balloc.c

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/*
 *  linux/fs/sysv/balloc.c
 *
 *  minix/bitmap.c
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  ext/freelists.c
 *  Copyright (C) 1992  Remy Card ([email protected])
 *
 *  xenix/alloc.c
 *  Copyright (C) 1992  Doug Evans
 *
 *  coh/alloc.c
 *  Copyright (C) 1993  Pascal Haible, Bruno Haible
 *
 *  sysv/balloc.c
 *  Copyright (C) 1993  Bruno Haible
 *
 *  This file contains code for allocating/freeing blocks.
 */

#include <linux/buffer_head.h>
#include <linux/string.h>
#include "sysv.h"

/* We don't trust the value of
   sb->sv_sbd2->s_tfree = *sb->sv_free_blocks
   but we nevertheless keep it up to date. */

static inline sysv_zone_t *get_chunk(struct super_block *sb, struct buffer_head *bh)
{
    char *bh_data = bh->b_data;

    if (SYSV_SB(sb)->s_type == FSTYPE_SYSV4)
        return (sysv_zone_t*)(bh_data+4);
    else
        return (sysv_zone_t*)(bh_data+2);
}

/* NOTE NOTE NOTE: nr is a block number _as_ _stored_ _on_ _disk_ */

void sysv_free_block(struct super_block * sb, sysv_zone_t nr)
{
    struct sysv_sb_info * sbi = SYSV_SB(sb);
    struct buffer_head * bh;
    sysv_zone_t *blocks = sbi->s_bcache;
    unsigned count;
    unsigned block = fs32_to_cpu(sbi, nr);

    /*
     * This code does not work at all for AFS (it has a bitmap
     * free list).  As AFS is supposed to be read-only no one
     * should call this for an AFS filesystem anyway...
     */
    if (sbi->s_type == FSTYPE_AFS)
        return;

    if (block < sbi->s_firstdatazone || block >= sbi->s_nzones) {
        printk("sysv_free_block: trying to free block not in datazone\n");
        return;
    }

    mutex_lock(&sbi->s_lock);
    count = fs16_to_cpu(sbi, *sbi->s_bcache_count);

    if (count > sbi->s_flc_size) {
        printk("sysv_free_block: flc_count > flc_size\n");
        mutex_unlock(&sbi->s_lock);
        return;
    }
    /* If the free list head in super-block is full, it is copied
     * into this block being freed, ditto if it's completely empty
     * (applies only on Coherent).
     */
    if (count == sbi->s_flc_size || count == 0) {
        block += sbi->s_block_base;
        bh = sb_getblk(sb, block);
        if (!bh) {
            printk("sysv_free_block: getblk() failed\n");
            mutex_unlock(&sbi->s_lock);
            return;
        }
        memset(bh->b_data, 0, sb->s_blocksize);
        *(__fs16*)bh->b_data = cpu_to_fs16(sbi, count);
        memcpy(get_chunk(sb,bh), blocks, count * sizeof(sysv_zone_t));
        mark_buffer_dirty(bh);
        set_buffer_uptodate(bh);
        brelse(bh);
        count = 0;
    }
    sbi->s_bcache[count++] = nr;

    *sbi->s_bcache_count = cpu_to_fs16(sbi, count);
    fs32_add(sbi, sbi->s_free_blocks, 1);
    dirty_sb(sb);
    mutex_unlock(&sbi->s_lock);
}

sysv_zone_t sysv_new_block(struct super_block * sb)
{
    struct sysv_sb_info *sbi = SYSV_SB(sb);
    unsigned int block;
    sysv_zone_t nr;
    struct buffer_head * bh;
    unsigned count;

    mutex_lock(&sbi->s_lock);
    count = fs16_to_cpu(sbi, *sbi->s_bcache_count);

    if (count == 0) /* Applies only to Coherent FS */
        goto Enospc;
    nr = sbi->s_bcache[--count];
    if (nr == 0)  /* Applies only to Xenix FS, SystemV FS */
        goto Enospc;

    block = fs32_to_cpu(sbi, nr);

