fs/nfs/nfs4namespace.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * linux/fs/nfs/nfs4namespace.c
  *
  * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
  * - Modified by David Howells <dhowells@redhat.com>
  *
  * NFSv4 namespace
  */

 #include <linux/dcache.h>
 #include <linux/mount.h>
 #include <linux/namei.h>
 #include <linux/nfs_fs.h>
 #include <linux/nfs_mount.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/addr.h>
 #include <linux/vfs.h>
 #include <linux/inet.h>
 #include "internal.h"
 #include "nfs4_fs.h"
 #include "dns_resolve.h"

 #define NFSDBG_FACILITY		NFSDBG_VFS

 /*
  * Convert the NFSv4 pathname components into a standard posix path.
  *
  * Note that the resulting string will be placed at the end of the buffer
  */
 static inline char *nfs4_pathname_string(const struct nfs4_pathname *pathname,
 					 char *buffer, ssize_t buflen)
 {
 	char *end = buffer + buflen;
 	int n;

 	*--end = '\0';
 	buflen--;

 	n = pathname->ncomponents;
 	while (--n >= 0) {
 		const struct nfs4_string *component = &pathname->components[n];
 		buflen -= component->len + 1;
 		if (buflen < 0)
 			goto Elong;
 		end -= component->len;
 		memcpy(end, component->data, component->len);
 		*--end = '/';
 	}
 	return end;
 Elong:
 	return ERR_PTR(-ENAMETOOLONG);
 }

 /*
  * return the path component of "<server>:<path>"
  *  nfspath - the "<server>:<path>" string
  *  end - one past the last char that could contain "<server>:"
  * returns NULL on failure
  */
 static char *nfs_path_component(const char *nfspath, const char *end)
 {
 	char *p;

 	if (*nfspath == '[') {
 		/* parse [] escaped IPv6 addrs */
 		p = strchr(nfspath, ']');
 		if (p != NULL && ++p < end && *p == ':')
 			return p + 1;
 	} else {
 		/* otherwise split on first colon */
 		p = strchr(nfspath, ':');
 		if (p != NULL && p < end)
 			return p + 1;
 	}
 	return NULL;
 }

 /*
  * Determine the mount path as a string
  */
 static char *nfs4_path(struct dentry *dentry, char *buffer, ssize_t buflen)
 {
 	char *limit;
 	char *path = nfs_path(&limit, dentry, buffer, buflen,
 			      NFS_PATH_CANONICAL);
 	if (!IS_ERR(path)) {
 		char *path_component = nfs_path_component(path, limit);
 		if (path_component)
 			return path_component;
 	}
 	return path;
 }

 /*
  * Check that fs_locations::fs_root [RFC3530 6.3] is a prefix for what we
  * believe to be the server path to this dentry
  */
 static int nfs4_validate_fspath(struct dentry *dentry,
 				const struct nfs4_fs_locations *locations,
 				char *page, char *page2)
 {
 	const char *path, *fs_path;

 	path = nfs4_path(dentry, page, PAGE_SIZE);
 	if (IS_ERR(path))
 		return PTR_ERR(path);

 	fs_path = nfs4_pathname_string(&locations->fs_path, page2, PAGE_SIZE);
 	if (IS_ERR(fs_path))
 		return PTR_ERR(fs_path);

 	if (strncmp(path, fs_path, strlen(fs_path)) != 0) {
 		dprintk("%s: path %s does not begin with fsroot %s\n",
 			__func__, path, fs_path);
 		return -ENOENT;
 	}

 	return 0;
 }

 size_t nfs_parse_server_name(char *string, size_t len, struct sockaddr *sa,
 			     size_t salen, struct net *net)
 {
 	ssize_t ret;

 	ret = rpc_pton(net, string, len, sa, salen);
 	if (ret == 0) {
 		ret = nfs_dns_resolve_name(net, string, len, sa, salen);
 		if (ret < 0)
 			ret = 0;
 	}
 	return ret;
 }

