linux-kernel - Re: [PATCH] 9p: trans_fd, initialize recv fcall properly if not set

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Message-ID: <CAFkjPT=1TAq5S_TBgKa_UyGs2CfhDKOWEqc9HyhKHw89vO_ZOQ@mail.gmail.com>
Date:	Sat, 5 Sep 2015 22:15:06 -0500
From:	Eric Van Hensbergen <ericvh@...il.com>
To:	Dominique Martinet <dominique.martinet@....fr>
Cc:	V9FS Developers <v9fs-developer@...ts.sourceforge.net>,
	Ron Minnich <rminnich@...dia.gov>,
	Latchesar Ionkov <lucho@...kov.net>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: Re: [PATCH] 9p: trans_fd, initialize recv fcall properly if not set

On Thu, Sep 3, 2015 at 4:38 AM, Dominique Martinet
<dominique.martinet@....fr> wrote:
> That code really should never be called (rc is allocated in
> tag_alloc), but if it had been it couldn't have worked...
>
> Signed-off-by: Dominique Martinet <dominique.martinet@....fr>
> ---
>  net/9p/trans_fd.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> To be honest, I think it might be better to just bail out if we get in
> this switch (m->req->rc == NULL after p9_tag_lookup) and not try to
> allocate more, because if we get there it's likely a race condition and
> silently re-allocating will end up in more troubles than trying to
> recover is worth.
> Thoughts ?
>

Hmmm...trying to rattle my brain and remember why I put it in there
back in 2008.
It might have just been over-defensive programming -- or more likely it just
pre-dated all the zero copy infrastructure which pretty much guaranteed we had
an rc allocated and what is there is vestigial.  I'm happy to accept a
patch which
makes this an assert, or perhaps just resets the connection because something
has gone horribly wrong (similar to the ENOMEM path that is there now).

        -eric
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