Date: Fri, 28 Apr 2017 17:43:13 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dave Jones <davej@codemonkey.org.uk>,
        Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: iov_iter_pipe warning.
Message-ID: <20170428164313.GK29622@ZenIV.linux.org.uk>
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 <20170412152600.GP29622@ZenIV.linux.org.uk>
 <20170412162709.bn5qfk4seues3yos@codemonkey.org.uk>
 <20170412170723.GQ29622@ZenIV.linux.org.uk>
 <20170412190318.srkkdytf2ebrjzrg@codemonkey.org.uk>
 <20170421175430.GT29622@ZenIV.linux.org.uk>
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On Fri, Apr 28, 2017 at 11:29:55AM -0400, Dave Jones wrote:
> On Fri, Apr 21, 2017 at 06:54:30PM +0100, Al Viro wrote:
>  > On Wed, Apr 12, 2017 at 03:03:18PM -0400, Dave Jones wrote:
>  > 
>  > > Well it's been running an hour without incident, which looks promising.
>  > > I'll leave it run, but I'd say you're on the right track given how quick
>  > > it reproduced so far.
>  > 
>  > Could you try this and see if it works?  What happens is that unlike
>  > e.g. generic_file_read_iter/generic_file_write_iter, NFS O_DIRECT handling
>  > does not make sure that iov_iter had been advanced by the amount
>  > actually transferred - it is left advanced by the amount *requested*.
> 
> Crap. So I never ran it long enough it seems. I can still hit that trace.
> I re-added one of your earlier debug patches, and got this..

Could you send me the diff against something from mainline (identified by
sha1, ideally)?