ia64/linux-2.6.18-xen.hg

view fs/exportfs/expfs.c @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
children
line source
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>
8 struct export_operations export_op_default;
10 #define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun)
12 #define dprintk(fmt, args...) do{}while(0)
14 static struct dentry *
15 find_acceptable_alias(struct dentry *result,
16 int (*acceptable)(void *context, struct dentry *dentry),
17 void *context)
18 {
19 struct dentry *dentry, *toput = NULL;
21 spin_lock(&dcache_lock);
22 list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
23 dget_locked(dentry);
24 spin_unlock(&dcache_lock);
25 if (toput)
26 dput(toput);
27 if (dentry != result && acceptable(context, dentry)) {
28 dput(result);
29 return dentry;
30 }
31 spin_lock(&dcache_lock);
32 toput = dentry;
33 }
34 spin_unlock(&dcache_lock);
36 if (toput)
37 dput(toput);
38 return NULL;
39 }
41 /**
42 * find_exported_dentry - helper routine to implement export_operations->decode_fh
43 * @sb: The &super_block identifying the filesystem
44 * @obj: An opaque identifier of the object to be found - passed to
45 * get_inode
46 * @parent: An optional opqaue identifier of the parent of the object.
47 * @acceptable: A function used to test possible &dentries to see if they are
48 * acceptable
49 * @context: A parameter to @acceptable so that it knows on what basis to
50 * judge.
51 *
52 * find_exported_dentry is the central helper routine to enable file systems
53 * to provide the decode_fh() export_operation. It's main task is to take
54 * an &inode, find or create an appropriate &dentry structure, and possibly
55 * splice this into the dcache in the correct place.
56 *
57 * The decode_fh() operation provided by the filesystem should call
58 * find_exported_dentry() with the same parameters that it received except
59 * that instead of the file handle fragment, pointers to opaque identifiers
60 * for the object and optionally its parent are passed. The default decode_fh
61 * routine passes one pointer to the start of the filehandle fragment, and
62 * one 8 bytes into the fragment. It is expected that most filesystems will
63 * take this approach, though the offset to the parent identifier may well be
64 * different.
65 *
66 * find_exported_dentry() will call get_dentry to get an dentry pointer from
67 * the file system. If any &dentry in the d_alias list is acceptable, it will
68 * be returned. Otherwise find_exported_dentry() will attempt to splice a new
69 * &dentry into the dcache using get_name() and get_parent() to find the
70 * appropriate place.
71 */
73 struct dentry *
74 find_exported_dentry(struct super_block *sb, void *obj, void *parent,
75 int (*acceptable)(void *context, struct dentry *de),
76 void *context)
77 {
78 struct dentry *result = NULL;
79 struct dentry *target_dir;
80 int err;
81 struct export_operations *nops = sb->s_export_op;
82 struct dentry *alias;
83 int noprogress;
84 char nbuf[NAME_MAX+1];
86 /*
87 * Attempt to find the inode.
88 */
89 result = CALL(sb->s_export_op,get_dentry)(sb,obj);
90 err = -ESTALE;
91 if (result == NULL)
92 goto err_out;
93 if (IS_ERR(result)) {
94 err = PTR_ERR(result);
95 goto err_out;
96 }
97 if (S_ISDIR(result->d_inode->i_mode) &&
98 (result->d_flags & DCACHE_DISCONNECTED)) {
99 /* it is an unconnected directory, we must connect it */
100 ;
101 } else {
102 if (acceptable(context, result))
103 return result;
104 if (S_ISDIR(result->d_inode->i_mode)) {
105 err = -EACCES;
106 goto err_result;
107 }
109 alias = find_acceptable_alias(result, acceptable, context);
110 if (alias)
111 return alias;
112 }
114 /* It's a directory, or we are required to confirm the file's
115 * location in the tree based on the parent information
116 */
117 dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj);
118 if (S_ISDIR(result->d_inode->i_mode))
119 target_dir = dget(result);
120 else {
121 if (parent == NULL)
122 goto err_result;
124 target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent);
125 if (IS_ERR(target_dir))
126 err = PTR_ERR(target_dir);
127 if (target_dir == NULL || IS_ERR(target_dir))
128 goto err_result;
129 }
130 /*
131 * Now we need to make sure that target_dir is properly connected.