    *sbi->s_bcache_count = cpu_to_fs16(sbi, count);

    if (block < sbi->s_firstdatazone || block >= sbi->s_nzones) {
        printk("sysv_new_block: new block %d is not in data zone\n",
            block);
        goto Enospc;
    }

    if (count == 0) { /* the last block continues the free list */
        unsigned count;

        block += sbi->s_block_base;
        if (!(bh = sb_bread(sb, block))) {
            printk("sysv_new_block: cannot read free-list block\n");
            /* retry this same block next time */
            *sbi->s_bcache_count = cpu_to_fs16(sbi, 1);
            goto Enospc;
        }
        count = fs16_to_cpu(sbi, *(__fs16*)bh->b_data);
        if (count > sbi->s_flc_size) {
            printk("sysv_new_block: free-list block with >flc_size entries\n");
            brelse(bh);
            goto Enospc;
        }
        *sbi->s_bcache_count = cpu_to_fs16(sbi, count);
        memcpy(sbi->s_bcache, get_chunk(sb, bh),
                count * sizeof(sysv_zone_t));
        brelse(bh);
    }
    /* Now the free list head in the superblock is valid again. */
    fs32_add(sbi, sbi->s_free_blocks, -1);
    dirty_sb(sb);
    mutex_unlock(&sbi->s_lock);
    return nr;

Enospc:
    mutex_unlock(&sbi->s_lock);
    return 0;
}

unsigned long sysv_count_free_blocks(struct super_block * sb)
{
    struct sysv_sb_info * sbi = SYSV_SB(sb);
    int sb_count;
    int count;
    struct buffer_head * bh = NULL;
    sysv_zone_t *blocks;
    unsigned block;
    int n;

    /*
     * This code does not work at all for AFS (it has a bitmap
     * free list).  As AFS is supposed to be read-only we just
     * lie and say it has no free block at all.
     */
    if (sbi->s_type == FSTYPE_AFS)
        return 0;

    mutex_lock(&sbi->s_lock);
    sb_count = fs32_to_cpu(sbi, *sbi->s_free_blocks);

    if (0)
        goto trust_sb;

    /* this causes a lot of disk traffic ... */
    count = 0;
    n = fs16_to_cpu(sbi, *sbi->s_bcache_count);
    blocks = sbi->s_bcache;
    while (1) {
        sysv_zone_t zone;
        if (n > sbi->s_flc_size)
            goto E2big;
        zone = 0;
        while (n && (zone = blocks[--n]) != 0)
            count++;
        if (zone == 0)
            break;

        block = fs32_to_cpu(sbi, zone);
        if (bh)
            brelse(bh);

        if (block < sbi->s_firstdatazone || block >= sbi->s_nzones)
            goto Einval;
        block += sbi->s_block_base;
        bh = sb_bread(sb, block);
        if (!bh)
            goto Eio;
        n = fs16_to_cpu(sbi, *(__fs16*)bh->b_data);
        blocks = get_chunk(sb, bh);
    }
    if (bh)
        brelse(bh);
    if (count != sb_count)
        goto Ecount;
done:
    mutex_unlock(&sbi->s_lock);
    return count;

Einval:
    printk("sysv_count_free_blocks: new block %d is not in data zone\n",
        block);
    goto trust_sb;
Eio:
    printk("sysv_count_free_blocks: cannot read free-list block\n");
    goto trust_sb;
E2big:
    printk("sysv_count_free_blocks: >flc_size entries in free-list block\n");
    if (bh)
        brelse(bh);
trust_sb:
    count = sb_count;
    goto done;
Ecount:
    printk("sysv_count_free_blocks: free block count was %d, "
        "correcting to %d\n", sb_count, count);
    if (!(sb->s_flags & MS_RDONLY)) {
        *sbi->s_free_blocks = cpu_to_fs32(sbi, count);
        dirty_sb(sb);
    }
    goto done;
}