Re: [PATCH v4 4/5] cramfs: add mmap support

From: Nicolas Pitre
Date: Sun Oct 01 2017 - 18:29:33 EST

On Sun, 1 Oct 2017, Christoph Hellwig wrote:

> up_read(&mm->mmap_sem) in the fault path is a still a complete
> no-go,

Care to elaborate?

What about mm/filemap.c:__lock_page_or_retry() then?

Why the special handling on mm->mmap_sem with VM_FAULT_RETRY?

What are the potential problems with my approach I didn't cover yet?

Serious: I'm simply looking for solutions here.