From: Jan Kara <jack@suse.cz>
To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>,
linux-ext4@vger.kernel.org, Jan Kara <jack@suse.cz>,
"Theodore Ts'o" <tytso@mit.edu>,
Dan Williams <dan.j.williams@intel.com>,
Yumei Huang <yuhuang@redhat.com>, KVM <kvm@vger.kernel.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux ACPI <linux-acpi@vger.kernel.org>,
Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: DAX can not work on virtual nvdimm device
Date: Tue, 6 Sep 2016 17:06:20 +0200 [thread overview]
Message-ID: <20160906150620.GJ28922@quack2.suse.cz> (raw)
In-Reply-To: <20160902025738.GA26108@linux.intel.com>
On Thu 01-09-16 20:57:38, Ross Zwisler wrote:
> On Wed, Aug 31, 2016 at 04:44:47PM +0800, Xiao Guangrong wrote:
> > On 08/31/2016 01:09 AM, Dan Williams wrote:
> > >
> > > Can you post your exact reproduction steps? This test is not failing for me.
> > >
> >
> > Sure.
> >
> > 1. make the guest kernel based on your tree, the top commit is
> > 10d7902fa0e82b (dax: unmap/truncate on device shutdown) and
> > the config file can be found in this thread.
> >
> > 2. add guest kernel command line: memmap=6G!10G
> >
> > 3: start the guest:
> > x86_64-softmmu/qemu-system-x86_64 -machine pc,nvdimm --enable-kvm \
> > -smp 16 -m 32G,maxmem=100G,slots=100 /other/VMs/centos6.img -monitor stdio
> >
> > 4: in guest:
> > mkfs.ext4 /dev/pmem0
> > mount -o dax /dev/pmem0 /mnt/pmem/
> > echo > /mnt/pmem/xxx
> > ./mmap /mnt/pmem/xxx
> > ./read /mnt/pmem/xxx
> >
> > The source code of mmap and read has been attached in this mail.
> >
> > Hopefully, you can detect the error triggered by read test.
> >
> > Thanks!
>
> Okay, I think I've isolated this issue. Xiao's VM was an old CentOS 6 system,
> and for some reason ext4+DAX with the old tools found in that VM fails. I was
> able to reproduce this failure with a freshly installed CentOS 6.8 VM.
>
> You can see the failure with his tests, or perhaps more easily with this
> series of commands:
>
> # mkfs.ext4 /dev/pmem0
> # mount -o dax /dev/pmem0 /mnt/pmem/
> # touch /mnt/pmem/x
> # md5sum /mnt/pmem/x
> md5sum: /mnt/pmem/x: Bad address
>
> This sequence of commands works fine in the old CentOS 6 system if you use XFS
> instead of ext4, and it works fine with both ext4 and XFS in CentOS 7 and
> with recent versions of Fedora.
>
> I've added the ext4 folks to this mail in case they care, but my guess is that
> the tools in CentOS 6 are so old that it's not worth worrying about. For
> reference, the kernel in CentOS 6 is based on 2.6.32. :) DAX was introduced
> in v4.0.
Hum, can you post 'dumpe2fs -h /dev/pmem0' output from that system when the
md5sum fails? Because the only idea I have is that mkfs.ext4 in CentOS 6
creates the filesystem with a different set of features than more recent
e2fsprogs and so we hit some untested path...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2016-09-06 15:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-19 11:19 DAX can not work on virtual nvdimm device Xiao Guangrong
2016-08-19 14:59 ` Dan Williams
2016-08-19 18:30 ` Ross Zwisler
2016-08-21 9:55 ` Boaz Harrosh
2016-08-29 7:54 ` Xiao Guangrong
2016-08-29 19:30 ` Ross Zwisler
2016-08-30 6:53 ` Xiao Guangrong
2016-08-30 17:09 ` Dan Williams
2016-08-31 8:44 ` Xiao Guangrong
2016-08-31 16:46 ` Ross Zwisler
2016-09-02 2:57 ` Ross Zwisler
2016-09-06 15:06 ` Jan Kara [this message]
2016-09-08 20:47 ` Ross Zwisler
2016-09-09 9:19 ` Jan Kara
2016-09-09 14:03 ` Theodore Ts'o
2016-09-09 16:34 ` Ross Zwisler
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