On Mon 23-01-23 18:23:08, Matthew Wilcox wrote: > On Mon, Jan 23, 2023 at 09:46:20AM -0800, Suren Baghdasaryan wrote: [...] > > Yes, batching the vmas into a list and draining it in remove_mt() and > > exit_mmap() as you suggested makes sense to me and is quite simple. > > Let's do that if nobody has objections. > > I object. We *know* nobody has a reference to any of the VMAs because > you have to have a refcount on the mm before you can get a reference > to a VMA. If Michal is saying that somebody could do: > > mmget(mm); > vma = find_vma(mm); > lock_vma(vma); > mmput(mm); > vma->a = b; > unlock_vma(mm, vma); > > then that's something we'd catch in review -- you obviously can't use > the mm after you've dropped your reference to it. I am not claiming this is possible now. I do not think we want to have something like that in the future either but that is really hard to envision. I am claiming that it is subtle and potentially error prone to have two different ways of mass vma freeing wrt. locking. Also, don't we have a very similar situation during last munmaps? -- Michal Hocko SUSE Labs
