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Linux/fs/bfs/file.c

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  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;
199 

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