GNU Linux-libre 4.19.211-gnu1
[releases.git] / fs / sysv / itree.c
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/string.h>
12 #include "sysv.h"
13
14 enum {DIRECT = 10, DEPTH = 4};  /* Have triple indirect */
15
16 static inline void dirty_indirect(struct buffer_head *bh, struct inode *inode)
17 {
18         mark_buffer_dirty_inode(bh, inode);
19         if (IS_SYNC(inode))
20                 sync_dirty_buffer(bh);
21 }
22
23 static int block_to_path(struct inode *inode, long block, int offsets[DEPTH])
24 {
25         struct super_block *sb = inode->i_sb;
26         struct sysv_sb_info *sbi = SYSV_SB(sb);
27         int ptrs_bits = sbi->s_ind_per_block_bits;
28         unsigned long   indirect_blocks = sbi->s_ind_per_block,
29                         double_blocks = sbi->s_ind_per_block_2;
30         int n = 0;
31
32         if (block < 0) {
33                 printk("sysv_block_map: block < 0\n");
34         } else if (block < DIRECT) {
35                 offsets[n++] = block;
36         } else if ( (block -= DIRECT) < indirect_blocks) {
37                 offsets[n++] = DIRECT;
38                 offsets[n++] = block;
39         } else if ((block -= indirect_blocks) < double_blocks) {
40                 offsets[n++] = DIRECT+1;
41                 offsets[n++] = block >> ptrs_bits;
42                 offsets[n++] = block & (indirect_blocks - 1);
43         } else if (((block -= double_blocks) >> (ptrs_bits * 2)) < indirect_blocks) {
44                 offsets[n++] = DIRECT+2;
45                 offsets[n++] = block >> (ptrs_bits * 2);
46                 offsets[n++] = (block >> ptrs_bits) & (indirect_blocks - 1);
47                 offsets[n++] = block & (indirect_blocks - 1);
48         } else {
49                 /* nothing */;
50         }
51         return n;
52 }
53
54 static inline int block_to_cpu(struct sysv_sb_info *sbi, sysv_zone_t nr)
55 {
56         return sbi->s_block_base + fs32_to_cpu(sbi, nr);
57 }
58
59 typedef struct {
60         sysv_zone_t     *p;
61         sysv_zone_t     key;
62         struct buffer_head *bh;
63 } Indirect;
64
65 static DEFINE_RWLOCK(pointers_lock);
66
67 static inline void add_chain(Indirect *p, struct buffer_head *bh, sysv_zone_t *v)
68 {
69         p->key = *(p->p = v);
70         p->bh = bh;
71 }
72
73 static inline int verify_chain(Indirect *from, Indirect *to)
74 {
75         while (from <= to && from->key == *from->p)
76                 from++;
77         return (from > to);
78 }
79
80 static inline sysv_zone_t *block_end(struct buffer_head *bh)
81 {
82         return (sysv_zone_t*)((char*)bh->b_data + bh->b_size);
83 }
84
85 /*
86  * Requires read_lock(&pointers_lock) or write_lock(&pointers_lock)
87  */
88 static Indirect *get_branch(struct inode *inode,
89                             int depth,
90                             int offsets[],
91                             Indirect chain[],
92                             int *err)
93 {
94         struct super_block *sb = inode->i_sb;
95         Indirect *p = chain;
96         struct buffer_head *bh;
97
98         *err = 0;
99         add_chain(chain, NULL, SYSV_I(inode)->i_data + *offsets);
100         if (!p->key)
101                 goto no_block;
102         while (--depth) {
103                 int block = block_to_cpu(SYSV_SB(sb), p->key);
104                 bh = sb_bread(sb, block);
105                 if (!bh)
106                         goto failure;
107                 if (!verify_chain(chain, p))
108                         goto changed;
109                 add_chain(++p, bh, (sysv_zone_t*)bh->b_data + *++offsets);
110                 if (!p->key)
111                         goto no_block;
112         }
113         return NULL;
114
115 changed:
116         brelse(bh);
117         *err = -EAGAIN;
118         goto no_block;
119 failure:
120         *err = -EIO;
121 no_block:
122         return p;
123 }
124
125 static int alloc_branch(struct inode *inode,
126                         int num,
127                         int *offsets,
128                         Indirect *branch)
129 {
130         int blocksize = inode->i_sb->s_blocksize;
131         int n = 0;
132         int i;
133
134         branch[0].key = sysv_new_block(inode->i_sb);
135         if (branch[0].key) for (n = 1; n < num; n++) {
136                 struct buffer_head *bh;
137                 int parent;
138                 /* Allocate the next block */
139                 branch[n].key = sysv_new_block(inode->i_sb);
140                 if (!branch[n].key)
141                         break;
142                 /*
143                  * Get buffer_head for parent block, zero it out and set 
144                  * the pointer to new one, then send parent to disk.
