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