bitmap.c

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/*
 *  linux/fs/minix/bitmap.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * Modified for 680x0 by Hamish Macdonald
 * Fixed for 680x0 by Andreas Schwab
 */

/* bitmap.c contains the code that handles the inode and block bitmaps */

#include "minix.h"
#include <linux/buffer_head.h>
#include <linux/bitops.h>
#include <linux/sched.h>

static DEFINE_SPINLOCK(bitmap_lock);

/*
 * bitmap consists of blocks filled with 16bit words
 * bit set == busy, bit clear == free
 * endianness is a mess, but for counting zero bits it really doesn't matter...
 */
static __u32 count_free(struct buffer_head *map[], unsigned blocksize, __u32 numbits)
{
    __u32 sum = 0;
    unsigned blocks = DIV_ROUND_UP(numbits, blocksize * 8);

    while (blocks--) {
        unsigned words = blocksize / 2;
        __u16 *p = (__u16 *)(*map++)->b_data;
        while (words--)
            sum += 16 - hweight16(*p++);
    }

    return sum;
}

void minix_free_block(struct inode *inode, unsigned long block)
{
    struct super_block *sb = inode->i_sb;
    struct minix_sb_info *sbi = minix_sb(sb);
    struct buffer_head *bh;
    int k = sb->s_blocksize_bits + 3;
    unsigned long bit, zone;

    if (block < sbi->s_firstdatazone || block >= sbi->s_nzones) {
        printk("Trying to free block not in datazone\n");
        return;
    }
    zone = block - sbi->s_firstdatazone + 1;
    bit = zone & ((1<<k) - 1);
    zone >>= k;
    if (zone >= sbi->s_zmap_blocks) {
        printk("minix_free_block: nonexistent bitmap buffer\n");
        return;
    }
    bh = sbi->s_zmap[zone];
    spin_lock(&bitmap_lock);
    if (!minix_test_and_clear_bit(bit, bh->b_data))
        printk("minix_free_block (%s:%lu): bit already cleared\n",
               sb->s_id, block);
    spin_unlock(&bitmap_lock);
    mark_buffer_dirty(bh);
    return;
}

int minix_new_block(struct inode * inode)
{
    struct minix_sb_info *sbi = minix_sb(inode->i_sb);
    int bits_per_zone = 8 * inode->i_sb->s_blocksize;
    int i;

    for (i = 0; i < sbi->s_zmap_blocks; i++) {
        struct buffer_head *bh = sbi->s_zmap[i];
        int j;

        spin_lock(&bitmap_lock);
        j = minix_find_first_zero_bit(bh->b_data, bits_per_zone);
        if (j < bits_per_zone) {
            minix_set_bit(j, bh->b_data);
            spin_unlock(&bitmap_lock);
            mark_buffer_dirty(bh);
            j += i * bits_per_zone + sbi->s_firstdatazone-1;
            if (j < sbi->s_firstdatazone || j >= sbi->s_nzones)
                break;
            return j;
        }
        spin_unlock(&bitmap_lock);
    }
    return 0;
}

unsigned long minix_count_free_blocks(struct super_block *sb)
{
    struct minix_sb_info *sbi = minix_sb(sb);
    u32 bits = sbi->s_nzones - (sbi->s_firstdatazone + 1);

    return (count_free(sbi->s_zmap, sb->s_blocksize, bits)
        << sbi->s_log_zone_size);
}

struct minix_inode *
minix_V1_raw_inode(struct super_block *sb, ino_t ino, struct buffer_head **bh)
{
    int block;
    struct minix_sb_info *sbi = minix_sb(sb);
    struct minix_inode *p;

    if (!ino || ino > sbi->s_ninodes) {
        printk("Bad inode number on dev %s: %ld is out of range\n",
               sb->s_id, (long)ino);
        return NULL;
    }
    ino--;
    block = 2 + sbi->s_imap_blocks + sbi->s_zmap_blocks +
         ino / MINIX_INODES_PER_BLOCK;
    *bh = sb_bread(sb, block);
    if (!*bh) {
        printk("Unable to read inode block\n");
        return NULL;
    }
    p = (void *)(*bh)->b_data;
    return p + ino % MINIX_INODES_PER_BLOCK;
}

struct minix2_inode *
minix_V2_raw_inode(struct super_block *sb, ino_t ino, struct buffer_head **bh)
{
    int block;
    struct minix_sb_info *sbi = minix_sb(sb);
    struct minix2_inode *p;
    int minix2_inodes_per_block = sb->s_blocksize / sizeof(struct minix2_inode);

