xprtrdma: Shrink send SGEs array

We no longer need to accommodate an xdr_buf whose pages start at an
offset and cross extra page boundaries. If there are more partial or
whole pages to send than there are available SGEs, the marshaling
logic is now smart enough to use a Read chunk instead of failing.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 3d7e9c9bad1f..852dd0a750a5 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -305,16 +305,19 @@ struct rpcrdma_mr_seg {		/* chunk descriptors */
 	char		*mr_offset;	/* kva if no page, else offset */
 };
 
-/* Reserve enough Send SGEs to send a maximum size inline request:
+/* The Send SGE array is provisioned to send a maximum size
+ * inline request:
  * - RPC-over-RDMA header
  * - xdr_buf head iovec
- * - RPCRDMA_MAX_INLINE bytes, possibly unaligned, in pages
+ * - RPCRDMA_MAX_INLINE bytes, in pages
  * - xdr_buf tail iovec
+ *
+ * The actual number of array elements consumed by each RPC
+ * depends on the device's max_sge limit.
  */
 enum {
 	RPCRDMA_MIN_SEND_SGES = 3,
-	RPCRDMA_MAX_SEND_PAGES = PAGE_SIZE + RPCRDMA_MAX_INLINE - 1,
-	RPCRDMA_MAX_PAGE_SGES = (RPCRDMA_MAX_SEND_PAGES >> PAGE_SHIFT) + 1,
+	RPCRDMA_MAX_PAGE_SGES = RPCRDMA_MAX_INLINE >> PAGE_SHIFT,
 	RPCRDMA_MAX_SEND_SGES = 1 + 1 + RPCRDMA_MAX_PAGE_SGES + 1,
 };