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From: Dave Chinner <david@fromorbit.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jan Kara <jack@suse.cz>, Jerome Glisse <jglisse@redhat.com>,
	John Hubbard <jhubbard@nvidia.com>,
	Matthew Wilcox <willy@infradead.org>,
	Dan Williams <dan.j.williams@intel.com>,
	John Hubbard <john.hubbard@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux MM <linux-mm@kvack.org>,
	tom@talpey.com, Al Viro <viro@zeniv.linux.org.uk>,
	benve@cisco.com, Christoph Hellwig <hch@infradead.org>,
	Christopher Lameter <cl@linux.com>,
	"Dalessandro, Dennis" <dennis.dalessandro@intel.com>,
	Doug Ledford <dledford@redhat.com>,
	Michal Hocko <mhocko@kernel.org>,
	mike.marciniszyn@intel.com, rcampbell@nvidia.com,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions
Date: Wed, 19 Dec 2018 21:28:25 +1100
Message-ID: <20181219102825.GN6311@dastard> (raw)
In-Reply-To: <20181219030329.GI21992@ziepe.ca>

On Tue, Dec 18, 2018 at 08:03:29PM -0700, Jason Gunthorpe wrote:
> On Wed, Dec 19, 2018 at 10:42:54AM +1100, Dave Chinner wrote:
> 
> > Essentially, what we are talking about is how to handle broken
> > hardware. I say we should just brun it with napalm and thermite
> > (i.e. taint the kernel with "unsupportable hardware") and force
> > wait_for_stable_page() to trigger when there are GUP mappings if
> > the underlying storage doesn't already require it.
> 
> If you want to ban O_DIRECT/etc from writing to file backed pages,
> then just do it.

O_DIRECT IO *isn't the problem*.


iO_DIRECT IO uses a short term pin that the existing prefaulting
during GUP works just fine for. The problem we have is the long term
pins where pages can be cleaned while the pages are pinned. i.e. the
use case we current have to disable for DAX because *we can't make
it work sanely* without either revokable file leases and/or hardware
that is able to trigger page faults when they need write access to a
clean page.

> Otherwise I'm not sure demanding some unrealistic HW design is
> reasonable. ie nvme drives are not likely to add page faulting to
> their IO path any time soon.

Direct IO on nvme drives are not the problem. It's RDMA pinning
pages for hours or days and expecting everyone else to jump through
hoops to support their broken page access access model.

> A SW architecture that relies on page faulting is just not going to
> support real world block IO devices.

The existing software architecture for file backed pages has been
based around page faulting for write notifications since ~2005. That
horse bolted many, many years ago.

> GPUs and one RDMA are about the only things that can do this today,
> and they are basically irrelevant to O_DIRECT.

It's RDMA that we need these changes for, not O_DIRECT.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  parent reply index

