184 lines
3.8 KiB
C
184 lines
3.8 KiB
C
/*
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* linux/fs/truncate.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*/
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/minix_fs.h>
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#include <linux/stat.h>
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#include <linux/fcntl.h>
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/*
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* Truncate has the most races in the whole filesystem: coding it is
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* a pain in the a**. Especially as I don't do any locking...
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*
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* The code may look a bit weird, but that's just because I've tried to
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* handle things like file-size changes in a somewhat graceful manner.
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* Anyway, truncating a file at the same time somebody else writes to it
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* is likely to result in pretty weird behaviour...
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*
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* The new code handles normal truncates (size = 0) as well as the more
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* general case (size = XXX). I hope.
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*/
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static int trunc_direct(struct inode * inode)
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{
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unsigned short * p;
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struct buffer_head * bh;
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int i, tmp;
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int retry = 0;
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#define DIRECT_BLOCK ((inode->i_size + 1023) >> 10)
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repeat:
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for (i = DIRECT_BLOCK ; i < 7 ; i++) {
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p = i + inode->u.minix_i.i_data;
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if (!(tmp = *p))
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continue;
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bh = get_hash_table(inode->i_dev,tmp,BLOCK_SIZE);
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if (i < DIRECT_BLOCK) {
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brelse(bh);
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goto repeat;
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}
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if ((bh && bh->b_count != 1) || tmp != *p) {
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retry = 1;
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brelse(bh);
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continue;
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}
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*p = 0;
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inode->i_dirt = 1;
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brelse(bh);
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minix_free_block(inode->i_sb,tmp);
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}
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return retry;
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}
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static int trunc_indirect(struct inode * inode, int offset, unsigned short * p)
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{
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struct buffer_head * bh;
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int i, tmp;
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struct buffer_head * ind_bh;
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unsigned short * ind;
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int retry = 0;
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#define INDIRECT_BLOCK (DIRECT_BLOCK-offset)
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tmp = *p;
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if (!tmp)
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return 0;
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ind_bh = bread(inode->i_dev, tmp, BLOCK_SIZE);
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if (tmp != *p) {
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brelse(ind_bh);
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return 1;
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}
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if (!ind_bh) {
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*p = 0;
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return 0;
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}
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repeat:
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for (i = INDIRECT_BLOCK ; i < 512 ; i++) {
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if (i < 0)
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i = 0;
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if (i < INDIRECT_BLOCK)
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goto repeat;
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ind = i+(unsigned short *) ind_bh->b_data;
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tmp = *ind;
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if (!tmp)
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continue;
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bh = get_hash_table(inode->i_dev,tmp,BLOCK_SIZE);
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if (i < INDIRECT_BLOCK) {
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brelse(bh);
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goto repeat;
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}
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if ((bh && bh->b_count != 1) || tmp != *ind) {
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retry = 1;
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brelse(bh);
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continue;
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}
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*ind = 0;
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ind_bh->b_dirt = 1;
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brelse(bh);
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minix_free_block(inode->i_sb,tmp);
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}
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ind = (unsigned short *) ind_bh->b_data;
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for (i = 0; i < 512; i++)
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if (*(ind++))
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break;
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if (i >= 512)
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if (ind_bh->b_count != 1)
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retry = 1;
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else {
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tmp = *p;
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*p = 0;
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minix_free_block(inode->i_sb,tmp);
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}
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brelse(ind_bh);
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return retry;
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}
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static int trunc_dindirect(struct inode * inode)
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{
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int i, tmp;
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struct buffer_head * dind_bh;
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unsigned short * dind, * p;
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int retry = 0;
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#define DINDIRECT_BLOCK ((DIRECT_BLOCK-(512+7))>>9)
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p = 8 + inode->u.minix_i.i_data;
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if (!(tmp = *p))
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return 0;
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dind_bh = bread(inode->i_dev, tmp, BLOCK_SIZE);
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if (tmp != *p) {
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brelse(dind_bh);
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return 1;
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}
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if (!dind_bh) {
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*p = 0;
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return 0;
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}
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repeat:
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for (i = DINDIRECT_BLOCK ; i < 512 ; i ++) {
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if (i < 0)
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i = 0;
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if (i < DINDIRECT_BLOCK)
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goto repeat;
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dind = i+(unsigned short *) dind_bh->b_data;
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retry |= trunc_indirect(inode,7+512+(i<<9),dind);
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dind_bh->b_dirt = 1;
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}
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dind = (unsigned short *) dind_bh->b_data;
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for (i = 0; i < 512; i++)
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if (*(dind++))
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break;
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if (i >= 512)
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if (dind_bh->b_count != 1)
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retry = 1;
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else {
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tmp = *p;
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*p = 0;
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inode->i_dirt = 1;
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minix_free_block(inode->i_sb,tmp);
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}
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brelse(dind_bh);
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return retry;
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}
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void minix_truncate(struct inode * inode)
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{
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int retry;
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if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
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S_ISLNK(inode->i_mode)))
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return;
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while (1) {
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retry = trunc_direct(inode);
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retry |= trunc_indirect(inode,7,inode->u.minix_i.i_data+7);
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retry |= trunc_dindirect(inode);
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if (!retry)
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break;
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current->counter = 0;
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schedule();
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}
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inode->i_mtime = inode->i_ctime = CURRENT_TIME;
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inode->i_dirt = 1;
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}
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