 /**
  * nfs_find_best_sec - Find a security mechanism supported locally
  * @server: NFS server struct
  * @flavors: List of security tuples returned by SECINFO procedure
  *
  * Return an rpc client that uses the first security mechanism in
  * "flavors" that is locally supported.  The "flavors" array
  * is searched in the order returned from the server, per RFC 3530
  * recommendation and each flavor is checked for membership in the
  * sec= mount option list if it exists.
  *
  * Return -EPERM if no matching flavor is found in the array.
  *
  * Please call rpc_shutdown_client() when you are done with this rpc client.
  *
  */
 static struct rpc_clnt *nfs_find_best_sec(struct rpc_clnt *clnt,
 					  struct nfs_server *server,
 					  struct nfs4_secinfo_flavors *flavors)
 {
 	rpc_authflavor_t pflavor;
 	struct nfs4_secinfo4 *secinfo;
 	unsigned int i;

 	for (i = 0; i < flavors->num_flavors; i++) {
 		secinfo = &flavors->flavors[i];

 		switch (secinfo->flavor) {
 		case RPC_AUTH_NULL:
 		case RPC_AUTH_UNIX:
 		case RPC_AUTH_GSS:
 			pflavor = rpcauth_get_pseudoflavor(secinfo->flavor,
 							&secinfo->flavor_info);
 			/* does the pseudoflavor match a sec= mount opt? */
 			if (pflavor != RPC_AUTH_MAXFLAVOR &&
 			    nfs_auth_info_match(&server->auth_info, pflavor)) {
 				struct rpc_clnt *new;
 				struct rpc_cred *cred;

 				/* Cloning creates an rpc_auth for the flavor */
 				new = rpc_clone_client_set_auth(clnt, pflavor);
 				if (IS_ERR(new))
 					continue;
 				/**
 				* Check that the user actually can use the
 				* flavor. This is mostly for RPC_AUTH_GSS
 				* where cr_init obtains a gss context
 				*/
 				cred = rpcauth_lookupcred(new->cl_auth, 0);
 				if (IS_ERR(cred)) {
 					rpc_shutdown_client(new);
 					continue;
 				}
 				put_rpccred(cred);
 				return new;
 			}
 		}
 	}
 	return ERR_PTR(-EPERM);
 }

 /**
  * nfs4_negotiate_security - in response to an NFS4ERR_WRONGSEC on lookup,
  * return an rpc_clnt that uses the best available security flavor with
  * respect to the secinfo flavor list and the sec= mount options.
  *
  * @clnt: RPC client to clone
  * @inode: directory inode
  * @name: lookup name
  *
  * Please call rpc_shutdown_client() when you are done with this rpc client.
  */
 struct rpc_clnt *
 nfs4_negotiate_security(struct rpc_clnt *clnt, struct inode *inode,
 					const struct qstr *name)
 {
 	struct page *page;
 	struct nfs4_secinfo_flavors *flavors;
 	struct rpc_clnt *new;
 	int err;

 	page = alloc_page(GFP_KERNEL);
 	if (!page)
 		return ERR_PTR(-ENOMEM);

 	flavors = page_address(page);

 	err = nfs4_proc_secinfo(inode, name, flavors);
 	if (err < 0) {
 		new = ERR_PTR(err);
 		goto out;
 	}

 	new = nfs_find_best_sec(clnt, NFS_SERVER(inode), flavors);

 out:
 	put_page(page);
 	return new;
 }

 static struct vfsmount *try_location(struct nfs_clone_mount *mountdata,
 				     char *page, char *page2,
 				     const struct nfs4_fs_location *location)
 {
 	const size_t addr_bufsize = sizeof(struct sockaddr_storage);
 	struct net *net = rpc_net_ns(NFS_SB(mountdata->sb)->client);
 	struct vfsmount *mnt = ERR_PTR(-ENOENT);
 	char *mnt_path;
 	unsigned int maxbuflen;
 	unsigned int s;

 	mnt_path = nfs4_pathname_string(&location->rootpath, page2, PAGE_SIZE);
 	if (IS_ERR(mnt_path))
 		return ERR_CAST(mnt_path);
 	mountdata->mnt_path = mnt_path;
 	maxbuflen = mnt_path - 1 - page2;

