[PATCH] riscv: Allow PROT_WRITE-only mmap()

[SS JieJi]

> https://fars.ee/1sPb, showing *inconsistent* read results on -r- pages
> before/after a write attempt performed by the kernel.

That said, maybe prohibit mmap-ing -w- pages is not the best fix for
this issue. If -w- pages are irreplaceable for some use cases (and
hence need to be allowed), I'd suggest at least we need to re-fix the
read result inconsistency issue somewhere else despite simply
reverting the patch.

Yours, Pan Ruizhe