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TOMOYO Linux Cross Reference
Linux/fs/omfs/dir.c

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  1 /*
  2  * OMFS (as used by RIO Karma) directory operations.
  3  * Copyright (C) 2005 Bob Copeland <me@bobcopeland.com>
  4  * Released under GPL v2.
  5  */
  6 
  7 #include <linux/fs.h>
  8 #include <linux/ctype.h>
  9 #include <linux/buffer_head.h>
 10 #include "omfs.h"
 11 
 12 static int omfs_hash(const char *name, int namelen, int mod)
 13 {
 14         int i, hash = 0;
 15         for (i = 0; i < namelen; i++)
 16                 hash ^= tolower(name[i]) << (i % 24);
 17         return hash % mod;
 18 }
 19 
 20 /*
 21  * Finds the bucket for a given name and reads the containing block;
 22  * *ofs is set to the offset of the first list entry.
 23  */
 24 static struct buffer_head *omfs_get_bucket(struct inode *dir,
 25                 const char *name, int namelen, int *ofs)
 26 {
 27         int nbuckets = (dir->i_size - OMFS_DIR_START)/8;
 28         int bucket = omfs_hash(name, namelen, nbuckets);
 29 
 30         *ofs = OMFS_DIR_START + bucket * 8;
 31         return omfs_bread(dir->i_sb, dir->i_ino);
 32 }
 33 
 34 static struct buffer_head *omfs_scan_list(struct inode *dir, u64 block,
 35                                 const char *name, int namelen,
 36                                 u64 *prev_block)
 37 {
 38         struct buffer_head *bh;
 39         struct omfs_inode *oi;
 40         int err = -ENOENT;
 41         *prev_block = ~0;
 42 
 43         while (block != ~0) {
 44                 bh = omfs_bread(dir->i_sb, block);
 45                 if (!bh) {
 46                         err = -EIO;
 47                         goto err;
 48                 }
 49 
 50                 oi = (struct omfs_inode *) bh->b_data;
 51                 if (omfs_is_bad(OMFS_SB(dir->i_sb), &oi->i_head, block)) {
 52                         brelse(bh);
 53                         goto err;
 54                 }
 55 
 56                 if (strncmp(oi->i_name, name, namelen) == 0)
 57                         return bh;
 58 
 59                 *prev_block = block;
 60                 block = be64_to_cpu(oi->i_sibling);
 61                 brelse(bh);
 62         }
 63 err:
 64         return ERR_PTR(err);
 65 }
 66 
 67 static struct buffer_head *omfs_find_entry(struct inode *dir,
 68                                            const char *name, int namelen)
 69 {
 70         struct buffer_head *bh;
 71         int ofs;
 72         u64 block, dummy;
 73 
 74         bh = omfs_get_bucket(dir, name, namelen, &ofs);
 75         if (!bh)
 76                 return ERR_PTR(-EIO);
 77 
 78         block = be64_to_cpu(*((__be64 *) &bh->b_data[ofs]));
 79         brelse(bh);
 80 
 81         return omfs_scan_list(dir, block, name, namelen, &dummy);
 82 }
 83 
 84 int omfs_make_empty(struct inode *inode, struct super_block *sb)
 85 {
 86         struct omfs_sb_info *sbi = OMFS_SB(sb);
 87         struct buffer_head *bh;
 88         struct omfs_inode *oi;
 89 
 90         bh = omfs_bread(sb, inode->i_ino);
 91         if (!bh)
 92                 return -ENOMEM;
 93 
 94         memset(bh->b_data, 0, sizeof(struct omfs_inode));
 95 
 96         if (S_ISDIR(inode->i_mode)) {
 97                 memset(&bh->b_data[OMFS_DIR_START], 0xff,
 98                         sbi->s_sys_blocksize - OMFS_DIR_START);
 99         } else
100                 omfs_make_empty_table(bh, OMFS_EXTENT_START);
101 
102         oi = (struct omfs_inode *) bh->b_data;
103         oi->i_head.h_self = cpu_to_be64(inode->i_ino);
104         oi->i_sibling = ~cpu_to_be64(0ULL);
105 
106         mark_buffer_dirty(bh);
107         brelse(bh);
108         return 0;
