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From: Yonghyeon PYUN <pyunyh@gmail.com>
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Date: Mon, 27 Jul 2015 21:58:51 +0900
To: Hans Petter Selasky <hps@selasky.org>
Cc: FreeBSD Current <freebsd-current@freebsd.org>,
 Sean Bruno <sbruno@freebsd.org>
Subject: Re: E1000 mbuf leaks
Message-ID: <20150727125850.GA986@michelle.fasterthan.com>
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On Mon, Jul 27, 2015 at 01:02:32PM +0200, Hans Petter Selasky wrote:
> Hi,
> 
> I'm currently doing some busdma work, and possibly stepped over some 
> driver bugs. When "bus_dmamap_load_mbuf_sg()" returns ENOMEM the mbuf 
> chain is not freed. Is there some magic in "bus_dmamap_load_mbuf_sg()" 
> for that error code or is there a possible memory leak in all E1000 
> drivers? See attached patch.

I don't think it's an mbuf leak since lem(4) just prepend the mbuf
to the if sendq(driver will retry it later).  But I think your
patch looks more correct in bus_dma(9) perspective.  If
bus_dmamap_load_mbuf_sg(9) returned an error except EFBIG, it would
be correct for lem(4) to free the mbuf chains rather than
restarting the bus_dmamap_load_mbuf_sg(9) later which shall fail
again with ENOMEM.