132 * It may already be, as the flag isn't always updated when connection
133 * happens.
134 * So, we walk up parent links until we find a connected directory,
135 * or we run out of directories. Then we find the parent, find
136 * the name of the child in that parent, and do a lookup.
137 * This should connect the child into the parent
138 * We then repeat.
139 */
141 /* it is possible that a confused file system might not let us complete
142 * the path to the root. For example, if get_parent returns a directory
143 * in which we cannot find a name for the child. While this implies a
144 * very sick filesystem we don't want it to cause knfsd to spin. Hence
145 * the noprogress counter. If we go through the loop 10 times (2 is
146 * probably enough) without getting anywhere, we just give up
147 */
148 noprogress= 0;
149 while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
150 struct dentry *pd = target_dir;
152 dget(pd);
153 spin_lock(&pd->d_lock);
154 while (!IS_ROOT(pd) &&
155 (pd->d_parent->d_flags&DCACHE_DISCONNECTED)) {
156 struct dentry *parent = pd->d_parent;
158 dget(parent);
159 spin_unlock(&pd->d_lock);
160 dput(pd);
161 pd = parent;
162 spin_lock(&pd->d_lock);
163 }
164 spin_unlock(&pd->d_lock);
166 if (!IS_ROOT(pd)) {
167 /* must have found a connected parent - great */
168 spin_lock(&pd->d_lock);
169 pd->d_flags &= ~DCACHE_DISCONNECTED;
170 spin_unlock(&pd->d_lock);
171 noprogress = 0;
172 } else if (pd == sb->s_root) {
173 printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
174 spin_lock(&pd->d_lock);
175 pd->d_flags &= ~DCACHE_DISCONNECTED;
176 spin_unlock(&pd->d_lock);
177 noprogress = 0;
178 } else {
179 /* we have hit the top of a disconnected path. Try
180 * to find parent and connect
181 * note: racing with some other process renaming a
182 * directory isn't much of a problem here. If someone
183 * renames the directory, it will end up properly
184 * connected, which is what we want
185 */
186 struct dentry *ppd;
187 struct dentry *npd;
189 mutex_lock(&pd->d_inode->i_mutex);
190 ppd = CALL(nops,get_parent)(pd);
191 mutex_unlock(&pd->d_inode->i_mutex);
193 if (IS_ERR(ppd)) {
194 err = PTR_ERR(ppd);
195 dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n",
196 pd->d_inode->i_ino, err);
197 dput(pd);
198 break;
199 }
200 dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino);
201 err = CALL(nops,get_name)(ppd, nbuf, pd);
202 if (err) {
203 dput(ppd);
204 dput(pd);
205 if (err == -ENOENT)
206 /* some race between get_parent and
207 * get_name? just try again
208 */
209 continue;
210 break;
211 }
212 dprintk("find_exported_dentry: found name: %s\n", nbuf);
213 mutex_lock(&ppd->d_inode->i_mutex);
214 npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
215 mutex_unlock(&ppd->d_inode->i_mutex);
216 if (IS_ERR(npd)) {
217 err = PTR_ERR(npd);
218 dprintk("find_exported_dentry: lookup failed: %d\n", err);
219 dput(ppd);
220 dput(pd);
221 break;
222 }
223 /* we didn't really want npd, we really wanted
224 * a side-effect of the lookup.
