truncate.c

嵌入式系统设计与实验教材二源码linux内核移植与编译

/*
 *  linux/fs/ufs/truncate.c
 *
 * Copyright (C) 1998
 * Daniel Pirkl <[e-mail]>
 * Charles University, Faculty of Mathematics and Physics
 *
 *  from
 *
 *  linux/fs/ext2/truncate.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([e-mail])
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/truncate.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([e-mail]), 1995
 */

/*
 * Real random numbers for secure rm added 94/02/18
 * Idea from Pierre del Perugia <[e-mail]>
 */

#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/ufs_fs.h>
#include <linux/fcntl.h>
#include <linux/sched.h>
#include <linux/stat.h>
#include <linux/locks.h>
#include <linux/string.h>

#include "swab.h"
#include "util.h"

#undef UFS_TRUNCATE_DEBUG

#ifdef UFS_TRUNCATE_DEBUG
#define UFSD(x) printk("(%s, %d), %s: ", __FILE__, __LINE__, __FUNCTION__); printk x;
#else
#define UFSD(x)
#endif
 
/*
 * Secure deletion currently doesn't work. It interacts very badly
 * with buffers shared with memory mappings, and for that reason
 * can't be done in the truncate() routines. It should instead be
 * done separately in "release()" before calling the truncate routines
 * that will release the actual file blocks.
 *
 *		Linus
 */

#define DIRECT_BLOCK ((inode->i_size + uspi->s_bsize - 1) >> uspi->s_bshift)
#define DIRECT_FRAGMENT ((inode->i_size + uspi->s_fsize - 1) >> uspi->s_fshift)

#define DATA_BUFFER_USED(bh) \
	(atomic_read(&bh->b_count)>1 || buffer_locked(bh))

static int ufs_trunc_direct (struct inode * inode)
{
	struct super_block * sb;
	struct ufs_sb_private_info * uspi;
	struct buffer_head * bh;
	u32 * p;
	unsigned frag1, frag2, frag3, frag4, block1, block2;
	unsigned frag_to_free, free_count;
	unsigned i, j, tmp;
	int retry;
	
	UFSD(("ENTER\n"))

	sb = inode->i_sb;
	uspi = sb->u.ufs_sb.s_uspi;
	
	frag_to_free = 0;
	free_count = 0;
	retry = 0;
	
	frag1 = DIRECT_FRAGMENT;
	frag4 = min_t(u32, UFS_NDIR_FRAGMENT, inode->u.ufs_i.i_lastfrag);
	frag2 = ((frag1 & uspi->s_fpbmask) ? ((frag1 | uspi->s_fpbmask) + 1) : frag1);
	frag3 = frag4 & ~uspi->s_fpbmask;
	block1 = block2 = 0;
	if (frag2 > frag3) {
		frag2 = frag4;
		frag3 = frag4 = 0;
	}
	else if (frag2 < frag3) {
		block1 = ufs_fragstoblks (frag2);
		block2 = ufs_fragstoblks (frag3);
	}

	UFSD(("frag1 %u, frag2 %u, block1 %u, block2 %u, frag3 %u, frag4 %u\n", frag1, frag2, block1, block2, frag3, frag4))

	if (frag1 >= frag2)
		goto next1;		

	/*
	 * Free first free fragments
	 */
	p = inode->u.ufs_i.i_u1.i_data + ufs_fragstoblks (frag1);
	tmp = fs32_to_cpu(sb, *p);
	if (!tmp )
		ufs_panic (sb, "ufs_trunc_direct", "internal error");
	frag1 = ufs_fragnum (frag1);
	frag2 = ufs_fragnum (frag2);
	for (j = frag1; j < frag2; j++) {
		bh = sb_get_hash_table (sb, tmp + j);
		if ((bh && DATA_BUFFER_USED(bh)) || tmp != fs32_to_cpu(sb, *p)) {
			retry = 1;
			brelse (bh);
			goto next1;
		}
		bforget (bh);
	}
	inode->i_blocks -= (frag2-frag1) << uspi->s_nspfshift;
	mark_inode_dirty(inode);
	ufs_free_fragments (inode, tmp + frag1, frag2 - frag1);
	frag_to_free = tmp + frag1;