109 }
110 
111 static int omfs_add_link(struct dentry *dentry, struct inode *inode)
112 {
113         struct inode *dir = d_inode(dentry->d_parent);
114         const char *name = dentry->d_name.name;
115         int namelen = dentry->d_name.len;
116         struct omfs_inode *oi;
117         struct buffer_head *bh;
118         u64 block;
119         __be64 *entry;
120         int ofs;
121 
122         /* just prepend to head of queue in proper bucket */
123         bh = omfs_get_bucket(dir, name, namelen, &ofs);
124         if (!bh)
125                 goto out;
126 
127         entry = (__be64 *) &bh->b_data[ofs];
128         block = be64_to_cpu(*entry);
129         *entry = cpu_to_be64(inode->i_ino);
130         mark_buffer_dirty(bh);
131         brelse(bh);
132 
133         /* now set the sibling and parent pointers on the new inode */
134         bh = omfs_bread(dir->i_sb, inode->i_ino);
135         if (!bh)
136                 goto out;
137 
138         oi = (struct omfs_inode *) bh->b_data;
139         memcpy(oi->i_name, name, namelen);
140         memset(oi->i_name + namelen, 0, OMFS_NAMELEN - namelen);
141         oi->i_sibling = cpu_to_be64(block);
142         oi->i_parent = cpu_to_be64(dir->i_ino);
143         mark_buffer_dirty(bh);
144         brelse(bh);
145 
146         dir->i_ctime = CURRENT_TIME_SEC;
147 
148         /* mark affected inodes dirty to rebuild checksums */
149         mark_inode_dirty(dir);
150         mark_inode_dirty(inode);
151         return 0;
152 out:
153         return -ENOMEM;
154 }
155 
156 static int omfs_delete_entry(struct dentry *dentry)
157 {
158         struct inode *dir = d_inode(dentry->d_parent);
159         struct inode *dirty;
160         const char *name = dentry->d_name.name;
161         int namelen = dentry->d_name.len;
162         struct omfs_inode *oi;
163         struct buffer_head *bh, *bh2;
164         __be64 *entry, next;
165         u64 block, prev;
166         int ofs;
167         int err = -ENOMEM;
168 
169         /* delete the proper node in the bucket's linked list */
170         bh = omfs_get_bucket(dir, name, namelen, &ofs);
171         if (!bh)
172                 goto out;
173 
174         entry = (__be64 *) &bh->b_data[ofs];
175         block = be64_to_cpu(*entry);
176 
177         bh2 = omfs_scan_list(dir, block, name, namelen, &prev);
178         if (IS_ERR(bh2)) {
179                 err = PTR_ERR(bh2);
180                 goto out_free_bh;
181         }
182 
183         oi = (struct omfs_inode *) bh2->b_data;
184         next = oi->i_sibling;
185         brelse(bh2);
186 
187         if (prev != ~0) {
188                 /* found in middle of list, get list ptr */
189                 brelse(bh);
190                 bh = omfs_bread(dir->i_sb, prev);
191                 if (!bh)
192                         goto out;
193 
194                 oi = (struct omfs_inode *) bh->b_data;
195                 entry = &oi->i_sibling;
196         }
197 
198         *entry = next;
199         mark_buffer_dirty(bh);
200 
201         if (prev != ~0) {
202                 dirty = omfs_iget(dir->i_sb, prev);
203                 if (!IS_ERR(dirty)) {
204                         mark_inode_dirty(dirty);
205                         iput(dirty);
206                 }
207         }
208 
209         err = 0;
210 out_free_bh:
211         brelse(bh);
212 out:
213         return err;
214 }
215 
216 static int omfs_dir_is_empty(struct inode *inode)
217 {
218         int nbuckets = (inode->i_size - OMFS_DIR_START) / 8;
219         struct buffer_head *bh;
220         u64 *ptr;
221         int i;
222 
223         bh = omfs_bread(inode->i_sb, inode->i_ino);
224 
225         if (!bh)
226                 return 0;
227 
