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Date:   Thu, 6 Jun 2019 16:46:52 -0300
From:   Jason Gunthorpe <>
To:     Ira Weiny <>
Cc:     John Hubbard <>,
        Dan Williams <>,
        Jan Kara <>, Theodore Ts'o <>,
        Jeff Layton <>,
        Dave Chinner <>,
        Matthew Wilcox <>,,
        Andrew Morton <>,
        Jérôme Glisse <>,,,,,,
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.


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