Re: copy_from_user / copy_to_user with no swap space

[Horst H. von Brand]

mfbaustx <mfbaustx@xxxxxxxxx> wrote:
> >>> No. Your code may be only partially paged into RAM.
> >>> The same can happen for any mmaped data.

> That's what I thought I read.  But then my question is:  with
> on-demand  paging, is it possible to have two processes partially
> paged?

Why shouldn't they be? The whole idea is having just /parts/ (hopefully the
ones in active use) in memory.

>         Surely, it  MUST be the case that any processes with
> overlapping logical address  spaces must be paged coherently.

I don't know what this is supposed to mean...

>                                                                So,
> while on-demand "paging-in" allows  for partial paging of a process,
> is it the case that, on a context switch,  the user-space PTE's are
> completely erased (so that you get page-faults  and can then on-demand
> page them in...)?

Each process has its own page tables, they don't get in each others
hair. And the page tables precisely manage making several processes get
access to the /same/ logical addresses, but at /different/ physical
addresses.
-- 
Dr. Horst H. von Brand                   User #22616 counter.li.org
Departamento de Informatica                    Fono: +56 32 2654431
Universidad Tecnica Federico Santa Maria             +56 32 2654239
Casilla 110-V, Valparaiso, Chile               Fax:  +56 32 2797513
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/