extent.c

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/*
 *  linux/fs/hfs/extent.c
 *
 * Copyright (C) 1995-1997  Paul H. Hargrove
 * (C) 2003 Ardis Technologies <[email protected]>
 * This file may be distributed under the terms of the GNU General Public License.
 *
 * This file contains the functions related to the extents B-tree.
 */

#include <linux/pagemap.h>

#include "hfs_fs.h"
#include "btree.h"

/*================ File-local functions ================*/

/*
 * build_key
 */
static void hfs_ext_build_key(hfs_btree_key *key, u32 cnid, u16 block, u8 type)
{
    key->key_len = 7;
    key->ext.FkType = type;
    key->ext.FNum = cpu_to_be32(cnid);
    key->ext.FABN = cpu_to_be16(block);
}

/*
 * hfs_ext_compare()
 *
 * Description:
 *   This is the comparison function used for the extents B-tree.  In
 *   comparing extent B-tree entries, the file id is the most
 *   significant field (compared as unsigned ints); the fork type is
 *   the second most significant field (compared as unsigned chars);
 *   and the allocation block number field is the least significant
 *   (compared as unsigned ints).
 * Input Variable(s):
 *   struct hfs_ext_key *key1: pointer to the first key to compare
 *   struct hfs_ext_key *key2: pointer to the second key to compare
 * Output Variable(s):
 *   NONE
 * Returns:
 *   int: negative if key1<key2, positive if key1>key2, and 0 if key1==key2
 * Preconditions:
 *   key1 and key2 point to "valid" (struct hfs_ext_key)s.
 * Postconditions:
 *   This function has no side-effects */
int hfs_ext_keycmp(const btree_key *key1, const btree_key *key2)
{
    __be32 fnum1, fnum2;
    __be16 block1, block2;

    fnum1 = key1->ext.FNum;
    fnum2 = key2->ext.FNum;
    if (fnum1 != fnum2)
        return be32_to_cpu(fnum1) < be32_to_cpu(fnum2) ? -1 : 1;
    if (key1->ext.FkType != key2->ext.FkType)
        return key1->ext.FkType < key2->ext.FkType ? -1 : 1;

    block1 = key1->ext.FABN;
    block2 = key2->ext.FABN;
    if (block1 == block2)
        return 0;
    return be16_to_cpu(block1) < be16_to_cpu(block2) ? -1 : 1;
}

/*
 * hfs_ext_find_block
 *
 * Find a block within an extent record
 */
static u16 hfs_ext_find_block(struct hfs_extent *ext, u16 off)
{
    int i;
    u16 count;

    for (i = 0; i < 3; ext++, i++) {
        count = be16_to_cpu(ext->count);
        if (off < count)
            return be16_to_cpu(ext->block) + off;
        off -= count;
    }
    /* panic? */
    return 0;
}

static int hfs_ext_block_count(struct hfs_extent *ext)
{
    int i;
    u16 count = 0;

    for (i = 0; i < 3; ext++, i++)
        count += be16_to_cpu(ext->count);
    return count;
}

static u16 hfs_ext_lastblock(struct hfs_extent *ext)
{
    int i;

    ext += 2;
    for (i = 0; i < 2; ext--, i++)
        if (ext->count)
            break;
    return be16_to_cpu(ext->block) + be16_to_cpu(ext->count);
}

static void __hfs_ext_write_extent(struct inode *inode, struct hfs_find_data *fd)
{
    int res;

    hfs_ext_build_key(fd->search_key, inode->i_ino, HFS_I(inode)->cached_start,
              HFS_IS_RSRC(inode) ?  HFS_FK_RSRC : HFS_FK_DATA);
    res = hfs_brec_find(fd);
    if (HFS_I(inode)->flags & HFS_FLG_EXT_NEW) {
        if (res != -ENOENT)
            return;
        hfs_brec_insert(fd, HFS_I(inode)->cached_extents, sizeof(hfs_extent_rec));
        HFS_I(inode)->flags &= ~(HFS_FLG_EXT_DIRTY|HFS_FLG_EXT_NEW);
    } else {
        if (res)
            return;
        hfs_bnode_write(fd->bnode, HFS_I(inode)->cached_extents, fd->entryoffset, fd->entrylength);
        HFS_I(inode)->flags &= ~HFS_FLG_EXT_DIRTY;
    }
}

void hfs_ext_write_extent(struct inode *inode)
{
    struct hfs_find_data fd;

    if (HFS_I(inode)->flags & HFS_FLG_EXT_DIRTY) {
        hfs_find_init(HFS_SB(inode->i_sb)->ext_tree, &fd);
        __hfs_ext_write_extent(inode, &fd);
        hfs_find_exit(&fd);
    }
}

