Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal

[Jason Gunthorpe]

On Thu, Jun 13, 2019 at 09:25:54AM -0700, Dan Williams wrote:
> On Thu, Jun 13, 2019 at 8:14 AM Jason Gunthorpe <jgg@xxxxxxxx> wrote:
> >
> > 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.
> 
> Oh, I must have missed where this conversation started talking about
> the driver-device fd. 

In the first paragraph above where Ira is musing about 'close a
specific file', he is talking about the driver-device fd.

Ie unilaterally closing /dev/uverbs as a punishment for an application
that used leases wrong: ie that released its lease with the RDMA is
still ongoing. 

Jason