linux/fs/bfs/file.c
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   1/*
   2 *      fs/bfs/file.c
   3 *      BFS file operations.
   4 *      Copyright (C) 1999,2000 Tigran Aivazian <tigran@veritas.com>
   5 *
   6 *      Make the file block allocation algorithm understand the size
   7 *      of the underlying block device.
   8 *      Copyright (C) 2007 Dmitri Vorobiev <dmitri.vorobiev@gmail.com>
   9 *
  10 */
  11
  12#include <linux/fs.h>
  13#include <linux/buffer_head.h>
  14#include "bfs.h"
  15
  16#undef DEBUG
  17
  18#ifdef DEBUG
  19#define dprintf(x...)   printf(x)
  20#else
  21#define dprintf(x...)
  22#endif
  23
  24const struct file_operations bfs_file_operations = {
  25        .llseek         = generic_file_llseek,
  26        .read           = do_sync_read,
  27        .aio_read       = generic_file_aio_read,
  28        .write          = do_sync_write,
  29        .aio_write      = generic_file_aio_write,
  30        .mmap           = generic_file_mmap,
  31        .splice_read    = generic_file_splice_read,
  32};
  33
  34static int bfs_move_block(unsigned long from, unsigned long to,
  35                                        struct super_block *sb)
  36{
  37        struct buffer_head *bh, *new;
  38
  39        bh = sb_bread(sb, from);
  40        if (!bh)
  41                return -EIO;
  42        new = sb_getblk(sb, to);
  43        memcpy(new->b_data, bh->b_data, bh->b_size);
  44        mark_buffer_dirty(new);
  45        bforget(bh);
  46        brelse(new);
  47        return 0;
  48}
  49
  50static int bfs_move_blocks(struct super_block *sb, unsigned long start,
  51                                unsigned long end, unsigned long where)
  52{
  53        unsigned long i;
  54
  55        dprintf("%08lx-%08lx->%08lx\n", start, end, where);
  56        for (i = start; i <= end; i++)
  57                if(bfs_move_block(i, where + i, sb)) {
  58                        dprintf("failed to move block %08lx -> %08lx\n", i,
  59                                                                where + i);
  60                        return -EIO;
  61                }
  62        return 0;
  63}
  64
  65static int bfs_get_block(struct inode *inode, sector_t block,
  66                        struct buffer_head *bh_result, int create)
  67{
  68        unsigned long phys;
  69        int err;
  70        struct super_block *sb = inode->i_sb;
  71        struct bfs_sb_info *info = BFS_SB(sb);
  72        struct bfs_inode_info *bi = BFS_I(inode);
  73
  74        phys = bi->i_sblock + block;
  75        if (!create) {
  76                if (phys <= bi->i_eblock) {
  77                        dprintf("c=%d, b=%08lx, phys=%09lx (granted)\n",
  78                                create, (unsigned long)block, phys);
  79                        map_bh(bh_result, sb, phys);
  80                }
  81                return 0;
  82        }
  83
  84        /*
  85         * If the file is not empty and the requested block is within the
  86         * range of blocks allocated for this file, we can grant it.
  87         */
  88        if (bi->i_sblock && (phys <= bi->i_eblock)) {
  89                dprintf("c=%d, b=%08lx, phys=%08lx (interim block granted)\n", 
  90                                create, (unsigned long)block, phys);
  91                map_bh(bh_result, sb, phys);
  92                return 0;
  93        }
  94
  95        /* The file will be extended, so let's see if there is enough space. */
  96        if (phys >= info->si_blocks)
  97                return -ENOSPC;
  98
  99        /* The rest has to be protected against itself. */
 100        mutex_lock(&info->bfs_lock);
 101
 102        /*
 103         * If the last data block for this file is the last allocated
 104         * block, we can extend the file trivially, without moving it
 105         * anywhere.
 106         */
 107        if (bi->i_eblock == info->si_lf_eblk) {
 108                dprintf("c=%d, b=%08lx, phys=%08lx (simple extension)\n", 
 109                                create, (unsigned long)block, phys);
 110                map_bh(bh_result, sb, phys);
 111                info->si_freeb -= phys - bi->i_eblock;
 112                info->si_lf_eblk = bi->i_eblock = phys;
 113                mark_inode_dirty(inode);
 114                err = 0;
 115                goto out;
 116        }
 117
 118        /* Ok, we have to move this entire file to the next free block. */
 119        phys = info->si_lf_eblk + 1;
 120        if (phys + block >= info->si_blocks) {
 121                err = -ENOSPC;
 122                goto out;
 123        }
 124
 125        if (bi->i_sblock) {
 126                err = bfs_move_blocks(inode->i_sb, bi->i_sblock, 
 127                                                bi->i_eblock, phys);
 128                if (err) {
 129                        dprintf("failed to move ino=%08lx -> fs corruption\n",
 130                                                                inode->i_ino);
 131                        goto out;
 132                }
 133        } else
 134                err = 0;
 135
 136        dprintf("c=%d, b=%08lx, phys=%08lx (moved)\n",
 137                create, (unsigned long)block, phys);
 138        bi->i_sblock = phys;
 139        phys += block;
 140        info->si_lf_eblk = bi->i_eblock = phys;
 141
 142        /*
 143         * This assumes nothing can write the inode back while we are here
 144         * and thus update inode->i_blocks! (XXX)
 145         */
 146        info->si_freeb -= bi->i_eblock - bi->i_sblock + 1 - inode->i_blocks;
 147        mark_inode_dirty(inode);
 148        map_bh(bh_result, sb, phys);
 149out:
 150        mutex_unlock(&info->bfs_lock);
 151        return err;
 152}
 153
 154static int bfs_writepage(struct page *page, struct writeback_control *wbc)
 155{
 156        return block_write_full_page(page, bfs_get_block, wbc);
 157}
 158
 159static int bfs_readpage(struct file *file, struct page *page)
 160{
 161        return block_read_full_page(page, bfs_get_block);
 162}
 163
 164static int bfs_write_begin(struct file *file, struct address_space *mapping,
 165                        loff_t pos, unsigned len, unsigned flags,
 166                        struct page **pagep, void **fsdata)
 167{
 168        int ret;
 169
 170        ret = block_write_begin(mapping, pos, len, flags, pagep,
 171                                bfs_get_block);
 172        if (unlikely(ret)) {
 173                loff_t isize = mapping->host->i_size;
 174                if (pos + len > isize)
 175                        vmtruncate(mapping->host, isize);
 176        }
 177
 178        return ret;
 179}
 180
 181static sector_t bfs_bmap(struct address_space *mapping, sector_t block)
 182{
 183        return generic_block_bmap(mapping, block, bfs_get_block);
 184}
 185
 186const struct address_space_operations bfs_aops = {
 187        .readpage       = bfs_readpage,
 188        .writepage      = bfs_writepage,
 189        .write_begin    = bfs_write_begin,
 190        .write_end      = generic_write_end,
 191        .bmap           = bfs_bmap,
 192};
 193
 194const struct inode_operations bfs_file_inops;
 195
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