1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/fs/sysv/itree.c
4 *
5 * Handling of indirect blocks' trees.
6 * AV, Sep--Dec 2000
7 */
8
9 #include <linux/buffer_head.h>
10 #include <linux/mount.h>
11 #include <linux/mpage.h>
12 #include <linux/string.h>
13 #include "sysv.h"
14
15 enum {DIRECT = 10, DEPTH = 4}; /* Have triple indirect */
16
17 static inline void dirty_indirect(struct buffer_head *bh, struct inode *inode)
18 {
19 mark_buffer_dirty_inode(bh, inode);
20 if (IS_SYNC(inode))
21 sync_dirty_buffer(bh);
22 }
23
24 static int block_to_path(struct inode *inode, long block, int offsets[DEPTH])
25 {
26 struct super_block *sb = inode->i_sb;
27 struct sysv_sb_info *sbi = SYSV_SB(sb);
28 int ptrs_bits = sbi->s_ind_per_block_bits;
29 unsigned long indirect_blocks = sbi->s_ind_per_block,
30 double_blocks = sbi->s_ind_per_block_2;
31 int n = 0;
32
33 if (block < 0) {
34 printk("sysv_block_map: block < 0\n");
35 } else if (block < DIRECT) {
36 offsets[n++] = block;
37 } else if ( (block -= DIRECT) < indirect_blocks) {
38 offsets[n++] = DIRECT;
39 offsets[n++] = block;
40 } else if ((block -= indirect_blocks) < double_blocks) {
41 offsets[n++] = DIRECT+1;
42 offsets[n++] = block >> ptrs_bits;
43 offsets[n++] = block & (indirect_blocks - 1);
44 } else if (((block -= double_blocks) >> (ptrs_bits * 2)) < indirect_blocks) {
45 offsets[n++] = DIRECT+2;
46 offsets[n++] = block >> (ptrs_bits * 2);
47 offsets[n++] = (block >> ptrs_bits) & (indirect_blocks - 1);
48 offsets[n++] = block & (indirect_blocks - 1);
49 } else {
50 /* nothing */;
51 }
52 return n;
53 }
54
55 static inline int block_to_cpu(struct sysv_sb_info *sbi, sysv_zone_t nr)
56 {
57 return sbi->s_block_base + fs32_to_cpu(sbi, nr);
58 }
59
60 typedef struct {
61 sysv_zone_t *p;
62 sysv_zone_t key;
63 struct buffer_head *bh;
64 } Indirect;
65
66 static DEFINE_RWLOCK(pointers_lock);
67
68 static inline void add_chain(Indirect *p, struct buffer_head *bh, sysv_zone_t *v)
69 {
70 p->key = *(p->p = v);
71 p->bh = bh;
72 }
73
74 static inline int verify_chain(Indirect *from, Indirect *to)
75 {
76 while (from <= to && from->key == *from->p)
77 from++;
78 return (from > to);
79 }
80
81 static inline sysv_zone_t *block_end(struct buffer_head *bh)
82 {
83 return (sysv_zone_t*)((char*)bh->b_data + bh->b_size);
84 }
85
86 static Indirect *get_branch(struct inode *inode,
87 int depth,
88 int offsets[],
89 Indirect chain[],
90 int *err)
91 {
92 struct super_block *sb = inode->i_sb;
93 Indirect *p = chain;
94 struct buffer_head *bh;
95
96 *err = 0;
97 add_chain(chain, NULL, SYSV_I(inode)->i_data + *offsets);
98 if (!p->key)
99 goto no_block;
100 while (--depth) {
101 int block = block_to_cpu(SYSV_SB(sb), p->key);
102 bh = sb_bread(sb, block);
103 if (!bh)
104 goto failure;
105 read_lock(&pointers_lock);
106 if (!verify_chain(chain, p))
107 goto changed;
108 add_chain(++p, bh, (sysv_zone_t*)bh->b_data + *++offsets);
109 read_unlock(&pointers_lock);
110 if (!p->key)
111 goto no_block;
112 }
113 return NULL;
114
115 changed:
116 read_unlock(&pointers_lock);
117 brelse(bh);
118 *err = -EAGAIN;
119 goto no_block;
120 failure:
121 *err = -EIO;
122 no_block:
123 return p;
124 }
125
126 static int alloc_branch(struct inode *inode,
127 int num,
128 int *offsets,
129 Indirect *branch)
130 {
131 int blocksize = inode->i_sb->s_blocksize;
132 int n = 0;
133 int i;
134
135 branch[0].key = sysv_new_block(inode->i_sb);
136 if (branch[0].key) for (n = 1; n < num; n++) {
137 struct buffer_head *bh;
138 int parent;
139 /* Allocate the next block */
140 branch[n].key = sysv_new_block(inode->i_sb);
141 if (!branch[n].key)
142 break;
143 /*
144 * Get buffer_head for parent block, zero it out and set
145 * the pointer to new one, then send parent to disk.
