From: Dave Chinner <david@fromorbit.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>,
linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org,
"John Hubbard" <jhubbard@nvidia.com>,
"Jeff Layton" <jlayton@kernel.org>,
linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Jérôme Glisse" <jglisse@redhat.com>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
"Jan Kara" <jack@suse.cz>,
linux-ext4@vger.kernel.org,
"Andrew Morton" <akpm@linux-foundation.org>
Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal
Date: Fri, 14 Jun 2019 13:07:12 +1000 [thread overview]
Message-ID: <20190614030712.GO14363@dread.disaster.area> (raw)
In-Reply-To: <20190614023107.GK32656@bombadil.infradead.org>
On Thu, Jun 13, 2019 at 07:31:07PM -0700, Matthew Wilcox wrote:
> On Fri, Jun 14, 2019 at 12:09:21PM +1000, Dave Chinner wrote:
> > If the lease holder modifies the mapping in a way that causes it's
> > own internal state to screw up, then that's a bug in the lease
> > holder application.
>
> Sounds like the lease semantics aren't the right ones for the longterm
> GUP users then. The point of the longterm GUP is so the pages can be
> written to, and if the filesystem is going to move the pages around when
> they're written to, that just won't work.
And now we go full circle back to the constraints we decided on long
ago because we can't rely on demand paging RDMA hardware any time
soon to do everything we need to transparently support long-term GUP
on file-backed mappings. i.e.:
RDMA to file backed mappings must first preallocate and
write zeros to the range of the file they are mapping so
that the filesystem block mapping is complete and static for
the life of the RDMA mapping that will pin it.
IOWs, the layout lease will tell the RDMA application that the
static setup it has already done to work correctly with a file
backed mapping may be about to be broken by a third party.....
-Dave.
--
Dave Chinner
david@fromorbit.com
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>
To: Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: "Theodore Ts'o" <tytso-3s7WtUTddSA@public.gmane.org>,
linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
"John Hubbard" <jhubbard-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
"Jeff Layton" <jlayton-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
"Jason Gunthorpe" <jgg-uk2M96/98Pc@public.gmane.org>,
"Jérôme Glisse" <jglisse-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
"Jan Kara" <jack-AlSwsSmVLrQ@public.gmane.org>,
linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
"Andrew Morton"
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal
Date: Fri, 14 Jun 2019 13:07:12 +1000 [thread overview]
Message-ID: <20190614030712.GO14363@dread.disaster.area> (raw)
In-Reply-To: <20190614023107.GK32656-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>
On Thu, Jun 13, 2019 at 07:31:07PM -0700, Matthew Wilcox wrote:
> On Fri, Jun 14, 2019 at 12:09:21PM +1000, Dave Chinner wrote:
> > If the lease holder modifies the mapping in a way that causes it's
> > own internal state to screw up, then that's a bug in the lease
> > holder application.
>
> Sounds like the lease semantics aren't the right ones for the longterm
> GUP users then. The point of the longterm GUP is so the pages can be
> written to, and if the filesystem is going to move the pages around when
> they're written to, that just won't work.
And now we go full circle back to the constraints we decided on long
ago because we can't rely on demand paging RDMA hardware any time
soon to do everything we need to transparently support long-term GUP
on file-backed mappings. i.e.:
RDMA to file backed mappings must first preallocate and
write zeros to the range of the file they are mapping so
that the filesystem block mapping is complete and static for
the life of the RDMA mapping that will pin it.
IOWs, the layout lease will tell the RDMA application that the
static setup it has already done to work correctly with a file
backed mapping may be about to be broken by a third party.....
-Dave.
--
Dave Chinner
david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Jason Gunthorpe" <jgg@ziepe.ca>,
"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
"Dan Williams" <dan.j.williams@intel.com>,
"Theodore Ts'o" <tytso@mit.edu>,
"Jeff Layton" <jlayton@kernel.org>,
linux-xfs@vger.kernel.org,
"Andrew Morton" <akpm@linux-foundation.org>,
"John Hubbard" <jhubbard@nvidia.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org,
linux-mm@kvack.org, linux-rdma@vger.kernel.org
Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal
Date: Fri, 14 Jun 2019 13:07:12 +1000 [thread overview]
Message-ID: <20190614030712.GO14363@dread.disaster.area> (raw)
In-Reply-To: <20190614023107.GK32656@bombadil.infradead.org>
On Thu, Jun 13, 2019 at 07:31:07PM -0700, Matthew Wilcox wrote:
> On Fri, Jun 14, 2019 at 12:09:21PM +1000, Dave Chinner wrote:
> > If the lease holder modifies the mapping in a way that causes it's
> > own internal state to screw up, then that's a bug in the lease
> > holder application.
