file.c

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/*
 *  linux/fs/affs/file.c
 *
 *  (c) 1996  Hans-Joachim Widmaier - Rewritten
 *
 *  (C) 1993  Ray Burr - Modified for Amiga FFS filesystem.
 *
 *  (C) 1992  Eric Youngdale Modified for ISO 9660 filesystem.
 *
 *  (C) 1991  Linus Torvalds - minix filesystem
 *
 *  affs regular file handling primitives
 */

#include "affs.h"

#if PAGE_SIZE < 4096
#error PAGE_SIZE must be at least 4096
#endif

static int affs_grow_extcache(struct inode *inode, u32 lc_idx);
static struct buffer_head *affs_alloc_extblock(struct inode *inode, struct buffer_head *bh, u32 ext);
static inline struct buffer_head *affs_get_extblock(struct inode *inode, u32 ext);
static struct buffer_head *affs_get_extblock_slow(struct inode *inode, u32 ext);
static int affs_file_open(struct inode *inode, struct file *filp);
static int affs_file_release(struct inode *inode, struct file *filp);

const struct file_operations affs_file_operations = {
    .llseek     = generic_file_llseek,
    .read       = do_sync_read,
    .aio_read   = generic_file_aio_read,
    .write      = do_sync_write,
    .aio_write  = generic_file_aio_write,
    .mmap       = generic_file_mmap,
    .open       = affs_file_open,
    .release    = affs_file_release,
    .fsync      = affs_file_fsync,
    .splice_read    = generic_file_splice_read,
};

const struct inode_operations affs_file_inode_operations = {
    .truncate   = affs_truncate,
    .setattr    = affs_notify_change,
};

static int
affs_file_open(struct inode *inode, struct file *filp)
{
    pr_debug("AFFS: open(%lu,%d)\n",
         inode->i_ino, atomic_read(&AFFS_I(inode)->i_opencnt));
    atomic_inc(&AFFS_I(inode)->i_opencnt);
    return 0;
}

static int
affs_file_release(struct inode *inode, struct file *filp)
{
    pr_debug("AFFS: release(%lu, %d)\n",
         inode->i_ino, atomic_read(&AFFS_I(inode)->i_opencnt));

    if (atomic_dec_and_test(&AFFS_I(inode)->i_opencnt)) {
        mutex_lock(&inode->i_mutex);
        if (inode->i_size != AFFS_I(inode)->mmu_private)
            affs_truncate(inode);
        affs_free_prealloc(inode);
        mutex_unlock(&inode->i_mutex);
    }

    return 0;
}

static int
affs_grow_extcache(struct inode *inode, u32 lc_idx)
{
    struct super_block  *sb = inode->i_sb;
    struct buffer_head  *bh;
    u32 lc_max;
    int i, j, key;

    if (!AFFS_I(inode)->i_lc) {
        char *ptr = (char *)get_zeroed_page(GFP_NOFS);
        if (!ptr)
            return -ENOMEM;
        AFFS_I(inode)->i_lc = (u32 *)ptr;
        AFFS_I(inode)->i_ac = (struct affs_ext_key *)(ptr + AFFS_CACHE_SIZE / 2);
    }

    lc_max = AFFS_LC_SIZE << AFFS_I(inode)->i_lc_shift;

    if (AFFS_I(inode)->i_extcnt > lc_max) {
        u32 lc_shift, lc_mask, tmp, off;

        /* need to recalculate linear cache, start from old size */
        lc_shift = AFFS_I(inode)->i_lc_shift;
        tmp = (AFFS_I(inode)->i_extcnt / AFFS_LC_SIZE) >> lc_shift;
        for (; tmp; tmp >>= 1)
            lc_shift++;
        lc_mask = (1 << lc_shift) - 1;

        /* fix idx and old size to new shift */
        lc_idx >>= (lc_shift - AFFS_I(inode)->i_lc_shift);
        AFFS_I(inode)->i_lc_size >>= (lc_shift - AFFS_I(inode)->i_lc_shift);

