blob: 166d8ca9eaea065c2e7bb169cba961993c4f0f1f [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001
Christoph Hellwiga5694252007-07-17 04:04:28 -07002#include <linux/exportfs.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003#include <linux/fs.h>
4#include <linux/file.h>
5#include <linux/module.h>
Christoph Hellwigd37065c2007-07-17 04:04:30 -07006#include <linux/mount.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07007#include <linux/namei.h>
8
Linus Torvalds1da177e2005-04-16 15:20:36 -07009#define dprintk(fmt, args...) do{}while(0)
10
Christoph Hellwig10f11c32007-07-17 04:04:31 -070011
12static int get_name(struct dentry *dentry, char *name,
13 struct dentry *child);
14
15
16static struct dentry *exportfs_get_dentry(struct super_block *sb, void *obj)
17{
18 struct dentry *result = ERR_PTR(-ESTALE);
19
20 if (sb->s_export_op->get_dentry) {
21 result = sb->s_export_op->get_dentry(sb, obj);
22 if (!result)
23 result = ERR_PTR(-ESTALE);
24 }
25
26 return result;
27}
28
29static int exportfs_get_name(struct dentry *dir, char *name,
30 struct dentry *child)
31{
32 struct export_operations *nop = dir->d_sb->s_export_op;
33
34 if (nop->get_name)
35 return nop->get_name(dir, name, child);
36 else
37 return get_name(dir, name, child);
38}
39
Christoph Hellwigfb66a192007-07-17 04:04:32 -070040/*
41 * Check if the dentry or any of it's aliases is acceptable.
42 */
Christoph Hellwige2f99012006-01-18 17:43:52 -080043static struct dentry *
44find_acceptable_alias(struct dentry *result,
45 int (*acceptable)(void *context, struct dentry *dentry),
46 void *context)
47{
48 struct dentry *dentry, *toput = NULL;
49
Christoph Hellwigfb66a192007-07-17 04:04:32 -070050 if (acceptable(context, result))
51 return result;
52
Christoph Hellwige2f99012006-01-18 17:43:52 -080053 spin_lock(&dcache_lock);
54 list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
55 dget_locked(dentry);
56 spin_unlock(&dcache_lock);
57 if (toput)
58 dput(toput);
59 if (dentry != result && acceptable(context, dentry)) {
60 dput(result);
61 return dentry;
62 }
63 spin_lock(&dcache_lock);
64 toput = dentry;
65 }
66 spin_unlock(&dcache_lock);
67
68 if (toput)
69 dput(toput);
70 return NULL;
71}
72
Christoph Hellwigdd90b502007-07-17 04:04:32 -070073/*
74 * Find root of a disconnected subtree and return a reference to it.
75 */
76static struct dentry *
77find_disconnected_root(struct dentry *dentry)
78{
79 dget(dentry);
80 spin_lock(&dentry->d_lock);
81 while (!IS_ROOT(dentry) &&
82 (dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) {
83 struct dentry *parent = dentry->d_parent;
84 dget(parent);
85 spin_unlock(&dentry->d_lock);
86 dput(dentry);
87 dentry = parent;
88 spin_lock(&dentry->d_lock);
89 }
90 spin_unlock(&dentry->d_lock);
91 return dentry;
92}
93
Linus Torvalds1da177e2005-04-16 15:20:36 -070094/**
95 * find_exported_dentry - helper routine to implement export_operations->decode_fh
96 * @sb: The &super_block identifying the filesystem
97 * @obj: An opaque identifier of the object to be found - passed to
98 * get_inode
99 * @parent: An optional opqaue identifier of the parent of the object.
100 * @acceptable: A function used to test possible &dentries to see if they are
101 * acceptable
102 * @context: A parameter to @acceptable so that it knows on what basis to
103 * judge.
104 *
105 * find_exported_dentry is the central helper routine to enable file systems
106 * to provide the decode_fh() export_operation. It's main task is to take
107 * an &inode, find or create an appropriate &dentry structure, and possibly
108 * splice this into the dcache in the correct place.
109 *
110 * The decode_fh() operation provided by the filesystem should call
111 * find_exported_dentry() with the same parameters that it received except
112 * that instead of the file handle fragment, pointers to opaque identifiers
113 * for the object and optionally its parent are passed. The default decode_fh
114 * routine passes one pointer to the start of the filehandle fragment, and
115 * one 8 bytes into the fragment. It is expected that most filesystems will
116 * take this approach, though the offset to the parent identifier may well be
117 * different.
