linux-kernel - Re: LTP rwtest01 blocks on DAX mountpoint

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Date:   Mon, 2 Jan 2017 14:49:41 -0700
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Xiong Zhou <xzhou@...hat.com>, linux-fsdevel@...r.kernel.org,
        linux-nvdimm@...1.01.org, linux-kernel@...r.kernel.org
Subject: Re: LTP rwtest01 blocks on DAX mountpoint

On Mon, Jan 02, 2017 at 06:16:17PM +0100, Jan Kara wrote:
> On Fri 30-12-16 17:33:53, Xiong Zhou wrote:
> > On Sat, Dec 24, 2016 at 07:07:14PM +0800, Xiong Zhou wrote:
> > > Hi lists,
> > > 
> > > Since around 20161129 tag, LTP rwtest01 on dax mountpoint blocks
> > > on linux-next tree, now on Linus tree.
> > > 
> > > In "normal", rwtest01 subcase ends in a few minutes, now it keeps
> > > running for hours on dax mountpoint, both ext4 and xfs. Ctrl + c
> > > can interrupt it.
> > 
> > Test programme is waiting for a memcpy call to return.
> > 
> > From sysrq output, kernel code is not blocking on somewhere,
> > it just wont return.
> 
> I was trying to reproduce this but for me rwtest01 completes just fine on
> dax mountpoint (I've used your reproducer). So can you sample several
> kernel stack traces to get a rough idea where the kernel is running?
> Thanks!
> 
> 								Honza

I'm also unable to reproduce this issue.  I've tried with both the blamed
commit:

4b4bb46 (HEAD) dax: clear dirty entry tags on cache flush

and with v4.9-rc2.  Both pass the test in my setup.

Perhaps the variable is the size of your PMEM partitions?

# fdisk -l /dev/pmem0
Disk /dev/pmem0: 16 GiB, 17179869184 bytes, 33554432 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xfe50c900

Device       Boot    Start      End  Sectors Size Id Type
/dev/pmem0p1          4096 25165823 25161728  12G 83 Linux
/dev/pmem0p2      25165824 33550335  8384512   4G 83 Linux

What does your setup look like?

I'm using the current tip of the LTP tree:

8cc4165  waitid02: define _XOPEN_SOURCE 500

Thanks,
- Ross