[PATCH v2] net: mvneta: fix refilling for Rx DMA buffers

[Oren Laskin]

I would hit this error on my Armada 370 board about 20% of the time
after downloading a 30MB file to /tmp.  We're running a 1 Gb SGMII
link.  I would hit this in less than a minute before removing this
commit from my tree.  I've now been running this test in a loop for a
few hours with no problems.

It was somewhat hard to diagnose since files I used scp didn't see the
issues (or at least as quickly).  I set up an http program to serve a
file and replicated the problem with wget and found it.

Oren

On Mon, Sep 14, 2015 at 3:13 PM, Simon Guinot <simon.guinot at sequanux.org> wrote:
> Hi Oren,
>
> On Mon, Sep 14, 2015 at 01:22:12PM -0700, Oren Laskin wrote:
>> I had to undo this change on my Amada 370 based board.  It was causing
>> corrupt data to make it through on large downloads.  I'm using wget to get
>> the same 30MB file many times and the SHA would occasionally be different.
>
> During your tests, can you see some "Linux processing - Can't refill"
> messages along with the data corruptions ?
>
>> I tracked it down to this commit.  In it, I would find on the order of a
>> few hundred bytes to simply be wrong data.
>
> I am little bit surprised here. For me, this patch is very simple and
> does the exact opposite. It does fix kernel crashes and data corruptions
> in case of refilling errors. This can happen for example if you run
> large data transfers with jumbo frames enabled...
>
> But anyway, I'll try to reproduce the issue tomorrow. I only have to
> wget the same file (size 30MB) in a loop and to check its md5sum ?
> That's it ? And how long should I wait for the error ?
>
> Thanks,
>
> Simon
>
>>
>> Thanks,
>>
>> Oren
>>
>> On Tue, Jul 21, 2015 at 12:30 AM, David Miller <davem at davemloft.net> wrote:
>>
>> > From: Simon Guinot <simon.guinot at sequanux.org>
>> > Date: Sun, 19 Jul 2015 13:00:53 +0200
>> >
>> > > With the actual code, if a memory allocation error happens while
>> > > refilling a Rx descriptor, then the original Rx buffer is both passed
>> > > to the networking stack (in a SKB) and let in the Rx ring. This leads
>> > > to various kernel oops and crashes.
>> > >
>> > > As a fix, this patch moves Rx descriptor refilling ahead of building
>> > > SKB with the associated Rx buffer. In case of a memory allocation
>> > > failure, data is dropped and the original DMA buffer is put back into
>> > > the Rx ring.
>> > >
>> > > Signed-off-by: Simon Guinot <simon.guinot at sequanux.org>
>> > > Fixes: c5aff18204da ("net: mvneta: driver for Marvell Armada 370/XP
>> > network unit")
>> > > Cc: <stable at vger.kernel.org> # v3.8+
>> > > Tested-by: Yoann Sculo <yoann at sculo.fr>
>> >
>> > Applied, thanks.
>> >
>> > _______________________________________________
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>> > linux-arm-kernel at lists.infradead.org
>> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>> >