252 lines
8.2 KiB
C
252 lines
8.2 KiB
C
/* This file is the counterpart of "read.c". It contains the code for writing
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* insofar as this is not contained in read_write().
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*
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* The entry points into this file are
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* do_write: call read_write to perform the WRITE system call
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* clear_zone: erase a zone in the middle of a file
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* new_block: acquire a new block
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*/
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#include "fs.h"
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#include <string.h>
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#include "buf.h"
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#include "file.h"
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#include "fproc.h"
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#include "inode.h"
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#include "super.h"
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FORWARD _PROTOTYPE( int write_map, (struct inode *rip, off_t position,
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zone_t new_zone) );
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FORWARD _PROTOTYPE( void wr_indir, (struct buf *bp, int index, zone_t zone) );
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/*===========================================================================*
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* do_write *
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*===========================================================================*/
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PUBLIC int do_write()
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{
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/* Perform the write(fd, buffer, nbytes) system call. */
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return(read_write(WRITING));
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}
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/*===========================================================================*
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* write_map *
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*===========================================================================*/
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PRIVATE int write_map(rip, position, new_zone)
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register struct inode *rip; /* pointer to inode to be changed */
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off_t position; /* file address to be mapped */
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zone_t new_zone; /* zone # to be inserted */
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{
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/* Write a new zone into an inode. */
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int scale, ind_ex, new_ind, new_dbl, zones, nr_indirects, single, zindex, ex;
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zone_t z, z1;
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register block_t b;
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long excess, zone;
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struct buf *bp;
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rip->i_dirt = DIRTY; /* inode will be changed */
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bp = NIL_BUF;
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scale = rip->i_sp->s_log_zone_size; /* for zone-block conversion */
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zone = (position/rip->i_sp->s_block_size) >> scale; /* relative zone # to insert */
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zones = rip->i_ndzones; /* # direct zones in the inode */
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nr_indirects = rip->i_nindirs;/* # indirect zones per indirect block */
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/* Is 'position' to be found in the inode itself? */
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if (zone < zones) {
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zindex = (int) zone; /* we need an integer here */
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rip->i_zone[zindex] = new_zone;
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return(OK);
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}
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/* It is not in the inode, so it must be single or double indirect. */
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excess = zone - zones; /* first Vx_NR_DZONES don't count */
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new_ind = FALSE;
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new_dbl = FALSE;
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if (excess < nr_indirects) {
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/* 'position' can be located via the single indirect block. */
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z1 = rip->i_zone[zones]; /* single indirect zone */
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single = TRUE;
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} else {
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/* 'position' can be located via the double indirect block. */
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if ( (z = rip->i_zone[zones+1]) == NO_ZONE) {
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/* Create the double indirect block. */
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if ( (z = alloc_zone(rip->i_dev, rip->i_zone[0])) == NO_ZONE)
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return(err_code);
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rip->i_zone[zones+1] = z;
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new_dbl = TRUE; /* set flag for later */
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}
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/* Either way, 'z' is zone number for double indirect block. */
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excess -= nr_indirects; /* single indirect doesn't count */
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ind_ex = (int) (excess / nr_indirects);
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excess = excess % nr_indirects;
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if (ind_ex >= nr_indirects) return(EFBIG);
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b = (block_t) z << scale;
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bp = get_block(rip->i_dev, b, (new_dbl ? NO_READ : NORMAL));
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if (new_dbl) zero_block(bp);
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z1 = rd_indir(bp, ind_ex);
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single = FALSE;
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}
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/* z1 is now single indirect zone; 'excess' is index. */
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if (z1 == NO_ZONE) {
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/* Create indirect block and store zone # in inode or dbl indir blk. */
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z1 = alloc_zone(rip->i_dev, rip->i_zone[0]);
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if (single)
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rip->i_zone[zones] = z1; /* update inode */
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else
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wr_indir(bp, ind_ex, z1); /* update dbl indir */
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new_ind = TRUE;
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if (bp != NIL_BUF) bp->b_dirt = DIRTY; /* if double ind, it is dirty*/
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if (z1 == NO_ZONE) {
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put_block(bp, INDIRECT_BLOCK); /* release dbl indirect blk */
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return(err_code); /* couldn't create single ind */
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}
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}
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put_block(bp, INDIRECT_BLOCK); /* release double indirect blk */
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/* z1 is indirect block's zone number. */
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b = (block_t) z1 << scale;
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bp = get_block(rip->i_dev, b, (new_ind ? NO_READ : NORMAL) );
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if (new_ind) zero_block(bp);
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ex = (int) excess; /* we need an int here */
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wr_indir(bp, ex, new_zone);
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bp->b_dirt = DIRTY;
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put_block(bp, INDIRECT_BLOCK);
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return(OK);
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}
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/*===========================================================================*
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* wr_indir *
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*===========================================================================*/
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PRIVATE void wr_indir(bp, index, zone)
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struct buf *bp; /* pointer to indirect block */
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int index; /* index into *bp */
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zone_t zone; /* zone to write */
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{
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/* Given a pointer to an indirect block, write one entry. */
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struct super_block *sp;
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sp = get_super(bp->b_dev); /* need super block to find file sys type */
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/* write a zone into an indirect block */
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if (sp->s_version == V1)
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bp->b_v1_ind[index] = (zone1_t) conv2(sp->s_native, (int) zone);
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else
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bp->b_v2_ind[index] = (zone_t) conv4(sp->s_native, (long) zone);
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}
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/*===========================================================================*
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* clear_zone *
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*===========================================================================*/
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PUBLIC void clear_zone(rip, pos, flag)
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register struct inode *rip; /* inode to clear */
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off_t pos; /* points to block to clear */
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int flag; /* 0 if called by read_write, 1 by new_block */
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{
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/* Zero a zone, possibly starting in the middle. The parameter 'pos' gives
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* a byte in the first block to be zeroed. Clearzone() is called from
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* read_write and new_block().
