be located in the cache,
10: * and (usually) on (one of several) queues. These lists are circular and
11: * doubly linked for easy removal.
12: *
13: * There are currently three queues for buffers:
14: * one for buffers which must be kept permanently (super blocks)
15: * one for buffers containing ``useful'' information (the cache)
16: * one for buffers containing ``non-useful'' information
17: * (and empty buffers, pushed onto the front)
18: * The latter two queues contain the buffers which are available for
19: * reallocation, are kept in lru order. When not on one of these queues,
20: * the buffers are ``checked out'' to drivers which use the available list
21: * pointers to keep track of them in their i/o active queues.
22: */
23:
24: /*
25: * Bufhd structures used at the head of the hashed buffer queues.
26: * We only need three words for these, so this abbreviated
27: * definition saves some space.
28: */
29: struct bufhd
30: {
31: long b_flags; /* see defines below */
32: struct buf *b_forw, *b_back; /* fwd/bkwd pointer in chain */
33: };
34: struct buf
35: {
36: long b_flags; /* too much goes here to describe */
37: struct buf *b_forw, *b_back; /* hash chain (2 way street) */
38: struct buf *av_forw, *av_back; /* position on free list if not BUSY */
39: #define b_actf av_forw /* alternate names for driver queue */
40: #define b_actl av_back /* head - isn't history wonderful */
41: long b_bcount; /* transfer count */
42: long b_bufsize; /* size of allocated buffer */
43: #define b_active b_bcount /* driver queue head: drive active */
44: short b_error; /* returned after I/O */
45: dev_t b_dev; /* major+minor device name */
46: union {
47: caddr_t b_addr; /* low order core address */
48: int *b_words; /* words for clearing */
49: struct fs *b_fs; /* superblocks */
50: struct csum *b_cs; /* superblock summary information */
51: struct cg *b_cg; /* cylinder group block */
52: struct dinode *b_dino; /* ilist */
53: daddr_t *b_daddr; /* indirect block */
54: } b_un;
55: daddr_t b_blkno; /* block # on device */
56: long b_resid; /* words not transferred after error */
57: #define b_errcnt b_resid /* while i/o in progress: # retries */
58: struct proc *b_proc; /* proc doing physical or swap I/O */
59: int (*b_iodone)(); /* function called by iodone */
60: int b_pfcent; /* center page when swapping cluster */
61: #define MAXBPTE 32 /* max no. of pte's in buffer (>=KLMAX) */
62: long b_upte[MAXBPTE+1]; /* user pte's for swap/raw I/O */
63: int b_ptecnt; /* number of user pte's in b_upte */
64: };
65:
66: #define BQUEUES 4 /* number of free buffer queues */
67:
68: #define BQ_LOCKED 0 /* super-blocks &c */
69: #define BQ_LRU 1 /* lru, useful buffers */
70: #define BQ_AGE 2 /* rubbish */
71: #define BQ_EMPTY 3 /* buffer headers with no memory */
72:
73: #ifdef KERNEL
74: #define BUFHSZ 63
75: #define RND (MAXBSIZE/DEV_BSIZE)
76: #define BUFHASH(dev, dblkno) \
77: ((struct buf *)&bufhash[((int)(dev)+(((int)(dblkno))/RND)) % BUFHSZ])
78:
79: struct buf *buf; /* the buffer pool itself */
80: char *buffers;
81: int nbuf; /* number of buffer headers */
82: int bufpages; /* number of memory pages in the buffer pool */
83: struct buf *swbuf; /* swap I/O headers */
84: int nswbuf;
85: struct bufhd bufhash[BUFHSZ]; /* heads of hash lists */
86: struct buf bfreelist[BQUEUES]; /* heads of available lists */
87: struct buf bswlist; /* head of free swap header list */
88: struct buf *bclnlist; /* head of cleaned page list */
89:
90: struct buf *alloc();
91: struct buf *realloccg();
92: struct buf *baddr();
93: struct buf *getblk();
94: struct buf *geteblk();
95: struct buf *getnewbuf();
96: struct buf *bread();
97: struct buf *breada();
98:
99: unsigned minphys();
100: #endif
101:
102: /*
103: * These flags are kept in b_flags.
