fs/bfs/file.c

   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
  24 const 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
  34 static 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
  50 static 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
  65 static 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);
 149 out:
 150         mutex_unlock(&info->bfs_lock);
 151         return err;
 152 }
 153
 154 static int bfs_writepage(struct page *page, struct writeback_control *wbc)
 155 {
 156         return block_write_full_page(page, bfs_get_block, wbc);
 157 }
 158
 159 static int bfs_readpage(struct file *file, struct page *page)
 160 {
 161         return block_read_full_page(page, bfs_get_block);
 162 }
 163
 164 static void bfs_write_failed(struct address_space *mapping, loff_t to)
 165 {
 166         struct inode *inode = mapping->host;
 167
 168         if (to > inode->i_size)
 169                 truncate_pagecache(inode, to, inode->i_size);
 170 }
 171
 172 static int bfs_write_begin(struct file *file, struct address_space *mapping,
 173                         loff_t pos, unsigned len, unsigned flags,
 174                         struct page **pagep, void **fsdata)
 175 {
 176         int ret;
 177
 178         ret = block_write_begin(mapping, pos, len, flags, pagep,
 179                                 bfs_get_block);
 180         if (unlikely(ret))
 181                 bfs_write_failed(mapping, pos + len);
 182
 183         return ret;
 184 }
 185
 186 static sector_t bfs_bmap(struct address_space *mapping, sector_t block)
 187 {
 188         return generic_block_bmap(mapping, block, bfs_get_block);
 189 }
 190
 191 const struct address_space_operations bfs_aops = {
 192         .readpage       = bfs_readpage,
 193         .writepage      = bfs_writepage,
 194         .write_begin    = bfs_write_begin,
 195         .write_end      = generic_write_end,
 196         .bmap           = bfs_bmap,
 197 };
 198
 199 const struct inode_operations bfs_file_inops;