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Linux/fs/sysv/itree.c

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  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 };
504 

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