fs/nfs/namespace.c - kernel/msm-4.9 - Gitiles

 /*
  * linux/fs/nfs/namespace.c
  *
  * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
  * - Modified by David Howells <dhowells@redhat.com>
  *
  * NFS namespace
  */

 #include <linux/dcache.h>
 #include <linux/gfp.h>
 #include <linux/mount.h>
 #include <linux/namei.h>
 #include <linux/nfs_fs.h>
 #include <linux/string.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/vfs.h>
 #include <linux/sunrpc/gss_api.h>
 #include "internal.h"

 #define NFSDBG_FACILITY		NFSDBG_VFS

 static void nfs_expire_automounts(struct work_struct *work);

 static LIST_HEAD(nfs_automount_list);
 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
 int nfs_mountpoint_expiry_timeout = 500 * HZ;

 static struct vfsmount *nfs_do_submount(struct dentry *dentry,
 					struct nfs_fh *fh,
 					struct nfs_fattr *fattr,
 					rpc_authflavor_t authflavor);

 /*
  * nfs_path - reconstruct the path given an arbitrary dentry
  * @base - used to return pointer to the end of devname part of path
  * @dentry - pointer to dentry
  * @buffer - result buffer
  * @buflen - length of buffer
  *
  * Helper function for constructing the server pathname
  * by arbitrary hashed dentry.
  *
  * This is mainly for use in figuring out the path on the
  * server side when automounting on top of an existing partition
  * and in generating /proc/mounts and friends.
  */
 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
 {
 	char *end;
 	int namelen;
 	unsigned seq;
 	const char *base;

 rename_retry:
 	end = buffer+buflen;
 	*--end = '\0';
 	buflen--;

 	seq = read_seqbegin(&rename_lock);
 	rcu_read_lock();
 	while (1) {
 		spin_lock(&dentry->d_lock);
 		if (IS_ROOT(dentry))
 			break;
 		namelen = dentry->d_name.len;
 		buflen -= namelen + 1;
 		if (buflen < 0)
 			goto Elong_unlock;
 		end -= namelen;
 		memcpy(end, dentry->d_name.name, namelen);
 		*--end = '/';
 		spin_unlock(&dentry->d_lock);
 		dentry = dentry->d_parent;
 	}
 	if (read_seqretry(&rename_lock, seq)) {
 		spin_unlock(&dentry->d_lock);
 		rcu_read_unlock();
 		goto rename_retry;
 	}
 	if (*end != '/') {
 		if (--buflen < 0) {
 			spin_unlock(&dentry->d_lock);
 			rcu_read_unlock();
 			goto Elong;
 		}
 		*--end = '/';
 	}
 	*p = end;
 	base = dentry->d_fsdata;
 	if (!base) {
 		spin_unlock(&dentry->d_lock);
 		rcu_read_unlock();
 		WARN_ON(1);
 		return end;
 	}
 	namelen = strlen(base);
 	/* Strip off excess slashes in base string */
 	while (namelen > 0 && base[namelen - 1] == '/')
 		namelen--;
 	buflen -= namelen;
 	if (buflen < 0) {
 		spin_unlock(&dentry->d_lock);
 		rcu_read_unlock();
 		goto Elong;
 	}
 	end -= namelen;
 	memcpy(end, base, namelen);
 	spin_unlock(&dentry->d_lock);
 	rcu_read_unlock();
 	return end;
 Elong_unlock:
 	spin_unlock(&dentry->d_lock);
 	rcu_read_unlock();
 	if (read_seqretry(&rename_lock, seq))
 		goto rename_retry;
 Elong:
 	return ERR_PTR(-ENAMETOOLONG);
 }

