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Re: iov_iter_pipe warning.

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On Mon, Apr 10, 2017 at 08:57:11PM +0100, Al Viro wrote:
 > On Mon, Apr 10, 2017 at 03:42:06PM -0400, Dave Jones wrote:
 > >  > Do you have a reliable reproducer?
 > > 
 > > Not reliable, but I'll see if I can find some time to narrow it down
 > > this week.  I've been working on better logging of "wtf just happened"
 > > the last few weeks, so it should get easier once I finish that work.
 > 
 > I would suggest
 > 	a) slapping WARN_ON(pipe->nr_bufs); right before the loop
 > in splice_direct_to_actor().  Internal pipe should be empty when we
 > enter this function.
 > 	b) the same WARN_ON() in the very end of the loop body.
 > 
 > We should have started with empty pipe.  We'd called ->splice_read()
 > and it had returned a positive number (in read_len).  That should be
 > the amount we'd pushed in there.  Then we call actor(), with
 > sd->total_len set to read_len.  Its return value is
 > 	* positive (or we would've buggered off)
 > 	* no less than read_len (ditto)
 > so it should have drained the pipe entirely, leaving it empty again.
 > 
 > Finding it not just non-empty, but full means that something's very
 > wrong.  The actor here is essentially ->splice_write(), and I'm really
 > curious which file is the target.  Actually, could you turn those
 > WARN_ON() into
 > 	if (WARN_ON(pipe->nr_bufs))
 > 		printk(KERN_ERR "->splice_write = %p",
 > 			sd->u.file->f_op->splice_write);
 > and see which function it is?

s/nr_bufs/nrbufs/ aside, I tried this, and it didn't trigger, even
though I hit the iov_iter_pipe WARN again.

	Dave

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Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-10 21:30 +0200
  Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-10 21:50 +0200
    Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-10 22:00 +0200
      Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-11 01:50 +0200
        Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-11 02:30 +0200
          Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-11 05:10 +0200
            Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-11 05:30 +0200
              Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-11 23:00 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-11 23:20 +0200
                Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-12 00:30 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-12 01:30 +0200
                Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-12 01:40 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-12 01:50 +0200
                Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-12 01:50 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-12 02:00 +0200
                Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-12 02:10 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-12 02:20 +0200
                Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-12 03:00 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-12 03:20 +0200
                Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-12 04:30 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-12 05:00 +0200
                Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-12 16:40 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-12 17:30 +0200
                Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-12 18:30 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-12 19:10 +0200
                Re: iov_iter_pipe warning. Dave Jones <davej@codemonkey.org.uk> - 2017-04-12 21:10 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-21 21:10 +0200
                Re: iov_iter_pipe warning. Al Viro <viro@ZenIV.linux.org.uk> - 2017-04-12 02:00 +0200

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