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

/*
 * Copyright (C) Neil Brown 2002
 * Copyright (C) Christoph Hellwig 2007
 *
 * This file contains the code mapping from inodes to NFS file handles,
 * and for mapping back from file handles to dentries.
 *
 * For details on why we do all the strange and hairy things in here
 * take a look at Documentation/filesystems/Exporting.
 */
#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 vfsmount *mnt, struct dentry *dentry, char *name,
		struct dentry *child);


static int exportfs_get_name(struct vfsmount *mnt, 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(mnt, 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 vfsmount *mnt, struct dentry *target_dir, char *nbuf)
{
	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 == mnt->mnt_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 (mnt->mnt_sb->s_export_op->get_parent)
				ppd = mnt->mnt_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",
					__func__, pd->d_inode->i_ino, err);
				dput(pd);
				break;
			}

			dprintk("%s: find name of %lu in %lu\n", __func__,
				pd->d_inode->i_ino, ppd->d_inode->i_ino);
			err = exportfs_get_name(mnt, 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", __func__, 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",
					__func__, 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", __func__);
			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 vfsmount *mnt, 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), mntget(mnt), 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 (buffer.found) {
			error = 0;
			break;
		}

		if (error < 0)
			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;
	char nbuf[NAME_MAX+1];
	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, result, nbuf);
			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;

		/*
		 * 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, target_dir, nbuf);
		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(mnt, 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
e38f9817 CH	1	/*
	2	* Copyright (C) Neil Brown 2002
	3	* Copyright (C) Christoph Hellwig 2007
	4	*
	5	* This file contains the code mapping from inodes to NFS file handles,
	6	* and for mapping back from file handles to dentries.
	7	*
	8	* For details on why we do all the strange and hairy things in here
	9	* take a look at Documentation/filesystems/Exporting.
	10	*/
a5694255	11	#include <linux/exportfs.h>
1da177e4 LT	12	#include <linux/fs.h>
	13	#include <linux/file.h>
	14	#include <linux/module.h>
d37065cd	15	#include <linux/mount.h>
1da177e4 LT	16	#include <linux/namei.h>
1da177e4 LT	17
10f11c34	18	#define dprintk(fmt, args...) do{}while(0)
1da177e4	19
1da177e4	20
e38f9817	21	static int get_name(struct vfsmount mnt, struct dentry dentry, char *name,
10f11c34 CH	22	struct dentry *child);
	23
	24
e38f9817 CH	25	static int exportfs_get_name(struct vfsmount mnt, struct dentry dir,
e38f9817 CH	26	char name, struct dentry child)
10f11c34	27	{
39655164	28	const struct export_operations *nop = dir->d_sb->s_export_op;
10f11c34 CH	29
	30	if (nop->get_name)
	31	return nop->get_name(dir, name, child);
	32	else
e38f9817	33	return get_name(mnt, dir, name, child);
10f11c34	34	}
1da177e4	35
fb66a198 CH	36	/*
	37	* Check if the dentry or any of it's aliases is acceptable.
	38	*/
e2f99018 CH	39	static struct dentry *
	40	find_acceptable_alias(struct dentry *result,
	41	int (acceptable)(void context, struct dentry *dentry),
	42	void *context)
	43	{
	44	struct dentry dentry, toput = NULL;
	45
fb66a198 CH	46	if (acceptable(context, result))
	47	return result;
	48
e2f99018 CH	49	spin_lock(&dcache_lock);
	50	list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
	51	dget_locked(dentry);
	52	spin_unlock(&dcache_lock);
	53	if (toput)
	54	dput(toput);
	55	if (dentry != result && acceptable(context, dentry)) {
	56	dput(result);
	57	return dentry;
	58	}
	59	spin_lock(&dcache_lock);
	60	toput = dentry;
	61	}
	62	spin_unlock(&dcache_lock);
	63
	64	if (toput)
	65	dput(toput);
	66	return NULL;
	67	}
	68
dd90b509 CH	69	/*
	70	* Find root of a disconnected subtree and return a reference to it.