228         ptr = (u64 *) &bh->b_data[OMFS_DIR_START];
229 
230         for (i = 0; i < nbuckets; i++, ptr++)
231                 if (*ptr != ~0)
232                         break;
233 
234         brelse(bh);
235         return *ptr != ~0;
236 }
237 
238 static int omfs_remove(struct inode *dir, struct dentry *dentry)
239 {
240         struct inode *inode = d_inode(dentry);
241         int ret;
242 
243 
244         if (S_ISDIR(inode->i_mode) &&
245             !omfs_dir_is_empty(inode))
246                 return -ENOTEMPTY;
247 
248         ret = omfs_delete_entry(dentry);
249         if (ret)
250                 return ret;
251         
252         clear_nlink(inode);
253         mark_inode_dirty(inode);
254         mark_inode_dirty(dir);
255         return 0;
256 }
257 
258 static int omfs_add_node(struct inode *dir, struct dentry *dentry, umode_t mode)
259 {
260         int err;
261         struct inode *inode = omfs_new_inode(dir, mode);
262 
263         if (IS_ERR(inode))
264                 return PTR_ERR(inode);
265 
266         err = omfs_make_empty(inode, dir->i_sb);
267         if (err)
268                 goto out_free_inode;
269 
270         err = omfs_add_link(dentry, inode);
271         if (err)
272                 goto out_free_inode;
273 
274         d_instantiate(dentry, inode);
275         return 0;
276 
277 out_free_inode:
278         iput(inode);
279         return err;
280 }
281 
282 static int omfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
283 {
284         return omfs_add_node(dir, dentry, mode | S_IFDIR);
285 }
286 
287 static int omfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
288                 bool excl)
289 {
290         return omfs_add_node(dir, dentry, mode | S_IFREG);
291 }
292 
293 static struct dentry *omfs_lookup(struct inode *dir, struct dentry *dentry,
294                                   unsigned int flags)
295 {
296         struct buffer_head *bh;
297         struct inode *inode = NULL;
298 
299         if (dentry->d_name.len > OMFS_NAMELEN)
300                 return ERR_PTR(-ENAMETOOLONG);
301 
302         bh = omfs_find_entry(dir, dentry->d_name.name, dentry->d_name.len);
303         if (!IS_ERR(bh)) {
304                 struct omfs_inode *oi = (struct omfs_inode *)bh->b_data;
305                 ino_t ino = be64_to_cpu(oi->i_head.h_self);
306                 brelse(bh);
307                 inode = omfs_iget(dir->i_sb, ino);
308                 if (IS_ERR(inode))
309                         return ERR_CAST(inode);
310         }
311         d_add(dentry, inode);
312         return NULL;
313 }
314 
315 /* sanity check block's self pointer */
316 int omfs_is_bad(struct omfs_sb_info *sbi, struct omfs_header *header,
317         u64 fsblock)
318 {
319         int is_bad;
320         u64 ino = be64_to_cpu(header->h_self);
321         is_bad = ((ino != fsblock) || (ino < sbi->s_root_ino) ||
322                 (ino > sbi->s_num_blocks));
323 
324         if (is_bad)
325                 printk(KERN_WARNING "omfs: bad hash chain detected\n");
326 
327         return is_bad;
328 }
329 
330 static bool omfs_fill_chain(struct inode *dir, struct dir_context *ctx,
331                 u64 fsblock, int hindex)
332 {
333         /* follow chain in this bucket */
334         while (fsblock != ~0) {
335                 struct buffer_head *bh = omfs_bread(dir->i_sb, fsblock);
336                 struct omfs_inode *oi;
337                 u64 self;
338                 unsigned char d_type;
339 
340                 if (!bh)
341                         return true;
342 
343                 oi = (struct omfs_inode *) bh->b_data;
344                 if (omfs_is_bad(OMFS_SB(dir->i_sb), &oi->i_head, fsblock)) {
345                         brelse(bh);