118 *
119 * find_exported_dentry() will call get_dentry to get an dentry pointer from
120 * the file system. If any &dentry in the d_alias list is acceptable, it will
121 * be returned. Otherwise find_exported_dentry() will attempt to splice a new
122 * &dentry into the dcache using get_name() and get_parent() to find the
123 * appropriate place.
124 */
125
126struct dentry *
127find_exported_dentry(struct super_block *sb, void *obj, void *parent,
128 int (*acceptable)(void *context, struct dentry *de),
129 void *context)
130{
131 struct dentry *result = NULL;
132 struct dentry *target_dir;
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700133 int err = -ESTALE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134 struct export_operations *nops = sb->s_export_op;
Christoph Hellwige2f99012006-01-18 17:43:52 -0800135 struct dentry *alias;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136 int noprogress;
137 char nbuf[NAME_MAX+1];
138
139 /*
140 * Attempt to find the inode.
141 */
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700142 result = exportfs_get_dentry(sb, obj);
143 if (IS_ERR(result))
144 return result;
145
Christoph Hellwigd7dd6182007-07-17 04:04:31 -0700146 if (S_ISDIR(result->d_inode->i_mode)) {
147 if (!(result->d_flags & DCACHE_DISCONNECTED)) {
148 if (acceptable(context, result))
149 return result;
Peter Staubach8c7b3892006-05-20 14:59:56 -0700150 err = -EACCES;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151 goto err_result;
152 }
Christoph Hellwige2f99012006-01-18 17:43:52 -0800153
Christoph Hellwigd7dd6182007-07-17 04:04:31 -0700154 target_dir = dget(result);
155 } else {
Christoph Hellwige2f99012006-01-18 17:43:52 -0800156 alias = find_acceptable_alias(result, acceptable, context);
157 if (alias)
158 return alias;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160 if (parent == NULL)
161 goto err_result;
162
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700163 target_dir = exportfs_get_dentry(sb,parent);
164 if (IS_ERR(target_dir)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165 err = PTR_ERR(target_dir);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166 goto err_result;
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700167 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168 }
Christoph Hellwigd7dd6182007-07-17 04:04:31 -0700169
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 /*
171 * Now we need to make sure that target_dir is properly connected.
172 * It may already be, as the flag isn't always updated when connection
173 * happens.
174 * So, we walk up parent links until we find a connected directory,
175 * or we run out of directories. Then we find the parent, find
176 * the name of the child in that parent, and do a lookup.
177 * This should connect the child into the parent
178 * We then repeat.
179 */
180
181 /* it is possible that a confused file system might not let us complete
182 * the path to the root. For example, if get_parent returns a directory
183 * in which we cannot find a name for the child. While this implies a
184 * very sick filesystem we don't want it to cause knfsd to spin. Hence
185 * the noprogress counter. If we go through the loop 10 times (2 is
186 * probably enough) without getting anywhere, we just give up
187 */
Christoph Hellwigdd90b502007-07-17 04:04:32 -0700188 noprogress = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189 while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
Christoph Hellwigdd90b502007-07-17 04:04:32 -0700190 struct dentry *pd = find_disconnected_root(target_dir);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191
192 if (!IS_ROOT(pd)) {
193 /* must have found a connected parent - great */
194 spin_lock(&pd->d_lock);
195 pd->d_flags &= ~DCACHE_DISCONNECTED;
196 spin_unlock(&pd->d_lock);
197 noprogress = 0;
198 } else if (pd == sb->s_root) {
199 printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
200 spin_lock(&pd->d_lock);
201 pd->d_flags &= ~DCACHE_DISCONNECTED;
202 spin_unlock(&pd->d_lock);
203 noprogress = 0;
204 } else {
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700205 /*
206 * We have hit the top of a disconnected path, try to
207 * find parent and connect.
208 *
209 * Racing with some other process renaming a directory
210 * isn't much of a problem here. If someone renames
211 * the directory, it will end up properly connected,
212 * which is what we want
213 *
214 * Getting the parent can't be supported generically,
215 * the locking is too icky.
