linux-kernel - Re: [PATCH v2 2/7] dax: change bdev_dax_supported() to support boolean returns

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Message-ID: <20180601012657.GQ10363@dastard>
Date:   Fri, 1 Jun 2018 11:26:57 +1000
From:   Dave Chinner <david@...morbit.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Toshi Kani <toshi.kani@....com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Dave Jiang <dave.jiang@...el.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-xfs@...r.kernel.org
Subject: Re: [PATCH v2 2/7] dax: change bdev_dax_supported() to support
 boolean returns

On Thu, May 31, 2018 at 12:13:32PM -0700, Darrick J. Wong wrote:
> On Tue, May 29, 2018 at 04:01:14PM -0600, Ross Zwisler wrote:
> > On Tue, May 29, 2018 at 02:25:10PM -0700, Darrick J. Wong wrote:
> > > On Tue, May 29, 2018 at 01:51:01PM -0600, Ross Zwisler wrote:
> > > > From: Dave Jiang <dave.jiang@...el.com>
> > > > 
> > > > The function return values are confusing with the way the function is
> > > > named. We expect a true or false return value but it actually returns
> > > > 0/-errno.  This makes the code very confusing. Changing the return values
> > > > to return a bool where if DAX is supported then return true and no DAX
> > > > support returns false.
> > > > 
> > > > Signed-off-by: Dave Jiang <dave.jiang@...el.com>
> > > > Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> > > 
> > > Looks ok, do you want me to pull the first two patches through the xfs
> > > tree?
> > > 
> > > Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
> > 
> > Thanks for the review.
> > 
> > I'm not sure what's best.  If you do that then Mike will need to have a DM
> > branch for the rest of the series based on your stable commits, yea?
> > 
> > Mike what would you prefer?
> 
> I /was/ about to say that I would pull in the first two patches, but now
> I can't get xfs to mount with pmem at all, and have no way of testing
> this...?

I have similar problems, too, but:

$ ndctl list
[
  {
    "dev":"namespace1.0",
    "mode":"raw",
    "size":8589934592,
    "sector_size":512,
    "blockdev":"pmem1"
  },
  {
    "dev":"namespace0.0",
    "mode":"raw",
    "size":8589934592,
    "sector_size":512,
    "blockdev":"pmem0"
  }
]
$ sudo ndctl create-namespace -f -e namespace0.0 --mode=fsdax
  Error: operation failed, region0 fsdax mode not available

failed to reconfigure namespace: Invalid argument
$

I can't make head or tail of what is going wrong here - how am I
supposed to debug this and get it working again?

FWIW, XFS+DAX used to just work on this setup (I hadn't even
installed ndctl until this morning!) but after changing the kernel
it no longer works. That would make it a regression, yes?

Cheers,

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