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Date: Thu, 13 Jun 2019 12:13:54 -0300
From: Jason Gunthorpe <jgg@ziepe.ca>
Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal
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To: Dan Williams <dan.j.williams@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>, Jan Kara <jack@suse.cz>, Theodore Ts'o <tytso@mit.edu>, Jeff Layton <jlayton@kernel.org>, Dave Chinner <david@fromorbit.com>, Matthew Wilcox <willy@infradead.org>, linux-xfs <linux-xfs@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, John Hubbard <jhubbard@nvidia.com>, =?utf-8?B?SsOpcsO0bWU=?= Glisse <jglisse@redhat.com>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, linux-nvdimm <linux-nvdimm@lists.01.org>, linux-ext4 <linux-ext4@vger.kernel.org>, Linux MM <linux-mm@kvack.org>

On Wed, Jun 12, 2019 at 06:14:46PM -0700, Dan Williams wrote:
> > Effectively, we would need a way for an admin to close a specific file
> > descriptor (or set of fds) which point to that file.  AFAIK there is no way to
> > do that at all, is there?
> 
> Even if there were that gets back to my other question, does RDMA
> teardown happen at close(fd), or at final fput() of the 'struct
> file'?

AFAIK there is no kernel side driver hook for close(fd). 

rdma uses a normal chardev so it's lifetime is linked to the file_ops
release, which is called on last fput. So all the mmaps, all the dups,
everything must go before it releases its resources.

Jason