        /* first shrink old cache to make more space */
        off = 1 << (lc_shift - AFFS_I(inode)->i_lc_shift);
        for (i = 1, j = off; j < AFFS_LC_SIZE; i++, j += off)
            AFFS_I(inode)->i_ac[i] = AFFS_I(inode)->i_ac[j];

        AFFS_I(inode)->i_lc_shift = lc_shift;
        AFFS_I(inode)->i_lc_mask = lc_mask;
    }

    /* fill cache to the needed index */
    i = AFFS_I(inode)->i_lc_size;
    AFFS_I(inode)->i_lc_size = lc_idx + 1;
    for (; i <= lc_idx; i++) {
        if (!i) {
            AFFS_I(inode)->i_lc[0] = inode->i_ino;
            continue;
        }
        key = AFFS_I(inode)->i_lc[i - 1];
        j = AFFS_I(inode)->i_lc_mask + 1;
        // unlock cache
        for (; j > 0; j--) {
            bh = affs_bread(sb, key);
            if (!bh)
                goto err;
            key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
            affs_brelse(bh);
        }
        // lock cache
        AFFS_I(inode)->i_lc[i] = key;
    }

    return 0;

err:
    // lock cache
    return -EIO;
}

static struct buffer_head *
affs_alloc_extblock(struct inode *inode, struct buffer_head *bh, u32 ext)
{
    struct super_block *sb = inode->i_sb;
    struct buffer_head *new_bh;
    u32 blocknr, tmp;

    blocknr = affs_alloc_block(inode, bh->b_blocknr);
    if (!blocknr)
        return ERR_PTR(-ENOSPC);

    new_bh = affs_getzeroblk(sb, blocknr);
    if (!new_bh) {
        affs_free_block(sb, blocknr);
        return ERR_PTR(-EIO);
    }

    AFFS_HEAD(new_bh)->ptype = cpu_to_be32(T_LIST);
    AFFS_HEAD(new_bh)->key = cpu_to_be32(blocknr);
    AFFS_TAIL(sb, new_bh)->stype = cpu_to_be32(ST_FILE);
    AFFS_TAIL(sb, new_bh)->parent = cpu_to_be32(inode->i_ino);
    affs_fix_checksum(sb, new_bh);

    mark_buffer_dirty_inode(new_bh, inode);

    tmp = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
    if (tmp)
        affs_warning(sb, "alloc_ext", "previous extension set (%x)", tmp);
    AFFS_TAIL(sb, bh)->extension = cpu_to_be32(blocknr);
    affs_adjust_checksum(bh, blocknr - tmp);
    mark_buffer_dirty_inode(bh, inode);

    AFFS_I(inode)->i_extcnt++;
    mark_inode_dirty(inode);

    return new_bh;
}

static inline struct buffer_head *
affs_get_extblock(struct inode *inode, u32 ext)
{
    /* inline the simplest case: same extended block as last time */
    struct buffer_head *bh = AFFS_I(inode)->i_ext_bh;
    if (ext == AFFS_I(inode)->i_ext_last)
        get_bh(bh);
    else
        /* we have to do more (not inlined) */
        bh = affs_get_extblock_slow(inode, ext);

    return bh;
}

static struct buffer_head *
affs_get_extblock_slow(struct inode *inode, u32 ext)
{
    struct super_block *sb = inode->i_sb;
    struct buffer_head *bh;
    u32 ext_key;
    u32 lc_idx, lc_off, ac_idx;
    u32 tmp, idx;

    if (ext == AFFS_I(inode)->i_ext_last + 1) {
        /* read the next extended block from the current one */
        bh = AFFS_I(inode)->i_ext_bh;
        ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
        if (ext < AFFS_I(inode)->i_extcnt)
            goto read_ext;
        if (ext > AFFS_I(inode)->i_extcnt)
            BUG();
        bh = affs_alloc_extblock(inode, bh, ext);
        if (IS_ERR(bh))
            return bh;
        goto store_ext;
    }

    if (ext == 0) {
        /* we seek back to the file header block */
        ext_key = inode->i_ino;
        goto read_ext;
    }

    if (ext >= AFFS_I(inode)->i_extcnt) {
        struct buffer_head *prev_bh;