146 */
147 parent = block_to_cpu(SYSV_SB(inode->i_sb), branch[n-1].key);
148 bh = sb_getblk(inode->i_sb, parent);
149 if (!bh) {
150 sysv_free_block(inode->i_sb, branch[n].key);
151 break;
152 }
153 lock_buffer(bh);
154 memset(bh->b_data, 0, blocksize);
155 branch[n].bh = bh;
156 branch[n].p = (sysv_zone_t*) bh->b_data + offsets[n];
157 *branch[n].p = branch[n].key;
158 set_buffer_uptodate(bh);
159 unlock_buffer(bh);
160 dirty_indirect(bh, inode);
161 }
162 if (n == num)
163 return 0;
164
165 /* Allocation failed, free what we already allocated */
166 for (i = 1; i < n; i++)
167 bforget(branch[i].bh);
168 for (i = 0; i < n; i++)
169 sysv_free_block(inode->i_sb, branch[i].key);
170 return -ENOSPC;
171 }
172
173 static inline int splice_branch(struct inode *inode,
174 Indirect chain[],
175 Indirect *where,
176 int num)
177 {
178 int i;
179
180 /* Verify that place we are splicing to is still there and vacant */
181 write_lock(&pointers_lock);
182 if (!verify_chain(chain, where-1) || *where->p)
183 goto changed;
184 *where->p = where->key;
185 write_unlock(&pointers_lock);
186
187 inode_set_ctime_current(inode);
188
189 /* had we spliced it onto indirect block? */
190 if (where->bh)
191 dirty_indirect(where->bh, inode);
192
193 if (IS_SYNC(inode))
194 sysv_sync_inode(inode);
195 else
196 mark_inode_dirty(inode);
197 return 0;
198
199 changed:
200 write_unlock(&pointers_lock);
201 for (i = 1; i < num; i++)
202 bforget(where[i].bh);
203 for (i = 0; i < num; i++)
204 sysv_free_block(inode->i_sb, where[i].key);
205 return -EAGAIN;
206 }
207
208 static int get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create)
209 {
210 int err = -EIO;
211 int offsets[DEPTH];
212 Indirect chain[DEPTH];
213 struct super_block *sb = inode->i_sb;
214 Indirect *partial;
215 int left;
216 int depth = block_to_path(inode, iblock, offsets);
217
218 if (depth == 0)
219 goto out;
220
221 reread:
222 partial = get_branch(inode, depth, offsets, chain, &err);
223
224 /* Simplest case - block found, no allocation needed */
225 if (!partial) {
226 got_it:
227 map_bh(bh_result, sb, block_to_cpu(SYSV_SB(sb),
228 chain[depth-1].key));
229 /* Clean up and exit */
230 partial = chain+depth-1; /* the whole chain */
231 goto cleanup;
232 }
233
234 /* Next simple case - plain lookup or failed read of indirect block */
235 if (!create || err == -EIO) {
236 cleanup:
237 while (partial > chain) {
238 brelse(partial->bh);
239 partial--;
240 }
241 out:
242 return err;
243 }
244
245 /*
246 * Indirect block might be removed by truncate while we were
247 * reading it. Handling of that case (forget what we've got and
248 * reread) is taken out of the main path.
