bitmap.c

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/*
 *  linux/fs/affs/bitmap.c
 *
 *  (c) 1996 Hans-Joachim Widmaier
 *
 *  bitmap.c contains the code that handles all bitmap related stuff -
 *  block allocation, deallocation, calculation of free space.
 */

#include <linux/slab.h>
#include "affs.h"

u32
affs_count_free_blocks(struct super_block *sb)
{
    struct affs_bm_info *bm;
    u32 free;
    int i;

    pr_debug("AFFS: count_free_blocks()\n");

    if (sb->s_flags & MS_RDONLY)
        return 0;

    mutex_lock(&AFFS_SB(sb)->s_bmlock);

    bm = AFFS_SB(sb)->s_bitmap;
    free = 0;
    for (i = AFFS_SB(sb)->s_bmap_count; i > 0; bm++, i--)
        free += bm->bm_free;

    mutex_unlock(&AFFS_SB(sb)->s_bmlock);

    return free;
}

void
affs_free_block(struct super_block *sb, u32 block)
{
    struct affs_sb_info *sbi = AFFS_SB(sb);
    struct affs_bm_info *bm;
    struct buffer_head *bh;
    u32 blk, bmap, bit, mask, tmp;
    __be32 *data;

    pr_debug("AFFS: free_block(%u)\n", block);

    if (block > sbi->s_partition_size)
        goto err_range;

    blk     = block - sbi->s_reserved;
    bmap    = blk / sbi->s_bmap_bits;
    bit     = blk % sbi->s_bmap_bits;
    bm      = &sbi->s_bitmap[bmap];

    mutex_lock(&sbi->s_bmlock);

    bh = sbi->s_bmap_bh;
    if (sbi->s_last_bmap != bmap) {
        affs_brelse(bh);
        bh = affs_bread(sb, bm->bm_key);
        if (!bh)
            goto err_bh_read;
        sbi->s_bmap_bh = bh;
        sbi->s_last_bmap = bmap;
    }

    mask = 1 << (bit & 31);
    data = (__be32 *)bh->b_data + bit / 32 + 1;

    /* mark block free */
    tmp = be32_to_cpu(*data);
    if (tmp & mask)
        goto err_free;
    *data = cpu_to_be32(tmp | mask);

    /* fix checksum */
    tmp = be32_to_cpu(*(__be32 *)bh->b_data);
    *(__be32 *)bh->b_data = cpu_to_be32(tmp - mask);

    mark_buffer_dirty(bh);
    affs_mark_sb_dirty(sb);
    bm->bm_free++;

    mutex_unlock(&sbi->s_bmlock);
    return;

err_free:
    affs_warning(sb,"affs_free_block","Trying to free block %u which is already free", block);
    mutex_unlock(&sbi->s_bmlock);
    return;

err_bh_read:
    affs_error(sb,"affs_free_block","Cannot read bitmap block %u", bm->bm_key);
    sbi->s_bmap_bh = NULL;
    sbi->s_last_bmap = ~0;
    mutex_unlock(&sbi->s_bmlock);
    return;

err_range:
    affs_error(sb, "affs_free_block","Block %u outside partition", block);
    return;
}

/*
 * Allocate a block in the given allocation zone.
 * Since we have to byte-swap the bitmap on little-endian
 * machines, this is rather expensive. Therefore we will
 * preallocate up to 16 blocks from the same word, if
 * possible. We are not doing preallocations in the
 * header zone, though.
 */

u32
affs_alloc_block(struct inode *inode, u32 goal)
{
    struct super_block *sb;
    struct affs_sb_info *sbi;
    struct affs_bm_info *bm;
    struct buffer_head *bh;
    __be32 *data, *enddata;
    u32 blk, bmap, bit, mask, mask2, tmp;
    int i;

    sb = inode->i_sb;
    sbi = AFFS_SB(sb);

    pr_debug("AFFS: balloc(inode=%lu,goal=%u): ", inode->i_ino, goal);

    if (AFFS_I(inode)->i_pa_cnt) {
        pr_debug("%d\n", AFFS_I(inode)->i_lastalloc+1);
        AFFS_I(inode)->i_pa_cnt--;
        return ++AFFS_I(inode)->i_lastalloc;
    }

