Fix a case where a request frame can be composed that requires 2 or more

SGList elements, but there's only enough space in the request frame for
either 1 element or a chain frame pointer.  Previously, the code would
hit the wrong case, add the SGList element, but then fail to add the
chain frame due to lack of space.  Re-arrange the code to catch this case
earlier and handle it.

Sponsored by:	Netflix

1 files changed, 11 insertions, 11 deletions

diff --git a/sys/dev/mps/mps.c b/sys/dev/mps/mps.c
index 766b77134fe3..b39fa32f7ed0 100644
--- a/sys/dev/mps/mps.c
+++ b/sys/dev/mps/mps.c
@@ -2609,6 +2609,17 @@ mps_push_sge(struct mps_command *cm, void *sgep, size_t len, int segsleft)
 	if (cm->cm_sglsize < MPS_SGC_SIZE)
 		panic("MPS: Need SGE Error Code\n");
 
+	if (segsleft >= 1 && cm->cm_sglsize < len + MPS_SGC_SIZE) {
+		/*
+		 * 1 or more segment, enough room for only a chain.
+		 * Hope the previous element wasn't a Simple entry
+		 * that needed to be marked with
+		 * MPI2_SGE_FLAGS_LAST_ELEMENT.  Case (4).
+		 */
+		if ((error = mps_add_chain(cm)) != 0)
+			return (error);
+	}
+
 	if (segsleft >= 2 &&
 	    cm->cm_sglsize < len + MPS_SGC_SIZE + MPS_SGE64_SIZE) {
 		/*
@@ -2633,17 +2644,6 @@ mps_push_sge(struct mps_command *cm, void *sgep, size_t len, int segsleft)
 		return (mps_add_chain(cm));
 	}
 
-	if (segsleft >= 1 && cm->cm_sglsize < len + MPS_SGC_SIZE) {
-		/*
-		 * 1 or more segment, enough room for only a chain.
-		 * Hope the previous element wasn't a Simple entry
-		 * that needed to be marked with
-		 * MPI2_SGE_FLAGS_LAST_ELEMENT.  Case (4).
-		 */
-		if ((error = mps_add_chain(cm)) != 0)
-			return (error);
-	}
-
 #ifdef INVARIANTS
 	/* Case 1: 1 more segment, enough room for it. */
 	if (segsleft == 1 && cm->cm_sglsize < len)