From: Jason Gunthorpe <jgg@ziepe.ca>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Doug Ledford <dledford@redhat.com>,
Dave Chinner <david@fromorbit.com>,
Christopher Lameter <cl@linux.com>,
Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
Ira Weiny <ira.weiny@intel.com>,
lsf-pc@lists.linux-foundation.org,
linux-rdma <linux-rdma@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
John Hubbard <jhubbard@nvidia.com>,
Jerome Glisse <jglisse@redhat.com>,
Michal Hocko <mhocko@kernel.org>
Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA
Date: Wed, 6 Feb 2019 16:41:32 -0700 [thread overview]
Message-ID: <20190206234132.GB15234@ziepe.ca> (raw)
In-Reply-To: <CAPcyv4g2r=L3jfSDoRPt4VG7D_2CxCgv3s+JLu4FQRUSRWg+4Q@mail.gmail.com>
On Wed, Feb 06, 2019 at 03:30:27PM -0800, Dan Williams wrote:
> On Wed, Feb 6, 2019 at 3:21 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> >
> > On Wed, Feb 06, 2019 at 02:44:45PM -0800, Dan Williams wrote:
> >
> > > > Do they need to stick with xfs?
> > >
> > > Can you clarify the motivation for that question? This problem exists
> > > for any filesystem that implements an mmap that where the physical
> > > page backing the mapping is identical to the physical storage location
> > > for the file data.
> >
> > .. and needs to dynamicaly change that mapping. Which is not really
> > something inherent to the general idea of a filesystem. A file system
> > that had *strictly static* block assignments would work fine.
> >
> > Not all filesystem even implement hole punch.
> >
> > Not all filesystem implement reflink.
> >
> > ftruncate doesn't *have* to instantly return the free blocks to
> > allocation pool.
> >
> > ie this is not a DAX & RDMA issue but a XFS & RDMA issue.
> >
> > Replacing XFS is probably not be reasonable, but I wonder if a XFS--
> > operating mode could exist that had enough features removed to be
> > safe?
>
> You're describing the current situation, i.e. Linux already implements
> this, it's called Device-DAX and some users of RDMA find it
> insufficient. The choices are to continue to tell them "no", or say
> "yes, but you need to submit to lease coordination".
Device-DAX is not what I'm imagining when I say XFS--.
I mean more like XFS with all features that require rellocation of
blocks disabled.
Forbidding hold punch, reflink, cow, etc, doesn't devolve back to
device-dax.
Jason
next prev parent reply other threads:[~2019-02-06 23:41 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-05 17:50 [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA Ira Weiny
2019-02-05 18:01 ` Ira Weiny
2019-02-06 21:31 ` Dave Chinner
2019-02-06 9:50 ` Jan Kara
2019-02-06 17:31 ` Jason Gunthorpe
2019-02-06 17:52 ` Matthew Wilcox
2019-02-06 18:32 ` Doug Ledford
2019-02-06 18:35 ` Matthew Wilcox
2019-02-06 18:44 ` Doug Ledford
2019-02-06 18:52 ` Jason Gunthorpe
2019-02-06 19:45 ` Dan Williams
2019-02-06 20:14 ` Doug Ledford
2019-02-06 21:04 ` Dan Williams
2019-02-06 21:12 ` Doug Ledford
2019-02-06 19:16 ` Christopher Lameter