104: */
105: #define B_WRITE 0x000000 /* non-read pseudo-flag */
106: #define B_READ 0x000001 /* read when I/O occurs */
107: #define B_DONE 0x000002 /* transaction finished */
108: #define B_ERROR 0x000004 /* transaction aborted */
109: #define B_BUSY 0x000008 /* not on av_forw/back list */
110: #define B_PHYS 0x000010 /* physical IO */
111: #define B_XXX 0x000020 /* was B_MAP, alloc UNIBUS on pdp-11 */
112: #define B_WANTED 0x000040 /* issue wakeup when BUSY goes off */
113: #define B_AGE 0x000080 /* delayed write for correct aging */
114: #define B_ASYNC 0x000100 /* don't wait for I/O completion */
115: #define B_DELWRI 0x000200 /* write at exit of avail list */
116: #define B_TAPE 0x000400 /* this is a magtape (no bdwrite) */
117: #define B_UAREA 0x000800 /* add u-area to a swap operation */
118: #define B_PAGET 0x001000 /* page in/out of page table space */
119: #define B_DIRTY 0x002000 /* dirty page to be pushed out async */
120: #define B_PGIN 0x004000 /* pagein op, so swap() can count it */
121: #define B_CACHE 0x008000 /* did bread find us in the cache ? */
122: #define B_INVAL 0x010000 /* does not contain valid info */
123: #define B_LOCKED 0x020000 /* locked in core (not reusable) */
124: #define B_HEAD 0x040000 /* a buffer header, not a buffer */
125: #define B_BAD 0x100000 /* bad block revectoring in progress */
126: #define B_CALL 0x200000 /* call b_iodone from iodone */
127: #define B_NOT1K 0x400000 /* I/O is through intermediate buffer */
128:
129: /*
130: * Insq/Remq for the buffer hash lists.
131: */
132: #define bremhash(bp) { \
133: (bp)->b_back->b_forw = (bp)->b_forw; \
134: (bp)->b_forw->b_back = (bp)->b_back; \
135: }
136: #define binshash(bp, dp) { \
137: (bp)->b_forw = (dp)->b_forw; \
138: (bp)->b_back = (dp); \
139: (dp)->b_forw->b_back = (bp); \
140: (dp)->b_forw = (bp); \
141: }
142:
143: /*
144: * Insq/Remq for the buffer free lists.
145: */
146: #define bremfree(bp) { \
147: (bp)->av_back->av_forw = (bp)->av_forw; \
148: (bp)->av_forw->av_back = (bp)->av_back; \
149: }
150: #define binsheadfree(bp, dp) { \
151: (dp)->av_forw->av_back = (bp); \
152: (bp)->av_forw = (dp)->av_forw; \
153: (dp)->av_forw = (bp); \
154: (bp)->av_back = (dp); \
155: }
156: #define binstailfree(bp, dp) { \
157: (dp)->av_back->av_forw = (bp); \
158: (bp)->av_back = (dp)->av_back; \
159: (dp)->av_back = (bp); \
160: (bp)->av_forw = (dp); \
161: }
162:
163: /*
164: * Take a buffer off the free list it's on and
165: * mark it as being use (B_BUSY) by a device.
166: */
167: #define notavail(bp) { \
168: int x = spl8(); \
169: bremfree(bp); \
170: (bp)->b_flags |= B_BUSY; \
171: splx(x); \
172: }
173:
174: #define iodone biodone
175: #define iowait biowait
176:
177: /*
178: * Zero out a buffer's data portion.
179: */
180: #define clrbuf(bp) { \
181: bzero(bp->b_un.b_addr, bp->b_bcount); \
182: bp->b_resid = 0; \
183: }
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