From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Subject: Re: [PATCH v9 0/6] MAP_DIRECT for DAX userspace flush
Date: Thu, 19 Oct 2017 00:02:49 -0600
Message-ID: <20171019060249.GA6555@obsidianresearch.com>
References: <20171012142319.GA11254@lst.de>
 <CAPcyv4gTON__Ohop0B5R2gsKXC71bycTBozqGmF3WmwG9C6LVA@mail.gmail.com>
 <20171013065716.GB26461@lst.de>
 <CAPcyv4gaLBBefOU+8f7_ypYnCTjSMk+9nq8NfCqBHAE+NbUusw@mail.gmail.com>
 <20171013163822.GA17411@obsidianresearch.com>
 <CAPcyv4jDHp8z2VgVfyRK1WwMzixYVQnh54LZoPD57HB3yqSPPQ@mail.gmail.com>
 <20171013173145.GA18702@obsidianresearch.com>
 <CAPcyv4jZJRto1jwmNU--pqH_6dOVMyj=68ZwEjAmmkgX=mRk7w@mail.gmail.com>
 <20171014015752.GA25172@obsidianresearch.com>
 <e29eb9ed-2d87-cde8-4efa-50de1fff0c04@grimberg.me>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Return-path: <linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Content-Disposition: inline
In-Reply-To: <e29eb9ed-2d87-cde8-4efa-50de1fff0c04-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org>
Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: Sagi Grimberg <sagi-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org>
Cc: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, "J. Bruce Fields" <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>, Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Arnd Bergmann <arnd-r2nGTMty4D4@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>, Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>, Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Jeff Layton <jlayton-vpEMnDpepFuMZCB2o+C8xQ@public.gmane.org>, linux-fsdevel <linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
List-Id: linux-api@vger.kernel.org

On Mon, Oct 16, 2017 at 03:02:52PM +0300, Sagi Grimberg wrote:
> But why should the kernel ever need to mangle the CQ? if a lease break
> would deregister the MR the device is expected to generate remote
> protection errors on its own.

The point is to avoid protection errors - hittles change over when the
DAX mapping changes like ODP does.

Theonly way to get there is to notify the app before the mappings
change.. Dan suggested having ibv_pollcq return this indication..

Jason