NFS: ensure bdi_unregister is called on mount failure.

bdi_unregister is called by nfs_put_super which is only called by
generic_shutdown_super if ->s_root is not NULL.  So if we error out
in a circumstance where we called nfs_bdi_register (i.e. server !=
NULL) but have not set s_root, then we need to call bdi_unregister
explicitly in nfs_get_sb and various other *_get_sb() functions.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/super.c

@@ -2214,7 +2214,7 @@ static int nfs_get_sb(struct file_system_type *fs_type,
 	} else {
 		error = nfs_bdi_register(server);
 		if (error)
-			goto error_splat_super;
+			goto error_splat_bdi;
 	}
 
 	if (!s->s_root) {
@@ -2256,6 +2256,9 @@ static int nfs_get_sb(struct file_system_type *fs_type,
 error_splat_root:
 	dput(mntroot);
 error_splat_super:
+	if (server && !s->s_root)
+		bdi_unregister(&server->backing_dev_info);
+error_splat_bdi:
 	deactivate_locked_super(s);
 	goto out;
 }
@@ -2326,7 +2329,7 @@ static int nfs_xdev_get_sb(struct file_system_type *fs_type, int flags,
 	} else {
 		error = nfs_bdi_register(server);
 		if (error)
-			goto error_splat_super;
+			goto error_splat_bdi;
 	}
 
 	if (!s->s_root) {
@@ -2363,6 +2366,9 @@ static int nfs_xdev_get_sb(struct file_system_type *fs_type, int flags,
 	return error;
 
 error_splat_super:
+	if (server && !s->s_root)
+		bdi_unregister(&server->backing_dev_info);
+error_splat_bdi:
 	deactivate_locked_super(s);
 	dprintk("<-- nfs_xdev_get_sb() = %d [splat]\n", error);
 	return error;
@@ -2578,7 +2584,7 @@ static int nfs4_remote_get_sb(struct file_system_type *fs_type,
 	} else {
 		error = nfs_bdi_register(server);
 		if (error)
-			goto error_splat_super;
+			goto error_splat_bdi;
 	}
 
 	if (!s->s_root) {
@@ -2616,6 +2622,9 @@ static int nfs4_remote_get_sb(struct file_system_type *fs_type,
 error_splat_root:
 	dput(mntroot);
 error_splat_super:
+	if (server && !s->s_root)
+		bdi_unregister(&server->backing_dev_info);
+error_splat_bdi:
 	deactivate_locked_super(s);
 	goto out;
 }
@@ -2811,7 +2820,7 @@ static int nfs4_xdev_get_sb(struct file_system_type *fs_type, int flags,
 	} else {
 		error = nfs_bdi_register(server);
 		if (error)
-			goto error_splat_super;
+			goto error_splat_bdi;
 	}
 
 	if (!s->s_root) {
@@ -2847,6 +2856,9 @@ static int nfs4_xdev_get_sb(struct file_system_type *fs_type, int flags,
 	return error;
 
 error_splat_super:
+	if (server && !s->s_root)
+		bdi_unregister(&server->backing_dev_info);
+error_splat_bdi:
 	deactivate_locked_super(s);
 	dprintk("<-- nfs4_xdev_get_sb() = %d [splat]\n", error);
 	return error;
@@ -2893,7 +2905,7 @@ static int nfs4_remote_referral_get_sb(struct file_system_type *fs_type,
 	} else {
 		error = nfs_bdi_register(server);
 		if (error)
-			goto error_splat_super;
+			goto error_splat_bdi;
 	}
 
 	if (!s->s_root) {
@@ -2929,6 +2941,9 @@ static int nfs4_remote_referral_get_sb(struct file_system_type *fs_type,
 	return error;
 
 error_splat_super:
+	if (server && !s->s_root)
+		bdi_unregister(&server->backing_dev_info);
+error_splat_bdi:
 	deactivate_locked_super(s);
 	dprintk("<-- nfs4_referral_get_sb() = %d [splat]\n", error);
 	return error;