Kernel/LibC: Implement {,f}statvfs

kernel/include/kernel/FS/Inode.h

@@ -19,6 +19,8 @@
 namespace Kernel
 {
 
+	class FileSystem;
+
 	class FileBackedRegion;
 	class SharedFileData;
 
@@ -86,6 +88,8 @@ namespace Kernel
 		virtual bool is_pipe() const { return false; }
 		virtual bool is_tty() const { return false; }
 
+		virtual const FileSystem* filesystem() const = 0;
+
 		// Directory API
 		BAN::ErrorOr<BAN::RefPtr<Inode>> find_inode(BAN::StringView);
 		BAN::ErrorOr<size_t> list_next_inodes(off_t, struct dirent* list, size_t list_size);