From: Chuck Lever chuck.lever@oracle.com
commit 773f91b2cf3f52df0d7508fdbf60f37567cdaee4 upstream.
Trond Myklebust reports an NFSD crash in svc_rdma_sendto(). Further investigation shows that the crash occurred while NFSD was handling a deferred request.
This patch addresses two inter-related issues that prevent request deferral from working correctly for RPC/RDMA requests:
1. Prevent the crash by ensuring that the original svc_rqst::rq_xprt_ctxt value is available when the request is revisited. Otherwise svc_rdma_sendto() does not have a Receive context available with which to construct its reply.
2. Possibly since before commit 71641d99ce03 ("svcrdma: Properly compute .len and .buflen for received RPC Calls"), svc_rdma_recvfrom() did not include the transport header in the returned xdr_buf. There should have been no need for svc_defer() and friends to save and restore that header, as of that commit. This issue is addressed in a backport-friendly way by simply having svc_rdma_recvfrom() set rq_xprt_hlen to zero unconditionally, just as svc_tcp_recvfrom() does. This enables svc_deferred_recv() to correctly reconstruct an RPC message received via RPC/RDMA.
Reported-by: Trond Myklebust trondmy@hammerspace.com Link: https://lore.kernel.org/linux-nfs/82662b7190f26fb304eb0ab1bb04279072439d4e.c... Signed-off-by: Chuck Lever chuck.lever@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/sunrpc/svc.h | 1 + net/sunrpc/svc_xprt.c | 3 +++ net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 2 +- 3 files changed, 5 insertions(+), 1 deletion(-)
--- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -384,6 +384,7 @@ struct svc_deferred_req { size_t addrlen; struct sockaddr_storage daddr; /* where reply must come from */ size_t daddrlen; + void *xprt_ctxt; struct cache_deferred_req handle; size_t xprt_hlen; int argslen; --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -1213,6 +1213,8 @@ static struct cache_deferred_req *svc_de dr->daddr = rqstp->rq_daddr; dr->argslen = rqstp->rq_arg.len >> 2; dr->xprt_hlen = rqstp->rq_xprt_hlen; + dr->xprt_ctxt = rqstp->rq_xprt_ctxt; + rqstp->rq_xprt_ctxt = NULL;
/* back up head to the start of the buffer and copy */ skip = rqstp->rq_arg.len - rqstp->rq_arg.head[0].iov_len; @@ -1251,6 +1253,7 @@ static noinline int svc_deferred_recv(st rqstp->rq_xprt_hlen = dr->xprt_hlen; rqstp->rq_daddr = dr->daddr; rqstp->rq_respages = rqstp->rq_pages; + rqstp->rq_xprt_ctxt = dr->xprt_ctxt; svc_xprt_received(rqstp->rq_xprt); return (dr->argslen<<2) - dr->xprt_hlen; } --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -826,7 +826,7 @@ int svc_rdma_recvfrom(struct svc_rqst *r goto out_err; if (ret == 0) goto out_drop; - rqstp->rq_xprt_hlen = ret; + rqstp->rq_xprt_hlen = 0;
if (svc_rdma_is_reverse_direction_reply(xprt, ctxt)) goto out_backchannel;