aboutsummaryrefslogtreecommitdiff
path: root/fs/exportfs/expfs.c
blob: 4c39009350f3e59529363108800c003de2e2d2d0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533

#include <linux/fs.h>
#include <linux/file.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/namei.h>

struct export_operations export_op_default;

#define	CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun)

#define dprintk(fmt, args...) do{}while(0)

static struct dentry *
find_acceptable_alias(struct dentry *result,
		int (*acceptable)(void *context, struct dentry *dentry),
		void *context)
{
	struct dentry *dentry, *toput = NULL;

	spin_lock(&dcache_lock);
	list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
		dget_locked(dentry);
		spin_unlock(&dcache_lock);
		if (toput)
			dput(toput);
		if (dentry != result && acceptable(context, dentry)) {
			dput(result);
			return dentry;
		}
		spin_lock(&dcache_lock);
		toput = dentry;
	}
	spin_unlock(&dcache_lock);

	if (toput)
		dput(toput);
	return NULL;
}

/**
 * find_exported_dentry - helper routine to implement export_operations->decode_fh
 * @sb:		The &super_block identifying the filesystem
 * @obj:	An opaque identifier of the object to be found - passed to
 *		get_inode
 * @parent:	An optional opqaue identifier of the parent of the object.
 * @acceptable:	A function used to test possible &dentries to see if they are
 *		acceptable
 * @context:	A parameter to @acceptable so that it knows on what basis to
 *		judge.
 *
 * find_exported_dentry is the central helper routine to enable file systems
 * to provide the decode_fh() export_operation.  It's main task is to take
 * an &inode, find or create an appropriate &dentry structure, and possibly
 * splice this into the dcache in the correct place.
 *
 * The decode_fh() operation provided by the filesystem should call
 * find_exported_dentry() with the same parameters that it received except
 * that instead of the file handle fragment, pointers to opaque identifiers
 * for the object and optionally its parent are passed.  The default decode_fh
 * routine passes one pointer to the start of the filehandle fragment, and
 * one 8 bytes into the fragment.  It is expected that most filesystems will
 * take this approach, though the offset to the parent identifier may well be
 * different.
 *
 * find_exported_dentry() will call get_dentry to get an dentry pointer from
 * the file system.  If any &dentry in the d_alias list is acceptable, it will
 * be returned.  Otherwise find_exported_dentry() will attempt to splice a new
 * &dentry into the dcache using get_name() and get_parent() to find the
 * appropriate place.
 */

struct dentry *
find_exported_dentry(struct super_block *sb, void *obj, void *parent,
		     int (*acceptable)(void *context, struct dentry *de),
		     void *context)
{
	struct dentry *result = NULL;
	struct dentry *target_dir;
	int err;
	struct export_operations *nops = sb->s_export_op;
	struct dentry *alias;
	int noprogress;
	char nbuf[NAME_MAX+1];

	/*
	 * Attempt to find the inode.
	 */
	result = CALL(sb->s_export_op,get_dentry)(sb,obj);
	err = -ESTALE;
	if (result == NULL)
		goto err_out;
	if (IS_ERR(result)) {
		err = PTR_ERR(result);
		goto err_out;
	}
	if (S_ISDIR(result->d_inode->i_mode) &&
	    (result->d_flags & DCACHE_DISCONNECTED)) {
		/* it is an unconnected directory, we must connect it */
		;
	} else {
		if (acceptable(context, result))
			return result;
		if (S_ISDIR(result->d_inode->i_mode)) {
			err = -EACCES;
			goto err_result;
		}

		alias = find_acceptable_alias(result, acceptable, context);
		if (alias)
			return alias;
	}			

