Re: [PATCH] Revert "SUNRPC: xs_sock_mark_closed() does not need to trigger socket autoclose"

[NeilBrown <neilb@suse.com>]

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On Thu, Aug 04 2016, Trond Myklebust wrote:

>> On Aug 3, 2016, at 19:33, NeilBrown <neilb@suse.com> wrote:
>> 
>> 
>> This reverts commit 4b0ab51db32eba0f48b7618254742f143364a28d.
>> 
>> This change causes 'rpc.nfsd' to hang for long time if rpcbind is not
>> available.
>> If
>>   --no-nfs-version 2 --no-nfs-version 3
>> is given, the delay is about 6.5 minutes.  When trying to register
>> all versions, the delay is over half an hour.
>> Before this commit, and after reverting it, nfsd fails (when v3 is
>> requested) or succeeds (when only v4 is requested) immediately.
>> 
>> Signed-off-by: NeilBrown <neilb@suse.com>
>> ---
>> net/sunrpc/xprtsock.c | 1 +
>> 1 file changed, 1 insertion(+)
>> 
>> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
>> index 111767ab124a..2a938055e95b 100644
>> --- a/net/sunrpc/xprtsock.c
>> +++ b/net/sunrpc/xprtsock.c
>> @@ -795,6 +795,7 @@ static void xs_sock_mark_closed(struct rpc_xprt *xprt)
>> 	xs_sock_reset_connection_flags(xprt);
>> 	/* Mark transport as closed and wake up all pending tasks */
>> 	xprt_disconnect_done(xprt);
>> +	xprt_force_disconnect(xprt);
>> }
>> 
>
> If there is an outstanding request, then _that_ is supposed to redrive the connection. Why is the xprt_disconnect_done() not functioning as per the comment above it?

No idea, sorry.  I haven't tried to follow though exactly what is
happening.
The symptom is trivial to reproduce:
  rpc.nfsd 0
  killall rpcbind
  rpc.nfsd 8

This will either complete immediately with kernel log messages, or block
for a long time.
I might try to figure out what is happening, but I suspect there are
others who know this code a lot better than I do.

NeilBrown

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