216 *
217 * Instead we just return EACCES. If server reboots
218 * or inodes get flushed, you lose
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219 */
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700220 struct dentry *ppd = ERR_PTR(-EACCES);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700221 struct dentry *npd;
222
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800223 mutex_lock(&pd->d_inode->i_mutex);
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700224 if (nops->get_parent)
225 ppd = nops->get_parent(pd);
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800226 mutex_unlock(&pd->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227
228 if (IS_ERR(ppd)) {
229 err = PTR_ERR(ppd);
230 dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n",
231 pd->d_inode->i_ino, err);
232 dput(pd);
233 break;
234 }
235 dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino);
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700236 err = exportfs_get_name(ppd, nbuf, pd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700237 if (err) {
238 dput(ppd);
239 dput(pd);
240 if (err == -ENOENT)
241 /* some race between get_parent and
242 * get_name? just try again
243 */
244 continue;
245 break;
246 }
247 dprintk("find_exported_dentry: found name: %s\n", nbuf);
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800248 mutex_lock(&ppd->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249 npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800250 mutex_unlock(&ppd->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251 if (IS_ERR(npd)) {
252 err = PTR_ERR(npd);
253 dprintk("find_exported_dentry: lookup failed: %d\n", err);
254 dput(ppd);
255 dput(pd);
256 break;
257 }
258 /* we didn't really want npd, we really wanted
259 * a side-effect of the lookup.
260 * hopefully, npd == pd, though it isn't really
261 * a problem if it isn't
262 */
263 if (npd == pd)
264 noprogress = 0;
265 else
266 printk("find_exported_dentry: npd != pd\n");
267 dput(npd);
268 dput(ppd);
269 if (IS_ROOT(pd)) {
270 /* something went wrong, we have to give up */
271 dput(pd);
272 break;
273 }
274 }
275 dput(pd);
276 }
277
278 if (target_dir->d_flags & DCACHE_DISCONNECTED) {
279 /* something went wrong - oh-well */
280 if (!err)
281 err = -ESTALE;
282 goto err_target;
283 }
284 /* if we weren't after a directory, have one more step to go */
285 if (result != target_dir) {
286 struct dentry *nresult;
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700287 err = exportfs_get_name(target_dir, nbuf, result);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700288 if (!err) {
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800289 mutex_lock(&target_dir->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290 nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
Jes Sorensen1b1dcc12006-01-09 15:59:24 -0800291 mutex_unlock(&target_dir->d_inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292 if (!IS_ERR(nresult)) {
293 if (nresult->d_inode) {
294 dput(result);
295 result = nresult;
296 } else
297 dput(nresult);
298 }
299 }
300 }
301 dput(target_dir);
Christoph Hellwige2f99012006-01-18 17:43:52 -0800302
303 alias = find_acceptable_alias(result, acceptable, context);
304 if (alias)
305 return alias;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306
307 /* drat - I just cannot find anything acceptable */
308 dput(result);
309 /* It might be justifiable to return ESTALE here,
310 * but the filehandle at-least looks reasonable good
311 * and it just be a permission problem, so returning
312 * -EACCESS is safer
313 */
314 return ERR_PTR(-EACCES);
315
316 err_target:
317 dput(target_dir);
318 err_result:
319 dput(result);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 return ERR_PTR(err);
321}
322
Linus Torvalds1da177e2005-04-16 15:20:36 -0700323struct getdents_callback {
324 char *name; /* name that was found. It already points to a
325 buffer NAME_MAX+1 is size */
326 unsigned long ino; /* the inum we are looking for */
327 int found; /* inode matched? */
328 int sequence; /* sequence counter */
329};
330
331/*
332 * A rather strange filldir function to capture
333 * the name matching the specified inode number.
334 */
335static int filldir_one(void * __buf, const char * name, int len,
David Howellsafefdbb2006-10-03 01:13:46 -0700336 loff_t pos, u64 ino, unsigned int d_type)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700337{
338 struct getdents_callback *buf = __buf;
339 int result = 0;
340
341 buf->sequence++;
342 if (buf->ino == ino) {
343 memcpy(buf->name, name, len);
344 buf->name[len] = '\0';
345 buf->found = 1;
346 result = -1;
347 }
348 return result;
349}
350
351/**
352 * get_name - default export_operations->get_name function
353 * @dentry: the directory in which to find a name
354 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name
355 * @child: the dentry for the child directory.
356 *
357 * calls readdir on the parent until it finds an entry with
358 * the same inode number as the child, and returns that.
359 */
360static int get_name(struct dentry *dentry, char *name,
361 struct dentry *child)
362{
363 struct inode *dir = dentry->d_inode;
364 int error;
365 struct file *file;
366 struct getdents_callback buffer;
367
368 error = -ENOTDIR;
369 if (!dir || !S_ISDIR(dir->i_mode))
370 goto out;
371 error = -EINVAL;
372 if (!dir->i_fop)
373 goto out;
374 /*
375 * Open the directory ...
