1 /* Generic part */
2
3 typedef struct {
4 block_t *p;
5 block_t key;
6 struct buffer_head *bh;
7 } Indirect;
8
9 static DEFINE_RWLOCK(pointers_lock);
10
11 static inline void add_chain(Indirect *p, struct buffer_head *bh, block_t *v)
12 {
13 p->key = *(p->p = v);
14 p->bh = bh;
15 }
16
17 static inline int verify_chain(Indirect *from, Indirect *to)
18 {
19 while (from <= to && from->key == *from->p)
20 from++;
21 return (from > to);
22 }
23
24 static inline block_t *block_end(struct buffer_head *bh)
25 {
26 return (block_t *)((char*)bh->b_data + bh->b_size);
27 }
28
29 static inline Indirect *get_branch(struct inode *inode,
30 int depth,
31 int *offsets,
32 Indirect chain[DEPTH],
33 int *err)
34 {
35 struct super_block *sb = inode->i_sb;
36 Indirect *p = chain;
37 struct buffer_head *bh;
38
39 *err = 0;
40 /* i_data is not going away, no lock needed */
41 add_chain (chain, NULL, i_data(inode) + *offsets);
42 if (!p->key)
43 goto no_block;
44 while (--depth) {
45 bh = sb_bread(sb, block_to_cpu(p->key));
46 if (!bh)
47 goto failure;
48 read_lock(&pointers_lock);
49 if (!verify_chain(chain, p))
50 goto changed;
51 add_chain(++p, bh, (block_t *)bh->b_data + *++offsets);
52 read_unlock(&pointers_lock);
53 if (!p->key)
54 goto no_block;
55 }
56 return NULL;
57
58 changed:
59 read_unlock(&pointers_lock);
60 brelse(bh);
61 *err = -EAGAIN;
62 goto no_block;
63 failure:
64 *err = -EIO;
65 no_block:
66 return p;
67 }
68
69 static int alloc_branch(struct inode *inode,
70 int num,
71 int *offsets,
72 Indirect *branch)
73 {
74 int n = 0;
75 int i;
76 int parent = minix_new_block(inode);
77
78 branch[0].key = cpu_to_block(parent);
79 if (parent) for (n = 1; n < num; n++) {
80 struct buffer_head *bh;
81 /* Allocate the next block */
82 int nr = minix_new_block(inode);
83 if (!nr)
84 break;
85 branch[n].key = cpu_to_block(nr);
86 bh = sb_getblk(inode->i_sb, parent);
87 lock_buffer(bh);
88 memset(bh->b_data, 0, bh->b_size);
89 branch[n].bh = bh;
90 branch[n].p = (block_t*) bh->b_data + offsets[n];
91 *branch[n].p = branch[n].key;
92 set_buffer_uptodate(bh);
93 unlock_buffer(bh);
94 mark_buffer_dirty_inode(bh, inode);
95 parent = nr;
96 }
97 if (n == num)
98 return 0;
99
100 /* Allocation failed, free what we already allocated */
101 for (i = 1; i < n; i++)
102 bforget(branch[i].bh);
103 for (i = 0; i < n; i++)
104 minix_free_block(inode, block_to_cpu(branch[i].key));
105 return -ENOSPC;
106 }
107
108 static inline int splice_branch(struct inode *inode,
109 Indirect chain[DEPTH],
110 Indirect *where,
111 int num)
112 {
113 int i;
114
115 write_lock(&pointers_lock);
116
117 /* Verify that place we are splicing to is still there and vacant */
118 if (!verify_chain(chain, where-1) || *where->p)
119 goto changed;
120
121 *where->p = where->key;
122
123 write_unlock(&pointers_lock);
124
125 /* We are done with atomic stuff, now do the rest of housekeeping */
126
127 inode->i_ctime = CURRENT_TIME_SEC;
128
129 /* had we spliced it onto indirect block? */
130 if (where->bh)
131 mark_buffer_dirty_inode(where->bh, inode);
132
133 mark_inode_dirty(inode);
134 return 0;
135
136 changed:
137 write_unlock(&pointers_lock);
138 for (i = 1; i < num; i++)
139 bforget(where[i].bh);
140 for (i = 0; i < num; i++)
141 minix_free_block(inode, block_to_cpu(where[i].key));
142 return -EAGAIN;
143 }
144
145 static inline int get_block(struct inode * inode, sector_t block,
146 struct buffer_head *bh, int create)
147 {
148 int err = -EIO;
149 int offsets[DEPTH];
150 Indirect chain[DEPTH];
151 Indirect *partial;
152 int left;
153 int depth = block_to_path(inode, block, offsets);
154
155 if (depth == 0)
156 goto out;
157
158 reread:
159 partial = get_branch(inode, depth, offsets, chain, &err);
160
161 /* Simplest case - block found, no allocation needed */
162 if (!partial) {
163 got_it:
164 map_bh(bh, inode->i_sb, block_to_cpu(chain[depth-1].key));
165 /* Clean up and exit */
166 partial = chain+depth-1; /* the whole chain */
167 goto cleanup;
168 }
169
170 /* Next simple case - plain lookup or failed read of indirect block */
171 if (!create || err == -EIO) {
172 cleanup:
173 while (partial > chain) {
174 brelse(partial->bh);
175 partial--;
176 }
177 out:
178 return err;
179 }
180
181 /*
182 * Indirect block might be removed by truncate while we were
183 * reading it. Handling of that case (forget what we've got and
184 * reread) is taken out of the main path.
