SUNRPC: Expand the svc_alloc_arg_err tracepoint

Record not only the number of pages requested, but the number of
pages that were actually allocated, to get a measure of progress
(or lack thereof).
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/trace/events/sunrpc.h

@@ -1989,20 +1989,24 @@ TRACE_EVENT(svc_wake_up,
 
 TRACE_EVENT(svc_alloc_arg_err,
 	TP_PROTO(
-		unsigned int pages
+		unsigned int requested,
+		unsigned int allocated
 	),
 
-	TP_ARGS(pages),
+	TP_ARGS(requested, allocated),
 
 	TP_STRUCT__entry(
-		__field(unsigned int, pages)
+		__field(unsigned int, requested)
+		__field(unsigned int, allocated)
 	),
 
 	TP_fast_assign(
-		__entry->pages = pages;
+		__entry->requested = requested;
+		__entry->allocated = allocated;
 	),
 
-	TP_printk("pages=%u", __entry->pages)
+	TP_printk("requested=%u allocated=%u",
+		__entry->requested, __entry->allocated)
 );
 
 DECLARE_EVENT_CLASS(svc_deferred_event,

net/sunrpc/svc_xprt.c

@@ -691,7 +691,7 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
 			set_current_state(TASK_RUNNING);
 			return -EINTR;
 		}
-		trace_svc_alloc_arg_err(pages);
+		trace_svc_alloc_arg_err(pages, ret);
 		memalloc_retry_wait(GFP_KERNEL);
 	}
 	rqstp->rq_page_end = &rqstp->rq_pages[pages];