 	mountdata->addr = kmalloc(addr_bufsize, GFP_KERNEL);
 	if (mountdata->addr == NULL)
 		return ERR_PTR(-ENOMEM);

 	for (s = 0; s < location->nservers; s++) {
 		const struct nfs4_string *buf = &location->servers[s];

 		if (buf->len <= 0 || buf->len >= maxbuflen)
 			continue;

 		if (memchr(buf->data, IPV6_SCOPE_DELIMITER, buf->len))
 			continue;

 		mountdata->addrlen = nfs_parse_server_name(buf->data, buf->len,
 				mountdata->addr, addr_bufsize, net);
 		if (mountdata->addrlen == 0)
 			continue;

 		memcpy(page2, buf->data, buf->len);
 		page2[buf->len] = '\0';
 		mountdata->hostname = page2;

 		snprintf(page, PAGE_SIZE, "%s:%s",
 				mountdata->hostname,
 				mountdata->mnt_path);

 		mnt = vfs_submount(mountdata->dentry, &nfs4_referral_fs_type, page, mountdata);
 		if (!IS_ERR(mnt))
 			break;
 	}
 	kfree(mountdata->addr);
 	return mnt;
 }

 /**
  * nfs_follow_referral - set up mountpoint when hitting a referral on moved error
  * @dentry - parent directory
  * @locations - array of NFSv4 server location information
  *
  */
 static struct vfsmount *nfs_follow_referral(struct dentry *dentry,
 					    const struct nfs4_fs_locations *locations)
 {
 	struct vfsmount *mnt = ERR_PTR(-ENOENT);
 	struct nfs_clone_mount mountdata = {
 		.sb = dentry->d_sb,
 		.dentry = dentry,
 		.authflavor = NFS_SB(dentry->d_sb)->client->cl_auth->au_flavor,
 	};
 	char *page = NULL, *page2 = NULL;
 	int loc, error;

 	if (locations == NULL || locations->nlocations <= 0)
 		goto out;

 	dprintk("%s: referral at %pd2\n", __func__, dentry);

 	page = (char *) __get_free_page(GFP_USER);
 	if (!page)
 		goto out;

 	page2 = (char *) __get_free_page(GFP_USER);
 	if (!page2)
 		goto out;

 	/* Ensure fs path is a prefix of current dentry path */
 	error = nfs4_validate_fspath(dentry, locations, page, page2);
 	if (error < 0) {
 		mnt = ERR_PTR(error);
 		goto out;
 	}

 	for (loc = 0; loc < locations->nlocations; loc++) {
 		const struct nfs4_fs_location *location = &locations->locations[loc];

 		if (location == NULL || location->nservers <= 0 ||
 		    location->rootpath.ncomponents == 0)
 			continue;

 		mnt = try_location(&mountdata, page, page2, location);
 		if (!IS_ERR(mnt))
 			break;
 	}

 out:
 	free_page((unsigned long) page);
 	free_page((unsigned long) page2);
 	return mnt;
 }

 /*
  * nfs_do_refmount - handle crossing a referral on server
  * @dentry - dentry of referral
  *
  */
 static struct vfsmount *nfs_do_refmount(struct rpc_clnt *client, struct dentry *dentry)
 {
 	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 	struct dentry *parent;
 	struct nfs4_fs_locations *fs_locations = NULL;
 	struct page *page;
 	int err;

 	/* BUG_ON(IS_ROOT(dentry)); */
 	page = alloc_page(GFP_KERNEL);
 	if (page == NULL)
 		return mnt;

 	fs_locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
 	if (fs_locations == NULL)
 		goto out_free;