2019-02-06 19:40 ` Matthew Wilcox
2019-02-06 20:16 ` Doug Ledford
2019-02-06 20:20 ` Matthew Wilcox
2019-02-06 20:28 ` Doug Ledford
2019-02-06 20:41 ` Matthew Wilcox
2019-02-06 20:47 ` Doug Ledford
2019-02-06 20:49 ` Matthew Wilcox
2019-02-06 20:50 ` Doug Ledford
2019-02-06 20:31 ` Jason Gunthorpe
2019-02-06 20:39 ` Christopher Lameter
2019-02-06 20:54 ` Doug Ledford
2019-02-07 16:48 ` Jan Kara
2019-02-06 20:24 ` Christopher Lameter
2019-02-06 21:03 ` Dave Chinner
2019-02-06 22:08 ` Jason Gunthorpe
2019-02-06 22:24 ` Doug Ledford
2019-02-06 22:44 ` Dan Williams
2019-02-06 23:21 ` Jason Gunthorpe
2019-02-06 23:30 ` Dan Williams
2019-02-06 23:41 ` Jason Gunthorpe [this message]
2019-02-07 0:22 ` Dan Williams
2019-02-07 5:33 ` Jason Gunthorpe
2019-02-07 1:57 ` Doug Ledford
2019-02-07 2:48 ` Dan Williams
2019-02-07 2:42 ` Doug Ledford
2019-02-07 3:13 ` Dan Williams
2019-02-07 17:23 ` Ira Weiny
2019-02-07 16:25 ` Doug Ledford
2019-02-07 16:55 ` Christopher Lameter
2019-02-07 17:35 ` Ira Weiny
2019-02-07 18:17 ` Christopher Lameter
2019-02-08 4:43 ` Dave Chinner
2019-02-08 11:10 ` Jan Kara
2019-02-08 20:50 ` Dan Williams
2019-02-11 10:24 ` Jan Kara
2019-02-11 17:22 ` Dan Williams
2019-02-11 18:06 ` Jason Gunthorpe
2019-02-11 18:15 ` Dan Williams
2019-02-11 18:19 ` Ira Weiny
2019-02-11 18:26 ` Jason Gunthorpe
2019-02-11 18:40 ` Matthew Wilcox
2019-02-11 19:58 ` Dan Williams
2019-02-11 20:49 ` Jason Gunthorpe
2019-02-11 21:02 ` Dan Williams
2019-02-11 21:09 ` Jason Gunthorpe
2019-02-12 16:34 ` Jan Kara
2019-02-12 16:55 ` Christopher Lameter
2019-02-13 15:06 ` Jan Kara
2019-02-12 16:36 ` Christopher Lameter
2019-02-12 16:44 ` Jan Kara
2019-02-11 21:08 ` Jerome Glisse
2019-02-11 21:22 ` John Hubbard
2019-02-11 22:12 ` Jason Gunthorpe
2019-02-11 22:33 ` John Hubbard
2019-02-12 16:39 ` Christopher Lameter
2019-02-13 2:58 ` John Hubbard
2019-02-12 16:28 ` Jan Kara
2019-02-14 20:26 ` Jerome Glisse
2019-02-14 20:50 ` Matthew Wilcox
2019-02-14 21:39 ` Jerome Glisse
2019-02-15 1:19 ` Dave Chinner
2019-02-15 15:42 ` Christopher Lameter
2019-02-15 18:08 ` Matthew Wilcox
2019-02-15 18:31 ` Christopher Lameter
2019-02-15 22:00 ` Jason Gunthorpe
2019-02-15 23:38 ` Ira Weiny
2019-02-16 22:42 ` Dave Chinner
2019-02-17 2:54 ` Christopher Lameter
2019-02-12 16:07 ` Jan Kara
2019-02-12 21:53 ` Dan Williams
2019-02-08 21:20 ` Dave Chinner
2019-02-08 15:33 ` Christopher Lameter
2019-02-07 17:24 ` Matthew Wilcox
2019-02-07 17:26 ` Jason Gunthorpe
2019-02-07 3:52 ` Dave Chinner
2019-02-07 5:23 ` Jason Gunthorpe
2019-02-07 6:00 ` Dan Williams
2019-02-07 17:17 ` Jason Gunthorpe
2019-02-07 23:54 ` Dan Williams
2019-02-08 1:44 ` Ira Weiny
2019-02-08 5:19 ` Jason Gunthorpe
2019-02-08 7:20 ` Dan Williams
2019-02-08 15:42 ` Jason Gunthorpe
2019-02-07 15:04 ` Chuck Lever
2019-02-07 15:28 ` Tom Talpey
2019-02-07 15:37 ` Doug Ledford
2019-02-07 15:41 ` Tom Talpey
2019-02-07 15:56 ` Doug Ledford
2019-02-07 16:57 ` Ira Weiny
2019-02-07 21:31 ` Tom Talpey
2019-02-07 16:54 ` Ira Weiny
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