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/*

 *  linux/fs/sysv/truncate.c

 *

 *  minix/truncate.c

 *  Copyright (C) 1991, 1992  Linus Torvalds

 *

 *  coh/truncate.c

 *  Copyright (C) 1993  Pascal Haible, Bruno Haible

 *

 *  sysv/truncate.c

 *  Copyright (C) 1993  Bruno Haible

 */

#include <linux/sched.h>

#include <linux/fs.h>

#include <linux/sysv_fs.h>

#include <linux/stat.h>

/* Linus' implementation of truncate.

 * It doesn't need locking because it can tell from looking at bh->b_count

 * whether a given block is in use elsewhere.

 */

/*

 * Truncate has the most races in the whole filesystem: coding it is

 * a pain in the a**. Especially as I don't do any locking...

 *

 * The code may look a bit weird, but that's just because I've tried to

 * handle things like file-size changes in a somewhat graceful manner.

 * Anyway, truncating a file at the same time somebody else writes to it

 * is likely to result in pretty weird behaviour...

 *

 * The new code handles normal truncates (size = 0) as well as the more

 * general case (size = XXX). I hope.

 */

/* We throw away any data beyond inode->i_size. */

static int trunc_direct(struct inode * inode)

{

        struct super_block * sb;

        unsigned int i;

        unsigned long * p;

        unsigned long block;

        struct buffer_head * bh;

        int retry = 0;

        sb = inode->i_sb;

repeat:

        for (i = ((unsigned long) inode->i_size + sb->sv_block_size_1) >> sb->sv_block_size_bits; i < 10; i++) {

                p = inode->u.sysv_i.i_data + i;

                block = *p;

                if (!block)

                        continue;

                bh = sv_get_hash_table(sb, inode->i_dev, block);

                if ((i << sb->sv_block_size_bits) < inode->i_size) {

                        brelse(bh);

                        goto repeat;

                }

                if ((bh && bh->b_count != 1) || (block != *p)) {

                        retry = 1;

                        brelse(bh);

                        continue;

                }

                *p = 0;

                inode->i_dirt = 1;

                brelse(bh);

                sysv_free_block(sb,block);

        }

        return retry;

}

static int trunc_indirect(struct inode * inode, unsigned long offset, unsigned long * p, int convert, unsigned char * dirt)

{

        unsigned long indtmp, indblock;

        struct super_block * sb;

        struct buffer_head * indbh;

        unsigned int i;

        sysv_zone_t * ind;

        unsigned long tmp, block;

        struct buffer_head * bh;

        int retry = 0;

        indblock = indtmp = *p;

        if (convert)

                indblock = from_coh_ulong(indblock);

        if (!indblock)

                return 0;

        sb = inode->i_sb;

        indbh = sv_bread(sb, inode->i_dev, indblock);

        if (indtmp != *p) {

                brelse(indbh);

                return 1;

        }

        if (!indbh) {

                *p = 0;

                *dirt = 1;

                return 0;

        }

repeat:

        if (inode->i_size < offset)

                i = 0;

        else

                i = (inode->i_size - offset + sb->sv_block_size_1) >> sb->sv_block_size_bits;

        for (; i < sb->sv_ind_per_block; i++) {

                ind = ((sysv_zone_t *) indbh->b_data) + i;

                block = tmp = *ind;

                if (sb->sv_convert)

                        block = from_coh_ulong(block);

                if (!block)

                        continue;

                bh = sv_get_hash_table(sb, inode->i_dev, block);

                if ((i << sb->sv_block_size_bits) + offset < inode->i_size) {

                        brelse(bh);

                        goto repeat;

                }

                if ((bh && bh->b_count != 1) || (tmp != *ind)) {

                        retry = 1;

                        brelse(bh);

                        continue;

                }

                *ind = 0;

                mark_buffer_dirty(indbh, 1);

                brelse(bh);

                sysv_free_block(sb,block);

        }

        for (i = 0; i < sb->sv_ind_per_block; i++)

                if (((sysv_zone_t *) indbh->b_data)[i])

                        goto done;

        if ((indbh->b_count != 1) || (indtmp != *p)) {

                brelse(indbh);

                return 1;

        }

        *p = 0;

        *dirt = 1;

        sysv_free_block(sb,indblock);

done:

        brelse(indbh);

        return retry;

}

static int trunc_dindirect(struct inode * inode, unsigned long offset, unsigned long * p, int convert, unsigned char * dirt)

{

        unsigned long indtmp, indblock;

        struct super_block * sb;

        struct buffer_head * indbh;

        unsigned int i;

        sysv_zone_t * ind;

        unsigned long tmp, block;

        int retry = 0;

        indblock = indtmp = *p;

        if (convert)

                indblock = from_coh_ulong(indblock);

        if (!indblock)

                return 0;

        sb = inode->i_sb;

        indbh = sv_bread(sb, inode->i_dev, indblock);

        if (indtmp != *p) {

                brelse(indbh);

                return 1;

