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374 lines · 7.9 KiB

1// SPDX-License-Identifier: GPL-2.0
2/* Generic part */
3
4typedef struct {
5 block_t *p;
6 block_t key;
7 struct buffer_head *bh;
8} Indirect;
9
10static DEFINE_RWLOCK(pointers_lock);
11
12static inline void add_chain(Indirect *p, struct buffer_head *bh, block_t *v)
13{
14 p->key = *(p->p = v);
15 p->bh = bh;
16}
17
18static inline int verify_chain(Indirect *from, Indirect *to)
19{
20 while (from <= to && from->key == *from->p)
21 from++;
22 return (from > to);
23}
24
25static inline block_t *block_end(struct buffer_head *bh)
26{
27 return (block_t *)((char*)bh->b_data + bh->b_size);
28}
29
30static inline Indirect *get_branch(struct inode *inode,
31 int depth,
32 int *offsets,
33 Indirect chain[DEPTH],
34 int *err)
35{
36 struct super_block *sb = inode->i_sb;
37 Indirect *p = chain;
38 struct buffer_head *bh;
39
40 *err = 0;
41 /* i_data is not going away, no lock needed */
42 add_chain (chain, NULL, i_data(inode) + *offsets);
43 if (!p->key)
44 goto no_block;
45 while (--depth) {
46 bh = sb_bread(sb, block_to_cpu(p->key));
47 if (!bh)
48 goto failure;
49 read_lock(&pointers_lock);
50 if (!verify_chain(chain, p))
51 goto changed;
52 add_chain(++p, bh, (block_t *)bh->b_data + *++offsets);
53 read_unlock(&pointers_lock);
54 if (!p->key)
55 goto no_block;
56 }
57 return NULL;
58
59changed:
60 read_unlock(&pointers_lock);
61 brelse(bh);
62 *err = -EAGAIN;
63 goto no_block;
64failure:
65 *err = -EIO;
66no_block:
67 return p;
68}
69
70static int alloc_branch(struct inode *inode,
71 int num,
72 int *offsets,
73 Indirect *branch)
74{
75 int n = 0;
76 int i;
77 int parent = minix_new_block(inode);
78 int err = -ENOSPC;
79
80 branch[0].key = cpu_to_block(parent);
81 if (parent) for (n = 1; n < num; n++) {
82 struct buffer_head *bh;
83 /* Allocate the next block */
84 int nr = minix_new_block(inode);
85 if (!nr)
86 break;
87 branch[n].key = cpu_to_block(nr);
88 bh = sb_getblk(inode->i_sb, parent);
89 if (!bh) {
90 minix_free_block(inode, nr);
91 err = -ENOMEM;
92 break;
93 }
94 lock_buffer(bh);
95 memset(bh->b_data, 0, bh->b_size);
96 branch[n].bh = bh;
97 branch[n].p = (block_t*) bh->b_data + offsets[n];
98 *branch[n].p = branch[n].key;
99 set_buffer_uptodate(bh);
100 unlock_buffer(bh);
101 mmb_mark_buffer_dirty(bh, &minix_i(inode)->i_metadata_bhs);
102 parent = nr;
103 }
104 if (n == num)
105 return 0;
106
107 /* Allocation failed, free what we already allocated */
108 for (i = 1; i < n; i++)
109 bforget(branch[i].bh);
110 for (i = 0; i < n; i++)
111 minix_free_block(inode, block_to_cpu(branch[i].key));
112 return err;
113}
114
115static inline int splice_branch(struct inode *inode,
116 Indirect chain[DEPTH],
117 Indirect *where,
118 int num)
119{
120 int i;
121
122 write_lock(&pointers_lock);
123
124 /* Verify that place we are splicing to is still there and vacant */
125 if (!verify_chain(chain, where-1) || *where->p)
126 goto changed;
127
128 *where->p = where->key;
129
130 write_unlock(&pointers_lock);
131
132 /* We are done with atomic stuff, now do the rest of housekeeping */
133
134 inode_set_ctime_current(inode);
135
136 /* had we spliced it onto indirect block? */
137 if (where->bh)
138 mmb_mark_buffer_dirty(where->bh,
139 &minix_i(inode)->i_metadata_bhs);
140
141 mark_inode_dirty(inode);
142 return 0;
143
144changed:
145 write_unlock(&pointers_lock);
146 for (i = 1; i < num; i++)
147 bforget(where[i].bh);
148 for (i = 0; i < num; i++)
149 minix_free_block(inode, block_to_cpu(where[i].key));
150 return -EAGAIN;
151}
152
153static int get_block(struct inode * inode, sector_t block,
154 struct buffer_head *bh, int create)
155{
156 int err = -EIO;
157 int offsets[DEPTH];
158 Indirect chain[DEPTH];
159 Indirect *partial;
160 int left;
161 int depth = block_to_path(inode, block, offsets);
162
163 if (depth == 0)
164 goto out;
165
166reread:
167 partial = get_branch(inode, depth, offsets, chain, &err);
168
169 /* Simplest case - block found, no allocation needed */
170 if (!partial) {
171got_it:
172 map_bh(bh, inode->i_sb, block_to_cpu(chain[depth-1].key));
173 /* Clean up and exit */
174 partial = chain+depth-1; /* the whole chain */
175 goto cleanup;
176 }
177
178 /* Next simple case - plain lookup or failed read of indirect block */
179 if (!create || err == -EIO) {
180cleanup:
181 while (partial > chain) {
182 brelse(partial->bh);
183 partial--;
184 }
185out:
186 return err;
187 }
188
189 /*
190 * Indirect block might be removed by truncate while we were
191 * reading it. Handling of that case (forget what we've got and
192 * reread) is taken out of the main path.