>
> Sounds like the lease semantics aren't the right ones for the longterm
> GUP users then. The point of the longterm GUP is so the pages can be
> written to, and if the filesystem is going to move the pages around when
> they're written to, that just won't work.
And now we go full circle back to the constraints we decided on long
ago because we can't rely on demand paging RDMA hardware any time
soon to do everything we need to transparently support long-term GUP
on file-backed mappings. i.e.:
RDMA to file backed mappings must first preallocate and
write zeros to the range of the file they are mapping so
that the filesystem block mapping is complete and static for
the life of the RDMA mapping that will pin it.
IOWs, the layout lease will tell the RDMA application that the
static setup it has already done to work correctly with a file
backed mapping may be about to be broken by a third party.....
-Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2019-06-14 3:08 UTC|newest]
Thread overview: 136+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-06 1:45 [PATCH RFC 00/10] RDMA/FS DAX truncate proposal ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-06 1:45 ` [PATCH RFC 01/10] fs/locks: Add trace_leases_conflict ira.weiny
2019-06-09 12:52 ` Jeff Layton
2019-06-06 1:45 ` [PATCH RFC 02/10] fs/locks: Export F_LAYOUT lease to user space ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-09 13:00 ` Jeff Layton
2019-06-09 13:00 ` Jeff Layton
2019-06-11 21:38 ` Ira Weiny
2019-06-11 21:38 ` Ira Weiny
2019-06-12 9:46 ` Jan Kara
2019-06-06 1:45 ` [PATCH RFC 03/10] mm/gup: Pass flags down to __gup_device_huge* calls ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-06 6:18 ` Christoph Hellwig
2019-06-06 16:10 ` Ira Weiny
2019-06-06 1:45 ` [PATCH RFC 04/10] mm/gup: Ensure F_LAYOUT lease is held prior to GUP'ing pages ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-06 1:45 ` [PATCH RFC 05/10] fs/ext4: Teach ext4 to break layout leases ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-06 1:45 ` [PATCH RFC 06/10] fs/ext4: Teach dax_layout_busy_page() to operate on a sub-range ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-06 1:45 ` [PATCH RFC 07/10] fs/ext4: Fail truncate if pages are GUP pinned ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-06 10:58 ` Jan Kara
2019-06-06 10:58 ` Jan Kara
2019-06-06 16:17 ` Ira Weiny
2019-06-06 1:45 ` [PATCH RFC 08/10] fs/xfs: Teach xfs to use new dax_layout_busy_page() ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-06 1:45 ` [PATCH RFC 09/10] fs/xfs: Fail truncate if pages are GUP pinned ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-06 1:45 ` [PATCH RFC 10/10] mm/gup: Remove FOLL_LONGTERM DAX exclusion ira.weiny
2019-06-06 1:45 ` ira.weiny
2019-06-06 5:52 ` [PATCH RFC 00/10] RDMA/FS DAX truncate proposal John Hubbard
2019-06-06 5:52 ` John Hubbard
2019-06-06 17:11 ` Ira Weiny
2019-06-06 17:11 ` Ira Weiny
2019-06-06 19:46 ` Jason Gunthorpe
2019-06-06 10:42 ` Jan Kara
2019-06-06 15:35 ` Dan Williams
