linux-kernel - Re: [PATCH net-next] rxrpc: Make service connection lookup always check for retry

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Date:   Tue, 05 Sep 2017 14:41:53 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dhowells@...hat.com
Cc:     netdev@...r.kernel.org, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] rxrpc: Make service connection lookup always
 check for retry

From: David Howells <dhowells@...hat.com>
Date: Mon, 04 Sep 2017 15:28:28 +0100

> When an RxRPC service packet comes in, the target connection is looked up
> by an rb-tree search under RCU and a read-locked seqlock; the seqlock retry
> check is, however, currently skipped if we got a match, but probably
> shouldn't be in case the connection we found gets replaced whilst we're
> doing a search.
> 
> Make the lookup procedure always go through need_seqretry(), even if the
> lookup was successful.  This makes sure we always pick up on a write-lock
> event.
> 
> On the other hand, since we don't take a ref on the object, but rely on RCU
> to prevent its destruction after dropping the seqlock, I'm not sure this is
> necessary.
> 
> Signed-off-by: David Howells <dhowells@...hat.com>

Applied, thanks David.