NFS: Fix a regression when loading the NFS v4 module

Some systems have a modprobe.d/nfs.conf file that sets an nfs4 alias
pointing to nfs.ko, rather than nfs4.ko.  This can prevent the v4 module
from loading on mount, since the kernel sees that something named "nfs4"
has already been loaded.  To work around this, I've renamed the modules
to "nfsv2.ko" "nfsv3.ko" and "nfsv4.ko".

I also had to move the nfs4_fs_type back to nfs.ko to ensure that `mount
-t nfs4` still works.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/Makefile

@@ -12,19 +12,19 @@ nfs-$(CONFIG_ROOT_NFS)	+= nfsroot.o
 nfs-$(CONFIG_SYSCTL)	+= sysctl.o
 nfs-$(CONFIG_NFS_FSCACHE) += fscache.o fscache-index.o
 
-obj-$(CONFIG_NFS_V2) += nfs2.o
-nfs2-y := nfs2super.o proc.o nfs2xdr.o
+obj-$(CONFIG_NFS_V2) += nfsv2.o
+nfsv2-y := nfs2super.o proc.o nfs2xdr.o
 
-obj-$(CONFIG_NFS_V3) += nfs3.o
-nfs3-y := nfs3super.o nfs3client.o nfs3proc.o nfs3xdr.o
-nfs3-$(CONFIG_NFS_V3_ACL) += nfs3acl.o
+obj-$(CONFIG_NFS_V3) += nfsv3.o
+nfsv3-y := nfs3super.o nfs3client.o nfs3proc.o nfs3xdr.o
+nfsv3-$(CONFIG_NFS_V3_ACL) += nfs3acl.o
 
-obj-$(CONFIG_NFS_V4) += nfs4.o
-nfs4-y := nfs4proc.o nfs4xdr.o nfs4state.o nfs4renewd.o nfs4super.o nfs4file.o \
+obj-$(CONFIG_NFS_V4) += nfsv4.o
+nfsv4-y := nfs4proc.o nfs4xdr.o nfs4state.o nfs4renewd.o nfs4super.o nfs4file.o \
 	  delegation.o idmap.o callback.o callback_xdr.o callback_proc.o \
 	  nfs4namespace.o nfs4getroot.o nfs4client.o
-nfs4-$(CONFIG_SYSCTL)	+= nfs4sysctl.o
-nfs4-$(CONFIG_NFS_V4_1)	+= pnfs.o pnfs_dev.o
+nfsv4-$(CONFIG_SYSCTL)	+= nfs4sysctl.o
+nfsv4-$(CONFIG_NFS_V4_1)	+= pnfs.o pnfs_dev.o
 
 obj-$(CONFIG_PNFS_FILE_LAYOUT) += nfs_layout_nfsv41_files.o
 nfs_layout_nfsv41_files-y := nfs4filelayout.o nfs4filelayoutdev.o

fs/nfs/client.c

@@ -105,7 +105,7 @@ struct nfs_subversion *get_nfs_version(unsigned int version)
 
 	if (IS_ERR(nfs)) {
 		mutex_lock(&nfs_version_mutex);
-		request_module("nfs%d", version);
+		request_module("nfsv%d", version);
 		nfs = find_nfs_version(version);
 		mutex_unlock(&nfs_version_mutex);
 	}

fs/nfs/nfs4_fs.h

@@ -205,6 +205,9 @@ extern const struct dentry_operations nfs4_dentry_operations;
 int nfs_atomic_open(struct inode *, struct dentry *, struct file *,
 		    unsigned, umode_t, int *);
 
+/* super.c */
+extern struct file_system_type nfs4_fs_type;
+
 /* nfs4namespace.c */
 rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *);
 struct rpc_clnt *nfs4_create_sec_client(struct rpc_clnt *, struct inode *, struct qstr *);

fs/nfs/nfs4super.c

@@ -23,14 +23,6 @@ static struct dentry *nfs4_referral_mount(struct file_system_type *fs_type,
 static struct dentry *nfs4_remote_referral_mount(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *raw_data);
 
-static struct file_system_type nfs4_fs_type = {
-	.owner		= THIS_MODULE,
-	.name		= "nfs4",
-	.mount		= nfs_fs_mount,
-	.kill_sb	= nfs_kill_super,
-	.fs_flags	= FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
-};
-
 static struct file_system_type nfs4_remote_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "nfs4",
@@ -344,14 +336,8 @@ static int __init init_nfs_v4(void)
 	if (err)
 		goto out1;
 
-	err = register_filesystem(&nfs4_fs_type);
-	if (err < 0)
-		goto out2;
-
 	register_nfs_version(&nfs_v4);
 	return 0;
-out2:
-	nfs4_unregister_sysctl();
 out1:
 	nfs_idmap_quit();
 out:
@@ -361,7 +347,6 @@ static int __init init_nfs_v4(void)
 static void __exit exit_nfs_v4(void)
 {
 	unregister_nfs_version(&nfs_v4);
-	unregister_filesystem(&nfs4_fs_type);
 	nfs4_unregister_sysctl();
 	nfs_idmap_quit();
 }

fs/nfs/super.c

@@ -319,6 +319,34 @@ EXPORT_SYMBOL_GPL(nfs_sops);
 static void nfs4_validate_mount_flags(struct nfs_parsed_mount_data *);
 static int nfs4_validate_mount_data(void *options,
 	struct nfs_parsed_mount_data *args, const char *dev_name);
+
+struct file_system_type nfs4_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "nfs4",
+	.mount		= nfs_fs_mount,
+	.kill_sb	= nfs_kill_super,
+	.fs_flags	= FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+};
+EXPORT_SYMBOL_GPL(nfs4_fs_type);
+
+static int __init register_nfs4_fs(void)
+{
+	return register_filesystem(&nfs4_fs_type);
+}
+
+static void unregister_nfs4_fs(void)
+{
+	unregister_filesystem(&nfs4_fs_type);
+}
+#else
+static int __init register_nfs4_fs(void)
+{
+	return 0;
+}
+
+static void unregister_nfs4_fs(void)
+{
+}
 #endif
 
 static struct shrinker acl_shrinker = {
@@ -337,12 +365,18 @@ int __init register_nfs_fs(void)
 	if (ret < 0)
 		goto error_0;
 
-	ret = nfs_register_sysctl();
+	ret = register_nfs4_fs();
 	if (ret < 0)
 		goto error_1;
+
+	ret = nfs_register_sysctl();
+	if (ret < 0)
+		goto error_2;
 	register_shrinker(&acl_shrinker);
 	return 0;
 
+error_2:
+	unregister_nfs4_fs();
 error_1:
 	unregister_filesystem(&nfs_fs_type);
 error_0:
@@ -356,6 +390,7 @@ void __exit unregister_nfs_fs(void)
 {
 	unregister_shrinker(&acl_shrinker);
 	nfs_unregister_sysctl();
+	unregister_nfs4_fs();
 	unregister_filesystem(&nfs_fs_type);
 }