145                  */
146                 parent = block_to_cpu(SYSV_SB(inode->i_sb), branch[n-1].key);
147                 bh = sb_getblk(inode->i_sb, parent);
148                 lock_buffer(bh);
149                 memset(bh->b_data, 0, blocksize);
150                 branch[n].bh = bh;
151                 branch[n].p = (sysv_zone_t*) bh->b_data + offsets[n];
152                 *branch[n].p = branch[n].key;
153                 set_buffer_uptodate(bh);
154                 unlock_buffer(bh);
155                 dirty_indirect(bh, inode);
156         }
157         if (n == num)
158                 return 0;
159
160         /* Allocation failed, free what we already allocated */
161         for (i = 1; i < n; i++)
162                 bforget(branch[i].bh);
163         for (i = 0; i < n; i++)
164                 sysv_free_block(inode->i_sb, branch[i].key);
165         return -ENOSPC;
166 }
167
168 static inline int splice_branch(struct inode *inode,
169                                 Indirect chain[],
170                                 Indirect *where,
171                                 int num)
172 {
173         int i;
174
175         /* Verify that place we are splicing to is still there and vacant */
176         write_lock(&pointers_lock);
177         if (!verify_chain(chain, where-1) || *where->p)
178                 goto changed;
179         *where->p = where->key;
180         write_unlock(&pointers_lock);
181
182         inode->i_ctime = current_time(inode);
183
184         /* had we spliced it onto indirect block? */
185         if (where->bh)
186                 dirty_indirect(where->bh, inode);
187
188         if (IS_SYNC(inode))
189                 sysv_sync_inode(inode);
190         else
191                 mark_inode_dirty(inode);
192         return 0;
193
194 changed:
195         write_unlock(&pointers_lock);
196         for (i = 1; i < num; i++)
197                 bforget(where[i].bh);
198         for (i = 0; i < num; i++)
199                 sysv_free_block(inode->i_sb, where[i].key);
200         return -EAGAIN;
201 }
202
203 static int get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create)
204 {
205         int err = -EIO;
206         int offsets[DEPTH];
207         Indirect chain[DEPTH];
208         struct super_block *sb = inode->i_sb;
209         Indirect *partial;
210         int left;
211         int depth = block_to_path(inode, iblock, offsets);
212
213         if (depth == 0)
214                 goto out;
215
216 reread:
217         read_lock(&pointers_lock);
218         partial = get_branch(inode, depth, offsets, chain, &err);
219         read_unlock(&pointers_lock);
220
221         /* Simplest case - block found, no allocation needed */
222         if (!partial) {
223 got_it:
224                 map_bh(bh_result, sb, block_to_cpu(SYSV_SB(sb),
225                                         chain[depth-1].key));
226                 /* Clean up and exit */
227                 partial = chain+depth-1; /* the whole chain */
228                 goto cleanup;
229         }
230
231         /* Next simple case - plain lookup or failed read of indirect block */
232         if (!create || err == -EIO) {
233 cleanup:
234                 while (partial > chain) {
235                         brelse(partial->bh);
236                         partial--;
237                 }
238 out:
239                 return err;
240         }
241
242         /*
243          * Indirect block might be removed by truncate while we were
244          * reading it. Handling of that case (forget what we've got and
245          * reread) is taken out of the main path.
