minix/servers/fs/write.c
Ben Gras 50b06261b6 Implementation of truncate(), ftruncate() and the F_FREESP fcntl().
Implemented by changing write_map to accept a WMAP_FREE flag. In that
case, it doesn't update the datablock (creating indirect zones as
necessary) pointer, but it frees the datablock if present. Also it
frees the single and double indirect blocks if unused.

This makes the implementation of truncate_inode() simpler.
truncate_inode() now accepts a truncation length which makes
implementing truncate() and ftruncate() simple.

This also allowed implementing the F_FREESP fcntl().
2006-01-11 17:14:51 +00:00

338 lines
11 KiB
C

/* This file is the counterpart of "read.c". It contains the code for writing
* insofar as this is not contained in read_write().
*
* The entry points into this file are
* do_write: call read_write to perform the WRITE system call
* clear_zone: erase a zone in the middle of a file
* new_block: acquire a new block
*/
#include "fs.h"
#include <string.h>
#include "buf.h"
#include "file.h"
#include "fproc.h"
#include "inode.h"
#include "super.h"
FORWARD _PROTOTYPE( void wr_indir, (struct buf *bp, int index, zone_t zone) );
FORWARD _PROTOTYPE( int empty_indir, (struct buf *, struct super_block *) );
/*===========================================================================*
* do_write *
*===========================================================================*/
PUBLIC int do_write()
{
/* Perform the write(fd, buffer, nbytes) system call. */
return(read_write(WRITING));
}
/*===========================================================================*
* write_map *
*===========================================================================*/
PUBLIC int write_map(rip, position, new_zone, op)
struct inode *rip; /* pointer to inode to be changed */
off_t position; /* file address to be mapped */
zone_t new_zone; /* zone # to be inserted */
int op; /* special actions */
{
/* Write a new zone into an inode.
*
* If op includes WMAP_FREE, free the data zone corresponding to that position
* in the inode ('new_zone' is ignored then). Also free the indirect block
* if that was the last entry in the indirect block.
* Also free the double indirect block if that was the last entry in the
* double indirect block.
*/
int scale, ind_ex, new_ind, new_dbl, zones, nr_indirects, single, zindex, ex;
zone_t z, z1, z2 = NO_ZONE, old_zone;
register block_t b;
long excess, zone;
struct buf *bp_dindir = NIL_BUF, *bp = NIL_BUF;
rip->i_dirt = DIRTY; /* inode will be changed */
scale = rip->i_sp->s_log_zone_size; /* for zone-block conversion */
/* relative zone # to insert */
zone = (position/rip->i_sp->s_block_size) >> scale;
zones = rip->i_ndzones; /* # direct zones in the inode */
nr_indirects = rip->i_nindirs;/* # indirect zones per indirect block */
/* Is 'position' to be found in the inode itself? */
if (zone < zones) {
zindex = (int) zone; /* we need an integer here */
if(rip->i_zone[zindex] != NO_ZONE && (op & WMAP_FREE)) {
free_zone(rip->i_dev, rip->i_zone[zindex]);
rip->i_zone[zindex] = NO_ZONE;
} else {
rip->i_zone[zindex] = new_zone;
}
return(OK);
}
/* It is not in the inode, so it must be single or double indirect. */
excess = zone - zones; /* first Vx_NR_DZONES don't count */
new_ind = FALSE;
new_dbl = FALSE;
if (excess < nr_indirects) {
/* 'position' can be located via the single indirect block. */
z1 = rip->i_zone[zones]; /* single indirect zone */
single = TRUE;
} else {
/* 'position' can be located via the double indirect block. */
if ( (z2 = z = rip->i_zone[zones+1]) == NO_ZONE &&
!(op & WMAP_FREE)) {
/* Create the double indirect block. */
if ( (z = alloc_zone(rip->i_dev, rip->i_zone[0])) == NO_ZONE)
return(err_code);
rip->i_zone[zones+1] = z;
new_dbl = TRUE; /* set flag for later */
}
/* 'z' is zone number for double indirect block, either old
* or newly created.
* If there wasn't one and WMAP_FREE is set, 'z' is NO_ZONE.