249 */
250 if (err == -EAGAIN)
251 goto changed;
252
253 left = (chain + depth) - partial;
254 err = alloc_branch(inode, left, offsets+(partial-chain), partial);
255 if (err)
256 goto cleanup;
257
258 if (splice_branch(inode, chain, partial, left) < 0)
259 goto changed;
260
261 set_buffer_new(bh_result);
262 goto got_it;
263
264 changed:
265 while (partial > chain) {
266 brelse(partial->bh);
267 partial--;
268 }
269 goto reread;
270 }
271
272 static inline int all_zeroes(sysv_zone_t *p, sysv_zone_t *q)
273 {
274 while (p < q)
275 if (*p++)
276 return 0;
277 return 1;
278 }
279
280 static Indirect *find_shared(struct inode *inode,
281 int depth,
282 int offsets[],
283 Indirect chain[],
284 sysv_zone_t *top)
285 {
286 Indirect *partial, *p;
287 int k, err;
288
289 *top = 0;
290 for (k = depth; k > 1 && !offsets[k-1]; k--)
291 ;
292 partial = get_branch(inode, k, offsets, chain, &err);
293
294 write_lock(&pointers_lock);
295 if (!partial)
296 partial = chain + k-1;
297 /*
298 * If the branch acquired continuation since we've looked at it -
299 * fine, it should all survive and (new) top doesn't belong to us.
300 */
301 if (!partial->key && *partial->p) {
302 write_unlock(&pointers_lock);
303 goto no_top;
304 }
305 for (p=partial; p>chain && all_zeroes((sysv_zone_t*)p->bh->b_data,p->p); p--)
306 ;
307 /*
308 * OK, we've found the last block that must survive. The rest of our
309 * branch should be detached before unlocking. However, if that rest
310 * of branch is all ours and does not grow immediately from the inode
311 * it's easier to cheat and just decrement partial->p.
312 */
313 if (p == chain + k - 1 && p > chain) {
314 p->p--;
315 } else {
316 *top = *p->p;
317 *p->p = 0;
318 }
319 write_unlock(&pointers_lock);
320
321 while (partial > p) {
322 brelse(partial->bh);
323 partial--;
324 }
325 no_top:
326 return partial;
327 }
328
329 static inline void free_data(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q)
330 {
331 for ( ; p < q ; p++) {
332 sysv_zone_t nr = *p;
333 if (nr) {
334 *p = 0;
335 sysv_free_block(inode->i_sb, nr);
336 mark_inode_dirty(inode);
337 }
338 }
339 }
340
341 static void free_branches(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q, int depth)
342 {
343 struct buffer_head * bh;
344 struct super_block *sb = inode->i_sb;
345
346 if (depth--) {
347 for ( ; p < q ; p++) {
348 int block;
349 sysv_zone_t nr = *p;
350 if (!nr)
351 continue;
352 *p = 0;
353 block = block_to_cpu(SYSV_SB(sb), nr);
354 bh = sb_bread(sb, block);
355 if (!bh)
356 continue;
357 free_branches(inode, (sysv_zone_t*)bh->b_data,
358 block_end(bh), depth);
359 bforget(bh);
360 sysv_free_block(sb, nr);
361 mark_inode_dirty(inode);
362 }
363 } else
364 free_data(inode, p, q);
365 }
366
367 void sysv_truncate (struct inode * inode)
368 {
369 sysv_zone_t *i_data = SYSV_I(inode)->i_data;
370 int offsets[DEPTH];
371 Indirect chain[DEPTH];
372 Indirect *partial;
373 sysv_zone_t nr = 0;
374 int n;
375 long iblock;
376 unsigned blocksize;
377
378 if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
379 S_ISLNK(inode->i_mode)))
380 return;
381
382 blocksize = inode->i_sb->s_blocksize;
383 iblock = (inode->i_size + blocksize-1)
384 >> inode->i_sb->s_blocksize_bits;
385
386 block_truncate_page(inode->i_mapping, inode->i_size, get_block);
387
388 n = block_to_path(inode, iblock, offsets);
389 if (n == 0)
390 return;
391
392 if (n == 1) {
393 free_data(inode, i_data+offsets[0], i_data + DIRECT);
394 goto do_indirects;
395 }
