NFS: Add fs_context support.

Add filesystem context support to NFS, parsing the options in advance and
attaching the information to struct nfs_fs_context.  The highlights are:

 (*) Merge nfs_mount_info and nfs_clone_mount into nfs_fs_context.  This
     structure represents NFS's superblock config.

 (*) Make use of the VFS's parsing support to split comma-separated lists

 (*) Pin the NFS protocol module in the nfs_fs_context.

 (*) Attach supplementary error information to fs_context.  This has the
     downside that these strings must be static and can't be formatted.

 (*) Remove the auxiliary file_system_type structs since the information
     necessary can be conveyed in the nfs_fs_context struct instead.

 (*) Root mounts are made by duplicating the config for the requested mount
     so as to have the same parameters.  Submounts pick up their parameters
     from the parent superblock.

[AV -- retrans is u32, not string]
[SM -- Renamed cfg to ctx in a few functions in an earlier patch]
[SM -- Moved fs_context mount option parsing to an earlier patch]
[SM -- Moved fs_context error logging to a later patch]
[SM -- Fixed printks in nfs4_try_get_tree() and nfs4_get_referral_tree()]
[SM -- Added is_remount_fc() helper]
[SM -- Deferred some refactoring to a later patch]
[SM -- Fixed referral mounts, which were broken in the original patch]
[SM -- Fixed leak of nfs_fattr when fs_context is freed]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/internal.h

@@ -4,7 +4,7 @@
  */
 
 #include "nfs4_fs.h"
-#include <linux/mount.h>
+#include <linux/fs_context.h>
 #include <linux/security.h>
 #include <linux/crc32.h>
 #include <linux/sunrpc/addr.h>
@@ -16,6 +16,7 @@
 extern const struct export_operations nfs_export_ops;
 
 struct nfs_string;
+struct nfs_pageio_descriptor;
 
 static inline void nfs_attr_check_mountpoint(struct super_block *parent, struct nfs_fattr *fattr)
 {
@@ -34,12 +35,13 @@ static inline int nfs_attr_use_mounted_on_fileid(struct nfs_fattr *fattr)
 
 struct nfs_clone_mount {
 	const struct super_block *sb;
-	const struct dentry *dentry;
+	struct dentry *dentry;
 	char *hostname;
 	char *mnt_path;
 	struct sockaddr *addr;
 	size_t addrlen;
 	rpc_authflavor_t authflavor;
+	struct nfs_fattr *fattr;
 };
 
 /*
@@ -78,10 +80,23 @@ struct nfs_client_initdata {
 	const struct cred *cred;
 };
 
+struct nfs_mount_info {
+	unsigned int inherited_bsize;
+	struct nfs_fs_context *ctx;
+	struct nfs_clone_mount *cloned;
+	struct nfs_server *server;
+	struct nfs_fh *mntfh;
+	struct nfs_subversion *nfs_mod;
+};
+
 /*
  * In-kernel mount arguments
  */
 struct nfs_fs_context {
+	bool			internal;
+	bool			skip_reconfig_option_check;
+	bool			need_mount;
+	bool			sloppy;
 	unsigned int		flags;		/* NFS{,4}_MOUNT_* flags */
 	unsigned int		rsize, wsize;
 	unsigned int		timeo, retrans;
@@ -98,8 +113,6 @@ struct nfs_fs_context {
 	char			*fscache_uniq;
 	unsigned short		protofamily;
 	unsigned short		mountfamily;
-	bool			need_mount;
-	bool			sloppy;
 
 	struct {
 		union {
@@ -124,14 +137,23 @@ struct nfs_fs_context {
 		int			port;
 		unsigned short		protocol;
 		unsigned short		nconnect;
+		unsigned short		export_path_len;
 	} nfs_server;
 
 	void			*lsm_opts;
 	struct net		*net;
 
 	char			buf[32];	/* Parse buffer */
+
+	struct nfs_mount_info	mount_info;
+	struct nfs_clone_mount	clone_data;
 };
 
