exfat: free the sbi and iocharset in ->kill_sb

As a rule of thumb everything allocated to the fs_context and moved into
the super_block should be freed by ->kill_sb so that the teardown
handling doesn't need to be duplicated between the fill_super error
path and put_super.  Implement an exfat-specific kill_sb method to do
that and share the code with the mount contex free helper for the
mount error handling case.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Message-Id: <20230809220545.1308228-11-hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/exfat/super.c

@@ -41,9 +41,7 @@ static void exfat_put_super(struct super_block *sb)
 	mutex_unlock(&sbi->s_lock);
 
 	unload_nls(sbi->nls_io);
-	exfat_free_iocharset(sbi);
 	exfat_free_upcase_table(sbi);
-	kfree(sbi);
 }
 
 static int exfat_sync_fs(struct super_block *sb, int wait)
@@ -703,9 +701,6 @@ static int exfat_fill_super(struct super_block *sb, struct fs_context *fc)
 
 check_nls_io:
 	unload_nls(sbi->nls_io);
-	exfat_free_iocharset(sbi);
-	sb->s_fs_info = NULL;
-	kfree(sbi);
 	return err;
 }
 
@@ -714,14 +709,18 @@ static int exfat_get_tree(struct fs_context *fc)
 	return get_tree_bdev(fc, exfat_fill_super);
 }
 
+static void exfat_free_sbi(struct exfat_sb_info *sbi)
+{
+	exfat_free_iocharset(sbi);
+	kfree(sbi);
+}
+
 static void exfat_free(struct fs_context *fc)
 {
 	struct exfat_sb_info *sbi = fc->s_fs_info;
 
-	if (sbi) {
-		exfat_free_iocharset(sbi);
-		kfree(sbi);
-	}
+	if (sbi)
+		exfat_free_sbi(sbi);
 }
 
 static int exfat_reconfigure(struct fs_context *fc)
@@ -766,12 +765,21 @@ static int exfat_init_fs_context(struct fs_context *fc)
 	return 0;
 }
 
+static void exfat_kill_sb(struct super_block *sb)
+{
+	struct exfat_sb_info *sbi = sb->s_fs_info;
+
+	kill_block_super(sb);
+	if (sbi)
+		exfat_free_sbi(sbi);
+}
+
 static struct file_system_type exfat_fs_type = {
 	.owner			= THIS_MODULE,
 	.name			= "exfat",
 	.init_fs_context	= exfat_init_fs_context,
 	.parameters		= exfat_parameters,
-	.kill_sb		= kill_block_super,
+	.kill_sb		= exfat_kill_sb,
 	.fs_flags		= FS_REQUIRES_DEV,
 };