next1:
	/*
	 * Free whole blocks
	 */
	for (i = block1 ; i < block2; i++) {
		p = inode->u.ufs_i.i_u1.i_data + i;
		tmp = fs32_to_cpu(sb, *p);
		if (!tmp)
			continue;
		for (j = 0; j < uspi->s_fpb; j++) {
			bh = sb_get_hash_table(sb, tmp + j);
			if ((bh && DATA_BUFFER_USED(bh)) || tmp != fs32_to_cpu(sb, *p)) {
				retry = 1;
				brelse (bh);
				goto next2;
			}
			bforget (bh);
		}
		*p = 0;
		inode->i_blocks -= uspi->s_nspb;
		mark_inode_dirty(inode);
		if (free_count == 0) {
			frag_to_free = tmp;
			free_count = uspi->s_fpb;
		} else if (free_count > 0 && frag_to_free == tmp - free_count)
			free_count += uspi->s_fpb;
		else {
			ufs_free_blocks (inode, frag_to_free, free_count);
			frag_to_free = tmp;
			free_count = uspi->s_fpb;
		}
next2:;
	}
	
	if (free_count > 0)
		ufs_free_blocks (inode, frag_to_free, free_count);

	if (frag3 >= frag4)
		goto next3;

	/*
	 * Free last free fragments
	 */
	p = inode->u.ufs_i.i_u1.i_data + ufs_fragstoblks (frag3);
	tmp = fs32_to_cpu(sb, *p);
	if (!tmp )
		ufs_panic(sb, "ufs_truncate_direct", "internal error");
	frag4 = ufs_fragnum (frag4);
	for (j = 0; j < frag4; j++) {
		bh = sb_get_hash_table (sb, tmp + j);
		if ((bh && DATA_BUFFER_USED(bh)) || tmp != fs32_to_cpu(sb, *p)) {
			retry = 1;
			brelse (bh);
			goto next1;
		}
		bforget (bh);
	}
	*p = 0;
	inode->i_blocks -= frag4 << uspi->s_nspfshift;
	mark_inode_dirty(inode);
	ufs_free_fragments (inode, tmp, frag4);
 next3:

	UFSD(("EXIT\n"))
	return retry;
}


static int ufs_trunc_indirect (struct inode * inode, unsigned offset, u32 * p)
{
	struct super_block * sb;
	struct ufs_sb_private_info * uspi;
	struct ufs_buffer_head * ind_ubh;
	struct buffer_head * bh;
	u32 * ind;
	unsigned indirect_block, i, j, tmp;
	unsigned frag_to_free, free_count;
	int retry;

	UFSD(("ENTER\n"))
		
	sb = inode->i_sb;
	uspi = sb->u.ufs_sb.s_uspi;

	frag_to_free = 0;
	free_count = 0;
	retry = 0;
	
	tmp = fs32_to_cpu(sb, *p);
	if (!tmp)
		return 0;
	ind_ubh = ubh_bread(sb, tmp, uspi->s_bsize);
	if (tmp != fs32_to_cpu(sb, *p)) {
		ubh_brelse (ind_ubh);
		return 1;
	}
	if (!ind_ubh) {
		*p = 0;
		return 0;
	}

	indirect_block = (DIRECT_BLOCK > offset) ? (DIRECT_BLOCK - offset) : 0;
	for (i = indirect_block; i < uspi->s_apb; i++) {
		ind = ubh_get_addr32 (ind_ubh, i);
		tmp = fs32_to_cpu(sb, *ind);
		if (!tmp)
			continue;
		for (j = 0; j < uspi->s_fpb; j++) {
			bh = sb_get_hash_table(sb, tmp + j);
			if ((bh && DATA_BUFFER_USED(bh)) || tmp != fs32_to_cpu(sb, *ind)) {
				retry = 1;
				brelse (bh);
				goto next;
			}
			bforget (bh);
		}	
		*ind = 0;
		ubh_mark_buffer_dirty(ind_ubh);
		if (free_count == 0) {
			frag_to_free = tmp;
			free_count = uspi->s_fpb;
		} else if (free_count > 0 && frag_to_free == tmp - free_count)
			free_count += uspi->s_fpb;
		else {
			ufs_free_blocks (inode, frag_to_free, free_count);
			frag_to_free = tmp;
			free_count = uspi->s_fpb;
		}
		inode->i_blocks -= uspi->s_nspb;
		mark_inode_dirty(inode);
next:;
	}