    *bh = NULL;
    if (!ino || ino > sbi->s_ninodes) {
        printk("Bad inode number on dev %s: %ld is out of range\n",
               sb->s_id, (long)ino);
        return NULL;
    }
    ino--;
    block = 2 + sbi->s_imap_blocks + sbi->s_zmap_blocks +
         ino / minix2_inodes_per_block;
    *bh = sb_bread(sb, block);
    if (!*bh) {
        printk("Unable to read inode block\n");
        return NULL;
    }
    p = (void *)(*bh)->b_data;
    return p + ino % minix2_inodes_per_block;
}

/* Clear the link count and mode of a deleted inode on disk. */

static void minix_clear_inode(struct inode *inode)
{
    struct buffer_head *bh = NULL;

    if (INODE_VERSION(inode) == MINIX_V1) {
        struct minix_inode *raw_inode;
        raw_inode = minix_V1_raw_inode(inode->i_sb, inode->i_ino, &bh);
        if (raw_inode) {
            raw_inode->i_nlinks = 0;
            raw_inode->i_mode = 0;
        }
    } else {
        struct minix2_inode *raw_inode;
        raw_inode = minix_V2_raw_inode(inode->i_sb, inode->i_ino, &bh);
        if (raw_inode) {
            raw_inode->i_nlinks = 0;
            raw_inode->i_mode = 0;
        }
    }
    if (bh) {
        mark_buffer_dirty(bh);
        brelse (bh);
    }
}

void minix_free_inode(struct inode * inode)
{
    struct super_block *sb = inode->i_sb;
    struct minix_sb_info *sbi = minix_sb(inode->i_sb);
    struct buffer_head *bh;
    int k = sb->s_blocksize_bits + 3;
    unsigned long ino, bit;

    ino = inode->i_ino;
    if (ino < 1 || ino > sbi->s_ninodes) {
        printk("minix_free_inode: inode 0 or nonexistent inode\n");
        return;
    }
    bit = ino & ((1<<k) - 1);
    ino >>= k;
    if (ino >= sbi->s_imap_blocks) {
        printk("minix_free_inode: nonexistent imap in superblock\n");
        return;
    }

    minix_clear_inode(inode);   /* clear on-disk copy */

    bh = sbi->s_imap[ino];
    spin_lock(&bitmap_lock);
    if (!minix_test_and_clear_bit(bit, bh->b_data))
        printk("minix_free_inode: bit %lu already cleared\n", bit);
    spin_unlock(&bitmap_lock);
    mark_buffer_dirty(bh);
}

struct inode *minix_new_inode(const struct inode *dir, umode_t mode, int *error)
{
    struct super_block *sb = dir->i_sb;
    struct minix_sb_info *sbi = minix_sb(sb);
    struct inode *inode = new_inode(sb);
    struct buffer_head * bh;
    int bits_per_zone = 8 * sb->s_blocksize;
    unsigned long j;
    int i;

    if (!inode) {
        *error = -ENOMEM;
        return NULL;
    }
    j = bits_per_zone;
    bh = NULL;
    *error = -ENOSPC;
    spin_lock(&bitmap_lock);
    for (i = 0; i < sbi->s_imap_blocks; i++) {
        bh = sbi->s_imap[i];
        j = minix_find_first_zero_bit(bh->b_data, bits_per_zone);
        if (j < bits_per_zone)
            break;
    }
    if (!bh || j >= bits_per_zone) {
        spin_unlock(&bitmap_lock);
        iput(inode);
        return NULL;
    }
    if (minix_test_and_set_bit(j, bh->b_data)) {    /* shouldn't happen */
        spin_unlock(&bitmap_lock);
        printk("minix_new_inode: bit already set\n");
        iput(inode);
        return NULL;
    }
    spin_unlock(&bitmap_lock);
    mark_buffer_dirty(bh);
    j += i * bits_per_zone;
    if (!j || j > sbi->s_ninodes) {
        iput(inode);
        return NULL;
    }
    inode_init_owner(inode, dir, mode);
    inode->i_ino = j;
    inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;
    inode->i_blocks = 0;
    memset(&minix_i(inode)->u, 0, sizeof(minix_i(inode)->u));
    insert_inode_hash(inode);
    mark_inode_dirty(inode);

    *error = 0;
    return inode;
}

unsigned long minix_count_free_inodes(struct super_block *sb)
{
    struct minix_sb_info *sbi = minix_sb(sb);
    u32 bits = sbi->s_ninodes + 1;

    return count_free(sbi->s_imap, sb->s_blocksize, bits);
}