From: Willem de Bruijn Date: Thu, 13 Jun 2013 19:29:38 +0000 (-0400) Subject: net-rps: fixes for rps flow limit X-Git-Tag: v3.11-rc1~16^2~87 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5f121b9a83b499a61ed44e5ba619c7de8f7271ad;p=pandora-kernel.git net-rps: fixes for rps flow limit Caught by sparse: - __rcu: missing annotation to sd->flow_limit - __user: direct access in cpumask_scnprintf Also - add endline character when printing bitmap if room in buffer - avoid bucket overflow by reducing FLOW_LIMIT_HISTORY The last item warrants some explanation. The hashtable buckets are subject to overflow if FLOW_LIMIT_HISTORY is larger than or equal to bucket size, since all packets may end up in a single bucket. The current (rather arbitrary) history value of 256 happens to match the buffer size (u8). As a result, with a single flow, the first 128 packets are accepted (correct), the second 128 packets dropped (correct) and then the history[] array has filled, so that each subsequent new packet causes an increment in the bucket for new_flow plus a decrement for old_flow: a steady state. This is fine if packets are dropped, as the steady state goes away as soon as a mix of traffic reappears. But, because the 256th packet overflowed the bucket to 0: no packets are dropped. Instead of explicitly adding an overflow check, this patch changes FLOW_LIMIT_HISTORY to never be able to overflow a single bucket. Reported-by: Fengguang Wu (first item) Signed-off-by: Willem de Bruijn Signed-off-by: David S. Miller --- Reading git-diff-tree failed