    if (!goal || goal > sbi->s_partition_size) {
        if (goal)
            affs_warning(sb, "affs_balloc", "invalid goal %d", goal);
        //if (!AFFS_I(inode)->i_last_block)
        //  affs_warning(sb, "affs_balloc", "no last alloc block");
        goal = sbi->s_reserved;
    }

    blk = goal - sbi->s_reserved;
    bmap = blk / sbi->s_bmap_bits;
    bm = &sbi->s_bitmap[bmap];

    mutex_lock(&sbi->s_bmlock);

    if (bm->bm_free)
        goto find_bmap_bit;

find_bmap:
    /* search for the next bmap buffer with free bits */
    i = sbi->s_bmap_count;
    do {
        if (--i < 0)
            goto err_full;
        bmap++;
        bm++;
        if (bmap < sbi->s_bmap_count)
            continue;
        /* restart search at zero */
        bmap = 0;
        bm = sbi->s_bitmap;
    } while (!bm->bm_free);
    blk = bmap * sbi->s_bmap_bits;

find_bmap_bit:

    bh = sbi->s_bmap_bh;
    if (sbi->s_last_bmap != bmap) {
        affs_brelse(bh);
        bh = affs_bread(sb, bm->bm_key);
        if (!bh)
            goto err_bh_read;
        sbi->s_bmap_bh = bh;
        sbi->s_last_bmap = bmap;
    }

    /* find an unused block in this bitmap block */
    bit = blk % sbi->s_bmap_bits;
    data = (__be32 *)bh->b_data + bit / 32 + 1;
    enddata = (__be32 *)((u8 *)bh->b_data + sb->s_blocksize);
    mask = ~0UL << (bit & 31);
    blk &= ~31UL;

    tmp = be32_to_cpu(*data);
    if (tmp & mask)
        goto find_bit;

    /* scan the rest of the buffer */
    do {
        blk += 32;
        if (++data >= enddata)
            /* didn't find something, can only happen
             * if scan didn't start at 0, try next bmap
             */
            goto find_bmap;
    } while (!*data);
    tmp = be32_to_cpu(*data);
    mask = ~0;

find_bit:
    /* finally look for a free bit in the word */
    bit = ffs(tmp & mask) - 1;
    blk += bit + sbi->s_reserved;
    mask2 = mask = 1 << (bit & 31);
    AFFS_I(inode)->i_lastalloc = blk;

    /* prealloc as much as possible within this word */
    while ((mask2 <<= 1)) {
        if (!(tmp & mask2))
            break;
        AFFS_I(inode)->i_pa_cnt++;
        mask |= mask2;
    }
    bm->bm_free -= AFFS_I(inode)->i_pa_cnt + 1;

    *data = cpu_to_be32(tmp & ~mask);

    /* fix checksum */
    tmp = be32_to_cpu(*(__be32 *)bh->b_data);
    *(__be32 *)bh->b_data = cpu_to_be32(tmp + mask);

    mark_buffer_dirty(bh);
    affs_mark_sb_dirty(sb);

    mutex_unlock(&sbi->s_bmlock);

    pr_debug("%d\n", blk);
    return blk;

err_bh_read:
    affs_error(sb,"affs_read_block","Cannot read bitmap block %u", bm->bm_key);
    sbi->s_bmap_bh = NULL;
    sbi->s_last_bmap = ~0;
err_full:
    mutex_unlock(&sbi->s_bmlock);
    pr_debug("failed\n");
    return 0;
}

int affs_init_bitmap(struct super_block *sb, int *flags)
{
    struct affs_bm_info *bm;
    struct buffer_head *bmap_bh = NULL, *bh = NULL;
    __be32 *bmap_blk;
    u32 size, blk, end, offset, mask;
    int i, res = 0;
    struct affs_sb_info *sbi = AFFS_SB(sb);

    if (*flags & MS_RDONLY)
        return 0;

    if (!AFFS_ROOT_TAIL(sb, sbi->s_root_bh)->bm_flag) {
        printk(KERN_NOTICE "AFFS: Bitmap invalid - mounting %s read only\n",
            sb->s_id);
        *flags |= MS_RDONLY;
        return 0;
    }

