blob: e98f6cd7200cd65fd709bf7ba4339a3e4f977216 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001
2#include <linux/fs.h>
3#include <linux/file.h>
4#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07005#include <linux/namei.h>
6
7struct export_operations export_op_default;
8
9#define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun)
10
11#define dprintk(fmt, args...) do{}while(0)
12
Christoph Hellwige2f99012006-01-18 17:43:52 -080013static struct dentry *
14find_acceptable_alias(struct dentry *result,
15 int (*acceptable)(void *context, struct dentry *dentry),
16 void *context)
17{
18 struct dentry *dentry, *toput = NULL;
19
20 spin_lock(&dcache_lock);
21 list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
22 dget_locked(dentry);
23 spin_unlock(&dcache_lock);
24 if (toput)
25 dput(toput);
26 if (dentry != result && acceptable(context, dentry)) {
27 dput(result);
28 return dentry;
29 }
30 spin_lock(&dcache_lock);
31 toput = dentry;
32 }
33 spin_unlock(&dcache_lock);
34
35 if (toput)
36 dput(toput);
37 return NULL;
38}
39
Linus Torvalds1da177e2005-04-16 15:20:36 -070040/**
41 * find_exported_dentry - helper routine to implement export_operations->decode_fh
42 * @sb: The &super_block identifying the filesystem
43 * @obj: An opaque identifier of the object to be found - passed to
44 * get_inode
45 * @parent: An optional opqaue identifier of the parent of the object.
46 * @acceptable: A function used to test possible &dentries to see if they are
47 * acceptable
48 * @context: A parameter to @acceptable so that it knows on what basis to
49 * judge.
50 *
51 * find_exported_dentry is the central helper routine to enable file systems
52 * to provide the decode_fh() export_operation. It's main task is to take
53 * an &inode, find or create an appropriate &dentry structure, and possibly
54 * splice this into the dcache in the correct place.
55 *
56 * The decode_fh() operation provided by the filesystem should call
57 * find_exported_dentry() with the same parameters that it received except
58 * that instead of the file handle fragment, pointers to opaque identifiers
59 * for the object and optionally its parent are passed. The default decode_fh
60 * routine passes one pointer to the start of the filehandle fragment, and
61 * one 8 bytes into the fragment. It is expected that most filesystems will
62 * take this approach, though the offset to the parent identifier may well be
63 * different.
64 *
65 * find_exported_dentry() will call get_dentry to get an dentry pointer from
66 * the file system. If any &dentry in the d_alias list is acceptable, it will
67 * be returned. Otherwise find_exported_dentry() will attempt to splice a new
68 * &dentry into the dcache using get_name() and get_parent() to find the
69 * appropriate place.
70 */
71
72struct dentry *
73find_exported_dentry(struct super_block *sb, void *obj, void *parent,
74 int (*acceptable)(void *context, struct dentry *de),
75 void *context)
76{
77 struct dentry *result = NULL;
78 struct dentry *target_dir;
79 int err;
80 struct export_operations *nops = sb->s_export_op;
Christoph Hellwige2f99012006-01-18 17:43:52 -080081 struct dentry *alias;
Linus Torvalds1da177e2005-04-16 15:20:36 -070082 int noprogress;
83 char nbuf[NAME_MAX+1];
84
85 /*
86 * Attempt to find the inode.
87 */
88 result = CALL(sb->s_export_op,get_dentry)(sb,obj);
89 err = -ESTALE;
90 if (result == NULL)
91 goto err_out;
92 if (IS_ERR(result)) {
93 err = PTR_ERR(result);
94 goto err_out;
95 }
96 if (S_ISDIR(result->d_inode->i_mode) &&
97 (result->d_flags & DCACHE_DISCONNECTED)) {
98 /* it is an unconnected directory, we must connect it */
99 ;
100 } else {
101 if (acceptable(context, result))
102 return result;
103 if (S_ISDIR(result->d_inode->i_mode)) {
Peter Staubach8c7b3892006-05-20 14:59:56 -0700104 err = -EACCES;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 goto err_result;
106 }
Christoph Hellwige2f99012006-01-18 17:43:52 -0800107
108 alias = find_acceptable_alias(result, acceptable, context);
109 if (alias)
110 return alias;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 }
112
113 /* It's a directory, or we are required to confirm the file's
114 * location in the tree based on the parent information
115 */
116 dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj);
117 if (S_ISDIR(result->d_inode->i_mode))
118 target_dir = dget(result);
119 else {
120 if (parent == NULL)
121 goto err_result;
122
123 target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent);
124 if (IS_ERR(target_dir))
125 err = PTR_ERR(target_dir);
126 if (target_dir == NULL || IS_ERR(target_dir))
127 goto err_result;
128 }
129 /*
130 * Now we need to make sure that target_dir is properly connected.