Thread overview: 213+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-04  0:17 [PATCH 0/2] put_user_page*(): start converting the call sites john.hubbard
2018-12-04  0:17 ` [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions john.hubbard
2018-12-04  7:53   ` Mike Rapoport
2018-12-05  1:40     ` John Hubbard
2018-12-04 20:28   ` Dan Williams
2018-12-04 21:56     ` John Hubbard
2018-12-04 23:03       ` Dan Williams
2018-12-05  0:36         ` Jerome Glisse
2018-12-05  0:40           ` Dan Williams
2018-12-05  0:59             ` John Hubbard
2018-12-05  0:58         ` John Hubbard
2018-12-05  1:00           ` Dan Williams
2018-12-05  1:15           ` Matthew Wilcox
2018-12-05  1:44             ` Jerome Glisse
2018-12-05  1:57               ` John Hubbard
2018-12-07  2:45                 ` John Hubbard
2018-12-07 19:16                   ` Jerome Glisse
2018-12-07 19:26                     ` Dan Williams
2018-12-07 19:40                       ` Jerome Glisse
2018-12-08  0:52                     ` John Hubbard
2018-12-08  2:24                       ` Jerome Glisse
2018-12-10 10:28                         ` Jan Kara
2018-12-12 15:03                           ` Jerome Glisse
2018-12-12 16:27                             ` Dan Williams
2018-12-12 17:02                               ` Jerome Glisse
2018-12-12 17:49                                 ` Dan Williams
2018-12-12 19:07                                   ` John Hubbard
2018-12-12 21:30                               ` Jerome Glisse
2018-12-12 21:40                                 ` Dan Williams
2018-12-12 21:53                                   ` Jerome Glisse
2018-12-12 22:11                                     ` Matthew Wilcox
2018-12-12 22:16                                       ` Jerome Glisse
2018-12-12 23:37                                     ` Jason Gunthorpe
2018-12-12 23:46                                       ` John Hubbard
2018-12-12 23:54                                       ` Dan Williams
2018-12-13  0:01                                       ` Jerome Glisse
2018-12-13  0:18                                         ` Dan Williams
2018-12-13  0:44                                           ` Jerome Glisse
2018-12-13  3:26                                             ` Jason Gunthorpe
2018-12-13  3:20                                         ` Jason Gunthorpe
2018-12-13 12:43                                           ` Jerome Glisse
2018-12-13 13:40                                             ` Tom Talpey
2018-12-13 14:18                                               ` Jerome Glisse
2018-12-13 14:51                                                 ` Tom Talpey
2018-12-13 15:18                                                   ` Jerome Glisse
2018-12-13 18:12                                                     ` Tom Talpey
2018-12-13 19:18                                                       ` Jerome Glisse
2018-12-14 10:41                                             ` Jan Kara
2018-12-14 15:25                                               ` Jerome Glisse
2018-12-12 21:56                                 ` John Hubbard
2018-12-12 22:04                                   ` Jerome Glisse
2018-12-12 22:11                                     ` John Hubbard
2018-12-12 22:14                                       ` Jerome Glisse
2018-12-12 22:17                                         ` John Hubbard
2018-12-12 21:46                             ` Dave Chinner
2018-12-12 21:59                               ` Jerome Glisse
2018-12-13  0:51                                 ` Dave Chinner
2018-12-13  2:02                                   ` Jerome Glisse
2018-12-13 15:56                                     ` Christopher Lameter
2018-12-13 16:02                                       ` Jerome Glisse
2018-12-14  6:00                                     ` Dave Chinner
2018-12-14 15:13                                       ` Jerome Glisse
2018-12-14  3:52                                   ` John Hubbard
2018-12-14  5:21                                     ` Dan Williams
2018-12-14  6:11                                       ` John Hubbard
2018-12-14 15:20                                         ` Jerome Glisse
2018-12-14 19:38                                         ` Dan Williams
2018-12-14 19:48                                           ` Matthew Wilcox
2018-12-14 19:53                                             ` Dave Hansen
2018-12-14 20:03                                               ` Matthew Wilcox
2018-12-14 20:17                                                 ` Dan Williams
2018-12-14 20:29                                                   ` Matthew Wilcox
2018-12-15  0:41                                                 ` John Hubbard
2018-12-17  8:56                                           ` Jan Kara
2018-12-17 18:28                                             ` Dan Williams
2018-12-14 15:43                               ` Jan Kara
2018-12-16 21:58                                 ` Dave Chinner
2018-12-17 18:11                                   ` Jerome Glisse
2018-12-17 18:34                                     ` Matthew Wilcox
2018-12-17 19:48                                       ` Jerome Glisse
2018-12-17 19:51                                         ` Matthew Wilcox
2018-12-17 19:54                                           ` Jerome Glisse
2018-12-17 19:59                                             ` Matthew Wilcox
2018-12-17 20:55                                               ` Jerome Glisse
2018-12-17 21:03                                                 ` Matthew Wilcox
2018-12-17 21:15                                                   ` Jerome Glisse
2018-12-18  1:09                                       ` Dave Chinner
