From: Christoph Hellwig <hch@lst.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>,
Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
linux-xfs@vger.kernel.org, Jan Kara <jack@suse.cz>,
Arnd Bergmann <arnd@arndb.de>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Linux API <linux-api@vger.kernel.org>,
Dave Chinner <david@fromorbit.com>,
"J. Bruce Fields" <bfields@fieldses.org>,
Linux MM <linux-mm@kvack.org>, Jeff Moyer <jmoyer@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@kernel.org>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Jeff Layton <jlayton@poochiereds.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v9 0/6] MAP_DIRECT for DAX userspace flush
Date: Tue, 17 Oct 2017 08:46:47 +0200 [thread overview]
Message-ID: <20171017064647.GA15437@lst.de> (raw)
In-Reply-To: <CAPcyv4gtnZu7obG7UwaBq1-fwRZj06HCa=mjBfDKKgfp97nYaw@mail.gmail.com>
On Mon, Oct 16, 2017 at 12:44:31PM -0700, Dan Williams wrote:
> > While I agree with the need for a per-MR notification mechanism, one
> > thing we lose by walking away from MAP_DIRECT is a way for a
> > hypervisor to coordinate pass through of a DAX mapping to an RDMA
> > device in a guest. That will remain a case where we will still need to
> > use device-dax. I'm fine if that's the answer, but just want to be
> > clear about all the places we need to protect a DAX mapping against
> > RDMA from a non-ODP device.
>
> For this specific issue perhaps we promote FL_LAYOUT as a lease-type
> that can be set by fcntl().
I don't think it is a good userspace interface, mostly because it
is about things that don't matter for userspace (block mappings).
It makes sense as a kernel interface for callers that want to pin
down a memory long-term, but for userspace the fact that the block
mapping changes doesn't matter - it matters that their long term
pin is broken by something.
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next prev parent reply other threads:[~2017-10-17 6:46 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-12 0:47 [PATCH v9 0/6] MAP_DIRECT for DAX userspace flush Dan Williams
2017-10-12 0:47 ` [PATCH v9 1/6] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags Dan Williams
2017-10-12 13:51 ` Jan Kara
2017-10-12 16:32 ` Linus Torvalds
2017-10-16 7:38 ` Christoph Hellwig
2017-10-16 7:56 ` Jan Kara
2017-10-12 0:47 ` [PATCH v9 2/6] fs, mm: pass fd to ->mmap_validate() Dan Williams
2017-10-12 1:21 ` Al Viro
2017-10-12 1:28 ` Dan Williams
2017-10-12 2:17 ` Dan Williams
2017-10-12 3:44 ` Dan Williams
2017-10-12 0:47 ` [PATCH v9 3/6] fs: MAP_DIRECT core Dan Williams
2017-10-12 0:47 ` [PATCH v9 4/6] xfs: prepare xfs_break_layouts() for reuse with MAP_DIRECT Dan Williams
2017-10-12 0:47 ` [PATCH v9 5/6] fs, xfs, iomap: introduce break_layout_nowait() Dan Williams
2017-10-12 0:47 ` [PATCH v9 6/6] xfs: wire up MAP_DIRECT Dan Williams
2017-10-12 14:23 ` [PATCH v9 0/6] MAP_DIRECT for DAX userspace flush Christoph Hellwig
2017-10-12 17:41 ` Dan Williams
2017-10-13 6:57 ` Christoph Hellwig
2017-10-13 15:14 ` Dan Williams
2017-10-13 16:38 ` Jason Gunthorpe
2017-10-13 17:01 ` Dan Williams
2017-10-13 17:31 ` Jason Gunthorpe
2017-10-13 18:22 ` Dan Williams
2017-10-14 1:57 ` Jason Gunthorpe
2017-10-16 12:02 ` Sagi Grimberg
2017-10-19 6:02 ` Jason Gunthorpe
2017-10-16 7:30 ` Christoph Hellwig
2017-10-16 7:26 ` Christoph Hellwig
2017-10-16 12:07 ` Sagi Grimberg
2017-10-16 17:43 ` Dan Williams
2017-10-16 19:44 ` Dan Williams
2017-10-17 6:46 ` Christoph Hellwig [this message]
2017-10-16 7:22 ` Christoph Hellwig
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