+static inline struct nfs_fs_context *nfs_fc2context(const struct fs_context *fc)
+{
+	return fc->fs_private;
+}
+
 /* mount_clnt.c */
 struct nfs_mount_request {
 	struct sockaddr		*sap;
@@ -147,15 +169,6 @@ struct nfs_mount_request {
 	struct net		*net;
 };
 
-struct nfs_mount_info {
-	unsigned int inherited_bsize;
-	struct nfs_fs_context *ctx;
-	struct nfs_clone_mount *cloned;
-	struct nfs_server *server;
-	struct nfs_fh *mntfh;
-	struct nfs_subversion *nfs_mod;
-};
-
 extern int nfs_mount(struct nfs_mount_request *info);
 extern void nfs_umount(const struct nfs_mount_request *info);
 
@@ -235,22 +248,8 @@ static inline void nfs_fs_proc_exit(void)
 extern const struct svc_version nfs4_callback_version1;
 extern const struct svc_version nfs4_callback_version4;
 
-struct nfs_pageio_descriptor;
-
-/* mount.c */
-#define NFS_TEXT_DATA		1
-
-extern struct nfs_fs_context *nfs_alloc_parsed_mount_data(void);
-extern void nfs_free_parsed_mount_data(struct nfs_fs_context *ctx);
-extern int nfs_parse_mount_options(char *raw, struct nfs_fs_context *ctx);
-extern int nfs_validate_mount_data(struct file_system_type *fs_type,
-				   void *options,
-				   struct nfs_fs_context *ctx,
-				   struct nfs_fh *mntfh,
-				   const char *dev_name);
-extern int nfs_validate_text_mount_data(void *options,
-					struct nfs_fs_context *ctx,
-					const char *dev_name);
+/* fs_context.c */
+extern struct file_system_type nfs_fs_type;
 
 /* pagelist.c */
 extern int __init nfs_init_nfspagecache(void);
@@ -411,14 +410,9 @@ extern int nfs_wait_atomic_killable(atomic_t *p, unsigned int mode);
 
 /* super.c */
 extern const struct super_operations nfs_sops;
-extern struct file_system_type nfs_fs_type;
-extern struct file_system_type nfs_prepared_fs_type;
-#if IS_ENABLED(CONFIG_NFS_V4)
-extern struct file_system_type nfs4_referral_fs_type;
-#endif
 bool nfs_auth_info_match(const struct nfs_auth_info *, rpc_authflavor_t);
-struct dentry *nfs_try_mount(int, const char *, struct nfs_mount_info *);
-struct dentry *nfs_fs_mount(struct file_system_type *, int, const char *, void *);
+int nfs_try_get_tree(struct fs_context *);
+int nfs_get_tree_common(struct fs_context *);
 void nfs_kill_super(struct super_block *);
 
 extern struct rpc_stat nfs_rpcstat;
@@ -446,10 +440,8 @@ static inline bool nfs_file_io_is_buffered(struct nfs_inode *nfsi)
 extern char *nfs_path(char **p, struct dentry *dentry,
 		      char *buffer, ssize_t buflen, unsigned flags);
 extern struct vfsmount *nfs_d_automount(struct path *path);
-struct vfsmount *nfs_submount(struct nfs_server *, struct dentry *,
-			      struct nfs_fh *, struct nfs_fattr *);
-struct vfsmount *nfs_do_submount(struct dentry *, struct nfs_fh *,
-				 struct nfs_fattr *, rpc_authflavor_t);
+int nfs_submount(struct fs_context *, struct nfs_server *);
+int nfs_do_submount(struct fs_context *);
 
 /* getroot.c */
 extern struct dentry *nfs_get_root(struct super_block *, struct nfs_fh *,
@@ -476,7 +468,7 @@ int  nfs_show_options(struct seq_file *, struct dentry *);
 int  nfs_show_devname(struct seq_file *, struct dentry *);
 int  nfs_show_path(struct seq_file *, struct dentry *);
 int  nfs_show_stats(struct seq_file *, struct dentry *);
-int nfs_remount(struct super_block *sb, int *flags, char *raw_data);
+int  nfs_reconfigure(struct fs_context *);
 