        /* allocate a new extended block */
        if (ext > AFFS_I(inode)->i_extcnt)
            BUG();

        /* get previous extended block */
        prev_bh = affs_get_extblock(inode, ext - 1);
        if (IS_ERR(prev_bh))
            return prev_bh;
        bh = affs_alloc_extblock(inode, prev_bh, ext);
        affs_brelse(prev_bh);
        if (IS_ERR(bh))
            return bh;
        goto store_ext;
    }

again:
    /* check if there is an extended cache and whether it's large enough */
    lc_idx = ext >> AFFS_I(inode)->i_lc_shift;
    lc_off = ext & AFFS_I(inode)->i_lc_mask;

    if (lc_idx >= AFFS_I(inode)->i_lc_size) {
        int err;

        err = affs_grow_extcache(inode, lc_idx);
        if (err)
            return ERR_PTR(err);
        goto again;
    }

    /* every n'th key we find in the linear cache */
    if (!lc_off) {
        ext_key = AFFS_I(inode)->i_lc[lc_idx];
        goto read_ext;
    }

    /* maybe it's still in the associative cache */
    ac_idx = (ext - lc_idx - 1) & AFFS_AC_MASK;
    if (AFFS_I(inode)->i_ac[ac_idx].ext == ext) {
        ext_key = AFFS_I(inode)->i_ac[ac_idx].key;
        goto read_ext;
    }

    /* try to find one of the previous extended blocks */
    tmp = ext;
    idx = ac_idx;
    while (--tmp, --lc_off > 0) {
        idx = (idx - 1) & AFFS_AC_MASK;
        if (AFFS_I(inode)->i_ac[idx].ext == tmp) {
            ext_key = AFFS_I(inode)->i_ac[idx].key;
            goto find_ext;
        }
    }

    /* fall back to the linear cache */
    ext_key = AFFS_I(inode)->i_lc[lc_idx];
find_ext:
    /* read all extended blocks until we find the one we need */
    //unlock cache
    do {
        bh = affs_bread(sb, ext_key);
        if (!bh)
            goto err_bread;
        ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
        affs_brelse(bh);
        tmp++;
    } while (tmp < ext);
    //lock cache

    /* store it in the associative cache */
    // recalculate ac_idx?
    AFFS_I(inode)->i_ac[ac_idx].ext = ext;
    AFFS_I(inode)->i_ac[ac_idx].key = ext_key;

read_ext:
    /* finally read the right extended block */
    //unlock cache
    bh = affs_bread(sb, ext_key);
    if (!bh)
        goto err_bread;
    //lock cache

store_ext:
    /* release old cached extended block and store the new one */
    affs_brelse(AFFS_I(inode)->i_ext_bh);
    AFFS_I(inode)->i_ext_last = ext;
    AFFS_I(inode)->i_ext_bh = bh;
    get_bh(bh);

    return bh;

err_bread:
    affs_brelse(bh);
    return ERR_PTR(-EIO);
}

static int
affs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh_result, int create)
{
    struct super_block  *sb = inode->i_sb;
    struct buffer_head  *ext_bh;
    u32          ext;

    pr_debug("AFFS: get_block(%u, %lu)\n", (u32)inode->i_ino, (unsigned long)block);

    BUG_ON(block > (sector_t)0x7fffffffUL);

    if (block >= AFFS_I(inode)->i_blkcnt) {
        if (block > AFFS_I(inode)->i_blkcnt || !create)
            goto err_big;
    } else
        create = 0;

    //lock cache
    affs_lock_ext(inode);

    ext = (u32)block / AFFS_SB(sb)->s_hashsize;
    block -= ext * AFFS_SB(sb)->s_hashsize;
    ext_bh = affs_get_extblock(inode, ext);
    if (IS_ERR(ext_bh))
        goto err_ext;
    map_bh(bh_result, sb, (sector_t)be32_to_cpu(AFFS_BLOCK(sb, ext_bh, block)));

    if (create) {
        u32 blocknr = affs_alloc_block(inode, ext_bh->b_blocknr);
        if (!blocknr)
            goto err_alloc;
        set_buffer_new(bh_result);
        AFFS_I(inode)->mmu_private += AFFS_SB(sb)->s_data_blksize;
        AFFS_I(inode)->i_blkcnt++;

