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
dirty_indirect(struct buffer_head * bh,struct inode * inode)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
block_to_path(struct inode * inode,long block,int offsets[DEPTH])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
block_to_cpu(struct sysv_sb_info * sbi,sysv_zone_t nr)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
add_chain(Indirect * p,struct buffer_head * bh,sysv_zone_t * v)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
verify_chain(Indirect * from,Indirect * to)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
block_end(struct buffer_head * bh)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 /*
87 * Requires read_lock(&pointers_lock) or write_lock(&pointers_lock)
88 */
get_branch(struct inode * inode,int depth,int offsets[],Indirect chain[],int * err)89 static Indirect *get_branch(struct inode *inode,
90 int depth,
91 int offsets[],
92 Indirect chain[],
93 int *err)
94 {
95 struct super_block *sb = inode->i_sb;
96 Indirect *p = chain;
97 struct buffer_head *bh;
98
99 *err = 0;
100 add_chain(chain, NULL, SYSV_I(inode)->i_data + *offsets);
101 if (!p->key)
102 goto no_block;
103 while (--depth) {
104 int block = block_to_cpu(SYSV_SB(sb), p->key);
105 bh = sb_bread(sb, block);
106 if (!bh)
107 goto failure;
108 if (!verify_chain(chain, p))
109 goto changed;
110 add_chain(++p, bh, (sysv_zone_t*)bh->b_data + *++offsets);
111 if (!p->key)
112 goto no_block;
113 }
114 return NULL;
115
116 changed:
117 brelse(bh);
118 *err = -EAGAIN;
119 goto no_block;
120 failure:
121 *err = -EIO;
122 no_block:
123 return p;
124 }
125
alloc_branch(struct inode * inode,int num,int * offsets,Indirect * branch)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
splice_branch(struct inode * inode,Indirect chain[],Indirect * where,int num)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
get_block(struct inode * inode,sector_t iblock,struct buffer_head * bh_result,int create)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 read_lock(&pointers_lock);
223 partial = get_branch(inode, depth, offsets, chain, &err);
224 read_unlock(&pointers_lock);
225
226 /* Simplest case - block found, no allocation needed */
227 if (!partial) {
228 got_it:
229 map_bh(bh_result, sb, block_to_cpu(SYSV_SB(sb),
230 chain[depth-1].key));
231 /* Clean up and exit */
232 partial = chain+depth-1; /* the whole chain */
233 goto cleanup;
234 }
235
236 /* Next simple case - plain lookup or failed read of indirect block */
237 if (!create || err == -EIO) {
238 cleanup:
239 while (partial > chain) {
240 brelse(partial->bh);
241 partial--;
242 }
243 out:
244 return err;
245 }
246
247 /*
248 * Indirect block might be removed by truncate while we were
249 * reading it. Handling of that case (forget what we've got and
250 * reread) is taken out of the main path.
251 */
252 if (err == -EAGAIN)
253 goto changed;
254
255 left = (chain + depth) - partial;
256 err = alloc_branch(inode, left, offsets+(partial-chain), partial);
257 if (err)
258 goto cleanup;
259
260 if (splice_branch(inode, chain, partial, left) < 0)
261 goto changed;
262
263 set_buffer_new(bh_result);
264 goto got_it;
265
266 changed:
267 while (partial > chain) {
268 brelse(partial->bh);
269 partial--;
270 }
271 goto reread;
272 }
273
all_zeroes(sysv_zone_t * p,sysv_zone_t * q)274 static inline int all_zeroes(sysv_zone_t *p, sysv_zone_t *q)
275 {
276 while (p < q)
277 if (*p++)
278 return 0;
279 return 1;
280 }
281
find_shared(struct inode * inode,int depth,int offsets[],Indirect chain[],sysv_zone_t * top)282 static Indirect *find_shared(struct inode *inode,
283 int depth,
284 int offsets[],
285 Indirect chain[],
286 sysv_zone_t *top)
287 {
288 Indirect *partial, *p;
289 int k, err;
290
291 *top = 0;
292 for (k = depth; k > 1 && !offsets[k-1]; k--)
293 ;
294
295 write_lock(&pointers_lock);
296 partial = get_branch(inode, k, offsets, chain, &err);
297 if (!partial)
298 partial = chain + k-1;
299 /*
300 * If the branch acquired continuation since we've looked at it -
301 * fine, it should all survive and (new) top doesn't belong to us.