	if (free_count > 0) {
		ufs_free_blocks (inode, frag_to_free, free_count);
	}
	for (i = 0; i < uspi->s_apb; i++)
		if (*ubh_get_addr32(ind_ubh,i))
			break;
	if (i >= uspi->s_apb) {
		if (ubh_max_bcount(ind_ubh) != 1) {
			retry = 1;
		}
		else {
			tmp = fs32_to_cpu(sb, *p);
			*p = 0;
			inode->i_blocks -= uspi->s_nspb;
			mark_inode_dirty(inode);
			ufs_free_blocks (inode, tmp, uspi->s_fpb);
			ubh_bforget(ind_ubh);
			ind_ubh = NULL;
		}
	}
	if (IS_SYNC(inode) && ind_ubh && ubh_buffer_dirty(ind_ubh)) {
		ubh_ll_rw_block (WRITE, 1, &ind_ubh);
		ubh_wait_on_buffer (ind_ubh);
	}
	ubh_brelse (ind_ubh);
	
	UFSD(("EXIT\n"))
	
	return retry;
}

static int ufs_trunc_dindirect (struct inode * inode, unsigned offset, u32 * p)
{
	struct super_block * sb;
	struct ufs_sb_private_info * uspi;
	struct ufs_buffer_head * dind_bh;
	unsigned i, tmp, dindirect_block;
	u32 * dind;
	int retry = 0;
	
	UFSD(("ENTER\n"))
	
	sb = inode->i_sb;
	uspi = sb->u.ufs_sb.s_uspi;

	dindirect_block = (DIRECT_BLOCK > offset) 
		? ((DIRECT_BLOCK - offset) >> uspi->s_apbshift) : 0;
	retry = 0;
	
	tmp = fs32_to_cpu(sb, *p);
	if (!tmp)
		return 0;
	dind_bh = ubh_bread(sb, tmp, uspi->s_bsize);
	if (tmp != fs32_to_cpu(sb, *p)) {
		ubh_brelse (dind_bh);
		return 1;
	}
	if (!dind_bh) {
		*p = 0;
		return 0;
	}

	for (i = dindirect_block ; i < uspi->s_apb ; i++) {
		dind = ubh_get_addr32 (dind_bh, i);
		tmp = fs32_to_cpu(sb, *dind);
		if (!tmp)
			continue;
		retry |= ufs_trunc_indirect (inode, offset + (i << uspi->s_apbshift), dind);
		ubh_mark_buffer_dirty(dind_bh);
	}

	for (i = 0; i < uspi->s_apb; i++)
		if (*ubh_get_addr32 (dind_bh, i))
			break;
	if (i >= uspi->s_apb) {
		if (ubh_max_bcount(dind_bh) != 1)
			retry = 1;
		else {
			tmp = fs32_to_cpu(sb, *p);
			*p = 0;
			inode->i_blocks -= uspi->s_nspb;
			mark_inode_dirty(inode);
			ufs_free_blocks (inode, tmp, uspi->s_fpb);
			ubh_bforget(dind_bh);
			dind_bh = NULL;
		}
	}
	if (IS_SYNC(inode) && dind_bh && ubh_buffer_dirty(dind_bh)) {
		ubh_ll_rw_block (WRITE, 1, &dind_bh);
		ubh_wait_on_buffer (dind_bh);
	}
	ubh_brelse (dind_bh);
	
	UFSD(("EXIT\n"))
	
	return retry;
}

static int ufs_trunc_tindirect (struct inode * inode)
{
	struct super_block * sb;
	struct ufs_sb_private_info * uspi;
	struct ufs_buffer_head * tind_bh;
	unsigned tindirect_block, tmp, i;
	u32 * tind, * p;
	int retry;
	
