fs/exportfs/expfs.c - kernel/mindspeed - Git at Google

 /*
  * 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/nfs/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>
 #include <linux/sched.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;
 	struct inode *inode;

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

 	inode = result->d_inode;
 	spin_lock(&inode->i_lock);
 	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
 		dget(dentry);
 		spin_unlock(&inode->i_lock);
 		if (toput)
 			dput(toput);
 		if (dentry != result && acceptable(context, dentry)) {
 			dput(result);
 			return dentry;
 		}
 		spin_lock(&inode->i_lock);
 		toput = dentry;
 	}
 	spin_unlock(&inode->i_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);
 	while (!IS_ROOT(dentry)) {
 		struct dentry *parent = dget_parent(dentry);

 		if (!(parent->d_flags & DCACHE_DISCONNECTED)) {
 			dput(parent);
 			break;
 		}

 		dput(dentry);
 		dentry = parent;
 	}
 	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)
 {
 	const struct cred *cred = current_cred();
 	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, cred);
 	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 (connectable && (len < 4)) {
 		*max_len = 4;
 		return 255;
 	} else if (len < 2) {
 		*max_len = 2;
 		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.
 	 */
 	if (!nop || !nop->fh_to_dentry)
 		return ERR_PTR(-ESTALE);
 	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");
	/*
	* 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/nfs/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>
	#include <linux/sched.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;
	struct inode *inode;

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

	inode = result->d_inode;
	spin_lock(&inode->i_lock);
	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
	dget(dentry);
	spin_unlock(&inode->i_lock);
	if (toput)
	dput(toput);
	if (dentry != result && acceptable(context, dentry)) {
	dput(result);
	return dentry;
	}
	spin_lock(&inode->i_lock);
	toput = dentry;
	}
	spin_unlock(&inode->i_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);
	while (!IS_ROOT(dentry)) {
	struct dentry *parent = dget_parent(dentry);

	if (!(parent->d_flags & DCACHE_DISCONNECTED)) {
	dput(parent);
	break;
	}

	dput(dentry);
	dentry = parent;
	}
	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)
	{
	const struct cred *cred = current_cred();
	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, cred);
	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 (connectable && (len < 4)) {
	*max_len = 4;
	return 255;
	} else if (len < 2) {
	*max_len = 2;
	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.
	*/
	if (!nop \|\| !nop->fh_to_dentry)
	return ERR_PTR(-ESTALE);
	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");