file.c

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/*
 * OMFS (as used by RIO Karma) file operations.
 * Copyright (C) 2005 Bob Copeland <[email protected]>
 * Released under GPL v2.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/mpage.h>
#include "omfs.h"

static u32 omfs_max_extents(struct omfs_sb_info *sbi, int offset)
{
    return (sbi->s_sys_blocksize - offset -
        sizeof(struct omfs_extent)) /
        sizeof(struct omfs_extent_entry) + 1;
}

void omfs_make_empty_table(struct buffer_head *bh, int offset)
{
    struct omfs_extent *oe = (struct omfs_extent *) &bh->b_data[offset];

    oe->e_next = ~cpu_to_be64(0ULL);
    oe->e_extent_count = cpu_to_be32(1),
    oe->e_fill = cpu_to_be32(0x22),
    oe->e_entry.e_cluster = ~cpu_to_be64(0ULL);
    oe->e_entry.e_blocks = ~cpu_to_be64(0ULL);
}

int omfs_shrink_inode(struct inode *inode)
{
    struct omfs_sb_info *sbi = OMFS_SB(inode->i_sb);
    struct omfs_extent *oe;
    struct omfs_extent_entry *entry;
    struct buffer_head *bh;
    u64 next, last;
    u32 extent_count;
    u32 max_extents;
    int ret;

    /* traverse extent table, freeing each entry that is greater
     * than inode->i_size;
     */
    next = inode->i_ino;

    /* only support truncate -> 0 for now */
    ret = -EIO;
    if (inode->i_size != 0)
        goto out;

    bh = omfs_bread(inode->i_sb, next);
    if (!bh)
        goto out;

    oe = (struct omfs_extent *)(&bh->b_data[OMFS_EXTENT_START]);
    max_extents = omfs_max_extents(sbi, OMFS_EXTENT_START);

    for (;;) {

        if (omfs_is_bad(sbi, (struct omfs_header *) bh->b_data, next))
            goto out_brelse;

        extent_count = be32_to_cpu(oe->e_extent_count);

        if (extent_count > max_extents)
            goto out_brelse;

        last = next;
        next = be64_to_cpu(oe->e_next);
        entry = &oe->e_entry;

        /* ignore last entry as it is the terminator */
        for (; extent_count > 1; extent_count--) {
            u64 start, count;
            start = be64_to_cpu(entry->e_cluster);
            count = be64_to_cpu(entry->e_blocks);

            omfs_clear_range(inode->i_sb, start, (int) count);
            entry++;
        }
        omfs_make_empty_table(bh, (char *) oe - bh->b_data);
        mark_buffer_dirty(bh);
        brelse(bh);

        if (last != inode->i_ino)
            omfs_clear_range(inode->i_sb, last, sbi->s_mirrors);

        if (next == ~0)
            break;

        bh = omfs_bread(inode->i_sb, next);
        if (!bh)
            goto out;
        oe = (struct omfs_extent *) (&bh->b_data[OMFS_EXTENT_CONT]);
        max_extents = omfs_max_extents(sbi, OMFS_EXTENT_CONT);
    }
    ret = 0;
out:
    return ret;
out_brelse:
    brelse(bh);
    return ret;
}

static void omfs_truncate(struct inode *inode)
{
    omfs_shrink_inode(inode);
    mark_inode_dirty(inode);
}

/*
 * Add new blocks to the current extent, or create new entries/continuations
 * as necessary.
 */
static int omfs_grow_extent(struct inode *inode, struct omfs_extent *oe,
            u64 *ret_block)
{
    struct omfs_extent_entry *terminator;
    struct omfs_extent_entry *entry = &oe->e_entry;
    struct omfs_sb_info *sbi = OMFS_SB(inode->i_sb);
    u32 extent_count = be32_to_cpu(oe->e_extent_count);
    u64 new_block = 0;
    u32 max_count;
    int new_count;
    int ret = 0;

    /* reached the end of the extent table with no blocks mapped.
     * there are three possibilities for adding: grow last extent,
     * add a new extent to the current extent table, and add a
     * continuation inode.  in last two cases need an allocator for
     * sbi->s_cluster_size
     */

    /* TODO: handle holes */

    /* should always have a terminator */
    if (extent_count < 1)
        return -EIO;

    /* trivially grow current extent, if next block is not taken */
    terminator = entry + extent_count - 1;
    if (extent_count > 1) {
        entry = terminator-1;
        new_block = be64_to_cpu(entry->e_cluster) +
            be64_to_cpu(entry->e_blocks);

        if (omfs_allocate_block(inode->i_sb, new_block)) {
            be64_add_cpu(&entry->e_blocks, 1);
            terminator->e_blocks = ~(cpu_to_be64(
                be64_to_cpu(~terminator->e_blocks) + 1));
            goto out;
        }
    }
    max_count = omfs_max_extents(sbi, OMFS_EXTENT_START);

    /* TODO: add a continuation block here */
    if (be32_to_cpu(oe->e_extent_count) > max_count-1)
        return -EIO;

    /* try to allocate a new cluster */
    ret = omfs_allocate_range(inode->i_sb, 1, sbi->s_clustersize,
        &new_block, &new_count);
    if (ret)
        goto out_fail;

    /* copy terminator down an entry */
    entry = terminator;
    terminator++;
    memcpy(terminator, entry, sizeof(struct omfs_extent_entry));

    entry->e_cluster = cpu_to_be64(new_block);
    entry->e_blocks = cpu_to_be64((u64) new_count);

    terminator->e_blocks = ~(cpu_to_be64(
        be64_to_cpu(~terminator->e_blocks) + (u64) new_count));

