On Mon 06-08-18 13:48:35, Yang Shi wrote: > > > On 8/6/18 1:41 PM, Michal Hocko wrote: > > On Mon 06-08-18 09:46:30, Yang Shi wrote: > > > > > > On 8/6/18 2:40 AM, Michal Hocko wrote: > > > > On Fri 03-08-18 14:01:58, Yang Shi wrote: > > > > > On 8/3/18 2:07 AM, Michal Hocko wrote: > > > > > > On Fri 27-07-18 02:10:14, Yang Shi wrote: > > [...] > > > > > > > If the vma has VM_LOCKED | VM_HUGETLB | VM_PFNMAP or uprobe, they are > > > > > > > considered as special mappings. They will be dealt with before zapping > > > > > > > pages with write mmap_sem held. Basically, just update vm_flags. > > > > > > Well, I think it would be safer to simply fallback to the current > > > > > > implementation with these mappings and deal with them on top. This would > > > > > > make potential issues easier to bisect and partial reverts as well. > > > > > Do you mean just call do_munmap()? It sounds ok. Although we may waste some > > > > > cycles to repeat what has done, it sounds not too bad since those special > > > > > mappings should be not very common. > > > > VM_HUGETLB is quite spread. Especially for DB workloads. > > > Wait a minute. In this way, it sounds we go back to my old implementation > > > with special handling for those mappings with write mmap_sem held, right? > > Yes, I would really start simple and add further enhacements on top. > > If updating vm_flags with read lock is safe in this case, we don't have to > do this. The only reason for this special handling is about vm_flags update. Yes, maybe you are right that this is safe. I would still argue to have it in a separate patch for easier review, bisectability etc... -- Michal Hocko SUSE Labs
