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

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Date:   Wed, 03 Jan 2018 10:26:06 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     nhorman@...hat.com
Cc:     nhorman@...driver.com, netdev@...r.kernel.org,
        tedheadster@...il.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@...hat.com>
Date: Wed, 3 Jan 2018 10:13:33 -0500

> Thats exactly what this patch does, instead of creating a second loop to
> traverse all the emptied ring buffers, now I:
> 
> 1) Pre-allocate a new skb when I know I'm going to receive the in-place skb
> 2) Map the skb into the appropriate dma device domain
> 3) If (1) and (2) succede, then I swap the newly allocate skb and dma address
> with the old one and recieve the old into the network stack
> 4) If (1) or (2) fail, then I goto clear_complete, which leaves the old skb and
> dma address in place, sets the buffer status back to 0 (indicating completion),
> and write the new ring status back to the hardware
> 
> This is what you wanted, a pre-allocate and swap-if-successful, recycle-if-not
> approach, rather than the leave-a-hole-in-the-ring approach that is there
> currently, no?  Or did I miss something else?

I misread the code sorry, you're absolutely right.

I'll apply this patch, thanks Neil. :)