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Message-ID: <20210111160549.GN504133@ziepe.ca>
Date: Mon, 11 Jan 2021 12:05:49 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: John Hubbard <jhubbard@...dia.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux-MM <linux-mm@...ck.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Yu Zhao <yuzhao@...gle.com>, Andy Lutomirski <luto@...nel.org>,
Peter Xu <peterx@...hat.com>,
Pavel Emelyanov <xemul@...nvz.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Mike Rapoport <rppt@...ux.vnet.ibm.com>,
Minchan Kim <minchan@...nel.org>,
Will Deacon <will@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Hugh Dickins <hughd@...gle.com>,
"Kirill A. Shutemov" <kirill@...temov.name>,
Matthew Wilcox <willy@...radead.org>,
Oleg Nesterov <oleg@...hat.com>, Jann Horn <jannh@...gle.com>,
Kees Cook <keescook@...omium.org>,
Leon Romanovsky <leonro@...dia.com>, Jan Kara <jack@...e.cz>,
Kirill Tkhai <ktkhai@...tuozzo.com>,
Nadav Amit <nadav.amit@...il.com>, Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH 0/1] mm: restore full accuracy in COW page reuse
On Sun, Jan 10, 2021 at 11:26:57PM -0800, John Hubbard wrote:
> So:
>
> FOLL_PIN: would use DMA_PIN_COUNTING_BIAS to increment page refcount.
> These are long term pins for dma.
>
> FOLL_GET: would use GUP_PIN_COUNTING_BIAS to increment page refcount.
> These are not long term pins.
Do we have any places yet that care about the long-term-ness?
The only place long term would matter is if something is waiting for
the page ref count to drop.
Jason
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