On 10/9/19 9:20 PM, Linus Torvalds wrote:
No. Your logic is garbage. The above code is completely broken. YOU CAN NOT AVOID TRHE SPLIT AND THEN GO ON AT THE PTE LEVEL. Don't you get it? There *is* no PTE level if you didn't split.
Hmm, This paragraph makes me think we have very different perceptions about what I'm trying to achieve. I wanted the pte level to *only* get called for *pre-existing* pte entries. Surely those must be able to exist even if we don't split occasional huge pmds in the pagewalk code?
So what you should do is to just always return 0 in your pmd_entry(). Boom, done. The only reason for the pmd_entry existing at all is to get the warning. Then, if you don't want to split it, you make that warning just return an error (or a positive value) instead and say "ok, that was bad, we don't handle it at all". And in some _future_ life, if anybody wants to actually say "yeah, let's not split it", make it have some "yeah I handled it" case.
Well yes, this is exactly what I want. Because any huge pmd we encounter should be read-only.
/Thomas