2018-12-18  6:12                                       ` Darrick J. Wong
2018-12-18  9:30                                       ` Jan Kara
2018-12-18 23:29                                         ` John Hubbard
2018-12-19  2:07                                           ` Jerome Glisse
2018-12-19 11:08                                             ` Jan Kara
2018-12-20 10:54                                               ` John Hubbard
2018-12-20 16:50                                                 ` Jerome Glisse
2018-12-20 16:57                                                   ` Dan Williams
2018-12-20 16:49                                               ` Jerome Glisse
2019-01-03  1:55                                               ` Jerome Glisse
2019-01-03  3:27                                                 ` John Hubbard
2019-01-03 14:57                                                   ` Jerome Glisse
2019-01-03  9:26                                                 ` Jan Kara
2019-01-03 14:44                                                   ` Jerome Glisse
2019-01-11  2:59                                                     ` John Hubbard
2019-01-11  2:59                                                       ` John Hubbard
2019-01-11 16:51                                                       ` Jerome Glisse
2019-01-11 16:51                                                         ` Jerome Glisse
2019-01-12  1:04                                                         ` John Hubbard
2019-01-12  1:04                                                           ` John Hubbard
2019-01-12  2:02                                                           ` Jerome Glisse
2019-01-12  2:02                                                             ` Jerome Glisse
2019-01-12  2:38                                                             ` John Hubbard
2019-01-12  2:38                                                               ` John Hubbard
2019-01-12  2:46                                                               ` Jerome Glisse
2019-01-12  2:46                                                                 ` Jerome Glisse
2019-01-12  3:06                                                                 ` John Hubbard
2019-01-12  3:06                                                                   ` John Hubbard
2019-01-12  3:25                                                                   ` Jerome Glisse
2019-01-12  3:25                                                                     ` Jerome Glisse
2019-01-12 20:46                                                                     ` John Hubbard
2019-01-12 20:46                                                                       ` John Hubbard
2019-01-14 14:54                                                                   ` Jan Kara
2019-01-14 14:54                                                                     ` Jan Kara
2019-01-14 17:21                                                                     ` Jerome Glisse
2019-01-14 17:21                                                                       ` Jerome Glisse
2019-01-14 19:09                                                                       ` John Hubbard
2019-01-14 19:09                                                                         ` John Hubbard
2019-01-15  8:34                                                                         ` Jan Kara
2019-01-15  8:34                                                                           ` Jan Kara
2019-01-15 21:39                                                                           ` John Hubbard
2019-01-15 21:39                                                                             ` John Hubbard
2019-01-15  8:07                                                                       ` Jan Kara
2019-01-15  8:07                                                                         ` Jan Kara
2019-01-15 17:15                                                                         ` Jerome Glisse
2019-01-15 17:15                                                                           ` Jerome Glisse
2019-01-15 21:56                                                                           ` John Hubbard
2019-01-15 21:56                                                                             ` John Hubbard
2019-01-15 22:12                                                                             ` Jerome Glisse
2019-01-15 22:12                                                                               ` Jerome Glisse
2019-01-16  0:44                                                                               ` John Hubbard
2019-01-16  0:44                                                                                 ` John Hubbard
2019-01-16  1:56                                                                                 ` Jerome Glisse
2019-01-16  1:56                                                                                   ` Jerome Glisse
2019-01-16  2:01                                                                                   ` Dan Williams
2019-01-16  2:01                                                                                     ` Dan Williams
2019-01-16  2:23                                                                                     ` Jerome Glisse
2019-01-16  2:23                                                                                       ` Jerome Glisse
2019-01-16  4:34                                                                                       ` Dave Chinner
2019-01-16  4:34                                                                                         ` Dave Chinner
2019-01-16 14:50                                                                                         ` Jerome Glisse