131 * It may already be, as the flag isn't always updated when connection
132 * happens.
133 * So, we walk up parent links until we find a connected directory,
134 * or we run out of directories. Then we find the parent, find
135 * the name of the child in that parent, and do a lookup.
136 * This should connect the child into the parent
137 * We then repeat.
138 */
139
140 /* it is possible that a confused file system might not let us complete
141 * the path to the root. For example, if get_parent returns a directory
142 * in which we cannot find a name for the child. While this implies a
143 * very sick filesystem we don't want it to cause knfsd to spin. Hence
144 * the noprogress counter. If we go through the loop 10 times (2 is
145 * probably enough) without getting anywhere, we just give up
146 */
147 noprogress= 0;
148 while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
149 struct dentry *pd = target_dir;
150
151 dget(pd);
152 spin_lock(&pd->d_lock);
153 while (!IS_ROOT(pd) &&
154 (pd->d_parent->d_flags&DCACHE_DISCONNECTED)) {
155 struct dentry *parent = pd->d_parent;
156
157 dget(parent);
158 spin_unlock(&pd->d_lock);
159 dput(pd);
160 pd = parent;
161 spin_lock(&pd->d_lock);
162 }
163 spin_unlock(&pd->d_lock);
164
165 if (!IS_ROOT(pd)) {
166 /* must have found a connected parent - great */
167 spin_lock(&pd->d_lock);
168 pd->d_flags &= ~DCACHE_DISCONNECTED;
169 spin_unlock(&pd->d_lock);
170 noprogress = 0;
171 } else if (pd == sb->s_root) {
172 printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
173 spin_lock(&pd->d_lock);
174 pd->d_flags &= ~DCACHE_DISCONNECTED;
175 spin_unlock(&pd->d_lock);
176 noprogress = 0;
177 } else {
178 /* we have hit the top of a disconnected path. Try
179 * to find parent and connect
180 * note: racing with some other process renaming a
181 * directory isn't much of a problem here. If someone
182 * renames the directory, it will end up properly
183 * connected, which is what we want
184 */
185 struct dentry *ppd;
186 struct dentry *npd;
187
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800188 mutex_lock(&pd->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189 ppd = CALL(nops,get_parent)(pd);
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800190 mutex_unlock(&pd->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191
192 if (IS_ERR(ppd)) {
193 err = PTR_ERR(ppd);
194 dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n",
195 pd->d_inode->i_ino, err);
196 dput(pd);
197 break;
198 }
199 dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino);
200 err = CALL(nops,get_name)(ppd, nbuf, pd);
201 if (err) {
202 dput(ppd);
203 dput(pd);
204 if (err == -ENOENT)
205 /* some race between get_parent and
206 * get_name? just try again
207 */
208 continue;
209 break;
210 }
211 dprintk("find_exported_dentry: found name: %s\n", nbuf);
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800212 mutex_lock(&ppd->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213 npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800214 mutex_unlock(&ppd->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700215 if (IS_ERR(npd)) {
216 err = PTR_ERR(npd);
217 dprintk("find_exported_dentry: lookup failed: %d\n", err);
218 dput(ppd);
219 dput(pd);
220 break;
221 }
222 /* we didn't really want npd, we really wanted
223 * a side-effect of the lookup.
