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Re: [Xen-devel] [PATCH net] xen-netback: Fix slot estimation

On 05/06/14 23:02, David Miller wrote:
From: Zoltan Kiss<zoltan.kiss@xxxxxxxxxx>
Date: Tue, 3 Jun 2014 14:32:16 +0100

A recent commit (a02eb4 "xen-netback: worse-case estimate in xenvif_rx_action is
underestimating") capped the slot estimation to MAX_SKB_FRAGS, but that triggers
the next BUG_ON a few lines down, as the packet consumes more slots than
This patch remove that cap, and if the frontend doesn't provide enough slot,
put back the skb to the top of the queue and caps rx_last_skb_slots. When the
next try also fails, it drops the packet.
Capping rx_last_skb_slots is needed because if the frontend never gives enough
slots, the ring gets stalled.

Signed-off-by: Zoltan Kiss<zoltan.kiss@xxxxxxxxxx>
Like David Laight, I do not like this patch at all.

Yes a crash or BUG_ON triggered is bad, but fixing it by deadlocking
TCP connections (a silent failure) is not an improvement.

I'm not applying this, sorry.


I haven't wrote it explicitly, but my other patch "xen-netback: Fix handling of skbs requiring too many slots" supersedes this one.

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