225 * hopefully, npd == pd, though it isn't really
226 * a problem if it isn't
227 */
228 if (npd == pd)
229 noprogress = 0;
230 else
231 printk("find_exported_dentry: npd != pd\n");
232 dput(npd);
233 dput(ppd);
234 if (IS_ROOT(pd)) {
235 /* something went wrong, we have to give up */
236 dput(pd);
237 break;
238 }
239 }
240 dput(pd);
241 }
243 if (target_dir->d_flags & DCACHE_DISCONNECTED) {
244 /* something went wrong - oh-well */
245 if (!err)
246 err = -ESTALE;
247 goto err_target;
248 }
249 /* if we weren't after a directory, have one more step to go */
250 if (result != target_dir) {
251 struct dentry *nresult;
252 err = CALL(nops,get_name)(target_dir, nbuf, result);
253 if (!err) {
254 mutex_lock(&target_dir->d_inode->i_mutex);
255 nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
256 mutex_unlock(&target_dir->d_inode->i_mutex);
257 if (!IS_ERR(nresult)) {
258 if (nresult->d_inode) {
259 dput(result);
260 result = nresult;
261 } else
262 dput(nresult);
263 }
264 }
265 }
266 dput(target_dir);
267 /* now result is properly connected, it is our best bet */
268 if (acceptable(context, result))
269 return result;
271 alias = find_acceptable_alias(result, acceptable, context);
272 if (alias)
273 return alias;
275 /* drat - I just cannot find anything acceptable */
276 dput(result);
277 /* It might be justifiable to return ESTALE here,
278 * but the filehandle at-least looks reasonable good
279 * and it just be a permission problem, so returning
280 * -EACCESS is safer
281 */
282 return ERR_PTR(-EACCES);
284 err_target:
285 dput(target_dir);
286 err_result:
287 dput(result);
288 err_out:
289 return ERR_PTR(err);
290 }
294 static struct dentry *get_parent(struct dentry *child)
295 {
296 /* get_parent cannot be supported generically, the locking
297 * is too icky.
298 * instead, we just return EACCES. If server reboots or inodes
299 * get flushed, you lose
300 */
301 return ERR_PTR(-EACCES);
302 }
305 struct getdents_callback {
306 char *name; /* name that was found. It already points to a
307 buffer NAME_MAX+1 is size */
308 unsigned long ino; /* the inum we are looking for */
309 int found; /* inode matched? */
310 int sequence; /* sequence counter */
311 };
313 /*
314 * A rather strange filldir function to capture
315 * the name matching the specified inode number.
316 */
317 static int filldir_one(void * __buf, const char * name, int len,
318 loff_t pos, ino_t ino, unsigned int d_type)
319 {
320 struct getdents_callback *buf = __buf;
321 int result = 0;
323 buf->sequence++;
324 if (buf->ino == ino) {
325 memcpy(buf->name, name, len);
326 buf->name[len] = '\0';
327 buf->found = 1;
328 result = -1;
329 }
330 return result;
331 }
333 /**
334 * get_name - default export_operations->get_name function
335 * @dentry: the directory in which to find a name
336 * @name: a pointer to a %NAME_MAX+1 char buffer to store the name
337 * @child: the dentry for the child directory.
338 *
339 * calls readdir on the parent until it finds an entry with
340 * the same inode number as the child, and returns that.
341 */
342 static int get_name(struct dentry *dentry, char *name,
343 struct dentry *child)
344 {
345 struct inode *dir = dentry->d_inode;
346 int error;
347 struct file *file;
348 struct getdents_callback buffer;
350 error = -ENOTDIR;
351 if (!dir || !S_ISDIR(dir->i_mode))
352 goto out;
353 error = -EINVAL;
354 if (!dir->i_fop)
355 goto out;
356 /*
357 * Open the directory ...
358 */
359 file = dentry_open(dget(dentry), NULL, O_RDONLY);
360 error = PTR_ERR(file);
361 if (IS_ERR(file))
362 goto out;
364 error = -EINVAL;
365 if (!file->f_op->readdir)
366 goto out_close;
368 buffer.name = name;
369 buffer.ino = child->d_inode->i_ino;
370 buffer.found = 0;
371 buffer.sequence = 0;
372 while (1) {
373 int old_seq = buffer.sequence;
375 error = vfs_readdir(file, filldir_one, &buffer);
377 if (error < 0)
378 break;
380 error = 0;
381 if (buffer.found)
382 break;
383 error = -ENOENT;
384 if (old_seq == buffer.sequence)
385 break;
386 }
388 out_close:
389 fput(file);
390 out:
391 return error;
392 }
395 static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation)
396 {
398 /* iget isn't really right if the inode is currently unallocated!!
399 * This should really all be done inside each filesystem
400 *
401 * ext2fs' read_inode has been strengthed to return a bad_inode if
402 * the inode had been deleted.
