blob: c49d6254379aa5ecc4c91e0af4bdcd62ac7059fa [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>
5#include <linux/smp_lock.h>
6#include <linux/namei.h>
7
8struct export_operations export_op_default;
9
10#define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun)
11
12#define dprintk(fmt, args...) do{}while(0)
13
14/**
15 * find_exported_dentry - helper routine to implement export_operations->decode_fh
16 * @sb: The &super_block identifying the filesystem
17 * @obj: An opaque identifier of the object to be found - passed to
18 * get_inode
19 * @parent: An optional opqaue identifier of the parent of the object.
20 * @acceptable: A function used to test possible &dentries to see if they are
21 * acceptable
22 * @context: A parameter to @acceptable so that it knows on what basis to
23 * judge.
24 *
25 * find_exported_dentry is the central helper routine to enable file systems
26 * to provide the decode_fh() export_operation. It's main task is to take
27 * an &inode, find or create an appropriate &dentry structure, and possibly
28 * splice this into the dcache in the correct place.
29 *
30 * The decode_fh() operation provided by the filesystem should call
31 * find_exported_dentry() with the same parameters that it received except
32 * that instead of the file handle fragment, pointers to opaque identifiers
33 * for the object and optionally its parent are passed. The default decode_fh
34 * routine passes one pointer to the start of the filehandle fragment, and
35 * one 8 bytes into the fragment. It is expected that most filesystems will
36 * take this approach, though the offset to the parent identifier may well be
37 * different.
38 *
39 * find_exported_dentry() will call get_dentry to get an dentry pointer from
40 * the file system. If any &dentry in the d_alias list is acceptable, it will
41 * be returned. Otherwise find_exported_dentry() will attempt to splice a new
42 * &dentry into the dcache using get_name() and get_parent() to find the
43 * appropriate place.
44 */
45
46struct dentry *
47find_exported_dentry(struct super_block *sb, void *obj, void *parent,
48 int (*acceptable)(void *context, struct dentry *de),
49 void *context)
50{
51 struct dentry *result = NULL;
52 struct dentry *target_dir;
53 int err;
54 struct export_operations *nops = sb->s_export_op;
55 struct list_head *le, *head;
56 struct dentry *toput = NULL;
57 int noprogress;
58 char nbuf[NAME_MAX+1];
59
60 /*
61 * Attempt to find the inode.
62 */
63 result = CALL(sb->s_export_op,get_dentry)(sb,obj);
64 err = -ESTALE;
65 if (result == NULL)
66 goto err_out;
67 if (IS_ERR(result)) {
68 err = PTR_ERR(result);
69 goto err_out;
70 }
71 if (S_ISDIR(result->d_inode->i_mode) &&
72 (result->d_flags & DCACHE_DISCONNECTED)) {
73 /* it is an unconnected directory, we must connect it */
74 ;
75 } else {
76 if (acceptable(context, result))
77 return result;
78 if (S_ISDIR(result->d_inode->i_mode)) {
79 /* there is no other dentry, so fail */
80 goto err_result;
81 }
82 /* try any other aliases */
83 spin_lock(&dcache_lock);
84 head = &result->d_inode->i_dentry;
85 list_for_each(le, head) {
86 struct dentry *dentry = list_entry(le, struct dentry, d_alias);
87 dget_locked(dentry);
88 spin_unlock(&dcache_lock);
89 if (toput)
90 dput(toput);
91 toput = NULL;
92 if (dentry != result &&
93 acceptable(context, dentry)) {
94 dput(result);
95 return dentry;
96 }
97 spin_lock(&dcache_lock);
98 toput = dentry;
99 }
100 spin_unlock(&dcache_lock);
101 if (toput)
102 dput(toput);
103 }
104
105 /* It's a directory, or we are required to confirm the file's
106 * location in the tree based on the parent information
107 */
108 dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj);
109 if (S_ISDIR(result->d_inode->i_mode))
110 target_dir = dget(result);
111 else {
112 if (parent == NULL)
113 goto err_result;
114
115 target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent);
116 if (IS_ERR(target_dir))
117 err = PTR_ERR(target_dir);
118 if (target_dir == NULL || IS_ERR(target_dir))
119 goto err_result;
120 }
121 /*
122 * Now we need to make sure that target_dir is properly connected.