 #ifdef CONFIG_NFS_V4
 rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
 {
 	struct gss_api_mech *mech;
 	struct xdr_netobj oid;
 	int i;
 	rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;

 	for (i = 0; i < flavors->num_flavors; i++) {
 		struct nfs4_secinfo_flavor *flavor;
 		flavor = &flavors->flavors[i];

 		if (flavor->flavor == RPC_AUTH_NULL || flavor->flavor == RPC_AUTH_UNIX) {
 			pseudoflavor = flavor->flavor;
 			break;
 		} else if (flavor->flavor == RPC_AUTH_GSS) {
 			oid.len  = flavor->gss.sec_oid4.len;
 			oid.data = flavor->gss.sec_oid4.data;
 			mech = gss_mech_get_by_OID(&oid);
 			if (!mech)
 				continue;
 			pseudoflavor = gss_svc_to_pseudoflavor(mech, flavor->gss.service);
 			gss_mech_put(mech);
 			break;
 		}
 	}

 	return pseudoflavor;
 }

 static int nfs_negotiate_security(const struct dentry *parent,
 				  const struct dentry *dentry,
 				  rpc_authflavor_t *flavor)
 {
 	struct page *page;
 	struct nfs4_secinfo_flavors *flavors;
 	int (*secinfo)(struct inode *, const struct qstr *, struct nfs4_secinfo_flavors *);
 	int ret = -EPERM;

 	secinfo = NFS_PROTO(parent->d_inode)->secinfo;
 	if (secinfo != NULL) {
 		page = alloc_page(GFP_KERNEL);
 		if (!page) {
 			ret = -ENOMEM;
 			goto out;
 		}
 		flavors = page_address(page);
 		ret = secinfo(parent->d_inode, &dentry->d_name, flavors);
 		*flavor = nfs_find_best_sec(flavors);
 		put_page(page);
 	}

 out:
 	return ret;
 }

 static int nfs_lookup_with_sec(struct nfs_server *server, struct dentry *parent,
 			       struct dentry *dentry, struct path *path,
 			       struct nfs_fh *fh, struct nfs_fattr *fattr,
 			       rpc_authflavor_t *flavor)
 {
 	struct rpc_clnt *clone;
 	struct rpc_auth *auth;
 	int err;

 	err = nfs_negotiate_security(parent, path->dentry, flavor);
 	if (err < 0)
 		goto out;
 	clone  = rpc_clone_client(server->client);
 	auth   = rpcauth_create(*flavor, clone);
 	if (!auth) {
 		err = -EIO;
 		goto out_shutdown;
 	}
 	err = server->nfs_client->rpc_ops->lookup(clone, parent->d_inode,
 						  &path->dentry->d_name,
 						  fh, fattr);
 out_shutdown:
 	rpc_shutdown_client(clone);
 out:
 	return err;
 }

 static struct rpc_clnt *nfs_lookup_mountpoint(struct inode *dir,
 					      struct qstr *name,
 					      struct nfs_fh *fh,
 					      struct nfs_fattr *fattr)
 {
 	int err;

 	if (NFS_PROTO(dir)->version == 4)
 		return nfs4_proc_lookup_mountpoint(dir, name, fh, fattr);

 	err = NFS_PROTO(dir)->lookup(NFS_SERVER(dir)->client, dir, name, fh, fattr);
 	if (err)
 		return ERR_PTR(err);
 	return rpc_clone_client(NFS_SERVER(dir)->client);
 }
 #else /* CONFIG_NFS_V4 */
 static inline int nfs_lookup_with_sec(struct nfs_server *server,
 				      struct dentry *parent, struct dentry *dentry,
 				      struct path *path, struct nfs_fh *fh,
 				      struct nfs_fattr *fattr,
 				      rpc_authflavor_t *flavor)
 {
 	return -EPERM;
 }

 static inline struct rpc_clnt *nfs_lookup_mountpoint(struct inode *dir,
 						     struct qstr *name,
 						     struct nfs_fh *fh,
 						     struct nfs_fattr *fattr)
 {
 	int err = NFS_PROTO(dir)->lookup(NFS_SERVER(dir)->client, dir, name, fh, fattr);
 	if (err)
 		return ERR_PTR(err);
 	return rpc_clone_client(NFS_SERVER(dir)->client);
 }
 #endif /* CONFIG_NFS_V4 */

