bitmap.c

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#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <asm/div64.h>
#include "omfs.h"

unsigned long omfs_count_free(struct super_block *sb)
{
    unsigned int i;
    unsigned long sum = 0;
    struct omfs_sb_info *sbi = OMFS_SB(sb);
    int nbits = sb->s_blocksize * 8;

    for (i = 0; i < sbi->s_imap_size; i++)
        sum += nbits - bitmap_weight(sbi->s_imap[i], nbits);

    return sum;
}

/*
 *  Counts the run of zero bits starting at bit up to max.
 *  It handles the case where a run might spill over a buffer.
 *  Called with bitmap lock.
 */
static int count_run(unsigned long **addr, int nbits,
        int addrlen, int bit, int max)
{
    int count = 0;
    int x;

    for (; addrlen > 0; addrlen--, addr++) {
        x = find_next_bit(*addr, nbits, bit);
        count += x - bit;

        if (x < nbits || count > max)
            return min(count, max);

        bit = 0;
    }
    return min(count, max);
}

/*
 * Sets or clears the run of count bits starting with bit.
 * Called with bitmap lock.
 */
static int set_run(struct super_block *sb, int map,
        int nbits, int bit, int count, int set)
{
    int i;
    int err;
    struct buffer_head *bh;
    struct omfs_sb_info *sbi = OMFS_SB(sb);

    err = -ENOMEM;
    bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
    if (!bh)
        goto out;

    for (i = 0; i < count; i++, bit++) {
        if (bit >= nbits) {
            bit = 0;
            map++;

            mark_buffer_dirty(bh);
            brelse(bh);
            bh = sb_bread(sb,
                clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
            if (!bh)
                goto out;
        }
        if (set) {
            set_bit(bit, sbi->s_imap[map]);
            set_bit(bit, (unsigned long *)bh->b_data);
        } else {
            clear_bit(bit, sbi->s_imap[map]);
            clear_bit(bit, (unsigned long *)bh->b_data);
        }
    }
    mark_buffer_dirty(bh);
    brelse(bh);
    err = 0;
out:
    return err;
}

/*
 * Tries to allocate exactly one block.  Returns true if successful.
 */
int omfs_allocate_block(struct super_block *sb, u64 block)
{
    struct buffer_head *bh;
    struct omfs_sb_info *sbi = OMFS_SB(sb);
    int bits_per_entry = 8 * sb->s_blocksize;
    unsigned int map, bit;
    int ret = 0;
    u64 tmp;

    tmp = block;
    bit = do_div(tmp, bits_per_entry);
    map = tmp;

    mutex_lock(&sbi->s_bitmap_lock);
    if (map >= sbi->s_imap_size || test_and_set_bit(bit, sbi->s_imap[map]))
        goto out;

    if (sbi->s_bitmap_ino > 0) {
        bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
        if (!bh)
            goto out;

        set_bit(bit, (unsigned long *)bh->b_data);
        mark_buffer_dirty(bh);
        brelse(bh);
    }
    ret = 1;
out:
    mutex_unlock(&sbi->s_bitmap_lock);
    return ret;
}


/*
 *  Tries to allocate a set of blocks.  The request size depends on the
 *  type: for inodes, we must allocate sbi->s_mirrors blocks, and for file
 *  blocks, we try to allocate sbi->s_clustersize, but can always get away
 *  with just one block.
 */
int omfs_allocate_range(struct super_block *sb,
            int min_request,
            int max_request,
            u64 *return_block,
            int *return_size)
{
    struct omfs_sb_info *sbi = OMFS_SB(sb);
    int bits_per_entry = 8 * sb->s_blocksize;
    int ret = 0;
    int i, run, bit;

    mutex_lock(&sbi->s_bitmap_lock);
    for (i = 0; i < sbi->s_imap_size; i++) {
        bit = 0;
        while (bit < bits_per_entry) {
            bit = find_next_zero_bit(sbi->s_imap[i], bits_per_entry,
                bit);

            if (bit == bits_per_entry)
                break;

            run = count_run(&sbi->s_imap[i], bits_per_entry,
                sbi->s_imap_size-i, bit, max_request);

            if (run >= min_request)
                goto found;
            bit += run;
        }
    }
    ret = -ENOSPC;
    goto out;

found:
    *return_block = i * bits_per_entry + bit;
    *return_size = run;
    ret = set_run(sb, i, bits_per_entry, bit, run, 1);

out:
    mutex_unlock(&sbi->s_bitmap_lock);
    return ret;
}

/*
 * Clears count bits starting at a given block.
 */
int omfs_clear_range(struct super_block *sb, u64 block, int count)
{
    struct omfs_sb_info *sbi = OMFS_SB(sb);
    int bits_per_entry = 8 * sb->s_blocksize;
    u64 tmp;
    unsigned int map, bit;
    int ret;

    tmp = block;
    bit = do_div(tmp, bits_per_entry);
    map = tmp;

    if (map >= sbi->s_imap_size)
        return 0;

    mutex_lock(&sbi->s_bitmap_lock);
    ret = set_run(sb, map, bits_per_entry, bit, count, 0);
    mutex_unlock(&sbi->s_bitmap_lock);
    return ret;
}