On Mon, Apr 13, 2020 at 08:04:10PM -0400, Yan Zhao wrote: > > I can't think of another way for a kernel thread to have a mm indeed. > for example, before calling to vfio_dma_rw(), a kernel thread has already > called use_mm(), then its current->mm is not null, and it has flag > PF_KTHREAD. > in this case, we just want to allow the copy_to_user() directly if > current->mm == mm, rather than call another use_mm() again. > > do you think it makes sense? I mean no other way than using use_mm. That being said nesting potentional use_mm callers sounds like a rather bad idea, and we should avoid that.
