Re: MAP_FIXED for ELF mappings

[Michal Hocko]

On Thu 05-10-17 18:33:20, Oleg Nesterov wrote:
> On 10/04, Michal Hocko wrote:
> >
> > On Wed 04-10-17 23:12:38, Baoquan He wrote:
> > >  	if (total_size) {
> > >  		total_size = ELF_PAGEALIGN(total_size);
> > > -		map_addr = vm_mmap(filep, addr, total_size, prot, flags, off);
> > > -		if (!BAD_ADDR(map_addr))
> > > -			vm_munmap(map_addr+size, total_size-size);
> > > -	} else
> > > -		map_addr = vm_mmap(filep, addr, size, prot, flags, off);
> > > +		addr = get_unmapped_area(file, addr, total_size, off, flags);
> >
> > So how does this prevent clobbering an existing VMA when flags contains
> > MAP_FIXED?
> 
> I got lost...
> 
> this is just cleanup, it should not change the behaviour, with or without
> MAP_FIXED. It just avoids the mmap(total_size) + munmap(extra_size).

OK, I have clearly misunderstood the intention then.
-- 
Michal Hocko
SUSE Labs