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

[Nicolas Pitre]

On Tue, 3 Oct 2017, Richard Weinberger wrote:

> On Mon, Oct 2, 2017 at 12:29 AM, Nicolas Pitre <nicolas.pitre@xxxxxxxxxx> wrote:
> > On Sun, 1 Oct 2017, Christoph Hellwig wrote:
> >
> >> up_read(&mm->mmap_sem) in the fault path is a still a complete
> >> no-go,
> >>
> >> NAK
> >
> > Care to elaborate?
> >
> > What about mm/filemap.c:__lock_page_or_retry() then?
> 
> As soon you up_read() in the page fault path other tasks will race
> with you before
> you're able to grab the write lock.

But I _know_ that.

Could you highlight an area in my code where this is not accounted for?


Nicolas