netdev - Re: [RESEND PATCH 0/7] Add FOLL_LONGTERM to GUP fast and use it

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Date:   Tue, 19 Mar 2019 15:19:30 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     ira.weiny@...el.com
Cc:     John Hubbard <jhubbard@...dia.com>, Michal Hocko <mhocko@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "David S. Miller" <davem@...emloft.net>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Rich Felker <dalias@...c.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [RESEND PATCH 0/7] Add FOLL_LONGTERM to GUP fast and use it

On Sun, 17 Mar 2019 11:34:31 -0700 ira.weiny@...el.com wrote:

> Resending after rebasing to the latest mm tree.
> 
> HFI1, qib, and mthca, use get_user_pages_fast() due to it performance
> advantages.  These pages can be held for a significant time.  But
> get_user_pages_fast() does not protect against mapping FS DAX pages.
> 
> Introduce FOLL_LONGTERM and use this flag in get_user_pages_fast() which
> retains the performance while also adding the FS DAX checks.  XDP has also
> shown interest in using this functionality.[1]
> 
> In addition we change get_user_pages() to use the new FOLL_LONGTERM flag and
> remove the specialized get_user_pages_longterm call.

It would be helpful to include your response to Christoph's question
(http://lkml.kernel.org/r/20190220180255.GA12020@iweiny-DESK2.sc.intel.com)
in the changelog.  Because if one person was wondering about this,
others will likely do so.

We have no record of acks or reviewed-by's.  At least one was missed
(http://lkml.kernel.org/r/CAOg9mSTTcD-9bCSDfC0WRYqfVrNB4TwOzL0c4+6QXi-N_Y43Vw@mail.gmail.com),
but that is very very partial.

This patchset is fairly DAX-centered, but Dan wasn't cc'ed!

So ho hum.  I'll scoop them up and shall make the above changes to the
[1/n] changelog, but we still have some work to do.