linux-ext4 - Re: [PATCH 2 2/2] xfs: fix rt

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Date:   Fri, 2 Feb 2018 14:20:23 +1100
From:   Dave Chinner <david@...morbit.com>
To:     Dave Jiang <dave.jiang@...el.com>
Cc:     darrick.wong@...cle.com, linux-xfs@...r.kernel.org,
        ross.zwisler@...ux.intel.com, linux-ext4@...r.kernel.org,
        dan.j.williams@...el.com, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH 2 2/2] xfs: fix rt_dev usage for DAX

On Thu, Feb 01, 2018 at 05:13:40PM -0700, Dave Jiang wrote:
> 
> 
> On 02/01/2018 04:44 PM, Dave Chinner wrote:
> > On Thu, Feb 01, 2018 at 01:33:05PM -0700, Dave Jiang wrote:
> >> When using realtime device (rtdev) with xfs where the data device is not
> >> DAX capable, two issues arise. One is when data device is not DAX but the
> >> realtime device is DAX capable, we currently disable DAX.
> >> After passing this check, we are also not marking the inode as DAX capable.
> >> This change will allow DAX enabled if the data device or the realtime
> >> device is DAX capable. S_DAX will be marked for the inode if the file is
> >> residing on a DAX capable device. This will prevent the case of rtdev is not
> >> DAX and data device is DAX to create realtime files.
> > 
> > I'm confused by this description. I'm not sure what is broken, nor
> > what you are trying to fix.
> > 
> > I think what you want to do is enable DAX on RT devices separately
> > to the data device and vice versa?
> > 
> > i.e. is this what you are trying to acheive?
> > 
> > datadev dax	rtdev dax		DAX enabled on
> > -----------     ---------		--------------
> > no		no			neither
> > yes		no			datadev
> > no		yes			rtdev
> > yes		yes			both
> 
> ^ Yes that's pretty much what I was trying to say. I probably should've
> just provided the table above.

Ok, good to know I understood what you want to achieve. Now we've
just got to work out how to do it. :)

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com