linux-kernel - LTP rwtest01 blocks on DAX mountpoint

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Date:   Sat, 24 Dec 2016 19:07:14 +0800
From:   Xiong Zhou <xzhou@...hat.com>
To:     jack@...e.cz, linux-nvdimm@...1.01.org,
        linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: LTP rwtest01 blocks on DAX mountpoint

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.

It is always reproducible, blocking following tests.

It does not happen when mounting without dax option.
It does not happen on v4.9.

Bisect point to:

commit 4b4bb46d00b386e1c972890dc5785a7966eaa9c0
Author: Jan Kara <jack@...e.cz>
Date:   Wed Dec 14 15:07:53 2016 -0800

    dax: clear dirty entry tags on cache flush

Reverting this commit on top of Linus tree "fixes" this issue.

Reproducer:

sh-4.2# cat rwt
rwtest01 export LTPROOT; rwtest -N rwtest01 -c -q -i 60s  -f sync 10%25000:$TMPDIR/rw-sync-$$
sh-4.2# 
mkfs.xfs /dev/pmem0p1
mount -o dax /dev/pmem0p1 /daxmnt && \
/opt/ltp/runltp -q -d /daxmnt -f rwt -p -b /dev/pmem0p2 -B xfs
umount /daxmnt

Bisect log is attached.

Thanks,
Xiong

View attachment "bisect2" of type "text/plain" (2815 bytes)