 /* write.c */
 extern void nfs_pageio_init_write(struct nfs_pageio_descriptor *pgio,

fs/nfs/namespace.c

@@ -140,34 +140,65 @@ EXPORT_SYMBOL_GPL(nfs_path);
  */
 struct vfsmount *nfs_d_automount(struct path *path)
 {
-	struct vfsmount *mnt;
+	struct nfs_fs_context *ctx;
+	struct fs_context *fc;
+	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 	struct nfs_server *server = NFS_SERVER(d_inode(path->dentry));
-	struct nfs_fh *fh = NULL;
-	struct nfs_fattr *fattr = NULL;
+	struct nfs_client *client = server->nfs_client;
+	int ret;
 
 	if (IS_ROOT(path->dentry))
 		return ERR_PTR(-ESTALE);
 
-	mnt = ERR_PTR(-ENOMEM);
-	fh = nfs_alloc_fhandle();
-	fattr = nfs_alloc_fattr();
-	if (fh == NULL || fattr == NULL)
-		goto out;
+	/* Open a new filesystem context, transferring parameters from the
+	 * parent superblock, including the network namespace.
+	 */
+	fc = fs_context_for_submount(&nfs_fs_type, path->dentry);
+	if (IS_ERR(fc))
+		return ERR_CAST(fc);
 
-	mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
+	ctx = nfs_fc2context(fc);
+	ctx->clone_data.dentry	= path->dentry;
+	ctx->clone_data.sb	= path->dentry->d_sb;
+	ctx->clone_data.fattr	= nfs_alloc_fattr();
+	if (!ctx->clone_data.fattr)
+		goto out_fc;
+
+	if (fc->net_ns != client->cl_net) {
+		put_net(fc->net_ns);
+		fc->net_ns = get_net(client->cl_net);
+	}
+
+	/* for submounts we want the same server; referrals will reassign */
+	memcpy(&ctx->nfs_server.address, &client->cl_addr, client->cl_addrlen);
+	ctx->nfs_server.addrlen	= client->cl_addrlen;
+	ctx->nfs_server.port	= server->port;
+
+	ctx->version		= client->rpc_ops->version;
+	ctx->minorversion	= client->cl_minorversion;
+	ctx->mount_info.nfs_mod	= client->cl_nfs_mod;
+	__module_get(ctx->mount_info.nfs_mod->owner);
+
+	ret = client->rpc_ops->submount(fc, server);
+	if (ret < 0) {
+		mnt = ERR_PTR(ret);
+		goto out_fc;
+	}
+
+	up_write(&fc->root->d_sb->s_umount);
+	mnt = vfs_create_mount(fc);
 	if (IS_ERR(mnt))
-		goto out;
+		goto out_fc;
 
 	if (nfs_mountpoint_expiry_timeout < 0)
-		goto out;
+		goto out_fc;
 
 	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_fc:
+	put_fs_context(fc);
 	return mnt;
 }
 
@@ -222,61 +253,62 @@ void nfs_release_automount_timer(void)
  * @authflavor: security flavor to use when performing the mount
  *
  */
-struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
-				 struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
+int nfs_do_submount(struct fs_context *fc)
 {
-	struct super_block *sb = dentry->d_sb;
-	struct nfs_clone_mount mountdata = {
-		.sb = sb,
-		.dentry = dentry,
-		.authflavor = authflavor,
-	};
-	struct nfs_mount_info mount_info = {
-		.inherited_bsize = sb->s_blocksize_bits,
-		.cloned = &mountdata,
-		.mntfh = fh,
-		.nfs_mod = NFS_SB(sb)->nfs_client->cl_nfs_mod,
-	};
+	struct nfs_fs_context *ctx = nfs_fc2context(fc);
+	struct dentry *dentry = ctx->clone_data.dentry;
 	struct nfs_server *server;
-	struct vfsmount *mnt;
-	char *page = (char *) __get_free_page(GFP_USER);
-	char *devname;
+	char *buffer, *p;
+	int ret;
 