396
397 partial = find_shared(inode, n, offsets, chain, &nr);
398 /* Kill the top of shared branch (already detached) */
399 if (nr) {
400 if (partial == chain)
401 mark_inode_dirty(inode);
402 else
403 dirty_indirect(partial->bh, inode);
404 free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
405 }
406 /* Clear the ends of indirect blocks on the shared branch */
407 while (partial > chain) {
408 free_branches(inode, partial->p + 1, block_end(partial->bh),
409 (chain+n-1) - partial);
410 dirty_indirect(partial->bh, inode);
411 brelse (partial->bh);
412 partial--;
413 }
414 do_indirects:
415 /* Kill the remaining (whole) subtrees (== subtrees deeper than...) */
416 while (n < DEPTH) {
417 nr = i_data[DIRECT + n - 1];
418 if (nr) {
419 i_data[DIRECT + n - 1] = 0;
420 mark_inode_dirty(inode);
421 free_branches(inode, &nr, &nr+1, n);
422 }
423 n++;
424 }
425 inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
426 if (IS_SYNC(inode))
427 sysv_sync_inode (inode);
428 else
429 mark_inode_dirty(inode);
430 }
431
432 static unsigned sysv_nblocks(struct super_block *s, loff_t size)
433 {
434 struct sysv_sb_info *sbi = SYSV_SB(s);
435 int ptrs_bits = sbi->s_ind_per_block_bits;
436 unsigned blocks, res, direct = DIRECT, i = DEPTH;
437 blocks = (size + s->s_blocksize - 1) >> s->s_blocksize_bits;
438 res = blocks;
439 while (--i && blocks > direct) {
440 blocks = ((blocks - direct - 1) >> ptrs_bits) + 1;
441 res += blocks;
442 direct = 1;
443 }
444 return res;
445 }
446
447 int sysv_getattr(struct mnt_idmap *idmap, const struct path *path,
448 struct kstat *stat, u32 request_mask, unsigned int flags)
449 {
450 struct super_block *s = path->dentry->d_sb;
451 generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry),
452 stat);
453 stat->blocks = (s->s_blocksize / 512) * sysv_nblocks(s, stat->size);
454 stat->blksize = s->s_blocksize;
455 return 0;
456 }
457
458 static int sysv_writepages(struct address_space *mapping,
459 struct writeback_control *wbc)
460 {
461 return mpage_writepages(mapping, wbc, get_block);
462 }
463
464 static int sysv_read_folio(struct file *file, struct folio *folio)
465 {
466 return block_read_full_folio(folio, get_block);
467 }
468
469 int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len)
470 {
471 return __block_write_begin(page, pos, len, get_block);
472 }
473
474 static void sysv_write_failed(struct address_space *mapping, loff_t to)
475 {
476 struct inode *inode = mapping->host;
477
478 if (to > inode->i_size) {
479 truncate_pagecache(inode, inode->i_size);
480 sysv_truncate(inode);
481 }
482 }
483
484 static int sysv_write_begin(struct file *file, struct address_space *mapping,
485 loff_t pos, unsigned len,
486 struct page **pagep, void **fsdata)
487 {
488 int ret;
489
490 ret = block_write_begin(mapping, pos, len, pagep, get_block);
491 if (unlikely(ret))
492 sysv_write_failed(mapping, pos + len);
493
494 return ret;
495 }
496
497 static sector_t sysv_bmap(struct address_space *mapping, sector_t block)
498 {
499 return generic_block_bmap(mapping,block,get_block);
500 }
501
502 const struct address_space_operations sysv_aops = {
503 .dirty_folio = block_dirty_folio,
504 .invalidate_folio = block_invalidate_folio,
505 .read_folio = sysv_read_folio,
506 .writepages = sysv_writepages,
507 .write_begin = sysv_write_begin,
508 .write_end = generic_write_end,
509 .migrate_folio = buffer_migrate_folio,
510 .bmap = sysv_bmap
511 };
512
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.