	UFSD(("ENTER\n"))

	sb = inode->i_sb;
	uspi = sb->u.ufs_sb.s_uspi;
	retry = 0;
	
	tindirect_block = (DIRECT_BLOCK > (UFS_NDADDR + uspi->s_apb + uspi->s_2apb))
		? ((DIRECT_BLOCK - UFS_NDADDR - uspi->s_apb - uspi->s_2apb) >> uspi->s_2apbshift) : 0;
	p = inode->u.ufs_i.i_u1.i_data + UFS_TIND_BLOCK;
	if (!(tmp = fs32_to_cpu(sb, *p)))
		return 0;
	tind_bh = ubh_bread (sb, tmp, uspi->s_bsize);
	if (tmp != fs32_to_cpu(sb, *p)) {
		ubh_brelse (tind_bh);
		return 1;
	}
	if (!tind_bh) {
		*p = 0;
		return 0;
	}

	for (i = tindirect_block ; i < uspi->s_apb ; i++) {
		tind = ubh_get_addr32 (tind_bh, i);
		retry |= ufs_trunc_dindirect(inode, UFS_NDADDR + 
			uspi->s_apb + ((i + 1) << uspi->s_2apbshift), tind);
		ubh_mark_buffer_dirty(tind_bh);
	}
	for (i = 0; i < uspi->s_apb; i++)
		if (*ubh_get_addr32 (tind_bh, i))
			break;
	if (i >= uspi->s_apb) {
		if (ubh_max_bcount(tind_bh) != 1)
			retry = 1;
		else {
			tmp = fs32_to_cpu(sb, *p);
			*p = 0;
			inode->i_blocks -= uspi->s_nspb;
			mark_inode_dirty(inode);
			ufs_free_blocks (inode, tmp, uspi->s_fpb);
			ubh_bforget(tind_bh);
			tind_bh = NULL;
		}
	}
	if (IS_SYNC(inode) && tind_bh && ubh_buffer_dirty(tind_bh)) {
		ubh_ll_rw_block (WRITE, 1, &tind_bh);
		ubh_wait_on_buffer (tind_bh);
	}
	ubh_brelse (tind_bh);
	
	UFSD(("EXIT\n"))
	return retry;
}
		
void ufs_truncate (struct inode * inode)
{
	struct super_block * sb;
	struct ufs_sb_private_info * uspi;
	struct buffer_head * bh;
	unsigned offset;
	int err, retry;
	
	UFSD(("ENTER\n"))
	sb = inode->i_sb;
	uspi = sb->u.ufs_sb.s_uspi;

	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)))
		return;
	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
		return;
	while (1) {
		retry = ufs_trunc_direct(inode);
		retry |= ufs_trunc_indirect (inode, UFS_IND_BLOCK,
			(u32 *) &inode->u.ufs_i.i_u1.i_data[UFS_IND_BLOCK]);
		retry |= ufs_trunc_dindirect (inode, UFS_IND_BLOCK + uspi->s_apb,
			(u32 *) &inode->u.ufs_i.i_u1.i_data[UFS_DIND_BLOCK]);
		retry |= ufs_trunc_tindirect (inode);
		if (!retry)
			break;
		if (IS_SYNC(inode) && (inode->i_state & I_DIRTY))
			ufs_sync_inode (inode);
		run_task_queue(&tq_disk);
		current->policy |= SCHED_YIELD;
		schedule ();


	}
	offset = inode->i_size & uspi->s_fshift;
	if (offset) {
		bh = ufs_bread (inode, inode->i_size >> uspi->s_fshift, 0, &err);
		if (bh) {
			memset (bh->b_data + offset, 0, uspi->s_fsize - offset);
			mark_buffer_dirty (bh);
			brelse (bh);
		}
	}
	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	inode->u.ufs_i.i_lastfrag = DIRECT_FRAGMENT;
	mark_inode_dirty(inode);
	UFSD(("EXIT\n"))
}