224 * hopefully, npd == pd, though it isn't really
225 * a problem if it isn't
226 */
227 if (npd == pd)
228 noprogress = 0;
229 else
230 printk("find_exported_dentry: npd != pd\n");
231 dput(npd);
232 dput(ppd);
233 if (IS_ROOT(pd)) {
234 /* something went wrong, we have to give up */
235 dput(pd);
236 break;
237 }
238 }
239 dput(pd);
240 }
241
242 if (target_dir->d_flags & DCACHE_DISCONNECTED) {
243 /* something went wrong - oh-well */
244 if (!err)
245 err = -ESTALE;
246 goto err_target;
247 }
248 /* if we weren't after a directory, have one more step to go */
249 if (result != target_dir) {
250 struct dentry *nresult;
251 err = CALL(nops,get_name)(target_dir, nbuf, result);
252 if (!err) {
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800253 mutex_lock(&target_dir->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700254 nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800255 mutex_unlock(&target_dir->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256 if (!IS_ERR(nresult)) {
257 if (nresult->d_inode) {
258 dput(result);
259 result = nresult;
260 } else
261 dput(nresult);
262 }
263 }
264 }
265 dput(target_dir);
266 /* now result is properly connected, it is our best bet */
267 if (acceptable(context, result))
268 return result;
Christoph Hellwige2f99012006-01-18 17:43:52 -0800269
270 alias = find_acceptable_alias(result, acceptable, context);
271 if (alias)
272 return alias;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273
274 /* drat - I just cannot find anything acceptable */
275 dput(result);
276 /* It might be justifiable to return ESTALE here,
277 * but the filehandle at-least looks reasonable good
278 * and it just be a permission problem, so returning
279 * -EACCESS is safer
280 */
281 return ERR_PTR(-EACCES);
282
283 err_target:
284 dput(target_dir);
285 err_result:
286 dput(result);
287 err_out:
288 return ERR_PTR(err);
289}
290
291
292
293static struct dentry *get_parent(struct dentry *child)
294{
295 /* get_parent cannot be supported generically, the locking
296 * is too icky.
297 * instead, we just return EACCES. If server reboots or inodes
298 * get flushed, you lose
299 */
300 return ERR_PTR(-EACCES);
301}
302
303
304struct getdents_callback {
305 char *name; /* name that was found. It already points to a
306 buffer NAME_MAX+1 is size */
307 unsigned long ino; /* the inum we are looking for */
308 int found; /* inode matched? */
309 int sequence; /* sequence counter */
310};
311
312/*
313 * A rather strange filldir function to capture
314 * the name matching the specified inode number.
315 */
316static int filldir_one(void * __buf, const char * name, int len,
David Howellsafefdbb2006-10-03 01:13:46 -0700317 loff_t pos, u64 ino, unsigned int d_type)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318{
319 struct getdents_callback *buf = __buf;
320 int result = 0;
321
322 buf->sequence++;
323 if (buf->ino == ino) {
324 memcpy(buf->name, name, len);
325 buf->name[len] = '\0';
326 buf->found = 1;
327 result = -1;
328 }
329 return result;
330}
331
332/**
333 * get_name - default export_operations->get_name function
334 * @dentry: the directory in which to find a name
335 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name
336 * @child: the dentry for the child directory.
337 *
338 * calls readdir on the parent until it finds an entry with
339 * the same inode number as the child, and returns that.
340 */
341static int get_name(struct dentry *dentry, char *name,
342 struct dentry *child)
343{
344 struct inode *dir = dentry->d_inode;
345 int error;
346 struct file *file;
347 struct getdents_callback buffer;
348
349 error = -ENOTDIR;
350 if (!dir || !S_ISDIR(dir->i_mode))
351 goto out;
352 error = -EINVAL;
353 if (!dir->i_fop)
354 goto out;
355 /*
356 * Open the directory ...
357 */
358 file = dentry_open(dget(dentry), NULL, O_RDONLY);
359 error = PTR_ERR(file);
360 if (IS_ERR(file))
361 goto out;
362
363 error = -EINVAL;
364 if (!file->f_op->readdir)
365 goto out_close;
366
367 buffer.name = name;
368 buffer.ino = child->d_inode->i_ino;
369 buffer.found = 0;
370 buffer.sequence = 0;
371 while (1) {
372 int old_seq = buffer.sequence;
373
374 error = vfs_readdir(file, filldir_one, &buffer);
375
376 if (error < 0)
377 break;
378
379 error = 0;
380 if (buffer.found)
381 break;
382 error = -ENOENT;
383 if (old_seq == buffer.sequence)
384 break;
385 }
386
387out_close:
388 fput(file);
389out:
390 return error;
391}
392
393
394static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation)
395{
396
397 /* iget isn't really right if the inode is currently unallocated!!