 	/* Get locations */
 	mnt = ERR_PTR(-ENOENT);

 	parent = dget_parent(dentry);
 	dprintk("%s: getting locations for %pd2\n",
 		__func__, dentry);

 	err = nfs4_proc_fs_locations(client, d_inode(parent), &dentry->d_name, fs_locations, page);
 	dput(parent);
 	if (err != 0 ||
 	    fs_locations->nlocations <= 0 ||
 	    fs_locations->fs_path.ncomponents <= 0)
 		goto out_free;

 	mnt = nfs_follow_referral(dentry, fs_locations);
 out_free:
 	__free_page(page);
 	kfree(fs_locations);
 	return mnt;
 }

 struct vfsmount *nfs4_submount(struct nfs_server *server, struct dentry *dentry,
 			       struct nfs_fh *fh, struct nfs_fattr *fattr)
 {
 	rpc_authflavor_t flavor = server->client->cl_auth->au_flavor;
 	struct dentry *parent = dget_parent(dentry);
 	struct inode *dir = d_inode(parent);
 	const struct qstr *name = &dentry->d_name;
 	struct rpc_clnt *client;
 	struct vfsmount *mnt;

 	/* Look it up again to get its attributes and sec flavor */
 	client = nfs4_proc_lookup_mountpoint(dir, name, fh, fattr);
 	dput(parent);
 	if (IS_ERR(client))
 		return ERR_CAST(client);

 	if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 		mnt = nfs_do_refmount(client, dentry);
 		goto out;
 	}

 	if (client->cl_auth->au_flavor != flavor)
 		flavor = client->cl_auth->au_flavor;
 	mnt = nfs_do_submount(dentry, fh, fattr, flavor);
 out:
 	rpc_shutdown_client(client);
 	return mnt;
 }

 /*
  * Try one location from the fs_locations array.
  *
  * Returns zero on success, or a negative errno value.
  */
 static int nfs4_try_replacing_one_location(struct nfs_server *server,
 		char *page, char *page2,
 		const struct nfs4_fs_location *location)
 {
 	const size_t addr_bufsize = sizeof(struct sockaddr_storage);
 	struct net *net = rpc_net_ns(server->client);
 	struct sockaddr *sap;
 	unsigned int s;
 	size_t salen;
 	int error;

 	sap = kmalloc(addr_bufsize, GFP_KERNEL);
 	if (sap == NULL)
 		return -ENOMEM;

 	error = -ENOENT;
 	for (s = 0; s < location->nservers; s++) {
 		const struct nfs4_string *buf = &location->servers[s];
 		char *hostname;

 		if (buf->len <= 0 || buf->len > PAGE_SIZE)
 			continue;

 		if (memchr(buf->data, IPV6_SCOPE_DELIMITER, buf->len) != NULL)
 			continue;

 		salen = nfs_parse_server_name(buf->data, buf->len,
 						sap, addr_bufsize, net);
 		if (salen == 0)
 			continue;
 		rpc_set_port(sap, NFS_PORT);

 		error = -ENOMEM;
 		hostname = kstrndup(buf->data, buf->len, GFP_KERNEL);
 		if (hostname == NULL)
 			break;

 		error = nfs4_update_server(server, hostname, sap, salen, net);
 		kfree(hostname);
 		if (error == 0)
 			break;
 	}

 	kfree(sap);
 	return error;
 }

 /**
  * nfs4_replace_transport - set up transport to destination server
  *
  * @server: export being migrated
  * @locations: fs_locations array
  *
  * Returns zero on success, or a negative errno value.
  *
  * The client tries all the entries in the "locations" array, in the
  * order returned by the server, until one works or the end of the
  * array is reached.
  */
 int nfs4_replace_transport(struct nfs_server *server,
 			   const struct nfs4_fs_locations *locations)
 {
 	char *page = NULL, *page2 = NULL;
 	int loc, error;

 	error = -ENOENT;
 	if (locations == NULL || locations->nlocations <= 0)
 		goto out;

 	error = -ENOMEM;
 	page = (char *) __get_free_page(GFP_USER);
 	if (!page)
 		goto out;
 	page2 = (char *) __get_free_page(GFP_USER);
 	if (!page2)
 		goto out;

 	for (loc = 0; loc < locations->nlocations; loc++) {
 		const struct nfs4_fs_location *location =
 						&locations->locations[loc];

 		if (location == NULL || location->nservers <= 0 ||
 		    location->rootpath.ncomponents == 0)
 			continue;

 		error = nfs4_try_replacing_one_location(server, page,
 							page2, location);
 		if (error == 0)
 			break;
 	}

 out:
 	free_page((unsigned long)page);
 	free_page((unsigned long)page2);
 	return error;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/fs/nfs/nfs4namespace.c
	*
	* Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
	* - Modified by David Howells <dhowells@redhat.com>
	*
	* NFSv4 namespace
	*/