        /* store new block */
        if (bh_result->b_blocknr)
            affs_warning(sb, "get_block", "block already set (%x)", bh_result->b_blocknr);
        AFFS_BLOCK(sb, ext_bh, block) = cpu_to_be32(blocknr);
        AFFS_HEAD(ext_bh)->block_count = cpu_to_be32(block + 1);
        affs_adjust_checksum(ext_bh, blocknr - bh_result->b_blocknr + 1);
        bh_result->b_blocknr = blocknr;

        if (!block) {
            /* insert first block into header block */
            u32 tmp = be32_to_cpu(AFFS_HEAD(ext_bh)->first_data);
            if (tmp)
                affs_warning(sb, "get_block", "first block already set (%d)", tmp);
            AFFS_HEAD(ext_bh)->first_data = cpu_to_be32(blocknr);
            affs_adjust_checksum(ext_bh, blocknr - tmp);
        }
    }

    affs_brelse(ext_bh);
    //unlock cache
    affs_unlock_ext(inode);
    return 0;

err_big:
    affs_error(inode->i_sb,"get_block","strange block request %d", block);
    return -EIO;
err_ext:
    // unlock cache
    affs_unlock_ext(inode);
    return PTR_ERR(ext_bh);
err_alloc:
    brelse(ext_bh);
    clear_buffer_mapped(bh_result);
    bh_result->b_bdev = NULL;
    // unlock cache
    affs_unlock_ext(inode);
    return -ENOSPC;
}

static int affs_writepage(struct page *page, struct writeback_control *wbc)
{
    return block_write_full_page(page, affs_get_block, wbc);
}

static int affs_readpage(struct file *file, struct page *page)
{
    return block_read_full_page(page, affs_get_block);
}

static int affs_write_begin(struct file *file, struct address_space *mapping,
            loff_t pos, unsigned len, unsigned flags,
            struct page **pagep, void **fsdata)
{
    int ret;

    *pagep = NULL;
    ret = cont_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
                affs_get_block,
                &AFFS_I(mapping->host)->mmu_private);
    if (unlikely(ret)) {
        loff_t isize = mapping->host->i_size;
        if (pos + len > isize)
            vmtruncate(mapping->host, isize);
    }

    return ret;
}

static sector_t _affs_bmap(struct address_space *mapping, sector_t block)
{
    return generic_block_bmap(mapping,block,affs_get_block);
}

const struct address_space_operations affs_aops = {
    .readpage = affs_readpage,
    .writepage = affs_writepage,
    .write_begin = affs_write_begin,
    .write_end = generic_write_end,
    .bmap = _affs_bmap
};

static inline struct buffer_head *
affs_bread_ino(struct inode *inode, int block, int create)
{
    struct buffer_head *bh, tmp_bh;
    int err;

    tmp_bh.b_state = 0;
    err = affs_get_block(inode, block, &tmp_bh, create);
    if (!err) {
        bh = affs_bread(inode->i_sb, tmp_bh.b_blocknr);
        if (bh) {
            bh->b_state |= tmp_bh.b_state;
            return bh;
        }
        err = -EIO;
    }
    return ERR_PTR(err);
}

static inline struct buffer_head *
affs_getzeroblk_ino(struct inode *inode, int block)
{
    struct buffer_head *bh, tmp_bh;
    int err;

    tmp_bh.b_state = 0;
    err = affs_get_block(inode, block, &tmp_bh, 1);
    if (!err) {
        bh = affs_getzeroblk(inode->i_sb, tmp_bh.b_blocknr);
        if (bh) {
            bh->b_state |= tmp_bh.b_state;
            return bh;
        }
        err = -EIO;
    }
    return ERR_PTR(err);
}

static inline struct buffer_head *
affs_getemptyblk_ino(struct inode *inode, int block)
{
    struct buffer_head *bh, tmp_bh;
    int err;