	71	*/
	72	static struct dentry *
	73	find_disconnected_root(struct dentry *dentry)
	74	{
	75	dget(dentry);
	76	spin_lock(&dentry->d_lock);
	77	while (!IS_ROOT(dentry) &&
	78	(dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) {
	79	struct dentry *parent = dentry->d_parent;
	80	dget(parent);
	81	spin_unlock(&dentry->d_lock);
	82	dput(dentry);
	83	dentry = parent;
	84	spin_lock(&dentry->d_lock);
	85	}
	86	spin_unlock(&dentry->d_lock);
	87	return dentry;
	88	}
	89
019ab801 CH	90
	91	/*
	92	* Make sure target_dir is fully connected to the dentry tree.
1da177e4	93	*
019ab801	94	* It may already be, as the flag isn't always updated when connection happens.
1da177e4	95	*/
019ab801	96	static int
f3f8e175	97	reconnect_path(struct vfsmount mnt, struct dentry target_dir, char *nbuf)
1da177e4	98	{
019ab801 CH	99	int noprogress = 0;
019ab801 CH	100	int err = -ESTALE;
1da177e4 LT	101
1da177e4 LT	102	/*
019ab801	103	* It is possible that a confused file system might not let us complete
1da177e4 LT	104	* the path to the root. For example, if get_parent returns a directory
	105	* in which we cannot find a name for the child. While this implies a
	106	* very sick filesystem we don't want it to cause knfsd to spin. Hence
	107	* the noprogress counter. If we go through the loop 10 times (2 is
	108	* probably enough) without getting anywhere, we just give up
	109	*/
1da177e4	110	while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
dd90b509	111	struct dentry *pd = find_disconnected_root(target_dir);
1da177e4 LT	112
	113	if (!IS_ROOT(pd)) {
	114	/* must have found a connected parent - great */
	115	spin_lock(&pd->d_lock);
	116	pd->d_flags &= ~DCACHE_DISCONNECTED;
	117	spin_unlock(&pd->d_lock);
	118	noprogress = 0;
e38f9817	119	} else if (pd == mnt->mnt_sb->s_root) {
1da177e4 LT	120	printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
	121	spin_lock(&pd->d_lock);
	122	pd->d_flags &= ~DCACHE_DISCONNECTED;
	123	spin_unlock(&pd->d_lock);
	124	noprogress = 0;
	125	} else {
10f11c34 CH	126	/*
	127	* We have hit the top of a disconnected path, try to
	128	* find parent and connect.
	129	*
	130	* Racing with some other process renaming a directory
	131	* isn't much of a problem here. If someone renames
	132	* the directory, it will end up properly connected,
	133	* which is what we want
	134	*
	135	* Getting the parent can't be supported generically,
	136	* the locking is too icky.
	137	*
	138	* Instead we just return EACCES. If server reboots
	139	* or inodes get flushed, you lose
1da177e4	140	*/
10f11c34	141	struct dentry *ppd = ERR_PTR(-EACCES);
1da177e4 LT	142	struct dentry *npd;
1da177e4 LT	143
1b1dcc1b	144	mutex_lock(&pd->d_inode->i_mutex);
e38f9817 CH	145	if (mnt->mnt_sb->s_export_op->get_parent)
e38f9817 CH	146	ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
1b1dcc1b	147	mutex_unlock(&pd->d_inode->i_mutex);
1da177e4 LT	148
	149	if (IS_ERR(ppd)) {
	150	err = PTR_ERR(ppd);
019ab801	151	dprintk("%s: get_parent of %ld failed, err %d\n",
8e24eea7	152	__func__, pd->d_inode->i_ino, err);
1da177e4 LT	153	dput(pd);
	154	break;
	155	}
019ab801	156
8e24eea7	157	dprintk("%s: find name of %lu in %lu\n", __func__,
019ab801	158	pd->d_inode->i_ino, ppd->d_inode->i_ino);
e38f9817	159	err = exportfs_get_name(mnt, ppd, nbuf, pd);
1da177e4 LT	160	if (err) {
	161	dput(ppd);
	162	dput(pd);
	163	if (err == -ENOENT)
	164	/* some race between get_parent and
	165	* get_name? just try again
	166	*/
	167	continue;
	168	break;
	169	}
8e24eea7	170	dprintk("%s: found name: %s\n", __func__, nbuf);
1b1dcc1b	171	mutex_lock(&ppd->d_inode->i_mutex);
1da177e4	172	npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
1b1dcc1b	173	mutex_unlock(&ppd->d_inode->i_mutex);
1da177e4 LT	174	if (IS_ERR(npd)) {
1da177e4 LT	175	err = PTR_ERR(npd);
019ab801	176	dprintk("%s: lookup failed: %d\n",
8e24eea7	177	__func__, err);
1da177e4 LT	178	dput(ppd);
	179	dput(pd);
	180	break;
	181	}
	182	/* we didn't really want npd, we really wanted
	183	* a side-effect of the lookup.