	#include <linux/dcache.h>
	#include <linux/mount.h>
	#include <linux/namei.h>
	#include <linux/nfs_fs.h>
	#include <linux/nfs_mount.h>
	#include <linux/slab.h>
	#include <linux/string.h>
	#include <linux/sunrpc/clnt.h>
	#include <linux/sunrpc/addr.h>
	#include <linux/vfs.h>
	#include <linux/inet.h>
	#include "internal.h"
	#include "nfs4_fs.h"
	#include "dns_resolve.h"

	#define NFSDBG_FACILITY NFSDBG_VFS

	/*
	* Convert the NFSv4 pathname components into a standard posix path.
	*
	* Note that the resulting string will be placed at the end of the buffer
	*/
	static inline char nfs4_pathname_string(const struct nfs4_pathname pathname,
	char *buffer, ssize_t buflen)
	{
	char *end = buffer + buflen;
	int n;

	*--end = '\0';
	buflen--;

	n = pathname->ncomponents;
	while (--n >= 0) {
	const struct nfs4_string *component = &pathname->components[n];
	buflen -= component->len + 1;
	if (buflen < 0)
	goto Elong;
	end -= component->len;
	memcpy(end, component->data, component->len);
	*--end = '/';
	}
	return end;
	Elong:
	return ERR_PTR(-ENAMETOOLONG);
	}

	/*
	* return the path component of "<server>:<path>"
	* nfspath - the "<server>:<path>" string
	* end - one past the last char that could contain "<server>:"
	* returns NULL on failure
	*/
	static char nfs_path_component(const char nfspath, const char *end)
	{
	char *p;

	if (*nfspath == '[') {
	/* parse [] escaped IPv6 addrs */
	p = strchr(nfspath, ']');
	if (p != NULL && ++p < end && *p == ':')
	return p + 1;
	} else {
	/* otherwise split on first colon */
	p = strchr(nfspath, ':');
	if (p != NULL && p < end)
	return p + 1;
	}
	return NULL;
	}

	/*
	* Determine the mount path as a string
	*/
	static char nfs4_path(struct dentry dentry, char *buffer, ssize_t buflen)
	{
	char *limit;
	char *path = nfs_path(&limit, dentry, buffer, buflen,
	NFS_PATH_CANONICAL);
	if (!IS_ERR(path)) {
	char *path_component = nfs_path_component(path, limit);
	if (path_component)
	return path_component;
	}
	return path;
	}

	/*
	* Check that fs_locations::fs_root [RFC3530 6.3] is a prefix for what we
	* believe to be the server path to this dentry
	*/
	static int nfs4_validate_fspath(struct dentry *dentry,
	const struct nfs4_fs_locations *locations,
	char page, char page2)
	{
	const char path, fs_path;

	path = nfs4_path(dentry, page, PAGE_SIZE);
	if (IS_ERR(path))
	return PTR_ERR(path);

	fs_path = nfs4_pathname_string(&locations->fs_path, page2, PAGE_SIZE);
	if (IS_ERR(fs_path))
	return PTR_ERR(fs_path);

	if (strncmp(path, fs_path, strlen(fs_path)) != 0) {
	dprintk("%s: path %s does not begin with fsroot %s\n",
	__func__, path, fs_path);
	return -ENOENT;
	}

	return 0;
	}

	size_t nfs_parse_server_name(char string, size_t len, struct sockaddr sa,
	size_t salen, struct net *net)
	{
	ssize_t ret;

	ret = rpc_pton(net, string, len, sa, salen);
	if (ret == 0) {
	ret = nfs_dns_resolve_name(net, string, len, sa, salen);
	if (ret < 0)
	ret = 0;
	}
	return ret;
	}

