[PATCH 1/3] xprtrdma: Recycle MRs after disconnect

[Chuck Lever <chuck.lever@xxxxxxxxxx>]

The optimization done in "xprtrdma: Simplify rpcrdma_mr_pop" was a
bit too optimistic. MRs left over after a reconnect still need to
be recycled, not added back to the free list, since they could be
in flight or actually fully registered.

Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 net/sunrpc/xprtrdma/frwr_ops.c  |   35 +++++++++++++++++++++++++++--------
 net/sunrpc/xprtrdma/rpc_rdma.c  |    2 +-
 net/sunrpc/xprtrdma/xprt_rdma.h |    1 +
 3 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index 368cdf3..30065a2 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -88,15 +88,8 @@ void frwr_release_mr(struct rpcrdma_mr *mr)
 	kfree(mr);
 }
 
-/* MRs are dynamically allocated, so simply clean up and release the MR.
- * A replacement MR will subsequently be allocated on demand.
- */
-static void
-frwr_mr_recycle_worker(struct work_struct *work)
+static void frwr_mr_recycle(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr *mr)
 {
-	struct rpcrdma_mr *mr = container_of(work, struct rpcrdma_mr, mr_recycle);
-	struct rpcrdma_xprt *r_xprt = mr->mr_xprt;
-
 	trace_xprtrdma_mr_recycle(mr);
 
 	if (mr->mr_dir != DMA_NONE) {
@@ -114,6 +107,32 @@ void frwr_release_mr(struct rpcrdma_mr *mr)
 	frwr_release_mr(mr);
 }
 
+/* MRs are dynamically allocated, so simply clean up and release the MR.
+ * A replacement MR will subsequently be allocated on demand.
+ */
+static void
+frwr_mr_recycle_worker(struct work_struct *work)
+{
+	struct rpcrdma_mr *mr = container_of(work, struct rpcrdma_mr,
+					     mr_recycle);
+
+	frwr_mr_recycle(mr->mr_xprt, mr);
+}
+
+/* frwr_recycle - Discard MRs
+ * @req: request to reset
+ *
+ * Used after a reconnect. These MRs could be in flight, we can't
+ * tell. Safe thing to do is release them.
+ */
+void frwr_recycle(struct rpcrdma_req *req)
+{
+	struct rpcrdma_mr *mr;
+
+	while ((mr = rpcrdma_mr_pop(&req->rl_registered)))
+		frwr_mr_recycle(mr->mr_xprt, mr);
+}
+
 /* frwr_reset - Place MRs back on the free list
  * @req: request to reset
  *
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 67e1684..19dd29a 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -867,7 +867,7 @@ static bool rpcrdma_prepare_msg_sges(struct rpcrdma_xprt *r_xprt,
 	 * chunks. Very likely the connection has been replaced,
 	 * so these registrations are invalid and unusable.
 	 */
-	frwr_reset(req);
+	frwr_recycle(req);
 
 	/* This implementation supports the following combinations
 	 * of chunk lists in one RPC-over-RDMA Call message:
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index bd1befa..65e6b0e 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -542,6 +542,7 @@ static inline bool rpcrdma_regbuf_dma_map(struct rpcrdma_xprt *r_xprt,
 /* Memory registration calls xprtrdma/frwr_ops.c
  */
 bool frwr_is_supported(struct ib_device *device);
+void frwr_recycle(struct rpcrdma_req *req);
 void frwr_reset(struct rpcrdma_req *req);
 int frwr_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep);
 int frwr_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mr *mr);