123 * It may already be, as the flag isn't always updated when connection
124 * happens.
125 * So, we walk up parent links until we find a connected directory,
126 * or we run out of directories. Then we find the parent, find
127 * the name of the child in that parent, and do a lookup.
128 * This should connect the child into the parent
129 * We then repeat.
130 */
131
132 /* it is possible that a confused file system might not let us complete
133 * the path to the root. For example, if get_parent returns a directory
134 * in which we cannot find a name for the child. While this implies a
135 * very sick filesystem we don't want it to cause knfsd to spin. Hence
136 * the noprogress counter. If we go through the loop 10 times (2 is
137 * probably enough) without getting anywhere, we just give up
138 */
139 noprogress= 0;
140 while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
141 struct dentry *pd = target_dir;
142
143 dget(pd);
144 spin_lock(&pd->d_lock);
145 while (!IS_ROOT(pd) &&
146 (pd->d_parent->d_flags&DCACHE_DISCONNECTED)) {
147 struct dentry *parent = pd->d_parent;
148
149 dget(parent);
150 spin_unlock(&pd->d_lock);
151 dput(pd);
152 pd = parent;
153 spin_lock(&pd->d_lock);
154 }
155 spin_unlock(&pd->d_lock);
156
157 if (!IS_ROOT(pd)) {
158 /* must have found a connected parent - great */
159 spin_lock(&pd->d_lock);
160 pd->d_flags &= ~DCACHE_DISCONNECTED;
161 spin_unlock(&pd->d_lock);
162 noprogress = 0;
163 } else if (pd == sb->s_root) {
164 printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
165 spin_lock(&pd->d_lock);
166 pd->d_flags &= ~DCACHE_DISCONNECTED;
167 spin_unlock(&pd->d_lock);
168 noprogress = 0;
169 } else {
170 /* we have hit the top of a disconnected path. Try
171 * to find parent and connect
172 * note: racing with some other process renaming a
173 * directory isn't much of a problem here. If someone
174 * renames the directory, it will end up properly
175 * connected, which is what we want
176 */
177 struct dentry *ppd;
178 struct dentry *npd;
179
180 down(&pd->d_inode->i_sem);
181 ppd = CALL(nops,get_parent)(pd);
182 up(&pd->d_inode->i_sem);
183
184 if (IS_ERR(ppd)) {
185 err = PTR_ERR(ppd);
186 dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n",
187 pd->d_inode->i_ino, err);
188 dput(pd);
189 break;
190 }
191 dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino);
192 err = CALL(nops,get_name)(ppd, nbuf, pd);
193 if (err) {
194 dput(ppd);
195 dput(pd);
196 if (err == -ENOENT)
197 /* some race between get_parent and
198 * get_name? just try again
199 */
200 continue;
201 break;
202 }
203 dprintk("find_exported_dentry: found name: %s\n", nbuf);
204 down(&ppd->d_inode->i_sem);
205 npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
206 up(&ppd->d_inode->i_sem);
207 if (IS_ERR(npd)) {
208 err = PTR_ERR(npd);
209 dprintk("find_exported_dentry: lookup failed: %d\n", err);
210 dput(ppd);
211 dput(pd);
212 break;
213 }
214 /* we didn't really want npd, we really wanted
215 * a side-effect of the lookup.