2019-01-16 14:50                                                                                           ` Jerome Glisse
2019-01-16 22:51                                                                                           ` Dave Chinner
2019-01-16 22:51                                                                                             ` Dave Chinner
2019-01-16 11:38                                                                         ` Jan Kara
2019-01-16 11:38                                                                           ` Jan Kara
2019-01-16 13:08                                                                           ` Jerome Glisse
2019-01-16 13:08                                                                             ` Jerome Glisse
2019-01-17  5:42                                                                             ` John Hubbard
2019-01-17  5:42                                                                               ` John Hubbard
2019-01-17 15:21                                                                               ` Jerome Glisse
2019-01-17 15:21                                                                                 ` Jerome Glisse
2019-01-18  0:16                                                                                 ` Dave Chinner
2019-01-18  1:59                                                                                   ` Jerome Glisse
2019-01-17  9:30                                                                             ` Jan Kara
2019-01-17  9:30                                                                               ` Jan Kara
2019-01-17 15:17                                                                               ` Jerome Glisse
2019-01-17 15:17                                                                                 ` Jerome Glisse
2019-01-22 15:24                                                                                 ` Jan Kara
2019-01-22 16:46                                                                                   ` Jerome Glisse
2019-01-23 18:02                                                                                     ` Jan Kara
2019-01-23 19:04                                                                                       ` Jerome Glisse
2019-01-29  0:22                                                                                         ` John Hubbard
2019-01-29  1:23                                                                                           ` Jerome Glisse
2019-01-29  6:41                                                                                             ` John Hubbard
2019-01-29 10:12                                                                                               ` Jan Kara
2019-01-30  2:21                                                                                                 ` John Hubbard
2019-01-17  5:25                                                                         ` John Hubbard
2019-01-17  5:25                                                                           ` John Hubbard
2019-01-17  9:04                                                                           ` Jan Kara
2019-01-17  9:04                                                                             ` Jan Kara
2019-01-12  3:14                                                               ` Jerome Glisse
2019-01-12  3:14                                                                 ` Jerome Glisse
2018-12-18 10:33                                   ` Jan Kara
2018-12-18 23:42                                     ` Dave Chinner
2018-12-19  3:03                                       ` Jason Gunthorpe
2018-12-19  5:26                                         ` Dan Williams
2018-12-19 11:19                                           ` Jan Kara
2018-12-19 10:28                                         ` Dave Chinner [this message]
2018-12-19 11:35                                           ` Jan Kara
2018-12-19 16:56                                             ` Jason Gunthorpe
2018-12-19 22:33                                             ` Dave Chinner
2018-12-20  9:07                                               ` Jan Kara
2018-12-20 16:54                                               ` Jerome Glisse
2018-12-19 13:24                                       ` Jan Kara
2018-12-08  5:18                       ` Matthew Wilcox
2018-12-12 19:13                         ` John Hubbard
2018-12-08  7:16                       ` Dan Williams
2018-12-08 16:33                         ` Jerome Glisse
2018-12-08 16:48                           ` Christoph Hellwig
2018-12-08 17:47                             ` Jerome Glisse
2018-12-08 18:26                               ` Christoph Hellwig
2018-12-08 18:45                                 ` Jerome Glisse
2018-12-08 18:09                             ` Dan Williams
2018-12-08 18:12                               ` Christoph Hellwig
2018-12-11  6:18                               ` Dave Chinner
2018-12-05  5:52             ` Dan Williams
2018-12-05 11:16       ` Jan Kara
2018-12-04  0:17 ` [PATCH 2/2] infiniband/mm: convert put_page() to put_user_page*() john.hubbard
2018-12-04 17:10 ` [PATCH 0/2] put_user_page*(): start converting the call sites David Laight
2018-12-05  1:05   ` John Hubbard
2018-12-05 14:08     ` David Laight
2018-12-28  8:37       ` Pavel Machek
2019-02-08  7:56 [PATCH 0/2] mm: put_user_page() call site conversion first john.hubbard
2019-02-08  7:56 ` [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions john.hubbard
2019-02-08 10:32   ` Mike Rapoport
2019-02-08 20:44     ` John Hubbard

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