Re: msync() bug

[Hugh Dickins]

On Mon, 9 Jul 2001, Linus Torvalds wrote:
> On Mon, 9 Jul 2001, Hugh Dickins wrote:
> > >
> > > that cannot happen, remap_pte_range only maps invalid pages or reserved
> > > pages.
> >
> > Anyone know why mmap() of /dev/mem behaves in this way - solves the
> > problem Andrew raises, but surely that could be solved in a better way?
> > Seems strange that mmap() cannot give you what read() and write() can.
> 
> Simple: we MUST NOT muck around with the page counts of random pages.

Of course.

> And if the pages aren't marked Reserved, the page counts _would_ get
> corrupted by the VM page handling.

As it stands, yes.  But shouldn't there be some kind of VM_ASIFRESERVED
vma flag to treat all its pages as if they were reserved, for /dev/mem?

Hugh