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*/
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register struct buf *bp;
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register block_t b, blo, bhi;
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register off_t next;
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register int scale;
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register zone_t zone_size;
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/* If the block size and zone size are the same, clear_zone() not needed. */
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scale = rip->i_sp->s_log_zone_size;
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if (scale == 0) return;
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zone_size = (zone_t) rip->i_sp->s_block_size << scale;
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if (flag == 1) pos = (pos/zone_size) * zone_size;
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next = pos + rip->i_sp->s_block_size - 1;
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/* If 'pos' is in the last block of a zone, do not clear the zone. */
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if (next/zone_size != pos/zone_size) return;
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if ( (blo = read_map(rip, next)) == NO_BLOCK) return;
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bhi = ( ((blo>>scale)+1) << scale) - 1;
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/* Clear all the blocks between 'blo' and 'bhi'. */
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for (b = blo; b <= bhi; b++) {
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bp = get_block(rip->i_dev, b, NO_READ);
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zero_block(bp);
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put_block(bp, FULL_DATA_BLOCK);
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}
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}
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/*===========================================================================*
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* new_block *
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*===========================================================================*/
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PUBLIC struct buf *new_block(rip, position)
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register struct inode *rip; /* pointer to inode */
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off_t position; /* file pointer */
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{
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/* Acquire a new block and return a pointer to it. Doing so may require
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* allocating a complete zone, and then returning the initial block.
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* On the other hand, the current zone may still have some unused blocks.
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*/
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register struct buf *bp;
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block_t b, base_block;
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zone_t z;
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zone_t zone_size;
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int scale, r;
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struct super_block *sp;
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/* Is another block available in the current zone? */
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if ( (b = read_map(rip, position)) == NO_BLOCK) {
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/* Choose first zone if possible. */
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/* Lose if the file is nonempty but the first zone number is NO_ZONE
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* corresponding to a zone full of zeros. It would be better to
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* search near the last real zone.
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*/
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if (rip->i_zone[0] == NO_ZONE) {
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sp = rip->i_sp;
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z = sp->s_firstdatazone;
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} else {
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z = rip->i_zone[0]; /* hunt near first zone */
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}
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if ( (z = alloc_zone(rip->i_dev, z)) == NO_ZONE) return(NIL_BUF);
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if ( (r = write_map(rip, position, z)) != OK) {
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free_zone(rip->i_dev, z);
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err_code = r;
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return(NIL_BUF);
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}
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/* If we are not writing at EOF, clear the zone, just to be safe. */
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if ( position != rip->i_size) clear_zone(rip, position, 1);
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scale = rip->i_sp->s_log_zone_size;
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base_block = (block_t) z << scale;
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zone_size = (zone_t) rip->i_sp->s_block_size << scale;
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b = base_block + (block_t)((position % zone_size)/rip->i_sp->s_block_size);
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}
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bp = get_block(rip->i_dev, b, NO_READ);
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zero_block(bp);
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return(bp);
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}
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/*===========================================================================*
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* zero_block *
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*===========================================================================*/
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PUBLIC void zero_block(bp)
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register struct buf *bp; /* pointer to buffer to zero */
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{
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/* Zero a block. */
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struct super_block *sb;
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int block_size;
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memset(bp->b_data, 0, MAX_BLOCK_SIZE);
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bp->b_dirt = DIRTY;
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}
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