        }

        if (!indbh) {

                *p = 0;

                *dirt = 1;

                return 0;

        }

        if (inode->i_size < offset)

                i = 0;

        else

                i = (inode->i_size - offset + sb->sv_ind_per_block_block_size_1) >> sb->sv_ind_per_block_block_size_bits;

        for (; i < sb->sv_ind_per_block; i++) {

                unsigned char dirty = 0;

                ind = ((sysv_zone_t *) indbh->b_data) + i;

                block = tmp = *ind;

                if (sb->sv_convert)

                        block = from_coh_ulong(block);

                if (!block)

                        continue;

                retry |= trunc_indirect(inode,offset+(i<<sb->sv_ind_per_block_bits),ind,sb->sv_convert,&dirty);

                if (dirty)

                        mark_buffer_dirty(indbh, 1);

        }

        for (i = 0; i < sb->sv_ind_per_block; i++)

                if (((sysv_zone_t *) indbh->b_data)[i])

                        goto done;

        if ((indbh->b_count != 1) || (indtmp != *p)) {

                brelse(indbh);

                return 1;

        }

        *p = 0;

        *dirt = 1;

        sysv_free_block(sb,indblock);

done:

        brelse(indbh);

        return retry;

}

static int trunc_tindirect(struct inode * inode, unsigned long offset, unsigned long * p, int convert, unsigned char * dirt)

{

        unsigned long indtmp, indblock;

        struct super_block * sb;

        struct buffer_head * indbh;

        unsigned int i;

        sysv_zone_t * ind;

        unsigned long tmp, block;

        int retry = 0;

        indblock = indtmp = *p;

        if (convert)

                indblock = from_coh_ulong(indblock);

        if (!indblock)

                return 0;

        sb = inode->i_sb;

        indbh = sv_bread(sb, inode->i_dev, indblock);

        if (indtmp != *p) {

                brelse(indbh);

                return 1;

        }

        if (!indbh) {

                *p = 0;

                *dirt = 1;

                return 0;

        }

        if (inode->i_size < offset)

                i = 0;

        else

                i = (inode->i_size - offset + sb->sv_ind_per_block_2_block_size_1) >> sb->sv_ind_per_block_2_block_size_bits;

        for (; i < sb->sv_ind_per_block; i++) {

                unsigned char dirty = 0;

                ind = ((sysv_zone_t *) indbh->b_data) + i;

                block = tmp = *ind;

                if (sb->sv_convert)

                        block = from_coh_ulong(block);

                if (!block)

                        continue;

                retry |= trunc_dindirect(inode,offset+(i<<sb->sv_ind_per_block_2_bits),ind,sb->sv_convert,&dirty);

                if (dirty)

                        mark_buffer_dirty(indbh, 1);

        }

        for (i = 0; i < sb->sv_ind_per_block; i++)

                if (((sysv_zone_t *) indbh->b_data)[i])

                        goto done;

        if ((indbh->b_count != 1) || (indtmp != *p)) {

                brelse(indbh);

                return 1;

        }

        *p = 0;

        *dirt = 1;

        sysv_free_block(sb,indblock);

done:

        brelse(indbh);

        return retry;

}

static int trunc_all(struct inode * inode)

{

        struct super_block * sb;

        sb = inode->i_sb;

        return trunc_direct(inode)

             | trunc_indirect(inode,sb->sv_ind0_size,&inode->u.sysv_i.i_data[10],0,&inode->i_dirt)

             | trunc_dindirect(inode,sb->sv_ind1_size,&inode->u.sysv_i.i_data[11],0,&inode->i_dirt)

             | trunc_tindirect(inode,sb->sv_ind2_size,&inode->u.sysv_i.i_data[12],0,&inode->i_dirt);

}

void sysv_truncate(struct inode * inode)

{

        /* If this is called from sysv_put_inode, we needn't worry about

         * races as we are just losing the last reference to the inode.

         * If this is called from another place, let's hope it's a regular

         * file.

         * Truncating symbolic links is strange. We assume we don't truncate

         * a directory we are just modifying. We ensure we don't truncate

         * a regular file we are just writing to, by use of a lock.

         */

        if (S_ISLNK(inode->i_mode))

                printk("sysv_truncate: truncating symbolic link\n");

        else if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))

                return;

        while (trunc_all(inode)) {

                current->counter = 0;

                schedule();

        }

        inode->i_mtime = inode->i_ctime = CURRENT_TIME;

        inode->i_dirt = 1;

}