376 */
377 file = dentry_open(dget(dentry), NULL, O_RDONLY);
378 error = PTR_ERR(file);
379 if (IS_ERR(file))
380 goto out;
381
382 error = -EINVAL;
383 if (!file->f_op->readdir)
384 goto out_close;
385
386 buffer.name = name;
387 buffer.ino = child->d_inode->i_ino;
388 buffer.found = 0;
389 buffer.sequence = 0;
390 while (1) {
391 int old_seq = buffer.sequence;
392
393 error = vfs_readdir(file, filldir_one, &buffer);
394
395 if (error < 0)
396 break;
397
398 error = 0;
399 if (buffer.found)
400 break;
401 error = -ENOENT;
402 if (old_seq == buffer.sequence)
403 break;
404 }
405
406out_close:
407 fput(file);
408out:
409 return error;
410}
411
Linus Torvalds1da177e2005-04-16 15:20:36 -0700412/**
413 * export_encode_fh - default export_operations->encode_fh function
414 * @dentry: the dentry to encode
415 * @fh: where to store the file handle fragment
416 * @max_len: maximum length to store there
417 * @connectable: whether to store parent information
418 *
419 * This default encode_fh function assumes that the 32 inode number
420 * is suitable for locating an inode, and that the generation number
421 * can be used to check that it is still valid. It places them in the
422 * filehandle fragment where export_decode_fh expects to find them.
423 */
424static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
425 int connectable)
426{
427 struct inode * inode = dentry->d_inode;
428 int len = *max_len;
429 int type = 1;
430
431 if (len < 2 || (connectable && len < 4))
432 return 255;
433
434 len = 2;
435 fh[0] = inode->i_ino;
436 fh[1] = inode->i_generation;
437 if (connectable && !S_ISDIR(inode->i_mode)) {
438 struct inode *parent;
439
440 spin_lock(&dentry->d_lock);
441 parent = dentry->d_parent->d_inode;
442 fh[2] = parent->i_ino;
443 fh[3] = parent->i_generation;
444 spin_unlock(&dentry->d_lock);
445 len = 4;
446 type = 2;
447 }
448 *max_len = len;
449 return type;
450}
451
452
453/**
454 * export_decode_fh - default export_operations->decode_fh function
455 * @sb: The superblock
456 * @fh: pointer to the file handle fragment
457 * @fh_len: length of file handle fragment
458 * @acceptable: function for testing acceptability of dentrys
459 * @context: context for @acceptable
460 *
461 * This is the default decode_fh() function.
462 * a fileid_type of 1 indicates that the filehandlefragment
463 * just contains an object identifier understood by get_dentry.
464 * a fileid_type of 2 says that there is also a directory
465 * identifier 8 bytes in to the filehandlefragement.
466 */
467static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len,
468 int fileid_type,
469 int (*acceptable)(void *context, struct dentry *de),
470 void *context)
471{
472 __u32 parent[2];
473 parent[0] = parent[1] = 0;
474 if (fh_len < 2 || fileid_type > 2)
475 return NULL;
476 if (fileid_type == 2) {
477 if (fh_len > 2) parent[0] = fh[2];
478 if (fh_len > 3) parent[1] = fh[3];
479 }
480 return find_exported_dentry(sb, fh, parent,
481 acceptable, context);
482}
483
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700484int exportfs_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
485 int connectable)
486{
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700487 struct export_operations *nop = dentry->d_sb->s_export_op;
488 int error;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700489
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700490 if (nop->encode_fh)
491 error = nop->encode_fh(dentry, fh, max_len, connectable);
492 else
493 error = export_encode_fh(dentry, fh, max_len, connectable);
494
495 return error;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700496}
497EXPORT_SYMBOL_GPL(exportfs_encode_fh);
498
499struct dentry *exportfs_decode_fh(struct vfsmount *mnt, __u32 *fh, int fh_len,
500 int fileid_type, int (*acceptable)(void *, struct dentry *),
501 void *context)
502{
503 struct export_operations *nop = mnt->mnt_sb->s_export_op;
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700504 struct dentry *result;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700505
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700506 if (nop->decode_fh) {
507 result = nop->decode_fh(mnt->mnt_sb, fh, fh_len, fileid_type,
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700508 acceptable, context);
Christoph Hellwig10f11c32007-07-17 04:04:31 -0700509 } else {
510 result = export_decode_fh(mnt->mnt_sb, fh, fh_len, fileid_type,
511 acceptable, context);
512 }
513
514 return result;
Christoph Hellwigd37065c2007-07-17 04:04:30 -0700515}
516EXPORT_SYMBOL_GPL(exportfs_decode_fh);
517
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518EXPORT_SYMBOL(find_exported_dentry);
519
520MODULE_LICENSE("GPL");