321 lines
9.9 KiB
C
321 lines
9.9 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 fs_readwrite().
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*
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* The entry points into this file are
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* write_map: write a new zone into an inode
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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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* zero_block: overwrite a block with zeroes
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*
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*/
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#include "fs.h"
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#include <string.h>
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#include <assert.h>
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#include <sys/param.h>
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#include "buf.h"
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#include "inode.h"
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#include "super.h"
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static void wr_indir(struct buf *bp, int index, zone_t zone);
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static int empty_indir(struct buf *, struct super_block *);
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/*===========================================================================*
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* write_map *
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*===========================================================================*/
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int write_map(rip, position, new_zone, op)
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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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int op; /* special actions */
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{
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/* Write a new zone into an inode.
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*
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* If op includes WMAP_FREE, free the data zone corresponding to that position
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* in the inode ('new_zone' is ignored then). Also free the indirect block
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* if that was the last entry in the indirect block.
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* Also free the double indirect block if that was the last entry in the
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* double indirect block.
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*/
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int scale, ind_ex = 0, new_ind, new_dbl,
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zones, nr_indirects, single, zindex, ex;
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zone_t z, z1, z2 = NO_ZONE, old_zone;
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register block_t b;
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long excess, zone;
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struct buf *bp_dindir = NULL, *bp = NULL;
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IN_MARKDIRTY(rip);
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scale = rip->i_sp->s_log_zone_size; /* for zone-block conversion */
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/* relative zone # to insert */
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zone = (position/rip->i_sp->s_block_size) >> scale;
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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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if(rip->i_zone[zindex] != NO_ZONE && (op & WMAP_FREE)) {
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free_zone(rip->i_dev, rip->i_zone[zindex]);
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rip->i_zone[zindex] = NO_ZONE;
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} else {
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rip->i_zone[zindex] = new_zone;
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}
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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 ( (z2 = z = rip->i_zone[zones+1]) == NO_ZONE &&
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!(op & WMAP_FREE)) {
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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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/* 'z' is zone number for double indirect block, either old
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* or newly created.
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* If there wasn't one and WMAP_FREE is set, 'z' is NO_ZONE.
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*/
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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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if(z == NO_ZONE && (op & WMAP_FREE)) {
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/* WMAP_FREE and no double indirect block - then no
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* single indirect block either.
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*/
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z1 = NO_ZONE;
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} else {
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b = (block_t) z << scale;
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bp_dindir = get_block(rip->i_dev, b,
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(new_dbl?NO_READ:NORMAL));
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if (new_dbl) zero_block(bp_dindir);
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z1 = rd_indir(bp_dindir, ind_ex);
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}
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single = FALSE;
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}
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/* z1 is now single indirect zone, or NO_ZONE; 'excess' is index.
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* We have to create the indirect zone if it's NO_ZONE. Unless
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* we're freeing (WMAP_FREE).
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*/
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if (z1 == NO_ZONE && !(op & WMAP_FREE)) {
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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 w. single indirect */
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else
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wr_indir(bp_dindir, ind_ex, z1); /* update dbl indir */
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new_ind = TRUE;
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/* If double ind, it is dirty. */
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if (bp_dindir != NULL) MARKDIRTY(bp_dindir);
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if (z1 == NO_ZONE) {
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/* Release dbl indirect blk. */
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put_block(bp_dindir, INDIRECT_BLOCK);
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return(err_code); /* couldn't create single ind */
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}
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}
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/* z1 is indirect block's zone number (unless it's NO_ZONE when we're
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* freeing).
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*/
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if(z1 != NO_ZONE) {
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ex = (int) excess; /* we need an int here */
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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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if(op & WMAP_FREE) {
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if((old_zone = rd_indir(bp, ex)) != NO_ZONE) {
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free_zone(rip->i_dev, old_zone);
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wr_indir(bp, ex, NO_ZONE);
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}
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/* Last reference in the indirect block gone? Then
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* free the indirect block.