246          */
247         if (err == -EAGAIN)
248                 goto changed;
249
250         left = (chain + depth) - partial;
251         err = alloc_branch(inode, left, offsets+(partial-chain), partial);
252         if (err)
253                 goto cleanup;
254
255         if (splice_branch(inode, chain, partial, left) < 0)
256                 goto changed;
257
258         set_buffer_new(bh_result);
259         goto got_it;
260
261 changed:
262         while (partial > chain) {
263                 brelse(partial->bh);
264                 partial--;
265         }
266         goto reread;
267 }
268
269 static inline int all_zeroes(sysv_zone_t *p, sysv_zone_t *q)
270 {
271         while (p < q)
272                 if (*p++)
273                         return 0;
274         return 1;
275 }
276
277 static Indirect *find_shared(struct inode *inode,
278                                 int depth,
279                                 int offsets[],
280                                 Indirect chain[],
281                                 sysv_zone_t *top)
282 {
283         Indirect *partial, *p;
284         int k, err;
285
286         *top = 0;
287         for (k = depth; k > 1 && !offsets[k-1]; k--)
288                 ;
289
290         write_lock(&pointers_lock);
291         partial = get_branch(inode, k, offsets, chain, &err);
292         if (!partial)
293                 partial = chain + k-1;
294         /*
295          * If the branch acquired continuation since we've looked at it -
296          * fine, it should all survive and (new) top doesn't belong to us.
297          */
298         if (!partial->key && *partial->p) {
299                 write_unlock(&pointers_lock);
300                 goto no_top;
301         }
302         for (p=partial; p>chain && all_zeroes((sysv_zone_t*)p->bh->b_data,p->p); p--)
303                 ;
304         /*
305          * OK, we've found the last block that must survive. The rest of our
306          * branch should be detached before unlocking. However, if that rest
307          * of branch is all ours and does not grow immediately from the inode
308          * it's easier to cheat and just decrement partial->p.
309          */
310         if (p == chain + k - 1 && p > chain) {
311                 p->p--;
312         } else {
313                 *top = *p->p;
314                 *p->p = 0;
315         }
316         write_unlock(&pointers_lock);
317
318         while (partial > p) {
319                 brelse(partial->bh);
320                 partial--;
321         }
322 no_top:
323         return partial;
324 }
325
326 static inline void free_data(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q)
327 {
328         for ( ; p < q ; p++) {
329                 sysv_zone_t nr = *p;
330                 if (nr) {
331                         *p = 0;
332                         sysv_free_block(inode->i_sb, nr);
333                         mark_inode_dirty(inode);
334                 }
335         }
336 }
337
338 static void free_branches(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q, int depth)
339 {
340         struct buffer_head * bh;
341         struct super_block *sb = inode->i_sb;
342
343         if (depth--) {
344                 for ( ; p < q ; p++) {
345                         int block;
346                         sysv_zone_t nr = *p;
347                         if (!nr)
348                                 continue;
349                         *p = 0;
350                         block = block_to_cpu(SYSV_SB(sb), nr);
351                         bh = sb_bread(sb, block);
352                         if (!bh)
353                                 continue;
354                         free_branches(inode, (sysv_zone_t*)bh->b_data,
355                                         block_end(bh), depth);
356                         bforget(bh);
357                         sysv_free_block(sb, nr);
358                         mark_inode_dirty(inode);
359                 }
360         } else
361                 free_data(inode, p, q);
362 }
363
364 void sysv_truncate (struct inode * inode)
365 {
366         sysv_zone_t *i_data = SYSV_I(inode)->i_data;
367         int offsets[DEPTH];
368         Indirect chain[DEPTH];
369         Indirect *partial;
370         sysv_zone_t nr = 0;
371         int n;
372         long iblock;
373         unsigned blocksize;
374
375         if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
376             S_ISLNK(inode->i_mode)))
377                 return;
378
379         blocksize = inode->i_sb->s_blocksize;
