Re: [PATCH 0/3] mm/mmap.c: don't unmap the overlapping VMA(s)

[Vlastimil Babka]

On 04/04/2016 09:31 AM, Michal Hocko wrote:
> On Sat 02-04-16 21:17:31, Piotr Kwapulinski wrote:
> > Currently the mmap(MAP_FIXED) discards the overlapping part of the
> > existing VMA(s).
> > Introduce the new MAP_DONTUNMAP flag which forces the mmap to fail
> > with ENOMEM whenever the overlapping occurs and MAP_FIXED is set.
> > No existing mapping(s) is discarded.
>
> You forgot to tell us what is the use case for this new flag.

Exactly. Also, returning ENOMEM is strange, EINVAL might be a better 
match, otherwise how would you distinguish a "geunine" ENOMEM from 
passing a wrong address?