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Date:   Mon, 25 Mar 2019 07:54:11 -0700
From:   Ira Weiny <ira.weiny@intel.com>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Jason Gunthorpe <jgg@ziepe.ca>,
        Andrew Morton <akpm@linux-foundation.org>,
        John Hubbard <jhubbard@nvidia.com>,
        Michal Hocko <mhocko@suse.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        "David S. Miller" <davem@davemloft.net>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Rich Felker <dalias@libc.org>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Ralf Baechle <ralf@linux-mips.org>,
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Subject: Re: [RESEND 4/7] mm/gup: Add FOLL_LONGTERM capability to GUP fast
Message-ID: <20190325145411.GI16366@iweiny-DESK2.sc.intel.com>
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On Mon, Mar 25, 2019 at 03:36:28PM -0700, Dan Williams wrote:
> On Mon, Mar 25, 2019 at 3:22 PM Ira Weiny <ira.weiny@intel.com> wrote:
> [..]
> > FWIW this thread is making me think my original patch which simply implemented
> > get_user_pages_fast_longterm() would be more clear.  There is some evidence
> > that the GUP API was trending that way (see get_user_pages_remote).  That seems
> > wrong but I don't know how to ensure users don't specify the wrong flag.
> 
> What about just making the existing get_user_pages_longterm() have a
> fast path option?

That would work but was not the direction we agreed upon before.[1]

At this point I would rather see this patch set applied, focus on fixing the
filesystem issues, and once that is done determine if FOLL_LONGTERM is needed
in any GUP calls.

Ira

[1] https://lkml.org/lkml/2019/2/11/2038