netdev - Re: [PATCHv2] 3c59x: fix missing dma_mapping_error check and bad ring refill logic

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Message-Id: <20180103.095849.985156664792555290.davem@davemloft.net>
Date:   Wed, 03 Jan 2018 09:58:49 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     nhorman@...driver.com
Cc:     netdev@...r.kernel.org, tedheadster@...il.com, nhorman@...hat.com,
        klassert@...hematik.tu-chemnitz.de
Subject: Re: [PATCHv2] 3c59x: fix missing dma_mapping_error check and bad
 ring refill logic

From: Neil Horman <nhorman@...driver.com>
Date: Wed,  3 Jan 2018 09:44:15 -0500

> A few spots in 3c59x missed calls to dma_mapping_error checks, casuing
> WARN_ONS to trigger.  Clean those up.  While we're at it, refactor the
> refill code a bit so that if skb allocation or dma mapping fails, we
> recycle the existing buffer.  This prevents holes in the rx ring, and
> makes for much simpler logic
> 
> Note: This is compile only tested.  Ted, if you could run this and
> confirm that it continues to work properly, I would appreciate it, as I
> currently don't have access to this hardware
> 
> Signed-off-by: Neil Horman <nhorman@...hat.com>
> CC: Steffen Klassert <klassert@...hematik.tu-chemnitz.de>
> CC: "David S. Miller" <davem@...emloft.net>
> Reported-by: tedheadster@...il.com

See my other reply.

Your RX handling must become more sophisticated.

This is exactly what we tell driver authors to do.  If you cannot allocate
or DMA map a replacement RX buffer, you _MUST_ recycle the existing buffer
back to the chip rather than pass it up to the stack.

Thank you.