file.c

Go to the documentation of this file.

/*
 *  fs/bfs/file.c
 *  BFS file operations.
 *  Copyright (C) 1999,2000 Tigran Aivazian <[email protected]>
 *
 *  Make the file block allocation algorithm understand the size
 *  of the underlying block device.
 *  Copyright (C) 2007 Dmitri Vorobiev <[email protected]>
 *
 */

#include <linux/fs.h>
#include <linux/buffer_head.h>
#include "bfs.h"

#undef DEBUG

#ifdef DEBUG
#define dprintf(x...)   printf(x)
#else
#define dprintf(x...)
#endif

const struct file_operations bfs_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,
    .splice_read    = generic_file_splice_read,
};

static int bfs_move_block(unsigned long from, unsigned long to,
                    struct super_block *sb)
{
    struct buffer_head *bh, *new;

    bh = sb_bread(sb, from);
    if (!bh)
        return -EIO;
    new = sb_getblk(sb, to);
    memcpy(new->b_data, bh->b_data, bh->b_size);
    mark_buffer_dirty(new);
    bforget(bh);
    brelse(new);
    return 0;
}

static int bfs_move_blocks(struct super_block *sb, unsigned long start,
                unsigned long end, unsigned long where)
{
    unsigned long i;

    dprintf("%08lx-%08lx->%08lx\n", start, end, where);
    for (i = start; i <= end; i++)
        if(bfs_move_block(i, where + i, sb)) {
            dprintf("failed to move block %08lx -> %08lx\n", i,
                                where + i);
            return -EIO;
        }
    return 0;
}

static int bfs_get_block(struct inode *inode, sector_t block,
            struct buffer_head *bh_result, int create)
{
    unsigned long phys;
    int err;
    struct super_block *sb = inode->i_sb;
    struct bfs_sb_info *info = BFS_SB(sb);
    struct bfs_inode_info *bi = BFS_I(inode);

    phys = bi->i_sblock + block;
    if (!create) {
        if (phys <= bi->i_eblock) {
            dprintf("c=%d, b=%08lx, phys=%09lx (granted)\n",
                                create, (unsigned long)block, phys);
            map_bh(bh_result, sb, phys);
        }
        return 0;
    }

    /*
     * If the file is not empty and the requested block is within the
     * range of blocks allocated for this file, we can grant it.
     */
    if (bi->i_sblock && (phys <= bi->i_eblock)) {
        dprintf("c=%d, b=%08lx, phys=%08lx (interim block granted)\n", 
                create, (unsigned long)block, phys);
        map_bh(bh_result, sb, phys);
        return 0;
    }

    /* The file will be extended, so let's see if there is enough space. */
    if (phys >= info->si_blocks)
        return -ENOSPC;

    /* The rest has to be protected against itself. */
    mutex_lock(&info->bfs_lock);

    /*
     * If the last data block for this file is the last allocated
     * block, we can extend the file trivially, without moving it
     * anywhere.
     */
    if (bi->i_eblock == info->si_lf_eblk) {
        dprintf("c=%d, b=%08lx, phys=%08lx (simple extension)\n", 
                create, (unsigned long)block, phys);
        map_bh(bh_result, sb, phys);
        info->si_freeb -= phys - bi->i_eblock;
        info->si_lf_eblk = bi->i_eblock = phys;
        mark_inode_dirty(inode);
        err = 0;
        goto out;
    }

    /* Ok, we have to move this entire file to the next free block. */
    phys = info->si_lf_eblk + 1;
    if (phys + block >= info->si_blocks) {
        err = -ENOSPC;
        goto out;
    }

    if (bi->i_sblock) {
        err = bfs_move_blocks(inode->i_sb, bi->i_sblock, 
                        bi->i_eblock, phys);
        if (err) {
            dprintf("failed to move ino=%08lx -> fs corruption\n",
                                inode->i_ino);
            goto out;
        }
    } else
        err = 0;

    dprintf("c=%d, b=%08lx, phys=%08lx (moved)\n",
                create, (unsigned long)block, phys);
    bi->i_sblock = phys;
    phys += block;
    info->si_lf_eblk = bi->i_eblock = phys;

    /*
     * This assumes nothing can write the inode back while we are here
     * and thus update inode->i_blocks! (XXX)
     */
    info->si_freeb -= bi->i_eblock - bi->i_sblock + 1 - inode->i_blocks;
    mark_inode_dirty(inode);
    map_bh(bh_result, sb, phys);
out:
    mutex_unlock(&info->bfs_lock);
    return err;
}

static int bfs_writepage(struct page *page, struct writeback_control *wbc)
{
    return block_write_full_page(page, bfs_get_block, wbc);
}

static int bfs_readpage(struct file *file, struct page *page)
{
    return block_read_full_page(page, bfs_get_block);
}

static int bfs_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,
                bfs_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 bfs_bmap(struct address_space *mapping, sector_t block)
{
    return generic_block_bmap(mapping, block, bfs_get_block);
}

const struct address_space_operations bfs_aops = {
    .readpage   = bfs_readpage,
    .writepage  = bfs_writepage,
    .write_begin    = bfs_write_begin,
    .write_end  = generic_write_end,
    .bmap       = bfs_bmap,
};

const struct inode_operations bfs_file_inops;