File: /usr/src/linux/fs/efs/inode.c
1 /*
2 * inode.c
3 *
4 * Copyright (c) 1999 Al Smith
5 *
6 * Portions derived from work (c) 1995,1996 Christian Vogelgsang,
7 * and from work (c) 1998 Mike Shaver.
8 */
9
10 #include <linux/efs_fs.h>
11 #include <linux/efs_fs_sb.h>
12
13 extern int efs_get_block(struct inode *, long, struct buffer_head *, int);
14 static int efs_readpage(struct file *file, struct page *page)
15 {
16 return block_read_full_page(page,efs_get_block);
17 }
18 static int _efs_bmap(struct address_space *mapping, long block)
19 {
20 return generic_block_bmap(mapping,block,efs_get_block);
21 }
22 struct address_space_operations efs_aops = {
23 readpage: efs_readpage,
24 sync_page: block_sync_page,
25 bmap: _efs_bmap
26 };
27
28 static inline void extent_copy(efs_extent *src, efs_extent *dst) {
29 /*
30 * this is slightly evil. it doesn't just copy
31 * efs_extent from src to dst, it also mangles
32 * the bits so that dst ends up in cpu byte-order.
33 */
34
35 dst->cooked.ex_magic = (unsigned int) src->raw[0];
36 dst->cooked.ex_bn = ((unsigned int) src->raw[1] << 16) |
37 ((unsigned int) src->raw[2] << 8) |
38 ((unsigned int) src->raw[3] << 0);
39 dst->cooked.ex_length = (unsigned int) src->raw[4];
40 dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
41 ((unsigned int) src->raw[6] << 8) |
42 ((unsigned int) src->raw[7] << 0);
43 return;
44 }
45
46 void efs_read_inode(struct inode *inode) {
47 int i, inode_index;
48 dev_t device;
49 struct buffer_head *bh;
50 struct efs_sb_info *sb = SUPER_INFO(inode->i_sb);
51 struct efs_inode_info *in = INODE_INFO(inode);
52 efs_block_t block, offset;
53 struct efs_dinode *efs_inode;
54
55 /*
56 ** EFS layout:
57 **
58 ** | cylinder group | cylinder group | cylinder group ..etc
59 ** |inodes|data |inodes|data |inodes|data ..etc
60 **
61 ** work out the inode block index, (considering initially that the
62 ** inodes are stored as consecutive blocks). then work out the block
63 ** number of that inode given the above layout, and finally the
64 ** offset of the inode within that block.
65 */
66
67 inode_index = inode->i_ino /
68 (EFS_BLOCKSIZE / sizeof(struct efs_dinode));
69
70 block = sb->fs_start + sb->first_block +
71 (sb->group_size * (inode_index / sb->inode_blocks)) +
72 (inode_index % sb->inode_blocks);
73
74 offset = (inode->i_ino %
75 (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
76 sizeof(struct efs_dinode);
77
78 bh = bread(inode->i_dev, block, EFS_BLOCKSIZE);
79 if (!bh) {
80 printk(KERN_WARNING "EFS: bread() failed at block %d\n", block);
81 goto read_inode_error;
82 }
83
84 efs_inode = (struct efs_dinode *) (bh->b_data + offset);
85
86 inode->i_mode = be16_to_cpu(efs_inode->di_mode);
87 inode->i_nlink = be16_to_cpu(efs_inode->di_nlink);
88 inode->i_uid = (uid_t)be16_to_cpu(efs_inode->di_uid);
89 inode->i_gid = (gid_t)be16_to_cpu(efs_inode->di_gid);
90 inode->i_size = be32_to_cpu(efs_inode->di_size);
91 inode->i_atime = be32_to_cpu(efs_inode->di_atime);
92 inode->i_mtime = be32_to_cpu(efs_inode->di_mtime);
93 inode->i_ctime = be32_to_cpu(efs_inode->di_ctime);
94
95 /* this is the number of blocks in the file */
96 if (inode->i_size == 0) {
97 inode->i_blocks = 0;
98 } else {
99 inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
100 }
101
102 /*
103 * BUG: irix dev_t is 32-bits. linux dev_t is only 16-bits.
104 *
105 * apparently linux will change to 32-bit dev_t sometime during
106 * linux 2.3.
107 *
108 * as is, this code maps devices that can't be represented in
109 * 16-bits (ie major > 255 or minor > 255) to major = minor = 255.
110 *
111 * during 2.3 when 32-bit dev_t become available, we should test
112 * to see whether odev contains 65535. if this is the case then we
113 * should then do device = be32_to_cpu(efs_inode->di_u.di_dev.ndev).
