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Linux/fs/sysv/itree.c

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

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