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Date: Thu, 13 Oct 2016 07:59:01 +1100
From: Dave Chinner <david@fromorbit.com>
To: CAI Qian <caiqian@redhat.com>
Cc: Sage Weil <sage@redhat.com>, Brian Foster <bfoster@redhat.com>,
        Jan Kara <jack@suse.cz>, Miklos Szeredi <miklos@szeredi.hu>,
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Subject: Re: [bisected] Re: local DoS - systemd hang or timeout (WAS: Re:
 [RFC][CFT] splice_read reworked)
Message-ID: <20161012205901.GF27872@dastard>
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On Wed, Oct 12, 2016 at 03:50:36PM -0400, CAI Qian wrote:
> 
> 
> ----- Original Message -----
> > From: "Dave Chinner" <david@fromorbit.com>
> > Sent: Monday, October 10, 2016 5:57:14 PM
> > 
> > > http://people.redhat.com/qcai/tmp/dmesg
> > 
> > It's a page lock order bug in the XFS seek hole/data implementation.
> So reverted this commit against the latest mainline allows trinity run
> hours. Otherwise, it always hang at fdatasync() within 30 minutes.
> 
> fc0561cefc04e7803c0f6501ca4f310a502f65b8
> xfs: optimise away log forces on timestamp updates for fdatasync

Has nothing at all to do with the hang.

> PS: tested against the vfs tree's #work.splice_read with this commit
> reverted is now hanging at sync() instead which won't be  reproduced
> against the mainline so far.
> http://people.redhat.com/qcai/tmp/dmesg-sync

It is the same page lock vs seek hole/data issue.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com