	/**
	* nfs_find_best_sec - Find a security mechanism supported locally
	* @server: NFS server struct
	* @flavors: List of security tuples returned by SECINFO procedure
	*
	* Return an rpc client that uses the first security mechanism in
	* "flavors" that is locally supported. The "flavors" array
	* is searched in the order returned from the server, per RFC 3530
	* recommendation and each flavor is checked for membership in the
	* sec= mount option list if it exists.
	*
	* Return -EPERM if no matching flavor is found in the array.
	*
	* Please call rpc_shutdown_client() when you are done with this rpc client.
	*
	*/
	static struct rpc_clnt nfs_find_best_sec(struct rpc_clnt clnt,
	struct nfs_server *server,
	struct nfs4_secinfo_flavors *flavors)
	{
	rpc_authflavor_t pflavor;
	struct nfs4_secinfo4 *secinfo;
	unsigned int i;

	for (i = 0; i < flavors->num_flavors; i++) {
	secinfo = &flavors->flavors[i];

	switch (secinfo->flavor) {
	case RPC_AUTH_NULL:
	case RPC_AUTH_UNIX:
	case RPC_AUTH_GSS:
	pflavor = rpcauth_get_pseudoflavor(secinfo->flavor,
	&secinfo->flavor_info);
	/* does the pseudoflavor match a sec= mount opt? */
	if (pflavor != RPC_AUTH_MAXFLAVOR &&
	nfs_auth_info_match(&server->auth_info, pflavor)) {
	struct rpc_clnt *new;
	struct rpc_cred *cred;

	/* Cloning creates an rpc_auth for the flavor */
	new = rpc_clone_client_set_auth(clnt, pflavor);
	if (IS_ERR(new))
	continue;
	/**
	* Check that the user actually can use the
	* flavor. This is mostly for RPC_AUTH_GSS
	* where cr_init obtains a gss context
	*/
	cred = rpcauth_lookupcred(new->cl_auth, 0);
	if (IS_ERR(cred)) {
	rpc_shutdown_client(new);
	continue;
	}
	put_rpccred(cred);
	return new;
	}
	}
	}
	return ERR_PTR(-EPERM);
	}

	/**
	* nfs4_negotiate_security - in response to an NFS4ERR_WRONGSEC on lookup,
	* return an rpc_clnt that uses the best available security flavor with
	* respect to the secinfo flavor list and the sec= mount options.
	*
	* @clnt: RPC client to clone
	* @inode: directory inode
	* @name: lookup name
	*
	* Please call rpc_shutdown_client() when you are done with this rpc client.
	*/
	struct rpc_clnt *
	nfs4_negotiate_security(struct rpc_clnt clnt, struct inode inode,
	const struct qstr *name)
	{
	struct page *page;
	struct nfs4_secinfo_flavors *flavors;
	struct rpc_clnt *new;
	int err;

	page = alloc_page(GFP_KERNEL);
	if (!page)
	return ERR_PTR(-ENOMEM);

	flavors = page_address(page);

	err = nfs4_proc_secinfo(inode, name, flavors);
	if (err < 0) {
	new = ERR_PTR(err);
	goto out;
	}

	new = nfs_find_best_sec(clnt, NFS_SERVER(inode), flavors);

	out:
	put_page(page);
	return new;
	}

	static struct vfsmount try_location(struct nfs_clone_mount mountdata,
	char page, char page2,
	const struct nfs4_fs_location *location)
	{
	const size_t addr_bufsize = sizeof(struct sockaddr_storage);
	struct net *net = rpc_net_ns(NFS_SB(mountdata->sb)->client);
	struct vfsmount *mnt = ERR_PTR(-ENOENT);
	char *mnt_path;
	unsigned int maxbuflen;
	unsigned int s;

