On Tue, Jul 23, 2019 at 04:30:16PM -0700, Ralph Campbell wrote: > hmm_range_snapshot() and hmm_range_fault() both call find_vma() and > walk_page_range() in a loop. This is unnecessary duplication since > walk_page_range() calls find_vma() in a loop already. > Simplify hmm_range_snapshot() and hmm_range_fault() by defining a > walk_test() callback function to filter unhandled vmas.
I like the approach a lot! But we really need to sort out the duplication between hmm_range_fault and hmm_range_snapshot first, as they are basically the same code. I have patches here: http://git.infradead.org/users/hch/misc.git/commitdiff/a34ccd30ee8a8a3111d9e91711c12901ed7dea74 http://git.infradead.org/users/hch/misc.git/commitdiff/81f442ebac7170815af7770a1efa9c4ab662137e That being said we don't really have any users for the snapshot mode or non-blocking faults, and I don't see any in the immediate pipeline either. It might actually be a better idea to just kill that stuff off for now until we have a user, as code without users is per definition untested and will just bitrot and break. > + const unsigned long device_vma = VM_IO | VM_PFNMAP | VM_MIXEDMAP; > + struct hmm_vma_walk *hmm_vma_walk = walk->private; > + struct hmm_range *range = hmm_vma_walk->range; > + struct vm_area_struct *vma = walk->vma; > + > + /* If range is no longer valid, force retry. */ > + if (!range->valid) > + return -EBUSY; > + > + if (vma->vm_flags & device_vma) Can we just kill off this odd device_vma variable? if (vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP)) and maybe add a comment on why we are skipping them (because they don't have struct page backing I guess..)
