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Date:   Sat, 14 Nov 2020 07:00:25 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Nathan Chancellor <natechancellor@gmail.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Christoph Hellwig <hch@lst.de>,
        Greg KH <gregkh@linuxfoundation.org>,
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        wei.liu@kernel.org, linux-hyperv@vger.kernel.org
Subject: Re: [PATCH 1/6] seq_file: add seq_read_iter
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On Fri, Nov 13, 2020 at 11:19:34PM -0700, Nathan Chancellor wrote:

> Assuming so, I have attached the output both with and without the
> WARN_ON. Looks like mountinfo is what is causing the error?

Cute...  FWIW, on #origin + that commit with fix folded in I don't
see anything unusual in reads from mountinfo ;-/  OTOH, they'd
obviously been... creative with readv(2) arguments, so it would
be very interesting to see what it is they are passing to it.

I'm half-asleep right now; will try to cook something to gather
that information tomorrow morning.  'Later...