216 * hopefully, npd == pd, though it isn't really
217 * a problem if it isn't
218 */
219 if (npd == pd)
220 noprogress = 0;
221 else
222 printk("find_exported_dentry: npd != pd\n");
223 dput(npd);
224 dput(ppd);
225 if (IS_ROOT(pd)) {
226 /* something went wrong, we have to give up */
227 dput(pd);
228 break;
229 }
230 }
231 dput(pd);
232 }
233
234 if (target_dir->d_flags & DCACHE_DISCONNECTED) {
235 /* something went wrong - oh-well */
236 if (!err)
237 err = -ESTALE;
238 goto err_target;
239 }
240 /* if we weren't after a directory, have one more step to go */
241 if (result != target_dir) {
242 struct dentry *nresult;
243 err = CALL(nops,get_name)(target_dir, nbuf, result);
244 if (!err) {
245 down(&target_dir->d_inode->i_sem);
246 nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
247 up(&target_dir->d_inode->i_sem);
248 if (!IS_ERR(nresult)) {
249 if (nresult->d_inode) {
250 dput(result);
251 result = nresult;
252 } else
253 dput(nresult);
254 }
255 }
256 }
257 dput(target_dir);
258 /* now result is properly connected, it is our best bet */
259 if (acceptable(context, result))
260 return result;
261 /* one last try of the aliases.. */
262 spin_lock(&dcache_lock);
263 toput = NULL;
264 head = &result->d_inode->i_dentry;
265 list_for_each(le, head) {
266 struct dentry *dentry = list_entry(le, struct dentry, d_alias);
267 dget_locked(dentry);
268 spin_unlock(&dcache_lock);
269 if (toput) dput(toput);
270 if (dentry != result &&
271 acceptable(context, dentry)) {
272 dput(result);
273 return dentry;
274 }
275 spin_lock(&dcache_lock);
276 toput = dentry;
277 }
278 spin_unlock(&dcache_lock);
279 if (toput)
280 dput(toput);
281
282 /* drat - I just cannot find anything acceptable */
283 dput(result);
284 /* It might be justifiable to return ESTALE here,
285 * but the filehandle at-least looks reasonable good
286 * and it just be a permission problem, so returning
287 * -EACCESS is safer
288 */
289 return ERR_PTR(-EACCES);
290
291 err_target:
292 dput(target_dir);
293 err_result:
294 dput(result);
295 err_out:
296 return ERR_PTR(err);
297}
298
299
300
301static struct dentry *get_parent(struct dentry *child)
302{
303 /* get_parent cannot be supported generically, the locking
304 * is too icky.
305 * instead, we just return EACCES. If server reboots or inodes
306 * get flushed, you lose
307 */
308 return ERR_PTR(-EACCES);
309}
310
311
312struct getdents_callback {
313 char *name; /* name that was found. It already points to a
314 buffer NAME_MAX+1 is size */
315 unsigned long ino; /* the inum we are looking for */
316 int found; /* inode matched? */
317 int sequence; /* sequence counter */
318};
319
320/*
321 * A rather strange filldir function to capture
322 * the name matching the specified inode number.
323 */
324static int filldir_one(void * __buf, const char * name, int len,
325 loff_t pos, ino_t ino, unsigned int d_type)
326{
327 struct getdents_callback *buf = __buf;
328 int result = 0;
329
330 buf->sequence++;
331 if (buf->ino == ino) {
332 memcpy(buf->name, name, len);
333 buf->name[len] = '\0';
334 buf->found = 1;
335 result = -1;
336 }
337 return result;
338}
339
340/**
341 * get_name - default export_operations->get_name function
342 * @dentry: the directory in which to find a name
343 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name
344 * @child: the dentry for the child directory.
345 *
346 * calls readdir on the parent until it finds an entry with
347 * the same inode number as the child, and returns that.
348 */
349static int get_name(struct dentry *dentry, char *name,
350 struct dentry *child)
351{
352 struct inode *dir = dentry->d_inode;
353 int error;
354 struct file *file;
355 struct getdents_callback buffer;
356
357 error = -ENOTDIR;
358 if (!dir || !S_ISDIR(dir->i_mode))
359 goto out;
360 error = -EINVAL;
361 if (!dir->i_fop)
362 goto out;
363 /*
364 * Open the directory ...
365 */
366 file = dentry_open(dget(dentry), NULL, O_RDONLY);
367 error = PTR_ERR(file);
368 if (IS_ERR(file))
369 goto out;
370
371 error = -EINVAL;
372 if (!file->f_op->readdir)
373 goto out_close;
374
375 buffer.name = name;
376 buffer.ino = child->d_inode->i_ino;
377 buffer.found = 0;
378 buffer.sequence = 0;
379 while (1) {
380 int old_seq = buffer.sequence;
381
382 error = vfs_readdir(file, filldir_one, &buffer);
383
384 if (error < 0)
385 break;
386
387 error = 0;
388 if (buffer.found)
389 break;
390 error = -ENOENT;
391 if (old_seq == buffer.sequence)
392 break;
393 }
394
395out_close:
396 fput(file);
397out:
398 return error;
399}
400
401
402static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation)
403{
404
405 /* iget isn't really right if the inode is currently unallocated!!