-	if (page == NULL)
-		return ERR_PTR(-ENOMEM);
+	/* create a new volume representation */
+	server = ctx->mount_info.nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb),
+						     ctx->mount_info.mntfh,
+						     ctx->clone_data.fattr,
+						     ctx->selected_flavor);
 
-	server = mount_info.nfs_mod->rpc_ops->clone_server(NFS_SB(sb), fh,
-							   fattr, authflavor);
 	if (IS_ERR(server))
-		return ERR_CAST(server);
+		return PTR_ERR(server);
 
-	mount_info.server = server;
+	ctx->mount_info.server = server;
 
-	devname = nfs_devname(dentry, page, PAGE_SIZE);
-	if (IS_ERR(devname))
-		mnt = ERR_CAST(devname);
-	else
-		mnt = vfs_submount(dentry, &nfs_prepared_fs_type, devname, &mount_info);
+	buffer = kmalloc(4096, GFP_USER);
+	if (!buffer)
+		return -ENOMEM;
 
-	if (mount_info.server)
-		nfs_free_server(mount_info.server);
-	free_page((unsigned long)page);
-	return mnt;
+	ctx->internal		= true;
+	ctx->mount_info.inherited_bsize = ctx->clone_data.sb->s_blocksize_bits;
+
+	p = nfs_devname(dentry, buffer, 4096);
+	if (IS_ERR(p)) {
+		dprintk("NFS: Couldn't determine submount pathname\n");
+		ret = PTR_ERR(p);
+	} else {
+		ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p);
+		if (!ret)
+			ret = vfs_get_tree(fc);
+	}
+	kfree(buffer);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(nfs_do_submount);
 
-struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
-			      struct nfs_fh *fh, struct nfs_fattr *fattr)
+int nfs_submount(struct fs_context *fc, struct nfs_server *server)
 {
-	int err;
+	struct nfs_fs_context *ctx = nfs_fc2context(fc);
+	struct dentry *dentry = ctx->clone_data.dentry;
 	struct dentry *parent = dget_parent(dentry);
+	int err;
 
 	/* Look it up again to get its attributes */
-	err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL);
+	err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name,
+						  ctx->mount_info.mntfh, ctx->clone_data.fattr,
+						  NULL);
 	dput(parent);
 	if (err != 0)
-		return ERR_PTR(err);
+		return err;
 
-	return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
+	ctx->selected_flavor = server->client->cl_auth->au_flavor;
+	return nfs_do_submount(fc);
 }
 EXPORT_SYMBOL_GPL(nfs_submount);

fs/nfs/nfs3proc.c

@@ -990,7 +990,7 @@ const struct nfs_rpc_ops nfs_v3_clientops = {
 	.nlmclnt_ops	= &nlmclnt_fl_close_lock_ops,
 	.getroot	= nfs3_proc_get_root,
 	.submount	= nfs_submount,
-	.try_mount	= nfs_try_mount,
+	.try_get_tree	= nfs_try_get_tree,
 	.getattr	= nfs3_proc_getattr,
 	.setattr	= nfs3_proc_setattr,
 	.lookup		= nfs3_proc_lookup,

fs/nfs/nfs4_fs.h

@@ -268,14 +268,13 @@ extern const struct dentry_operations nfs4_dentry_operations;
 int nfs_atomic_open(struct inode *, struct dentry *, struct file *,
 		    unsigned, umode_t);
 
-/* super.c */
+/* fs_context.c */
 extern struct file_system_type nfs4_fs_type;
 