 /*
  * nfs_d_automount - Handle crossing a mountpoint on the server
  * @path - The mountpoint
  *
  * When we encounter a mountpoint on the server, we want to set up
  * a mountpoint on the client too, to prevent inode numbers from
  * colliding, and to allow "df" to work properly.
  * On NFSv4, we also want to allow for the fact that different
  * filesystems may be migrated to different servers in a failover
  * situation, and that different filesystems may want to use
  * different security flavours.
  */
 struct vfsmount *nfs_d_automount(struct path *path)
 {
 	struct vfsmount *mnt;
 	struct dentry *parent;
 	struct nfs_fh *fh = NULL;
 	struct nfs_fattr *fattr = NULL;
 	struct rpc_clnt *client;
 	rpc_authflavor_t flavor = RPC_AUTH_UNIX;

 	dprintk("--> nfs_d_automount()\n");

 	mnt = ERR_PTR(-ESTALE);
 	if (IS_ROOT(path->dentry))
 		goto out_nofree;

 	mnt = ERR_PTR(-ENOMEM);
 	fh = nfs_alloc_fhandle();
 	fattr = nfs_alloc_fattr();
 	if (fh == NULL || fattr == NULL)
 		goto out;

 	dprintk("%s: enter\n", __func__);

 	/* Look it up again to get its attributes */
 	parent = dget_parent(path->dentry);
 	client = nfs_lookup_mountpoint(parent->d_inode, &path->dentry->d_name, fh, fattr);
 	dput(parent);
 	if (IS_ERR(client)) {
 		mnt = ERR_CAST(client);
 		goto out;
 	}

 	if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
 		mnt = nfs_do_refmount(client, path->dentry);
 	else
 		mnt = nfs_do_submount(path->dentry, fh, fattr, flavor);
 	rpc_shutdown_client(client);

 	if (IS_ERR(mnt))
 		goto out;

 	dprintk("%s: done, success\n", __func__);
 	mntget(mnt); /* prevent immediate expiration */
 	mnt_set_expiry(mnt, &nfs_automount_list);
 	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);

 out:
 	nfs_free_fattr(fattr);
 	nfs_free_fhandle(fh);
 out_nofree:
 	if (IS_ERR(mnt))
 		dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt));
 	else
 		dprintk("<-- %s() = %p\n", __func__, mnt);
 	return mnt;
 }

 const struct inode_operations nfs_mountpoint_inode_operations = {
 	.getattr	= nfs_getattr,
 };

 const struct inode_operations nfs_referral_inode_operations = {
 };

 static void nfs_expire_automounts(struct work_struct *work)
 {
 	struct list_head *list = &nfs_automount_list;

 	mark_mounts_for_expiry(list);
 	if (!list_empty(list))
 		schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 }

 void nfs_release_automount_timer(void)
 {
 	if (list_empty(&nfs_automount_list))
 		cancel_delayed_work(&nfs_automount_task);
 }

 /*
  * Clone a mountpoint of the appropriate type
  */
 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 					   const char *devname,
 					   struct nfs_clone_mount *mountdata)
 {
 #ifdef CONFIG_NFS_V4
 	struct vfsmount *mnt = ERR_PTR(-EINVAL);
 	switch (server->nfs_client->rpc_ops->version) {
 		case 2:
 		case 3:
 			mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 			break;
 		case 4:
 			mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
 	}
 	return mnt;
 #else
 	return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 #endif
 }

 /**
  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
  * @dentry - parent directory
  * @fh - filehandle for new root dentry
  * @fattr - attributes for new root inode
  * @authflavor - security flavor to use when performing the mount
  *
  */
 static struct vfsmount *nfs_do_submount(struct dentry *dentry,
 					struct nfs_fh *fh,
 					struct nfs_fattr *fattr,
 					rpc_authflavor_t authflavor)
 {
 	struct nfs_clone_mount mountdata = {
 		.sb = dentry->d_sb,
 		.dentry = dentry,
 		.fh = fh,
 		.fattr = fattr,
 		.authflavor = authflavor,
 	};
 	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 	char *page = (char *) __get_free_page(GFP_USER);
 	char *devname;

 	dprintk("--> nfs_do_submount()\n");

 	dprintk("%s: submounting on %s/%s\n", __func__,
 			dentry->d_parent->d_name.name,
 			dentry->d_name.name);
 	if (page == NULL)
 		goto out;
 	devname = nfs_devname(dentry, page, PAGE_SIZE);
 	mnt = (struct vfsmount *)devname;
 	if (IS_ERR(devname))
 		goto free_page;
 	mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
 free_page:
 	free_page((unsigned long)page);
 out:
 	dprintk("%s: done\n", __func__);

 	dprintk("<-- nfs_do_submount() = %p\n", mnt);
 	return mnt;
 }
	/*
	* linux/fs/nfs/namespace.c
	*
	* Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
	* - Modified by David Howells <dhowells@redhat.com>
	*
	* NFS namespace
	*/