2019-06-06 19:51 ` Jason Gunthorpe
2019-06-06 22:22 ` Ira Weiny
2019-06-07 10:36 ` Jan Kara
2019-06-07 12:17 ` Jason Gunthorpe
2019-06-07 14:52 ` Ira Weiny
2019-06-07 14:52 ` Ira Weiny
2019-06-07 15:10 ` Jason Gunthorpe
2019-06-12 10:29 ` Jan Kara
2019-06-12 10:29 ` Jan Kara
2019-06-12 11:47 ` Jason Gunthorpe
2019-06-12 12:09 ` Jan Kara
2019-06-12 12:09 ` Jan Kara
2019-06-12 18:41 ` Dan Williams
2019-06-13 7:17 ` Jan Kara
2019-06-13 7:17 ` Jan Kara
2019-06-12 19:14 ` Jason Gunthorpe
2019-06-12 22:13 ` Ira Weiny
2019-06-12 22:54 ` Dan Williams
2019-06-12 22:54 ` Dan Williams
2019-06-12 23:33 ` Ira Weiny
2019-06-12 23:33 ` Ira Weiny
2019-06-13 1:14 ` Dan Williams
2019-06-13 1:14 ` Dan Williams
2019-06-13 15:13 ` Jason Gunthorpe
2019-06-13 16:25 ` Dan Williams
2019-06-13 16:25 ` Dan Williams
2019-06-13 17:18 ` Jason Gunthorpe
2019-06-13 16:53 ` Dan Williams
2019-06-13 16:53 ` Dan Williams
2019-06-13 15:12 ` Jason Gunthorpe
2019-06-13 7:53 ` Jan Kara
2019-06-13 7:53 ` Jan Kara
2019-06-12 18:49 ` Dan Williams
2019-06-12 18:49 ` Dan Williams
2019-06-13 7:43 ` Jan Kara
2019-06-06 22:03 ` Ira Weiny
2019-06-06 22:03 ` Ira Weiny
2019-06-06 22:26 ` Ira Weiny
2019-06-06 22:28 ` Dave Chinner
2019-06-07 11:04 ` Jan Kara
2019-06-07 18:25 ` Ira Weiny
2019-06-07 18:25 ` Ira Weiny
2019-06-07 18:25 ` Ira Weiny
2019-06-07 18:50 ` Jason Gunthorpe
2019-06-08 0:10 ` Dave Chinner
2019-06-08 0:10 ` Dave Chinner
2019-06-09 1:29 ` Ira Weiny
2019-06-09 1:29 ` Ira Weiny
2019-06-09 1:29 ` Ira Weiny
2019-06-12 12:37 ` Matthew Wilcox
2019-06-12 12:37 ` Matthew Wilcox
2019-06-12 12:37 ` Matthew Wilcox
2019-06-12 23:30 ` Ira Weiny
2019-06-12 23:30 ` Ira Weiny
2019-06-12 23:30 ` Ira Weiny
2019-06-13 0:55 ` Dave Chinner
2019-06-13 0:55 ` Dave Chinner
2019-06-13 0:55 ` Dave Chinner
2019-06-13 20:34 ` Ira Weiny
2019-06-13 20:34 ` Ira Weiny
2019-06-13 20:34 ` Ira Weiny
2019-06-14 3:42 ` Dave Chinner
2019-06-13 0:25 ` Dave Chinner
2019-06-13 0:25 ` Dave Chinner
2019-06-13 3:23 ` Matthew Wilcox
2019-06-13 3:23 ` Matthew Wilcox
2019-06-13 3:23 ` Matthew Wilcox
2019-06-13 4:36 ` Dave Chinner
2019-06-13 4:36 ` Dave Chinner
2019-06-13 4:36 ` Dave Chinner
2019-06-13 10:47 ` Matthew Wilcox
2019-06-13 10:47 ` Matthew Wilcox
2019-06-13 10:47 ` Matthew Wilcox
2019-06-13 15:29 ` Jason Gunthorpe
2019-06-13 15:27 ` Matthew Wilcox
2019-06-13 15:27 ` Matthew Wilcox
2019-06-13 15:27 ` Matthew Wilcox
2019-06-13 21:13 ` Ira Weiny
2019-06-13 21:13 ` Ira Weiny
2019-06-13 23:45 ` Jason Gunthorpe
2019-06-14 0:00 ` Ira Weiny
2019-06-14 0:00 ` Ira Weiny
2019-06-14 2:09 ` Dave Chinner
2019-06-14 2:09 ` Dave Chinner
2019-06-14 2:09 ` Dave Chinner
2019-06-14 2:31 ` Matthew Wilcox
2019-06-14 2:31 ` Matthew Wilcox
2019-06-14 3:07 ` Dave Chinner [this message]
2019-06-14 3:07 ` Dave Chinner
2019-06-14 3:07 ` Dave Chinner
2019-06-20 14:52 ` Jan Kara
2019-06-20 14:52 ` Jan Kara
2019-06-13 20:34 ` Ira Weiny
2019-06-13 20:34 ` Ira Weiny
2019-06-13 20:34 ` Ira Weiny
2019-06-14 2:58 ` Dave Chinner
2019-06-14 2:58 ` Dave Chinner
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