    sbi->s_last_bmap = ~0;
    sbi->s_bmap_bh = NULL;
    sbi->s_bmap_bits = sb->s_blocksize * 8 - 32;
    sbi->s_bmap_count = (sbi->s_partition_size - sbi->s_reserved +
                 sbi->s_bmap_bits - 1) / sbi->s_bmap_bits;
    size = sbi->s_bmap_count * sizeof(*bm);
    bm = sbi->s_bitmap = kzalloc(size, GFP_KERNEL);
    if (!sbi->s_bitmap) {
        printk(KERN_ERR "AFFS: Bitmap allocation failed\n");
        return -ENOMEM;
    }

    bmap_blk = (__be32 *)sbi->s_root_bh->b_data;
    blk = sb->s_blocksize / 4 - 49;
    end = blk + 25;

    for (i = sbi->s_bmap_count; i > 0; bm++, i--) {
        affs_brelse(bh);

        bm->bm_key = be32_to_cpu(bmap_blk[blk]);
        bh = affs_bread(sb, bm->bm_key);
        if (!bh) {
            printk(KERN_ERR "AFFS: Cannot read bitmap\n");
            res = -EIO;
            goto out;
        }
        if (affs_checksum_block(sb, bh)) {
            printk(KERN_WARNING "AFFS: Bitmap %u invalid - mounting %s read only.\n",
                   bm->bm_key, sb->s_id);
            *flags |= MS_RDONLY;
            goto out;
        }
        pr_debug("AFFS: read bitmap block %d: %d\n", blk, bm->bm_key);
        bm->bm_free = memweight(bh->b_data + 4, sb->s_blocksize - 4);

        /* Don't try read the extension if this is the last block,
         * but we also need the right bm pointer below
         */
        if (++blk < end || i == 1)
            continue;
        if (bmap_bh)
            affs_brelse(bmap_bh);
        bmap_bh = affs_bread(sb, be32_to_cpu(bmap_blk[blk]));
        if (!bmap_bh) {
            printk(KERN_ERR "AFFS: Cannot read bitmap extension\n");
            res = -EIO;
            goto out;
        }
        bmap_blk = (__be32 *)bmap_bh->b_data;
        blk = 0;
        end = sb->s_blocksize / 4 - 1;
    }

    offset = (sbi->s_partition_size - sbi->s_reserved) % sbi->s_bmap_bits;
    mask = ~(0xFFFFFFFFU << (offset & 31));
    pr_debug("last word: %d %d %d\n", offset, offset / 32 + 1, mask);
    offset = offset / 32 + 1;

    if (mask) {
        u32 old, new;

        /* Mark unused bits in the last word as allocated */
        old = be32_to_cpu(((__be32 *)bh->b_data)[offset]);
        new = old & mask;
        //if (old != new) {
            ((__be32 *)bh->b_data)[offset] = cpu_to_be32(new);
            /* fix checksum */
            //new -= old;
            //old = be32_to_cpu(*(__be32 *)bh->b_data);
            //*(__be32 *)bh->b_data = cpu_to_be32(old - new);
            //mark_buffer_dirty(bh);
        //}
        /* correct offset for the bitmap count below */
        //offset++;
    }
    while (++offset < sb->s_blocksize / 4)
        ((__be32 *)bh->b_data)[offset] = 0;
    ((__be32 *)bh->b_data)[0] = 0;
    ((__be32 *)bh->b_data)[0] = cpu_to_be32(-affs_checksum_block(sb, bh));
    mark_buffer_dirty(bh);

    /* recalculate bitmap count for last block */
    bm--;
    bm->bm_free = memweight(bh->b_data + 4, sb->s_blocksize - 4);

out:
    affs_brelse(bh);
    affs_brelse(bmap_bh);
    return res;
}

void affs_free_bitmap(struct super_block *sb)
{
    struct affs_sb_info *sbi = AFFS_SB(sb);

    if (!sbi->s_bitmap)
        return;

    affs_brelse(sbi->s_bmap_bh);
    sbi->s_bmap_bh = NULL;
    sbi->s_last_bmap = ~0;
    kfree(sbi->s_bitmap);
    sbi->s_bitmap = NULL;
}