193 */
194 if (err == -EAGAIN)
195 goto changed;
196
197 left = (chain + depth) - partial;
198 err = alloc_branch(inode, left, offsets+(partial-chain), partial);
199 if (err)
200 goto cleanup;
201
202 if (splice_branch(inode, chain, partial, left) < 0)
203 goto changed;
204
205 set_buffer_new(bh);
206 goto got_it;
207
208changed:
209 while (partial > chain) {
210 brelse(partial->bh);
211 partial--;
212 }
213 goto reread;
214}
215
216static inline int all_zeroes(block_t *p, block_t *q)
217{
218 while (p < q)
219 if (*p++)
220 return 0;
221 return 1;
222}
223
224static Indirect *find_shared(struct inode *inode,
225 int depth,
226 int offsets[DEPTH],
227 Indirect chain[DEPTH],
228 block_t *top)
229{
230 Indirect *partial, *p;
231 int k, err;
232
233 *top = 0;
234 for (k = depth; k > 1 && !offsets[k-1]; k--)
235 ;
236 partial = get_branch(inode, k, offsets, chain, &err);
237
238 write_lock(&pointers_lock);
239 if (!partial)
240 partial = chain + k-1;
241 if (!partial->key && *partial->p) {
242 write_unlock(&pointers_lock);
243 goto no_top;
244 }
245 for (p=partial;p>chain && all_zeroes((block_t*)p->bh->b_data,p->p);p--)
246 ;
247 if (p == chain + k - 1 && p > chain) {
248 p->p--;
249 } else {
250 *top = *p->p;
251 *p->p = 0;
252 }
253 write_unlock(&pointers_lock);
254
255 while(partial > p)
256 {
257 brelse(partial->bh);
258 partial--;
259 }
260no_top:
261 return partial;
262}
263
264static inline void free_data(struct inode *inode, block_t *p, block_t *q)
265{
266 unsigned long nr;
267
268 for ( ; p < q ; p++) {
269 nr = block_to_cpu(*p);
270 if (nr) {
271 *p = 0;
272 minix_free_block(inode, nr);
273 }
274 }
275}
276
277static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth)
278{
279 struct buffer_head * bh;
280 unsigned long nr;
281
282 if (depth--) {
283 for ( ; p < q ; p++) {
284 nr = block_to_cpu(*p);
285 if (!nr)
286 continue;
287 *p = 0;
288 bh = sb_bread(inode->i_sb, nr);
289 if (!bh)
290 continue;
291 free_branches(inode, (block_t*)bh->b_data,
292 block_end(bh), depth);
293 bforget(bh);
294 minix_free_block(inode, nr);
295 mark_inode_dirty(inode);
296 }
297 } else
298 free_data(inode, p, q);
299}
300
301static inline void truncate (struct inode * inode)
302{
303 struct super_block *sb = inode->i_sb;
304 block_t *idata = i_data(inode);
305 int offsets[DEPTH];
306 Indirect chain[DEPTH];
307 Indirect *partial;
308 block_t nr = 0;
309 int n;
310 int first_whole;
311 long iblock;
312
313 iblock = (inode->i_size + sb->s_blocksize -1) >> sb->s_blocksize_bits;
314 block_truncate_page(inode->i_mapping, inode->i_size, get_block);
315
316 n = block_to_path(inode, iblock, offsets);
317 if (!n)
318 return;
319
320 if (n == 1) {
321 free_data(inode, idata+offsets[0], idata + DIRECT);
322 first_whole = 0;
323 goto do_indirects;
324 }
325
326 first_whole = offsets[0] + 1 - DIRECT;
327 partial = find_shared(inode, n, offsets, chain, &nr);
328 if (nr) {
329 if (partial == chain)
330 mark_inode_dirty(inode);
331 else
332 mmb_mark_buffer_dirty(partial->bh,
333 &minix_i(inode)->i_metadata_bhs);
334 free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
335 }
336 /* Clear the ends of indirect blocks on the shared branch */
337 while (partial > chain) {
338 free_branches(inode, partial->p + 1, block_end(partial->bh),
339 (chain+n-1) - partial);
340 mmb_mark_buffer_dirty(partial->bh,
341 &minix_i(inode)->i_metadata_bhs);
342 brelse (partial->bh);
343 partial--;
344 }
345do_indirects:
346 /* Kill the remaining (whole) subtrees */
347 while (first_whole < DEPTH-1) {
348 nr = idata[DIRECT+first_whole];
349 if (nr) {
350 idata[DIRECT+first_whole] = 0;
351 mark_inode_dirty(inode);
352 free_branches(inode, &nr, &nr+1, first_whole+1);
353 }
354 first_whole++;
355 }
356 inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
357 mark_inode_dirty(inode);
358}
359
360static inline unsigned nblocks(loff_t size, struct super_block *sb)
361{
362 int k = sb->s_blocksize_bits - 10;
363 unsigned blocks, res, direct = DIRECT, i = DEPTH;
364 blocks = (size + sb->s_blocksize - 1) >> (BLOCK_SIZE_BITS + k);
365 res = blocks;
366 while (--i && blocks > direct) {
367 blocks -= direct;
368 blocks += sb->s_blocksize/sizeof(block_t) - 1;
369 blocks /= sb->s_blocksize/sizeof(block_t);
370 res += blocks;
371 direct = 1;
372 }
373 return res;
374}