76 lines
2.2 KiB
C
76 lines
2.2 KiB
C
/* This file manages the super block table and the related data structures,
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* namely, the bit maps that keep track of which zones and which inodes are
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* allocated and which are free. When a new inode or zone is needed, the
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* appropriate bit map is searched for a free entry.
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*
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* The entry points into this file are
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* alloc_bit: somebody wants to allocate a zone or inode; find one
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* free_bit: indicate that a zone or inode is available for allocation
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*/
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#include "fs.h"
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#include "buf.h"
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#include "inode.h"
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#include "const.h"
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/*===========================================================================*
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* alloc_bit *
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*===========================================================================*/
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bit_t alloc_bit(void)
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{
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/* Allocate a bit from a bit map and return its bit number. */
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bitchunk_t *wptr, *wlim;
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bit_t b;
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unsigned int i, bcount;
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bcount = FS_BITMAP_CHUNKS(NR_INODES); /* Inode map has this many chunks. */
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wlim = &inodemap[bcount]; /* Point to last chunk in inodemap. */
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for (wptr = &inodemap[0]; wptr < wlim; wptr++) {
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/* Does this word contain a free bit? */
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if (*wptr == (bitchunk_t) ~0) continue; /* No. Go to next word */
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/* Find and allocate the free bit. */
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for (i = 0; (*wptr & (1 << i)) != 0; ++i) {}
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/* Get inode number */
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b = (bit_t) ((wptr - &inodemap[0]) * FS_BITCHUNK_BITS + i);
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/* Don't allocate bits beyond end of map. */
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if (b >= NR_INODES) break;
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/* Allocate and return bit number. */
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*wptr |= 1 << i;
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/* Mark server 'busy' */
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busy++;
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return(b);
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}
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return(NO_BIT); /* no bit could be allocated */
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}
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/*===========================================================================*
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* free_bit *
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*===========================================================================*/
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void free_bit(bit_returned)
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bit_t bit_returned; /* number of bit to insert into the inode map*/
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{
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bitchunk_t *k, mask;
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bit_t bit;
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unsigned word;
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/* Get word offset and bit within offset */
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word = (unsigned) (bit_returned / (bit_t) FS_BITCHUNK_BITS);
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bit = bit_returned % (bit_t) FS_BITCHUNK_BITS;
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/* Unset bit */
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k = &inodemap[word];
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mask = (unsigned) 1 << bit;
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*k &= ~mask;
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busy--; /* One inode less in use. */
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}
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