    tmp_bh.b_state = 0;
    err = affs_get_block(inode, block, &tmp_bh, 1);
    if (!err) {
        bh = affs_getemptyblk(inode->i_sb, tmp_bh.b_blocknr);
        if (bh) {
            bh->b_state |= tmp_bh.b_state;
            return bh;
        }
        err = -EIO;
    }
    return ERR_PTR(err);
}

static int
affs_do_readpage_ofs(struct file *file, struct page *page, unsigned from, unsigned to)
{
    struct inode *inode = page->mapping->host;
    struct super_block *sb = inode->i_sb;
    struct buffer_head *bh;
    char *data;
    u32 bidx, boff, bsize;
    u32 tmp;

    pr_debug("AFFS: read_page(%u, %ld, %d, %d)\n", (u32)inode->i_ino, page->index, from, to);
    BUG_ON(from > to || to > PAGE_CACHE_SIZE);
    kmap(page);
    data = page_address(page);
    bsize = AFFS_SB(sb)->s_data_blksize;
    tmp = (page->index << PAGE_CACHE_SHIFT) + from;
    bidx = tmp / bsize;
    boff = tmp % bsize;

    while (from < to) {
        bh = affs_bread_ino(inode, bidx, 0);
        if (IS_ERR(bh))
            return PTR_ERR(bh);
        tmp = min(bsize - boff, to - from);
        BUG_ON(from + tmp > to || tmp > bsize);
        memcpy(data + from, AFFS_DATA(bh) + boff, tmp);
        affs_brelse(bh);
        bidx++;
        from += tmp;
        boff = 0;
    }
    flush_dcache_page(page);
    kunmap(page);
    return 0;
}

static int
affs_extent_file_ofs(struct inode *inode, u32 newsize)
{
    struct super_block *sb = inode->i_sb;
    struct buffer_head *bh, *prev_bh;
    u32 bidx, boff;
    u32 size, bsize;
    u32 tmp;

    pr_debug("AFFS: extent_file(%u, %d)\n", (u32)inode->i_ino, newsize);
    bsize = AFFS_SB(sb)->s_data_blksize;
    bh = NULL;
    size = AFFS_I(inode)->mmu_private;
    bidx = size / bsize;
    boff = size % bsize;
    if (boff) {
        bh = affs_bread_ino(inode, bidx, 0);
        if (IS_ERR(bh))
            return PTR_ERR(bh);
        tmp = min(bsize - boff, newsize - size);
        BUG_ON(boff + tmp > bsize || tmp > bsize);
        memset(AFFS_DATA(bh) + boff, 0, tmp);
        be32_add_cpu(&AFFS_DATA_HEAD(bh)->size, tmp);
        affs_fix_checksum(sb, bh);
        mark_buffer_dirty_inode(bh, inode);
        size += tmp;
        bidx++;
    } else if (bidx) {
        bh = affs_bread_ino(inode, bidx - 1, 0);
        if (IS_ERR(bh))
            return PTR_ERR(bh);
    }

    while (size < newsize) {
        prev_bh = bh;
        bh = affs_getzeroblk_ino(inode, bidx);
        if (IS_ERR(bh))
            goto out;
        tmp = min(bsize, newsize - size);
        BUG_ON(tmp > bsize);
        AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
        AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
        AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
        AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
        affs_fix_checksum(sb, bh);
        bh->b_state &= ~(1UL << BH_New);
        mark_buffer_dirty_inode(bh, inode);
        if (prev_bh) {
            u32 tmp = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
            if (tmp)
                affs_warning(sb, "extent_file_ofs", "next block already set for %d (%d)", bidx, tmp);
            AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
            affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp);
            mark_buffer_dirty_inode(prev_bh, inode);
            affs_brelse(prev_bh);
        }
        size += bsize;
        bidx++;
    }
    affs_brelse(bh);
    inode->i_size = AFFS_I(inode)->mmu_private = newsize;
    return 0;

out:
    inode->i_size = AFFS_I(inode)->mmu_private = newsize;
    return PTR_ERR(bh);
}

static int
affs_readpage_ofs(struct file *file, struct page *page)
{
    struct inode *inode = page->mapping->host;
    u32 to;
    int err;

