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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri, 11 Sep 2020 12:09:25 -0700
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Subject: Re: [PATCH] mm/gup: fix gup_fast with dynamic page table folding
To: Vasily Gorbik <gor@linux.ibm.com>
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On Fri, Sep 11, 2020 at 12:04 PM Vasily Gorbik <gor@linux.ibm.com> wrote:
>
> Currently to make sure that every page table entry is read just once
> gup_fast walks perform READ_ONCE and pass pXd value down to the next
> gup_pXd_range function by value e.g.:
[ ... ]

Ack, this looks sane to me.

I was going to ask how horrible it would be to convert all the other
users, but a quick grep convinced me that yeah, it's only GUP that is
this special, and we don't want to make this interface be the real one
for everything else too..

                Linus