	#include <linux/dcache.h>
	#include <linux/gfp.h>
	#include <linux/mount.h>
	#include <linux/namei.h>
	#include <linux/nfs_fs.h>
	#include <linux/string.h>
	#include <linux/sunrpc/clnt.h>
	#include <linux/vfs.h>
	#include <linux/sunrpc/gss_api.h>
	#include "internal.h"

	#define NFSDBG_FACILITY NFSDBG_VFS

	static void nfs_expire_automounts(struct work_struct *work);

	static LIST_HEAD(nfs_automount_list);
	static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
	int nfs_mountpoint_expiry_timeout = 500 * HZ;

	static struct vfsmount nfs_do_submount(struct dentry dentry,
	struct nfs_fh *fh,
	struct nfs_fattr *fattr,
	rpc_authflavor_t authflavor);

	/*
	* nfs_path - reconstruct the path given an arbitrary dentry
	* @base - used to return pointer to the end of devname part of path
	* @dentry - pointer to dentry
	* @buffer - result buffer
	* @buflen - length of buffer
	*
	* Helper function for constructing the server pathname
	* by arbitrary hashed dentry.
	*
	* This is mainly for use in figuring out the path on the
	* server side when automounting on top of an existing partition
	* and in generating /proc/mounts and friends.
	*/
	char nfs_path(char p, struct dentry dentry, char *buffer, ssize_t buflen)
	{
	char *end;
	int namelen;
	unsigned seq;
	const char *base;

	rename_retry:
	end = buffer+buflen;
	*--end = '\0';
	buflen--;

	seq = read_seqbegin(&rename_lock);
	rcu_read_lock();
	while (1) {
	spin_lock(&dentry->d_lock);
	if (IS_ROOT(dentry))
	break;
	namelen = dentry->d_name.len;
	buflen -= namelen + 1;
	if (buflen < 0)
	goto Elong_unlock;
	end -= namelen;
	memcpy(end, dentry->d_name.name, namelen);
	*--end = '/';
	spin_unlock(&dentry->d_lock);
	dentry = dentry->d_parent;
	}
	if (read_seqretry(&rename_lock, seq)) {
	spin_unlock(&dentry->d_lock);
	rcu_read_unlock();
	goto rename_retry;
	}
	if (*end != '/') {
	if (--buflen < 0) {
	spin_unlock(&dentry->d_lock);
	rcu_read_unlock();
	goto Elong;
	}
	*--end = '/';
	}
	*p = end;
	base = dentry->d_fsdata;
	if (!base) {
	spin_unlock(&dentry->d_lock);
	rcu_read_unlock();
	WARN_ON(1);
	return end;
	}
	namelen = strlen(base);
	/* Strip off excess slashes in base string */
	while (namelen > 0 && base[namelen - 1] == '/')
	namelen--;
	buflen -= namelen;
	if (buflen < 0) {
	spin_unlock(&dentry->d_lock);
	rcu_read_unlock();
	goto Elong;
	}
	end -= namelen;
	memcpy(end, base, namelen);
	spin_unlock(&dentry->d_lock);
	rcu_read_unlock();
	return end;
	Elong_unlock:
	spin_unlock(&dentry->d_lock);
	rcu_read_unlock();
	if (read_seqretry(&rename_lock, seq))
	goto rename_retry;
	Elong:
	return ERR_PTR(-ENAMETOOLONG);
	}

