tree a28503490179133baff9275d428a3c0c31f35e4e
parent e2307ed6cbe71c74e291681aaa7e92ab98bc3177
author Thomas Graf <tgraf@suug.ch> 1429688506 +0200
committer David S. Miller <davem@davemloft.net> 1429726642 -0400

rhashtable: Do not schedule more than one rehash if we can't grow further

The current code currently only stops inserting rehashes into the
chain when no resizes are currently scheduled. As long as resizes
are scheduled and while inserting above the utilization watermark,
more and more rehashes will be scheduled.

This lead to a perfect DoS storm with thousands of rehashes
scheduled which lead to thousands of spinlocks to be taken
sequentially.

Instead, only allow either a series of resizes or a single rehash.
Drop any further rehashes and return -EBUSY.

Fixes: ccd57b1bd324 ("rhashtable: Add immediate rehash during insertion")
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>