xprtrdma: Replace rpcrdma_mr_seg with xdr_buf cursor

The FRWR registration path converts data through three
representations: xdr_buf -> rpcrdma_mr_seg[] -> scatterlist[]
-> ib_map_mr_sg(). The rpcrdma_mr_seg intermediate is a relic
of when multiple registration strategies existed (FMR, physical,
FRWR). Only FRWR remains, so this indirection and the 6240-byte
rl_segments[260] array embedded in each rpcrdma_req serve no
purpose.

Introduce struct rpcrdma_xdr_cursor to track position within
an xdr_buf during iterative MR registration. Rewrite frwr_map to
populate scatterlist entries directly from the xdr_buf regions
(head kvec, page list, tail kvec). The boundary logic for
non-SG_GAPS devices is simpler because the xdr_buf structure
guarantees that page-region entries after the first start at
offset 0, and that head/tail kvecs are separate regions that
naturally break at MR boundaries.

Fix a pre-existing bug in rpcrdma_encode_write_list where the
write-pad statistics accumulator added mr->mr_length from the last
data MR rather than the write-pad MR. The refactored code uses
ep->re_write_pad_mr->mr_length.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

1 files changed, 14 insertions, 14 deletions

diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
index e6a72646c507..b79913048e1a 100644
--- a/include/trace/events/rpcrdma.h
+++ b/include/trace/events/rpcrdma.h
@@ -392,10 +392,10 @@ DECLARE_EVENT_CLASS(xprtrdma_rdch_event,
 		const struct rpc_task *task,
 		unsigned int pos,
 		struct rpcrdma_mr *mr,
-		int nsegs
+		bool is_last
 	),
 
-	TP_ARGS(task, pos, mr, nsegs),
+	TP_ARGS(task, pos, mr, is_last),
 
 	TP_STRUCT__entry(
 		__field(unsigned int, task_id)
@@ -405,7 +405,7 @@ DECLARE_EVENT_CLASS(xprtrdma_rdch_event,
 		__field(u32, handle)
 		__field(u32, length)
 		__field(u64, offset)
-		__field(int, nsegs)
+		__field(bool, is_last)
 	),
 
 	TP_fast_assign(
@@ -416,7 +416,7 @@ DECLARE_EVENT_CLASS(xprtrdma_rdch_event,
 		__entry->handle = mr->mr_handle;
 		__entry->length = mr->mr_length;
 		__entry->offset = mr->mr_offset;
-		__entry->nsegs = nsegs;
+		__entry->is_last = is_last;
 	),
 
 	TP_printk(SUNRPC_TRACE_TASK_SPECIFIER
@@ -424,7 +424,7 @@ DECLARE_EVENT_CLASS(xprtrdma_rdch_event,
 		__entry->task_id, __entry->client_id,
 		__entry->pos, __entry->length,
 		(unsigned long long)__entry->offset, __entry->handle,
-		__entry->nents < __entry->nsegs ? "more" : "last"
+		__entry->is_last ? "last" : "more"
 	)
 );
 
@@ -434,18 +434,18 @@ DECLARE_EVENT_CLASS(xprtrdma_rdch_event,
 					const struct rpc_task *task,	\
 					unsigned int pos,		\
 					struct rpcrdma_mr *mr,		\
-					int nsegs			\
+					bool is_last			\
 				),					\
-				TP_ARGS(task, pos, mr, nsegs))
+				TP_ARGS(task, pos, mr, is_last))
 
 DECLARE_EVENT_CLASS(xprtrdma_wrch_event,
 	TP_PROTO(
 		const struct rpc_task *task,
 		struct rpcrdma_mr *mr,
-		int nsegs
+		bool is_last
 	),
 
-	TP_ARGS(task, mr, nsegs),
+	TP_ARGS(task, mr, is_last),
 
 	TP_STRUCT__entry(
 		__field(unsigned int, task_id)
@@ -454,7 +454,7 @@ DECLARE_EVENT_CLASS(xprtrdma_wrch_event,
 		__field(u32, handle)
 		__field(u32, length)
 		__field(u64, offset)
-		__field(int, nsegs)
+		__field(bool, is_last)
 	),
 
 	TP_fast_assign(
@@ -464,7 +464,7 @@ DECLARE_EVENT_CLASS(xprtrdma_wrch_event,
 		__entry->handle = mr->mr_handle;
 		__entry->length = mr->mr_length;
 		__entry->offset = mr->mr_offset;
-		__entry->nsegs = nsegs;
+		__entry->is_last = is_last;
 	),
 
 	TP_printk(SUNRPC_TRACE_TASK_SPECIFIER
@@ -472,7 +472,7 @@ DECLARE_EVENT_CLASS(xprtrdma_wrch_event,
 		__entry->task_id, __entry->client_id,
 		__entry->length, (unsigned long long)__entry->offset,
 		__entry->handle,
-		__entry->nents < __entry->nsegs ? "more" : "last"
+		__entry->is_last ? "last" : "more"
 	)
 );
 
@@ -481,9 +481,9 @@ DECLARE_EVENT_CLASS(xprtrdma_wrch_event,
 				TP_PROTO(				\
 					const struct rpc_task *task,	\
 					struct rpcrdma_mr *mr,		\
-					int nsegs			\
+					bool is_last			\
 				),					\
-				TP_ARGS(task, mr, nsegs))
+				TP_ARGS(task, mr, is_last))
 
 TRACE_DEFINE_ENUM(DMA_BIDIRECTIONAL);
 TRACE_DEFINE_ENUM(DMA_TO_DEVICE);