static inline int __hfs_ext_read_extent(struct hfs_find_data *fd, struct hfs_extent *extent,
                    u32 cnid, u32 block, u8 type)
{
    int res;

    hfs_ext_build_key(fd->search_key, cnid, block, type);
    fd->key->ext.FNum = 0;
    res = hfs_brec_find(fd);
    if (res && res != -ENOENT)
        return res;
    if (fd->key->ext.FNum != fd->search_key->ext.FNum ||
        fd->key->ext.FkType != fd->search_key->ext.FkType)
        return -ENOENT;
    if (fd->entrylength != sizeof(hfs_extent_rec))
        return -EIO;
    hfs_bnode_read(fd->bnode, extent, fd->entryoffset, sizeof(hfs_extent_rec));
    return 0;
}

static inline int __hfs_ext_cache_extent(struct hfs_find_data *fd, struct inode *inode, u32 block)
{
    int res;

    if (HFS_I(inode)->flags & HFS_FLG_EXT_DIRTY)
        __hfs_ext_write_extent(inode, fd);

    res = __hfs_ext_read_extent(fd, HFS_I(inode)->cached_extents, inode->i_ino,
                    block, HFS_IS_RSRC(inode) ? HFS_FK_RSRC : HFS_FK_DATA);
    if (!res) {
        HFS_I(inode)->cached_start = be16_to_cpu(fd->key->ext.FABN);
        HFS_I(inode)->cached_blocks = hfs_ext_block_count(HFS_I(inode)->cached_extents);
    } else {
        HFS_I(inode)->cached_start = HFS_I(inode)->cached_blocks = 0;
        HFS_I(inode)->flags &= ~(HFS_FLG_EXT_DIRTY|HFS_FLG_EXT_NEW);
    }
    return res;
}

static int hfs_ext_read_extent(struct inode *inode, u16 block)
{
    struct hfs_find_data fd;
    int res;

    if (block >= HFS_I(inode)->cached_start &&
        block < HFS_I(inode)->cached_start + HFS_I(inode)->cached_blocks)
        return 0;

    hfs_find_init(HFS_SB(inode->i_sb)->ext_tree, &fd);
    res = __hfs_ext_cache_extent(&fd, inode, block);
    hfs_find_exit(&fd);
    return res;
}

static void hfs_dump_extent(struct hfs_extent *extent)
{
    int i;

    dprint(DBG_EXTENT, "   ");
    for (i = 0; i < 3; i++)
        dprint(DBG_EXTENT, " %u:%u", be16_to_cpu(extent[i].block),
                 be16_to_cpu(extent[i].count));
    dprint(DBG_EXTENT, "\n");
}

static int hfs_add_extent(struct hfs_extent *extent, u16 offset,
              u16 alloc_block, u16 block_count)
{
    u16 count, start;
    int i;

    hfs_dump_extent(extent);
    for (i = 0; i < 3; extent++, i++) {
        count = be16_to_cpu(extent->count);
        if (offset == count) {
            start = be16_to_cpu(extent->block);
            if (alloc_block != start + count) {
                if (++i >= 3)
                    return -ENOSPC;
                extent++;
                extent->block = cpu_to_be16(alloc_block);
            } else
                block_count += count;
            extent->count = cpu_to_be16(block_count);
            return 0;
        } else if (offset < count)
            break;
        offset -= count;
    }
    /* panic? */
    return -EIO;
}

static int hfs_free_extents(struct super_block *sb, struct hfs_extent *extent,
                u16 offset, u16 block_nr)
{
    u16 count, start;
    int i;

    hfs_dump_extent(extent);
    for (i = 0; i < 3; extent++, i++) {
        count = be16_to_cpu(extent->count);
        if (offset == count)
            goto found;
        else if (offset < count)
            break;
        offset -= count;
    }
    /* panic? */
    return -EIO;
found:
    for (;;) {
        start = be16_to_cpu(extent->block);
        if (count <= block_nr) {
            hfs_clear_vbm_bits(sb, start, count);
            extent->block = 0;
            extent->count = 0;
            block_nr -= count;
        } else {
            count -= block_nr;
            hfs_clear_vbm_bits(sb, start + count, block_nr);
            extent->count = cpu_to_be16(count);
            block_nr = 0;
        }
        if (!block_nr || !i)
            return 0;
        i--;
        extent--;
        count = be16_to_cpu(extent->count);
    }
}

int hfs_free_fork(struct super_block *sb, struct hfs_cat_file *file, int type)
{
    struct hfs_find_data fd;
    u32 total_blocks, blocks, start;
    u32 cnid = be32_to_cpu(file->FlNum);
    struct hfs_extent *extent;
    int res, i;