380         iblock = (inode->i_size + blocksize-1)
381                                         >> inode->i_sb->s_blocksize_bits;
382
383         block_truncate_page(inode->i_mapping, inode->i_size, get_block);
384
385         n = block_to_path(inode, iblock, offsets);
386         if (n == 0)
387                 return;
388
389         if (n == 1) {
390                 free_data(inode, i_data+offsets[0], i_data + DIRECT);
391                 goto do_indirects;
392         }
393
394         partial = find_shared(inode, n, offsets, chain, &nr);
395         /* Kill the top of shared branch (already detached) */
396         if (nr) {
397                 if (partial == chain)
398                         mark_inode_dirty(inode);
399                 else
400                         dirty_indirect(partial->bh, inode);
401                 free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
402         }
403         /* Clear the ends of indirect blocks on the shared branch */
404         while (partial > chain) {
405                 free_branches(inode, partial->p + 1, block_end(partial->bh),
406                                 (chain+n-1) - partial);
407                 dirty_indirect(partial->bh, inode);
408                 brelse (partial->bh);
409                 partial--;
410         }
411 do_indirects:
412         /* Kill the remaining (whole) subtrees (== subtrees deeper than...) */
413         while (n < DEPTH) {
414                 nr = i_data[DIRECT + n - 1];
415                 if (nr) {
416                         i_data[DIRECT + n - 1] = 0;
417                         mark_inode_dirty(inode);
418                         free_branches(inode, &nr, &nr+1, n);
419                 }
420                 n++;
421         }
422         inode->i_mtime = inode->i_ctime = current_time(inode);
423         if (IS_SYNC(inode))
424                 sysv_sync_inode (inode);
425         else
426                 mark_inode_dirty(inode);
427 }
428
429 static unsigned sysv_nblocks(struct super_block *s, loff_t size)
430 {
431         struct sysv_sb_info *sbi = SYSV_SB(s);
432         int ptrs_bits = sbi->s_ind_per_block_bits;
433         unsigned blocks, res, direct = DIRECT, i = DEPTH;
434         blocks = (size + s->s_blocksize - 1) >> s->s_blocksize_bits;
435         res = blocks;
436         while (--i && blocks > direct) {
437                 blocks = ((blocks - direct - 1) >> ptrs_bits) + 1;
438                 res += blocks;
439                 direct = 1;
440         }
441         return blocks;
442 }
443
444 int sysv_getattr(const struct path *path, struct kstat *stat,
445                  u32 request_mask, unsigned int flags)
446 {
447         struct super_block *s = path->dentry->d_sb;
448         generic_fillattr(d_inode(path->dentry), stat);
449         stat->blocks = (s->s_blocksize / 512) * sysv_nblocks(s, stat->size);
450         stat->blksize = s->s_blocksize;
451         return 0;
452 }
453
454 static int sysv_writepage(struct page *page, struct writeback_control *wbc)
455 {
456         return block_write_full_page(page,get_block,wbc);
457 }
458
459 static int sysv_readpage(struct file *file, struct page *page)
460 {
461         return block_read_full_page(page,get_block);
462 }
463
464 int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len)
465 {
466         return __block_write_begin(page, pos, len, get_block);
467 }
468
469 static void sysv_write_failed(struct address_space *mapping, loff_t to)
470 {
471         struct inode *inode = mapping->host;
472
473         if (to > inode->i_size) {
474                 truncate_pagecache(inode, inode->i_size);
475                 sysv_truncate(inode);
476         }
477 }
478
479 static int sysv_write_begin(struct file *file, struct address_space *mapping,
480                         loff_t pos, unsigned len, unsigned flags,
481                         struct page **pagep, void **fsdata)
482 {
483         int ret;
484
485         ret = block_write_begin(mapping, pos, len, flags, pagep, get_block);
486         if (unlikely(ret))
487                 sysv_write_failed(mapping, pos + len);
488
489         return ret;
490 }
491
492 static sector_t sysv_bmap(struct address_space *mapping, sector_t block)
493 {
494         return generic_block_bmap(mapping,block,get_block);
495 }
496
497 const struct address_space_operations sysv_aops = {
498         .readpage = sysv_readpage,
499         .writepage = sysv_writepage,
500         .write_begin = sysv_write_begin,
501         .write_end = generic_write_end,
502         .bmap = sysv_bmap
503 };