	mnt_path = nfs4_pathname_string(&location->rootpath, page2, PAGE_SIZE);
	if (IS_ERR(mnt_path))
	return ERR_CAST(mnt_path);
	mountdata->mnt_path = mnt_path;
	maxbuflen = mnt_path - 1 - page2;

	mountdata->addr = kmalloc(addr_bufsize, GFP_KERNEL);
	if (mountdata->addr == NULL)
	return ERR_PTR(-ENOMEM);

	for (s = 0; s < location->nservers; s++) {
	const struct nfs4_string *buf = &location->servers[s];

	if (buf->len <= 0 \|\| buf->len >= maxbuflen)
	continue;

	if (memchr(buf->data, IPV6_SCOPE_DELIMITER, buf->len))
	continue;

	mountdata->addrlen = nfs_parse_server_name(buf->data, buf->len,
	mountdata->addr, addr_bufsize, net);
	if (mountdata->addrlen == 0)
	continue;

	memcpy(page2, buf->data, buf->len);
	page2[buf->len] = '\0';
	mountdata->hostname = page2;

	snprintf(page, PAGE_SIZE, "%s:%s",
	mountdata->hostname,
	mountdata->mnt_path);

	mnt = vfs_submount(mountdata->dentry, &nfs4_referral_fs_type, page, mountdata);
	if (!IS_ERR(mnt))
	break;
	}
	kfree(mountdata->addr);
	return mnt;
	}

	/**
	* nfs_follow_referral - set up mountpoint when hitting a referral on moved error
	* @dentry - parent directory
	* @locations - array of NFSv4 server location information
	*
	*/
	static struct vfsmount nfs_follow_referral(struct dentry dentry,
	const struct nfs4_fs_locations *locations)
	{
	struct vfsmount *mnt = ERR_PTR(-ENOENT);
	struct nfs_clone_mount mountdata = {
	.sb = dentry->d_sb,
	.dentry = dentry,
	.authflavor = NFS_SB(dentry->d_sb)->client->cl_auth->au_flavor,
	};
	char page = NULL, page2 = NULL;
	int loc, error;

	if (locations == NULL \|\| locations->nlocations <= 0)
	goto out;

	dprintk("%s: referral at %pd2\n", __func__, dentry);

	page = (char *) __get_free_page(GFP_USER);
	if (!page)
	goto out;

	page2 = (char *) __get_free_page(GFP_USER);
	if (!page2)
	goto out;

	/* Ensure fs path is a prefix of current dentry path */
	error = nfs4_validate_fspath(dentry, locations, page, page2);
	if (error < 0) {
	mnt = ERR_PTR(error);
	goto out;
	}

	for (loc = 0; loc < locations->nlocations; loc++) {
	const struct nfs4_fs_location *location = &locations->locations[loc];

	if (location == NULL \|\| location->nservers <= 0 \|\|
	location->rootpath.ncomponents == 0)
	continue;

	mnt = try_location(&mountdata, page, page2, location);
	if (!IS_ERR(mnt))
	break;
	}

	out:
	free_page((unsigned long) page);
	free_page((unsigned long) page2);
	return mnt;
	}

	/*
	* nfs_do_refmount - handle crossing a referral on server
	* @dentry - dentry of referral
	*
	*/
	static struct vfsmount nfs_do_refmount(struct rpc_clnt client, struct dentry *dentry)
	{
	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
	struct dentry *parent;
	struct nfs4_fs_locations *fs_locations = NULL;
	struct page *page;
	int err;

	/* BUG_ON(IS_ROOT(dentry)); */
	page = alloc_page(GFP_KERNEL);
	if (page == NULL)
	return mnt;

	fs_locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
	if (fs_locations == NULL)
	goto out_free;