302 */
303 if (!partial->key && *partial->p) {
304 write_unlock(&pointers_lock);
305 goto no_top;
306 }
307 for (p=partial; p>chain && all_zeroes((sysv_zone_t*)p->bh->b_data,p->p); p--)
308 ;
309 /*
310 * OK, we've found the last block that must survive. The rest of our
311 * branch should be detached before unlocking. However, if that rest
312 * of branch is all ours and does not grow immediately from the inode
313 * it's easier to cheat and just decrement partial->p.
314 */
315 if (p == chain + k - 1 && p > chain) {
316 p->p--;
317 } else {
318 *top = *p->p;
319 *p->p = 0;
320 }
321 write_unlock(&pointers_lock);
322
323 while (partial > p) {
324 brelse(partial->bh);
325 partial--;
326 }
327 no_top:
328 return partial;
329 }
330
free_data(struct inode * inode,sysv_zone_t * p,sysv_zone_t * q)331 static inline void free_data(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q)
332 {
333 for ( ; p < q ; p++) {
334 sysv_zone_t nr = *p;
335 if (nr) {
336 *p = 0;
337 sysv_free_block(inode->i_sb, nr);
338 mark_inode_dirty(inode);
339 }
340 }
341 }
342
free_branches(struct inode * inode,sysv_zone_t * p,sysv_zone_t * q,int depth)343 static void free_branches(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q, int depth)
344 {
345 struct buffer_head * bh;
346 struct super_block *sb = inode->i_sb;
347
348 if (depth--) {
349 for ( ; p < q ; p++) {
350 int block;
351 sysv_zone_t nr = *p;
352 if (!nr)
353 continue;
354 *p = 0;
355 block = block_to_cpu(SYSV_SB(sb), nr);
356 bh = sb_bread(sb, block);
357 if (!bh)
358 continue;
359 free_branches(inode, (sysv_zone_t*)bh->b_data,
360 block_end(bh), depth);
361 bforget(bh);
362 sysv_free_block(sb, nr);
363 mark_inode_dirty(inode);
364 }
365 } else
366 free_data(inode, p, q);
367 }
368
sysv_truncate(struct inode * inode)369 void sysv_truncate (struct inode * inode)
370 {
371 sysv_zone_t *i_data = SYSV_I(inode)->i_data;
372 int offsets[DEPTH];
373 Indirect chain[DEPTH];
374 Indirect *partial;
375 sysv_zone_t nr = 0;
376 int n;
377 long iblock;
378 unsigned blocksize;
379
380 if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
381 S_ISLNK(inode->i_mode)))
382 return;
383
384 blocksize = inode->i_sb->s_blocksize;
385 iblock = (inode->i_size + blocksize-1)
386 >> inode->i_sb->s_blocksize_bits;
387
388 block_truncate_page(inode->i_mapping, inode->i_size, get_block);
389
390 n = block_to_path(inode, iblock, offsets);
391 if (n == 0)
392 return;
393
394 if (n == 1) {
395 free_data(inode, i_data+offsets[0], i_data + DIRECT);
396 goto do_indirects;
397 }
398
399 partial = find_shared(inode, n, offsets, chain, &nr);
400 /* Kill the top of shared branch (already detached) */
401 if (nr) {
402 if (partial == chain)
403 mark_inode_dirty(inode);
404 else
405 dirty_indirect(partial->bh, inode);
406 free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
407 }
408 /* Clear the ends of indirect blocks on the shared branch */
409 while (partial > chain) {
410 free_branches(inode, partial->p + 1, block_end(partial->bh),
411 (chain+n-1) - partial);
412 dirty_indirect(partial->bh, inode);
413 brelse (partial->bh);
414 partial--;
415 }
416 do_indirects:
417 /* Kill the remaining (whole) subtrees (== subtrees deeper than...) */
418 while (n < DEPTH) {
419 nr = i_data[DIRECT + n - 1];
420 if (nr) {
