root/fs/bfs/file.c

DEFINITIONS

1. bfs_move_block
2. bfs_move_blocks
3. bfs_get_block
4. bfs_writepage
5. bfs_readpage
6. bfs_write_failed
7. bfs_write_begin
8. bfs_bmap

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      fs/bfs/file.c
   4  *      BFS file operations.
   5  *      Copyright (C) 1999-2018 Tigran Aivazian <aivazian.tigran@gmail.com>
   6  *
   7  *      Make the file block allocation algorithm understand the size
   8  *      of the underlying block device.
   9  *      Copyright (C) 2007 Dmitri Vorobiev <dmitri.vorobiev@gmail.com>
  10  *
  11  */
  12 
  13 #include <linux/fs.h>
  14 #include <linux/buffer_head.h>
  15 #include "bfs.h"
  16 
  17 #undef DEBUG
  18 
  19 #ifdef DEBUG
  20 #define dprintf(x...)   printf(x)
  21 #else
  22 #define dprintf(x...)
  23 #endif
  24 
  25 const struct file_operations bfs_file_operations = {
  26         .llseek         = generic_file_llseek,
  27         .read_iter      = generic_file_read_iter,
  28         .write_iter     = generic_file_write_iter,
  29         .mmap           = generic_file_mmap,
  30         .splice_read    = generic_file_splice_read,
  31 };
  32 
  33 static int bfs_move_block(unsigned long from, unsigned long to,
  34                                         struct super_block *sb)
  35 {
  36         struct buffer_head *bh, *new;
  37 
  38         bh = sb_bread(sb, from);
  39         if (!bh)
  40                 return -EIO;
  41         new = sb_getblk(sb, to);
  42         memcpy(new->b_data, bh->b_data, bh->b_size);
  43         mark_buffer_dirty(new);
  44         bforget(bh);
  45         brelse(new);
  46         return 0;
  47 }
  48 
  49 static int bfs_move_blocks(struct super_block *sb, unsigned long start,
  50                                 unsigned long end, unsigned long where)
  51 {
  52         unsigned long i;
  53 
  54         dprintf("%08lx-%08lx->%08lx\n", start, end, where);
  55         for (i = start; i <= end; i++)
  56                 if(bfs_move_block(i, where + i, sb)) {
  57                         dprintf("failed to move block %08lx -> %08lx\n", i,
  58                                                                 where + i);
  59                         return -EIO;
  60                 }
  61         return 0;
  62 }
  63 
  64 static int bfs_get_block(struct inode *inode, sector_t block,
  65                         struct buffer_head *bh_result, int create)
  66 {
  67         unsigned long phys;
  68         int err;
  69         struct super_block *sb = inode->i_sb;
  70         struct bfs_sb_info *info = BFS_SB(sb);
  71         struct bfs_inode_info *bi = BFS_I(inode);
  72 
  73         phys = bi->i_sblock + block;
  74         if (!create) {
  75                 if (phys <= bi->i_eblock) {
  76                         dprintf("c=%d, b=%08lx, phys=%09lx (granted)\n",
  77                                 create, (unsigned long)block, phys);
  78                         map_bh(bh_result, sb, phys);
  79                 }
  80                 return 0;
  81         }
  82 
  83         /*
  84          * If the file is not empty and the requested block is within the
  85          * range of blocks allocated for this file, we can grant it.
  86          */
  87         if (bi->i_sblock && (phys <= bi->i_eblock)) {
  88                 dprintf("c=%d, b=%08lx, phys=%08lx (interim block granted)\n", 
  89                                 create, (unsigned long)block, phys);
  90                 map_bh(bh_result, sb, phys);
  91                 return 0;
  92         }
  93 
  94         /* The file will be extended, so let's see if there is enough space. */
  95         if (phys >= info->si_blocks)
  96                 return -ENOSPC;
  97 
  98         /* The rest has to be protected against itself. */
  99         mutex_lock(&info->bfs_lock);
 100 
 101         /*
 102          * If the last data block for this file is the last allocated
 103          * block, we can extend the file trivially, without moving it
 104          * anywhere.
 105          */
 106         if (bi->i_eblock == info->si_lf_eblk) {
 107                 dprintf("c=%d, b=%08lx, phys=%08lx (simple extension)\n", 
 108                                 create, (unsigned long)block, phys);
 109                 map_bh(bh_result, sb, phys);
 110                 info->si_freeb -= phys - bi->i_eblock;
 111                 info->si_lf_eblk = bi->i_eblock = phys;
 112                 mark_inode_dirty(inode);
 113                 err = 0;
 114                 goto out;
 115         }
 116 
 117         /* Ok, we have to move this entire file to the next free block. */
 118         phys = info->si_lf_eblk + 1;
 119         if (phys + block >= info->si_blocks) {
 120                 err = -ENOSPC;
 121                 goto out;
 122         }
 123 
 124         if (bi->i_sblock) {
 125                 err = bfs_move_blocks(inode->i_sb, bi->i_sblock, 
 126                                                 bi->i_eblock, phys);
 127                 if (err) {
 128                         dprintf("failed to move ino=%08lx -> fs corruption\n",
 129                                                                 inode->i_ino);
 130                         goto out;
 131                 }
 132         } else
 133                 err = 0;
 134 
 135         dprintf("c=%d, b=%08lx, phys=%08lx (moved)\n",
 136                 create, (unsigned long)block, phys);
 137         bi->i_sblock = phys;
 138         phys += block;
 139         info->si_lf_eblk = bi->i_eblock = phys;
 140 
 141         /*
 142          * This assumes nothing can write the inode back while we are here
 143          * and thus update inode->i_blocks! (XXX)
 144          */
 145         info->si_freeb -= bi->i_eblock - bi->i_sblock + 1 - inode->i_blocks;
 146         mark_inode_dirty(inode);
 147         map_bh(bh_result, sb, phys);
 148 out:
 149         mutex_unlock(&info->bfs_lock);
 150         return err;
 151 }
 152 
 153 static int bfs_writepage(struct page *page, struct writeback_control *wbc)
 154 {
 155         return block_write_full_page(page, bfs_get_block, wbc);
 156 }
 157 
 158 static int bfs_readpage(struct file *file, struct page *page)
 159 {
 160         return block_read_full_page(page, bfs_get_block);
 161 }
 162 
 163 static void bfs_write_failed(struct address_space *mapping, loff_t to)
 164 {
 165         struct inode *inode = mapping->host;
 166 
 167         if (to > inode->i_size)
 168                 truncate_pagecache(inode, inode->i_size);
 169 }
 170 
 171 static int bfs_write_begin(struct file *file, struct address_space *mapping,
 172                         loff_t pos, unsigned len, unsigned flags,
 173                         struct page **pagep, void **fsdata)
 174 {
 175         int ret;
 176 
 177         ret = block_write_begin(mapping, pos, len, flags, pagep,
 178                                 bfs_get_block);
 179         if (unlikely(ret))
 180                 bfs_write_failed(mapping, pos + len);
 181 
 182         return ret;
 183 }
 184 
 185 static sector_t bfs_bmap(struct address_space *mapping, sector_t block)
 186 {
 187         return generic_block_bmap(mapping, block, bfs_get_block);
 188 }
 189 
 190 const struct address_space_operations bfs_aops = {
 191         .readpage       = bfs_readpage,
 192         .writepage      = bfs_writepage,
 193         .write_begin    = bfs_write_begin,
 194         .write_end      = generic_write_end,
 195         .bmap           = bfs_bmap,
 196 };
 197 
 198 const struct inode_operations bfs_file_inops;