[deliverable/linux.git] / fs / exportfs / expfs.c


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

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


static int get_name(struct dentry *dentry, char *name,
		struct dentry *child);


static int exportfs_get_name(struct dentry *dir, char *name,
		struct dentry *child)
{
	const 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);
}

/*
 * Check if the dentry or any of it's aliases is acceptable.
 */
static struct dentry *
find_acceptable_alias(struct dentry *result,
		int (*acceptable)(void *context, struct dentry *dentry),
		void *context)
{
	struct dentry *dentry, *toput = NULL;

	if (acceptable(context, result))
		return result;

	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 root of a disconnected subtree and return a reference to it.
 */
static struct dentry *
find_disconnected_root(struct dentry *dentry)
{
	dget(dentry);
	spin_lock(&dentry->d_lock);
	while (!IS_ROOT(dentry) &&
	       (dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) {
		struct dentry *parent = dentry->d_parent;
		dget(parent);
		spin_unlock(&dentry->d_lock);
		dput(dentry);
		dentry = parent;
		spin_lock(&dentry->d_lock);
	}
	spin_unlock(&dentry->d_lock);
	return dentry;
}


/*
 * Make sure target_dir is fully connected to the dentry tree.
 *
 * It may already be, as the flag isn't always updated when connection happens.
 */
static int
reconnect_path(struct super_block *sb, struct dentry *target_dir)
{
	char nbuf[NAME_MAX+1];
	int noprogress = 0;
	int err = -ESTALE;

	/*
	 * 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
	 */
	while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
		struct dentry *pd = find_disconnected_root(target_dir);

		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.
			 *
			 * 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
			 */
			struct dentry *ppd = ERR_PTR(-EACCES);
			struct dentry *npd;

			mutex_lock(&pd->d_inode->i_mutex);
			if (sb->s_export_op->get_parent)
				ppd = sb->s_export_op->get_parent(pd);
			mutex_unlock(&pd->d_inode->i_mutex);

			if (IS_ERR(ppd)) {
				err = PTR_ERR(ppd);
				dprintk("%s: get_parent of %ld failed, err %d\n",
					__FUNCTION__, pd->d_inode->i_ino, err);
				dput(pd);
				break;
			}

			dprintk("%s: find name of %lu in %lu\n", __FUNCTION__,
				pd->d_inode->i_ino, ppd->d_inode->i_ino);
			err = exportfs_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("%s: found name: %s\n", __FUNCTION__, 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("%s: lookup failed: %d\n",
					__FUNCTION__, 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("%s: npd != pd\n", __FUNCTION__);
			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;
		return err;
	}

	return 0;
}

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, u64 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;
}

/**
 * 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, struct fid *fid,
		int *max_len, int connectable)
{
	struct inode * inode = dentry->d_inode;
	int len = *max_len;
	int type = FILEID_INO32_GEN;
	
	if (len < 2 || (connectable && len < 4))
		return 255;

	len = 2;
	fid->i32.ino = inode->i_ino;
	fid->i32.gen = inode->i_generation;
	if (connectable && !S_ISDIR(inode->i_mode)) {
		struct inode *parent;

		spin_lock(&dentry->d_lock);
		parent = dentry->d_parent->d_inode;
		fid->i32.parent_ino = parent->i_ino;
		fid->i32.parent_gen = parent->i_generation;
		spin_unlock(&dentry->d_lock);
		len = 4;
		type = FILEID_INO32_GEN_PARENT;
	}
	*max_len = len;
	return type;
}

int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
		int connectable)
{
	const struct export_operations *nop = dentry->d_sb->s_export_op;
	int error;

	if (nop->encode_fh)
		error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
	else
		error = export_encode_fh(dentry, fid, max_len, connectable);

	return error;
}
EXPORT_SYMBOL_GPL(exportfs_encode_fh);

struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
		int fh_len, int fileid_type,
		int (*acceptable)(void *, struct dentry *), void *context)
{
	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
	struct dentry *result, *alias;
	int err;

