Re: [RFC v7 PATCH 4/4] mm: unmap special vmas with regular do_munmap()

[Michal Hocko]

On Fri 10-08-18 11:51:54, Vlastimil Babka wrote:
> On 08/10/2018 01:36 AM, Yang Shi wrote:
> > Unmapping vmas, which have VM_HUGETLB | VM_PFNMAP flag set or
> > have uprobes set, need get done with write mmap_sem held since
> > they may update vm_flags.
> > 
> > So, it might be not safe enough to deal with these kind of special
> > mappings with read mmap_sem. Deal with such mappings with regular
> > do_munmap() call.
> > 
> > Michal suggested to make this as a separate patch for safer and more
> > bisectable sake.
> 
> Hm I believe Michal meant the opposite "evolution" though. Patch 2/4
> should be done in a way that special mappings keep using the regular
> path, and this patch would convert them to the new path. Possibly even
> each special case separately.

yes, that is what I meant. Each of the special case should have its own
patch and changelog explaining why it is safe.
-- 
Michal Hocko
SUSE Labs