	/* Get locations */
	mnt = ERR_PTR(-ENOENT);

	parent = dget_parent(dentry);
	dprintk("%s: getting locations for %pd2\n",
	__func__, dentry);

	err = nfs4_proc_fs_locations(client, d_inode(parent), &dentry->d_name, fs_locations, page);
	dput(parent);
	if (err != 0 \|\|
	fs_locations->nlocations <= 0 \|\|
	fs_locations->fs_path.ncomponents <= 0)
	goto out_free;

	mnt = nfs_follow_referral(dentry, fs_locations);
	out_free:
	__free_page(page);
	kfree(fs_locations);
	return mnt;
	}

	struct vfsmount nfs4_submount(struct nfs_server server, struct dentry *dentry,
	struct nfs_fh fh, struct nfs_fattr fattr)
	{
	rpc_authflavor_t flavor = server->client->cl_auth->au_flavor;
	struct dentry *parent = dget_parent(dentry);
	struct inode *dir = d_inode(parent);
	const struct qstr *name = &dentry->d_name;
	struct rpc_clnt *client;
	struct vfsmount *mnt;

	/* Look it up again to get its attributes and sec flavor */
	client = nfs4_proc_lookup_mountpoint(dir, name, fh, fattr);
	dput(parent);
	if (IS_ERR(client))
	return ERR_CAST(client);

	if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
	mnt = nfs_do_refmount(client, dentry);
	goto out;
	}

	if (client->cl_auth->au_flavor != flavor)
	flavor = client->cl_auth->au_flavor;
	mnt = nfs_do_submount(dentry, fh, fattr, flavor);
	out:
	rpc_shutdown_client(client);
	return mnt;
	}

	/*
	* Try one location from the fs_locations array.
	*
	* Returns zero on success, or a negative errno value.
	*/
	static int nfs4_try_replacing_one_location(struct nfs_server *server,
	char page, char page2,
	const struct nfs4_fs_location *location)
	{
	const size_t addr_bufsize = sizeof(struct sockaddr_storage);
	struct net *net = rpc_net_ns(server->client);
	struct sockaddr *sap;
	unsigned int s;
	size_t salen;
	int error;

	sap = kmalloc(addr_bufsize, GFP_KERNEL);
	if (sap == NULL)
	return -ENOMEM;

	error = -ENOENT;
	for (s = 0; s < location->nservers; s++) {
	const struct nfs4_string *buf = &location->servers[s];
	char *hostname;

	if (buf->len <= 0 \|\| buf->len > PAGE_SIZE)
	continue;

	if (memchr(buf->data, IPV6_SCOPE_DELIMITER, buf->len) != NULL)
	continue;

	salen = nfs_parse_server_name(buf->data, buf->len,
	sap, addr_bufsize, net);
	if (salen == 0)
	continue;
	rpc_set_port(sap, NFS_PORT);

	error = -ENOMEM;
	hostname = kstrndup(buf->data, buf->len, GFP_KERNEL);
	if (hostname == NULL)
	break;

	error = nfs4_update_server(server, hostname, sap, salen, net);
	kfree(hostname);
	if (error == 0)
	break;
	}

	kfree(sap);
	return error;
	}

	/**
	* nfs4_replace_transport - set up transport to destination server
	*
	* @server: export being migrated
	* @locations: fs_locations array
	*
	* Returns zero on success, or a negative errno value.
	*
	* The client tries all the entries in the "locations" array, in the
	* order returned by the server, until one works or the end of the
	* array is reached.
	*/
	int nfs4_replace_transport(struct nfs_server *server,
	const struct nfs4_fs_locations *locations)
	{
	char page = NULL, page2 = NULL;
	int loc, error;

	error = -ENOENT;
	if (locations == NULL \|\| locations->nlocations <= 0)
	goto out;

	error = -ENOMEM;
	page = (char *) __get_free_page(GFP_USER);
	if (!page)
	goto out;
	page2 = (char *) __get_free_page(GFP_USER);
	if (!page2)
	goto out;

	for (loc = 0; loc < locations->nlocations; loc++) {
	const struct nfs4_fs_location *location =
	&locations->locations[loc];

	if (location == NULL \|\| location->nservers <= 0 \|\|
	location->rootpath.ncomponents == 0)
	continue;

	error = nfs4_try_replacing_one_location(server, page,
	page2, location);
	if (error == 0)
	break;
	}

	out:
	free_page((unsigned long)page);
	free_page((unsigned long)page2);
	return error;
	}