	/*
	 * Try to get any dentry for the given file handle from the filesystem.
	 */
	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
	if (!result)
		result = ERR_PTR(-ESTALE);
	if (IS_ERR(result))
		return result;

	if (S_ISDIR(result->d_inode->i_mode)) {
		/*
		 * This request is for a directory.
		 *
		 * On the positive side there is only one dentry for each
		 * directory inode.  On the negative side this implies that we
		 * to ensure our dentry is connected all the way up to the
		 * filesystem root.
		 */
		if (result->d_flags & DCACHE_DISCONNECTED) {
			err = reconnect_path(mnt->mnt_sb, result);
			if (err)
				goto err_result;
		}

		if (!acceptable(context, result)) {
			err = -EACCES;
			goto err_result;
		}

		return result;
	} else {
		/*
		 * It's not a directory.  Life is a little more complicated.
		 */
		struct dentry *target_dir, *nresult;
		char nbuf[NAME_MAX+1];

		/*
		 * See if either the dentry we just got from the filesystem
		 * or any alias for it is acceptable.  This is always true
		 * if this filesystem is exported without the subtreecheck
		 * option.  If the filesystem is exported with the subtree
		 * check option there's a fair chance we need to look at
		 * the parent directory in the file handle and make sure
		 * it's connected to the filesystem root.
		 */
		alias = find_acceptable_alias(result, acceptable, context);
		if (alias)
			return alias;

		/*
		 * Try to extract a dentry for the parent directory from the
		 * file handle.  If this fails we'll have to give up.
		 */
		err = -ESTALE;
		if (!nop->fh_to_parent)
			goto err_result;

		target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
				fh_len, fileid_type);
		if (!target_dir)
			goto err_result;
		err = PTR_ERR(target_dir);
		if (IS_ERR(target_dir))
			goto err_result;

		/*
		 * And as usual we need to make sure the parent directory is
		 * connected to the filesystem root.  The VFS really doesn't
		 * like disconnected directories..
		 */
		err = reconnect_path(mnt->mnt_sb, target_dir);
		if (err) {
			dput(target_dir);
			goto err_result;
		}

		/*
		 * Now that we've got both a well-connected parent and a
		 * dentry for the inode we're after, make sure that our
		 * inode is actually connected to the parent.
		 */
		err = exportfs_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);
			}
		}

		/*
		 * At this point we are done with the parent, but it's pinned
		 * by the child dentry anyway.
		 */
		dput(target_dir);

		/*
		 * And finally make sure the dentry is actually acceptable
		 * to NFSD.
		 */
		alias = find_acceptable_alias(result, acceptable, context);
		if (!alias) {
			err = -EACCES;
			goto err_result;
		}

		return alias;
	}

 err_result:
	dput(result);
	return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(exportfs_decode_fh);

