It is possible to seek past the end of the file when FMODE_UNSIGNED_OFFSET. This would result in undefined behavior, which is bad.

I would restructure this code to explicitly handle the case where FMODE_UNSIGNED_OFFSET is set and the case where FMODE_UNSIGNED_OFFSET is unset. This could be done something like this:

```
if (filp->f_mode & FMODE_UNSIGNED_OFFSET) {
if ((unsigned loff_t) offset > (unsigned loff_t) inode->i_sb->s_maxbytes)
error = -EINVAL;
} else if (offset < 0 || offset > inode->i_sb->s_maxbytes)
error = -EINVAL;
```