    pr_debug("AFFS: read_page(%u, %ld)\n", (u32)inode->i_ino, page->index);
    to = PAGE_CACHE_SIZE;
    if (((page->index + 1) << PAGE_CACHE_SHIFT) > inode->i_size) {
        to = inode->i_size & ~PAGE_CACHE_MASK;
        memset(page_address(page) + to, 0, PAGE_CACHE_SIZE - to);
    }

    err = affs_do_readpage_ofs(file, page, 0, to);
    if (!err)
        SetPageUptodate(page);
    unlock_page(page);
    return err;
}

static int affs_write_begin_ofs(struct file *file, struct address_space *mapping,
                loff_t pos, unsigned len, unsigned flags,
                struct page **pagep, void **fsdata)
{
    struct inode *inode = mapping->host;
    struct page *page;
    pgoff_t index;
    int err = 0;

    pr_debug("AFFS: write_begin(%u, %llu, %llu)\n", (u32)inode->i_ino, (unsigned long long)pos, (unsigned long long)pos + len);
    if (pos > AFFS_I(inode)->mmu_private) {
        /* XXX: this probably leaves a too-big i_size in case of
         * failure. Should really be updating i_size at write_end time
         */
        err = affs_extent_file_ofs(inode, pos);
        if (err)
            return err;
    }

    index = pos >> PAGE_CACHE_SHIFT;
    page = grab_cache_page_write_begin(mapping, index, flags);
    if (!page)
        return -ENOMEM;
    *pagep = page;

    if (PageUptodate(page))
        return 0;

    /* XXX: inefficient but safe in the face of short writes */
    err = affs_do_readpage_ofs(file, page, 0, PAGE_CACHE_SIZE);
    if (err) {
        unlock_page(page);
        page_cache_release(page);
    }
    return err;
}

static int affs_write_end_ofs(struct file *file, struct address_space *mapping,
                loff_t pos, unsigned len, unsigned copied,
                struct page *page, void *fsdata)
{
    struct inode *inode = mapping->host;
    struct super_block *sb = inode->i_sb;
    struct buffer_head *bh, *prev_bh;
    char *data;
    u32 bidx, boff, bsize;
    unsigned from, to;
    u32 tmp;
    int written;

    from = pos & (PAGE_CACHE_SIZE - 1);
    to = pos + len;
    /*
     * XXX: not sure if this can handle short copies (len < copied), but
     * we don't have to, because the page should always be uptodate here,
     * due to write_begin.
     */

    pr_debug("AFFS: write_begin(%u, %llu, %llu)\n", (u32)inode->i_ino, (unsigned long long)pos, (unsigned long long)pos + len);
    bsize = AFFS_SB(sb)->s_data_blksize;
    data = page_address(page);