346                         return true;
347                 }
348 
349                 self = fsblock;
350                 fsblock = be64_to_cpu(oi->i_sibling);
351 
352                 /* skip visited nodes */
353                 if (hindex) {
354                         hindex--;
355                         brelse(bh);
356                         continue;
357                 }
358 
359                 d_type = (oi->i_type == OMFS_DIR) ? DT_DIR : DT_REG;
360 
361                 if (!dir_emit(ctx, oi->i_name,
362                               strnlen(oi->i_name, OMFS_NAMELEN),
363                               self, d_type)) {
364                         brelse(bh);
365                         return false;
366                 }
367                 brelse(bh);
368                 ctx->pos++;
369         }
370         return true;
371 }
372 
373 static int omfs_rename(struct inode *old_dir, struct dentry *old_dentry,
374                 struct inode *new_dir, struct dentry *new_dentry)
375 {
376         struct inode *new_inode = d_inode(new_dentry);
377         struct inode *old_inode = d_inode(old_dentry);
378         int err;
379 
380         if (new_inode) {
381                 /* overwriting existing file/dir */
382                 err = omfs_remove(new_dir, new_dentry);
383                 if (err)
384                         goto out;
385         }
386 
387         /* since omfs locates files by name, we need to unlink _before_
388          * adding the new link or we won't find the old one */
389         err = omfs_delete_entry(old_dentry);
390         if (err)
391                 goto out;
392 
393         mark_inode_dirty(old_dir);
394         err = omfs_add_link(new_dentry, old_inode);
395         if (err)
396                 goto out;
397 
398         old_inode->i_ctime = CURRENT_TIME_SEC;
399         mark_inode_dirty(old_inode);
400 out:
401         return err;
402 }
403 
404 static int omfs_readdir(struct file *file, struct dir_context *ctx)
405 {
406         struct inode *dir = file_inode(file);
407         struct buffer_head *bh;
408         __be64 *p;
409         unsigned int hchain, hindex;
410         int nbuckets;
411 
412         if (ctx->pos >> 32)
413                 return -EINVAL;
414 
415         if (ctx->pos < 1 << 20) {
416                 if (!dir_emit_dots(file, ctx))
417                         return 0;
418                 ctx->pos = 1 << 20;
419         }
420 
421         nbuckets = (dir->i_size - OMFS_DIR_START) / 8;
422 
423         /* high 12 bits store bucket + 1 and low 20 bits store hash index */
424         hchain = (ctx->pos >> 20) - 1;
425         hindex = ctx->pos & 0xfffff;
426 
427         bh = omfs_bread(dir->i_sb, dir->i_ino);
428         if (!bh)
429                 return -EINVAL;
430 
431         p = (__be64 *)(bh->b_data + OMFS_DIR_START) + hchain;
432 
433         for (; hchain < nbuckets; hchain++) {
434                 __u64 fsblock = be64_to_cpu(*p++);
435                 if (!omfs_fill_chain(dir, ctx, fsblock, hindex))
436                         break;
437                 hindex = 0;
438                 ctx->pos = (hchain+2) << 20;
439         }
440         brelse(bh);
441         return 0;
442 }
443 
444 const struct inode_operations omfs_dir_inops = {
445         .lookup = omfs_lookup,
446         .mkdir = omfs_mkdir,
447         .rename = omfs_rename,
448         .create = omfs_create,
449         .unlink = omfs_remove,
450         .rmdir = omfs_remove,
451 };
452 
453 const struct file_operations omfs_dir_operations = {
454         .read = generic_read_dir,
455         .iterate = omfs_readdir,
456         .llseek = generic_file_llseek,
457 };
458 

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