114 */
115 device = be16_to_cpu(efs_inode->di_u.di_dev.odev);
116
117 /* get the number of extents for this object */
118 in->numextents = be16_to_cpu(efs_inode->di_numextents);
119 in->lastextent = 0;
120
121 /* copy the extents contained within the inode to memory */
122 for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
123 extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
124 if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
125 printk(KERN_WARNING "EFS: extent %d has bad magic number in inode %lu\n", i, inode->i_ino);
126 brelse(bh);
127 goto read_inode_error;
128 }
129 }
130
131 brelse(bh);
132
133 #ifdef DEBUG
134 printk(KERN_DEBUG "EFS: read_inode(): inode %lu, extents %d, mode %o\n",
135 inode->i_ino, in->numextents, inode->i_mode);
136 #endif
137
138 switch (inode->i_mode & S_IFMT) {
139 case S_IFDIR:
140 inode->i_op = &efs_dir_inode_operations;
141 inode->i_fop = &efs_dir_operations;
142 break;
143 case S_IFREG:
144 inode->i_fop = &generic_ro_fops;
145 inode->i_data.a_ops = &efs_aops;
146 break;
147 case S_IFLNK:
148 inode->i_op = &page_symlink_inode_operations;
149 inode->i_data.a_ops = &efs_symlink_aops;
150 break;
151 case S_IFCHR:
152 case S_IFBLK:
153 case S_IFIFO:
154 init_special_inode(inode, inode->i_mode, device);
155 break;
156 default:
157 printk(KERN_WARNING "EFS: unsupported inode mode %o\n", inode->i_mode);
158 goto read_inode_error;
159 break;
160 }
161
162 return;
163
164 read_inode_error:
165 printk(KERN_WARNING "EFS: failed to read inode %lu\n", inode->i_ino);
166 make_bad_inode(inode);
167
168 return;
169 }
170
171 static inline efs_block_t
172 efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
173 efs_block_t start;
174 efs_block_t length;
175 efs_block_t offset;
176
177 /*
178 * given an extent and a logical block within a file,
179 * can this block be found within this extent ?
180 */
181 start = ptr->cooked.ex_bn;
182 length = ptr->cooked.ex_length;
183 offset = ptr->cooked.ex_offset;
184
185 if ((block >= offset) && (block < offset+length)) {
186 return(sb->fs_start + start + block - offset);
187 } else {
188 return 0;
189 }
190 }
191
192 efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
193 struct efs_sb_info *sb = SUPER_INFO(inode->i_sb);
194 struct efs_inode_info *in = INODE_INFO(inode);
195 struct buffer_head *bh = NULL;
196
197 int cur, last, first = 1;
198 int ibase, ioffset, dirext, direxts, indext, indexts;
199 efs_block_t iblock, result = 0, lastblock = 0;
200 efs_extent ext, *exts;
201
202 last = in->lastextent;
203
204 if (in->numextents <= EFS_DIRECTEXTENTS) {
205 /* first check the last extent we returned */
206 if ((result = efs_extent_check(&in->extents[last], block, sb)))
207 return result;
208
209 /* if we only have one extent then nothing can be found */
210 if (in->numextents == 1) {
211 printk(KERN_ERR "EFS: map_block() failed to map (1 extent)\n");
212 return 0;
213 }
214
215 direxts = in->numextents;
216
217 /*
218 * check the stored extents in the inode
219 * start with next extent and check forwards
220 */
221 for(dirext = 1; dirext < direxts; dirext++) {
222 cur = (last + dirext) % in->numextents;
223 if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
224 in->lastextent = cur;
225 return result;
226 }
227 }
228
229 printk(KERN_ERR "EFS: map_block() failed to map block %u (dir)\n", block);
230 return 0;
231 }
232
233 #ifdef DEBUG
234 printk(KERN_DEBUG "EFS: map_block(): indirect search for logical block %u\n", block);
235 #endif
236 direxts = in->extents[0].cooked.ex_offset;
237 indexts = in->numextents;
238
239 for(indext = 0; indext < indexts; indext++) {
240 cur = (last + indext) % indexts;
241
242 /*
243 * work out which direct extent contains `cur'.
244 *
245 * also compute ibase: i.e. the number of the first
246 * indirect extent contained within direct extent `cur'.
247 *
248 */
249 ibase = 0;
250 for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
251 ibase += in->extents[dirext].cooked.ex_length *
252 (EFS_BLOCKSIZE / sizeof(efs_extent));
253 }
254
255 if (dirext == direxts) {
256 /* should never happen */
257 printk(KERN_ERR "EFS: couldn't find direct extent for indirect extent %d (block %u)\n", cur, block);
258 if (bh) brelse(bh);
259 return 0;
260 }
261
262 /* work out block number and offset of this indirect extent */
263 iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
264 (cur - ibase) /
265 (EFS_BLOCKSIZE / sizeof(efs_extent));
266 ioffset = (cur - ibase) %
267 (EFS_BLOCKSIZE / sizeof(efs_extent));
268
269 if (first || lastblock != iblock) {
270 if (bh) brelse(bh);
271
272 bh = bread(inode->i_dev, iblock, EFS_BLOCKSIZE);
273 if (!bh) {
274 printk(KERN_ERR "EFS: bread() failed at block %d\n", iblock);
275 return 0;
276 }
277 #ifdef DEBUG
278 printk(KERN_DEBUG "EFS: map_block(): read indirect extent block %d\n", iblock);
279 #endif
280 first = 0;
281 lastblock = iblock;
282 }
283
284 exts = (efs_extent *) bh->b_data;
285
286 extent_copy(&(exts[ioffset]), &ext);
287
288 if (ext.cooked.ex_magic != 0) {
289 printk(KERN_ERR "EFS: extent %d has bad magic number in block %d\n", cur, iblock);
290 if (bh) brelse(bh);
291 return 0;
292 }
293
294 if ((result = efs_extent_check(&ext, block, sb))) {
295 if (bh) brelse(bh);
296 in->lastextent = cur;
297 return result;
298 }
299 }
300 if (bh) brelse(bh);
301 printk(KERN_ERR "EFS: map_block() failed to map block %u (indir)\n", block);
302 return 0;
303 }
304
305