    /* write in new entry */
    be32_add_cpu(&oe->e_extent_count, 1);

out:
    *ret_block = new_block;
out_fail:
    return ret;
}

/*
 * Scans across the directory table for a given file block number.
 * If block not found, return 0.
 */
static sector_t find_block(struct inode *inode, struct omfs_extent_entry *ent,
            sector_t block, int count, int *left)
{
    /* count > 1 because of terminator */
    sector_t searched = 0;
    for (; count > 1; count--) {
        int numblocks = clus_to_blk(OMFS_SB(inode->i_sb),
            be64_to_cpu(ent->e_blocks));

        if (block >= searched  &&
            block < searched + numblocks) {
            /*
             * found it at cluster + (block - searched)
             * numblocks - (block - searched) is remainder
             */
            *left = numblocks - (block - searched);
            return clus_to_blk(OMFS_SB(inode->i_sb),
                be64_to_cpu(ent->e_cluster)) +
                block - searched;
        }
        searched += numblocks;
        ent++;
    }
    return 0;
}

static int omfs_get_block(struct inode *inode, sector_t block,
              struct buffer_head *bh_result, int create)
{
    struct buffer_head *bh;
    sector_t next, offset;
    int ret;
    u64 uninitialized_var(new_block);
    u32 max_extents;
    int extent_count;
    struct omfs_extent *oe;
    struct omfs_extent_entry *entry;
    struct omfs_sb_info *sbi = OMFS_SB(inode->i_sb);
    int max_blocks = bh_result->b_size >> inode->i_blkbits;
    int remain;

    ret = -EIO;
    bh = omfs_bread(inode->i_sb, inode->i_ino);
    if (!bh)
        goto out;

    oe = (struct omfs_extent *)(&bh->b_data[OMFS_EXTENT_START]);
    max_extents = omfs_max_extents(sbi, OMFS_EXTENT_START);
    next = inode->i_ino;

    for (;;) {

        if (omfs_is_bad(sbi, (struct omfs_header *) bh->b_data, next))
            goto out_brelse;

        extent_count = be32_to_cpu(oe->e_extent_count);
        next = be64_to_cpu(oe->e_next);
        entry = &oe->e_entry;

        if (extent_count > max_extents)
            goto out_brelse;

        offset = find_block(inode, entry, block, extent_count, &remain);
        if (offset > 0) {
            ret = 0;
            map_bh(bh_result, inode->i_sb, offset);
            if (remain > max_blocks)
                remain = max_blocks;
            bh_result->b_size = (remain << inode->i_blkbits);
            goto out_brelse;
        }
        if (next == ~0)
            break;

        brelse(bh);
        bh = omfs_bread(inode->i_sb, next);
        if (!bh)
            goto out;
        oe = (struct omfs_extent *) (&bh->b_data[OMFS_EXTENT_CONT]);
        max_extents = omfs_max_extents(sbi, OMFS_EXTENT_CONT);
    }
    if (create) {
        ret = omfs_grow_extent(inode, oe, &new_block);
        if (ret == 0) {
            mark_buffer_dirty(bh);
            mark_inode_dirty(inode);
            map_bh(bh_result, inode->i_sb,
                    clus_to_blk(sbi, new_block));
        }
    }
out_brelse:
    brelse(bh);
out:
    return ret;
}

static int omfs_readpage(struct file *file, struct page *page)
{
    return block_read_full_page(page, omfs_get_block);
}

static int omfs_readpages(struct file *file, struct address_space *mapping,
        struct list_head *pages, unsigned nr_pages)
{
    return mpage_readpages(mapping, pages, nr_pages, omfs_get_block);
}

static int omfs_writepage(struct page *page, struct writeback_control *wbc)
{
    return block_write_full_page(page, omfs_get_block, wbc);
}

static int
omfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
{
    return mpage_writepages(mapping, wbc, omfs_get_block);
}

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

    ret = block_write_begin(mapping, pos, len, flags, pagep,
                omfs_get_block);
    if (unlikely(ret)) {
        loff_t isize = mapping->host->i_size;
        if (pos + len > isize)
            vmtruncate(mapping->host, isize);
    }

    return ret;
}

static sector_t omfs_bmap(struct address_space *mapping, sector_t block)
{
    return generic_block_bmap(mapping, block, omfs_get_block);
}

const struct file_operations omfs_file_operations = {
    .llseek = generic_file_llseek,
    .read = do_sync_read,
    .write = do_sync_write,
    .aio_read = generic_file_aio_read,
    .aio_write = generic_file_aio_write,
    .mmap = generic_file_mmap,
    .fsync = generic_file_fsync,
    .splice_read = generic_file_splice_read,
};

static int omfs_setattr(struct dentry *dentry, struct iattr *attr)
{
    struct inode *inode = dentry->d_inode;
    int error;

    error = inode_change_ok(inode, attr);
    if (error)
        return error;

    if ((attr->ia_valid & ATTR_SIZE) &&
        attr->ia_size != i_size_read(inode)) {
        error = vmtruncate(inode, attr->ia_size);
        if (error)
            return error;
    }

    setattr_copy(inode, attr);
    mark_inode_dirty(inode);
    return 0;
}

const struct inode_operations omfs_file_inops = {
    .setattr = omfs_setattr,
    .truncate = omfs_truncate
};

const struct address_space_operations omfs_aops = {
    .readpage = omfs_readpage,
    .readpages = omfs_readpages,
    .writepage = omfs_writepage,
    .writepages = omfs_writepages,
    .write_begin = omfs_write_begin,
    .write_end = generic_write_end,
    .bmap = omfs_bmap,
};