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/mpage.h> 15 #include <linux/buffer_head.h> 16 #include "bfs.h" 17 18 #undef DEBUG 19 20 #ifdef DEBUG 21 #define dprintf(x...) printf(x) 22 #else 23 #define dprintf(x...) 24 #endif 25 26 const struct file_operations bfs_file_operations = { 27 .llseek = generic_file_llseek, 28 .read_iter = generic_file_read_iter, 29 .write_iter = generic_file_write_iter, 30 .mmap = generic_file_mmap, 31 .splice_read = filemap_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_writepages(struct address_space *mapping, 155 struct writeback_control *wbc) 156 { 157 return mpage_writepages(mapping, wbc, bfs_get_block); 158 } 159 160 static int bfs_read_folio(struct file *file, struct folio *folio) 161 { 162 return block_read_full_folio(folio, bfs_get_block); 163 } 164 165 static void bfs_write_failed(struct address_space *mapping, loff_t to) 166 { 167 struct inode *inode = mapping->host; 168 169 if (to > inode->i_size) 170 truncate_pagecache(inode, inode->i_size); 171 } 172 173 static int bfs_write_begin(struct file *file, struct address_space *mapping, 174 loff_t pos, unsigned len, 175 struct page **pagep, void **fsdata) 176 { 177 int ret; 178 179 ret = block_write_begin(mapping, pos, len, pagep, 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 .dirty_folio = block_dirty_folio, 193 .invalidate_folio = block_invalidate_folio, 194 .read_folio = bfs_read_folio, 195 .writepages = bfs_writepages, 196 .write_begin = bfs_write_begin, 197 .write_end = generic_write_end, 198 .migrate_folio = buffer_migrate_folio, 199 .bmap = bfs_bmap, 200 }; 201 202 const struct inode_operations bfs_file_inops; 203