	#ifdef CONFIG_NFS_V4
	rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
	{
	struct gss_api_mech *mech;
	struct xdr_netobj oid;
	int i;
	rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;

	for (i = 0; i < flavors->num_flavors; i++) {
	struct nfs4_secinfo_flavor *flavor;
	flavor = &flavors->flavors[i];

	if (flavor->flavor == RPC_AUTH_NULL \|\| flavor->flavor == RPC_AUTH_UNIX) {
	pseudoflavor = flavor->flavor;
	break;
	} else if (flavor->flavor == RPC_AUTH_GSS) {
	oid.len = flavor->gss.sec_oid4.len;
	oid.data = flavor->gss.sec_oid4.data;
	mech = gss_mech_get_by_OID(&oid);
	if (!mech)
	continue;
	pseudoflavor = gss_svc_to_pseudoflavor(mech, flavor->gss.service);
	gss_mech_put(mech);
	break;
	}
	}

	return pseudoflavor;
	}

	static int nfs_negotiate_security(const struct dentry *parent,
	const struct dentry *dentry,
	rpc_authflavor_t *flavor)
	{
	struct page *page;
	struct nfs4_secinfo_flavors *flavors;
	int (secinfo)(struct inode , const struct qstr , struct nfs4_secinfo_flavors );
	int ret = -EPERM;

	secinfo = NFS_PROTO(parent->d_inode)->secinfo;
	if (secinfo != NULL) {
	page = alloc_page(GFP_KERNEL);
	if (!page) {
	ret = -ENOMEM;
	goto out;
	}
	flavors = page_address(page);
	ret = secinfo(parent->d_inode, &dentry->d_name, flavors);
	*flavor = nfs_find_best_sec(flavors);
	put_page(page);
	}

	out:
	return ret;
	}

	static int nfs_lookup_with_sec(struct nfs_server server, struct dentry parent,
	struct dentry dentry, struct path path,
	struct nfs_fh fh, struct nfs_fattr fattr,
	rpc_authflavor_t *flavor)
	{
	struct rpc_clnt *clone;
	struct rpc_auth *auth;
	int err;

	err = nfs_negotiate_security(parent, path->dentry, flavor);
	if (err < 0)
	goto out;
	clone = rpc_clone_client(server->client);
	auth = rpcauth_create(*flavor, clone);
	if (!auth) {
	err = -EIO;
	goto out_shutdown;
	}
	err = server->nfs_client->rpc_ops->lookup(clone, parent->d_inode,
	&path->dentry->d_name,
	fh, fattr);
	out_shutdown:
	rpc_shutdown_client(clone);
	out:
	return err;
	}

	static struct rpc_clnt nfs_lookup_mountpoint(struct inode dir,
	struct qstr *name,
	struct nfs_fh *fh,
	struct nfs_fattr *fattr)
	{
	int err;

	if (NFS_PROTO(dir)->version == 4)
	return nfs4_proc_lookup_mountpoint(dir, name, fh, fattr);

	err = NFS_PROTO(dir)->lookup(NFS_SERVER(dir)->client, dir, name, fh, fattr);
	if (err)
	return ERR_PTR(err);
	return rpc_clone_client(NFS_SERVER(dir)->client);
	}
	#else /* CONFIG_NFS_V4 */
	static inline int nfs_lookup_with_sec(struct nfs_server *server,
	struct dentry parent, struct dentry dentry,
	struct path path, struct nfs_fh fh,
	struct nfs_fattr *fattr,
	rpc_authflavor_t *flavor)
	{
	return -EPERM;
	}

	static inline struct rpc_clnt nfs_lookup_mountpoint(struct inode dir,
	struct qstr *name,
	struct nfs_fh *fh,
	struct nfs_fattr *fattr)
	{
	int err = NFS_PROTO(dir)->lookup(NFS_SERVER(dir)->client, dir, name, fh, fattr);
	if (err)
	return ERR_PTR(err);
	return rpc_clone_client(NFS_SERVER(dir)->client);
	}
	#endif /* CONFIG_NFS_V4 */

