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
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