	184	* hopefully, npd == pd, though it isn't really
	185	* a problem if it isn't
	186	*/
	187	if (npd == pd)
	188	noprogress = 0;
	189	else
8e24eea7	190	printk("%s: npd != pd\n", __func__);
1da177e4 LT	191	dput(npd);
	192	dput(ppd);
	193	if (IS_ROOT(pd)) {
	194	/* something went wrong, we have to give up */
	195	dput(pd);
	196	break;
	197	}
	198	}
	199	dput(pd);
	200	}
	201
	202	if (target_dir->d_flags & DCACHE_DISCONNECTED) {
	203	/* something went wrong - oh-well */
	204	if (!err)
	205	err = -ESTALE;
019ab801	206	return err;
1da177e4	207	}
019ab801 CH	208
	209	return 0;
	210	}
	211
1da177e4 LT	212	struct getdents_callback {
	213	char name; / name that was found. It already points to a
	214	buffer NAME_MAX+1 is size */
	215	unsigned long ino; /* the inum we are looking for */
	216	int found; /* inode matched? */
	217	int sequence; /* sequence counter */
	218	};
	219
	220	/*
	221	* A rather strange filldir function to capture
	222	* the name matching the specified inode number.
	223	*/
	224	static int filldir_one(void * __buf, const char * name, int len,
afefdbb2	225	loff_t pos, u64 ino, unsigned int d_type)
1da177e4 LT	226	{
	227	struct getdents_callback *buf = __buf;
	228	int result = 0;
	229
	230	buf->sequence++;
	231	if (buf->ino == ino) {
	232	memcpy(buf->name, name, len);
	233	buf->name[len] = '\0';
	234	buf->found = 1;
	235	result = -1;
	236	}
	237	return result;
	238	}
	239
	240	/**
	241	* get_name - default export_operations->get_name function
	242	* @dentry: the directory in which to find a name
	243	* @name: a pointer to a %NAME_MAX+1 char buffer to store the name
	244	* @child: the dentry for the child directory.
	245	*
	246	* calls readdir on the parent until it finds an entry with
	247	* the same inode number as the child, and returns that.
	248	*/
e38f9817 CH	249	static int get_name(struct vfsmount mnt, struct dentry dentry,
e38f9817 CH	250	char name, struct dentry child)
1da177e4 LT	251	{
	252	struct inode *dir = dentry->d_inode;
	253	int error;
	254	struct file *file;
	255	struct getdents_callback buffer;
	256
	257	error = -ENOTDIR;
	258	if (!dir \|\| !S_ISDIR(dir->i_mode))
	259	goto out;
	260	error = -EINVAL;
	261	if (!dir->i_fop)
	262	goto out;
	263	/*
	264	* Open the directory ...
