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145 lines
3.0 KiB
C
145 lines
3.0 KiB
C
/*
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* CACHE.C
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*
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* Block cache for dump
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*/
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#include <sys/param.h>
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#include <sys/stat.h>
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#include <sys/mman.h>
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#ifdef sunos
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#include <sys/vnode.h>
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#include <ufs/fs.h>
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#include <ufs/fsdir.h>
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#include <ufs/inode.h>
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#else
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#include <ufs/ufs/dir.h>
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#include <ufs/ufs/dinode.h>
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#include <ufs/ffs/fs.h>
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#endif
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#include <protocols/dumprestore.h>
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#include <ctype.h>
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#include <stdio.h>
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#ifdef __STDC__
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#include <errno.h>
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#include <string.h>
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#include <stdlib.h>
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#include <unistd.h>
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#endif
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#include "dump.h"
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typedef struct Block {
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struct Block *b_HNext; /* must be first field */
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off_t b_Offset;
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char *b_Data;
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} Block;
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#define HFACTOR 4
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#define BLKFACTOR 4
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static char *DataBase;
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static Block **BlockHash;
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static int BlockSize;
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static int HSize;
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static int NBlocks;
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static void
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cinit(void)
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{
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int i;
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int hi;
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Block *base;
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if ((BlockSize = sblock->fs_bsize * BLKFACTOR) > MAXBSIZE)
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BlockSize = MAXBSIZE;
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NBlocks = cachesize / BlockSize;
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HSize = NBlocks / HFACTOR;
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msg("Cache %d MB, blocksize = %d\n",
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NBlocks * BlockSize / (1024 * 1024), BlockSize);
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base = calloc(sizeof(Block), NBlocks);
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BlockHash = calloc(sizeof(Block *), HSize);
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DataBase = mmap(NULL, NBlocks * BlockSize,
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PROT_READ|PROT_WRITE, MAP_ANON, -1, 0);
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for (i = 0; i < NBlocks; ++i) {
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base[i].b_Data = DataBase + i * BlockSize;
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base[i].b_Offset = (off_t)-1;
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hi = i / HFACTOR;
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base[i].b_HNext = BlockHash[hi];
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BlockHash[hi] = &base[i];
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}
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}
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ssize_t
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cread(int fd, void *buf, size_t nbytes, off_t offset)
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{
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Block *blk;
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Block **pblk;
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Block **ppblk;
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int hi;
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int n;
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off_t mask;
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/*
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* If the cache is disabled, or we do not yet know the filesystem
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* block size, then revert to pread. Otherwise initialize the
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* cache as necessary and continue.
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*/
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if (cachesize <= 0 || sblock->fs_bsize == 0)
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return(pread(fd, buf, nbytes, offset));
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if (DataBase == NULL)
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cinit();
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/*
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* If the request crosses a cache block boundary, or the
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* request is larger or equal to the cache block size,
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* revert to pread(). Full-block-reads are typically
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* one-time calls and caching would be detrimental.
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*/
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mask = ~(off_t)(BlockSize - 1);
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if (nbytes >= BlockSize ||
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((offset ^ (offset + nbytes - 1)) & mask) != 0) {
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return(pread(fd, buf, nbytes, offset));
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}
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/*
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* Obtain and access the cache block. Cache a successful
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* result. If an error occurs, revert to pread() (this might
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* occur near the end of the media).
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*/
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hi = (offset / BlockSize) % HSize;
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pblk = &BlockHash[hi];
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ppblk = NULL;
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while ((blk = *pblk) != NULL) {
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if (((blk->b_Offset ^ offset) & mask) == 0)
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break;
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ppblk = pblk;
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pblk = &blk->b_HNext;
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}
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if (blk == NULL) {
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blk = *ppblk;
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pblk = ppblk;
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blk->b_Offset = offset & mask;
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n = pread(fd, blk->b_Data, BlockSize, blk->b_Offset);
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if (n != BlockSize) {
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blk->b_Offset = (off_t)-1;
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blk = NULL;
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}
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}
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if (blk) {
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bcopy(blk->b_Data + (offset - blk->b_Offset), buf, nbytes);
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*pblk = blk->b_HNext;
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blk->b_HNext = BlockHash[hi];
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BlockHash[hi] = blk;
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return(nbytes);
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} else {
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return(pread(fd, buf, nbytes, offset));
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}
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}
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