	/* It's a directory, or we are required to confirm the file's
	 * location in the tree based on the parent information
 	 */
	dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj);
	if (S_ISDIR(result->d_inode->i_mode))
		target_dir = dget(result);
	else {
		if (parent == NULL)
			goto err_result;

		target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent);
		if (IS_ERR(target_dir))
			err = PTR_ERR(target_dir);
		if (target_dir == NULL || IS_ERR(target_dir))
			goto err_result;
	}
	/*
	 * Now we need to make sure that target_dir is properly connected.
	 * It may already be, as the flag isn't always updated when connection
	 * happens.
	 * So, we walk up parent links until we find a connected directory,
	 * or we run out of directories.  Then we find the parent, find
	 * the name of the child in that parent, and do a lookup.
	 * This should connect the child into the parent
	 * We then repeat.
	 */

	/* it is possible that a confused file system might not let us complete 
	 * the path to the root.  For example, if get_parent returns a directory
	 * in which we cannot find a name for the child.  While this implies a
	 * very sick filesystem we don't want it to cause knfsd to spin.  Hence
	 * the noprogress counter.  If we go through the loop 10 times (2 is
	 * probably enough) without getting anywhere, we just give up
	 */
	noprogress= 0;
	while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
		struct dentry *pd = target_dir;

		dget(pd);
		spin_lock(&pd->d_lock);
		while (!IS_ROOT(pd) &&
				(pd->d_parent->d_flags&DCACHE_DISCONNECTED)) {
			struct dentry *parent = pd->d_parent;

			dget(parent);
			spin_unlock(&pd->d_lock);
			dput(pd);
			pd = parent;
			spin_lock(&pd->d_lock);
		}
		spin_unlock(&pd->d_lock);

		if (!IS_ROOT(pd)) {
			/* must have found a connected parent - great */
			spin_lock(&pd->d_lock);
			pd->d_flags &= ~DCACHE_DISCONNECTED;
			spin_unlock(&pd->d_lock);
			noprogress = 0;
		} else if (pd == sb->s_root) {
			printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
			spin_lock(&pd->d_lock);
			pd->d_flags &= ~DCACHE_DISCONNECTED;
			spin_unlock(&pd->d_lock);
			noprogress = 0;
		} else {
			/* we have hit the top of a disconnected path.  Try
			 * to find parent and connect
			 * note: racing with some other process renaming a
			 * directory isn't much of a problem here.  If someone
			 * renames the directory, it will end up properly
			 * connected, which is what we want
			 */
			struct dentry *ppd;
			struct dentry *npd;

			mutex_lock(&pd->d_inode->i_mutex);
			ppd = CALL(nops,get_parent)(pd);
			mutex_unlock(&pd->d_inode->i_mutex);

			if (IS_ERR(ppd)) {
				err = PTR_ERR(ppd);
				dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n",
					pd->d_inode->i_ino, err);
				dput(pd);
				break;
			}
			dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino);
			err = CALL(nops,get_name)(ppd, nbuf, pd);
			if (err) {
				dput(ppd);
				dput(pd);
				if (err == -ENOENT)
					/* some race between get_parent and
					 * get_name?  just try again
					 */
					continue;
				break;
			}
			dprintk("find_exported_dentry: found name: %s\n", nbuf);
			mutex_lock(&ppd->d_inode->i_mutex);
			npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
			mutex_unlock(&ppd->d_inode->i_mutex);
			if (IS_ERR(npd)) {
				err = PTR_ERR(npd);
				dprintk("find_exported_dentry: lookup failed: %d\n", err);
				dput(ppd);
				dput(pd);
				break;
			}
			/* we didn't really want npd, we really wanted
			 * a side-effect of the lookup.
			 * hopefully, npd == pd, though it isn't really
			 * a problem if it isn't
			 */
			if (npd == pd)
				noprogress = 0;
			else
				printk("find_exported_dentry: npd != pd\n");
			dput(npd);
			dput(ppd);
			if (IS_ROOT(pd)) {
				/* something went wrong, we have to give up */
				dput(pd);
				break;
			}
		}
		dput(pd);
	}