 /* nfs4namespace.c */
 struct rpc_clnt *nfs4_negotiate_security(struct rpc_clnt *, struct inode *,
 					 const struct qstr *);
-struct vfsmount *nfs4_submount(struct nfs_server *, struct dentry *,
-			       struct nfs_fh *, struct nfs_fattr *);
+int nfs4_submount(struct fs_context *, struct nfs_server *);
 int nfs4_replace_transport(struct nfs_server *server,
 				const struct nfs4_fs_locations *locations);
 
@@ -526,7 +525,6 @@ extern const nfs4_stateid invalid_stateid;
 /* nfs4super.c */
 struct nfs_mount_info;
 extern struct nfs_subversion nfs_v4;
-struct dentry *nfs4_try_mount(int, const char *, struct nfs_mount_info *);
 extern bool nfs4_disable_idmapping;
 extern unsigned short max_session_slots;
 extern unsigned short max_session_cb_slots;
@@ -536,6 +534,9 @@ extern bool recover_lost_locks;
 #define NFS4_CLIENT_ID_UNIQ_LEN		(64)
 extern char nfs4_client_id_uniquifier[NFS4_CLIENT_ID_UNIQ_LEN];
 
+extern int nfs4_try_get_tree(struct fs_context *);
+extern int nfs4_get_referral_tree(struct fs_context *);
+
 /* nfs4sysctl.c */
 #ifdef CONFIG_SYSCTL
 int nfs4_register_sysctl(void);

fs/nfs/nfs4file.c

@@ -7,6 +7,7 @@
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/falloc.h>
+#include <linux/mount.h>
 #include <linux/nfs_fs.h>
 #include "delegation.h"
 #include "internal.h"

fs/nfs/nfs4proc.c

@@ -10001,7 +10001,7 @@ const struct nfs_rpc_ops nfs_v4_clientops = {
 	.file_ops	= &nfs4_file_operations,
 	.getroot	= nfs4_proc_get_root,
 	.submount	= nfs4_submount,
-	.try_mount	= nfs4_try_mount,
+	.try_get_tree	= nfs4_try_get_tree,
 	.getattr	= nfs4_proc_getattr,
 	.setattr	= nfs4_proc_setattr,
 	.lookup		= nfs4_proc_lookup,

fs/nfs/nfs4super.c

@@ -4,6 +4,7 @@
  */
 #include <linux/init.h>
 #include <linux/module.h>
+#include <linux/mount.h>
 #include <linux/nfs4_mount.h>
 #include <linux/nfs_fs.h>
 #include "delegation.h"
@@ -18,16 +19,6 @@
 
 static int nfs4_write_inode(struct inode *inode, struct writeback_control *wbc);
 static void nfs4_evict_inode(struct inode *inode);
-static struct dentry *nfs4_referral_mount(struct file_system_type *fs_type,
-	int flags, const char *dev_name, void *raw_data);
-
-struct file_system_type nfs4_referral_fs_type = {
-	.owner		= THIS_MODULE,
-	.name		= "nfs4",
-	.mount		= nfs4_referral_mount,
-	.kill_sb	= nfs_kill_super,
-	.fs_flags	= FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
-};
 
 static const struct super_operations nfs4_sops = {
 	.alloc_inode	= nfs_alloc_inode,
@@ -41,7 +32,6 @@ static const struct super_operations nfs4_sops = {
 	.show_devname	= nfs_show_devname,
 	.show_path	= nfs_show_path,
 	.show_stats	= nfs_show_stats,
-	.remount_fs	= nfs_remount,
 };
 
 struct nfs_subversion nfs_v4 = {
@@ -147,102 +137,121 @@ static void nfs_referral_loop_unprotect(void)
 	kfree(p);
 }
 
