kernel/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_iter      = generic_file_read_iter,
  27         .write_iter     = generic_file_write_iter,
  28         .mmap           = generic_file_mmap,
  29         .splice_read    = generic_file_splice_read,
  30 };
  31
  32 static int bfs_move_block(unsigned long from, unsigned long to,
  33                                         struct super_block *sb)
  34 {
  35         struct buffer_head *bh, *new;
  36
  37         bh = sb_bread(sb, from);
  38         if (!bh)
  39                 return -EIO;
  40         new = sb_getblk(sb, to);
  41         memcpy(new->b_data, bh->b_data, bh->b_size);
  42         mark_buffer_dirty(new);
  43         bforget(bh);
  44         brelse(new);
  45         return 0;
  46 }
  47
  48 static int bfs_move_blocks(struct super_block *sb, unsigned long start,
  49                                 unsigned long end, unsigned long where)
  50 {
  51         unsigned long i;
  52
  53         dprintf("%08lx-%08lx->%08lx\n", start, end, where);
  54         for (i = start; i <= end; i++)
  55                 if(bfs_move_block(i, where + i, sb)) {
  56                         dprintf("failed to move block %08lx -> %08lx\n", i,
  57                                                                 where + i);
  58                         return -EIO;
  59                 }
  60         return 0;
  61 }
  62
  63 static int bfs_get_block(struct inode *inode, sector_t block,
  64                         struct buffer_head *bh_result, int create)
  65 {
  66         unsigned long phys;
  67         int err;
  68         struct super_block *sb = inode->i_sb;
  69         struct bfs_sb_info *info = BFS_SB(sb);
  70         struct bfs_inode_info *bi = BFS_I(inode);
  71
  72         phys = bi->i_sblock + block;
  73         if (!create) {
  74                 if (phys <= bi->i_eblock) {
  75                         dprintf("c=%d, b=%08lx, phys=%09lx (granted)\n",
  76                                 create, (unsigned long)block, phys);
  77                         map_bh(bh_result, sb, phys);
  78                 }
  79                 return 0;
  80         }
  81
  82         /*
  83          * If the file is not empty and the requested block is within the
  84          * range of blocks allocated for this file, we can grant it.
  85          */
  86         if (bi->i_sblock && (phys <= bi->i_eblock)) {
  87                 dprintf("c=%d, b=%08lx, phys=%08lx (interim block granted)\n",
  88                                 create, (unsigned long)block, phys);
  89                 map_bh(bh_result, sb, phys);
  90                 return 0;
  91         }
  92
  93         /* The file will be extended, so let's see if there is enough space. */
  94         if (phys >= info->si_blocks)
  95                 return -ENOSPC;
  96
  97         /* The rest has to be protected against itself. */
  98         mutex_lock(&info->bfs_lock);
  99
 100         /*
 101          * If the last data block for this file is the last allocated
 102          * block, we can extend the file trivially, without moving it
 103          * anywhere.
 104          */
 105         if (bi->i_eblock == info->si_lf_eblk) {
 106                 dprintf("c=%d, b=%08lx, phys=%08lx (simple extension)\n",
 107                                 create, (unsigned long)block, phys);
 108                 map_bh(bh_result, sb, phys);
 109                 info->si_freeb -= phys - bi->i_eblock;
 110                 info->si_lf_eblk = bi->i_eblock = phys;
 111                 mark_inode_dirty(inode);
 112                 err = 0;
 113                 goto out;
 114         }
 115
 116         /* Ok, we have to move this entire file to the next free block. */
 117         phys = info->si_lf_eblk + 1;
 118         if (phys + block >= info->si_blocks) {
 119                 err = -ENOSPC;
 120                 goto out;
 121         }
 122
 123         if (bi->i_sblock) {
 124                 err = bfs_move_blocks(inode->i_sb, bi->i_sblock,
 125                                                 bi->i_eblock, phys);
 126                 if (err) {
 127                         dprintf("failed to move ino=%08lx -> fs corruption\n",
 128                                                                 inode->i_ino);
 129                         goto out;
 130                 }
 131         } else
 132                 err = 0;
 133
 134         dprintf("c=%d, b=%08lx, phys=%08lx (moved)\n",
 135                 create, (unsigned long)block, phys);
 136         bi->i_sblock = phys;
 137         phys += block;
 138         info->si_lf_eblk = bi->i_eblock = phys;
 139
 140         /*
 141          * This assumes nothing can write the inode back while we are here
 142          * and thus update inode->i_blocks! (XXX)
 143          */
 144         info->si_freeb -= bi->i_eblock - bi->i_sblock + 1 - inode->i_blocks;
 145         mark_inode_dirty(inode);
 146         map_bh(bh_result, sb, phys);
 147 out:
 148         mutex_unlock(&info->bfs_lock);
 149         return err;
 150 }
 151
 152 static int bfs_writepage(struct page *page, struct writeback_control *wbc)
 153 {
 154         return block_write_full_page(page, bfs_get_block, wbc);
 155 }
 156
 157 static int bfs_readpage(struct file *file, struct page *page)
 158 {
 159         return block_read_full_page(page, bfs_get_block);
 160 }
 161
 162 static void bfs_write_failed(struct address_space *mapping, loff_t to)
 163 {
 164         struct inode *inode = mapping->host;
 165
 166         if (to > inode->i_size)
 167                 truncate_pagecache(inode, inode->i_size);
 168 }
 169
 170 static int bfs_write_begin(struct file *file, struct address_space *mapping,
 171                         loff_t pos, unsigned len, unsigned flags,
 172                         struct page **pagep, void **fsdata)
 173 {
 174         int ret;
 175
 176         ret = block_write_begin(mapping, pos, len, flags, pagep,
 177                                 bfs_get_block);
 178         if (unlikely(ret))
 179                 bfs_write_failed(mapping, pos + len);
 180
 181         return ret;
 182 }
 183
 184 static sector_t bfs_bmap(struct address_space *mapping, sector_t block)
 185 {
 186         return generic_block_bmap(mapping, block, bfs_get_block);
 187 }
 188
 189 const struct address_space_operations bfs_aops = {
 190         .readpage       = bfs_readpage,
 191         .writepage      = bfs_writepage,
 192         .write_begin    = bfs_write_begin,
 193         .write_end      = generic_write_end,
 194         .bmap           = bfs_bmap,
 195 };
 196
 197 const struct inode_operations bfs_file_inops;