	if (target_dir->d_flags & DCACHE_DISCONNECTED) {
		/* something went wrong - oh-well */
		if (!err)
			err = -ESTALE;
		goto err_target;
	}
	/* if we weren't after a directory, have one more step to go */
	if (result != target_dir) {
		struct dentry *nresult;
		err = CALL(nops,get_name)(target_dir, nbuf, result);
		if (!err) {
			mutex_lock(&target_dir->d_inode->i_mutex);
			nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
			mutex_unlock(&target_dir->d_inode->i_mutex);
			if (!IS_ERR(nresult)) {
				if (nresult->d_inode) {
					dput(result);
					result = nresult;
				} else
					dput(nresult);
			}
		}
	}
	dput(target_dir);
	/* now result is properly connected, it is our best bet */
	if (acceptable(context, result))
		return result;

	alias = find_acceptable_alias(result, acceptable, context);
	if (alias)
		return alias;

	/* drat - I just cannot find anything acceptable */
	dput(result);
	/* It might be justifiable to return ESTALE here,
	 * but the filehandle at-least looks reasonable good
	 * and it just be a permission problem, so returning
	 * -EACCESS is safer
	 */
	return ERR_PTR(-EACCES);

 err_target:
	dput(target_dir);
 err_result:
	dput(result);
 err_out:
	return ERR_PTR(err);
}



static struct dentry *get_parent(struct dentry *child)
{
	/* get_parent cannot be supported generically, the locking
	 * is too icky.
	 * instead, we just return EACCES.  If server reboots or inodes
	 * get flushed, you lose
	 */
	return ERR_PTR(-EACCES);
}


struct getdents_callback {
	char *name;		/* name that was found. It already points to a
				   buffer NAME_MAX+1 is size */
	unsigned long ino;	/* the inum we are looking for */
	int found;		/* inode matched? */
	int sequence;		/* sequence counter */
};

/*
 * A rather strange filldir function to capture
 * the name matching the specified inode number.
 */
static int filldir_one(void * __buf, const char * name, int len,
			loff_t pos, ino_t ino, unsigned int d_type)
{
	struct getdents_callback *buf = __buf;
	int result = 0;

	buf->sequence++;
	if (buf->ino == ino) {
		memcpy(buf->name, name, len);
		buf->name[len] = '\0';
		buf->found = 1;
		result = -1;
	}
	return result;
}

/**
 * get_name - default export_operations->get_name function
 * @dentry: the directory in which to find a name
 * @name:   a pointer to a %NAME_MAX+1 char buffer to store the name
 * @child:  the dentry for the child directory.
 *
 * calls readdir on the parent until it finds an entry with
 * the same inode number as the child, and returns that.
 */
static int get_name(struct dentry *dentry, char *name,
			struct dentry *child)
{
	struct inode *dir = dentry->d_inode;
	int error;
	struct file *file;
	struct getdents_callback buffer;

	error = -ENOTDIR;
	if (!dir || !S_ISDIR(dir->i_mode))
		goto out;
	error = -EINVAL;
	if (!dir->i_fop)
		goto out;
	/*
	 * Open the directory ...
	 */
	file = dentry_open(dget(dentry), NULL, O_RDONLY);
	error = PTR_ERR(file);
	if (IS_ERR(file))
		goto out;

	error = -EINVAL;
	if (!file->f_op->readdir)
		goto out_close;

	buffer.name = name;
	buffer.ino = child->d_inode->i_ino;
	buffer.found = 0;
	buffer.sequence = 0;
	while (1) {
		int old_seq = buffer.sequence;

		error = vfs_readdir(file, filldir_one, &buffer);

		if (error < 0)
			break;

		error = 0;
		if (buffer.found)
			break;
		error = -ENOENT;
		if (old_seq == buffer.sequence)
			break;
	}

