Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT
From: Michal Hocko
Date: Wed Aug 26 2015 - 03:20:39 EST
On Tue 25-08-15 15:03:00, Eric B Munson wrote:
> Would you drop your objections to the VMA flag if I drop the portions of
> the patch that expose it to userspace?
> The rework to not use the VMA flag is pretty sizeable and is much more
> ugly IMO. I know that you are not wild about using bit 30 of 32 for
> this, but perhaps we can settle on not exporting it to userspace so we
> can reclaim it if we really need it in the future?
Yes, that would be definitely more acceptable for me. I do understand
that you are not wild about changing mremap behavior.
Anyway, I would really prefer if the vma flag was really used only at
few places - when we are clearing it along with VM_LOCKED (which could
be hidden in VM_LOCKED_CLEAR_MASK or something like that) and when we
decide whether the populate or not (this should be __mm_populate). But
maybe I am missing some call paths where gup is called unconditionally,
I haven't checked that.
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