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From: Dave Chinner <david@fromorbit.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
	Mike Snitzer <snitzer@redhat.com>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-xfs <linux-xfs@vger.kernel.org>,
	device-mapper development <dm-devel@redhat.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v2 2/7] dax: change bdev_dax_supported() to support boolean returns
Date: Fri, 1 Jun 2018 12:24:18 +1000	[thread overview]
Message-ID: <20180601022418.GR10363@dastard> (raw)
In-Reply-To: <CAPcyv4g6dv9sG9dR-iY+aEfSi2r3ey1dXGbX-nexKsN72t0QMw@mail.gmail.com>

On Thu, May 31, 2018 at 06:57:33PM -0700, Dan Williams wrote:
> On Thu, May 31, 2018 at 6:26 PM, Dave Chinner <david@fromorbit.com> wrote:
> > 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@intel.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@intel.com>
> >> > > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.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@oracle.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?
> 
> This commit caused the behavior change:
> 
>     569d0365f571 dax: require 'struct page' by default for filesystem dax
> 
> The justification is in that patch, but the short summary is we killed
> off "pageless" dax because it had so many incomplete holes and
> surprise behaviors. It needed to die on the path to making dax not
> experimental, i.e. to close safety holes, and be feature complete for
> all the ways userspace expects to use mappings (direct-io, fork,
> poison handling, etc).
> 
> I suspect your kernel does not have CONFIG_ZONE_DEVICE enabled which
> has the following dependencies:
> 
>         depends on MEMORY_HOTPLUG
>         depends on MEMORY_HOTREMOVE
>         depends on SPARSEMEM_VMEMMAP

Filesystem DAX now has a dependency on memory hotplug?

Fmeh. No wonder I never enabled CONFIG_ZONE_DEVICE. It's described in
menuconfig as "Device memory (pmem, HMM, etc...) hotplug support".
This isn't for hotplug support - it required for basic DAX
functionality. I've never enabled memory hotplug in any of my test
kernel configs, because the VMs I run the kernels on don't ever get
memory hotplugged....

OK, works now I've found the magic config incantantions to turn
everything I now need on.

Can we get this rationalised to a single top level config
option in the filesystems menu "Enable Filesystem DAX" that turns
on every knob that is required?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  reply	other threads:[~2018-06-01  2:24 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-29 19:50 [PATCH v2 0/7] Fix DM DAX handling Ross Zwisler
2018-05-29 19:51 ` [PATCH v2 1/7] fs: allow per-device dax status checking for filesystems Ross Zwisler
2018-05-29 19:51 ` [PATCH v2 2/7] dax: change bdev_dax_supported() to support boolean returns Ross Zwisler
2018-05-29 21:25   ` Darrick J. Wong
2018-05-29 22:01     ` Ross Zwisler
2018-05-31 19:13       ` Darrick J. Wong
2018-05-31 20:34         ` Ross Zwisler
2018-05-31 20:35         ` Dan Williams
2018-05-31 20:41         ` Ross Zwisler
2018-05-31 20:52         ` Mike Snitzer
2018-05-31 22:26           ` [dm-devel] " Darrick J. Wong
2018-06-01 20:59             ` Ross Zwisler
2018-06-01  1:26         ` Dave Chinner
2018-06-01  1:57           ` Dan Williams
2018-06-01  2:24             ` Dave Chinner [this message]
2018-06-01  4:02               ` Dan Williams
2018-06-03 22:20                 ` Dave Chinner
2018-06-04  0:25                   ` Dave Chinner
2018-06-04  1:48                     ` Dan Williams
2018-06-04 23:40                       ` Dan Williams
2018-06-05  0:33                         ` Mike Snitzer
2018-06-05  5:55                           ` Dave Chinner
2018-06-05  3:32                         ` Dan Williams
2018-05-29 19:51 ` [PATCH v2 3/7] dm: fix test for DAX device support Ross Zwisler
2018-06-01 20:19   ` Mike Snitzer
2018-06-01 20:46     ` Mike Snitzer
2018-06-01 21:11       ` Ross Zwisler
2018-06-01 21:16       ` Dan Williams
2018-05-29 19:51 ` [PATCH v2 4/7] dm: prevent DAX mounts if not supported Ross Zwisler
2018-06-01 21:55   ` Mike Snitzer
2018-06-04 23:15     ` Ross Zwisler
2018-06-20 15:17       ` Mike Snitzer
2018-06-25 19:20         ` Ross Zwisler
2018-05-29 19:51 ` [PATCH v2 5/7] dm: remove DM_TYPE_DAX_BIO_BASED dm_queue_mode Ross Zwisler
2018-06-01 22:04   ` Mike Snitzer
2018-06-04 23:24     ` Ross Zwisler
2018-06-04 23:49       ` Kani, Toshi
2018-06-05  0:46       ` Mike Snitzer
2018-06-06 17:24         ` Ross Zwisler
2018-06-06 22:29           ` Mike Snitzer
2018-05-29 19:51 ` [PATCH v2 6/7] dm-snap: remove unnecessary direct_access() stub Ross Zwisler
2018-05-29 19:51 ` [PATCH v2 7/7] dm-error: " Ross Zwisler

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