Re: [PATCH] 9p/virtio: restrict page pinning to user_backed_iter() iovec

asmadeus
2025-12-17T21:49:31Z

Christian Schoenebeck wrote on Wed, Dec 17, 2025 at 02:41:31PM +0100:
> Something's seriously messed up with 9p cache right now. With today's git
> master I do get data corruption in any 9p cache mode, including cache=mmap,
> only cache=none behaves clean.

Ugh...

> With this patch applied though it gets even worse as I can't even boot due to
> immediate 9p data corruption. Could be coincidence, as I get corruption
> without this patch in any cache mode as well, but at least I have to try much
> harder to trigger it.

As said before don't bother with this patch, it's definitely wrong --
we can't just use data->kvec->iov_base for bvec or folioq iters, so
there *will* be corruptions with this patch.

I'll try to see if I can produce anything wrong with master...
--
Dominique