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Date: Sat, 21 Dec 2013 20:56:28 -0700
From: Jens Axboe <axboe@kernel.dk>
To: Dave Chinner <david@fromorbit.com>
Cc: Ming Lei <tom.leiming@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [HANG 3.13-rc3] blk-mq/virtio: mkfs.ext4 hangs in
 blk_mq_wait_for_tags
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On Fri, Dec 13 2013, Dave Chinner wrote:
> On Fri, Dec 13, 2013 at 09:57:48AM +0800, Ming Lei wrote:
> > On Tue, Dec 10, 2013 at 6:39 AM, Dave Chinner <david@fromorbit.com> wrote:
> > > Hi Jens,
> > >
> > > Another day, another blkmq/virtio problem. Running mkfs.ext4 on a
> > > sparse 100TB VM file image, it hangs hard while writing superblock
> > > information:
> > >
> > > $ tests/fsmark-50-test-ext4.sh
> > > mke2fs 1.43-WIP (20-Jun-2013)
> > > Filesystem label=
> > > OS type: Linux
> > > Block size=4096 (log=2)
> > > Fragment size=4096 (log=2)
> > > Stride=0 blocks, Stripe width=0 blocks
> > > 1677721600 inodes, 26843545600 blocks
> > > 1342177280 blocks (5.00%) reserved for the super user
> > > First data block=0
> > > 819200 block groups
> > > 32768 blocks per group, 32768 fragments per group
> > > 2048 inodes per group
> > > Superblock backups stored on blocks:
> > >         32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
> > >         4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
> > >         102400000, 214990848, 512000000, 550731776, 644972544, 1934917632,
> > >         2560000000, 3855122432, 5804752896, 12800000000, 17414258688
> > >
> > > Allocating group tables: done
> > > Writing inode tables: done
> > > Creating journal (32768 blocks): done
> > > Writing superblocks and filesystem accounting information:
> > >
> > > It writes a few superblocks, then hangs. Immediately after it stops
> > > updating that last line, I see this:
> > >
> > > root@test4:~# echo w > /proc/sysrq-trigger
> > 
> > It might be helpful to do below and post the result before the sysrq-trigger:
> > 
> >          cat    /sys/class/block/vda/mq/0/tags
> 
> I would, but for some reason I can't reproduce it now. I'm running a
> slightly more recent kernel than a few days ago, and it isn't
> hanging now....

Dave, I haven't found anything through testing. Is that the case at your
end too?

-- 
Jens Axboe