    bh = NULL;
    written = 0;
    tmp = (page->index << PAGE_CACHE_SHIFT) + from;
    bidx = tmp / bsize;
    boff = tmp % bsize;
    if (boff) {
        bh = affs_bread_ino(inode, bidx, 0);
        if (IS_ERR(bh))
            return PTR_ERR(bh);
        tmp = min(bsize - boff, to - from);
        BUG_ON(boff + tmp > bsize || tmp > bsize);
        memcpy(AFFS_DATA(bh) + boff, data + from, tmp);
        be32_add_cpu(&AFFS_DATA_HEAD(bh)->size, tmp);
        affs_fix_checksum(sb, bh);
        mark_buffer_dirty_inode(bh, inode);
        written += tmp;
        from += tmp;
        bidx++;
    } else if (bidx) {
        bh = affs_bread_ino(inode, bidx - 1, 0);
        if (IS_ERR(bh))
            return PTR_ERR(bh);
    }
    while (from + bsize <= to) {
        prev_bh = bh;
        bh = affs_getemptyblk_ino(inode, bidx);
        if (IS_ERR(bh))
            goto out;
        memcpy(AFFS_DATA(bh), data + from, bsize);
        if (buffer_new(bh)) {
            AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
            AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
            AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
            AFFS_DATA_HEAD(bh)->size = cpu_to_be32(bsize);
            AFFS_DATA_HEAD(bh)->next = 0;
            bh->b_state &= ~(1UL << BH_New);
            if (prev_bh) {
                u32 tmp = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
                if (tmp)
                    affs_warning(sb, "commit_write_ofs", "next block already set for %d (%d)", bidx, tmp);
                AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
                affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp);
                mark_buffer_dirty_inode(prev_bh, inode);
            }
        }
        affs_brelse(prev_bh);
        affs_fix_checksum(sb, bh);
        mark_buffer_dirty_inode(bh, inode);
        written += bsize;
        from += bsize;
        bidx++;
    }
    if (from < to) {
        prev_bh = bh;
        bh = affs_bread_ino(inode, bidx, 1);
        if (IS_ERR(bh))
            goto out;
        tmp = min(bsize, to - from);
        BUG_ON(tmp > bsize);
        memcpy(AFFS_DATA(bh), data + from, tmp);
        if (buffer_new(bh)) {
            AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
            AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
            AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
            AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
            AFFS_DATA_HEAD(bh)->next = 0;
            bh->b_state &= ~(1UL << BH_New);
            if (prev_bh) {
                u32 tmp = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
                if (tmp)
                    affs_warning(sb, "commit_write_ofs", "next block already set for %d (%d)", bidx, tmp);
                AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
                affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp);
                mark_buffer_dirty_inode(prev_bh, inode);
            }
        } else if (be32_to_cpu(AFFS_DATA_HEAD(bh)->size) < tmp)
            AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
        affs_brelse(prev_bh);
        affs_fix_checksum(sb, bh);
        mark_buffer_dirty_inode(bh, inode);
        written += tmp;
        from += tmp;
        bidx++;
    }
    SetPageUptodate(page);

done:
    affs_brelse(bh);
    tmp = (page->index << PAGE_CACHE_SHIFT) + from;
    if (tmp > inode->i_size)
        inode->i_size = AFFS_I(inode)->mmu_private = tmp;

    unlock_page(page);
    page_cache_release(page);

    return written;

out:
    bh = prev_bh;
    if (!written)
        written = PTR_ERR(bh);
    goto done;
}

const struct address_space_operations affs_aops_ofs = {
    .readpage = affs_readpage_ofs,
    //.writepage = affs_writepage_ofs,
    .write_begin = affs_write_begin_ofs,
    .write_end = affs_write_end_ofs
};

/* Free any preallocated blocks. */

void
affs_free_prealloc(struct inode *inode)
{
    struct super_block *sb = inode->i_sb;

    pr_debug("AFFS: free_prealloc(ino=%lu)\n", inode->i_ino);

    while (AFFS_I(inode)->i_pa_cnt) {
        AFFS_I(inode)->i_pa_cnt--;
        affs_free_block(sb, ++AFFS_I(inode)->i_lastalloc);
    }
}

/* Truncate (or enlarge) a file to the requested size. */

void
affs_truncate(struct inode *inode)
{
    struct super_block *sb = inode->i_sb;
    u32 ext, ext_key;
    u32 last_blk, blkcnt, blk;
    u32 size;
    struct buffer_head *ext_bh;
    int i;

    pr_debug("AFFS: truncate(inode=%d, oldsize=%u, newsize=%u)\n",
         (u32)inode->i_ino, (u32)AFFS_I(inode)->mmu_private, (u32)inode->i_size);

    last_blk = 0;
    ext = 0;
    if (inode->i_size) {
        last_blk = ((u32)inode->i_size - 1) / AFFS_SB(sb)->s_data_blksize;
        ext = last_blk / AFFS_SB(sb)->s_hashsize;
    }

    if (inode->i_size > AFFS_I(inode)->mmu_private) {
        struct address_space *mapping = inode->i_mapping;
        struct page *page;
        void *fsdata;
        u32 size = inode->i_size;
        int res;

        res = mapping->a_ops->write_begin(NULL, mapping, size, 0, 0, &page, &fsdata);
        if (!res)
            res = mapping->a_ops->write_end(NULL, mapping, size, 0, 0, page, fsdata);
        else
            inode->i_size = AFFS_I(inode)->mmu_private;
        mark_inode_dirty(inode);
        return;
    } else if (inode->i_size == AFFS_I(inode)->mmu_private)
        return;

