From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH v9 2/6] fs, mm: pass fd to ->mmap_validate()
Date: Wed, 11 Oct 2017 18:28:32 -0700
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To: Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
Cc: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>, "Darrick J. Wong" <darrick.wong-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>, Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org" <linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>, Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>, linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>, linux-fsdevel <linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
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On Wed, Oct 11, 2017 at 6:21 PM, Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org> wrote:
> On Wed, Oct 11, 2017 at 05:47:18PM -0700, Dan Williams wrote:
>> The MAP_DIRECT mechanism for mmap intends to use a file lease to prevent
>> block map changes while the file is mapped. It requires the fd to setup
>> an fasync_struct for signalling lease break events to the lease holder.
>
> *UGH*
>
> That looks like one hell of a bad API.  You are not even guaranteed that
> descriptor will remain be still open by the time you pass it down to your
> helper, nevermind the moment when event actually happens...

What am I missing, fcntl(F_SETLEASE) seems to follow a similar pattern?