	265	*/
e38f9817	266	file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY);
1da177e4 LT	267	error = PTR_ERR(file);
	268	if (IS_ERR(file))
	269	goto out;
	270
	271	error = -EINVAL;
	272	if (!file->f_op->readdir)
	273	goto out_close;
	274
	275	buffer.name = name;
	276	buffer.ino = child->d_inode->i_ino;
	277	buffer.found = 0;
	278	buffer.sequence = 0;
	279	while (1) {
	280	int old_seq = buffer.sequence;
	281
	282	error = vfs_readdir(file, filldir_one, &buffer);
53c9c5c0 AV	283	if (buffer.found) {
	284	error = 0;
	285	break;
	286	}
1da177e4 LT	287
	288	if (error < 0)
	289	break;
	290
1da177e4 LT	291	error = -ENOENT;
	292	if (old_seq == buffer.sequence)
	293	break;
	294	}
	295
	296	out_close:
	297	fput(file);
	298	out:
	299	return error;
	300	}
	301
1da177e4 LT	302	/**
	303	* export_encode_fh - default export_operations->encode_fh function
	304	* @dentry: the dentry to encode
	305	* @fh: where to store the file handle fragment
	306	* @max_len: maximum length to store there
	307	* @connectable: whether to store parent information
	308	*
	309	* This default encode_fh function assumes that the 32 inode number
	310	* is suitable for locating an inode, and that the generation number
	311	* can be used to check that it is still valid. It places them in the
	312	* filehandle fragment where export_decode_fh expects to find them.
	313	*/
6e91ea2b CH	314	static int export_encode_fh(struct dentry dentry, struct fid fid,
6e91ea2b CH	315	int *max_len, int connectable)
1da177e4 LT	316	{
	317	struct inode * inode = dentry->d_inode;
	318	int len = *max_len;
6e91ea2b	319	int type = FILEID_INO32_GEN;
1da177e4 LT	320
	321	if (len < 2 \|\| (connectable && len < 4))
	322	return 255;
	323
	324	len = 2;
6e91ea2b CH	325	fid->i32.ino = inode->i_ino;
6e91ea2b CH	326	fid->i32.gen = inode->i_generation;
1da177e4 LT	327	if (connectable && !S_ISDIR(inode->i_mode)) {
	328	struct inode *parent;
	329
	330	spin_lock(&dentry->d_lock);
	331	parent = dentry->d_parent->d_inode;
6e91ea2b CH	332	fid->i32.parent_ino = parent->i_ino;
6e91ea2b CH	333	fid->i32.parent_gen = parent->i_generation;
1da177e4 LT	334	spin_unlock(&dentry->d_lock);
1da177e4 LT	335	len = 4;
6e91ea2b	336	type = FILEID_INO32_GEN_PARENT;
1da177e4 LT	337	}
	338	*max_len = len;
	339	return type;
	340	}
	341
6e91ea2b	342	int exportfs_encode_fh(struct dentry dentry, struct fid fid, int *max_len,
d37065cd CH	343	int connectable)
d37065cd CH	344	{
39655164	345	const struct export_operations *nop = dentry->d_sb->s_export_op;
10f11c34	346	int error;
d37065cd	347
10f11c34	348	if (nop->encode_fh)
6e91ea2b	349	error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
10f11c34	350	else
6e91ea2b	351	error = export_encode_fh(dentry, fid, max_len, connectable);
10f11c34 CH	352
10f11c34 CH	353	return error;
d37065cd CH	354	}
	355	EXPORT_SYMBOL_GPL(exportfs_encode_fh);
	356
6e91ea2b CH	357	struct dentry exportfs_decode_fh(struct vfsmount mnt, struct fid *fid,
	358	int fh_len, int fileid_type,
	359	int (acceptable)(void , struct dentry ), void context)
d37065cd	360	{
39655164	361	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
2596110a	362	struct dentry result, alias;
f3f8e175	363	char nbuf[NAME_MAX+1];
2596110a	364	int err;
d37065cd	365
2596110a CH	366	/*
	367	* Try to get any dentry for the given file handle from the filesystem.