398 * This should really all be done inside each filesystem
399 *
400 * ext2fs' read_inode has been strengthed to return a bad_inode if
401 * the inode had been deleted.
402 *
403 * Currently we don't know the generation for parent directory, so
404 * a generation of 0 means "accept any"
405 */
406 struct inode *inode;
407 struct dentry *result;
408 if (ino == 0)
409 return ERR_PTR(-ESTALE);
410 inode = iget(sb, ino);
411 if (inode == NULL)
412 return ERR_PTR(-ENOMEM);
413 if (is_bad_inode(inode)
414 || (generation && inode->i_generation != generation)
415 ) {
416 /* we didn't find the right inode.. */
417 dprintk("fh_verify: Inode %lu, Bad count: %d %d or version %u %u\n",
418 inode->i_ino,
419 inode->i_nlink, atomic_read(&inode->i_count),
420 inode->i_generation,
421 generation);
422
423 iput(inode);
424 return ERR_PTR(-ESTALE);
425 }
426 /* now to find a dentry.
427 * If possible, get a well-connected one
428 */
429 result = d_alloc_anon(inode);
430 if (!result) {
431 iput(inode);
432 return ERR_PTR(-ENOMEM);
433 }
434 return result;
435}
436
437
438static struct dentry *get_object(struct super_block *sb, void *vobjp)
439{
440 __u32 *objp = vobjp;
441 unsigned long ino = objp[0];
442 __u32 generation = objp[1];
443
444 return export_iget(sb, ino, generation);
445}
446
447
448/**
449 * export_encode_fh - default export_operations->encode_fh function
450 * @dentry: the dentry to encode
451 * @fh: where to store the file handle fragment
452 * @max_len: maximum length to store there
453 * @connectable: whether to store parent information
454 *
455 * This default encode_fh function assumes that the 32 inode number
456 * is suitable for locating an inode, and that the generation number
457 * can be used to check that it is still valid. It places them in the
458 * filehandle fragment where export_decode_fh expects to find them.
459 */
460static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
461 int connectable)
462{
463 struct inode * inode = dentry->d_inode;
464 int len = *max_len;
465 int type = 1;
466
467 if (len < 2 || (connectable && len < 4))
468 return 255;
469
470 len = 2;
471 fh[0] = inode->i_ino;
472 fh[1] = inode->i_generation;
473 if (connectable && !S_ISDIR(inode->i_mode)) {
474 struct inode *parent;
475
476 spin_lock(&dentry->d_lock);
477 parent = dentry->d_parent->d_inode;
478 fh[2] = parent->i_ino;
479 fh[3] = parent->i_generation;
480 spin_unlock(&dentry->d_lock);
481 len = 4;
482 type = 2;
483 }
484 *max_len = len;
485 return type;
486}
487
488
489/**
490 * export_decode_fh - default export_operations->decode_fh function
491 * @sb: The superblock
492 * @fh: pointer to the file handle fragment
493 * @fh_len: length of file handle fragment
494 * @acceptable: function for testing acceptability of dentrys
495 * @context: context for @acceptable
496 *
497 * This is the default decode_fh() function.
498 * a fileid_type of 1 indicates that the filehandlefragment
499 * just contains an object identifier understood by get_dentry.
500 * a fileid_type of 2 says that there is also a directory
501 * identifier 8 bytes in to the filehandlefragement.
502 */
503static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len,
504 int fileid_type,
505 int (*acceptable)(void *context, struct dentry *de),
506 void *context)
507{
508 __u32 parent[2];
509 parent[0] = parent[1] = 0;
510 if (fh_len < 2 || fileid_type > 2)
511 return NULL;
512 if (fileid_type == 2) {
513 if (fh_len > 2) parent[0] = fh[2];
514 if (fh_len > 3) parent[1] = fh[3];
515 }
516 return find_exported_dentry(sb, fh, parent,
517 acceptable, context);
518}
519
520struct export_operations export_op_default = {
521 .decode_fh = export_decode_fh,
522 .encode_fh = export_encode_fh,
523
524 .get_name = get_name,
525 .get_parent = get_parent,
526 .get_dentry = get_object,
527};
528
529EXPORT_SYMBOL(export_op_default);
530EXPORT_SYMBOL(find_exported_dentry);
531
532MODULE_LICENSE("GPL");