vfs_read
ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
ret = vfs_read(fd_file(f), buf, count, ppos);
return vfs_read(fd_file(f), buf, count, &pos);
extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);