403 *
404 * Currently we don't know the generation for parent directory, so
405 * a generation of 0 means "accept any"
406 */
407 struct inode *inode;
408 struct dentry *result;
409 if (ino == 0)
410 return ERR_PTR(-ESTALE);
411 inode = iget(sb, ino);
412 if (inode == NULL)
413 return ERR_PTR(-ENOMEM);
414 if (is_bad_inode(inode)
415 || (generation && inode->i_generation != generation)
416 ) {
417 /* we didn't find the right inode.. */
418 dprintk("fh_verify: Inode %lu, Bad count: %d %d or version %u %u\n",
419 inode->i_ino,
420 inode->i_nlink, atomic_read(&inode->i_count),
421 inode->i_generation,
422 generation);
424 iput(inode);
425 return ERR_PTR(-ESTALE);
426 }
427 /* now to find a dentry.
428 * If possible, get a well-connected one
429 */
430 result = d_alloc_anon(inode);
431 if (!result) {
432 iput(inode);
433 return ERR_PTR(-ENOMEM);
434 }
435 return result;
436 }
439 static struct dentry *get_object(struct super_block *sb, void *vobjp)
440 {
441 __u32 *objp = vobjp;
442 unsigned long ino = objp[0];
443 __u32 generation = objp[1];
445 return export_iget(sb, ino, generation);
446 }
449 /**
450 * export_encode_fh - default export_operations->encode_fh function
451 * @dentry: the dentry to encode
452 * @fh: where to store the file handle fragment
453 * @max_len: maximum length to store there
454 * @connectable: whether to store parent information
455 *
456 * This default encode_fh function assumes that the 32 inode number
457 * is suitable for locating an inode, and that the generation number
458 * can be used to check that it is still valid. It places them in the
459 * filehandle fragment where export_decode_fh expects to find them.
460 */
461 static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
462 int connectable)
463 {
464 struct inode * inode = dentry->d_inode;
465 int len = *max_len;
466 int type = 1;
468 if (len < 2 || (connectable && len < 4))
469 return 255;
471 len = 2;
472 fh[0] = inode->i_ino;
473 fh[1] = inode->i_generation;
474 if (connectable && !S_ISDIR(inode->i_mode)) {
475 struct inode *parent;
477 spin_lock(&dentry->d_lock);
478 parent = dentry->d_parent->d_inode;
479 fh[2] = parent->i_ino;
480 fh[3] = parent->i_generation;
481 spin_unlock(&dentry->d_lock);
482 len = 4;
483 type = 2;
484 }
485 *max_len = len;
486 return type;
487 }
490 /**
491 * export_decode_fh - default export_operations->decode_fh function
492 * @sb: The superblock
493 * @fh: pointer to the file handle fragment
494 * @fh_len: length of file handle fragment
495 * @acceptable: function for testing acceptability of dentrys
496 * @context: context for @acceptable
497 *
498 * This is the default decode_fh() function.
499 * a fileid_type of 1 indicates that the filehandlefragment
500 * just contains an object identifier understood by get_dentry.
501 * a fileid_type of 2 says that there is also a directory
502 * identifier 8 bytes in to the filehandlefragement.
503 */
504 static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len,
505 int fileid_type,
506 int (*acceptable)(void *context, struct dentry *de),
507 void *context)
508 {
509 __u32 parent[2];
510 parent[0] = parent[1] = 0;
511 if (fh_len < 2 || fileid_type > 2)
512 return NULL;
513 if (fileid_type == 2) {
514 if (fh_len > 2) parent[0] = fh[2];
515 if (fh_len > 3) parent[1] = fh[3];
516 }
517 return find_exported_dentry(sb, fh, parent,
518 acceptable, context);
519 }
521 struct export_operations export_op_default = {
522 .decode_fh = export_decode_fh,
523 .encode_fh = export_encode_fh,
525 .get_name = get_name,
526 .get_parent = get_parent,
527 .get_dentry = get_object,
528 };
530 EXPORT_SYMBOL(export_op_default);
531 EXPORT_SYMBOL(find_exported_dentry);
533 MODULE_LICENSE("GPL");