	368	*/
	369	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
a4f4d6df BF	370	if (!result)
a4f4d6df BF	371	result = ERR_PTR(-ESTALE);
2596110a CH	372	if (IS_ERR(result))
	373	return result;
	374
	375	if (S_ISDIR(result->d_inode->i_mode)) {
	376	/*
	377	* This request is for a directory.
	378	*
	379	* On the positive side there is only one dentry for each
	380	* directory inode. On the negative side this implies that we
	381	* to ensure our dentry is connected all the way up to the
	382	* filesystem root.
	383	*/
	384	if (result->d_flags & DCACHE_DISCONNECTED) {
f3f8e175	385	err = reconnect_path(mnt, result, nbuf);
2596110a CH	386	if (err)
	387	goto err_result;
	388	}
	389
	390	if (!acceptable(context, result)) {
	391	err = -EACCES;
	392	goto err_result;
	393	}
	394
	395	return result;
10f11c34	396	} else {
2596110a CH	397	/*
	398	* It's not a directory. Life is a little more complicated.
	399	*/
	400	struct dentry target_dir, nresult;
2596110a CH	401
	402	/*
	403	* See if either the dentry we just got from the filesystem
	404	* or any alias for it is acceptable. This is always true
	405	* if this filesystem is exported without the subtreecheck
	406	* option. If the filesystem is exported with the subtree
	407	* check option there's a fair chance we need to look at
	408	* the parent directory in the file handle and make sure
	409	* it's connected to the filesystem root.
	410	*/
	411	alias = find_acceptable_alias(result, acceptable, context);
	412	if (alias)
	413	return alias;
	414
	415	/*
	416	* Try to extract a dentry for the parent directory from the
	417	* file handle. If this fails we'll have to give up.
	418	*/
	419	err = -ESTALE;
	420	if (!nop->fh_to_parent)
	421	goto err_result;
	422
	423	target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
	424	fh_len, fileid_type);
a4f4d6df BF	425	if (!target_dir)
a4f4d6df BF	426	goto err_result;
2596110a CH	427	err = PTR_ERR(target_dir);
	428	if (IS_ERR(target_dir))
	429	goto err_result;
	430
	431	/*
	432	* And as usual we need to make sure the parent directory is
	433	* connected to the filesystem root. The VFS really doesn't
	434	* like disconnected directories..
	435	*/
f3f8e175	436	err = reconnect_path(mnt, target_dir, nbuf);
2596110a CH	437	if (err) {
	438	dput(target_dir);
	439	goto err_result;
	440	}
	441
	442	/*
	443	* Now that we've got both a well-connected parent and a
	444	* dentry for the inode we're after, make sure that our
	445	* inode is actually connected to the parent.
	446	*/
e38f9817	447	err = exportfs_get_name(mnt, target_dir, nbuf, result);
2596110a CH	448	if (!err) {
	449	mutex_lock(&target_dir->d_inode->i_mutex);
	450	nresult = lookup_one_len(nbuf, target_dir,
	451	strlen(nbuf));
	452	mutex_unlock(&target_dir->d_inode->i_mutex);
	453	if (!IS_ERR(nresult)) {
	454	if (nresult->d_inode) {
	455	dput(result);
	456	result = nresult;
	457	} else
	458	dput(nresult);
	459	}
	460	}
	461
	462	/*
	463	* At this point we are done with the parent, but it's pinned
	464	* by the child dentry anyway.
	465	*/
	466	dput(target_dir);
	467
	468	/*
	469	* And finally make sure the dentry is actually acceptable
	470	* to NFSD.
	471	*/
	472	alias = find_acceptable_alias(result, acceptable, context);
	473	if (!alias) {
	474	err = -EACCES;
	475	goto err_result;
	476	}
	477
	478	return alias;
10f11c34 CH	479	}
10f11c34 CH	480
2596110a CH	481	err_result:
	482	dput(result);
	483	return ERR_PTR(err);
d37065cd CH	484	}
	485	EXPORT_SYMBOL_GPL(exportfs_decode_fh);
	486
1da177e4	487	MODULE_LICENSE("GPL");