    if (type == HFS_FK_DATA) {
        total_blocks = be32_to_cpu(file->PyLen);
        extent = file->ExtRec;
    } else {
        total_blocks = be32_to_cpu(file->RPyLen);
        extent = file->RExtRec;
    }
    total_blocks /= HFS_SB(sb)->alloc_blksz;
    if (!total_blocks)
        return 0;

    blocks = 0;
    for (i = 0; i < 3; extent++, i++)
        blocks += be16_to_cpu(extent[i].count);

    res = hfs_free_extents(sb, extent, blocks, blocks);
    if (res)
        return res;
    if (total_blocks == blocks)
        return 0;

    hfs_find_init(HFS_SB(sb)->ext_tree, &fd);
    do {
        res = __hfs_ext_read_extent(&fd, extent, cnid, total_blocks, type);
        if (res)
            break;
        start = be16_to_cpu(fd.key->ext.FABN);
        hfs_free_extents(sb, extent, total_blocks - start, total_blocks);
        hfs_brec_remove(&fd);
        total_blocks = start;
    } while (total_blocks > blocks);
    hfs_find_exit(&fd);

    return res;
}

/*
 * hfs_get_block
 */
int hfs_get_block(struct inode *inode, sector_t block,
          struct buffer_head *bh_result, int create)
{
    struct super_block *sb;
    u16 dblock, ablock;
    int res;

    sb = inode->i_sb;
    /* Convert inode block to disk allocation block */
    ablock = (u32)block / HFS_SB(sb)->fs_div;

    if (block >= HFS_I(inode)->fs_blocks) {
        if (block > HFS_I(inode)->fs_blocks || !create)
            return -EIO;
        if (ablock >= HFS_I(inode)->alloc_blocks) {
            res = hfs_extend_file(inode);
            if (res)
                return res;
        }
    } else
        create = 0;

    if (ablock < HFS_I(inode)->first_blocks) {
        dblock = hfs_ext_find_block(HFS_I(inode)->first_extents, ablock);
        goto done;
    }

    mutex_lock(&HFS_I(inode)->extents_lock);
    res = hfs_ext_read_extent(inode, ablock);
    if (!res)
        dblock = hfs_ext_find_block(HFS_I(inode)->cached_extents,
                        ablock - HFS_I(inode)->cached_start);
    else {
        mutex_unlock(&HFS_I(inode)->extents_lock);
        return -EIO;
    }
    mutex_unlock(&HFS_I(inode)->extents_lock);

done:
    map_bh(bh_result, sb, HFS_SB(sb)->fs_start +
           dblock * HFS_SB(sb)->fs_div +
           (u32)block % HFS_SB(sb)->fs_div);

    if (create) {
        set_buffer_new(bh_result);
        HFS_I(inode)->phys_size += sb->s_blocksize;
        HFS_I(inode)->fs_blocks++;
        inode_add_bytes(inode, sb->s_blocksize);
        mark_inode_dirty(inode);
    }
    return 0;
}

int hfs_extend_file(struct inode *inode)
{
    struct super_block *sb = inode->i_sb;
    u32 start, len, goal;
    int res;

    mutex_lock(&HFS_I(inode)->extents_lock);
    if (HFS_I(inode)->alloc_blocks == HFS_I(inode)->first_blocks)
        goal = hfs_ext_lastblock(HFS_I(inode)->first_extents);
    else {
        res = hfs_ext_read_extent(inode, HFS_I(inode)->alloc_blocks);
        if (res)
            goto out;
        goal = hfs_ext_lastblock(HFS_I(inode)->cached_extents);
    }

    len = HFS_I(inode)->clump_blocks;
    start = hfs_vbm_search_free(sb, goal, &len);
    if (!len) {
        res = -ENOSPC;
        goto out;
    }

    dprint(DBG_EXTENT, "extend %lu: %u,%u\n", inode->i_ino, start, len);
    if (HFS_I(inode)->alloc_blocks == HFS_I(inode)->first_blocks) {
        if (!HFS_I(inode)->first_blocks) {
            dprint(DBG_EXTENT, "first extents\n");
            /* no extents yet */
            HFS_I(inode)->first_extents[0].block = cpu_to_be16(start);
            HFS_I(inode)->first_extents[0].count = cpu_to_be16(len);
            res = 0;
        } else {
            /* try to append to extents in inode */
            res = hfs_add_extent(HFS_I(inode)->first_extents,
                         HFS_I(inode)->alloc_blocks,
                         start, len);
            if (res == -ENOSPC)
                goto insert_extent;
        }
        if (!res) {
            hfs_dump_extent(HFS_I(inode)->first_extents);
            HFS_I(inode)->first_blocks += len;
        }
    } else {
        res = hfs_add_extent(HFS_I(inode)->cached_extents,
                     HFS_I(inode)->alloc_blocks -
                     HFS_I(inode)->cached_start,
                     start, len);
        if (!res) {
            hfs_dump_extent(HFS_I(inode)->cached_extents);
            HFS_I(inode)->flags |= HFS_FLG_EXT_DIRTY;
            HFS_I(inode)->cached_blocks += len;
        } else if (res == -ENOSPC)
            goto insert_extent;
    }
out:
    mutex_unlock(&HFS_I(inode)->extents_lock);
    if (!res) {
        HFS_I(inode)->alloc_blocks += len;
        mark_inode_dirty(inode);
        if (inode->i_ino < HFS_FIRSTUSER_CNID)
            set_bit(HFS_FLG_ALT_MDB_DIRTY, &HFS_SB(sb)->flags);
        set_bit(HFS_FLG_MDB_DIRTY, &HFS_SB(sb)->flags);
        hfs_mark_mdb_dirty(sb);
    }
    return res;

