expfs.c 13.7 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1

2
#include <linux/exportfs.h>
Linus Torvalds's avatar
Linus Torvalds committed
3 4 5
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/module.h>
6
#include <linux/mount.h>
Linus Torvalds's avatar
Linus Torvalds committed
7 8
#include <linux/namei.h>

9
#define dprintk(fmt, args...) do{}while(0)
Linus Torvalds's avatar
Linus Torvalds committed
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
static int get_name(struct dentry *dentry, char *name,
		struct dentry *child);


static struct dentry *exportfs_get_dentry(struct super_block *sb, void *obj)
{
	struct dentry *result = ERR_PTR(-ESTALE);

	if (sb->s_export_op->get_dentry) {
		result = sb->s_export_op->get_dentry(sb, obj);
		if (!result)
			result = ERR_PTR(-ESTALE);
	}

	return result;
}

static int exportfs_get_name(struct dentry *dir, char *name,
		struct dentry *child)
{
	struct export_operations *nop = dir->d_sb->s_export_op;

	if (nop->get_name)
		return nop->get_name(dir, name, child);
	else
		return get_name(dir, name, child);
}
Linus Torvalds's avatar
Linus Torvalds committed
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
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;
}

Linus Torvalds's avatar
Linus Torvalds committed
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
/**
 * 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;
106
	int err = -ESTALE;
Linus Torvalds's avatar
Linus Torvalds committed
107
	struct export_operations *nops = sb->s_export_op;
108
	struct dentry *alias;
Linus Torvalds's avatar
Linus Torvalds committed
109 110 111 112 113 114
	int noprogress;
	char nbuf[NAME_MAX+1];

	/*
	 * Attempt to find the inode.
	 */
115 116 117 118
	result = exportfs_get_dentry(sb, obj);
	if (IS_ERR(result))
		return result;

119 120 121 122
	if (S_ISDIR(result->d_inode->i_mode)) {
		if (!(result->d_flags & DCACHE_DISCONNECTED)) {
			if (acceptable(context, result))
				return result;
123
			err = -EACCES;
Linus Torvalds's avatar
Linus Torvalds committed
124 125
			goto err_result;
		}
126

127 128 129 130 131
		target_dir = dget(result);
	} else {
		if (acceptable(context, result))
			return result;

132 133 134
		alias = find_acceptable_alias(result, acceptable, context);
		if (alias)
			return alias;
Linus Torvalds's avatar
Linus Torvalds committed
135 136 137 138

		if (parent == NULL)
			goto err_result;

139 140
		target_dir = exportfs_get_dentry(sb,parent);
		if (IS_ERR(target_dir)) {
Linus Torvalds's avatar
Linus Torvalds committed
141 142
			err = PTR_ERR(target_dir);
			goto err_result;
143
		}
Linus Torvalds's avatar
Linus Torvalds committed
144
	}
145

Linus Torvalds's avatar
Linus Torvalds committed
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
	/*
	 * 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 {
195 196 197 198 199 200 201 202 203 204 205 206 207 208
			/*
			 * We have hit the top of a disconnected path, try to
			 * find parent and connect.
			 *
			 * 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
			 *
			 * Getting the parent can't be supported generically,
			 * the locking is too icky.
			 *
			 * Instead we just return EACCES.  If server reboots
			 * or inodes get flushed, you lose
Linus Torvalds's avatar
Linus Torvalds committed
209
			 */
210
			struct dentry *ppd = ERR_PTR(-EACCES);
Linus Torvalds's avatar
Linus Torvalds committed
211 212
			struct dentry *npd;

213
			mutex_lock(&pd->d_inode->i_mutex);
214 215
			if (nops->get_parent)
				ppd = nops->get_parent(pd);
216
			mutex_unlock(&pd->d_inode->i_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
217 218 219 220 221 222 223 224 225

			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);
226
			err = exportfs_get_name(ppd, nbuf, pd);
Linus Torvalds's avatar
Linus Torvalds committed
227 228 229 230 231 232 233 234 235 236 237
			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);
238
			mutex_lock(&ppd->d_inode->i_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
239
			npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
240
			mutex_unlock(&ppd->d_inode->i_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
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
			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;
277
		err = exportfs_get_name(target_dir, nbuf, result);
Linus Torvalds's avatar
Linus Torvalds committed
278
		if (!err) {
279
			mutex_lock(&target_dir->d_inode->i_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
280
			nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
281
			mutex_unlock(&target_dir->d_inode->i_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
282 283 284 285 286 287 288 289 290 291 292 293 294
			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;
295 296 297 298

	alias = find_acceptable_alias(result, acceptable, context);
	if (alias)
		return alias;
Linus Torvalds's avatar
Linus Torvalds committed
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

	/* 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);
	return ERR_PTR(err);
}

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,
329
			loff_t pos, u64 ino, unsigned int d_type)
Linus Torvalds's avatar
Linus Torvalds committed
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
{
	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;
}

/**
 * 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);
}

477 478 479
int exportfs_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
		int connectable)
{
480 481
 	struct export_operations *nop = dentry->d_sb->s_export_op;
	int error;
482

483 484 485 486 487 488
	if (nop->encode_fh)
		error = nop->encode_fh(dentry, fh, max_len, connectable);
	else
		error = export_encode_fh(dentry, fh, max_len, connectable);

	return error;
489 490 491 492 493 494 495 496
}
EXPORT_SYMBOL_GPL(exportfs_encode_fh);

struct dentry *exportfs_decode_fh(struct vfsmount *mnt, __u32 *fh, int fh_len,
		int fileid_type, int (*acceptable)(void *, struct dentry *),
		void *context)
{
	struct export_operations *nop = mnt->mnt_sb->s_export_op;
497
	struct dentry *result;
498

499 500
	if (nop->decode_fh) {
		result = nop->decode_fh(mnt->mnt_sb, fh, fh_len, fileid_type,
501
			acceptable, context);
502 503 504 505 506 507
	} else {
		result = export_decode_fh(mnt->mnt_sb, fh, fh_len, fileid_type,
			acceptable, context);
	}

	return result;
508 509 510
}
EXPORT_SYMBOL_GPL(exportfs_decode_fh);

Linus Torvalds's avatar
Linus Torvalds committed
511 512 513
EXPORT_SYMBOL(find_exported_dentry);

MODULE_LICENSE("GPL");