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I thought this would > > belong to the PAT object somehow? > > It's glued to a VMA. The only alternative to using a VMA field would be looking it > up for a VMA, storing it in an xarray etc ... ends up complicating stuff when there > is no need to right now. Yeah no, that'd be crazy. I guess we are stuck with this so need to think of a sensible way forward. > > > > > Though getting rid of VM_PAT would be fantastic... > > > > I wonder if a _general_ VMA ref count would be a bit much just for this > > case. > > I don't think it would be helpful for this case. It's much more similar to the anon > VMA name (that also has its own kref) Ahh I see, adding a field like this, that makes a lot more sense, obviously could put behind appropriate CONFIG_ flag. Given cacheline alignment probably have a bit of wiggle room there to avoid increasing VMA size also. > > > > > But maybe I misunderstand your approach :) Happy to obviously look and if > > not like some crazy thing just for PAT (you can understand why I would not > > like this) will be supportive :>) > > This is something quick (well, longer than I wish it would take) that seems to > work. There are smaller pat-internal cleanups to be had on top of this, and > the new functions shall be documented. > > > Observe how: > * We remove VM_PAT and that weird VM flags manipulation + "locked" flag > * We remove any traces of the nasty tracking handling from mremap+fork code > * Just like anon_vma_name, it hooks into vm_area_dup()/vm_area_free(). > * We remove the page table lookup via get_pat_info()->... completely > * We remove the VMA parameter from PAT code completely > * We reduce the track/untrack/sanitize interface to 3 functions Yeah this is all lovely! OK this should hopefully be workable then!