421 i_data[DIRECT + n - 1] = 0;
422 mark_inode_dirty(inode);
423 free_branches(inode, &nr, &nr+1, n);
424 }
425 n++;
426 }
427 inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
428 if (IS_SYNC(inode))
429 sysv_sync_inode (inode);
430 else
431 mark_inode_dirty(inode);
432 }
433
sysv_nblocks(struct super_block * s,loff_t size)434 static unsigned sysv_nblocks(struct super_block *s, loff_t size)
435 {
436 struct sysv_sb_info *sbi = SYSV_SB(s);
437 int ptrs_bits = sbi->s_ind_per_block_bits;
438 unsigned blocks, res, direct = DIRECT, i = DEPTH;
439 blocks = (size + s->s_blocksize - 1) >> s->s_blocksize_bits;
440 res = blocks;
441 while (--i && blocks > direct) {
442 blocks = ((blocks - direct - 1) >> ptrs_bits) + 1;
443 res += blocks;
444 direct = 1;
445 }
446 return res;
447 }
448
sysv_getattr(struct mnt_idmap * idmap,const struct path * path,struct kstat * stat,u32 request_mask,unsigned int flags)449 int sysv_getattr(struct mnt_idmap *idmap, const struct path *path,
450 struct kstat *stat, u32 request_mask, unsigned int flags)
451 {
452 struct super_block *s = path->dentry->d_sb;
453 generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry),
454 stat);
455 stat->blocks = (s->s_blocksize / 512) * sysv_nblocks(s, stat->size);
456 stat->blksize = s->s_blocksize;
457 return 0;
458 }
459
sysv_writepages(struct address_space * mapping,struct writeback_control * wbc)460 static int sysv_writepages(struct address_space *mapping,
461 struct writeback_control *wbc)
462 {
463 return mpage_writepages(mapping, wbc, get_block);
464 }
465
sysv_read_folio(struct file * file,struct folio * folio)466 static int sysv_read_folio(struct file *file, struct folio *folio)
467 {
468 return block_read_full_folio(folio, get_block);
469 }
470
sysv_prepare_chunk(struct page * page,loff_t pos,unsigned len)471 int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len)
472 {
473 return __block_write_begin(page, pos, len, get_block);
474 }
475
sysv_write_failed(struct address_space * mapping,loff_t to)476 static void sysv_write_failed(struct address_space *mapping, loff_t to)
477 {
478 struct inode *inode = mapping->host;
479
480 if (to > inode->i_size) {
481 truncate_pagecache(inode, inode->i_size);
482 sysv_truncate(inode);
483 }
484 }
485
sysv_write_begin(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,struct page ** pagep,void ** fsdata)486 static int sysv_write_begin(struct file *file, struct address_space *mapping,
487 loff_t pos, unsigned len,
488 struct page **pagep, void **fsdata)
489 {
490 int ret;
491
492 ret = block_write_begin(mapping, pos, len, pagep, get_block);
493 if (unlikely(ret))
494 sysv_write_failed(mapping, pos + len);
495
496 return ret;
497 }
498
sysv_bmap(struct address_space * mapping,sector_t block)499 static sector_t sysv_bmap(struct address_space *mapping, sector_t block)
500 {
501 return generic_block_bmap(mapping,block,get_block);
502 }
503
504 const struct address_space_operations sysv_aops = {
505 .dirty_folio = block_dirty_folio,
506 .invalidate_folio = block_invalidate_folio,
507 .read_folio = sysv_read_folio,
508 .writepages = sysv_writepages,
509 .write_begin = sysv_write_begin,
510 .write_end = generic_write_end,
511 .migrate_folio = buffer_migrate_folio,
512 .bmap = sysv_bmap
513 };
514