MODULE_LICENSE("GPL");
Commit	Line	Data
1da177e4	1
a5694255	2	#include <linux/exportfs.h>
1da177e4 LT	3	#include <linux/fs.h>
	4	#include <linux/file.h>
	5	#include <linux/module.h>
d37065cd	6	#include <linux/mount.h>
1da177e4 LT	7	#include <linux/namei.h>
1da177e4 LT	8
10f11c34	9	#define dprintk(fmt, args...) do{}while(0)
1da177e4	10
1da177e4	11
10f11c34 CH	12	static int get_name(struct dentry dentry, char name,
	13	struct dentry *child);
	14
	15
10f11c34 CH	16	static int exportfs_get_name(struct dentry dir, char name,
	17	struct dentry *child)
	18	{
39655164	19	const struct export_operations *nop = dir->d_sb->s_export_op;
10f11c34 CH	20
	21	if (nop->get_name)
	22	return nop->get_name(dir, name, child);
	23	else
	24	return get_name(dir, name, child);
	25	}
1da177e4	26
fb66a198 CH	27	/*
	28	* Check if the dentry or any of it's aliases is acceptable.
	29	*/
e2f99018 CH	30	static struct dentry *
	31	find_acceptable_alias(struct dentry *result,
	32	int (acceptable)(void context, struct dentry *dentry),
	33	void *context)
	34	{
	35	struct dentry dentry, toput = NULL;
	36
fb66a198 CH	37	if (acceptable(context, result))
	38	return result;
	39
e2f99018 CH	40	spin_lock(&dcache_lock);
	41	list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
	42	dget_locked(dentry);
	43	spin_unlock(&dcache_lock);
	44	if (toput)
	45	dput(toput);
	46	if (dentry != result && acceptable(context, dentry)) {
	47	dput(result);
	48	return dentry;
	49	}
	50	spin_lock(&dcache_lock);
	51	toput = dentry;
	52	}
	53	spin_unlock(&dcache_lock);
	54
	55	if (toput)
	56	dput(toput);
	57	return NULL;
	58	}
	59
dd90b509 CH	60	/*
	61	* Find root of a disconnected subtree and return a reference to it.
	62	*/
	63	static struct dentry *
	64	find_disconnected_root(struct dentry *dentry)
	65	{
	66	dget(dentry);
	67	spin_lock(&dentry->d_lock);
	68	while (!IS_ROOT(dentry) &&
	69	(dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) {
	70	struct dentry *parent = dentry->d_parent;
	71	dget(parent);
	72	spin_unlock(&dentry->d_lock);
	73	dput(dentry);
	74	dentry = parent;
	75	spin_lock(&dentry->d_lock);
	76	}
	77	spin_unlock(&dentry->d_lock);
	78	return dentry;
	79	}
	80
019ab801 CH	81
	82	/*
	83	* Make sure target_dir is fully connected to the dentry tree.
1da177e4	84	*
019ab801	85	* It may already be, as the flag isn't always updated when connection happens.
1da177e4	86	*/
019ab801 CH	87	static int
019ab801 CH	88	reconnect_path(struct super_block sb, struct dentry target_dir)
1da177e4	89	{
1da177e4	90	char nbuf[NAME_MAX+1];
019ab801 CH	91	int noprogress = 0;
019ab801 CH	92	int err = -ESTALE;
1da177e4 LT	93
1da177e4 LT	94	/*
019ab801	95	* It is possible that a confused file system might not let us complete
1da177e4 LT	96	* the path to the root. For example, if get_parent returns a directory
	97	* in which we cannot find a name for the child. While this implies a
	98	* very sick filesystem we don't want it to cause knfsd to spin. Hence
	99	* the noprogress counter. If we go through the loop 10 times (2 is
	100	* probably enough) without getting anywhere, we just give up
	101	*/
1da177e4	102	while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
dd90b509	103	struct dentry *pd = find_disconnected_root(target_dir);
1da177e4 LT	104
	105	if (!IS_ROOT(pd)) {
	106	/* must have found a connected parent - great */
	107	spin_lock(&pd->d_lock);
	108	pd->d_flags &= ~DCACHE_DISCONNECTED;
	109	spin_unlock(&pd->d_lock);
	110	noprogress = 0;
	111	} else if (pd == sb->s_root) {
	112	printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
	113	spin_lock(&pd->d_lock);
	114	pd->d_flags &= ~DCACHE_DISCONNECTED;