185 */
186 if (err == -EAGAIN)
187 goto changed;
188
189 left = (chain + depth) - partial;
190 err = alloc_branch(inode, left, offsets+(partial-chain), partial);
191 if (err)
192 goto cleanup;
193
194 if (splice_branch(inode, chain, partial, left) < 0)
195 goto changed;
196
197 set_buffer_new(bh);
198 goto got_it;
199
200 changed:
201 while (partial > chain) {
202 brelse(partial->bh);
203 partial--;
204 }
205 goto reread;
206 }
207
208 static inline int all_zeroes(block_t *p, block_t *q)
209 {
210 while (p < q)
211 if (*p++)
212 return 0;
213 return 1;
214 }
215
216 static Indirect *find_shared(struct inode *inode,
217 int depth,
218 int offsets[DEPTH],
219 Indirect chain[DEPTH],
220 block_t *top)
221 {
222 Indirect *partial, *p;
223 int k, err;
224
225 *top = 0;
226 for (k = depth; k > 1 && !offsets[k-1]; k--)
227 ;
228 partial = get_branch(inode, k, offsets, chain, &err);
229
230 write_lock(&pointers_lock);
231 if (!partial)
232 partial = chain + k-1;
233 if (!partial->key && *partial->p) {
234 write_unlock(&pointers_lock);
235 goto no_top;
236 }
237 for (p=partial;p>chain && all_zeroes((block_t*)p->bh->b_data,p->p);p--)
238 ;
239 if (p == chain + k - 1 && p > chain) {
240 p->p--;
241 } else {
242 *top = *p->p;
243 *p->p = 0;
244 }
245 write_unlock(&pointers_lock);
246
247 while(partial > p)
248 {
249 brelse(partial->bh);
250 partial--;
251 }
252 no_top:
253 return partial;
254 }
255
256 static inline void free_data(struct inode *inode, block_t *p, block_t *q)
257 {
258 unsigned long nr;
259
260 for ( ; p < q ; p++) {
261 nr = block_to_cpu(*p);
262 if (nr) {
263 *p = 0;
264 minix_free_block(inode, nr);
265 }
266 }
267 }
268
269 static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth)
270 {
271 struct buffer_head * bh;
272 unsigned long nr;
273
274 if (depth--) {
275 for ( ; p < q ; p++) {
276 nr = block_to_cpu(*p);
277 if (!nr)
278 continue;
279 *p = 0;
280 bh = sb_bread(inode->i_sb, nr);
281 if (!bh)
282 continue;
283 free_branches(inode, (block_t*)bh->b_data,
284 block_end(bh), depth);
285 bforget(bh);
286 minix_free_block(inode, nr);
287 mark_inode_dirty(inode);
288 }
289 } else
290 free_data(inode, p, q);
291 }
292
293 static inline void truncate (struct inode * inode)
294 {
295 struct super_block *sb = inode->i_sb;
296 block_t *idata = i_data(inode);
297 int offsets[DEPTH];
298 Indirect chain[DEPTH];
299 Indirect *partial;
300 block_t nr = 0;
301 int n;
302 int first_whole;
303 long iblock;
304
305 iblock = (inode->i_size + sb->s_blocksize -1) >> sb->s_blocksize_bits;
306 block_truncate_page(inode->i_mapping, inode->i_size, get_block);
307
308 n = block_to_path(inode, iblock, offsets);
309 if (!n)
310 return;
311
312 if (n == 1) {
313 free_data(inode, idata+offsets[0], idata + DIRECT);
314 first_whole = 0;
315 goto do_indirects;
316 }
317
318 first_whole = offsets[0] + 1 - DIRECT;
319 partial = find_shared(inode, n, offsets, chain, &nr);
320 if (nr) {
321 if (partial == chain)
322 mark_inode_dirty(inode);
323 else
324 mark_buffer_dirty_inode(partial->bh, inode);
325 free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
326 }
327 /* Clear the ends of indirect blocks on the shared branch */
328 while (partial > chain) {
329 free_branches(inode, partial->p + 1, block_end(partial->bh),
330 (chain+n-1) - partial);
331 mark_buffer_dirty_inode(partial->bh, inode);
332 brelse (partial->bh);
333 partial--;
334 }
335 do_indirects:
336 /* Kill the remaining (whole) subtrees */
337 while (first_whole < DEPTH-1) {
338 nr = idata[DIRECT+first_whole];
339 if (nr) {
340 idata[DIRECT+first_whole] = 0;
341 mark_inode_dirty(inode);
342 free_branches(inode, &nr, &nr+1, first_whole+1);
343 }
344 first_whole++;
345 }
346 inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
347 mark_inode_dirty(inode);
348 }
349
350 static inline unsigned nblocks(loff_t size, struct super_block *sb)
351 {
352 int k = sb->s_blocksize_bits - 10;
353 unsigned blocks, res, direct = DIRECT, i = DEPTH;
354 blocks = (size + sb->s_blocksize - 1) >> (BLOCK_SIZE_BITS + k);
355 res = blocks;
356 while (--i && blocks > direct) {
357 blocks -= direct;
358 blocks += sb->s_blocksize/sizeof(block_t) - 1;
359 blocks /= sb->s_blocksize/sizeof(block_t);
360 res += blocks;
361 direct = 1;
362 }
363 return res;
364 }
365
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