From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Date: Wed, 20 Feb 2019 15:19:30 +0000
Subject: Re: [RESEND PATCH 0/7] Add FOLL_LONGTERM to GUP fast and use it
Message-Id: <20190220151930.GB11695@infradead.org>
List-Id: <linux-fbdev.vger.kernel.org>
References: <20190220053040.10831-1-ira.weiny@intel.com>
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To: ira.weiny@intel.com
Cc: John Hubbard <jhubbard@nvidia.com>, Andrew Morton <akpm@linux-foundation.org>, Michal Hocko <mhocko@suse.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Peter Zijlstra <peterz@infradead.org>, Jason Gunthorpe <jgg@ziepe.ca>, 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>, Paul Burton <paul.burton@mips.com>, James Hogan <jhogan@kernel.org>, linux-kernel@vger.kerne

On Tue, Feb 19, 2019 at 09:30:33PM -0800, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
> 
> Resending these as I had only 1 minor comment which I believe we have covered
> in this series.  I was anticipating these going through the mm tree as they
> depend on a cleanup patch there and the IB changes are very minor.  But they
> could just as well go through the IB tree.
> 
> NOTE: This series depends on my clean up patch to remove the write parameter
> from gup_fast_permitted()[1]
> 
> 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 of FS DAX pages.

This I don't get - if you do lock down long term mappings performance
of the actual get_user_pages call shouldn't matter to start with.

What do I miss?