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*/
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if(empty_indir(bp, rip->i_sp)) {
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free_zone(rip->i_dev, z1);
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z1 = NO_ZONE;
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/* Update the reference to the indirect block to
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* NO_ZONE - in the double indirect block if there
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* is one, otherwise in the inode directly.
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*/
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if(single) {
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rip->i_zone[zones] = z1;
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} else {
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wr_indir(bp_dindir, ind_ex, z1);
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MARKDIRTY(bp_dindir);
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}
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}
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} else {
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wr_indir(bp, ex, new_zone);
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}
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/* z1 equals NO_ZONE only when we are freeing up the indirect block. */
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if(z1 == NO_ZONE) { MARKCLEAN(bp); } else { MARKDIRTY(bp); }
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put_block(bp, INDIRECT_BLOCK);
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}
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/* If the single indirect block isn't there (or was just freed),
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* see if we have to keep the double indirect block, if any.
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* If we don't have to keep it, don't bother writing it out.
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*/
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if(z1 == NO_ZONE && !single && z2 != NO_ZONE &&
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empty_indir(bp_dindir, rip->i_sp)) {
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MARKCLEAN(bp_dindir);
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free_zone(rip->i_dev, z2);
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rip->i_zone[zones+1] = NO_ZONE;
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}
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put_block(bp_dindir, INDIRECT_BLOCK); /* release double indirect blk */
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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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static 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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if(bp == NULL)
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panic("wr_indir() on NULL");
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sp = get_super(lmfs_dev(bp)); /* need super block to find file sys type */
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/* write a zone into an indirect block */
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assert(sp->s_version == V3);
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b_v2_ind(bp)[index] = (zone_t) conv4(sp->s_native, (long) zone);
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}
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/*===========================================================================*
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* empty_indir *
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*===========================================================================*/
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static int empty_indir(bp, sb)
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struct buf *bp; /* pointer to indirect block */
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struct super_block *sb; /* superblock of device block resides on */
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{
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/* Return nonzero if the indirect block pointed to by bp contains
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* only NO_ZONE entries.
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*/
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unsigned int i;
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for(i = 0; i < V2_INDIRECTS(sb->s_block_size); i++)
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if( b_v2_ind(bp)[i] != NO_ZONE)
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return(0);
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return(1);
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}
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/*===========================================================================*
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* clear_zone *
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*===========================================================================*/
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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; /* 1 if called by new_block, 0 otherwise */
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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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* fs_readwrite(), truncate_inode(), and new_block().
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*/
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int scale;
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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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assert(scale == 0);
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return;
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}
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/*===========================================================================*
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* new_block *
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*===========================================================================*/
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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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/* Is another block available in the current zone? */
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if ( (b = read_map(rip, position, 0)) == NO_BLOCK) {
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if (rip->i_zsearch == NO_ZONE) {
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/* First search for this file. Start looking from
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* the file's first data zone to prevent fragmentation
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*/
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if ( (z = rip->i_zone[0]) == NO_ZONE) {
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/* No first zone for file either, let alloc_zone
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* decide. */
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z = (zone_t) rip->i_sp->s_firstdatazone;
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}
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} else {
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/* searched before, start from last find */
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z = rip->i_zsearch;
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}
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if ( (z = alloc_zone(rip->i_dev, z)) == NO_ZONE) return(NULL);
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rip->i_zsearch = z; /* store for next lookup */
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if ( (r = write_map(rip, position, z, 0)) != OK) {
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free_zone(rip->i_dev, z);
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err_code = r;
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return(NULL);
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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 = lmfs_get_block_ino(rip->i_dev, b, NO_READ, rip->i_num,
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rounddown(position, rip->i_sp->s_block_size));
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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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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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ASSERT(lmfs_bytes(bp) > 0);
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ASSERT(bp->data);
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memset(b_data(bp), 0, (size_t) lmfs_bytes(bp));
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MARKDIRTY(bp);
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}
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