-static struct dentry *do_nfs4_mount(struct nfs_server *server, int flags,
-				    struct nfs_mount_info *info,
-				    const char *hostname,
-				    const char *export_path)
+static int do_nfs4_mount(struct nfs_server *server,
+			 struct fs_context *fc,
+			 const char *hostname,
+			 const char *export_path)
 {
+	struct nfs_fs_context *root_ctx;
+	struct fs_context *root_fc;
 	struct vfsmount *root_mnt;
 	struct dentry *dentry;
-	char *root_devname;
-	int err;
 	size_t len;
+	int ret;
+
+	struct fs_parameter param = {
+		.key	= "source",
+		.type	= fs_value_is_string,
+		.dirfd	= -1,
+	};
 
 	if (IS_ERR(server))
-		return ERR_CAST(server);
+		return PTR_ERR(server);
 
-	len = strlen(hostname) + 5;
-	root_devname = kmalloc(len, GFP_KERNEL);
-	if (root_devname == NULL) {
+	root_fc = vfs_dup_fs_context(fc);
+	if (IS_ERR(root_fc)) {
 		nfs_free_server(server);
-		return ERR_PTR(-ENOMEM);
+		return PTR_ERR(root_fc);
+	}
+	kfree(root_fc->source);
+	root_fc->source = NULL;
+
+	root_ctx = nfs_fc2context(root_fc);
+	root_ctx->internal = true;
+	root_ctx->mount_info.server = server;
+	/* We leave export_path unset as it's not used to find the root. */
+
+	len = strlen(hostname) + 5;
+	param.string = kmalloc(len, GFP_KERNEL);
+	if (param.string == NULL) {
+		put_fs_context(root_fc);
+		return -ENOMEM;
 	}
 
 	/* Does hostname needs to be enclosed in brackets? */
 	if (strchr(hostname, ':'))
-		snprintf(root_devname, len, "[%s]:/", hostname);
+		param.size = snprintf(param.string, len, "[%s]:/", hostname);
 	else
-		snprintf(root_devname, len, "%s:/", hostname);
-	info->server = server;
-	root_mnt = vfs_kern_mount(&nfs_prepared_fs_type, flags, root_devname, info);
-	if (info->server)
-		nfs_free_server(info->server);
-	info->server = NULL;
-	kfree(root_devname);
+		param.size = snprintf(param.string, len, "%s:/", hostname);
+	ret = vfs_parse_fs_param(root_fc, &param);
+	kfree(param.string);
+	if (ret < 0) {
+		put_fs_context(root_fc);
+		return ret;
+	}
+	root_mnt = fc_mount(root_fc);
+	put_fs_context(root_fc);
 
 	if (IS_ERR(root_mnt))
-		return ERR_CAST(root_mnt);
+		return PTR_ERR(root_mnt);
 
-	err = nfs_referral_loop_protect();
-	if (err) {
+	ret = nfs_referral_loop_protect();
+	if (ret) {
 		mntput(root_mnt);
-		return ERR_PTR(err);
+		return ret;
 	}
 
 	dentry = mount_subtree(root_mnt, export_path);
 	nfs_referral_loop_unprotect();
 
-	return dentry;
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+
+	fc->root = dentry;
+	return 0;
 }
 
-struct dentry *nfs4_try_mount(int flags, const char *dev_name,
-			      struct nfs_mount_info *mount_info)
+int nfs4_try_get_tree(struct fs_context *fc)
 {
-	struct nfs_fs_context *ctx = mount_info->ctx;
-	struct dentry *res;
-
-	dfprintk(MOUNT, "--> nfs4_try_mount()\n");
+	struct nfs_fs_context *ctx = nfs_fc2context(fc);
+	int err;
 
-	res = do_nfs4_mount(nfs4_create_server(mount_info),
-			    flags, mount_info,
-			    ctx->nfs_server.hostname,
-			    ctx->nfs_server.export_path);
+	dfprintk(MOUNT, "--> nfs4_try_get_tree()\n");
 
