[Ocfs2-devel] [patch 03/11] ocfs2/o2net: incorrect to terminate accepting connections loop upon rejecting an invalid one

[Tariq Saeed <tariq.x.saeed@oracle.com>]

On 03/19/2014 02:01 PM, Andrew Morton wrote:
> On Fri, 24 Jan 2014 14:22:57 -0800 tariq saeed <tariq.x.saeed@oracle.com> wrote:
>
>> On 1/24/2014 1:55 PM, Mark Fasheh wrote:
>>> On Fri, Jan 24, 2014 at 12:47:02PM -0800, akpm at linux-foundation.org wrote:
>>>> From: Tariq Saeed <tariq.x.saeed@oracle.com>
>>>> Subject: ocfs2/o2net: incorrect to terminate accepting connections loop upon rejecting an invalid one
>>>>
>>>> When o2net-accept-one() rejects an illegal connection, it terminates the
>>>> loop picking up the remaining queued connections.  This fix will continue
>>>> accepting connections till the queue is emtpy.
>>>>
>>>> Addresses Orabug 17489469.
>>> Thanks for sending this, review comments below.
>>>
>>>
>>>> diff -puN fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one fs/ocfs2/cluster/tcp.c
>>>> --- a/fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one
>>>> +++ a/fs/ocfs2/cluster/tcp.c
>>>> @@ -1826,7 +1826,7 @@ int o2net_register_hb_callbacks(void)
>>>>
>>>>    /* ------------------------------------------------------------ */
>>>>
>>>> -static int o2net_accept_one(struct socket *sock)
>>>> +static int o2net_accept_one(struct socket *sock, int *more)
>>>>    {
>>>>    	int ret, slen;
>>>>    	struct sockaddr_in sin;
>>>> @@ -1837,6 +1837,7 @@ static int o2net_accept_one(struct socke
>>>>    	struct o2net_node *nn;
>>>>
>>>>    	BUG_ON(sock == NULL);
>>>> +	*more = 0;
>>>>    	ret = sock_create_lite(sock->sk->sk_family, sock->sk->sk_type,
>>>>    			       sock->sk->sk_protocol, &new_sock);
>>>>    	if (ret)
>>>> @@ -1848,6 +1849,7 @@ static int o2net_accept_one(struct socke
>>>>    	if (ret < 0)
>>>>    		goto out;
>>>>
>>>> +	*more = 1;
>>>>    	new_sock->sk->sk_allocation = GFP_ATOMIC;
>>>>
>>>>    	ret = o2net_set_nodelay(new_sock);
>>>> @@ -1949,8 +1951,15 @@ out:
>>>>    static void o2net_accept_many(struct work_struct *work)
>>>>    {
>>>>    	struct socket *sock = o2net_listen_sock;
>>>> -	while (o2net_accept_one(sock) == 0)
>>>> +	int	more;
>>>> +	int	err;
>>>> +
>>>> +	for (;;) {
>>>> +		err = o2net_accept_one(sock, &more);
>>>> +		if (!more)
>>>> +			break;
>>> We're throwing out 'err' here and trusting the variable 'more'. However, err
>>> could be set and more would be 0 regardless of whether there actually are
>>> more connections to be had. This makes more sense given when 'more' is set:
>>
>> Thanks for the comments.
>> To understand the consequences of ignoring the err, we need to look at
>> what is going on.
>> We get a softIRQ when a connection packet (tcp SYN). It is critical to
>> note that we may not
>> get a softIRQ_for every connection s_ince connection packets can arrive
>> back-to-back (as happened in this bug). So, one softIRQ could be
>> delivered for > 1 pending accept.
>> _This is the KEY point. _
>>
>> If we terminate the loop calling o2net_accept_one() upon seeing an
>> error, what happens
>> to the rest of the connections in the queue. If no new connection
>> arrives for hours, no new softIRQ
>> will be delivered, and the connections will just sit in the queue.
>
> Please note that I had to edit your email to undo the top-posting so I
> could reply to it.  Please don't top-post.
>
> Mark, are you now OK with the patch as-is?
Mark, do you have further questios?
>
>
> From: Tariq Saeed <tariq.x.saeed@oracle.com>
> Subject: ocfs2/o2net: incorrect to terminate accepting connections loop upon rejecting an invalid one
>
> When o2net-accept-one() rejects an illegal connection, it terminates the
> loop picking up the remaining queued connections.  This fix will continue
> accepting connections till the queue is emtpy.
>
> Addresses Orabug 17489469.
>
> Signed-off-by: Tariq Saseed <tariq.x.saeed@oracle.com>
> Cc: Mark Fasheh <mfasheh@suse.com>
> Cc: Joel Becker <jlbec@evilplan.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
>   fs/ocfs2/cluster/tcp.c |   13 +++++++++++--
>   1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff -puN fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one fs/ocfs2/cluster/tcp.c
> --- a/fs/ocfs2/cluster/tcp.c~ocfs2-o2net-incorrect-to-terminate-accepting-connections-loop-upon-rejecting-an-invalid-one
> +++ a/fs/ocfs2/cluster/tcp.c
> @@ -1826,7 +1826,7 @@ int o2net_register_hb_callbacks(void)
>
>   /* ------------------------------------------------------------ */
>
> -static int o2net_accept_one(struct socket *sock)
> +static int o2net_accept_one(struct socket *sock, int *more)
>   {
>   	int ret, slen;
>   	struct sockaddr_in sin;
> @@ -1837,6 +1837,7 @@ static int o2net_accept_one(struct socke
>   	struct o2net_node *nn;
>
>   	BUG_ON(sock == NULL);
> +	*more = 0;
>   	ret = sock_create_lite(sock->sk->sk_family, sock->sk->sk_type,
>   			       sock->sk->sk_protocol, &new_sock);
>   	if (ret)
> @@ -1848,6 +1849,7 @@ static int o2net_accept_one(struct socke
>   	if (ret < 0)
>   		goto out;
>
> +	*more = 1;
>   	new_sock->sk->sk_allocation = GFP_ATOMIC;
>
>   	ret = o2net_set_nodelay(new_sock);
> @@ -1949,8 +1951,15 @@ out:
>   static void o2net_accept_many(struct work_struct *work)
>   {
>   	struct socket *sock = o2net_listen_sock;
> -	while (o2net_accept_one(sock) == 0)
> +	int	more;
> +	int	err;
> +
> +	for (;;) {
> +		err = o2net_accept_one(sock, &more);
> +		if (!more)
> +			break;
>   		cond_resched();
> +	}
>   }
>
>   static void o2net_listen_data_ready(struct sock *sk, int bytes)
> _
>