On 12 Dec 2018, at 13:02, Trond Myklebust wrote:
> On Wed, 2018-12-12 at 12:47 -0500, Dave Wysochanski wrote:
>> On Wed, 2018-12-12 at 16:56 +0000, Trond Myklebust wrote:
>>> On Wed, 2018-12-12 at 08:51 -0500, Dave Wysochanski wrote:
>>>> Commit 9b30889c548a changed the handling of TCP_CLOSE inside
>>>> xs_tcp_state_change. Prior to this change, the XPRT_CONNECTED
>>>> bit
>>>> was cleared unconditionally inside xprt_disconnect_done, similar
>>>> to the handling of TCP_CLOSE_WAIT. After the change the clearing
>>>> of XPRT_CONNECTED depends on successfully queueing a work based
>>>> xprt_autoclose which depends on XPRT_LOCKED and may not happen.
>>>> This is significant in the case of an unexpected RST from the
>>>> server, as the client will only see xs_tcp_state_change called
>>>> with
>>>> sk_state == TCP_CLOSE. Restore the unconditional clear_bit on
>>>> XPRT_CONNECTED while handling TCP_CLOSE and make it consistent
>>>> with handling TCP_CLOSE_WAIT.
>>>>
>>>> Signed-off-by: Dave Wysochanski <dwysocha@xxxxxxxxxx>
>>>> ---
>>>> net/sunrpc/xprtsock.c | 1 +
>>>> 1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
>>>> index 8a5e823e0b33..b9789036051d 100644
>>>> --- a/net/sunrpc/xprtsock.c
>>>> +++ b/net/sunrpc/xprtsock.c
>>>> @@ -1492,6 +1492,7 @@ static void xs_tcp_state_change(struct sock
>>>> *sk)
>>>> if (sk->sk_err)
>>>> xprt_wake_pending_tasks(xprt, -sk-
>>>>> sk_err);
>>>> /* Trigger the socket release */
>>>> + clear_bit(XPRT_CONNECTED, &xprt->state);
>>>> xs_tcp_force_close(xprt);
>>>> }
>>>> out:
>>>
>>> Hi Dave,
>>>
>>> This isn't needed for 4.20 or newer because call_transmit() will
>>> now
>>> always call xprt_end_transmit(). I suggest that a stable fix do
>>> something similar (perhaps conditional on the error returned by
>>> xprt_transmit()?).
>>>
>>
>> Can you explain the handling in xs_tcp_state_change - why
>> XPRT_CONNECTED would need to remain set longer in the case of
>> handling
>> TCP_CLOSE case rather than TCP_CLOSE_WAIT? It seems like if we get
>> an
>> RST we'll go directly to TCP_CLOSE and why would the XPRT_CONNECTED
>> bit
>> getting cleared need to be delayed in that case?
>>
>> I will look into the approach you mention though at the moment I do
>> not
>> see how it helps because the underlying issue seems to be clearing of
>> the XPRT_CONNECTED bit.
>>
>
> See xprt_clear_locked(). Dropping the XPRT_LOCK will automatically
> trigger autoclose if XPRT_CLOSE_WAIT is set, regardless of whether or
> not there are other tasks waiting for the lock.
It seems to make sense to drop the XPRT_LOCK in call_transmit_status if
XPRT_CLOSE_WAIT is set.. something like:
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 336fd1a19cca..f30bf500888d 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -443,6 +443,11 @@ static inline int xprt_test_and_set_connecting(struct
rpc_xprt *xprt)
return test_and_set_bit(XPRT_CONNECTING, &xprt->state);
}
+static inline int xprt_close_wait(struct rpc_xprt *xprt)
+{
+ return test_bit(XPRT_CLOSE_WAIT, &xprt->state);
+}
+
static inline void xprt_set_bound(struct rpc_xprt *xprt)
{
test_and_set_bit(XPRT_BOUND, &xprt->state);
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 8ea2f5fadd96..1fc812ba9871 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1992,13 +1992,15 @@ call_transmit(struct rpc_task *task)
static void
call_transmit_status(struct rpc_task *task)
{
+ struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
task->tk_action = call_status;
/*
* Common case: success. Force the compiler to put this
- * test first.
+ * test first. Or, if any error and xprt_close_wait,
+ * release the xprt lock so the socket can close.
*/
- if (task->tk_status == 0) {
+ if (task->tk_status == 0 || xprt_close_wait(xprt)) {
xprt_end_transmit(task);
rpc_task_force_reencode(task);
return;
Hmm.. I guess I have to figure out how to get a stable patch submitted that
will never have a mainline commit, since we don't have this problem in the
mainline.
Ben