    // lock cache
    ext_bh = affs_get_extblock(inode, ext);
    if (IS_ERR(ext_bh)) {
        affs_warning(sb, "truncate", "unexpected read error for ext block %u (%d)",
                 ext, PTR_ERR(ext_bh));
        return;
    }
    if (AFFS_I(inode)->i_lc) {
        /* clear linear cache */
        i = (ext + 1) >> AFFS_I(inode)->i_lc_shift;
        if (AFFS_I(inode)->i_lc_size > i) {
            AFFS_I(inode)->i_lc_size = i;
            for (; i < AFFS_LC_SIZE; i++)
                AFFS_I(inode)->i_lc[i] = 0;
        }
        /* clear associative cache */
        for (i = 0; i < AFFS_AC_SIZE; i++)
            if (AFFS_I(inode)->i_ac[i].ext >= ext)
                AFFS_I(inode)->i_ac[i].ext = 0;
    }
    ext_key = be32_to_cpu(AFFS_TAIL(sb, ext_bh)->extension);

    blkcnt = AFFS_I(inode)->i_blkcnt;
    i = 0;
    blk = last_blk;
    if (inode->i_size) {
        i = last_blk % AFFS_SB(sb)->s_hashsize + 1;
        blk++;
    } else
        AFFS_HEAD(ext_bh)->first_data = 0;
    AFFS_HEAD(ext_bh)->block_count = cpu_to_be32(i);
    size = AFFS_SB(sb)->s_hashsize;
    if (size > blkcnt - blk + i)
        size = blkcnt - blk + i;
    for (; i < size; i++, blk++) {
        affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
        AFFS_BLOCK(sb, ext_bh, i) = 0;
    }
    AFFS_TAIL(sb, ext_bh)->extension = 0;
    affs_fix_checksum(sb, ext_bh);
    mark_buffer_dirty_inode(ext_bh, inode);
    affs_brelse(ext_bh);

    if (inode->i_size) {
        AFFS_I(inode)->i_blkcnt = last_blk + 1;
        AFFS_I(inode)->i_extcnt = ext + 1;
        if (AFFS_SB(sb)->s_flags & SF_OFS) {
            struct buffer_head *bh = affs_bread_ino(inode, last_blk, 0);
            u32 tmp;
            if (IS_ERR(bh)) {
                affs_warning(sb, "truncate", "unexpected read error for last block %u (%d)",
                         ext, PTR_ERR(bh));
                return;
            }
            tmp = be32_to_cpu(AFFS_DATA_HEAD(bh)->next);
            AFFS_DATA_HEAD(bh)->next = 0;
            affs_adjust_checksum(bh, -tmp);
            affs_brelse(bh);
        }
    } else {
        AFFS_I(inode)->i_blkcnt = 0;
        AFFS_I(inode)->i_extcnt = 1;
    }
    AFFS_I(inode)->mmu_private = inode->i_size;
    // unlock cache

    while (ext_key) {
        ext_bh = affs_bread(sb, ext_key);
        size = AFFS_SB(sb)->s_hashsize;
        if (size > blkcnt - blk)
            size = blkcnt - blk;
        for (i = 0; i < size; i++, blk++)
            affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
        affs_free_block(sb, ext_key);
        ext_key = be32_to_cpu(AFFS_TAIL(sb, ext_bh)->extension);
        affs_brelse(ext_bh);
    }
    affs_free_prealloc(inode);
}

int affs_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
{
    struct inode *inode = filp->f_mapping->host;
    int ret, err;

    err = filemap_write_and_wait_range(inode->i_mapping, start, end);
    if (err)
        return err;

    mutex_lock(&inode->i_mutex);
    ret = write_inode_now(inode, 0);
    err = sync_blockdev(inode->i_sb->s_bdev);
    if (!ret)
        ret = err;
    mutex_unlock(&inode->i_mutex);
    return ret;
}