vfs: Convert efivarfs to use the new mount API

Convert the efivarfs filesystem to the new internal mount API as the old
one will be obsoleted and removed.  This allows greater flexibility in
communication of mount parameters between userspace, the VFS and the
filesystem.

[AV: get rid of efivarfs_sb nonsense - it has never been used]

See Documentation/filesystems/mount_api.txt for more information.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Matthew Garrett <matthew.garrett@nebula.com>
cc: Jeremy Kerr <jk@ozlabs.org>
cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
cc: linux-efi@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/efivarfs/super.c

@@ -10,6 +10,7 @@
 #include <linux/ctype.h>
 #include <linux/efi.h>
 #include <linux/fs.h>
+#include <linux/fs_context.h>
 #include <linux/module.h>
 #include <linux/pagemap.h>
 #include <linux/ucs2_string.h>
@@ -31,8 +32,6 @@ static const struct super_operations efivarfs_ops = {
 	.evict_inode = efivarfs_evict_inode,
 };
 
-static struct super_block *efivarfs_sb;
-
 /*
  * Compare two efivarfs file names.
  *
@@ -191,14 +190,12 @@ static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 	return 0;
 }
 
-static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
+static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct inode *inode = NULL;
 	struct dentry *root;
 	int err;
 
-	efivarfs_sb = sb;
-
 	sb->s_maxbytes          = MAX_LFS_FILESIZE;
 	sb->s_blocksize         = PAGE_SIZE;
 	sb->s_blocksize_bits    = PAGE_SHIFT;
@@ -226,16 +223,24 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 	return err;
 }
 
-static struct dentry *efivarfs_mount(struct file_system_type *fs_type,
-				    int flags, const char *dev_name, void *data)
+static int efivarfs_get_tree(struct fs_context *fc)
+{
+	return get_tree_single(fc, efivarfs_fill_super);
+}
+
+static const struct fs_context_operations efivarfs_context_ops = {
+	.get_tree	= efivarfs_get_tree,
+};
+
+static int efivarfs_init_fs_context(struct fs_context *fc)
 {
-	return mount_single(fs_type, flags, data, efivarfs_fill_super);
+	fc->ops = &efivarfs_context_ops;
+	return 0;
 }
 
 static void efivarfs_kill_sb(struct super_block *sb)
 {
 	kill_litter_super(sb);
-	efivarfs_sb = NULL;
 
 	/* Remove all entries and destroy */
 	__efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
@@ -244,7 +249,7 @@ static void efivarfs_kill_sb(struct super_block *sb)
 static struct file_system_type efivarfs_type = {
 	.owner   = THIS_MODULE,
 	.name    = "efivarfs",
-	.mount   = efivarfs_mount,
+	.init_fs_context = efivarfs_init_fs_context,
 	.kill_sb = efivarfs_kill_sb,
 };