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Date: Thu, 6 Jun 2019 16:46:52 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Ira Weiny <ira.weiny@...el.com>
Cc: John Hubbard <jhubbard@...dia.com>,
Dan Williams <dan.j.williams@...el.com>,
Jan Kara <jack@...e.cz>, Theodore Ts'o <tytso@....edu>,
Jeff Layton <jlayton@...nel.org>,
Dave Chinner <david@...morbit.com>,
Matthew Wilcox <willy@...radead.org>,
linux-xfs@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Jérôme Glisse <jglisse@...hat.com>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-nvdimm@...ts.01.org, linux-ext4@...r.kernel.org,
linux-mm@...ck.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal
On Thu, Jun 06, 2019 at 10:11:58AM -0700, Ira Weiny wrote:
> 2) This is a bit more subtle and something I almost delayed sending these out
> for. Currently the implementation of a lease break actually removes the
> lease from the file. I did not want this to happen and I was thinking of
> delaying this patch set to implement something which keeps the lease around
> but I figured I should get something out for comments. Jan has proposed
> something along these lines and I agree with him so I'm going to ask you to
> read my response to him about the details.
>
>
> Anyway so the key here is that currently an app needs the SIGIO to retake
> the lease if they want to map the file again or in parts based on usage.
> For example, they may only want to map some of the file for when they are
> using it and then map another part later. Without the SIGIO they would lose
> their lease or would have to just take the lease for each GUP pin (which
> adds overhead). Like I said I did not like this but I left it to get
> something which works out.
So to be clear..
Even though the lease is broken the GUP remains, the pages remain
pined, and truncate/etc continues to fail?
I like Jan's take on this actually.. see other email.
Jason
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