	115	spin_unlock(&pd->d_lock);
	116	noprogress = 0;
	117	} else {
10f11c34 CH	118	/*
	119	* We have hit the top of a disconnected path, try to
	120	* find parent and connect.
	121	*
	122	* Racing with some other process renaming a directory
	123	* isn't much of a problem here. If someone renames
	124	* the directory, it will end up properly connected,
	125	* which is what we want
	126	*
	127	* Getting the parent can't be supported generically,
	128	* the locking is too icky.
	129	*
	130	* Instead we just return EACCES. If server reboots
	131	* or inodes get flushed, you lose
1da177e4	132	*/
10f11c34	133	struct dentry *ppd = ERR_PTR(-EACCES);
1da177e4 LT	134	struct dentry *npd;
1da177e4 LT	135
1b1dcc1b	136	mutex_lock(&pd->d_inode->i_mutex);
019ab801 CH	137	if (sb->s_export_op->get_parent)
019ab801 CH	138	ppd = sb->s_export_op->get_parent(pd);
1b1dcc1b	139	mutex_unlock(&pd->d_inode->i_mutex);
1da177e4 LT	140
	141	if (IS_ERR(ppd)) {
	142	err = PTR_ERR(ppd);
019ab801 CH	143	dprintk("%s: get_parent of %ld failed, err %d\n",
019ab801 CH	144	__FUNCTION__, pd->d_inode->i_ino, err);
1da177e4 LT	145	dput(pd);
	146	break;
	147	}
019ab801 CH	148
	149	dprintk("%s: find name of %lu in %lu\n", __FUNCTION__,
	150	pd->d_inode->i_ino, ppd->d_inode->i_ino);
10f11c34	151	err = exportfs_get_name(ppd, nbuf, pd);
1da177e4 LT	152	if (err) {
	153	dput(ppd);
	154	dput(pd);
	155	if (err == -ENOENT)
	156	/* some race between get_parent and
	157	* get_name? just try again
	158	*/
	159	continue;
	160	break;
	161	}
019ab801	162	dprintk("%s: found name: %s\n", __FUNCTION__, nbuf);
1b1dcc1b	163	mutex_lock(&ppd->d_inode->i_mutex);
1da177e4	164	npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
1b1dcc1b	165	mutex_unlock(&ppd->d_inode->i_mutex);
1da177e4 LT	166	if (IS_ERR(npd)) {
1da177e4 LT	167	err = PTR_ERR(npd);
019ab801 CH	168	dprintk("%s: lookup failed: %d\n",
019ab801 CH	169	__FUNCTION__, err);
1da177e4 LT	170	dput(ppd);
	171	dput(pd);
	172	break;
	173	}
	174	/* we didn't really want npd, we really wanted
	175	* a side-effect of the lookup.
	176	* hopefully, npd == pd, though it isn't really
	177	* a problem if it isn't
	178	*/
	179	if (npd == pd)
	180	noprogress = 0;
	181	else
019ab801	182	printk("%s: npd != pd\n", __FUNCTION__);
1da177e4 LT	183	dput(npd);
	184	dput(ppd);
	185	if (IS_ROOT(pd)) {
	186	/* something went wrong, we have to give up */
	187	dput(pd);
	188	break;
	189	}
	190	}
	191	dput(pd);
	192	}
	193
	194	if (target_dir->d_flags & DCACHE_DISCONNECTED) {
	195	/* something went wrong - oh-well */
	196	if (!err)
	197	err = -ESTALE;
019ab801	198	return err;
1da177e4	199	}
019ab801 CH	200
	201	return 0;
	202	}
	203
1da177e4 LT	204	struct getdents_callback {
	205	char name; / name that was found. It already points to a
	206	buffer NAME_MAX+1 is size */
	207	unsigned long ino; /* the inum we are looking for */
	208	int found; /* inode matched? */
	209	int sequence; /* sequence counter */
	210	};
	211
	212	/*
	213	* A rather strange filldir function to capture
	214	* the name matching the specified inode number.
	215	*/
	216	static int filldir_one(void * __buf, const char * name, int len,
afefdbb2	217	loff_t pos, u64 ino, unsigned int d_type)
1da177e4 LT	218	{
	219	struct getdents_callback *buf = __buf;
	220	int result = 0;
	221
	222	buf->sequence++;
	223	if (buf->ino == ino) {
	224	memcpy(buf->name, name, len);
	225	buf->name[len] = '\0';
	226	buf->found = 1;
	227	result = -1;
	228	}
	229	return result;
	230	}
	231
	232	/**
	233	* get_name - default export_operations->get_name function
	234	* @dentry: the directory in which to find a name
