2 * Copyright (c) 2005 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * $FreeBSD: src/sbin/dump/cache.c,v 1.1.2.1 2003/01/25 18:54:59 dillon Exp $
37 * Block cache for dump
40 #include <sys/param.h>
44 #include <vfs/ufs/dir.h>
45 #include <vfs/ufs/dinode.h>
46 #include <vfs/ufs/fs.h>
48 #include <protocols/dumprestore.h>
59 typedef struct Block {
60 struct Block *b_HNext; /* must be first field */
68 static char *DataBase;
69 static Block **BlockHash;
81 if ((BlockSize = sblock->fs_bsize * BLKFACTOR) > MAXBSIZE)
83 NBlocks = cachesize / BlockSize;
84 HSize = NBlocks / HFACTOR;
86 msg("Cache %d MB, blocksize = %d\n",
87 NBlocks * BlockSize / (1024 * 1024), BlockSize);
89 base = calloc(sizeof(Block), NBlocks);
90 BlockHash = calloc(sizeof(Block *), HSize);
91 DataBase = mmap(NULL, NBlocks * BlockSize,
92 PROT_READ|PROT_WRITE, MAP_ANON, -1, 0);
93 for (i = 0; i < NBlocks; ++i) {
94 base[i].b_Data = DataBase + i * BlockSize;
95 base[i].b_Offset = (off_t)-1;
97 base[i].b_HNext = BlockHash[hi];
98 BlockHash[hi] = &base[i];
103 cread(int fd, void *buf, size_t nbytes, off_t offset)
113 * If the cache is disabled, or we do not yet know the filesystem
114 * block size, then revert to pread. Otherwise initialize the
115 * cache as necessary and continue.
117 if (cachesize <= 0 || sblock->fs_bsize == 0)
118 return(pread(fd, buf, nbytes, offset));
119 if (DataBase == NULL)
123 * If the request crosses a cache block boundary, or the
124 * request is larger or equal to the cache block size,
125 * revert to pread(). Full-block-reads are typically
126 * one-time calls and caching would be detrimental.
128 mask = ~(off_t)(BlockSize - 1);
129 if (nbytes >= (unsigned)BlockSize ||
130 ((offset ^ (offset + nbytes - 1)) & mask) != 0) {
131 return(pread(fd, buf, nbytes, offset));
135 * Obtain and access the cache block. Cache a successful
136 * result. If an error occurs, revert to pread() (this might
137 * occur near the end of the media).
139 hi = (offset / BlockSize) % HSize;
140 pblk = &BlockHash[hi];
142 while ((blk = *pblk) != NULL) {
143 if (((blk->b_Offset ^ offset) & mask) == 0)
146 pblk = &blk->b_HNext;
151 blk->b_Offset = offset & mask;
152 n = pread(fd, blk->b_Data, BlockSize, blk->b_Offset);
153 if (n != BlockSize) {
154 blk->b_Offset = (off_t)-1;
159 bcopy(blk->b_Data + (offset - blk->b_Offset), buf, nbytes);
160 *pblk = blk->b_HNext;
161 blk->b_HNext = BlockHash[hi];
165 return(pread(fd, buf, nbytes, offset));