xprtrdma: Chunk list encoders no longer share one rl_segments array

Currently, all three chunk list encoders each use a portion of the
one rl_segments array in rpcrdma_req. This is because the MWs for
each chunk list were preserved in rl_segments so that ro_unmap could
find and invalidate them after the RPC was complete.

However, now that MWs are placed on a per-req linked list as they
are registered, there is no longer any information in rpcrdma_mr_seg
that is shared between ro_map and ro_unmap_{sync,safe}, and thus
nothing in rl_segments needs to be preserved after
rpcrdma_marshal_req is complete.

Thus the rl_segments array can be used now just for the needs of
each rpcrdma_convert_iovs call. Once each chunk list is encoded, the
next chunk list encoder is free to re-use all of rl_segments.

This means all three chunk lists in one RPC request can now each
encode a full size data payload with no increase in the size of
rl_segments.

This is a key requirement for Kerberos support, since both the Call
and Reply for a single RPC transaction are conveyed via Long
messages (RDMA Read/Write). Both can be large.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 16 insertions, 20 deletions

diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index f5d05110de9f..670fad57153a 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -171,23 +171,14 @@ rdmab_to_msg(struct rpcrdma_regbuf *rb)
  *   o recv buffer (posted to provider)
  *   o ib_sge (also donated to provider)
  *   o status of reply (length, success or not)
- *   o bookkeeping state to get run by tasklet (list, etc)
+ *   o bookkeeping state to get run by reply handler (list, etc)
  *
- * These are allocated during initialization, per-transport instance;
- * however, the tasklet execution list itself is global, as it should
- * always be pretty short.
+ * These are allocated during initialization, per-transport instance.
  *
  * N of these are associated with a transport instance, and stored in
  * struct rpcrdma_buffer. N is the max number of outstanding requests.
  */
 
-#define RPCRDMA_MAX_DATA_SEGS	((1 * 1024 * 1024) / PAGE_SIZE)
-
-/* data segments + head/tail for Call + head/tail for Reply */
-#define RPCRDMA_MAX_SEGS 	(RPCRDMA_MAX_DATA_SEGS + 4)
-
-struct rpcrdma_buffer;
-
 struct rpcrdma_rep {
 	struct ib_cqe		rr_cqe;
 	unsigned int		rr_len;
@@ -267,13 +258,18 @@ struct rpcrdma_mw {
  * of iovs for send operations. The reason is that the iovs passed to
  * ib_post_{send,recv} must not be modified until the work request
  * completes.
- *
- * NOTES:
- *   o RPCRDMA_MAX_SEGS is the max number of addressible chunk elements we
- *     marshal. The number needed varies depending on the iov lists that
- *     are passed to us and the memory registration mode we are in.
  */
 
+/* Maximum number of page-sized "segments" per chunk list to be
+ * registered or invalidated. Must handle a Reply chunk:
+ */
+enum {
+	RPCRDMA_MAX_IOV_SEGS	= 3,
+	RPCRDMA_MAX_DATA_SEGS	= ((1 * 1024 * 1024) / PAGE_SIZE) + 1,
+	RPCRDMA_MAX_SEGS	= RPCRDMA_MAX_DATA_SEGS +
+				  RPCRDMA_MAX_IOV_SEGS,
+};
+
 struct rpcrdma_mr_seg {		/* chunk descriptors */
 	u32		mr_len;		/* length of chunk or segment */
 	struct page	*mr_page;	/* owning page, if any */
@@ -282,10 +278,10 @@ struct rpcrdma_mr_seg {		/* chunk descriptors */
 
 #define RPCRDMA_MAX_IOVS	(2)
 
+struct rpcrdma_buffer;
 struct rpcrdma_req {
 	struct list_head	rl_free;
 	unsigned int		rl_niovs;
-	unsigned int		rl_nchunks;
 	unsigned int		rl_connect_cookie;
 	struct rpc_task		*rl_task;
 	struct rpcrdma_buffer	*rl_buffer;
@@ -293,13 +289,13 @@ struct rpcrdma_req {
 	struct ib_sge		rl_send_iov[RPCRDMA_MAX_IOVS];
 	struct rpcrdma_regbuf	*rl_rdmabuf;
 	struct rpcrdma_regbuf	*rl_sendbuf;
-	struct list_head	rl_registered;	/* registered segments */
-	struct rpcrdma_mr_seg	rl_segments[RPCRDMA_MAX_SEGS];
-	struct rpcrdma_mr_seg	*rl_nextseg;
 
 	struct ib_cqe		rl_cqe;
 	struct list_head	rl_all;
 	bool			rl_backchannel;
+
+	struct list_head	rl_registered;	/* registered segments */
+	struct rpcrdma_mr_seg	rl_segments[RPCRDMA_MAX_SEGS];
 };
 
 static inline struct rpcrdma_req *