	235	* @name: a pointer to a %NAME_MAX+1 char buffer to store the name
	236	* @child: the dentry for the child directory.
	237	*
	238	* calls readdir on the parent until it finds an entry with
	239	* the same inode number as the child, and returns that.
	240	*/
	241	static int get_name(struct dentry dentry, char name,
	242	struct dentry *child)
	243	{
	244	struct inode *dir = dentry->d_inode;
	245	int error;
	246	struct file *file;
	247	struct getdents_callback buffer;
	248
	249	error = -ENOTDIR;
	250	if (!dir \|\| !S_ISDIR(dir->i_mode))
	251	goto out;
	252	error = -EINVAL;
	253	if (!dir->i_fop)
	254	goto out;
	255	/*
	256	* Open the directory ...
	257	*/
	258	file = dentry_open(dget(dentry), NULL, O_RDONLY);
	259	error = PTR_ERR(file);
	260	if (IS_ERR(file))
	261	goto out;
	262
	263	error = -EINVAL;
	264	if (!file->f_op->readdir)
	265	goto out_close;
	266
	267	buffer.name = name;
	268	buffer.ino = child->d_inode->i_ino;
	269	buffer.found = 0;
	270	buffer.sequence = 0;
	271	while (1) {
	272	int old_seq = buffer.sequence;
	273
	274	error = vfs_readdir(file, filldir_one, &buffer);
	275
	276	if (error < 0)
	277	break;
	278
	279	error = 0;
	280	if (buffer.found)
	281	break;
282	error = -ENOENT;
283	if (old_seq == buffer.sequence)
284	break;
285	}
286
287	out_close:
288	fput(file);
289	out:
290	return error;
291	}
292
1da177e4 LT	293	/**
	294	* export_encode_fh - default export_operations->encode_fh function
	295	* @dentry: the dentry to encode
	296	* @fh: where to store the file handle fragment
	297	* @max_len: maximum length to store there
	298	* @connectable: whether to store parent information
	299	*
	300	* This default encode_fh function assumes that the 32 inode number
	301	* is suitable for locating an inode, and that the generation number
	302	* can be used to check that it is still valid. It places them in the
	303	* filehandle fragment where export_decode_fh expects to find them.
	304	*/
6e91ea2b CH	305	static int export_encode_fh(struct dentry dentry, struct fid fid,
6e91ea2b CH	306	int *max_len, int connectable)
1da177e4 LT	307	{
	308	struct inode * inode = dentry->d_inode;
	309	int len = *max_len;
6e91ea2b	310	int type = FILEID_INO32_GEN;
1da177e4 LT	311
	312	if (len < 2 \|\| (connectable && len < 4))
	313	return 255;
	314
	315	len = 2;
6e91ea2b CH	316	fid->i32.ino = inode->i_ino;
6e91ea2b CH	317	fid->i32.gen = inode->i_generation;
1da177e4 LT	318	if (connectable && !S_ISDIR(inode->i_mode)) {
	319	struct inode *parent;
	320
	321	spin_lock(&dentry->d_lock);
	322	parent = dentry->d_parent->d_inode;
6e91ea2b CH	323	fid->i32.parent_ino = parent->i_ino;
6e91ea2b CH	324	fid->i32.parent_gen = parent->i_generation;
1da177e4 LT	325	spin_unlock(&dentry->d_lock);
1da177e4 LT	326	len = 4;
6e91ea2b	327	type = FILEID_INO32_GEN_PARENT;
1da177e4 LT	328	}
	329	*max_len = len;
	330	return type;
	331	}
	332
6e91ea2b	333	int exportfs_encode_fh(struct dentry dentry, struct fid fid, int *max_len,
d37065cd CH	334	int connectable)
d37065cd CH	335	{
39655164	336	const struct export_operations *nop = dentry->d_sb->s_export_op;
10f11c34	337	int error;
d37065cd	338
10f11c34	339	if (nop->encode_fh)
6e91ea2b	340	error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
10f11c34	341	else
6e91ea2b	342	error = export_encode_fh(dentry, fid, max_len, connectable);
10f11c34 CH	343
10f11c34 CH	344	return error;
d37065cd CH	345	}
	346	EXPORT_SYMBOL_GPL(exportfs_encode_fh);
	347
6e91ea2b CH	348	struct dentry exportfs_decode_fh(struct vfsmount mnt, struct fid *fid,
	349	int fh_len, int fileid_type,
	350	int (acceptable)(void , struct dentry ), void context)
d37065cd	351	{
