/*
 *  linux/fs/sysv/balloc.c
 *
 *  minix/bitmap.c
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  ext/freelists.c
 *  Copyright (C) 1992  Remy Card (card@masi.ibp.fr)
 *
 *  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;
        }

        lock_super(sb);
        count = fs16_to_cpu(sbi, *sbi->s_bcache_count);

        if (count > sbi->s_flc_size) {
                printk("sysv_free_block: flc_count > flc_size\n");
                unlock_super(sb);
                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");
                        unlock_super(sb);
                        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);
        unlock_super(sb);
}

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;

        lock_super(sb);
        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);
        unlock_super(sb);
        return nr;

Enospc:
        unlock_super(sb);
        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;

        lock_super(sb);
        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:
        unlock_super(sb);
        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;
}