out_close:
	fput(file);
out:
	return error;
}


static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation)
{

	/* iget isn't really right if the inode is currently unallocated!!
	 * This should really all be done inside each filesystem
	 *
	 * ext2fs' read_inode has been strengthed to return a bad_inode if
	 * the inode had been deleted.
	 *
	 * Currently we don't know the generation for parent directory, so
	 * a generation of 0 means "accept any"
	 */
	struct inode *inode;
	struct dentry *result;
	if (ino == 0)
		return ERR_PTR(-ESTALE);
	inode = iget(sb, ino);
	if (inode == NULL)
		return ERR_PTR(-ENOMEM);
	if (is_bad_inode(inode)
	    || (generation && inode->i_generation != generation)
		) {
		/* we didn't find the right inode.. */
		dprintk("fh_verify: Inode %lu, Bad count: %d %d or version  %u %u\n",
			inode->i_ino,
			inode->i_nlink, atomic_read(&inode->i_count),
			inode->i_generation,
			generation);

		iput(inode);
		return ERR_PTR(-ESTALE);
	}
	/* now to find a dentry.
	 * If possible, get a well-connected one
	 */
	result = d_alloc_anon(inode);
	if (!result) {
		iput(inode);
		return ERR_PTR(-ENOMEM);
	}
	return result;
}


static struct dentry *get_object(struct super_block *sb, void *vobjp)
{
	__u32 *objp = vobjp;
	unsigned long ino = objp[0];
	__u32 generation = objp[1];

	return export_iget(sb, ino, generation);
}


/**
 * export_encode_fh - default export_operations->encode_fh function
 * @dentry:  the dentry to encode
 * @fh:      where to store the file handle fragment
 * @max_len: maximum length to store there
 * @connectable: whether to store parent information
 *
 * This default encode_fh function assumes that the 32 inode number
 * is suitable for locating an inode, and that the generation number
 * can be used to check that it is still valid.  It places them in the
 * filehandle fragment where export_decode_fh expects to find them.
 */
static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
		   int connectable)
{
	struct inode * inode = dentry->d_inode;
	int len = *max_len;
	int type = 1;
	
	if (len < 2 || (connectable && len < 4))
		return 255;

	len = 2;
	fh[0] = inode->i_ino;
	fh[1] = inode->i_generation;
	if (connectable && !S_ISDIR(inode->i_mode)) {
		struct inode *parent;

		spin_lock(&dentry->d_lock);
		parent = dentry->d_parent->d_inode;
		fh[2] = parent->i_ino;
		fh[3] = parent->i_generation;
		spin_unlock(&dentry->d_lock);
		len = 4;
		type = 2;
	}
	*max_len = len;
	return type;
}


/**
 * export_decode_fh - default export_operations->decode_fh function
 * @sb:  The superblock
 * @fh:  pointer to the file handle fragment
 * @fh_len: length of file handle fragment
 * @acceptable: function for testing acceptability of dentrys
 * @context:   context for @acceptable
 *
 * This is the default decode_fh() function.
 * a fileid_type of 1 indicates that the filehandlefragment
 * just contains an object identifier understood by  get_dentry.
 * a fileid_type of 2 says that there is also a directory
 * identifier 8 bytes in to the filehandlefragement.
 */
static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len,
			      int fileid_type,
			 int (*acceptable)(void *context, struct dentry *de),
			 void *context)
{
	__u32 parent[2];
	parent[0] = parent[1] = 0;
	if (fh_len < 2 || fileid_type > 2)
		return NULL;
	if (fileid_type == 2) {
		if (fh_len > 2) parent[0] = fh[2];
		if (fh_len > 3) parent[1] = fh[3];
	}
	return find_exported_dentry(sb, fh, parent,
				   acceptable, context);
}

struct export_operations export_op_default = {
	.decode_fh	= export_decode_fh,
	.encode_fh	= export_encode_fh,

	.get_name	= get_name,
	.get_parent	= get_parent,
	.get_dentry	= get_object,
};

EXPORT_SYMBOL(export_op_default);
EXPORT_SYMBOL(find_exported_dentry);

MODULE_LICENSE("GPL");