39655164	352	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
2596110a CH	353	struct dentry result, alias;
2596110a CH	354	int err;
d37065cd	355
2596110a CH	356	/*
	357	* Try to get any dentry for the given file handle from the filesystem.
	358	*/
	359	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
	360	if (!result)
	361	result = ERR_PTR(-ESTALE);
	362	if (IS_ERR(result))
	363	return result;
	364
	365	if (S_ISDIR(result->d_inode->i_mode)) {
	366	/*
	367	* This request is for a directory.
	368	*
	369	* On the positive side there is only one dentry for each
	370	* directory inode. On the negative side this implies that we
	371	* to ensure our dentry is connected all the way up to the
	372	* filesystem root.
	373	*/
	374	if (result->d_flags & DCACHE_DISCONNECTED) {
	375	err = reconnect_path(mnt->mnt_sb, result);
	376	if (err)
	377	goto err_result;
	378	}
	379
	380	if (!acceptable(context, result)) {
	381	err = -EACCES;
	382	goto err_result;
	383	}
	384
	385	return result;
10f11c34	386	} else {
2596110a CH	387	/*
	388	* It's not a directory. Life is a little more complicated.
	389	*/
	390	struct dentry target_dir, nresult;
	391	char nbuf[NAME_MAX+1];
	392
	393	/*
	394	* See if either the dentry we just got from the filesystem
	395	* or any alias for it is acceptable. This is always true
	396	* if this filesystem is exported without the subtreecheck
	397	* option. If the filesystem is exported with the subtree
	398	* check option there's a fair chance we need to look at
	399	* the parent directory in the file handle and make sure
	400	* it's connected to the filesystem root.
	401	*/
	402	alias = find_acceptable_alias(result, acceptable, context);
	403	if (alias)
	404	return alias;
	405
	406	/*
	407	* Try to extract a dentry for the parent directory from the
	408	* file handle. If this fails we'll have to give up.
	409	*/
	410	err = -ESTALE;
	411	if (!nop->fh_to_parent)
	412	goto err_result;
	413
	414	target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
	415	fh_len, fileid_type);
	416	if (!target_dir)
	417	goto err_result;
	418	err = PTR_ERR(target_dir);
	419	if (IS_ERR(target_dir))
	420	goto err_result;
	421
	422	/*
	423	* And as usual we need to make sure the parent directory is
	424	* connected to the filesystem root. The VFS really doesn't
	425	* like disconnected directories..
	426	*/
	427	err = reconnect_path(mnt->mnt_sb, target_dir);
	428	if (err) {
	429	dput(target_dir);
	430	goto err_result;
	431	}
	432
	433	/*
	434	* Now that we've got both a well-connected parent and a
	435	* dentry for the inode we're after, make sure that our
	436	* inode is actually connected to the parent.
	437	*/
	438	err = exportfs_get_name(target_dir, nbuf, result);
	439	if (!err) {
	440	mutex_lock(&target_dir->d_inode->i_mutex);
	441	nresult = lookup_one_len(nbuf, target_dir,
	442	strlen(nbuf));
	443	mutex_unlock(&target_dir->d_inode->i_mutex);
	444	if (!IS_ERR(nresult)) {
	445	if (nresult->d_inode) {
	446	dput(result);
	447	result = nresult;
	448	} else
	449	dput(nresult);
	450	}
451	}
452
453	/*
454	* At this point we are done with the parent, but it's pinned
455	* by the child dentry anyway.
456	*/
457	dput(target_dir);
458
459	/*
460	* And finally make sure the dentry is actually acceptable
461	* to NFSD.
462	*/
463	alias = find_acceptable_alias(result, acceptable, context);
464	if (!alias) {
465	err = -EACCES;
466	goto err_result;
467	}
468
469	return alias;
10f11c34 CH	470	}
10f11c34 CH	471
2596110a CH	472	err_result:
	473	dput(result);
	474	return ERR_PTR(err);
d37065cd CH	475	}
	476	EXPORT_SYMBOL_GPL(exportfs_decode_fh);
	477
1da177e4	478	MODULE_LICENSE("GPL");