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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 "affs.h"

/* This is, of course, shamelessly stolen from fs/minix */

static const int nibblemap[] = { 0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4 };

static u32

affs_count_free_bits(u32 blocksize, const void *data)

{

        const u32 *map;

        u32 free;

        u32 tmp;

        map = data;

        free = 0;

        for (blocksize /= 4; blocksize > 0; blocksize--) {

                tmp = *map++;

                while (tmp) {

                        free += nibblemap[tmp & 0xf];

                        tmp >>= 4;

                }

        }

        return free;

}

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;

        down(&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;

        up(&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];

        down(&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);

        sb->s_dirt = 1;

        bm->bm_free++;

        up(&sbi->s_bmlock);

        return;

err_free:

        affs_warning(sb,"affs_free_block","Trying to free block %u which is already free", block);

        up(&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;

        up(&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. Therefor 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];

        down(&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);

        sb->s_dirt = 1;

        up(&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:

        up(&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 = affs_count_free_bits(sb->s_blocksize - 4, bh->b_data + 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 = affs_count_free_bits(sb->s_blocksize - 4, bh->b_data + 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;

}