2  * CACHE.C
4  *	Block cache for dump
35 typedef struct Block {  struct
36 	struct Block	*b_HNext;	/* must be first field */  argument
39 } Block;  typedef
45 static Block **BlockHash;
55 	Block *base;  in cinit()
57 	if ((BlockSize = sblock->fs_bsize * BLKFACTOR) > MAXBSIZE)  in cinit()
62 	msg("Cache %d MB, blocksize = %d\n",   in cinit()
65 	base = calloc(sizeof(Block), NBlocks);  in cinit()
66 	BlockHash = calloc(sizeof(Block *), HSize);  in cinit()
68 			PROT_READ|PROT_WRITE, MAP_ANON, -1, 0);  in cinit()
71 		base[i].b_Offset = (off_t)-1;  in cinit()
81 	Block *blk;  in cread()
82 	Block **pblk;  in cread()
83 	Block **ppblk;  in cread()
89 	 * If the cache is disabled, or we do not yet know the filesystem  in cread()
90 	 * block size, then revert to pread.  Otherwise initialize the  in cread()
91 	 * cache as necessary and continue.  in cread()
93 	if (cachesize <= 0 || sblock->fs_bsize == 0)  in cread()
99 	 * If the request crosses a cache block boundary, or the  in cread()
100 	 * request is larger or equal to the cache block size,  in cread()
101 	 * revert to pread().  Full-block-reads are typically  in cread()
102 	 * one-time calls and caching would be detrimental.  in cread()
104 	mask = ~(off_t)(BlockSize - 1);  in cread()
106 	    ((offset ^ (offset + nbytes - 1)) & mask) != 0) {  in cread()
111 	 * Obtain and access the cache block.  Cache a successful  in cread()
119 		if (((blk->b_Offset ^ offset) & mask) == 0)  in cread()
122 		pblk = &blk->b_HNext;  in cread()
127 		blk->b_Offset = offset & mask;  in cread()
128 		n = pread(fd, blk->b_Data, BlockSize, blk->b_Offset);  in cread()
130 			blk->b_Offset = (off_t)-1;  in cread()
135 		bcopy(blk->b_Data + (offset - blk->b_Offset), buf, nbytes);  in cread()
136 		*pblk = blk->b_HNext;  in cread()
137 		blk->b_HNext = BlockHash[hi];  in cread()