*/
excess -= nr_indirects; /* single indirect doesn't count */
ind_ex = (int) (excess / nr_indirects);
excess = excess % nr_indirects;
if (ind_ex >= nr_indirects) return(EFBIG);
if(z == NO_ZONE) {
/* WMAP_FREE and no double indirect block - then no
* single indirect block either.
*/
z1 = NO_ZONE;
} else {
b = (block_t) z << scale;
bp_dindir = get_block(rip->i_dev, b, (new_dbl?NO_READ:NORMAL));
if (new_dbl) zero_block(bp_dindir);
z1 = rd_indir(bp_dindir, ind_ex);
}
single = FALSE;
}
/* z1 is now single indirect zone, or NO_ZONE; 'excess' is index.
* We have to create the indirect zone if it's NO_ZONE. Unless
* we're freeing (WMAP_FREE).
*/
if (z1 == NO_ZONE && !(op & WMAP_FREE)) {
z1 = alloc_zone(rip->i_dev, rip->i_zone[0]);
if (single)
rip->i_zone[zones] = z1; /* update inode w. single indirect */
else
wr_indir(bp_dindir, ind_ex, z1); /* update dbl indir */
new_ind = TRUE;
/* If double ind, it is dirty. */
if (bp_dindir != NIL_BUF) bp_dindir->b_dirt = DIRTY;
if (z1 == NO_ZONE) {
/* Release dbl indirect blk. */
put_block(bp_dindir, INDIRECT_BLOCK);
return(err_code); /* couldn't create single ind */
}
}
/* z1 is indirect block's zone number (unless it's NO_ZONE when we're
* freeing).
*/
if(z1 != NO_ZONE) {
ex = (int) excess; /* we need an int here */
b = (block_t) z1 << scale;
bp = get_block(rip->i_dev, b, (new_ind ? NO_READ : NORMAL) );
if (new_ind) zero_block(bp);
if(op & WMAP_FREE) {
if((old_zone = rd_indir(bp, ex)) != NO_ZONE) {
free_zone(rip->i_dev, old_zone);
wr_indir(bp, ex, NO_ZONE);
}
/* Last reference in the indirect block gone? Then
* Free the indirect block.
*/
if(empty_indir(bp, rip->i_sp)) {
free_zone(rip->i_dev, z1);
z1 = NO_ZONE;
/* Update the reference to the indirect block to
* NO_ZONE - in the double indirect block if there
* is one, otherwise in the inode directly.
*/
if(single) {
rip->i_zone[zones] = z1;
} else {
wr_indir(bp_dindir, ind_ex, z1);
bp_dindir->b_dirt = DIRTY;
}
}
} else {
wr_indir(bp, ex, new_zone);
}
bp->b_dirt = DIRTY;
put_block(bp, INDIRECT_BLOCK);
}
/* If the single indirect block isn't there (or was just freed),
* see if we have to keep the double indirect block.
*/
if(z1 == NO_ZONE && !single && empty_indir(bp_dindir, rip->i_sp) &&
z2 != NO_ZONE) {
free_zone(rip->i_dev, z2);
rip->i_zone[zones+1] = NO_ZONE;
}
put_block(bp_dindir, INDIRECT_BLOCK); /* release double indirect blk */
return(OK);
}
/*===========================================================================*
* wr_indir *
*===========================================================================*/
PRIVATE void wr_indir(bp, index, zone)
struct buf *bp; /* pointer to indirect block */
int index; /* index into *bp */
zone_t zone; /* zone to write */
{
/* Given a pointer to an indirect block, write one entry. */
struct super_block *sp;
if(bp == NIL_BUF)
panic(__FILE__, "wr_indir() on NIL_BUF", NO_NUM);
sp = get_super(bp->b_dev); /* need super block to find file sys type */
/* write a zone into an indirect block */
if (sp->s_version == V1)
bp->b_v1_ind[index] = (zone1_t) conv2(sp->s_native, (int) zone);
else
bp->b_v2_ind[index] = (zone_t) conv4(sp->s_native, (long) zone);
}
/*===========================================================================*
* empty_indir *
*===========================================================================*/
PRIVATE int empty_indir(bp, sb)
struct buf *bp; /* pointer to indirect block */
struct super_block *sb; /* superblock of device block resides on */
{
/* Return nonzero if the indirect block pointed to by bp contains
* only NO_ZONE entries.