-	dfprintk(MOUNT, "<-- nfs4_try_mount() = %d%s\n",
-		 PTR_ERR_OR_ZERO(res),
-		 IS_ERR(res) ? " [error]" : "");
-	return res;
+	/* We create a mount for the server's root, walk to the requested
+	 * location and then create another mount for that.
+	 */
+	err= do_nfs4_mount(nfs4_create_server(&ctx->mount_info),
+			   fc, ctx->nfs_server.hostname,
+			   ctx->nfs_server.export_path);
+	if (err) {
+		dfprintk(MOUNT, "<-- nfs4_try_get_tree() = %d [error]\n", err);
+	} else {
+		dfprintk(MOUNT, "<-- nfs4_try_get_tree() = 0\n");
+	}
+	return err;
 }
 
 /*
  * Create an NFS4 server record on referral traversal
  */
-static struct dentry *nfs4_referral_mount(struct file_system_type *fs_type,
-		int flags, const char *dev_name, void *raw_data)
+int nfs4_get_referral_tree(struct fs_context *fc)
 {
-	struct nfs_clone_mount *data = raw_data;
-	struct nfs_mount_info mount_info = {
-		.cloned = data,
-		.nfs_mod = &nfs_v4,
-	};
-	struct dentry *res;
+	struct nfs_fs_context *ctx = nfs_fc2context(fc);
+	int err;
 
 	dprintk("--> nfs4_referral_mount()\n");
 
-	mount_info.mntfh = nfs_alloc_fhandle();
-	if (!mount_info.mntfh)
-		return ERR_PTR(-ENOMEM);
-
-	res = do_nfs4_mount(nfs4_create_referral_server(mount_info.cloned,
-							mount_info.mntfh),
-			    flags, &mount_info, data->hostname, data->mnt_path);
-
-	dprintk("<-- nfs4_referral_mount() = %d%s\n",
-		PTR_ERR_OR_ZERO(res),
-		IS_ERR(res) ? " [error]" : "");
-
-	nfs_free_fhandle(mount_info.mntfh);
-	return res;
+	/* create a new volume representation */
+	err = do_nfs4_mount(nfs4_create_referral_server(&ctx->clone_data, ctx->mount_info.mntfh),
+			    fc, ctx->nfs_server.hostname,
+			    ctx->nfs_server.export_path);
+	if (err) {
+		dfprintk(MOUNT, "<-- nfs4_get_referral_tree() = %d [error]\n", err);
+	} else {
+		dfprintk(MOUNT, "<-- nfs4_get_referral_tree() = 0\n");
+	}
+	return err;
 }
 
 

fs/nfs/proc.c

@@ -710,7 +710,7 @@ const struct nfs_rpc_ops nfs_v2_clientops = {
 	.file_ops	= &nfs_file_operations,
 	.getroot	= nfs_proc_get_root,
 	.submount	= nfs_submount,
-	.try_mount	= nfs_try_mount,
+	.try_get_tree	= nfs_try_get_tree,
 	.getattr	= nfs_proc_getattr,
 	.setattr	= nfs_proc_setattr,
 	.lookup		= nfs_proc_lookup,

include/linux/nfs_xdr.h

@@ -1639,6 +1639,7 @@ struct nfs_subversion;
 struct nfs_mount_info;
 struct nfs_client_initdata;
 struct nfs_pageio_descriptor;
+struct fs_context;
 
 /*
  * RPC procedure vector for NFSv2/NFSv3 demuxing
@@ -1653,9 +1654,8 @@ struct nfs_rpc_ops {
 
 	int	(*getroot) (struct nfs_server *, struct nfs_fh *,
 			    struct nfs_fsinfo *);
-	struct vfsmount *(*submount) (struct nfs_server *, struct dentry *,
-				      struct nfs_fh *, struct nfs_fattr *);
-	struct dentry *(*try_mount) (int, const char *, struct nfs_mount_info *);
+	int	(*submount) (struct fs_context *, struct nfs_server *);
+	int	(*try_get_tree) (struct fs_context *);
 	int	(*getattr) (struct nfs_server *, struct nfs_fh *,
 			    struct nfs_fattr *, struct nfs4_label *,
 			    struct inode *);