	/*
	* nfs_d_automount - Handle crossing a mountpoint on the server
	* @path - The mountpoint
	*
	* When we encounter a mountpoint on the server, we want to set up
	* a mountpoint on the client too, to prevent inode numbers from
	* colliding, and to allow "df" to work properly.
	* On NFSv4, we also want to allow for the fact that different
	* filesystems may be migrated to different servers in a failover
	* situation, and that different filesystems may want to use
	* different security flavours.
	*/
	struct vfsmount nfs_d_automount(struct path path)
	{
	struct vfsmount *mnt;
	struct dentry *parent;
	struct nfs_fh *fh = NULL;
	struct nfs_fattr *fattr = NULL;
	struct rpc_clnt *client;
	rpc_authflavor_t flavor = RPC_AUTH_UNIX;

	dprintk("--> nfs_d_automount()\n");

	mnt = ERR_PTR(-ESTALE);
	if (IS_ROOT(path->dentry))
	goto out_nofree;

	mnt = ERR_PTR(-ENOMEM);
	fh = nfs_alloc_fhandle();
	fattr = nfs_alloc_fattr();
	if (fh == NULL \|\| fattr == NULL)
	goto out;

	dprintk("%s: enter\n", __func__);

	/* Look it up again to get its attributes */
	parent = dget_parent(path->dentry);
	client = nfs_lookup_mountpoint(parent->d_inode, &path->dentry->d_name, fh, fattr);
	dput(parent);
	if (IS_ERR(client)) {
	mnt = ERR_CAST(client);
	goto out;
	}

	if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
	mnt = nfs_do_refmount(client, path->dentry);
	else
	mnt = nfs_do_submount(path->dentry, fh, fattr, flavor);
	rpc_shutdown_client(client);

	if (IS_ERR(mnt))
	goto out;

	dprintk("%s: done, success\n", __func__);
	mntget(mnt); /* prevent immediate expiration */
	mnt_set_expiry(mnt, &nfs_automount_list);
	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);

	out:
	nfs_free_fattr(fattr);
	nfs_free_fhandle(fh);
	out_nofree:
	if (IS_ERR(mnt))
	dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt));
	else
	dprintk("<-- %s() = %p\n", __func__, mnt);
	return mnt;
	}

	const struct inode_operations nfs_mountpoint_inode_operations = {
	.getattr = nfs_getattr,
	};

	const struct inode_operations nfs_referral_inode_operations = {
	};

	static void nfs_expire_automounts(struct work_struct *work)
	{
	struct list_head *list = &nfs_automount_list;

	mark_mounts_for_expiry(list);
	if (!list_empty(list))
	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
	}

	void nfs_release_automount_timer(void)
	{
	if (list_empty(&nfs_automount_list))
	cancel_delayed_work(&nfs_automount_task);
	}

	/*
	* Clone a mountpoint of the appropriate type
	*/
	static struct vfsmount nfs_do_clone_mount(struct nfs_server server,
	const char *devname,
	struct nfs_clone_mount *mountdata)
	{
	#ifdef CONFIG_NFS_V4
	struct vfsmount *mnt = ERR_PTR(-EINVAL);
	switch (server->nfs_client->rpc_ops->version) {
	case 2:
	case 3:
	mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
	break;
	case 4:
	mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
	}
	return mnt;
	#else
	return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
	#endif
	}

	/**
	* nfs_do_submount - set up mountpoint when crossing a filesystem boundary
	* @dentry - parent directory
	* @fh - filehandle for new root dentry
	* @fattr - attributes for new root inode
	* @authflavor - security flavor to use when performing the mount
	*
	*/
	static struct vfsmount nfs_do_submount(struct dentry dentry,
	struct nfs_fh *fh,
	struct nfs_fattr *fattr,
	rpc_authflavor_t authflavor)
	{
	struct nfs_clone_mount mountdata = {
	.sb = dentry->d_sb,
	.dentry = dentry,
	.fh = fh,
	.fattr = fattr,
	.authflavor = authflavor,
	};
	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
	char page = (char ) __get_free_page(GFP_USER);
	char *devname;

	dprintk("--> nfs_do_submount()\n");

	dprintk("%s: submounting on %s/%s\n", __func__,
	dentry->d_parent->d_name.name,
	dentry->d_name.name);
	if (page == NULL)
	goto out;
	devname = nfs_devname(dentry, page, PAGE_SIZE);
	mnt = (struct vfsmount *)devname;
	if (IS_ERR(devname))
	goto free_page;
	mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
	free_page:
	free_page((unsigned long)page);
	out:
	dprintk("%s: done\n", __func__);

	dprintk("<-- nfs_do_submount() = %p\n", mnt);
	return mnt;
	}