xprtrdma: Replace send and receive arrays

The rb_send_bufs and rb_recv_bufs arrays are used to implement a
pair of stacks for keeping track of free rpcrdma_req and rpcrdma_rep
structs. Replace those arrays with free lists.

To allow more than 512 RPCs in-flight at once, each of these arrays
would be larger than a page (assuming 8-byte addresses and 4KB
pages). Allowing up to 64K in-flight RPCs (as TCP now does), each
buffer array would have to be 128 pages. That's an order-6
allocation. (Not that we're going there.)

A list is easier to expand dynamically. Instead of allocating a
larger array of pointers and copying the existing pointers to the
new array, simply append more buffers to each list.

This also makes it simpler to manage receive buffers that might
catch backwards-direction calls, or to post receive buffers in
bulk to amortize the overhead of ib_post_recv.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Devesh Sharma <devesh.sharma@avagotech.com>
Tested-By: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index a13508bbe4c4..e6a358fd1f1d 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -252,6 +252,7 @@ struct rpcrdma_mr_seg {		/* chunk descriptors */
 #define RPCRDMA_MAX_IOVS	(2)
 
 struct rpcrdma_req {
+	struct list_head	rl_free;
 	unsigned int		rl_niovs;
 	unsigned int		rl_nchunks;
 	unsigned int		rl_connect_cookie;
@@ -285,12 +286,10 @@ struct rpcrdma_buffer {
 	struct list_head	rb_all;
 	char			*rb_pool;
 
-	spinlock_t		rb_lock;	/* protect buf arrays */
+	spinlock_t		rb_lock;	/* protect buf lists */
+	struct list_head	rb_send_bufs;
+	struct list_head	rb_recv_bufs;
 	u32			rb_max_requests;
-	int			rb_send_index;
-	int			rb_recv_index;
-	struct rpcrdma_req	**rb_send_bufs;
-	struct rpcrdma_rep	**rb_recv_bufs;
 };
 #define rdmab_to_ia(b) (&container_of((b), struct rpcrdma_xprt, rx_buf)->rx_ia)