insert_extent:
    dprint(DBG_EXTENT, "insert new extent\n");
    hfs_ext_write_extent(inode);

    memset(HFS_I(inode)->cached_extents, 0, sizeof(hfs_extent_rec));
    HFS_I(inode)->cached_extents[0].block = cpu_to_be16(start);
    HFS_I(inode)->cached_extents[0].count = cpu_to_be16(len);
    hfs_dump_extent(HFS_I(inode)->cached_extents);
    HFS_I(inode)->flags |= HFS_FLG_EXT_DIRTY|HFS_FLG_EXT_NEW;
    HFS_I(inode)->cached_start = HFS_I(inode)->alloc_blocks;
    HFS_I(inode)->cached_blocks = len;

    res = 0;
    goto out;
}

void hfs_file_truncate(struct inode *inode)
{
    struct super_block *sb = inode->i_sb;
    struct hfs_find_data fd;
    u16 blk_cnt, alloc_cnt, start;
    u32 size;
    int res;

    dprint(DBG_INODE, "truncate: %lu, %Lu -> %Lu\n", inode->i_ino,
           (long long)HFS_I(inode)->phys_size, inode->i_size);
    if (inode->i_size > HFS_I(inode)->phys_size) {
        struct address_space *mapping = inode->i_mapping;
        void *fsdata;
        struct page *page;
        int res;

        /* XXX: Can use generic_cont_expand? */
        size = inode->i_size - 1;
        res = pagecache_write_begin(NULL, mapping, size+1, 0,
                AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
        if (!res) {
            res = pagecache_write_end(NULL, mapping, size+1, 0, 0,
                    page, fsdata);
        }
        if (res)
            inode->i_size = HFS_I(inode)->phys_size;
        return;
    } else if (inode->i_size == HFS_I(inode)->phys_size)
        return;
    size = inode->i_size + HFS_SB(sb)->alloc_blksz - 1;
    blk_cnt = size / HFS_SB(sb)->alloc_blksz;
    alloc_cnt = HFS_I(inode)->alloc_blocks;
    if (blk_cnt == alloc_cnt)
        goto out;

    mutex_lock(&HFS_I(inode)->extents_lock);
    hfs_find_init(HFS_SB(sb)->ext_tree, &fd);
    while (1) {
        if (alloc_cnt == HFS_I(inode)->first_blocks) {
            hfs_free_extents(sb, HFS_I(inode)->first_extents,
                     alloc_cnt, alloc_cnt - blk_cnt);
            hfs_dump_extent(HFS_I(inode)->first_extents);
            HFS_I(inode)->first_blocks = blk_cnt;
            break;
        }
        res = __hfs_ext_cache_extent(&fd, inode, alloc_cnt);
        if (res)
            break;
        start = HFS_I(inode)->cached_start;
        hfs_free_extents(sb, HFS_I(inode)->cached_extents,
                 alloc_cnt - start, alloc_cnt - blk_cnt);
        hfs_dump_extent(HFS_I(inode)->cached_extents);
        if (blk_cnt > start) {
            HFS_I(inode)->flags |= HFS_FLG_EXT_DIRTY;
            break;
        }
        alloc_cnt = start;
        HFS_I(inode)->cached_start = HFS_I(inode)->cached_blocks = 0;
        HFS_I(inode)->flags &= ~(HFS_FLG_EXT_DIRTY|HFS_FLG_EXT_NEW);
        hfs_brec_remove(&fd);
    }
    hfs_find_exit(&fd);
    mutex_unlock(&HFS_I(inode)->extents_lock);

    HFS_I(inode)->alloc_blocks = blk_cnt;
out:
    HFS_I(inode)->phys_size = inode->i_size;
    HFS_I(inode)->fs_blocks = (inode->i_size + sb->s_blocksize - 1) >> sb->s_blocksize_bits;
    inode_set_bytes(inode, HFS_I(inode)->fs_blocks << sb->s_blocksize_bits);
    mark_inode_dirty(inode);
}