406 * This should really all be done inside each filesystem
407 *
408 * ext2fs' read_inode has been strengthed to return a bad_inode if
409 * the inode had been deleted.
410 *
411 * Currently we don't know the generation for parent directory, so
412 * a generation of 0 means "accept any"
413 */
414 struct inode *inode;
415 struct dentry *result;
416 if (ino == 0)
417 return ERR_PTR(-ESTALE);
418 inode = iget(sb, ino);
419 if (inode == NULL)
420 return ERR_PTR(-ENOMEM);
421 if (is_bad_inode(inode)
422 || (generation && inode->i_generation != generation)
423 ) {
424 /* we didn't find the right inode.. */
425 dprintk("fh_verify: Inode %lu, Bad count: %d %d or version %u %u\n",
426 inode->i_ino,
427 inode->i_nlink, atomic_read(&inode->i_count),
428 inode->i_generation,
429 generation);
430
431 iput(inode);
432 return ERR_PTR(-ESTALE);
433 }
434 /* now to find a dentry.
435 * If possible, get a well-connected one
436 */
437 result = d_alloc_anon(inode);
438 if (!result) {
439 iput(inode);
440 return ERR_PTR(-ENOMEM);
441 }
442 return result;
443}
444
445
446static struct dentry *get_object(struct super_block *sb, void *vobjp)
447{
448 __u32 *objp = vobjp;
449 unsigned long ino = objp[0];
450 __u32 generation = objp[1];
451
452 return export_iget(sb, ino, generation);
453}
454
455
456/**
457 * export_encode_fh - default export_operations->encode_fh function
458 * @dentry: the dentry to encode
459 * @fh: where to store the file handle fragment
460 * @max_len: maximum length to store there
461 * @connectable: whether to store parent information
462 *
463 * This default encode_fh function assumes that the 32 inode number
464 * is suitable for locating an inode, and that the generation number
465 * can be used to check that it is still valid. It places them in the
466 * filehandle fragment where export_decode_fh expects to find them.
467 */
468static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
469 int connectable)
470{
471 struct inode * inode = dentry->d_inode;
472 int len = *max_len;
473 int type = 1;
474
475 if (len < 2 || (connectable && len < 4))
476 return 255;
477
478 len = 2;
479 fh[0] = inode->i_ino;
480 fh[1] = inode->i_generation;
481 if (connectable && !S_ISDIR(inode->i_mode)) {
482 struct inode *parent;
483
484 spin_lock(&dentry->d_lock);
485 parent = dentry->d_parent->d_inode;
486 fh[2] = parent->i_ino;
487 fh[3] = parent->i_generation;
488 spin_unlock(&dentry->d_lock);
489 len = 4;
490 type = 2;
491 }
492 *max_len = len;
493 return type;
494}
495
496
497/**
498 * export_decode_fh - default export_operations->decode_fh function
499 * @sb: The superblock
500 * @fh: pointer to the file handle fragment
501 * @fh_len: length of file handle fragment
502 * @acceptable: function for testing acceptability of dentrys
503 * @context: context for @acceptable
504 *
505 * This is the default decode_fh() function.
506 * a fileid_type of 1 indicates that the filehandlefragment
507 * just contains an object identifier understood by get_dentry.
508 * a fileid_type of 2 says that there is also a directory
509 * identifier 8 bytes in to the filehandlefragement.
510 */
511static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len,
512 int fileid_type,
513 int (*acceptable)(void *context, struct dentry *de),
514 void *context)
515{
516 __u32 parent[2];
517 parent[0] = parent[1] = 0;
518 if (fh_len < 2 || fileid_type > 2)
519 return NULL;
520 if (fileid_type == 2) {
521 if (fh_len > 2) parent[0] = fh[2];
522 if (fh_len > 3) parent[1] = fh[3];
523 }
524 return find_exported_dentry(sb, fh, parent,
525 acceptable, context);
526}
527
528struct export_operations export_op_default = {
529 .decode_fh = export_decode_fh,
530 .encode_fh = export_encode_fh,
531
532 .get_name = get_name,
533 .get_parent = get_parent,
534 .get_dentry = get_object,
535};
536
537EXPORT_SYMBOL(export_op_default);
538EXPORT_SYMBOL(find_exported_dentry);
539
540MODULE_LICENSE("GPL");