Re: iov_iter_pipe warning.

From	Dave Chinner <david@fromorbit.com>
Newsgroups	linux.kernel
Subject	Re: iov_iter_pipe warning.
Date	2017-09-07 01:50 +0200
Message-ID	<umSeZ-dZ-5@gated-at.bofh.it> (permalink)
References	(5 earlier) <tBhSp-272-3@gated-at.bofh.it> <ubWFk-5gn-25@gated-at.bofh.it> <ujyZc-1HG-37@gated-at.bofh.it> <ujGk1-6l8-1@gated-at.bofh.it> <umOO5-6BS-3@gated-at.bofh.it>
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On Wed, Sep 06, 2017 at 04:03:37PM -0400, Dave Jones wrote:
> On Mon, Aug 28, 2017 at 09:25:42PM -0700, Darrick J. Wong wrote:
>  > On Mon, Aug 28, 2017 at 04:31:30PM -0400, Dave Jones wrote:
>  > > I'm still trying to narrow down an exact reproducer, but it seems having
>  > > trinity do a combination of sendfile & writev, with pipes and regular
>  > > files as fd's is the best repro.
>  > > 
>  > > Is this a real problem, or am I chasing ghosts ?  That it doesn't happen
>  > > on ext4 or btrfs is making me wonder...
>  > 
>  > <shrug> I haven't heard of any problems w/ directio xfs lately, but OTOH
>  > I think it's the only filesystem that uses iomap_dio_rw, which would
>  > explain why ext4/btrfs don't have this problem.
> 
> Another warning, from likely the same root cause.
> 
> WARNING: CPU: 3 PID: 572 at lib/iov_iter.c:962 iov_iter_pipe+0xe2/0xf0

	WARN_ON(pipe->nrbufs == pipe->buffers);

 *      @nrbufs: the number of non-empty pipe buffers in this pipe
 *      @buffers: total number of buffers (should be a power of 2)

So that's warning that the pipe buffer is already full before we
try to read from the filesystem?

That doesn't seem like an XFS problem - it indicates the pipe we are
filling in generic_file_splice_read() is not being emptied by
whatever we are splicing the file data to....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Thread

Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-08-28 22:40 +0200
  Re: iov_iter_pipe warning. "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-29 06:30 +0200
    Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-08-30 19:10 +0200
      Re: iov_iter_pipe warning. "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-30 19:20 +0200
        Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-08-30 19:20 +0200
    Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-09-06 22:10 +0200
      Re: iov_iter_pipe warning. Dave Chinner <david@fromorbit.com> - 2017-09-07 01:50 +0200
        Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-09-07 05:50 +0200
          Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-07 06:40 +0200
        Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-08 03:10 +0200
          Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-09-10 03:10 +0200
            Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-09-10 05:00 +0200

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