*/
int i;
if(sb->s_version == V1) {
for(i = 0; i < V1_INDIRECTS; i++)
if(bp->b_v1_ind[i] != NO_ZONE)
return 0;
} else {
for(i = 0; i < V2_INDIRECTS(sb->s_block_size); i++)
if(bp->b_v2_ind[i] != NO_ZONE)
return 0;
}
return 1;
}
/*===========================================================================*
* clear_zone *
*===========================================================================*/
PUBLIC void clear_zone(rip, pos, flag)
register struct inode *rip; /* inode to clear */
off_t pos; /* points to block to clear */
int flag; /* 0 if called by read_write, 1 by new_block */
{
/* Zero a zone, possibly starting in the middle. The parameter 'pos' gives
* a byte in the first block to be zeroed. Clearzone() is called from
* read_write and new_block().
*/
register struct buf *bp;
register block_t b, blo, bhi;
register off_t next;
register int scale;
register zone_t zone_size;
/* If the block size and zone size are the same, clear_zone() not needed. */
scale = rip->i_sp->s_log_zone_size;
if (scale == 0) return;
zone_size = (zone_t) rip->i_sp->s_block_size << scale;
if (flag == 1) pos = (pos/zone_size) * zone_size;
next = pos + rip->i_sp->s_block_size - 1;
/* If 'pos' is in the last block of a zone, do not clear the zone. */
if (next/zone_size != pos/zone_size) return;
if ( (blo = read_map(rip, next)) == NO_BLOCK) return;
bhi = ( ((blo>>scale)+1) << scale) - 1;
/* Clear all the blocks between 'blo' and 'bhi'. */
for (b = blo; b <= bhi; b++) {
bp = get_block(rip->i_dev, b, NO_READ);
zero_block(bp);
put_block(bp, FULL_DATA_BLOCK);
}
}
/*===========================================================================*
* new_block *
*===========================================================================*/
PUBLIC struct buf *new_block(rip, position)
register struct inode *rip; /* pointer to inode */
off_t position; /* file pointer */
{
/* Acquire a new block and return a pointer to it. Doing so may require
* allocating a complete zone, and then returning the initial block.
* On the other hand, the current zone may still have some unused blocks.
*/
register struct buf *bp;
block_t b, base_block;
zone_t z;
zone_t zone_size;
int scale, r;
struct super_block *sp;
/* Is another block available in the current zone? */
if ( (b = read_map(rip, position)) == NO_BLOCK) {
/* Choose first zone if possible. */
/* Lose if the file is nonempty but the first zone number is NO_ZONE
* corresponding to a zone full of zeros. It would be better to
* search near the last real zone.
*/
if (rip->i_zone[0] == NO_ZONE) {
sp = rip->i_sp;
z = sp->s_firstdatazone;
} else {
z = rip->i_zone[0]; /* hunt near first zone */
}
if ( (z = alloc_zone(rip->i_dev, z)) == NO_ZONE) return(NIL_BUF);
if ( (r = write_map(rip, position, z, 0)) != OK) {
free_zone(rip->i_dev, z);
err_code = r;
return(NIL_BUF);
}
/* If we are not writing at EOF, clear the zone, just to be safe. */
if ( position != rip->i_size) clear_zone(rip, position, 1);
scale = rip->i_sp->s_log_zone_size;
base_block = (block_t) z << scale;
zone_size = (zone_t) rip->i_sp->s_block_size << scale;
b = base_block + (block_t)((position % zone_size)/rip->i_sp->s_block_size);
}
bp = get_block(rip->i_dev, b, NO_READ);
zero_block(bp);
return(bp);
}
/*===========================================================================*
* zero_block *
*===========================================================================*/
PUBLIC void zero_block(bp)
register struct buf *bp; /* pointer to buffer to zero */
{
/* Zero a block. */
memset(bp->b_data, 0, _MAX_BLOCK_SIZE);
bp->b_dirt = DIRTY;
}