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linux/net/sunrpc/xprtrdma
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Chuck Lever 05c974669e xprtrdma: Fix receive buffer accounting 
An RPC can terminate before its reply arrives, if a credential
problem or a soft timeout occurs. After this happens, xprtrdma
reports it is out of Receive buffers.

A Receive buffer is posted before each RPC is sent, and returned to
the buffer pool when a reply is received. If no reply is received
for an RPC, that Receive buffer remains posted. But xprtrdma tries
to post another when the next RPC is sent.

If this happens a few dozen times, there are no receive buffers left
to be posted at send time. I don't see a way for a transport
connection to recover at that point, and it will spit warnings and
unnecessarily delay RPCs on occasion for its remaining lifetime.

Commit 1e465fd4ff ("xprtrdma: Replace send and receive arrays")
removed a little bit of logic to detect this case and not provide
a Receive buffer so no more buffers are posted, and then transport
operation continues correctly. We didn't understand what that logic
did, and it wasn't commented, so it was removed as part of the
overhaul to support backchannel requests.

Restore it, but be wary of the need to keep extra Receives posted
to deal with backchannel requests.

Fixes: 1e465fd4ff ("xprtrdma: Replace send and receive arrays")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2016-09-06 15:59:35 -04:00
..
backchannel.c sunrpc: Advertise maximum backchannel payload size 2016-05-17 15:47:57 -04:00
fmr_ops.c xprtrdma: Place registered MWs on a per-req list 2016-07-11 15:50:43 -04:00
frwr_ops.c xprtrdma: Place registered MWs on a per-req list 2016-07-11 15:50:43 -04:00
Makefile xprtrdma: Remove ALLPHYSICAL memory registration mode 2016-07-11 15:50:43 -04:00
module.c rpcrdma: Merge svcrdma and xprtrdma modules into one 2015-06-04 16:56:02 -04:00
rpc_rdma.c xprtrdma: No direct data placement with krb5i and krb5p 2016-07-11 15:50:43 -04:00
svc_rdma_backchannel.c svcrdma: Use new CQ API for RPC-over-RDMA server send CQs 2016-03-01 13:06:43 -08:00
svc_rdma_marshal.c svcrdma: Generalize svc_rdma_xdr_decode_req() 2016-05-13 15:53:06 -04:00
svc_rdma_recvfrom.c A very quiet cycle for nfsd, mainly just an RDMA update from Chuck Lever. 2016-05-24 14:39:20 -07:00
svc_rdma_sendto.c svcrdma: svc_rdma_put_context() is invoked twice in Send error path 2016-05-13 15:53:05 -04:00
svc_rdma_transport.c svcrdma: Drain QP before freeing svcrdma_xprt 2016-05-13 15:53:06 -04:00
svc_rdma.c svcrdma: Define maximum number of backchannel requests 2016-01-19 15:30:48 -05:00
transport.c xprtrdma: Place registered MWs on a per-req list 2016-07-11 15:50:43 -04:00
verbs.c xprtrdma: Fix receive buffer accounting 2016-09-06 15:59:35 -04:00
xprt_rdma.h xprtrdma: Fix receive buffer accounting 2016-09-06 15:59:35 -04:00